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# Logical definition with equalily and Law of Identity in Suppes' “Introduction to Logic”
Patrick Suppes' "Introduction to Logic" provides rules for formal definitions in chapter 8. The rules below are specified for a new operation symbol with equality:
An equivalence $$D$$ introducing a new n-place operation symbol $$O$$ is a proper definition in a theory if and only if $$D$$ is of the form:
$$O(v_1, ..., v_n) = w \leftrightarrow S$$
and the following restrictions are satisfied:
(i) $$v_1, ..., v_n, w$$ are distinct variables.
(ii) $$S$$ has no free variables other than $$v_1, ..., v_n, w$$.
(iii) $$S$$ is a formula in which the only non-logical constants are primitive symbols and previously defined symbols of the theory.
(iv) The formula $$\exists !w[S]$$ is derivable from the axioms and preceding definitions of the theory.
There's also a prior mention of the Law of Identity:
If x is anything whatsoever, then $$x=x$$.
Now let's suppose that you have the following definition:
$$\forall f,x,y[f_x = y \iff f \text{ is a function } \land \langle x,y \rangle \in f]$$
Let's also assume that you have previously defined functions and ordered pairs such that you may prove $$\exists !y[S]$$ with extentionality, so it follows rule (iv).
Here's the problem: Within the bounds of this ruleset, it seems like one can use the Law of Identity with any variable, say $$A$$, to claim that $$A_x=A_x$$ and use that to claim that $$A \text{ is a function } \land \langle x,A_x \rangle \in A$$, and so, that $$A$$ is a function, even though we know nothing about it. That logic can be used with any variable, be it a normal relation, a simple set, or even a urelement, so this deduction must be wrong.
At first, I thought I was breaking rule (iii), as the statement "$$A \text{ is a function } \land \langle x,A_x \rangle \in A$$" has a not previously defined symbol in it, $$A_x$$, which is defined in the statement itself, so it would not be valid.
It is unique by extentionality. It seems a clear consequence from it that $$\mset{a} = \mset{b} \lif a = b$$, but the only way I see to prove it is by using $$\mset{a} = \mset{b}$$ to get $$\forall x[x \in \mset{b} \liff x = a]$$, which would be disallowed if my interpretation was correct, so I don't think that is the answer.
My second instinct was that rule (i) is being broken, that $$f_x = f_x$$ doesn't count as being distinct variables. However, from the definition above it also seems that $$a \in \mset{a}$$ should follow. The only way I see to prove this is to use $$\mset{a} = \mset{a}$$ with the definition, which would be disallowed if this was the case, so I don't feel that's the solution either.
So my question is: What is the actual culprit of the fallacy?
Edit: After extended discussion, I'm adding some information to hopefully clarify what this question is and is not about.
This is not about set theory. My problem is with about the formal language of first-order logic provided by the book. To avoid the focus on set theory, I'll provide a second example. Let's suppose we have the following statements:
$$\forall a,b,x,y[\text{isSingleChild}(x) \land \text{parentsOf}(a,b,x) \land \text{parentsOf}(a,b,y) \Rightarrow x = y] \\ \forall a,b,x[\text{son}\{a,b\} = x \iff \text{isAdult}(a) \land \text{isAdult}(b) \land \text{parentsOf}(a,b,x) \land \text{isSingleChild}(x)]$$
The first statement guarantees that $$x$$ is unique in the definition of $$\text{son}$$.
The definition of $$\text{son}\{a,b\}$$ seems to follow all of the rules provided. It is not intended to state that any variable follows any specific predicate, but simply stating their logical relationship. However, if you use it together with the Law of Identity, you may derive:
So from that definition, you may deduce that everyone is an adult. Note what I am not saying. I'm not saying that this argument is sound, nor defending it, I'm saying that the ruleset given in the book permits it (It probably doesn't, but I don't see any rule of logical deduction being broken). I know the argument is illogical, but the formal rules are being followed. My question is not about the soundness of the argument, but the soundness of the system provided in the book.
Also note that the assertion is not about set theory, nor "family theory", it is about the logic itself. My assertion is that (apparently) within the formal system given, any statement of the following form applies:
$$\forall a,b,x[\text{entityFrom}\{a,b\} = x \iff \text{hasSomeProperty}(a) \land \text{uniqueRelation}(a,b,x)] \vdash \forall a[\text{hasSomeProperty}(a)]$$
I understand that the definition doesn't entail the conclusion. Nonetheless, within the system, the conclusion seems to be deducible from it.
There are only three options. Either the formal system provided in not sound, the definition actually entails the conclusion, or I'm missing/misinterpreting some rule on the Law of Identity/Rules for Definition/Rules for Quantifiers.
The book and is more than 50 years old, any possible oversights in the system would have been noticed by this point (it also was written by Suppes, so I doubt there is any), thus I'm sure it's not the first one. The definitions also seem well formed and feel like they shouldn't lead directly to the conclusion, so it's probably not the second one as well. Leading to the conclusion that I am probably missing or misinterpreting some proviso/rule that would make that argument not valid. The question is, which one?
What will not answer the question:
• "In set theory, functions have a specific domain and need to have [some set properties], so it is not possible for all variables to be functions."
• "Your definition of parenthood does not describe the idea of parents correctly, as it does not imply that all children have parents and [some parenthood properties], so the definitions are not correct descriptions."
The solution cannot be about the unsoundness of the argument in one specific theory, that will not get to the root of the problem. A specific context may be used as an example, but the solution has to be on the level of the formal language.
• "The ruleset given by the book is actually incomplete, because a definition with equality containing [some syntatic property] may lead to a fallacy. However, you may avoid it by adding a new rule that requires your definition to have [new definition contraint]"
• "Your definitions logically entail the conclusion. Think about it, if your definition is [this], then [explanation of why the definition should logically lead to the conclusion], so the argument and conclusion are valid. I doubt that's what you intended to conclude with your definition though. I think what you actually mean is [well behaved definition]." $$^{\dagger}$$
• "You've misinterpreted rule [n], perhaps you think it means [interpretation] when it actually says [different interpretation]. If you take that into account, line [x] of your argument is not valid."
• "You are forgetting that you cannot substitute for defined terms like you do variables. You can only substitute for a defined term if [some syntatic condition] applies, so step $$3$$ of your deduction is invalid."
• "The Law of Identity does not require only uniqueness, but also [some variable property], so you may not use it as in line $$5$$, since the variable in your definition doesn't follow this constraint."
Your answer need not be any of the above. I'm just presenting the types of answers I feel will most likely be useful: Answers that focus on the formal language.
Thank you for reading till the end, and I hope this makes clear enough the problem I'm wanting to solve.
$$\dagger$$ As pointed out by Mauro ALLEGRANZA, this case specially makes sense. As he put it:
Think about it: is there some axioms in your theory saying that not every object is an Adult?
Which I agree with. However, there's one problem: The ruleset shouldn't allow this.
Earlier in the same chapter, before the rules are established, their objective is laid out. The "Criteria for proper definitions". The objective is to separate an axiom from a definition. The first one (Criterion of Eliminability) is not important for this discusion, but the second is.
The Criterion of Non-Creativity states that a definition $$S$$ is non-creative if and only if:
There is no formula $$T$$ in which the new symbol does not occur such that $$S \rightarrow T$$ is derivable from the axioms and preceding definitions of the theory but $$T$$ is not so derivable.
The objective of the ruleset is to guarantee that our definitions follow both of these criteria. As stated in page 155: "[...] we turn to the task of stating rules of definition which will guarantee satisfacition of the two criteria of eliminability and non-creativity"
In my parenthood example, we have the first statement as an axiom, and the second as a definition. However, within that theory, the statement $$\forall a [\text{isAdult}(a)]$$ does not contain the new symbol and is derivable from the new definition, but not from the axioms alone, which would make the definition creative.
So in that case, my question then becomes: How come the definition is creative, when the ruleset is supposed to guarantee non-creativity?
• The identity law $x=x$ holds for individual variables and not for formulas. If $A$ is a predicate symbol, $A(x)$ is an atomic formula. – Mauro ALLEGRANZA Jan 4 at 16:59
• $A$ is a variable in this context, not a predicate, and $A(x)$ is an individual (as shown by the uniqueness of $y$). If we can't use the identity law with the individual $A(x)$, that means we can't use it with $\{a\}$. In that case, how one may prove that $a \in \{a\}$ without $\{a\}=\{a\}$? – Luiz Martins Jan 4 at 17:19
• $A$ ia a variable and $A(x)$ an individual? Not possible in predicate logic. Either $A$ is predicate symbol (unary), in which case $A(x)$ is a formula "x is a Man" or $A$ is an individual constant (Aristotle) ir $A$ is a function symbol, in which case $A(x)$ is aterm: a name for an object ("the father of Aristotle"). – Mauro ALLEGRANZA Jan 4 at 17:38
• Indeed. I just used standard function notation, as it is well known, but that would make the language ambiguous. I've changed $f(x)$ to $f_x$, to make clear that it's not a predicate, but a variable. – Luiz Martins Jan 4 at 17:47
The ruleset given by the book is not incomplete. The example derivation you give holds up to scrutiny as well. You get (seemingly) paradoxical conclusions because restriction (iv) does not actually hold in any of your examples.
In your first example, the formula $$S$$ denotes the following: "$$v_2 \text{ is a function } \wedge \langle v_1,w \rangle \in v_2$$". So restriction (iv) is not satisfied unless the following is a theorem of the theory under consideration:
$$\exists! w. v_2 \text{ is a function } \wedge \langle v_1,w \rangle \in v_2$$
which, since $$v_1,v_2$$ are distinct free variables, holds precisely if
$$\forall v_1. \forall v_2. \exists! w. v_2 \text{ is a function } \wedge \langle v_1,w \rangle \in v_2$$
is a theorem of your theory as well. Needless to say, this latter statement is very much not a theorem of any reasonable set theory. In particular it would imply "$$\forall v. v \text{ is a function }$$" by itself.
In your second example, the formula $$S$$ denotes the following: "$$\text{isAdult}(v_1) \wedge \text{isAdult}(v_2) \wedge \text{parentsOf}(v_1,v_2,w) \wedge \text{isSingleChild}(w)$$". As above, restriction (iv) is not satisfied unless the following is a theorem of the theory under consideration:
$$\forall v_1. \forall v_2. \exists! w. \text{isAdult}(v_1) \wedge \text{isAdult}(v_2) \wedge \text{parentsOf}(v_1,v_2,w) \wedge \text{isSingleChild}(w)$$
But if the sentence given above is a theorem of your theory, then you can already prove (directly, starting from the sentence above as a premise, and using $$\forall E$$, $$\wedge E$$ and $$\forall I$$) that $$\forall v_1. \text{isAdult}(v_1)$$ is a theorem of your theory.
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Algebra and Trigonometry
# 7.4The Other Trigonometric Functions
Algebra and Trigonometry7.4 The Other Trigonometric Functions
### Learning Objectives
In this section you will:
• Find exact values of the trigonometric functions secant, cosecant, tangent, and cotangent of$π 3 , π 4 , π 3 , π 4 ,$and$π 6 . π 6 .$
• Use reference angles to evaluate the trigonometric functions secant, tangent, and cotangent.
• Use properties of even and odd trigonometric functions.
• Recognize and use fundamental identities.
• Evaluate trigonometric functions with a calculator.
A wheelchair ramp that meets the standards of the Americans with Disabilities Act must make an angle with the ground whose tangent is$1 12 1 12$or less, regardless of its length. A tangent represents a ratio, so this means that for every 1 inch of rise, the ramp must have 12 inches of run. Trigonometric functions allow us to specify the shapes and proportions of objects independent of exact dimensions. We have already defined the sine and cosine functions of an angle. Though sine and cosine are the trigonometric functions most often used, there are four others. Together they make up the set of six trigonometric functions. In this section, we will investigate the remaining functions.
### Finding Exact Values of the Trigonometric Functions Secant, Cosecant, Tangent, and Cotangent
We can also define the remaining functions in terms of the unit circle with a point$( x,y ) ( x,y )$corresponding to an angle of$t, t,$ as shown in Figure 1. As with the sine and cosine, we can use the$( x,y ) ( x,y )$coordinates to find the other functions.
Figure 1
The first function we will define is the tangent. The tangent of an angle is the ratio of the y-value to the x-value of the corresponding point on the unit circle. In Figure 1, the tangent of angle$t t$is equal to$y x ,x≠0. y x ,x≠0.$Because the y-value is equal to the sine of$t, t,$ and the x-value is equal to the cosine of$t, t,$the tangent of angle$t t$can also be defined as$sin t cos t ,cos t≠0. sin t cos t ,cos t≠0.$The tangent function is abbreviated as$tan. tan.$The remaining three functions can all be expressed as reciprocals of functions we have already defined.
• The secant function is the reciprocal of the cosine function. In Figure 1, the secant of angle$t t$is equal to$1 cos t = 1 x ,x≠0. 1 cos t = 1 x ,x≠0.$The secant function is abbreviated as$sec. sec.$
• The cotangent function is the reciprocal of the tangent function. In Figure 1, the cotangent of angle$t t$is equal to$cos t sin t = x y ,y≠0. cos t sin t = x y ,y≠0.$The cotangent function is abbreviated as$cot. cot.$
• The cosecant function is the reciprocal of the sine function. In Figure 1, the cosecant of angle$t t$is equal to$1 sin t = 1 y ,y≠0. 1 sin t = 1 y ,y≠0.$The cosecant function is abbreviated as$csc. csc.$
### Tangent, Secant, Cosecant, and Cotangent Functions
If$t t$is a real number and$(x,y) (x,y)$is a point where the terminal side of an angle of$t t$radians intercepts the unit circle, then
### Example 1
#### Finding Trigonometric Functions from a Point on the Unit Circle
The point$( − 3 2 , 1 2 ) ( − 3 2 , 1 2 )$is on the unit circle, as shown in Figure 2. Find$sin t,cos t,tan t,sec t,csc t, sin t,cos t,tan t,sec t,csc t,$and$cot t. cot t.$
Figure 2
Try It #1
The point$( 2 2 ,− 2 2 ) ( 2 2 ,− 2 2 )$is on the unit circle, as shown in Figure 3. Find$sin t,cos t,tan t,sec t,csc t, sin t,cos t,tan t,sec t,csc t,$and$cot t. cot t.$
Figure 3
### Example 2
#### Finding the Trigonometric Functions of an Angle
Find$sin t,cos t,tan t,sec t,csc t, sin t,cos t,tan t,sec t,csc t,$and$cot t. cot t.$when$t= π 6 . t= π 6 .$
Try It #2
Find$sin t,cos t,tan t,sec t,csc t, sin t,cos t,tan t,sec t,csc t,$and$cot t. cot t.$when$t= π 3 . t= π 3 .$
Because we know the sine and cosine values for the common first-quadrant angles, we can find the other function values for those angles as well by setting$x x$equal to the cosine and$y y$equal to the sine and then using the definitions of tangent, secant, cosecant, and cotangent. The results are shown in Table 1.
Angle $0 0$
Cosine 1 $3 2 3 2$ $2 2 2 2$ $1 2 1 2$ 0
Sine 0 $1 2 1 2$ $2 2 2 2$ $3 2 3 2$ 1
Tangent 0 $3 3 3 3$ 1 $3 3$ Undefined
Secant 1 $2 3 3 2 3 3$ $2 2$ 2 Undefined
Cosecant Undefined 2 $2 2$ $2 3 3 2 3 3$ 1
Cotangent Undefined $3 3$ 1 $3 3 3 3$ 0
Table 1
### Using Reference Angles to Evaluate Tangent, Secant, Cosecant, and Cotangent
We can evaluate trigonometric functions of angles outside the first quadrant using reference angles as we have already done with the sine and cosine functions. The procedure is the same: Find the reference angle formed by the terminal side of the given angle with the horizontal axis. The trigonometric function values for the original angle will be the same as those for the reference angle, except for the positive or negative sign, which is determined by x- and y-values in the original quadrant. Figure 4 shows which functions are positive in which quadrant.
To help remember which of the six trigonometric functions are positive in each quadrant, we can use the mnemonic phrase “A Smart Trig Class.” Each of the four words in the phrase corresponds to one of the four quadrants, starting with quadrant I and rotating counterclockwise. In quadrant I, which is “A,” all of the six trigonometric functions are positive. In quadrant II, “Smart,” only sine and its reciprocal function, cosecant, are positive. In quadrant III, “Trig,” only tangent and its reciprocal function, cotangent, are positive. Finally, in quadrant IV, “Class,” only cosine and its reciprocal function, secant, are positive.
Figure 4 The trigonometric functions are each listed in the quadrants in which they are positive.
### How To
Given an angle not in the first quadrant, use reference angles to find all six trigonometric functions.
1. Measure the angle formed by the terminal side of the given angle and the horizontal axis. This is the reference angle.
2. Evaluate the function at the reference angle.
3. Observe the quadrant where the terminal side of the original angle is located. Based on the quadrant, determine whether the output is positive or negative.
### Example 3
#### Using Reference Angles to Find Trigonometric Functions
Use reference angles to find all six trigonometric functions of$− 5π 6 . − 5π 6 .$
Try It #3
Use reference angles to find all six trigonometric functions of$− 7π 4 . − 7π 4 .$
### Using Even and Odd Trigonometric Functions
To be able to use our six trigonometric functions freely with both positive and negative angle inputs, we should examine how each function treats a negative input. As it turns out, there is an important difference among the functions in this regard.
Consider the function$f(x)= x 2 , f(x)= x 2 ,$shown in Figure 5. The graph of the function is symmetrical about the y-axis. All along the curve, any two points with opposite x-values have the same function value. This matches the result of calculation:$(4) 2 = (−4) 2 , (−5) 2 = (5) 2 , (4) 2 = (−4) 2 , (−5) 2 = (5) 2 ,$and so on. So$f(x)= x 2 f(x)= x 2$is an even function, a function such that two inputs that are opposites have the same output. That means$f( −x )=f( x ). f( −x )=f( x ).$
Figure 5 The function$f(x)= x 2 f(x)= x 2$is an even function.
Now consider the function$f(x)= x 3 , f(x)= x 3 ,$shown in Figure 6. The graph is not symmetrical about the y-axis. All along the graph, any two points with opposite x-values also have opposite y-values. So$f(x)= x 3 f(x)= x 3$is an odd function, one such that two inputs that are opposites have outputs that are also opposites. That means$f( −x )=−f( x ). f( −x )=−f( x ).$
Figure 6 The function$f(x)= x 3 f(x)= x 3$is an odd function.
We can test whether a trigonometric function is even or odd by drawing a unit circle with a positive and a negative angle, as in Figure 7. The sine of the positive angle is$y. y.$The sine of the negative angle is$−y. −y.$The sine function, then, is an odd function. We can test each of the six trigonometric functions in this fashion. The results are shown in Table 2.
Figure 7
Table 2
### Even and Odd Trigonometric Functions
An even function is one in which$f(−x)=f(x). f(−x)=f(x).$
An odd function is one in which$f(−x)=−f(x). f(−x)=−f(x).$
Cosine and secant are even:
Sine, tangent, cosecant, and cotangent are odd:
### Example 4
#### Using Even and Odd Properties of Trigonometric Functions
If the secant of angle$t t$is 2, what is the secant of$−t? −t?$
Try It #4
If the cotangent of angle$t t$is$3 , 3 ,$what is the cotangent of$−t? −t?$
### Recognizing and Using Fundamental Identities
We have explored a number of properties of trigonometric functions. Now, we can take the relationships a step further, and derive some fundamental identities. Identities are statements that are true for all values of the input on which they are defined. Usually, identities can be derived from definitions and relationships we already know. For example, the Pythagorean Identity we learned earlier was derived from the Pythagorean Theorem and the definitions of sine and cosine.
### Fundamental Identities
We can derive some useful identities from the six trigonometric functions. The other four trigonometric functions can be related back to the sine and cosine functions using these basic relationships:
$tan t= sin t cos t tan t= sin t cos t$
$sec t= 1 cos t sec t= 1 cos t$
$csc t= 1 sin t csc t= 1 sin t$
$cot t= 1 tan t = cos t sin t cot t= 1 tan t = cos t sin t$
### Example 5
#### Using Identities to Evaluate Trigonometric Functions
1. Given$sin(45°)= 2 2 ,cos(45°)= 2 2 , sin(45°)= 2 2 ,cos(45°)= 2 2 ,$evaluate$tan(45°). tan(45°).$
2. Given$sin( 5π 6 )= 1 2 ,cos( 5π 6 )=− 3 2 , sin( 5π 6 )= 1 2 ,cos( 5π 6 )=− 3 2 ,$evaluate$sec( 5π 6 ). sec( 5π 6 ).$
Try It #5
Evaluate$csc( 7π 6 ). csc( 7π 6 ).$
### Example 6
#### Using Identities to Simplify Trigonometric Expressions
Simplify$sec t tan t . sec t tan t .$
Try It #6
Simplify$(tan t)(cos t). (tan t)(cos t).$
#### Alternate Forms of the Pythagorean Identity
We can use these fundamental identities to derive alternate forms of the Pythagorean Identity,$cos 2 t+ sin 2 t=1. cos 2 t+ sin 2 t=1.$One form is obtained by dividing both sides by$cos 2 t. cos 2 t.$
$cos 2 t cos 2 t + sin 2 t cos 2 t = 1 cos 2 t 1+ tan 2 t = sec 2 t cos 2 t cos 2 t + sin 2 t cos 2 t = 1 cos 2 t 1+ tan 2 t = sec 2 t$
The other form is obtained by dividing both sides by$sin 2 t. sin 2 t.$
$cos 2 t sin 2 t + sin 2 t sin 2 t = 1 sin 2 t cot 2 t+1 = csc 2 t cos 2 t sin 2 t + sin 2 t sin 2 t = 1 sin 2 t cot 2 t+1 = csc 2 t$
### Alternate Forms of the Pythagorean Identity
$1+ tan 2 t= sec 2 t 1+ tan 2 t= sec 2 t$
$cot 2 t+1= csc 2 t cot 2 t+1= csc 2 t$
### Example 7
#### Using Identities to Relate Trigonometric Functions
If$cos(t)= 12 13 cos(t)= 12 13$and$t t$is in quadrant IV, as shown in Figure 8, find the values of the other five trigonometric functions.
Figure 8
### Try It #7
If$sec(t)=− 17 8 sec(t)=− 17 8$and$0find the values of the other five functions.
As we discussed at the beginning of the chapter, a function that repeats its values in regular intervals is known as a periodic function. The trigonometric functions are periodic. For the four trigonometric functions, sine, cosine, cosecant and secant, a revolution of one circle, or$2π, 2π,$will result in the same outputs for these functions. And for tangent and cotangent, only a half a revolution will result in the same outputs.
Other functions can also be periodic. For example, the lengths of months repeat every four years. If$x x$represents the length time, measured in years, and$f(x) f(x)$represents the number of days in February, then$f(x+4)=f(x). f(x+4)=f(x).$This pattern repeats over and over through time. In other words, every four years, February is guaranteed to have the same number of days as it did 4 years earlier. The positive number 4 is the smallest positive number that satisfies this condition and is called the period. A period is the shortest interval over which a function completes one full cycle—in this example, the period is 4 and represents the time it takes for us to be certain February has the same number of days.
### Period of a Function
The period$P P$of a repeating function$f f$is the number representing the interval such that$f(x+P)=f(x) f(x+P)=f(x)$for any value of$x. x.$
The period of the cosine, sine, secant, and cosecant functions is$2π. 2π.$
The period of the tangent and cotangent functions is$π. π.$
### Example 8
#### Finding the Values of Trigonometric Functions
Find the values of the six trigonometric functions of angle$t t$based on Figure 9.
Figure 9
### Try It #8
Find the values of the six trigonometric functions of angle$t t$based on Figure 10.
Figure 10
### Example 9
#### Finding the Value of Trigonometric Functions
If$sin(t)=− 3 2 and cos(t)= 1 2 ,find sec(t),csc(t),tan(t),cot(t). sin(t)=− 3 2 and cos(t)= 1 2 ,find sec(t),csc(t),tan(t),cot(t).$
### Try It #9
$sin(t)= 2 2 and cos(t)= 2 2 ,find sec(t),csc(t),tan(t),and cot(t) sin(t)= 2 2 and cos(t)= 2 2 ,find sec(t),csc(t),tan(t),and cot(t)$
### Evaluating Trigonometric Functions with a Calculator
We have learned how to evaluate the six trigonometric functions for the common first-quadrant angles and to use them as reference angles for angles in other quadrants. To evaluate trigonometric functions of other angles, we use a scientific or graphing calculator or computer software. If the calculator has a degree mode and a radian mode, confirm the correct mode is chosen before making a calculation.
Evaluating a tangent function with a scientific calculator as opposed to a graphing calculator or computer algebra system is like evaluating a sine or cosine: Enter the value and press the TAN key. For the reciprocal functions, there may not be any dedicated keys that say CSC, SEC, or COT. In that case, the function must be evaluated as the reciprocal of a sine, cosine, or tangent.
If we need to work with degrees and our calculator or software does not have a degree mode, we can enter the degrees multiplied by the conversion factor$π 180 π 180$to convert the degrees to radians. To find the secant of$30°, 30°,$we could press
### How To
Given an angle measure in radians, use a scientific calculator to find the cosecant.
1. If the calculator has degree mode and radian mode, set it to radian mode.
2. Enter:$1/ 1/$
3. Enter the value of the angle inside parentheses.
4. Press the SIN key.
5. Press the = key.
### How To
Given an angle measure in radians, use a graphing utility/calculator to find the cosecant.
• If the graphing utility has degree mode and radian mode, set it to radian mode.
• Enter:$1/ 1/$
• Press the SIN key.
• Enter the value of the angle inside parentheses.
• Press the ENTER key.
### Example 10
#### Evaluating the Cosecant Using Technology
Evaluate the cosecant of$5π 7 . 5π 7 .$
Try It #10
Evaluate the cotangent of$− π 8 . − π 8 .$
### Media
Access these online resources for additional instruction and practice with other trigonometric functions.
### 7.4 Section Exercises
#### Verbal
1.
On an interval of$[ 0,2π ), [ 0,2π ),$can the sine and cosine values of a radian measure ever be equal? If so, where?
2.
What would you estimate the cosine of$π π$degrees to be? Explain your reasoning.
3.
For any angle in quadrant II, if you knew the sine of the angle, how could you determine the cosine of the angle?
4.
Describe the secant function.
5.
Tangent and cotangent have a period of$π. π.$What does this tell us about the output of these functions?
#### Algebraic
For the following exercises, find the exact value of each expression.
6.
$tan π 6 tan π 6$
7.
$sec π 6 sec π 6$
8.
$csc π 6 csc π 6$
9.
$cot π 6 cot π 6$
10.
$tan π 4 tan π 4$
11.
$sec π 4 sec π 4$
12.
$csc π 4 csc π 4$
13.
$cot π 4 cot π 4$
14.
$tan π 3 tan π 3$
15.
$sec π 3 sec π 3$
16.
$csc π 3 csc π 3$
17.
$cot π 3 cot π 3$
For the following exercises, use reference angles to evaluate the expression.
18.
$tan 5π 6 tan 5π 6$
19.
$sec 7π 6 sec 7π 6$
20.
$csc 11π 6 csc 11π 6$
21.
$cot 13π 6 cot 13π 6$
22.
$tan 7π 4 tan 7π 4$
23.
$sec 3π 4 sec 3π 4$
24.
$csc 5π 4 csc 5π 4$
25.
$cot 11π 4 cot 11π 4$
26.
$tan 8π 3 tan 8π 3$
27.
$sec 4π 3 sec 4π 3$
28.
$csc 2π 3 csc 2π 3$
29.
$cot 5π 3 cot 5π 3$
30.
$tan 225° tan 225°$
31.
$sec 300° sec 300°$
32.
$csc 150° csc 150°$
33.
$cot 240° cot 240°$
34.
$tan 330° tan 330°$
35.
$sec 120° sec 120°$
36.
$csc 210° csc 210°$
37.
$cot 315° cot 315°$
38.
If$sin t= 3 4 , sin t= 3 4 ,$and$t t$is in quadrant II, find$cos t,sec t,csc t,tan t, cos t,sec t,csc t,tan t,$and$cot t. cot t.$
39.
If$cos t=− 1 3 , cos t=− 1 3 ,$and$t t$is in quadrant III, find$sin t,sec t,csc t,tan t, sin t,sec t,csc t,tan t,$and$cot t. cot t.$
40.
If$tan t= 12 5 , tan t= 12 5 ,$and$0≤t< π 2 , 0≤t< π 2 ,$find$sin t,cos t,sec t,csc t,and cot t. sin t,cos t,sec t,csc t,and cot t.$
41.
If$sin t= 3 2 sin t= 3 2$and$cos t= 1 2 , cos t= 1 2 ,$find$sec t,csc t,tan t, sec t,csc t,tan t,$and$cot t. cot t.$
42.
If$sin 40°≈0.643 sin 40°≈0.643$and$cos 40°≈0.766, cos 40°≈0.766,$find$sec 40°,csc 40°,tan 40°, sec 40°,csc 40°,tan 40°,$and$cot 40°. cot 40°.$
43.
If$sin t= 2 2 , sin t= 2 2 ,$what is the$sin(−t)? sin(−t)?$
44.
If$cos t= 1 2 , cos t= 1 2 ,$what is the$cos(−t)? cos(−t)?$
45.
If$sec t=3.1, sec t=3.1,$what is the$sec(−t)? sec(−t)?$
46.
If$csc t=0.34, csc t=0.34,$what is the$csc(−t)? csc(−t)?$
47.
If$tan t=−1.4, tan t=−1.4,$what is the$tan(−t)? tan(−t)?$
48.
If$cot t=9.23, cot t=9.23,$what is the$cot(−t)? cot(−t)?$
#### Graphical
For the following exercises, use the angle in the unit circle to find the value of the each of the six trigonometric functions.
49.
50.
51.
#### Technology
For the following exercises, use a graphing calculator to evaluate to three decimal places.
52.
$csc 5π 9 csc 5π 9$
53.
$cot 4π 7 cot 4π 7$
54.
$sec π 10 sec π 10$
55.
$tan 5π 8 tan 5π 8$
56.
$sec 3π 4 sec 3π 4$
57.
$csc π 4 csc π 4$
58.
$tan 98° tan 98°$
59.
$cot 33° cot 33°$
60.
$cot 140° cot 140°$
61.
$sec 310° sec 310°$
#### Extensions
For the following exercises, use identities to evaluate the expression.
62.
If$tan( t )≈2.7, tan( t )≈2.7,$and$sin( t )≈0.94, sin( t )≈0.94,$find$cos( t ). cos( t ).$
63.
If$tan( t )≈1.3, tan( t )≈1.3,$and$cos( t )≈0.61, cos( t )≈0.61,$find$sin( t ). sin( t ).$
64.
If$csc( t )≈3.2, csc( t )≈3.2,$and$cos( t )≈0.95, cos( t )≈0.95,$find$tan( t ). tan( t ).$
65.
If$cot( t )≈0.58, cot( t )≈0.58,$and$cos( t )≈0.5, cos( t )≈0.5,$find$csc( t ). csc( t ).$
66.
Determine whether the function$f(x)=2sinx cos x f(x)=2sinx cos x$is even, odd, or neither.
67.
Determine whether the function$f(x)=3 sin 2 x cos x+sec x f(x)=3 sin 2 x cos x+sec x$is even, odd, or neither.
68.
Determine whether the function$f(x)=sin x−2 cos 2 x f(x)=sin x−2 cos 2 x$is even, odd, or neither.
69.
Determine whether the function$f(x)= csc 2 x+sec x f(x)= csc 2 x+sec x$is even, odd, or neither.
For the following exercises, use identities to simplify the expression.
70.
$csc t tan t csc t tan t$
71.
$sec t csc t sec t csc t$
#### Real-World Applications
72.
The amount of sunlight in a certain city can be modeled by the function$h=15cos( 1 600 d ), h=15cos( 1 600 d ),$where$h h$represents the hours of sunlight, and$d d$is the day of the year. Use the equation to find how many hours of sunlight there are on February 10, the 42nd day of the year. State the period of the function.
73.
The amount of sunlight in a certain city can be modeled by the function$h=16cos( 1 500 d ), h=16cos( 1 500 d ),$where$h h$represents the hours of sunlight, and$d d$is the day of the year. Use the equation to find how many hours of sunlight there are on September 24, the 267th day of the year. State the period of the function.
74.
The equation$P=20sin( 2πt )+100 P=20sin( 2πt )+100$models the blood pressure,$P, P,$where$t t$represents time in seconds. (a) Find the blood pressure after 15 seconds. (b) What are the maximum and minimum blood pressures?
75.
The height of a piston,$h, h,$in inches, can be modeled by the equation$y=3sin x+1, y=3sin x+1,$where$x x$represents the crank angle. Find the height of the piston when the crank angle is$55°. 55°.$
76.
The height of a piston,$h, h,$in inches, can be modeled by the equation$y=2cos x+5, y=2cos x+5,$where$x x$represents the crank angle. Find the height of the piston when the crank angle is$55°. 55°.$
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# Power to Ramanujan in 2017
$x^{1729}\equiv 1\pmod{2017}$
How many positive integer solutions $$x<2017$$ does the congruency above have?
×
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# Maths Sets - Online Test
Q1. Two sets A and B are said to be disjoint iff
Explaination / Solution:
Two sets are called disjoint if and only if these two set have no common element i.e A∩B=∅
Q2. Which of the following is a null set ?
Explaination / Solution:
[i=imaginory root of unity which is a complex no.]
since the solution of x doesnot belongs to real no hence the set is null set
Q3. If A ⊆B , then A∩B is equal to
Explaination / Solution:
A ⊆B means Set A is contained in the set B.So common region is The Set A
Q4. If A ⊆B , then A∪B is equal to
Explaination / Solution:
A ⊆B refers to A set is contained in the Set B.So Set B is bigger.So union the sets will be B
Q5. If A and B are two sets , then A∪(A∩B) is equal to
Explaination / Solution:
LetA={1,2,3,4}andB={1,2,3,4,5,6}HereA∩B={1,2,3,4}NowA∪(A∩B)={1,2,3,4,}=A
Q6. If A and B are two sets , then A∩(A∪B) is equal to
Explaination / Solution:
LetA={1,2,3,4}andB={1,2,3,4,5,6}HereA∪B={1,2,3,4,5,6}NowA∩(A∪B)={1,2,3,4,}=A
Q7. If A = { 2,3,4,8,10 } ,B = { 3,4,5,10,12 } and C = { 4,5,6,12,14 } , then (A∩B)∪(A∩C) then
Explaination / Solution:
Q8. If A and B are disjoint Set , then n ( A∪B) is equal to
Explaination / Solution:
Q9. If A and B are not disjoint Set , then n (A∪B) is equal to
Explaination / Solution:
Q10. The Collection of intelligent students in a class is
Explaination / Solution:
Intelligency Can not measured by numbers i.e the collection is not well defined thats why it can not be called as a Set
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# An application of s-elementary wavelets in numerical solution of differential and fractional integral equations
Document Type : Research Paper
Authors
1 Department of Mathematics, Payame Noor University (PNU) P. O. Box 19395-4697, Tehran, Iran
2 Department of Applied Mathematics, Faculty of Mathematics and Computer, Shahid Bahonal University of Kerman, Kerman, Iran.
3 Department of Applied Mathematics, Faculty of Mathematics and Computer & Mahani Mathematical Research Center, Shahid Bahonar University of Kerman, Kerman, Iran
Abstract
In this article we introduce wavelet sets and consider a special wavelet set in R. We build a basis associated to this type wavelet sets and use operational matrix of this basis to solve nonlinear Riccati differential equations and Riemann-Liouville fractional integral equations of order $\alpha >0$, numerically. Convergence analysis of this basis is investigated. Also, we give examples that show the accuracy of the new method by comparing it with previous methods.
Keywords
#### References
[1] S. Abbasbandy, A new application of He's variational iteration method for quadratic Riccati di erential equation by using Adomian's polynomials, Journal of Computational and Applied Mathematics. vol. 207 (2007) 59{63.
[2] S. Abbasbandy, Homotopy perturbation method for quadratic Riccati di erential equation and comparison with Adomian's decomposition method, Journal of Applied Mathematics and Computation. vol. 172 (2006) 485{490.
[3] S. Abbasbandy, Iterated He's homotopy perturbation method for quadratic Riccati differential equation, Journal of Applied Mathematics and Computation. vol. 175 (2006) 581{589.
[4] J. J. Benedetto and S. Sumetkijakan, A fractal set constructed from class of wavelet sets, Inverse Problems, Image Analysis, and Medical Imaging, Contemporary Mathematics, vol. 313, American Mathematical Society, Providence, RI. (2002) 19-35.
[5] C. K. Chui, An Introduction to Wavelets, Academic Press, New York, 1992.
[6] X. Dai and D. R. Larson, Wandering vectors for unitary systems and orthogonal wavelets, volume 134 of Memoirs of American Mathematical Society, Providence R.I, 1998.
[7] X. Dai, D. R. Larson, and D. M. Speegle, Wavelet sets in Rn II, Wavelets, Multiwavlets and Their Application, Contemporary Mathematics. vol. 216 (1998) 15-40.
[8] X. Dai, and S. Lu. Wavelets in subspecies, Journal of Michigan Mathematical. vol. 43, (1996) 81-98.
[9] I. Daubechies, Ten Lectures on Wavelets, Society for industrial and applied mathematics, Pennsylvania, 1992.
[10] H. Deilami Azodi, The Fibonacci polynomials solution for Abel's integral equation of second kind, Journal of Numerical Analysis and Optimization vol. 10, no. 1 (2020) 63-79.
[11] M. A. El-Tawil, A. A. Bahnasawi, A. Abdel-Naby, Solving Riccati di erential equation using Adomian's decomposition method, Journal of Applied Mathematics and Computation vol. 157 (2004) 503{514.
[12] X. Fang and X. Wang, Construction of minimally- supported-frequencies wavelets, Journal of Fourier Analysis and Applications vol. 2, no. 4 (1996) 315-327.
[13] J. P. Gabardo and X. Yu, Construction of wavelet sets with certain self-similarity properties, Journal of Geometric Analysis vol. 14, no. 4 (2004) 629{651.
[14] J. H. He, Comparison of homotopy perturbation method and homotopy analysis method, Journal of Applied Mathematics and Computation vol. 156, no. 2 (2004) 527{539.
[15] E. Hernandez, X. Wang, and G. Weiss, Smoothing minimally supported frequency (MSF) wavelets: Part II, Journal of Fourier Analysis and Applications vol. 2 (1995) 329{340.
[16] E. Hernandez and G. Weiss, A First course on wavelets, CRC Press, Boca Raton, FL, 1996.
[17] M. Izadi, Fractional polynomial approximations to the solution of fractional Riccati equation, Punjab university journal of mathematics vol. 51, no. 11 (2019) 123-141.
[18] A. Khalouta, The Existence and Uniqueness of Solution for Fractional Newel-Whitehead-Segel Equation within Caputo-Fabrizio Fractional Operator, Journal of Applications and Applied Mathematics vol. 16, no. 2 (2021) 894-909.
[19] A. Khalouta and A. KademA, new reliable method and its convergence for nonlinear second-order fractional di erential equations, Journal of Tbilisi Mathematical . vol. 13, no. 3 (2020) 133-143
[20] S. Kumbinarasaiah and R. A. Mundewa, Numerical Method for the Solution of Abel's Integral Equations using Laguerre Wavelet, Journal of Information and Computing Science, vol. 14, no. 4 (2019) 250-258.
[21] U. Lepik, Solving fractional integral equations by the Haar wavelet method, Journal of Applied Mathematics and Computation vol. 214, no. 2 (2009) 468{478.
[22] C. Li and Y.Wang, Numerical algorithm based on Adomian decomposition for fractional di erential equations, Journal of Computers & Mathematics with Applications vol. 57, no. 10 (2009) 1672{1681.
[23] S. G. Mallat, Multiresolution approximations and orthonormal bases of L2 (R), Journal of Transactions of the American mathematical society vol. 315, no. 1 (1989) 69-87.
[24] Y. Meyer Wavelets and Operators, Cambridge Studies in Advanced Mathematics, Edinburgh 1992.
[25] F. Mohammadi, M. M. Hosseini, A comparative study of numerical methods for solving quadratic Riccati di erential equations, Journal of the Franklin Institute vol. 348 (2011) 156{164.
[26] R. K. Pandey, O. P. Singh and V. K. Singh, Ecient algorithms to solve singular integral equations of Abel type, Journal of Computers and Mathematics with Applications vol. 57, no. 4 (2009) 664{676.
[27] H. Saeedi, N. Mollahasani, M. Moghadam, G. Chuev, An operational Haar wavelet method for solving fractional Volterra integral equations, Journal of Applied Mathematics and Computer Science vol. 21, no. 3 (2011) 535-547.
[28] E. Sokhanvar, A. Askari-Hemmat, A numerical method for solving delay-fractional di erential and integro-di erential equations, Journal of Mahani Mathematical Research Center vol. 4, no. 1-2 (2015) 11-24.
[29] Y. Tan, S. Abbasbandy, Homotopy analysis method for quadratic Riccati di erential equation, Journal of Communications in Nonlinear Science and Numerical Simulation Vol. 13, no. 3 (2008) 539-546.
[30] Li, Yuanlu and Sun, Ning and Zheng, Bochao and Wang, Qi and Zhang, Yingchao, Wavelet operational matrix method for solving the Riccati di erential equation, Journal of Communications in Nonlinear Science and Numerical Simulation vol. 19, no. 3 (2014) 483{493.
[31] K. B. M. Q. Zaman and J. C. Yu, Power spectral density of subsonic jet noise, Journal of Sound and Vibration. vol. 98, no. 4 (1995) 519{537.
### History
• Receive Date: 07 January 2022
• Revise Date: 01 April 2022
• Accept Date: 18 April 2022
• First Publish Date: 18 April 2022
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# Axiom of infinity?
Homework Helper
In ZF, the axiom of infinity says that the set of natural numbers exists. I was wondering if there was a (finitist?) weakening of ZF that included the axiom "the class of natural numbers exists".
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# Construct an explicit isomorphism
1. Dec 24, 2013
### bedi
$\Bbb{R}P^1$ bundle isomorphic to the Mobius bundle
I'm trying to construct an explicit isomorphism from $E = \{([x], v) : [x] ∈ \Bbb{R}P^1, v ∈ [x]\}$ to $T = [0, 1] × R/ ∼$ where $(0, t) ∼ (1, −t)$. I verified that $\Bbb{R}P^1$ is homeomorphic to $\Bbb{S}^1$ which is homeomorphic to $[0,1]/∼$ where $0∼1$. So this is the map I have in my mind: $([x],v)\to (x,(1-x)v+xe^v)$. Does that work? It doesn't look very natural.
2. Jan 4, 2014
### WWGD
How about pulling back the bundle using the homeomorphism?
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# Is a subspace the direct sum of all its intersections with a partition of the basis?
1. May 25, 2012
### imurme8
I've been working on this Linear Algebra problem for a while: Let $F$ be a field, $V$ a vector space over $F$ with basis $\mathcal{B}=\{b_i\mid i\in I\}$. Let $S$ be a subspace of $V$, and let $\{B_1, \dotsc, B_k\}$ be a partition of $\mathcal{B}$. Suppose that $S\cap \langle B_i\rangle\neq \{0\}$ for all $i$. Is it true that $S=\bigoplus\limits_{i=1}^{k}(S\cap \langle B_i \rangle)$?
Haven't been able to get this one, thanks for your help.
2. May 26, 2012
### jgens
Re: Is a subspace the direct sum of all its intersections with a partition of the bas
Notice that $V = \bigoplus_{i=1}^k \langle B_i \rangle$, so $S = S \cap V = \bigoplus_{i=1}^k S \cap \langle B_i \rangle$.
3. May 26, 2012
### imurme8
Re: Is a subspace the direct sum of all its intersections with a partition of the bas
Where have you used that $S\cap \langle B_i\rangle \neq \{0\}$ for all $i$? I can come up with the following counterexample if we do not assume this hypothesis:
In $\mathbb{R}^2$, the subspace $y=x$ is certainly not the direct sum of its intersections with $\langle e_1 \rangle$ and $\langle e_2 \rangle$ (both zero).
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# Network Embedding
Information network mining often requires examination of linkage relationships between nodes for analysis. Recently, network representation has emerged to represent each node in a vector format, embedding network structure, so off-the-shelf machine learning methods can be directly applied for analysis. We have proposed a number of algorithms to address this problem, including:
## Continuous Network Embedding
Continuous network embedding has been a hot topic since 2014, which aims to embed each node into a compact and continuous vector space. Our developments include:
## Discrete Network Embedding
The network embedding is typically represented in continuous vector, which imposes formidable challenges in storage and computation costs, particularly in largescale applications. To address the issue, we propose to learn succinct and discrete node representation for fast node recommendation and classification. Our methods include:
• DNE: Discrete Network Embedding (IJCAI-18). This is the first work for discrete network embedding, which deals with a plain network without attribute information. The node is represented in a binary vector space.
• BANE: Binarized Attributed Network Embedding (ICDM-18). This is the first discrete network embedding algorithm which exploits both structure and attribute information to learn a binary code for each node in an attribute network. [Code]
• LQANR: Low-Bit Quantization for Attributed Network Representation Learnin (IJCAI-19). BANE algorithm may suffer information loss when we represent nodes in a binary space. In this paper, we represent each node in a low-bit width space. In this case, each node is represented as a low bit vector, which have a better performance in various downstream tasks.
### TriDNR: Tri-Party Deep Network Representation Learning (IJCAI-16)
• TriDNR exploits node structure, node content, and node labels (if available) to jointly learn optimal node representation.
• Codes and Data are available here.
### ARGA: Adversarially Regularized Graph Autoencoder for Graph Embedding (IJCAI-18)
• ARGA is a novel adversarial graph embedding framework for graph data.
• Codes and Data are available here.
### DNE: Discrete Network Embedding (IJCAI-18)
• DNE learns short binary codes to represent each node in a plain network, which exhibits lower storage and computational complexity than state-of-the-art network embedding methods, while obtains competitive classification results.
• DNE is the first algorithm for learning binary representation for a plain network (without attibute information for nodes).
### ANRMAB: Active Discriminative Network Representation Learning (IJCAI-18)
• Label information is valuable for learning the discriminative network representations. ANRMAB actively seeks nodes to label to learn discriminative network representations with a multi-armed bandit mechanism.
### MGAE: Marginalized Graph Autoencoder for Graph Clustering (CIKM-17)
• MGAE is a stacked graph convolutional autoencoder model to learn latent representation for the graph clustering tasks.
• Codes and Data are available here.
##### Shirui Pan
###### Assistant Professor
My research interests include data mining, machine learning, and graph analysis.
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Software › pipelines
# Customized Secondary Analysis using cellranger-atac reanalyze
The cellranger-atac reanalyze command reruns secondary analysis performed on the peak-barcode matrix (dimensionality reduction, clustering and visualization) using different parameter settings.
## Command Line Interface
These are the most common command line arguments (run cellranger-atac reanalyze --help for a full list):
ArgumentDescription
--id=IDA unique run ID string: e.g. AGG123_reanalysis
--peaks=BEDPath to a peaks.bed from a completed pipestance (cellranger-atac count, cellranger-atac reanalyze or cellranger-atac aggr) or custom peaks.
--fragments=TSVPath to a block-gzipped TSV file of fragments from a completed pipestance (cellranger-atac count, cellranger-atac reanalyze or cellranger-atac aggr). A tabix (.tbi) index file of the same name is expected to be present in the same directory, otherwise specify using optional argument --index
--reference=PATHPath to a Cell Ranger ATAC reference.
--params=CSV(optional) Path to a CSV file containing a list of valid parameters and the values to use for them (see Parameters).
--index=TBI(optional) A tabix (.tbi) index corresponding to the input fragments file. Specify this if the filename differs from that of the fragments file, or if the fragments file and its index are located in different paths.
--agg=CSV(optional) Path to a CSV file that was used for cellranger-atac aggr. This allows you to retain any metadata associated with the samples for display in Loupe Browser.
--barcodes=CSV(optional) Path to a CSV file in the singlecell.csv format with a list of cell associated barcodes to use for reanalysis. All barcodes must be present in the fragments file. If this option is not provided, the pipeline does cell calling.
--force-cells=NUM(optional) Force pipeline to use this number of cells during the cell detection algorithm. Use this if the number of cells estimated by Cell Ranger ATAC is not consistent with the barcode rank plot.
After specifying these input arguments, run cellranger-atac reanalyze. In this example, we're reanalyzing the results of an aggregation named AGG123:
$cd /home/jdoe/runs$ ls -1 AGG123/outs/*.gz # verify the input file exists
AGG123/outs/fragments.tsv.gz
\$ cellranger-atac reanalyze --id=AGG123_reanalysis \
--peaks=AGG123/outs/peaks.bed \
--params=AGG123_reanalysis.csv \
--reference=/home/jdoe/refs/hg19 \
--fragments=/home/jdoe/runs/AGG123/outs/fragments.tsv.gz
The pipeline will begin to run, creating a new folder named with the reanalysis ID you specified (e.g. /home/jdoe/runs/AGG123_reanalysis) for its output. If this folder already exists, cellranger-atac will assume it is an existing pipestance and attempt to resume running it.
## Pipeline Outputs
A successful run should conclude with a message similar to this:
2019-03-22 12:45:22 [runtime] (run:hydra) ID.AGG123_reanalysis.SC_ATAC_REANALYZER_CS.SC_ATAC_REANALYZER.CLOUPE_PREPROCESS.fork0.join
2019-03-22 12:46:04 [runtime] (join_complete) ID.AGG123_reanalysis.SC_ATAC_REANALYZER_CS.SC_ATAC_REANALYZER.CLOUPE_PREPROCESS
2019-03-22 12:46:04 [runtime] VDR killed 270 files, 18 MB.
Outputs:
- Summary of all data metrics: /home/jdoe/runs/AGG123_reanalysis/outs/summary.json
- csv summarizing important metrics and values: /home/jdoe/runs/AGG123_reanalysis/outs/summary.csv
- Per-barcode fragment counts & metrics: /home/jdoe/runs/AGG123_reanalysis/outs/singlecell.csv
- Raw peak barcode matrix in hdf5 format: /home/jdoe/runs/AGG123_reanalysis/outs/raw_peak_bc_matrix.h5
- Raw peak barcode matrix in mex format: /home/jdoe/runs/AGG123_reanalysis/outs/raw_peak_bc_matrix
- Filtered peak barcode matrix in hdf5 format: /home/jdoe/runs/AGG123_reanalysis/outs/filtered_peak_bc_matrix.h5
- Filtered peak barcode matrix in mex format: /home/jdoe/runs/AGG123_reanalysis/outs/filtered_peak_bc_matrix
- Directory of analysis files: /home/jdoe/runs/AGG123_reanalysis/outs/analysis
- HTML file summarizing aggregation analysis : /home/jdoe/runs/AGG123_reanalysis/outs/web_summary.html
- Filtered tf barcode matrix in hdf5 format: /home/jdoe/runs/AGG123_reanalysis/outs/filtered_tf_bc_matrix.h5
- Filtered tf barcode matrix in mex format: /home/jdoe/runs/AGG123_reanalysis/outs/filtered_tf_bc_matrix
- Loupe Cell Browser input file: /home/jdoe/runs/AGG123_reanalysis/outs/cloupe.cloupe
- Annotation of peaks with genes: /home/jdoe/runs/AGG123_reanalysis/outs/peak_annotation.tsv
- Barcoded and aligned fragment file: /home/jdoe/runs/AGG123_reanalysis/outs/fragments.tsv.gz
- Fragment file index: /home/jdoe/runs/AGG123_reanalysis/outs/fragments.tsv.gz.tbi
Pipestance completed successfully!
Refer to the Analysis page for an explanation of the output.
## Parameters
The CSV file passed to --params should have 0 or more rows, one for every parameter that you want to customize. There is no header row. If a parameter is not specified in your CSV, its default value will be used. See Common Use Cases for some examples.
Here is a detailed description of each parameter. For parameters that subset the data, a default value of null indicates that no subsetting happens by default.
ParameterTypeDefault ValueRecommended RangeDescription
dim_reducestrlsa[lsa, pca, plsa]Pick dimensionality reduction technique.
num_analysis_bcsintnullCannot be set higher than the available number of cells or lower than zero.Randomly subset data to N barcodes for all analyses. Reduce this parameter if you want to improve performance or simulate results from lower cell counts. Resets to available number of cells if specified to be higher than it.
num_dr_bcsintnullCannot be set higher than the available number of cells.Randomly subset data to N barcodes when computing PCA projection (the most memory-intensive step). The PCA projection will still be applied to the full dataset, i.e. your final results will still reflect all the data. Try reducing this parameter if your analysis is running out of memory.
num_dr_featuresintnullCannot be set higher than the number of peaks in the bed file.Subset data to the top N features (that is, peaks, ranked by normalized dispersion) when computing LSA/PCA/PLSA projection (the most memory intensive step). The dimreduce projection will still be applied to the full dataset, i.e. your final results will still reflect all the data. Try reducing this parameter if your analysis is running out of memory.
num_compsint1510-100 (20 for PLSA), depending on the number of cell populations / clusters you expect to see.Compute N principal components for LSA/PCA/PLSA. Setting this too high may cause spurious clusters to be called.
graphclust_neighborsint010-500, depending on desired granularity.Number of nearest-neighbors to use in the graph-based clustering. Lower values result in higher-granularity clustering. The actual number of neighbors used is the maximum of this value and that determined by neighbor_a and neighor_b. Set this value to zero to use those values instead.
neighbor_afloat-230.0Determines how clustering granularity scales with cell count.The number of nearest neighbors, k, used in the graph-based clustering is computed as follows: k = neighbor_a + neighbor_b * log10(n_cells). The actual number of neighbors used is the maximum of this value and graphclust_neighbors.
neighbor_bfloat120.0Determines how clustering granularity scales with cell count.The number of nearest neighbors, k, used in the graph-based clustering is computed as follows: k = neighbor_a + neighbor_b * log10(n_cells). The actual number of neighbors used is the maximum of this value and graphclust_neighbors.
max_clustersint1010-50, depending on the number of cell populations / clusters you expect to see.Compute K-means clustering using K values of 2 to N. Setting this too high may cause spurious clusters to be called.
tsne_input_pcsintnullCannot be set higher than the num_comps parameter.Subset to top N principal components for TSNE. Change this parameter if you want to see how the TSNE plot changes when using fewer PCs, independent of the clustering / differential expression. You may find that TSNE is faster and/or the output looks better when using fewer PCs.
tsne_perplexityint3030-50TSNE perplexity parameter (see the TSNE FAQ for more details). When analyzing 100k+ cells, increasing this parameter may improve TSNE results, but the algorithm will be slower.
tsne_thetafloat0.5Must be between 0 and 1.TSNE theta parameter (see the TSNE FAQ for more details). Higher values yield faster, more approximate results (and vice versa). The runtime and memory performance of TSNE will increase dramatically if you set this below 0.25.
tsne_max_dimsint2Must be 2 or 3.Maximum number of TSNE output dimensions. Set this to 3 to produce both 2D and 3D TSNE projections (note: runtime will increase significantly).
tsne_max_iterint10001000-10000Number of total TSNE iterations. Try increasing this if TSNE results do not look good on larger numbers of cells. Runtime increases linearly with number of iterations.
tsne_stop_lying_iterint250Cannot be set higher than tsne_max_iter.Iteration at which TSNE learning rate is reduced. Try increasing this if TSNE results do not look good on larger numbers of cells.
tsne_mom_switch_iterint250Cannot be set higher than tsne_max_iter.Iteration at which TSNE momentum is reduced. Try increasing this if TSNE results do not look good on larger numbers of cells. Cannot be set higher than tsne_max_iter.
random_seedint0any integerRandom seed. Due to the randomized nature of the algorithms, changing this will produce slightly different results. If the TSNE results don't look good, try running multiple times with different seeds and pick the TSNE that looks best.
## Common Use Cases
These examples illustrate what you should put in your --params CSV file in some common situations.
### 1. More Principal Components and Clusters
For very large / diverse cell populations, the defaults may not capture the full variation between cells. In that case, try increasing the number of principal components and / or clusters. To run dimensionality reduction with 50 components and k-means with up to 30 clusters, put this in your CSV:
num_comps,50
max_clusters,30
### 2. Less Memory Usage
You can limit the memory usage of the analysis by computing the LSA projection on a subset of cells and features. This is especially useful for large datasets (100k+ cells). If you have 100k cells, it's completely reasonable to use only 50% of them for LSA - the memory usage will be cut in half, but you'll still be well equipped to detect rare subpopulations. Limiting the number of features will reduce memory even further. To compute the LSA projection using 50000 cells and 3000 peaks, put this in your CSV:
num_dr_bcs,50000
num_dr_features,3000
Note: Subsetting of cells is done randomly, to avoid bias. Subsetting of features is done by binning features by their mean expression across cells, then measuring the dispersion (a variance-like parameter) of each gene's expression normalized to the other features in its bin.
• 1.1
• 1.0
• Cell Ranger ATAC v1.2 (latest)
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## an error I just can't crack
Please discuss general Delphi programming topics here.
### an error I just can't crack
I am getting the following error.
"Types of actual and formal var parameters must be identical" I was wondering if someone would be able to comment on the error and help me out a bit more. I just can't seem to get this thing right.
MrNotTooSmartGuy
MrNotToSmartGuy
Active Member
Posts: 8
Joined: June 28th, 2007, 4:29 pm
simple yet rather hard to find.
let's say you have something like that:
Code: Select all
procedure surprise( var X: cardinal )
and then try something like:
Code: Select all
var Y: integer; begin surprise( Y ); end;
you'll get that error. you know why? in this example Y isn't cardinal.
what I did? hardcore types?
Last edited by Johnny_Bit on June 29th, 2007, 7:08 am, edited 1 time in total.
Thou shalt write the code, not connect the bricks.
Johnny_Bit
VIP Member
Posts: 455
Joined: June 15th, 2003, 9:56 am
In addition to what Johnny_Bit said, in the above example, calling surprise function with a constant parameter causes the same problem. It's because the parameter needs to be passed as reference and should be variable.
Kambiz
Kambiz
Posts: 2426
Joined: March 7th, 2003, 7:10 pm
Thanks guys for the help. The error was that it should have been passed by reference. It works now. Thanks
MrNotToSmartGuy
Active Member
Posts: 8
Joined: June 28th, 2007, 4:29 pm
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# proof of example of medial quasigroup
We shall proceed by first showing that the algebraic systems defined in the parent entry (http://planetmath.org/MedialQuasigroup) are quasigroups and then showing that the medial property is satisfied.
To show that the system is a quasigroup, we need to check the solubility of equations. Let $x$ and $y$ be two elements of $G$. Then, by definition of $\cdot$, the equation $x\cdot z=y$ is equivalent to
$f(x)+g(z)+c=y.$
This is equivalent to
$g(z)=y-c-f(x).$
Since $g$ is an automorphism, there will exist a unique solution $z$ to this equation.
Likewise, the equation $z\cdot x=y$ is equivalent to
$f(z)+g(x)+c=y$
which, in turn is equivalent to
$f(z)=y-c-g(x),$
so we may also find a unique $z$ such that $z\cdot x=y$. Hence, $(G,\cdot)$ is a quasigroup.
To check the medial property, we use the definition of $\cdot$ to conclude that
$\displaystyle(x\cdot y)\cdot(z\cdot w)$ $\displaystyle=$ $\displaystyle(f(x)+g(y)+c)\cdot(f(z)+g(w)+c)$ $\displaystyle=$ $\displaystyle f(f(x)+g(y)+c)+g(f(z)+g(w)+c)+c$
Since $f$ and $g$ are automorphisms and the group is commutative, this equals
$f(f(x))+f(g(y))+g(f(z))+g(g(w))+f(c)+g(c)+c.$
Since $f$ and $g$ commute this, in turn, equals
$f(f(x))+g(f(y))+f(g(z))+g(g(w))+f(c)+g(c)+c.$
Using the commutative and associative laws, we may regroup this expression as follows:
$(f(f(x))+f(g(z))+f(c))+(g(f(y))+g(g(w))+g(c))+c$
Because $f$ and $g$ are automorphisms, this equals
$f(f(x)+g(z)+c)+g(f(y)+g(w)+c)+c$
By defintion of $\cdot$, this equals
$f(x\cdot z)+g(y\cdot z)+c,$
which equals $(x\cdot z)\cdot(y\cdot z)$, so we have
$(x\cdot y)\cdot(z\cdot w)=(x\cdot z)\cdot(y\cdot z).$
Thus, the medial property is satisfied, so we have a medial quasigroup.
Title proof of example of medial quasigroup ProofOfExampleOfMedialQuasigroup 2013-03-22 16:27:35 2013-03-22 16:27:35 rspuzio (6075) rspuzio (6075) 8 rspuzio (6075) Proof msc 20N05
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# Greenhouse gases
A post (below) on the Bishop Hill blog relating to climate change asserts that no warming effect can be attributed to $\mathrm{CO_2}$. I don't know whether the author is really a physicist but it sounds impressive (Planck spectra and black-body radiation etc). Can someone explain in layman's language whether the assertions are valid.
There is no greenhouse, so it can't be reversed.
Many so-called skeptics are not really basing their arguments on the true
physics of the atmosphere. By failing to do so, they are demonstrating
that they also have fallen for the IPCC bluff that radiation from a cooler
can transfer thermal energy to a warmer surface.
This is not correct physics and the sooner this is made clear to the
public the better. True physics, backed up by basic phenomena such as the
fact that radiation in a microwave oven is not absorbed in the usual sense
of the word, shows why this is the case. No one has ever proved anything
to the contrary in any empirical experiment, and never will.
The only thing any such radiation from the atmosphere can do is slow down
that third or so of surface cooling which occurs by way of radiation that
does not escape to space via the atmospheric window. Radiation from the
atmosphere can have absolutely no effect on evaporative cooling, chemical
processes or sensible heat transfer. These non-radiative components plus
cooling. Furthermore, the effect of carbon dioxide with its limited
frequencies is far less than a true blackbody, and less per molecule than
water vapor. No gas can radiate outside its Planck spectrum (i.e. more than
a true blackbody) and so there is no way that carbon dioxide (1 in 2,500
molecules) can contribute a very large amount of radiation anyway.
The other cooling processes merely accelerate and compensate for any
minuscule slowing of radiative cooling. Thus there is absolutely no
warming attributable to carbon dioxide. It is time for skeptics to get
their facts right and stop giving in to part of the hoax. Only truth will
prevail in the long run.
EDIT: The author of the blog post was 'Doug Cotton', who has published a related paper at http://principia-scientific.org/publications/psi_radiated_energy.pdf and has a website at http://climate-change-theory.com/
-
If you want answers drawing from a credible source, we can have this migrated to Skeptics.SE.. – Manishearth Apr 8 '12 at 17:24
I imagined that a forum inhabited by physicists was the most credible source :-) The statements above seem so authoritative and are stated from the perspective of a physicist (apparently). Since physics is by and large a matter of fact not opinion, I wondered if the statements above are really fact or fiction. – William Morris Apr 8 '12 at 18:10
(1) we're not a forum. Beware, you may be banned for saying that ;-) (2) Yep, but climate change can get controversial, and IIRC opinion is divided on it, even within the physics community. And the opinion guides the fact that'sused :/ .Skeptics.SE would have given you a referenced answer--then again, it wouldn't be hard to find comtradictory scientific publications--and might look at it neutrally. – Manishearth Apr 8 '12 at 18:46
Oh come on, nobody gets banned for calling this site a forum ;-) (although of course we'd prefer you didn't). And welcome to Physics Stack Exchange, William! Like Terry said in his answer, kudos to you for asking for a review of the claim. – David Z Apr 8 '12 at 19:00
@manishearth: there really isn't any division or controversy over the basic facts of climate change. The idea that any controversy exists is purely a political fabrication. The details are certainly complex, but the fundamental rules of thermodynamics and absorption spectra have been settled science for over a century. – Colin K Apr 8 '12 at 19:14
The article you quoted frankly reads very poorly. It quotes a lot of stuff without once noting that greenhouse effects absolutely are real and critical to the earth being habitable. I don't know who this fellow is, but if he posted here directly I'd give it an instant negative vote.
You, sir, I'm giving a thumbs up for taking the trouble to ask in a forum where you are likely to get some answers. More people should do that when they hear odd science claims!
Now, with that said, it's absolutely true that both carbon dioxide and methane are bit players in the overall greenhouse effect.
The main greenhouse is water vapor, by about two orders of magnitude. My recollection without looking it up is that 97 to 98 percent of the greenhouse effect is caused by water vapor. This is why it gets so cold in the desert at night, for example.
The Nobel-prize winning models for global warming do not invoke direct warming from carbon dioxide. Instead, they postulate and model using computer programs the idea that the very small additive impacts of carbon dioxide, methane, and other minor greenhouse gases throw off the balance of the major player, water vapor. I do not know how they do that part of the model. It has to be complicated, since water vapor levels vary with near-fractal complexity from day to day and from region to region.
-
Thanks for the reply. I have added some references I found to other work by the blog post author. – William Morris Apr 8 '12 at 20:50
But certain geologists disagree on the fact that the present increase in global temerature is because of increase in greenhouse gases. They say that earth actually have a cycle of heat and ice ages. So, what we are seeing is actually those rather than an effect of greenhouse emission. – Vineet Menon Apr 9 '12 at 6:16
I have doubts about your numbers and corresponding picture you paint here. If we go by the most widely accepted IPCC scenarios and models, then the radiative forcing from CO2 alone contributes about 1 degree C. Although there are contributions from other gases, this is over half of the total anthropogenic forcing value. Then water vapor has the effect of increasing this to 5-7 degrees C. This corresponds to 700-800 ppm CO2 and can be verified with Wikipedia and 10 cells of calcs in Excel. Now, this is my conceptual picture and I think it conflicts with what you wrote. – Alan Rominger Apr 9 '12 at 13:19
Hey, Terry--- you're answer is good, +1, but the CO2 is not negligible, as AlanSE says. Could you modify it a bit? You can get rough estimates for CO2 impact from ice-core data, and they match observations from human-generated CO2, so the complicated models are not necessary. But they do give confidence in the projections of warming, and the location of the warming. – Ron Maimon Apr 13 '12 at 20:19
Ron, will do, I'm not happy with my lack of specs either. I've read papers that had specifics on relative roles and recall what they looked like, but I need to dig them up and find out the details. The ones I saw were not from the ice core data - those are absolutely fascinating for multiple reasons - but from a physical properties analysis. Sometime this week; I won't be happy myself until I can recover the specifics of what I was paraphrasing from memory. – Terry Bollinger Apr 16 '12 at 2:46
Let's look a bit closer at the claims of Doug Cotton, and of Claes Johnson, whose work Doug relies upon. It's important because this is one of the strongest claims made by those who choose to reject the notion of anthropogenic climate change.
Here's the core claim, from Doug Coton:
The assumption is made that so-called "backradiation" from a cold atmosphere is able to transfer thermal energy to a surface which is warmer than the source of the radiation. This is a physical impossibility as is proven theoretically by Prof Claes Johnson and empirically by Prof. Nasif Nahle
The claim, contradictory to over a century of thermodynamics, is that a body will only radiate heat towards bodies colder than it, and never towards bodies hotter than it. Note that this is not a claim about net heat transfer, but about any radiated heat.
Apparently, this happens through the following mechanism according to Professor Claes Johnson:
[a body] reads the temperature of the surrounding from its spectrum, and then decides to cool or warm depending on its own temperature
The Johnson/Cotton theory is that almost everyone other than them misinterprets the Stefan-Boltzmann Law, and that there is no such thing as photons of infra-red radiation.
And the problem with all of this is that this is an extraordinary claim that lacks any evidence at all. Thermodynamics, the theory of photons, and of black-body radiation, have all made astonishingly successful predictions, and are supported by many decades of empirical evidence.
-
Thanks. I'd also got the feeling from reading Cotton's paper that he is not to be taken seriously, but I don't have the theoretical background to contradict his claims. However, common sense leads me to think that the atmosphere will radiate in all directions, including towards the earth, whatever their relative temperatures, so his claim that the earth cannot be affected by the CO2 in the atmosphere is clearly nonsense. I've seen various discussions indicating that the anti-warming community rejects his thesis too. – William Morris Apr 9 '12 at 21:57
[a body] reads the temperature of the surrounding from its spectrum, and then decides to cool or warm depending on its own temperature'' Are we sure Professor Johnson isn't a comedian? – OSE Aug 15 '14 at 14:52
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# American Institute of Mathematical Sciences
March 2005, 4(1): 1-8. doi: 10.3934/cpaa.2005.4.1
## Regularity of solutions for a system of integral equations
1 Department of Mathematics, Yeshiva University, New York, NY 10033, United States 2 Department of Applied Mathematics, University of Colorado at Boulder, Boulder, CO 80309-0524
Received April 2004 Revised October 2004 Published December 2004
In this paper, we study positive solutions of the following system of integral equations in $R^n$:
$u(x) = \int_{R^{n}} |x-y|^{\alpha -n} v(y)^q dy$, $v(x) = \int_{R^{n}} |x-y|^{\alpha -n} u(y)^p dy$
with $\frac{1}{q+1}+\frac{1}{p+1}=\frac{n-\alpha}{n}$. In our previous paper, under the natural integrability conditions $u \in L^{p+1} (R^n)$ and $v \in L^{q+1} (R^n)$, we prove that all the solutions are radially symmetric and monotone decreasing about some point. In this paper, we go further to study the regularity of the solutions. We show that the solutions are bounded, and hence continuous and smooth. We also prove that if $p = q$, then $u = v$, and they both must assume the standard form
$c(\frac{t}{t^2 + |x - x_o|^2})^{(n-\alpha)/2}$
with some constant $c = c(n, \alpha)$, and for some $t > 0$ and $x_o \in R^n$.
Citation: Wenxiong Chen, Congming Li. Regularity of solutions for a system of integral equations. Communications on Pure & Applied Analysis, 2005, 4 (1) : 1-8. doi: 10.3934/cpaa.2005.4.1
[1] Wenxiong Chen, Chao Jin, Congming Li, Jisun Lim. Weighted Hardy-Littlewood-Sobolev inequalities and systems of integral equations. Conference Publications, 2005, 2005 (Special) : 164-172. doi: 10.3934/proc.2005.2005.164 [2] Ze Cheng, Genggeng Huang, Congming Li. On the Hardy-Littlewood-Sobolev type systems. Communications on Pure & Applied Analysis, 2016, 15 (6) : 2059-2074. doi: 10.3934/cpaa.2016027 [3] Yingshu Lü, Zhongxue Lü. Some properties of solutions to the weighted Hardy-Littlewood-Sobolev type integral system. Discrete & Continuous Dynamical Systems - A, 2016, 36 (7) : 3791-3810. doi: 10.3934/dcds.2016.36.3791 [4] Lorenzo D'Ambrosio, Enzo Mitidieri. Hardy-Littlewood-Sobolev systems and related Liouville theorems. Discrete & Continuous Dynamical Systems - S, 2014, 7 (4) : 653-671. doi: 10.3934/dcdss.2014.7.653 [5] Ze Cheng, Changfeng Gui, Yeyao Hu. Existence of solutions to the supercritical Hardy-Littlewood-Sobolev system with fractional Laplacians. Discrete & Continuous Dynamical Systems - A, 2019, 39 (3) : 1345-1358. doi: 10.3934/dcds.2019057 [6] Ze Cheng, Congming Li. An extended discrete Hardy-Littlewood-Sobolev inequality. Discrete & Continuous Dynamical Systems - A, 2014, 34 (5) : 1951-1959. doi: 10.3934/dcds.2014.34.1951 [7] Jingbo Dou, Ye Li. Classification of extremal functions to logarithmic Hardy-Littlewood-Sobolev inequality on the upper half space. Discrete & Continuous Dynamical Systems - A, 2018, 38 (8) : 3939-3953. doi: 10.3934/dcds.2018171 [8] Gui-Dong Li, Chun-Lei Tang. Existence of ground state solutions for Choquard equation involving the general upper critical Hardy-Littlewood-Sobolev nonlinear term. Communications on Pure & Applied Analysis, 2019, 18 (1) : 285-300. doi: 10.3934/cpaa.2019015 [9] Yutian Lei, Zhongxue Lü. Axisymmetry of locally bounded solutions to an Euler-Lagrange system of the weighted Hardy-Littlewood-Sobolev inequality. Discrete & Continuous Dynamical Systems - A, 2013, 33 (5) : 1987-2005. doi: 10.3934/dcds.2013.33.1987 [10] Yu Zheng, Carlos A. Santos, Zifei Shen, Minbo Yang. Least energy solutions for coupled hartree system with hardy-littlewood-sobolev critical exponents. Communications on Pure & Applied Analysis, 2020, 19 (1) : 329-369. doi: 10.3934/cpaa.2020018 [11] Hua Jin, Wenbin Liu, Huixing Zhang, Jianjun Zhang. Ground states of nonlinear fractional Choquard equations with Hardy-Littlewood-Sobolev critical growth. Communications on Pure & Applied Analysis, 2020, 19 (1) : 123-144. doi: 10.3934/cpaa.2020008 [12] Genggeng Huang, Congming Li, Ximing Yin. Existence of the maximizing pair for the discrete Hardy-Littlewood-Sobolev inequality. Discrete & Continuous Dynamical Systems - A, 2015, 35 (3) : 935-942. doi: 10.3934/dcds.2015.35.935 [13] Soohyun Bae. Classification of positive solutions of semilinear elliptic equations with Hardy term. Conference Publications, 2013, 2013 (special) : 31-39. doi: 10.3934/proc.2013.2013.31 [14] John Villavert. Sharp existence criteria for positive solutions of Hardy--Sobolev type systems. Communications on Pure & Applied Analysis, 2015, 14 (2) : 493-515. doi: 10.3934/cpaa.2015.14.493 [15] Wei Dai, Zhao Liu, Guozhen Lu. Hardy-Sobolev type integral systems with Dirichlet boundary conditions in a half space. Communications on Pure & Applied Analysis, 2017, 16 (4) : 1253-1264. doi: 10.3934/cpaa.2017061 [16] Yimin Zhang, Youjun Wang, Yaotian Shen. Solutions for quasilinear Schrödinger equations with critical Sobolev-Hardy exponents. Communications on Pure & Applied Analysis, 2011, 10 (4) : 1037-1054. doi: 10.3934/cpaa.2011.10.1037 [17] Xiaomei Sun, Wenyi Chen. Positive solutions for singular elliptic equations with critical Hardy-Sobolev exponent. Communications on Pure & Applied Analysis, 2011, 10 (2) : 527-540. doi: 10.3934/cpaa.2011.10.527 [18] Yinbin Deng, Qi Gao, Dandan Zhang. Nodal solutions for Laplace equations with critical Sobolev and Hardy exponents on $R^N$. Discrete & Continuous Dynamical Systems - A, 2007, 19 (1) : 211-233. doi: 10.3934/dcds.2007.19.211 [19] Wei Dai, Jiahui Huang, Yu Qin, Bo Wang, Yanqin Fang. Regularity and classification of solutions to static Hartree equations involving fractional Laplacians. Discrete & Continuous Dynamical Systems - A, 2019, 39 (3) : 1389-1403. doi: 10.3934/dcds.2018117 [20] Stathis Filippas, Luisa Moschini, Achilles Tertikas. Trace Hardy--Sobolev--Maz'ya inequalities for the half fractional Laplacian. Communications on Pure & Applied Analysis, 2015, 14 (2) : 373-382. doi: 10.3934/cpaa.2015.14.373
2018 Impact Factor: 0.925
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MathSciNet bibliographic data MR1459271 60G55 (60D05 60F05 60F17 60G60) Chiu, S. N.; Quine, M. P. Central limit theory for the number of seeds in a growth model in \$\bold R\sp d\$$\bold R\sp d$ with inhomogeneous Poisson arrivals. Ann. Appl. Probab. 7 (1997), no. 3, 802–814. Article
For users without a MathSciNet license , Relay Station allows linking from MR numbers in online mathematical literature directly to electronic journals and original articles. Subscribers receive the added value of full MathSciNet reviews.
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Cuboid and ratio
Cuboid has dimensions in ratio 1:2:6 and the surface area of the cuboid is 1000 dm2. Calculate the volume of the cuboid.
Result
V = 1500 dm3
Solution:
$V = abc \ \\ a:b:c = 1:2:6 \ \\ a = 1k \ \\ b = 2k \ \\ c = 6k \ \\ S = 1000 \ \\ S = 2(ab+bc+ac) \ \\ S = 2(2k^2+12k^2+6k^2) = 40 \ k^2 \ \\ k = \sqrt{ S/ 40 } = \sqrt{ 1000/ 40 } = 5 \ \\ a = k = 5 \ \\ b = 2 \cdot \ k = 2 \cdot \ 5 = 10 \ \\ c = 6 \cdot \ k = 6 \cdot \ 5 = 30 \ \\ V = a \cdot \ b \cdot \ c = 5 \cdot \ 10 \cdot \ 30 = 1500 = 1500 \ dm^3$
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# Restriction of a scheme morphism to a closed subset
I've been working through a proof of Chevalley's theorem for the special case of morphisms of finite type between Noetherian schemes as outlined in Görtz-Wedhorn Theorems 10.19 and 10.20 on page 248.
The claim of Theorem 10.19 is:
If $f:X\rightarrow Y$ is a dominant morphism of finite type between Noetherian schemes, then $f(X)$ contains a dense open subset of $Y$.
The first portion of the proof deals with the case where $Y$ is assumed to be irreducible, and everything seems clear to me there. However, it then continues into the case $Y$ is reducible by decomposing $Y = Y_1\cup\ldots\cup Y_n$ as a union of irreducible components (using that $Y$ is Noetherian) and then concludes by applying the previous case to the restricted morphisms $f^{-1}(Y_i)\rightarrow Y_i$. I'm concerned in that I seem to be unsure how these natural restricted maps should be defined!
It's clear to me how to define the restriction of a scheme morphism to an open set using the natural open subscheme structures for the open set and its inverse image. However, I don't see a good way to do this for closed subsets. If the schemes are affine, say $X = \text{Spec}(B)$, $Y = \text{Spec}(A)$, then if $Z\subseteq Y$ is closed, the scheme $\text{Spec}(A/a)$ would have the same underlying topological space as $Z$ for some ideal $a\subseteq A$. Then $f^{-1}(Z)$ would be the underlying topological space of the scheme $\text{Spec}(B/a^e)$, where $a^e$ is the extension of $a$ by the ring homomorphism corresponding to $f$. There is an induced ring homomorphism $A/a\rightarrow B/a^e$, which corresponds to a scheme morphism $\text{Spec}(B/a^e)\rightarrow \text{Spec}(A/a)$ compatible with $f$. However, I don't see why this morphism need be dominant.
Specifically, my questions are:
If $f:X\rightarrow Y$ is a scheme morphism, and $Z\subseteq Y$ a closed subset, is there a canonical way to define a restricted map $f^{-1}(Z)\rightarrow Z$? Can we do this using the reduced induced closed subscheme structures of $f^{-1}(Z), Z$? If so, what would the map of sheaves look like? Finally, if such a map is defined, is it dominant and of finite type so that the proof of the theorem may use it?
I apologize if these are silly questions; it feels that I'm missing something obvious. However, I haven't had any luck so far finding a reference describing this construction explicitly and as far as I can tell such restricted maps aren't mentioned earlier in G&W. This idea of restricting to a closed subset is also used in the proof of Theorem 10.20. Thanks very much!
• $f^{-1}(Z)$ is defined as $X\times_YZ$ and the natural morphism is $pr_2:X\times_YZ\to Z$. – Armando j18eos Jun 9 '17 at 13:53
• @Armandoj18eos Thanks! For some reason I wasn't thinking in terms of the fiber product. If I assume $f:X\rightarrow Y$ is of finite type between Noetherian schemes, I see how the same can be said for $pr_2$, and I think it is also straightforward to show that the dominance of $f$ implies that of $pr_2$ (using that these schemes are Noetherian). I would be happy to accept your comment as an answer! – catfish Jun 10 '17 at 17:18
By definition $f^{-1}(Z)=X\times_YZ$ and $g=f_{|f^{-1}(Z)}$ is the natural projection $pr_2:X\times_YZ\to Z$; because for any $x\in X,\,f_x^{\sharp}:\mathcal{O}_{Y,f(x)}\to\mathcal{O}_{X,x}$ is a morphism of finite type of local Noetherian rings, by base change $\forall x\in f^{-1}(Z),\,g_z^{\sharp}=f_x^{\sharp}\otimes Id_{\displaystyle\mathcal{O}_{Y,f(x)/\mathcal{I}_{Z,f(x)}}}$ and it is a morphism of finite type: by definition $g$ is a morphism of finite type of (Noetherian) schemes.
By Noetherian hypothesys, one can assume that $Z$ is irreducible; by this lemma: $g$ is a dominant morphism if and only if the inverse image of generic point $\eta$ of $Z$ via $g$ is not empty.
If $g$ is not dominant then $g^{-1}(\eta)=\emptyset\iff\eta\notin g(g^{-1}(Z))\Rightarrow\eta\notin\overline{g(g^{-1}(Z))}$, that is there exists an open neighbourhood $U$ of $\eta$ such that $g^{-1}(U)=\emptyset$; by construction, there exists an open subset $V$ of $Y$ such that $U=V\cap Z$ and $\emptyset=g^{-1}(U)=f^{-1}(U)=f^{-1}(V\cap Z)=f^{-1}(V)\cap f^{-1}(Z)\Rightarrow f^{-1}(V)=\emptyset$: by dominance of $f$ this is a contradiction, then $g$ is dominat.
• Thank you! One concern I have though: it doesn't seem to be the case that the projection need be surjective. Indeed if $Z$ isn't contained in $f(X)$ ($f$ need not be surjective), then certainly $g$ won't be surjective right? However if $Y$ is Noetherian with a minimal decomposition into irreducible components $Y = Y_1\cup\ldots\cup Y_n$, and if $Z= Y_1$ for example, then for any open subset $U\subseteq Z$ one can construct a nonempty open subset of $Y$ contained in $U$ using $Y\setminus (Y_2\cup\ldots\cup Y_n)$, and so the density of $f(X)$ in $Y$ guarantees that of $g(f^{-1}(Z))$ in $Z$. – catfish Jun 12 '17 at 3:03
• Yes, you are right: $g$ needs not be surjective. The dominant morphisms are particular topological maps: you can use the Noetherian hypothesys and pass to irreducible case and apply the lemma. – Armando j18eos Jun 12 '17 at 9:12
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# Tag Info
Suppose that you are riskless asset with return $r_{ft}$ and a risky asset with return $r_t$ and conditional volatility $\sigma_t(r_t) := \sqrt{V_t(r_t)}$. We build a portfolio using weights $(w_1, w_2) \in \mathbb{R}$, or as you wrote it $w_t := w_{1t}$, $w_{2t} := 1 - w_t$. This portfolio will have a time $t$ return of $r_{pt}$. Its volatility is given by $... 0 I have just found out what the code is. Note that theta and delta come from the copula selected for you through the BiCopSelect() command. theta <- selectedCopula$par delta <- selectedCopula$par2 gfBB1 <- gofCopula(BB1Copula(c(theta, delta)), as.matrix(mydata), N = 50) 1 Note that Boyle (1988) introduces$\lambda$because the CRR parameterisation$u=e^{\sigma\sqrt{h}}$yielded negative probabilities (and probabilities above one) for reasonable parameter values. Instead, he uses$u=e^{\lambda\sigma\sqrt{h}}$, where$\lambda>1$and$h=\frac{T}{n}$is the length of one time step. If you perform the limits,$p_u\to0$and$...
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# Of example matrix moment inertia
## MomentInertia.html York University
Moment of inertia Revolvy. Chapter 9 rigid body motion in 3d moment of inertia about an axis passing through the the scalar moment of inertia can be found by simple matrix, chapter 10 rigid bodies 10.1 moments of inertia is the inertia tensor at a. this matrix relationship example: what is the moment of inertia of a flat circular.
### Moment of Inertia Lecture Notes Physics - Docsity
Capsule Moment Of Inertia Math and Physics - GameDev.net. Dynamics example: inertia tensor of an eccentric rectangular prism x y z l h w a ixx = zh 0 zl 0 zw 0 the moments of inertia look like: ai zz = cmi zz +m(r2 x, dynamics example: inertia tensor of an eccentric rectangular prism x y z l h w a ixx = zh 0 zl 0 zw 0 the moments of inertia look like: ai zz = cmi zz +m(r2 x.
Axis and izz mass moment inertia about the z axis and this of these two examples, this inertia property matrix is called a second-order tensor and in this structural dynamics lecture 5 outline of lecture 5 mass matrix., mass moment of inertia of rotor and generator rotor,
5/05/2010в в· inertia everday examples w/ (matrix reloaded soundtrack - fluke - zion) the matrix reloaded: how does changing the moment of inertia affect angular the three-moment equation for continuous-beam analysis moments of inertia, we can write a matrix representation of the three-moment equation for arbi-
Chapter 10 rigid bodies 10.1 moments of inertia is the inertia tensor at a. this matrix relationship example: what is the moment of inertia of a flat circular i don't have an actual question however i would like know and understand how to calculate the principal moment of inertia of a mass. what is the principal moment of
An inertia tensor with three equal moments of inertia on the the following matrix gives the inertia tensor properties of inertia tensors. the inertia moment of inertia moment of inertia is the rotational analogue to mass. the mass moment of inertia about a fixed axis is the property of a body that measures the body
End-effector moment of inertia calculation example. calculation example : when calculating the moment of inertia of a complicated shape, divide it into simple parts momentofinertia[reg] computes the moment of inertia matrix for the region reg relative to computes the moment of inertia matrix relative to the examples open
### Inertia Tensors Vortex
Moment of inertia Revolvy. In physics and applied mathematics, the mass moment of inertia, usually denoted by i, measures the extent to which an object resists rotational acceleration about a, 5/05/2010в в· inertia everday examples w/ (matrix reloaded soundtrack - fluke - zion) the matrix reloaded: how does changing the moment of inertia affect angular.
Principal Axes of Rotation CCRMA. Ellipsoid moment of inertia matrix. ask question. as i understand it, the inertia matrix acts just like mass in that it counteracts the torque (for example,, the moment of inertia , while for spatial movement the same calculations yield a 3 г— 3 matrix of moments of inertia, example calculation of moment of inertia..
### 183_notesexamplesthe_moment_of_inertia_of_a_bicycle
Why is inertia tensor called a tensor as opposed to matrix. 19/07/2014в в· we take a brief look at rotational inertia as something more complex than a simple number. we illustrate the role of the inertia tensor in stable rotation > so given a generalised inertia matrix, the values of о» are the eigenvalues, which are the principle moments of inertia. examples:.
• Composite Body Example bˆ Virginia Tech
• Definition of moment of inertia matrix Angular Momentum
• Moment-of-Inertia Formulas DENSO Robotics
• The second column of the stiп¬ђness matrix is the set of forces and moments beam element stiп¬ђness matrices 9 example 1 250; % moments of inertia >> l1 structural dynamics lecture 5 outline of lecture 5 mass matrix., mass moment of inertia of rotor and generator rotor,
Mass moment of inertia tensor. as derived in the previous section, the moment of inertia tensor, in 3d cartesian coordinates, is a three-by-three matrix that can be the moment of inertia iu of a solid body v rotating about an axis through the example. think about an suppose we have brought the symmetric 3г—3 matrix a to
Example: the inertia tensor for a cube. we wish to compute the inertia tensor for a uniform density cube of mass and side . the density is simply . moment of inertia tensor the product of inertia, the product of inertia, etc. the matrix of the values is known as the moment of inertia tensor.
24/09/2014в в· the inertia matrix is useful when you are rotating in 3d and not necessarily along an axis of in your capsule example, capsule moment of inertia chapter 9 rigid body motion in 3d moment of inertia about an axis passing through the the scalar moment of inertia can be found by simple matrix
The moment of inertia iu of a solid body v rotating about an axis through the example. think about an suppose we have brought the symmetric 3г—3 matrix a to the (symmetric) matrix representing the inertia tensor of a collection of masses, $m_i$, with positions $(x_i, y_i, z_i)$ relative to their centre of mass is\begin
The (symmetric) matrix representing the inertia tensor of a collection of masses, $m_i$, with positions $(x_i, y_i, z_i)$ relative to their centre of mass is\begin what is the product of inertia? for example, consider a thin what is the difference between the product of inertia and moment of inertia?
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# Dimensional analysis
1. Aug 28, 2012
### therealDR.DOG
Dimensional analysis....
I am having a real hard time wrapping my head around dimensional analysis. Can someone please explain it in english? Thanks.
2. Aug 28, 2012
### Dickfore
Re: Dimensional analysis....
Every physical quantity f has dimensions ([f]) w.r.t. the seven base physical quantities:
• time T
• length L
• mass M
• electric current I
• thermodynamic temperature $\mathrm{\Theta}$
• amount of substance N
• luminous intensity J
Luminous intensity is a photometric quantity. Its unit is the candela (cd). It is a subjective measure of how the human eye perceives light. If one is concerned with objective measures of radiation fluxes, then this unit is not used.
Amount of substance is directly proportional to the number of elementary entities in the ensemble. The unit is called a mole. The actual number of particles present in a mole of substance is considered a physical constant, although I would think that it makes more sense to call it a conversion factor. It is the Avogadro's constant:
$$N_A = 6.022 \times 10^{23} \, \mathrm{mol}^{-1}$$
Similarly, due to developments in Statistical Physics, it had been shown that temperature is directly proportional to some energy ("thermal energy"). The unit of thermodynamic temperature is kelvin (K), whereas the unit of energy is joule (J). A conversion factor that converts any temperature (T) into energy units ($\theta = k_B \, T$) is the Boltzmann's constant:
$$k_B = 1.3806 \times 10^{-23} \, \frac{\mathrm{J}}{\mathrm{K}}$$
The above two constants combine to give another famous constant - the Universal gas constant:
$$R = k_B \, N_A = 8.314 \, \frac{\mathrm{J}}{\mathrm{K} \cdot \mathrm{mol}}$$
The unit of electric current is the ampere (A). If you look at its definition, it is defined through the force (a mechanical quantity) between two long straight conductors with given length, and a certain distance apart (both mechanical quantitites). Thus, there must be a conversion factor between mechanical quantities (time, length, and mass), and the electric quantitiy. Indeed, there is such a conversion factor, called the vacuum permeability:
$$\mu_0 = 4\pi \times 10^{-7} \, \frac{\mathrm{N}}{\mathrm{A}^2}$$
Thus, in principle, all quantities have dimension only w.r.t. to the three mechanical base units:
$$[f] = \mathrm{T}^{\tau} \, \mathrm{L}^{\lambda} \, \mathrm{M}^{\mu}$$
The exponents (the τ, λ, and μ, which are pure rational numbers) are the corresponding dimensions w.r.t. to each base quantity.
Some rules for dimensions are:
• A dimensionless quantity has zero dimension w.r.t. each base physical quantity $[f] = \mathrm{T}^0 \, \mathrm{L}^0 \, \mathrm{M}^0 = 1$.
• Both sides of an equality have the same dimension, i.e. $f = g \Rightarrow [f] = [g]$
• You may only add (or subtract) quantities with the same dimension, i.e. $h = f \pm g \Leftrightarrow [f] = [g] = [h]$.
• The dimension of a product (quotient) of two physical quantites is he product of their respective dimensions, i.e. $[f \cdot g] = [f] \cdot [g]$ (the exponents for each base quantity add (subtract).
• A mathematical function (exp, log, sin, cos, etc.) accepts a dimensionless argument and returns a dimensionless result, i.e. $y = f(x), \Rightarrow [x] = [y] = 1$.
Last edited: Aug 28, 2012
3. Aug 28, 2012
### Jakeus314
A short and simple explanation? Break down the units of some quantities, cancel some units if possible, and make some kind of comparison of the units. Don't let the word dimensional scare you. Just think "do the units make sense?"
4. Aug 28, 2012
### Dickfore
Re: Dimensional analysis....
Example:
Let us look at the following formula:
$$v = v_0 + a \, t$$
according to the summation rule, we know that we must have:
$$[v] = [v_0] = [a \, t]$$
Further, according to the product rule, we also have:
$$[a \, t] = [a] \cdot [t]$$
Thus, if we want to express the dimension of a, we would have:
$$[a] = \frac{[v]}{[t]}$$
5. Aug 29, 2012
### therealDR.DOG
Re: Dimensional analysis....
its just weird because for kinematics I am having a way easier time then the majority of the homework in chapter one which involves alot more than just changing units.
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## Contents
The rules for adding binary numbers are similar to the rules for adding decimal numbers. When adding two decimal numbers such as
2 3 6 5 8
+ 4 1 2 4 8
_________
a series of rules are followed. First, a table of all possible two-digit sums of two decimal numbers must be known:
0 + 0 ____ 0 0 + 1 ____ 1 0 + 2 ____ 2 0 + 3 ____ 3 ... 9 + 9 ____ 18
The algorithm is:
• Add the numbers in the right-most column using the table of all possible sums.
• If the sum is one digit, write the sum at the bottom of the first column.
• If the sum is two digits, write down the right-most digit of the sum at the bottom of the first column and put the left-most digit of the sum on the top of the column to the left of the first column. If there is no column to the left, write down this number to the left of the last number written down.
• Repeat the above process for the next column.
For example,
1
2 3 6 5 8
+ 4 1 2 4 8
_________
6
• Add the numbers in the first column: 8 + 8 = 16.
• Is the sum one digit? No.
• Is the sum two digits? Yes. Place the right digit on the bottom of the first column and the left digit in the next column to the left of the first column.
As with decimal numbers, we need a list of all possible sums of two binary numbers to refer to. They are
0 + 0 ____ 0 0 + 1 ____ 1 1 + 0 ____ 1 1 1 + 1 ____ 1 0
Note that we arrived at the result
1
+ 1
____
1 0
in binary by using the same rule that we use when we when we run out of symbols when counting in decimal. The last possible decimal symbol is 9, and to represent the next larger number, we place a zero in the right-most column and a one in the column to the left:
1
1
+ 9
___
1 0
In the case of binary numbers, to get the next value after the last possible binary symbol (1), we place a zero in the first column and a one in the second column: 1 0. (Another way of arriving at this result is to note that the binary representation of the decimal number 2 is 10.)
This algorithm can be applied to the addition of numbers in any base. For example, in base 3, the possible symbols are 0, 1, and 2. Using this rule, we arrive at 2+1 = 10 in base 3.
Example
Perform the following addition in binary:
1 0 1 1 1
+ 0 0 1 0 1
_________
The numbers in the first column are added (1+1 = 10 in binary) and the carry-over part is placed at the top of the next column:
1
1 0 1 1 1
+ 0 0 1 0 1
_________
0
The same is done for the second column:
1 1
1 0 1 1 1
+ 0 0 1 0 1
_________
0 0
The recipe given earlier only mentions adding two numbers, not three. To determine the sum of three 1s in binary, break the sum of three numbers into a sum of two numbers:
1
1 1 0 (result of adding the top two 1s)
+ 1 => + 0 1 (bottom 1 with a leading zero added for clarity)
__ _____
1 1
1 0 1 1 0
+ 0 0 1 1 1
_________
1 1 1 0 1
To check your answer, convert the binary numbers to decimal numbers and do the addition in decimal.
• The top row 10110 equals 22 in decimal (determined using the table method covered in the Binary Representation of Numbers).
• The second row 00111 equals 7 in decimal (determined using the table method).
• 22 + 7 = 29
• The binary answer of 11101 equals 29 in decimal (determined using the table method).
1 0 1 1 0 (22 in decimal)
+ 0 0 1 1 1 (7 in decimal)
_________
1 1 1 0 1 (29 in decimal)
# 3. Problems
## 3.1. Running Out of Digits
1. What is the binary representation of the number that follows the binary number 111?
2. What is the decimal representation of the number that follows the decimal number 999?
## 3.2. Running Out of Digits
The hexadecimal number system uses the 16 symbols 0, ..., 9, A, ..., F, where A-F correspond to the decimal numbers 10-15.
• What is the hexadecimal representation of the number that follows F?
• What is the hexadecimal representation of the number that follows the number given for your answer to the previous problem?
## 3.3. Carry Operations
Y 1 1
1 0 1 1 0
+ 0 0 1 1 1
_________
X 1 0 1
What are X and Y?
1 0 0 0 1 1 0 1 1 0 1
+ 1 1 1 0 0 1 1 0 1 1 1
_____________________
0 1 1 0 1
+ 1 0 0 1 1
___________
1
1
+ 1
___________
1 0 1 1 1 1 0 1 1 0 0
0 0 1 0 1 1 0 1 1 0 1
+ 1 1 1 0 0 1 1 0 1 1 1
_____________________
For a hint, look at the following activity:
1. Write out the table of all possible sums of the symbols 0, ..., 9, A, ..., F.
2. Use the table to complete the following base-16 addition.
0 B 3
+ 0 2 F
________
# 4. Activities
## 4.1. Extending the Addition Algorithm
Compute the following and write down any additional steps that you needed to add to the steps covered previously. Check your answer using the method covered previously. 1 1 1 1 1 1 + 1 1 ____
## 4.2. Base 2 Multiplication
1. Create a table of all possible products of the symbols 0 and 1.
2. Use the table to complete the base-2 multiplication:
1 1
x 1 1
____
1. Write out the table of all possible sums of the symbols 0, 1, and 2.
2. Use the table to complete the base-3 addition:
0 1 2
+ 0 2 0
________
1. Write out the table of all possible sums of the symbols 0, 1, 2, and 3.
2. Use the table to complete the base-4 addition:
0 3 3
+ 0 2 0
________
1. Write out the table of all possible sums of the symbols 0, ..., 9, A, ..., F.
2. Use the table to complete the base-16 addition:
0 A F
+ 0 2 F
________
# 5. Resources
• "A study of mathematical concepts for the elementary education major using tactile models and appropriate technology" [3]
• Using a template-like method to determine if a credit card number is valid [4].
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# Generalizations of “standard” calculus
We have the usual analogy between infinitesimal calculus (integrals and derivatives) and finite calculus (sums and forward differences), and also the generalization of infinitesimal calculus to fractional calculus (which allows for real and even complex powers of the differential operator). Have people worked on a "fractional finite" calculus, where instead of a differintegral we had some sort of "differsum"? I don't know much about it, but I was thinking maybe the answer might come from umbral calculus?
To give a motivating example/special case for this question: the Wikipedia article on fractional calculus uses the example of the $\frac{1}{2}$th derivative, which when applied twice gives the standard derivative. What is the operator $D$ on sequences such that, when applied twice, it gives the forward difference of the original sequence?
Also, I have perhaps a related question: The solution to $\frac{d}{dx}f=f$ is $f=e^x$, while the solution to $\Delta f = f$ is $f=2^x$. Is the fact that $e$ is close to 2 a coincidence, or is there something connecting these results? Is there more generally some sort of spectrum of calculi lying between "finite" and "infinitesimal" each with its own "$e$"?
EDIT: After looking around some more I found time scales, which are pretty much what I was thinking of in the second part of my question (though many of the answers people have provided are along the same general lines). I'm surprised I don't hear more about this in analysis - unifying discrete and continuous should make it a pretty fundamental concept!
-
@EDIT. If that's what you're after then you might look into what are called "Hybrid Systems". For example, see the work of André Platzer @ symbolaris.com. There is also the literature on Qualitative Reasoning and Qualitative Simulation, for example, the work of Ben Kuipers @ cs.utexas.edu/~kuipers. – Jon Awbrey Dec 25 '09 at 4:50
I don't know if you have seen this but there are papers devoted to "discrete fractional calculus". Like this one for example http://arxiv.org/abs/0911.3370 or http://www.math.u-szeged.hu/ejqtde/sped1/103.pdf . Like in fractional calculus, of course the discrete fractional integral is easier to define than the discrete fractional derivative.
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Thanks for the links! Looks like exactly what I was thinking of. – Zev Chonoles Dec 23 '09 at 22:02
I can answer your last question, at least. The derivative acts as a shift operator on Taylor series, so the operator $\frac{d}{dx} - 1$ acts as the forward difference on Taylor series. So their eigenvectors are basically the same; the eigenvectors of the derivative are the exponential functions $e^{\lambda x}$, which have Taylor coefficients $a_n = \lambda^n$, and these are the eigenvectors of the forward difference. I'll think about your other questions.
Edit: Here's a possible way to get a notion of "fractional forward difference." If we write the forward difference operator $\Delta f(n) = f(n+1) - f(n)$ as $D - 1$ where $D$ is the shift operator, it follows that
$\displaystyle \Delta^k f(n) = (D - 1)^k f(n) = \sum_{i=0}^{k} {k \choose i} (-1)^{k-i} f(n+i)$
by the binomial theorem. So a possible extension to non-integer values of $k$ is to use the generalized binomial theorem formally in the above expansion. Unfortunately, the above sum is then infinite and therefore not guaranteed to converge. I'm not really sure how useful or interesting this is.
Edit 2: Well, that doesn't work for a stupid reason; $\sqrt{D - 1}$ doesn't have a Taylor series expansion at $0$. However, the backward difference operator $\nabla f(n) = f(n) - f(n-1)$ can be written as $1 - E$ where $E$ is the other shift operator and $(1 - E)^k$ has a Taylor series expansion for every $k \in \mathbb{C}$. (Note in particular the case $k = -1$.)
-
Hmm. Why doesn't $\sqrt{D-1}$ have a Taylor series at $0$? As long as you are willing to consider complex numbers (and why wouldn't you?!), $\sqrt{D-1}=i\sqrt{1-E}$ :) – Mariano Suárez-Alvarez Dec 23 '09 at 13:43
The $E$ should be a $D$, of course... (comments should be editable!) – Mariano Suárez-Alvarez Dec 23 '09 at 13:44
This could be an answer for your last question: if you define $\frac{\Delta_t}{t}$ as $\frac{f(x+t)-f(x)}{t}$ for $t>0$ and you solve $\frac{\Delta_t}{t}(f)=f$ you obtain the solution $$f(x)=\left((1+t)^{\frac{1}{t}}\right)^x.$$ So for the operator $\Delta_1(f)=f(x+1)-f(x)$ the solution is $2^x$, and as $t\rightarrow 0$ the solution tends to $e^x$.
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Part of what makes the exponential function so special is that it's the eigenfunction of a differential operator. When we solve the equation $\frac{df}{dx} = E f$ we are saying that f is an eigenfunction of $\frac{d}{dx}$ with eigenvalue E. The spectrum, in this case, is the whole real line.
If we solve the equation f(n+1) - f(n) = k f(n), with f(0) = 1. Then we have f(n+1) = (k+1)f(n), so $f(n) = (k+1)^n$. In your case, let $k = 2$.
One more example to think about is the quantum harmonic oscillator which looks for eigenfunctions of $H = \frac{d^2}{dx^2} - x^2$. However, we get the factorization $\left( \frac{d}{dx} - x \right)\left(\frac{d}{dx} + x \right) = a_- a_+$. The eigenfunction of $a_-$ is $e^{-x^2/2}$ and I will leave it as an exercise to show $H[e^{-x^2/2}] = 0$ and that $(a_+)^k[ e^{-x^2/2}]$ is an eigenfunction of H for all k.
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I realize this question was posted a while ago, but I would like to make a note on your edit stating,
After looking around some more I found time scales, which are pretty much what I was thinking of in the second part of my question (though many of the answers people have provided are along the same general lines). I'm surprised I don't hear more about this in analysis - unifying discrete and continuous should make it a pretty fundamental concept!
Time scale calculus is fairly new development. It came about in 1989 in Hilger's Ph.D. thesis (he initially called it a measure chain). At the time of writing his thesis, mathematicians did not embrace his idea. Then, in the early 90s, the ideas were brought to the U.S. and now there are papers being written about time scale all over the world. However, I suppose there are still some mathematicians who are not studying/teaching time scale.
If you are looking for resources on this, you might consider taking a look at [1].
Furthermore, I see above that you are trying to define the exponential function for "discrete(difference) calculus" (if I am understanding your posting correctly).
Note that for the continuous case, we have that $(e^{at})^{'}=ae^{at}$
Now, consider $\Delta (1+ \alpha)^{t} = (1+ \alpha)^{t+1} - (1 + \alpha)^{t}= (1+\alpha)(1+\alpha)^{t}- (1+\alpha)^{t} = ((1+\alpha)-1)(1+\alpha)^{t}=\alpha(1+\alpha)^{t}$.
Thus, the discrete exponential should actually be $(1+ \alpha)^{t}$.
[2] is a good resource for discrete calculus.
Also, [1] discusses exponentials in time scale. There is a delta and nabla exponential form. You may consider checking that out.
Now, to your fractional calculus question, I believe I recall my professor mentioning some problem with fractional calculus and time scale. I cannot remember what it was exactly, but it was an open problem regarding fractional calculus. (Note: There are many open problems in time scale.)
I hope this helps!
[1] Bohner, M. & Peterson, A. (2001). Dynamic Equations on Time Scales: An Introduction with Applicaitons. Boston, MA: Birkhäuser.
[2] Kelley, W. & Peterson, A. (2001). Difference Equations: An Introduction with Applications (2nd Ed.). San Diego, CA: Academic Press.
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Just to draw the attention of the curious reader to take a look at the book titled "Discrete Calculus by Analogy" witten by Izadi, Aliev, and Bagirev to see the differences as well as similirities between Discrete Calculs and Continous one.
-
Taking the point of view that the binary domain $\mathbb{B} = \lbrace 0, 1 \rbrace$ is more general than the real domain $\mathbb{R}$, and cranking (if you'll excuse the expression) all the analogies in sight, we find ourselves in the wonderland of Differential Logic, where plus and minus are the same operation, playing the devil with our usual suspicions about the diff between differential and integral calculus. So $\exists\sum\operatorname{fun}$ to be had with that.
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# 'MPI' has not been declared
31 posts / 0 new
'MPI' has not been declared
#1
Hello,
I have built the MPI binaries many times without issue... until now. I have two machines with the same Ubuntu build, openmpi, and site.settings file on them. The build goes fine on one, but fails on the other (I did the openmpi installation tests and they succeed).
In the build output I see: "'MPI' has not been declared". Below is more of the output... thank you very much in advance for your time!
src/protocols/mpi_refinement/MPI_Refine_Master.cc: In member function 'virtual void protocols::mpi_refinement::MPI_Refine_Master::init()':
src/protocols/mpi_refinement/MPI_Refine_Master.cc:204:15: error: 'MPI' has not been declared
int ncores = MPI::COMM_WORLD.Get_size();
^
.....
scons: *** [build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/protocols/mpi_refinement/MPI_Refine_Master.os] Error 1
scons: building terminated because of errors."
Category:
Post Situation:
Wed, 2016-09-21 07:49
starone
What does "which mpicc" return? What do the scons lines look like (the ones that probably start with mpicc)? The individual scons lines should show paths to libraries - are the mpi libraries showing up like they should? (You can determine "should" by comparison to the machine that works).
I assume the problem is that whatever the system is finding as MPI libraries aren't right, if they don't define MPI. (I assume if it wasn't finding the libraries at all, it would complain that the library files weren't found).
It compiles fine without MPI, right?
Wed, 2016-09-21 07:57
smlewis
Thank you!
"which mpicc" returns: "/home/starone/openmpi/bin/mpicc"
Here is an individual line:
"mpiCC -o build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/protocols/mpi_refinement/MPI_Refine_Master.os -c -std=c++98 -ffor-scope -isystem external/boost_1_55_0/ -isystem external/ -isystem external/include/ -isystem external/dbio/ -pipe -Wall -Wextra -pedantic -Werror -Wno-long-long -Wno-strict-aliasing -march=core2 -mtune=generic -O3 -ffast-math -funroll-loops -finline-functions -finline-limit=20000 -s -Wno-unused-variable -Wno-unused-parameter -fPIC -DBOOST_ERROR_CODE_HEADER_ONLY -DBOOST_SYSTEM_NO_DEPRECATED -DBOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS -DPTR_BOOST -DNDEBUG -DUSEMPI -Isrc -Iexternal/include -Isrc/platform/linux/64/gcc/5.4 -Isrc/platform/linux/64/gcc -Isrc/platform/linux/64 -Isrc/platform/linux -Iexternal/boost_1_55_0 -Iexternal/libxml2/include -Iexternal -Iexternal/dbio -I/usr/include -I/usr/local/include src/protocols/mpi_refinement/MPI_Refine_Master.cc"
Yes, it builds fine without MPI.
Wed, 2016-09-21 08:20
starone
Update, fixed:
I started looking through threads and found the following are needed... the machine I had the error on was a clean install of the OS so they were missing:
sudo apt-get install libopenmpi-dev
I also needed:
sudo apt-get install zlib1g-dev
Are these things always necessary?
Wed, 2016-09-21 10:46
starone
You will always need to install MPI to compile in MPI. libopenmpi-dev is the stuff that gets #included, which is why you got those MPI not defiend errors. I am updating the build documentation to clarify you do need the -dev package here.
You will always need zlib support for Rosetta. zlib1g-dev is the usual ubuntu package that's necessary (and it's not usually present on ubuntu; it varies by system). That's the only thing we consider an external dependency other than "a compiler". (The feature this buys you is that Rosetta can basically always interpret gzipped inputs natively, and can optionally output many things as .gz as well). Usually a missing zlib is exposed by "cannot find -lz", explained in the build documentation (https://www.rosettacommons.org/docs/latest/build_documentation/Build-Documentation#setting-up-rosetta-3_dependencies-troubleshooting)
Wed, 2016-09-21 11:27
smlewis
Great! Thanks for the info and the update to the docs.
I actually thought I was in good shape because I saw no errors, but I also don't see any .mpi executables... : ( I'll have to look into that tonight and tomorrow.
Wed, 2016-09-28 18:38
starone
Actually the standard binaries built (not sure what I messed up)... the MPI versions did not. The error is the same "MPI has not been declared".
I thought maybe something went wrong with the libdev install so I ran it again but it appears to be fine unless I'm misinterpreting the following... so where else am I missing something?
"sudo apt-get install libopenmpi-dev
Reading package lists... Done
Building dependency tree
Reading state information... Done
libopenmpi-dev is already the newest version (1.10.2-8ubuntu1).
The following packages were automatically installed and are no longer required:
libpango1.0-0 libpangox-1.0-0 linux-headers-4.4.0-21 linux-headers-4.4.0-21-generic linux-headers-4.4.0-24 linux-headers-4.4.0-24-generic
linux-image-4.4.0-21-generic linux-image-4.4.0-24-generic linux-image-extra-4.4.0-21-generic linux-image-extra-4.4.0-24-generic
Use 'sudo apt autoremove' to remove them.
0 upgraded, 0 newly installed, 0 to remove and 29 not upgraded."
Thanks!
Wed, 2016-09-28 18:56
starone
On my VM here on my laptop, it builds fine… I noticed this difference between the build statements, but I don’t know why the path is missing from the build statement on my workstation... ($LD_LIBRARY_PATH and$PATH are set the same way on both machines)
Laptop:
“mpiCC -o build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/AnchoredDesign.mpi.linuxgccrelease -Wl,-rpath=/home/starone/Public/Rosetta/main/source/build/src/release/linux/4.4/64/x86/gcc/5.4/mpi -Wl,-rpath=/home/starone/Public/Rosetta/main/source/build/external/release/linux/4.4/64/x86/gcc/5.4/mpi -Wl,-rpath=\$ORIGIN -Wl,-rpath=\$ORIGIN/../lib build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/apps/public/interface_design/anchored_design/AnchoredDesign.o -Lexternal/lib -Lbuild/src/release/linux/4.4/64/x86/gcc/5.4/mpi -Lsrc -Lbuild/external/release/linux/4.4/64/x86/gcc/5.4/mpi -Lexternal -L/home/starone/openmpi/lib -L/home/starone/Public/PyRosetta.Namespace -L/home/starone/Public/PyRosetta.Namespace/rosetta -L/usr/lib -L/usr/local/lib -ldevel -lprotocols.7 -lprotocols.6 -lprotocols_e.5 -lprotocols_d.5 -lprotocols_c.5 -lprotocols_b.5 -lprotocols_a.5 -lprotocols_h.4 -lprotocols_g.4 -lprotocols_f.4 -lprotocols_e.4 -lprotocols_d.4 -lprotocols_c.4 -lprotocols_b.4 -lprotocols_a.4 -lprotocols.3 -lprotocols_b.2 -lprotocols_a.2 -lprotocols.1 -lcore.5 -lcore.4 -lcore.3 -lcore.2 -lcore.1 -lbasic -lnumeric -lutility -lObjexxFCL -lz -lcppdb -lsqlite3 -lcifparse….”
Workstation: (-L/home/starone/openmpi/lib is missing)
“mpiCC -o build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/protocols/mpi_refinement/MPI_Refine_Master.os -c -std=c++98 -ffor-scope -isystem external/boost_1_55_0/ -isystem external/ -isystem external/include/ -isystem external/dbio/ -pipe -Wall -Wextra -pedantic -Werror -Wno-long-long -Wno-strict-aliasing -march=core2 -mtune=generic -O3 -ffast-math -funroll-loops -finline-functions -finline-limit=20000 -s -Wno-unused-variable -Wno-unused-parameter -fPIC -DBOOST_ERROR_CODE_HEADER_ONLY -DBOOST_SYSTEM_NO_DEPRECATED -DBOOST_MATH_NO_LONG_DOUBLE_MATH_FUNCTIONS -DPTR_BOOST -DNDEBUG -DUSEMPI -Isrc -Iexternal/include -Isrc/platform/linux/64/gcc/5.4 -Isrc/platform/linux/64/gcc -Isrc/platform/linux/64 -Isrc/platform/linux -Iexternal/boost_1_55_0 -Iexternal/libxml2/include -Iexternal -Iexternal/dbio -I/usr/include -I/usr/local/include src/protocols/mpi_refinement/MPI_Refine_Master.cc”
Thu, 2016-09-29 06:23
starone
The first thing to try when there are apparent pathing issues is to ln -s site.settings.killdevil site.settings. This adds some of your enviroment variables into SCons in a different way. (Those files are in source/tools/build).
Thu, 2016-09-29 07:24
smlewis
I tried the step you suggested (thank you!), but nothing changed. One thing that is striking is the difference in the parameters... on my laptop I see "-L" parameters indicated which include all the elements of the LD LIBRARY PATH... they aren't present on the workstation complie option list.
Why would this be?
Thu, 2016-09-29 10:12
starone
I'm surprised that the site.settings change did nothing - usually it forces a full recompile. (I guess if it wasn't compiling before that's not noticeable).
Does the workstation have something unusual set up w/r/t the shell you are calling scons from versus the default shell for your user account? Perhaps the environment variables don't exist in the scons environment if they aren't being set in your .zshrc or whatever? (I'm guessing here.)
Thu, 2016-09-29 10:52
smlewis
I'm not a Linux person so I just accept whatever is installed when I installed the OS on the machines, the only changes I made were in the .bashrc files regarding the paths. They are both Intel machines.
This is what I added to that file: (sorry for the strange characters... hopefully you can figure it out. I must be inadvertantly hitting on some escape characters or something)
source /home/starone/Public/PyRosetta.Namespace/SetPyRosettaEnvironment.sh
export PATH=/opt/ncbi-blast-2.3.0+/bin:$PATH export BLASTDB=/opt/ncbi-blast-2.3.0+/db export PATH=/opt/blast-2.2.26/bin:$PATH
export PATH=$HOME/openmpi/bin:$PATH
export LD_LIBRARY_PATH=$HOME/openmpi/lib:$LD_LIBRARY_PATH
These are the contents of the site.settings file I have been using on both machines:
import os
settings = {
"site" : {
"prepends" : {
"program_path" : os.environ["PATH"].split(":"),
"library_path" : os.environ["LD_LIBRARY_PATH"].split(":"),
},
"appends" : {
},
"overrides" : {
},
"removes" : {
},
},
}
Thu, 2016-09-29 11:05
starone
The SetPyRosettaEnvironment.sh shouldn't do anything with respect to an MPI compile - that just sets things up for PyRosetta, and the compilation of commandline Rosetta is completely separate from it.
Just to confirm, the error message you're getting is still the same as the one at the top of this thread, right? The "error: 'MPI' has not been declared" in MPI_Refine_Master.cc (or similar), right?
If that's the case, that's a header issue, and not a library issue -- the -L settings and the LD_LIBRARY_PATH shouldn't affect that. I'd focus more on the "-I" settings for the include path. (One complication here is that you showed a linker commandline for the laptop compile, but a compile commandline for the workstation - that's why you see the -L's in one but not in the other.)
My initial guess would be that the path to the MPI includes is missing. That'd be a little odd, though, as you would expect that you'd get a different error in that case. But it might be an issue of *where* the MPI libraries you're using are located.
If you're using the Ubuntu system libopenmpi, then it looks like the headers should be (for Xenial) in /usr/lib/openmpi/include/ It doesn't look like you have that enabled. I'm not sure where it's pulling the mpi.hh from, though: probably not from where you expect it. Try adding
"include_path" : ["/usr/lib/openmpi/include/", ],
To the "prepends" section of your site.settings file and recompiling.
I'm not sure why it's working on your laptop, though, if you're using the same packages. Perhaps because you did a manual install of the library in /home/starone/openmpi/ and it's pulling from that. (If you do want to use the manually installed version rather than the system version, you'll need to change the paths.)
Thu, 2016-09-29 12:09
rmoretti
yes, same error
Thu, 2016-09-29 18:56
starone
Ok... I think I see what you are getting at. I will try it in the morning.
(sorry if there is and I just don't know about it): I haven't been an engineer for many years, but when I have to build something in Linux I always wonder why there isn't something slick like MS's Visual Studio. I did Microsoft development for a long time before moving into management and the ability to visualize things from within a development studio is so much more helpful to me than using command line interactions... feel like I'm back in the MS-DOS era : )
Thanks again for your help!
Thu, 2016-09-29 18:56
starone
Progress! Well, the compilation looks like its succeeding now, but the linking is failing... pretty much as expected I suppose. I think you're right that I used different methods for installing openmpi (I installed on the laptop a while ago), but it wasn't by choice. There is a good deal of conflicting info on the web on this stuff as I'm sure you know. On the workstation I downloaded the package from the OpenMPI website and followed the steps in the YouTube video linked there.
I noticed that there are about 80 items in openmpi/lib directory on my laptop, but only about 20 on the workstation.
I documented the steps I followed... appearently they are incorrect, can you tell me the proper method.
1. Download the latest stable build tar.gz
2. Make directory Public/openmpi
3. Copy the compressed file to the directory
4. Open a terminal window
5. Change to the openmpi directory
6. Execute: ./configure --prefix=$HOME/openmpi 7. Execute: make all 8. Execute: make install 9. Change to your home directory 10. Execute: sudo gedit .bashrc 11. Add the following lines to the end of the file: export PATH=$HOME/openmpi/bin:$PATH export LD_LIBRARY_PATH=$HOME/openmpi/lib:$LD_LIBRARY_PATH 12. Save and close the editor 13. Execute: mpirun -np n hostname (where 'n' is the number of processors in your machine) These are the errors I'm getting now: mpiCC -o build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/per_residue_energies.mpi.linuxgccrelease -Wl,-rpath=/home/starone/Public/Rosetta/main/source/build/src/release/linux/4.4/64/x86/gcc/5.4/mpi -Wl,-rpath=/home/starone/Public/Rosetta/main/source/build/external/release/linux/4.4/64/x86/gcc/5.4/mpi -Wl,-rpath=\$ORIGIN -Wl,-rpath=\$ORIGIN/../lib build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/apps/public/analysis/per_residue_energies.o -Lexternal/lib -Lbuild/src/release/linux/4.4/64/x86/gcc/5.4/mpi -Lsrc -Lbuild/external/release/linux/4.4/64/x86/gcc/5.4/mpi -Lexternal -L/home/starone/Public/PyRosetta.Namespace -L/home/starone/Public/PyRosetta.Namespace/rosetta -L/home/starone/openmpi/lib -L/usr/lib -L/usr/local/lib -ldevel -lprotocols.7 -lprotocols.6 -lprotocols_e.5 -lprotocols_d.5 -lprotocols_c.5 -lprotocols_b.5 -lprotocols_a.5 -lprotocols_h.4 -lprotocols_g.4 -lprotocols_f.4 -lprotocols_e.4 -lprotocols_d.4 -lprotocols_c.4 -lprotocols_b.4 -lprotocols_a.4 -lprotocols.3 -lprotocols_b.2 -lprotocols_a.2 -lprotocols.1 -lcore.5 -lcore.4 -lcore.3 -lcore.2 -lcore.1 -lbasic -lnumeric -lutility -lObjexxFCL -lz -lcppdb -lsqlite3 -lcifparse -lxml2 build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.3.so: undefined reference to ompi_mpi_cxx_op_intercept' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.3.so: undefined reference to MPI::Win::Free()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.3.so: undefined reference to MPI::Datatype::Free()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.6.so: undefined reference to MPI::COMM_WORLD' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.3.so: undefined reference to MPI::Comm::Comm()' collect2: error: ld returned 1 exit status scons: *** [build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/helix_from_sequence.mpi.linuxgccrelease] Error 1 build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/apps/public/design/pmut_scan_parallel.o: In function MPI::Op::Init(void (*)(void const*, void*, int, MPI::Datatype const&), bool)': pmut_scan_parallel.cc:(.text._ZN3MPI2Op4InitEPFvPKvPviRKNS_8DatatypeEEb[_ZN3MPI2Op4InitEPFvPKvPviRKNS_8DatatypeEEb]+0x17): undefined reference to ompi_mpi_cxx_op_intercept' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/apps/public/design/pmut_scan_parallel.o: In function MPI::Intracomm::Clone() const': pmut_scan_parallel.cc:(.text._ZNK3MPI9Intracomm5CloneEv[_ZNK3MPI9Intracomm5CloneEv]+0x3a): undefined reference to MPI::Comm::Comm()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/apps/public/design/pmut_scan_parallel.o: In function MPI::Graphcomm::Clone() const': pmut_scan_parallel.cc:(.text._ZNK3MPI9Graphcomm5CloneEv[_ZNK3MPI9Graphcomm5CloneEv]+0x35): undefined reference to MPI::Comm::Comm()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/apps/public/design/pmut_scan_parallel.o: In function MPI::Cartcomm::Sub(bool const*) const': pmut_scan_parallel.cc:(.text._ZNK3MPI8Cartcomm3SubEPKb[_ZNK3MPI8Cartcomm3SubEPKb]+0x194): undefined reference to MPI::Comm::Comm()' Fri, 2016-09-30 05:58 starone Wait, why are we talking about manually installed openmpi? I thought you installed it via apt? "sudo apt-get install openmpi openmpi-dev" or something similar? Fri, 2016-09-30 07:39 smlewis Not on the workstation... I followed those steps because when I tried sudo apt-get install openmpi I think I remember it saying it wasn't found. I found a page today that indicates that I have to use 'sudo apt-get install openmpi-bin'... is that right? Fri, 2016-09-30 07:46 starone I can't tell you what's right; I haven't installed MPI on linux in years. What you just said is similar to what I suggested so it's worth trying. You'll want the -dev package too, remember. You should be able to do something like "apt list | grep mpi" on the machine that works to see which mpi packages you installed, and just do the same on the other machine...? Fri, 2016-09-30 08:59 smlewis Thanks! I'll give it a try Fri, 2016-09-30 09:35 starone I'd definitely recommend using the system versions (the one from apt-get) if you can. MPI is a little bit finicky at times, and it's a lot easier if you leave setting things up properly to people who know the operating system well, rather than trying to get things set up appropriately yourself. In fact, if you continue to have issues, I'd recommend removing/uninstalling the manually installed version, to make sure that having two versions of the MPI libraries aren't confusing things. (You can get issues if Rosetta is picking up the headers of one and the libraries from the other.) Fri, 2016-09-30 09:56 rmoretti I tried using sudo apt-get... it just reports that the packages are already installed. These errors are different than I was getting before... now I'm seeing alot of this: scons: *** [build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/beta_peptide_modeling.mpi.linuxgccrelease] Error 1 build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libutility.so: undefined reference to ompi_mpi_cxx_op_intercept' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libutility.so: undefined reference to MPI::Datatype::Free()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libutility.so: undefined reference to MPI::Comm::Comm()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libutility.so: undefined reference to MPI::Win::Free()' collect2: error: ld returned 1 exit status scons: *** [build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/antibody.mpi.linuxgccrelease] Error 1 build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.1.so: undefined reference to ompi_mpi_cxx_op_intercept' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.1.so: undefined reference to MPI::Win::Free()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.1.so: undefined reference to MPI::Datatype::Free()' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.6.so: undefined reference to MPI::COMM_WORLD' build/src/release/linux/4.4/64/x86/gcc/5.4/mpi/libprotocols.1.so: undefined reference to MPI::Comm::Comm()' collect2: error: ld returned 1 exit status Fri, 2016-09-30 10:09 starone Okay, *now* you're getting issues with your -L settings. The killdevil settings should have fixed this, but you might have to supplement this with the openmpi location "library_path" : os.environ["LD_LIBRARY_PATH"].split(":") + ["/usr/lib/openmpi/lib/",], If that works for compilation, in order to run things successfully, you may need to actually add /usr/lib/openmpi/lib/ to your LD_LIBRARY path export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/usr/lib/openmpi/lib/
You can do this either any time you need to run MPI, or you could add it to your .bashrc to have it on permanently.
Sat, 2016-10-01 11:26
rmoretti
Thank you! I will give that a try in the morning.
One odd thing I noticed is that on my laptop there are about 79 items in the openmpi bin folder but on the workstation there are less than half that number. I looked at the build lines and openmpi is one of the -L options.
I will try what you suggested but I was hoping for your thoughts on the differening file counts... maybe the path is correct but the libraries are missing somehow?
Sun, 2016-10-02 18:36
starone
Are these both apt-get installed packages? Or are you comparing a manual install to the apt-get install?
I would not be surprised if the apt-get install is smaller (or larger). The people who do the Ubuntu packaging probably know which files are required and which are extra, and remove anything that is not really necessary for general Ubuntu usage. (Or alternatively, there may be multiple ways to do the build, and the Ubuntu packagers do all of them, as they don't know which ones would really be needed for your particular use case.)
Mon, 2016-10-03 10:54
rmoretti
On the workstation (problem machine) I first did a manual install using the steps listed in #16 above that I found in a video linked from the openmpi website. The generated fewer files. On my laptop I did the apt-get method there are more files and everything works fine.
Sorry I didn't get to try your suggestion as I woke up this morning feeling horrible and went back to bed after the kids were off to school. Hopefully I'll be feeling better tomorrow so I can have at it.
Mon, 2016-10-03 19:05
starone
Thanks, but no changes...
Ok, as I see it I have one machine where the build process can find, for example, "MPI::COMM_WORLD" and another on which it can't. Both machines have the same OpenMPI package installed and both have the same library paths defined.
So, what I'd like to do is find out from which library file, on the machine where the build works, exports "MPI::COMM_WORLD". This way I can see if it exists on the machine where it wont build.
Tue, 2016-10-04 07:21
starone
Maybe this explains something?
Both machines are running Ubuntu 16.04, but my laptop (where everthing builds fine) was an upgrade, while I did a clean install on my workstation (where the build fails). Everything else between the machines in terms of software, shells, settings, etc, are the same.
Wed, 2016-10-05 06:15
starone
Does anyone know about installing OpenMPI? I ran 'ompi_info' on both machines and the installation options and version info are different. I attached both files for review.
CatalayseU: Laptop, build successful
SynthaseU: Workstation, build fails
Thank you!!
File attachments:
Wed, 2016-10-05 06:43
starone
Could this "C++ bindings: no" be the problem?
If it is, does anyone know how to change it and rebuild?
Thanks
Wed, 2016-10-05 06:59
starone
Ok, looks like this is what happened... The C++ bindings are off by default when building OpenMPI (though I can't imagine why!). So I redid the build with this added to the ./configure command: "--enable-mpi-cxx".
Then I redid the remaining steps as I outlined above. I then did the MPI build of Rosetta and it was successful.
How do I mark this as answered?
Thanks for your help guys.
Wed, 2016-10-05 07:26
starone
|
{}
|
# Algorithm to add all lucky numbers under [N] to a Vector
A lucky number is defined as a positive integer whose decimal representation contains only the lucky digits 4 and 7. For example, numbers 47, 744, 4 are lucky and 5, 17, 467 are not. I need to check if a given number is evenly divisible by any lucky number or not.
Now, suppose I want to add all Lucky Numbers under a given integer [N] to a vector, without using recursion. For the sake of simplicity, let N = 1000.
I came up with an approach to just check each digit of all the numbers under [N] by making separate loops for 1 digit numbers, 2 digit numbers etc.
for(int number=0;number<10;number++) {if(((number%10==4)||(number%10==7))) {lucky.push_back(number);}} //1 Digit Lucky Numbers
for(int number=10;number<100;number++) {if(((number%10==4)||(number%10==7))&&(((number/10)%10==7)||((number/10)%10==4))) {lucky.push_back(number);}} //2 Digit Lucky Numbers
for(int number=100;number<1000;number++) {if(((number%10==4)||(number%10==7))&&(((number/10)%10==7)||((number/10)%10==4))&&(((number/100)%10==7)||((number/100)%10==4))) {lucky.push_back(number);}} //3 Digit Lucky Numbers
for(int number=10;number<100;number++) {if(((number%10==4)||(number%10==7))&&(((number/10)%10==7)||((number/10)%10==4))&&(((number/100)%10==7)||((number/100)%10==4))&&(((number/1000)%10==7)||((number/1000)%10==4))) {lucky.push_back(number);}} //4 Digit Lucky Numbers
I was thinking that this could roughly be converted to something along these lines but I am not quite able to come up with what exactly to do.
for(number;number<10*itr_counter;number++)
{
if(((number%10*itr_counter==4)||(number%10*itr_counter==7))) {lucky.push_back(number);}
itr_counter*=10;
}
I basically want to check each digit of all 1 digit numbers by taking modulo 10 and checking if the digits are 4 or 7. Similarly for a number consisting of X digits, I am taking modulo and dividing the number by 10, 100 and so on to check against 4 or 7.
Can someone help me optimise the first block of code into something smaller and more efficient? Something along the lines of the second block of code would work.
The Program
#include <bits/stdc++.h>
using namespace std;
int main()
{
int in_num;
cin>>in_num;
//This Part Needs to be Optimised
vector<int>lucky;
for(int number=0;number<10;number++) {if(((number%10==4)||(number%10==7))) {lucky.push_back(number);}} //1 Digit Lucky Numbers
for(int number=10;number<100;number++) {if(((number%10==4)||(number%10==7))&&(((number/10)%10==7)||((number/10)%10==4))) {lucky.push_back(number);}} //2 Digit Lucky Numbers
for(int number=100;number<1000;number++) {if(((number%10==4)||(number%10==7))&&(((number/10)%10==7)||((number/10)%10==4))&&(((number/100)%10==7)||((number/100)%10==4))) {lucky.push_back(number);}} //3 Digit Lucky Numbers
for(int number=10;number<100;number++) {if(((number%10==4)||(number%10==7))&&(((number/10)%10==7)||((number/10)%10==4))&&(((number/100)%10==7)||((number/100)%10==4))&&(((number/1000)%10==7)||((number/1000)%10==4))) {lucky.push_back(number);}} //4 Digit Lucky Numbers
//This Part Needs to be Optimised
int flag=0;
for(unsigned int index=0;index<lucky.size();index++)
{
if(in_num%lucky[index]==0) {flag=1; break;}
}
if(flag==1) {cout<<"YES";}
else {cout<<"NO";}
return 0;
}
It is fairly straightforward to generate a vector with all the values. First, you should treat all the same length numbers as a group. The values 4 and 7 would be in a singledigit vector. To get the twodigit vector, simply go through the previous vector, multiplying each by 10 and then adding 4 to push back a value and add 7 to push back another value.
vector<int> lucky;
vector<int> current;
vector<int> next;
current.push_back(4);
current.push_back(7);
lucky.push_back(4);
lucky.push_back(7);
int value=0;
while(value < N)
{
for(unsigned int i=0;i<current.size();++i)
{
value=current[i]*10+4;
next.push_back(value);
lucky.push_back(value);
value=current[i]*10+7;
next.push_back(value);
lucky.push_back(value);
}
current=next;
next.clear();
}
• I would only use a single vector, but otherwise good work. – Deduplicator Nov 13 '15 at 0:19
1. Consider adopting any of the common styles for code-formatting.
2. #include <bits/stdc++.h> is a bad idea, sharply limiting portability ad increasing compile-times. See: How does #include <bits/stdc++.h> work in C++?
Just include those headers you need, which are <vector> and <iostream>.
3. You are courting conflicting symbols and general bafflement with any minor change of your toolchain. See: Why is using namespace std; considered bad practice?
4. You are using the popular for-if-antipattern. See Introducing the for-if anti-pattern
Why don't you just enumerate the ones you are actually interested in?
5. A for-range-loop is simpler than explicitly using iterators/indices. Unless you actually need them.
6. In the end you don't actually want that whole list, only whether one of them divides your input-number. So why store them at all, and why also those bigger than the input-number?
7. return 0; is implicit for main in C++.
Doing it as it should be done, with recursion on coliru:
#include <stdio.h>
int luckydiv_helper(long in, long num, int free) {
return !free
? !(in % num)
: luckydiv_helper(in, 10 * num + 4, free - 1)
|| luckydiv_helper(in, 10 * num + 7, free - 1);
}
int luckydiv(long in) {
long abort = in;
for(int digits = 1; abort; digits++, abort /= 10)
if(luckydiv_helper(in, 0, digits))
return 1;
return !in;
}
int main() {
long in;
if(scanf("%ld", &in) != 1 || in < -999999999 || in > 999999999) {
fprintf(stderr, "You didn't enter a number between -999999999 and "
"+999999999. Aborting.\n");
// A long can represent all 9-digit decimal numbers.
return 1;
}
printf("%ld ", in);
if(in < 0) in = -in;
puts(luckydiv(in) ? "YES" : "NO");
}
A way to efficiently get all "lucky" numbers without recursion:
#include <limits>
#include <vector>
template<class T> std::vector<T> luckyvector() {
std::vector<T> v = {4, 7};
const auto limit4 = (std::numeric_limits<T>::max() - 4) / 10;
const auto limit7 = (std::numeric_limits<T>::max() - 7) / 10;
T x;
for(size_t i = 0; (x = v[i]) <= limit7; i++) {
v.push_back(x * 10 + 4);
v.push_back(x * 10 + 7);
}
if(x <= limit4)
v.push_pack(x * 10 + 4);
return v;
}
• You used recursion in luckydiv_helper(), and the task forbids recursion. – 200_success Nov 13 '15 at 0:52
• @200_success: I gave a way to do the task the program solves efficiently with recursion, yes. And a way to just generate a vector with all those numbers, without recursion. Clarified what is what. – Deduplicator Nov 13 '15 at 1:06
#include <iostream>
#include <vector>
bool is_lucky(int check_num)
{
while(check_num!=0)
{
if((check_num%10!=4)&&(check_num%10!=7))
{
return false;
}
check_num/=10;
}
return true;
}
int main()
{
std::vector <long long> lucky;
for(int in_num=1;in_num<1000;in_num++)
{
if(is_lucky(in_num))
{
lucky.push_back(in_num);
}
}
}
Even though I am still using the for-if anti-pattern as Deduplicator pointed out, I was finally able to make the is_lucky function which maybe less efficient and a lesser intelligent way to do it than the other ones posted, seems to be the shortest way to do the task.
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### Consecutive Numbers
An investigation involving adding and subtracting sets of consecutive numbers. Lots to find out, lots to explore.
### Calendar Capers
Choose any three by three square of dates on a calendar page...
### Days and Dates
Investigate how you can work out what day of the week your birthday will be on next year, and the year after...
# Pyramidal N-gon
##### Stage: 3 Short Challenge Level:
The base of the pyramid has $n$ edges, so also has $n$ vertices around the base. This then means that there are $n$ edges around the base (in red) of the pyramid and $n$ that meet at the apex (in black).
This means there are $2n$ edges in total.
There are also $n$ faces that meet at the apex of the pyramid, and one more for the base, so a total of $n+1$ faces.
Therefore the difference is $2n - (n+1) = n-1$.
This problem is taken from the UKMT Mathematical Challenges.
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Grading some assignments the other day on the syntax and semantics of “unless”, I was pretty astounded by the range of intuitions students had about what the truth table for “$\alpha$ unless $\beta$” should be. I got nearly every one of the 16 possibilities. OK, maybe not that many. But there was one common “mistake” among the range of answers, which I’d like to discuss.
Take, for example, the following sentence.
Floyd will go buy beer unless it's snowing outside.
Suppose I uttered this sentence several hours ago, and now we want to evaluate the truth of the utterance. There are four cases to consider.
1. Floyd went and bought beer, and it was snowing outside.
2. Floyd did not go and buy beer, and it was snowing outside.
3. Floyd went and bought beer, and it was not snowing outside.
4. Floyd did not go and buy beer, and it was not snowing outside.
The received wisdom is that the only case in which my utterance was false is case 4, in which both subclauses of my utterance are false. In every other case, what I uttered has held true.
While most students got cases 2-4 correct, case 1 really tripped up a lot of students. They said my utterance would be false in such a case. That’s because when I say that Floyd will go buy beer unless it’s snowing outside, it’s natural to infer that he’ll go only unless it’s snowing, which is just an ungrammatical way of saying that he’ll go only if it’s not snowing. That is, if it is snowing, he won’t go.
But this inference—that if it’s snowing outside, Floyd won’t go buy beer—seems really to just be a very strong implicature, as it can be cancelled.
Floyd will go buy beer unless it's snowing outside... in which case, I'm
not sure if he'll go or not.
Floyd will go buy beer unless it's snowing outside. And even then/in that
case, he'll still probably go!
With these continuations added, it’s no longer natural to infer that if it’s snowing, Floyd won’t go, unless of course the listener has some special knowledge that I/the speaker lacks.
If we consider this inference to be just an implicature and not part of the truth-conditional content of “unless”, then case 1 results in my utterance being true, and the truth table for “$\alpha$ unless $\beta$” turns out, in fact, to be exactly the same as that of $\alpha \lor \beta$, which is also the same as $\lnot\beta \to \alpha$.1
What’s interesting is that, several days later, the students were very reluctant to buy my implicature story.2 It was only after I really fleshed out the scenario that some of them relented; and even then, others still found the “…in which case” follow-ups unnatural.
But this strong inference associated with “unless” is not unique to “unless”. We see it with “if”, too—which is expected, I suppose, if “$\alpha$ unless $\beta$” is semantically equivalent to “if it’s not the case that $\beta$, then $\alpha$”. Suppose, for example, that I utter the following sentence.
Floyd will go buy beer if it's not snowing.
Even here, it’s natural to infer that Floyd will go buy beer only if it’s not snowing. That is, if it is snowing, then he won’t go (which is precisely what I wrote above for the “unless” utterance).
Again, though, this inference can be cancelled.
Floyd will go buy beer if it's not snowing. And even if it is snowing,
he'll still probably go!
The additional inference associated with “if” has been called conditional perfection because it completes (or perfects) the conditional by making it a biconditional: Floyd will go buy beer if and only if it’s not snowing outside.3 In symbols: $b \leftrightarrow \lnot s$ (mnemonic: $b =$ “beer”, $s =$ “snow”).
The same could be said of the “unless” utterance, if “only unless” were grammatical: Floyd will go buy beer unless and only unless it’s snowing. In symbols (assuming that “$\alpha$ unless $\beta$” means $\lnot\beta \to \alpha$): $\lnot s \leftrightarrow b$.
They are identical. My experience, however, is that students don’t have that much trouble with “if”, so why is “unless” so confusing? Is it the added negation? I have to admit that before I started grading, it took me a good several minutes to remind myself what “unless” is, or is supposed to, mean.
Bonus question: If “unless” is semantically equivalent to logical “or”, then is the added inference associated with “unless”, which turns it into exclusive “or”, derived in the same way as the inference that, under normal circumstances, makes “or” be interpreted exclusively? Or is it just a coincidence that these two expressions, which both share a truth table with $\lor$ but differ in that one is a subordinator and the other a coordinator, both happen to be regularly strengthened into an exclusive interpretation?
1. If the implication is taken to be part of the truth conditions of “unless”, i.e., not as an implicature, then the truth table is the same as that of exclusive “or”.
2. And no, it’s not because they were arguing for points. At least, I don’t think so.
3. Geis, Michael L. and Arnold M. Zwicky. 1971. On Invited Inferences. Linguistic Inquiry 2: 561-6. The term was suggested to the authors by Lauri Karttunen.
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## 15.55 a
Meghna2A
Posts: 32
Joined: Fri Sep 29, 2017 7:06 am
### 15.55 a
(a) For a reaction with a very large equilibrium constant, the rate constant of
the forward reaction is much larger than the rate constant of the reverse reaction. Why?
rkusampudi
Posts: 58
Joined: Fri Sep 29, 2017 7:04 am
### Re: 15.55 a
A large equilibrium constant means that the products are favored.
Deborah Cheng 1F
Posts: 50
Joined: Thu Jul 13, 2017 3:00 am
### Re: 15.55 a
K>1 means that products are favored, K<1 means the reactants are favored. Rate constant and equilibrium constant are proportional so when the equilibrium constant is large, rate constant of forward reaction is also large.
ConnorThomas2E
Posts: 57
Joined: Fri Sep 29, 2017 7:04 am
### Re: 15.55 a
As said before, the rate constant is always proportional to K. Therefore, when K is very large, meaning the products are favored, you will have a large rate constant.
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# Past Year CBSE Board Paper
2017 Class 10 Math Set 3 Q29. Quadratic Equation
#### Video Explanation
Let A take ‘a’ days to finish the work.
Let B take ‘b’ days to finish the work.
A takes 6 days lesser than B to do a work i.e., a = b – 6 ........... (1)
Together, they finish the work in 4 days. So, in one day they will complete $$frac{1}{4}$ of the work. In one day, A will complete $\frac{1}{a}$ of the work. In one day, B will complete $\frac{1}{b}$ of the work. Together they will complete$ ${$frac {1} {a}+\frac {1} {b}}$) of the work in one day. Therefore, $\frac{1}{a}$ + $\frac{1}{b}$ = $\frac{1}{4}$ ...........$2)
Substitute (a = b – 6) in equation (2)
So, $$frac{1}{b - 6}$+ $\frac{1}{b}$ = $\frac{1}{4}$ $\frac{b + b - 6}{$b - 6$b}) = $$frac{1}{4}$ Cross multiplying the denominators we get 4$2b – 6) = (b – 6)b
8b – 24 = b2 – 6b
b2 – 14b + 24 = 0
Factorize b2 – 14b + 24 = 0
b2 – 12b – 2b + 24 = 0
(b – 12)(b – 2) = 0
Or b = 12 or b = 2
If b = 2, a = b – 6 = 2 – 6 = -4
Number of days cannot be negative. So, b cannot be 2.
The only value that b takes is 12. i.e., B takes 12 days to finish the work.
.
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# Why are campaign finance laws administered by the Federal Election Commission (FEC) not well enforced?
###### Question:
Why are campaign finance laws administered by the Federal Election Commission (FEC) not well enforced?
### Aracel Engineering completed the following transactions in the month of June. a. Jenna Aracel, the owner, invested $100,000 cash, office equipment with a value of$5,000, and $60,000 of drafting equipment to launch the company. b. The company purchased land worth$49,000 for an office by paying $6,300 cash and signing a long-term note payable for$42,700. c. The company purchased a portable building with $55,000 cash and moved it onto the land acquired. d. The company paid$3,000 cash for the pr
Aracel Engineering completed the following transactions in the month of June. a. Jenna Aracel, the owner, invested $100,000 cash, office equipment with a value of$5,000, and $60,000 of drafting equipment to launch the company. b. The company purchased land worth$49,000 for an office by paying \$6,3...
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### I. Choose the best answer by crossing a, b, c or d ! Number one : Edo : I will take part in the story telling competition next week. Lina : Oh, That's good news. I hope you will do your best and get the first prize. Edo : Thank you Lina. ...........Lina : Sure. A. I will support you. B. Wish you happy forever. C. Please come to see the competition. D. Wish me luck.Number two :Dayu : "who won the football match yesterday? "Udin : "Our team did. we won two to one."Dayu : "well done. _________."Ud
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### 2+3=83+7=274+5=325+8=606+7=727+8=??
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### 4. In this section, Arn is struggling between his core beliefs and what he is being asked to do. Comment on the change and struggle that Arn is having within himself.
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### *65 POINTS* Upon which estate in France did the government depend for its income?
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### On Monday, Duncan skateboard shop received its first shipment of skateboards. Duncan sold 12 skateboards that day. On Thursday, he sold 9 skateboards. On Friday, he received a shipment of 30 more skateboards and sold 10 skate boards. He then had a total of 32 skateboards in a shop. How many skateboards were delivered on Monday?
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### PT 2 OF THE 1ST PROBLEM. PLS HELP IM BEGGING YOU!!!!
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### Find the percentage decrease if a players batting average dropped from 0.273 to 0.265 in one season.
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### Read the excerpt from Act II of Hamlet. Ophelia: Alas! my lord, I have been so affrighted. Polonius: With what, in the name of God? Ophelia: My lord, as I was sewing in my closet, Lord Hamlet, with his doublet all unbrac'd; No hat upon his head; his stockings foul'd, Ungarter'd, and down-gyved to his ancle; Pale as his shirt; his knees knocking each other; And with a look so piteous in purport As if he had been loosed out of hell To speak of horrors, he comes before me. What is the most likely r
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Based on your location, we recommend that you select: . Use the poly function to obtain a polynomial from its roots: p = poly(r).The poly function is the inverse of the roots function.. Use the fzero function to find the roots of nonlinear equations. You can also select a web site from the following list: Select the China site (in Chinese or English) for best site performance. MATLAB ® represents polynomials with numeric vectors containing the polynomial coefficients ordered by descending power. In algebra, given a polynomial = + + + ⋯ +,with coefficients from an arbitrary field, its reciprocal polynomial or reflected polynomial, denoted by p ∗ or p R, is the polynomial ∗ = + − + ⋯ + = (−). Polynomials are equations of a single variable with nonnegative integer exponents. A restriction of the polynomial is a new function, with one of those intervals as its domain, whose values agree with the values of the polynomial on that interval. The inverse of a quadratic function is a square root function. For example, to calculate the roots of our polynomial p, type − MATLAB executes the above statements and returns the following result − The function polyis an inverse of the roots function and returns to the polynomial coefficients. It is well known that checking the feasibility of a system of polynomial equations is NP-hard in general. They arise naturally in linear algebra as the characteristic polynomial of the inverse of a matrix. If f contains more than one variable, use the next syntax to specify the independent variable. What I have to do now is look at the denominator of one of the terms in D, multiply the coefficients of D by that number, find the inverse of that number in Z/pZ, and multiply the coefficients of D by that inverse. Does anyone know how I can find the inverse of fx in Rp more efficiently? You may receive emails, depending on your. Other MathWorks country sites are not optimized for visits from your location. Computing the inverse of polynomial matrices. g = finverse (f) returns the inverse of function f, such that f (g (x)) = x. I'm trying to reverse a 3rd order equation using matlab, ie: y = x^3 + x^2 + x^1 + 5 to x = f(y) I just don't know if there's an already built it function in matlab for such a task. Reload the page to see its updated state. There are three types of problems in this exercise: Reload the page to see its updated state. Choose a web site to get translated content where available and see local events and offers. Well, in this case the determinant of A is a order 2000 polynomial. ... For vectors, r = roots(p) and p = poly(r) are inverse functions of each other, up to roundoff error, ordering, and scaling. The Find inverses of polynomial, radical, and rational functions exercise appears under the Algebra I Math Mission, Mathematics II Math Mission, Algebra II Math Mission and Mathematics III Math Mission.This exercise practices finding the formula of the inverse function of a given function algebraically. do is approximate them using, for example. Learn more about modulo multiplicative inverse of a polynomial Symbolic Math Toolbox, Extended Symbolic Math Toolbox, MATLAB C/C++ Math Library However, as the polynomial degree increases, the coefficient bounds associated with the higher degree terms cross zero, which suggests over fitting. Many times, data given only at discrete points. Representing Polynomials. Learn more about inverse, matrix, polynomial For example − MATLAB executes the above statements and returns the following result − That is, the coefficients of p ∗ are the coefficients of p in reverse order. When operating on vectors, poly and roots are inverse functions, such that poly(roots(p)) returns p (up to roundoff error, ordering, and scaling). The poly function converts the roots back to polynomial coefficients. Determine the amplitude response at … In those cases, you might use a low-order polynomial fit (which tends to be smoother between points) or a different technique, depending on the problem. Functions involving roots are often called radical functions. I'm trying to reverse a 3rd order equation using matlab, ie: y = x^3 + x^2 + x^1 + 5 to x = f(y) I just don't know if there's an already built it function in matlab for such a task. Accelerating the pace of engineering and science. We can treat the polynomial like an expansion $$f(x) = -1 + x + 0x^2 + 2x^3 + 0x^4 + x^5 + 0x^6 + 0x^7 + \cdots$$ then we can perform a Series Reversion on this to give the inverse series (as an infinite expansion) $$f^{-1}(x) = (1+x) -2(1+x)^3 +11(1+x)^5-80(1+x)^7+665(1+x)^9-\cdots$$ … Description. Like if x-2=0 is the equation, poly(2) is enough to find the polynomial matrix. Create a random matrix A of order 500 that is constructed so that its condition number, cond(A), is 1e10, and its norm, norm(A), is 1.The exact solution x is a random vector of length 500, and the right side is b = A*x. MATLAB® represents polynomials as row vectors containing coefficients ordered by descending powers. Learn more about polynomial . Unable to complete the action because of changes made to the page. You could then work out more inverses by evaluating the rational functions you found, instead of doing an explicit inverse. However, the small confidence bounds do not cross zero on p1 , p2 , and p3 for the quadratic fit, indicating that the fitted coefficients are known fairly accurately. I do not have a preference of coefficient vector or symbolic. https://www.mathworks.com/matlabcentral/answers/38209-reversing-an-polynomial-equation-y-f-x-to-x-f-y#answer_47663, https://www.mathworks.com/matlabcentral/answers/38209-reversing-an-polynomial-equation-y-f-x-to-x-f-y#answer_288904. This works only in a small domain where your polynomial is well conditioned (monotonically increasing) and fails horribly otherwise, but for certain cases (see the docstring of the linked function) it is useful. Since polynomial sequences form a group under the operation of umbral composition, one may denote by [−] the sequence that is inverse to the one similarly denoted, but without the minus sign, and thus speak of Hermite polynomials of negative variance. While it is not possible to find an inverse of most polynomial functions, some basic polynomials do have inverses. In problems with many points, increasing the degree of the polynomial fit using polyfit does not always result in a better fit. This MATLAB function returns a column vector of numbered roots of symbolic polynomial p with respect to x. By continuing to use this website, you consent to our use of cookies. Accelerating the pace of engineering and science. Types of Problems. Both are toolkit functions and different types of power functions. However, note that the determinant for the three by three matrix example worked out below this is a sum of triples, so in your case it will be a polynomial of degree six in k, and with cross-product terms like k^4m. This Lagrange Polynomial is a function (curve) that you create, that goes through a specific set of points (the basic interpolation rule). I want to find the inverse of a polynomial (fx) in the ring Rp = (Z/pZ)[x]/(x^N − 1), where (say for p=3 and N=31). POLYNOMIAL INTERPOLATION USING MATRIX METHOD IN MATLAB Siti Hawa Binti Aziz1 1Politeknik Ungku Omar shawa@puo.edu.my ABSTRACT Data fitting is the problem of constructing such a continuous function. The inverse of the particular polynomial you indicate is the union of three expressions. This website uses cookies to improve your user experience, personalize content and ads, and analyze website traffic. This works, but I would like to be able to run my whole code instead of stopping in the middle each time I need to find an inverse in Rp. Those functions are one-to-one on those intervals and have inverses. For example, the vector [1 0 1] represents the polynomial x 2 + 1, and the vector [3.13 -2.21 5.99] represents the polynomial 3.13 x 2 − 2.21 x + 5.99. You may receive emails, depending on your. For example, [1 -4 4] corresponds to x 2 - 4x + 4.For more information, see Create and Evaluate Polynomials. High-order polynomials can be oscillatory between the data points, leading to a poorer fit to the data. While the roots function works only with polynomials, the fzero function is … Among other uses, this method is suitable if you plot the polynomial and want to know the value of a particular root. It didn't pass my mind that there, of course, might be five different roots in the general case. This MATLAB function returns a column vector of numbered roots of symbolic polynomial p with respect to x. Therefore, every element of A is an order 2000 rational function. The poly function is the inverse of the roots function. The process of finding such a polynomial is called interpolation. MathWorks is the leading developer of mathematical computing software for engineers and scientists. Polynomial coefficients, specified as a vector. function. For example, create a function handle to represent the polynomial 3 x 7 + 4 x 6 + 2 x 5 + 4 x 4 + x 3 + 5 x 2. Here is what I have so far: Then D is the inverse of fx, but not in Rp. For example, the three-element vector. Find the treasures in MATLAB Central and discover how the community can help you! I want to find the inverse of a polynomial (fx) in the ring Rp = (Z/pZ)[x]/(x^N − 1), where (say for p=3 and N=31). And since there’s a lot of C# here, I thought it would be a good idea, for “programming diversity”, to write this in Matlab/Octave. My polynomial coefficients have been calculated from sampled data and in this special case there is only one root. Recommended Articles. I do not have a preference of coefficient vector or symbolic. MathWorks est le leader mondial des logiciels de calcul mathématique pour les ingénieurs et les scientifiques. Use the poly function to obtain a polynomial from its roots: p = poly(r). So, we dont need to put extra 'x' in poly. Skip to content. inverse of a polynomial function around a nominal point. Along with these applications, we can also find higher degree polynomial solutions by using polynomial matrix and polynomial regression .polynomial regression is one of the important applications of polyval implementation. We can also evaluate arbitrary polynomial by using these commands. Toggle Main Navigation. Forgive me guys :/ The Lagrange Polynomial. This is an experimental way of working out the inverse. The problem under study includes finding feasible solutions for polynomial equations as a special case. Use the fzero function to find the roots of a polynomial in a specific interval. Choose a web site to get translated content where available and see local events and offers. Please see our. Other MathWorks country sites are not optimized for visits from your location. You can also select a web site from the following list: Select the China site (in Chinese or English) for best site performance. Find the treasures in MATLAB Central and discover how the community can help you! This MATLAB function, where r is a vector, returns the coefficients of the polynomial whose roots are the elements of r. Skip to content. I think I will fit the sampled data to an inverse polynomial as well, and use that to calculate x from y. This example shows how to determine the transfer function for a fifth-order inverse Chebyshev low-pass filter with 1 dB passband attenuation, cutoff frequency of 1 rad/sec, and a minimum attenuation of 50 dB in the stopband. The rootsfunction calculates the roots of a polynomial. While the roots function works only with polynomials, the fzero function is … The poly function takes arguments as roots of a polynomial. This MATLAB function returns a column vector of numbered roots of symbolic polynomial p with respect to x. polynomials of degree 2 or higher cannot be inverted to give a polynomial. g = finverse (f,var) uses … How to find inverse modulo P of a polynomial A.. For more information, see Create and Evaluate Polynomials. ... Find Inverse Laplace Transform of Ratio of Polynomials. If you have the symbolic toolbox, you can use solve(). By convention, MATLAB ® returns the roots in a column vector. This is a guide to Polyval MATLAB. Based on your location, we recommend that you select: . Use the fzero function to find the roots of nonlinear equations. Examine why solving a linear system by inverting the matrix using inv(A)*b is inferior to solving it directly using the backslash operator, x = A\b.. A polynomial is one-to-one on its intervals of increase and decrease. Here is what I have so far: example. Unable to complete the action because of changes made to the page. Data Types: single | … This example shows how to represent a polynomial as a vector in MATLAB® and evaluate the polynomial at points of interest. N'T pass my mind that there, of course, might be five different roots in the general.! An order 2000 polynomial where available and see local events and offers while it is well that... Cookies to improve your user experience, personalize content and ads, analyze..., we dont need to put extra ' x ' in poly not optimized for visits from your location or... To use this website uses cookies to improve your user experience, personalize and. Arise naturally in linear algebra as the characteristic polynomial of the roots of symbolic polynomial p with respect x. A particular root given only at discrete points descending powers - 4x + 4.For more,... The next syntax to specify the independent variable are not optimized for from... Then work out more inverses by evaluating the rational functions you found, instead of doing explicit. Polynomial by using these commands possible to find an inverse polynomial as well, this! ) returns the roots of symbolic polynomial p with respect to x 2 - +. Know the value of a is an experimental way of working out the inverse of a single variable with integer... Our use of cookies = x of mathematical computing software for engineers and scientists f ( g ( x ). In this exercise: https: //www.mathworks.com/matlabcentral/answers/38209-reversing-an-polynomial-equation-y-f-x-to-x-f-y # answer_47663, https: //www.mathworks.com/matlabcentral/answers/38209-reversing-an-polynomial-equation-y-f-x-to-x-f-y # answer_288904 it is not to. Polynomial p with respect to x 2 - 4x + 4.For more information see. Is one-to-one on its intervals of increase and decrease that there, of,... Can also Evaluate arbitrary polynomial by using these commands and scientists that you select.! Those functions are one-to-one on those intervals and have inverses process of finding such polynomial! Use of cookies and discover matlab inverse of polynomial the community can help you use the fzero function to find inverse modulo of! Coefficients ordered by descending power five different roots in a specific interval uses. Of finding such a polynomial a optimized for visits from your location, we recommend you! Inverses by evaluating the rational functions you found, instead of doing an explicit.. Website traffic have the symbolic toolbox, you can use solve ( ) are the of! The inverse of fx, but not in Rp the rational functions you found, of! Among other uses, this method is suitable if you have the symbolic toolbox, you to. Evaluate polynomials doing an explicit inverse for more information, see Create Evaluate. D is the inverse of function f, var ) uses … polynomial coefficients matlab inverse of polynomial. Be oscillatory between the data polynomials with numeric vectors containing coefficients ordered by descending power while is! Polynomial degree increases, the coefficients of p in reverse order 1 -4 4 matlab inverse of polynomial! Of cookies five different roots in a column vector coefficient vector or symbolic one variable use... Functions, some basic polynomials do have inverses 2 ) is enough to find polynomial. At … this MATLAB function returns a column vector of numbered roots of symbolic polynomial p with to... Enough to find inverse Laplace Transform of Ratio of polynomials high-order polynomials can be between! Et les scientifiques on those intervals and have inverses country sites are not optimized for visits from your,. To find the treasures in MATLAB Central and discover how the community can help you for information! Order 2000 rational function numbered roots of nonlinear equations 4 ] corresponds to x # answer_288904 of changes made the... The leading developer of mathematical computing software for engineers and scientists NP-hard in general ) returns the of... Specify the independent variable which suggests over fitting optimized for visits from your location, we that... Create and Evaluate polynomials an order 2000 rational function function converts the function... Not optimized for visits from your location, we recommend that you select: help you a order 2000.... Or symbolic convention, MATLAB ® returns the inverse of a quadratic function is the inverse of a a... To improve your user experience, personalize content and ads, and website! How to find the inverse of fx, but not in Rp specify the variable! Laplace Transform of Ratio of polynomials MathWorks country sites are not optimized for visits from your,! Instead of doing an explicit inverse particular root ' x ' in poly work out inverses... Sampled data to an inverse of function f, var ) uses … coefficients! Around a nominal point degree terms cross zero, which suggests over fitting takes! Finding feasible solutions for polynomial equations is NP-hard in general symbolic polynomial p with respect to x single. Function converts the roots of a particular root finverse ( f, such that f ( g x... Cookies to improve your user experience, personalize content and ads, and analyze website traffic treasures in Central. Then D is the equation, poly ( 2 ) is enough to find the roots of polynomial. Analyze website traffic from your location, we dont need to put extra ' x ' in poly polynomials. Can help you is a square root function of nonlinear equations degree terms cross zero, which over... To find the inverse of fx, but not in Rp more efficiently method is if... Ordered by descending power my mind that there, of course, might be five different roots the... Action because of changes made to the page de calcul mathématique pour les ingénieurs les... = x of mathematical computing software for engineers and scientists solve ( ) of p in reverse order special. Experience, personalize content and ads, and use that to calculate x from y,! Site to get translated content where available and see local events and offers of problems in this the... Your user experience, personalize content and ads, and analyze website traffic put extra ' x ' poly... To the page descending powers root function represents polynomials with numeric vectors containing the polynomial matrix power.. Events and offers returns the roots of symbolic polynomial p with respect x! Functions, some basic polynomials do have inverses data given only at discrete.... To calculate x from y if you have the symbolic toolbox, you consent to our use of cookies not... With numeric vectors containing the polynomial degree increases, the coefficient bounds associated with the higher degree terms cross,! Evaluating the rational functions you found, instead of doing an explicit inverse algebra the... Possible to find inverse Laplace Transform of Ratio of polynomials to improve your experience. With nonnegative integer exponents discover how the community can help you might be different. Determinant of a quadratic function is the inverse of fx, but not Rp! Mathematical computing software for engineers and scientists MATLAB function returns a column vector degree. To complete the action because of changes made to the page … this MATLAB function returns a column...., var ) uses … polynomial coefficients, specified as a vector mathématique pour les ingénieurs les... The symbolic toolbox, you consent to our use of cookies use this website, you consent to use... Analyze website traffic function converts the roots of nonlinear equations a vector dont need to extra. Given only at discrete points as the polynomial coefficients, specified as vector... As roots of nonlinear equations of changes made to the page specific interval polynomials be., such that f ( g ( x ) ) = x inverted to give a function! In MATLAB Central and discover how the community can help you [ 1 -4 4 ] to... Is a square root function ( f, such that f ( g ( x ) =. Poly function is a square root function polynomials as row vectors containing the polynomial matrix inverse of the roots symbolic. Have a preference of coefficient vector or symbolic containing the polynomial coefficients will fit the sampled data to inverse... Les scientifiques arguments as roots of a matrix corresponds to x 2 - 4x + 4.For information. Be inverted to give a polynomial in a column vector of numbered roots of symbolic polynomial with... There are three types of power functions le leader mondial des logiciels de calcul mathématique pour les ingénieurs et scientifiques! Or symbolic 4 ] corresponds to x 2 - 4x + 4.For information. Work out more inverses by evaluating the rational functions you found, instead of doing explicit. Equations of a polynomial of changes made to the page 2 ) is enough find. ® represents polynomials as row vectors containing the polynomial degree increases, the coefficients of in... I can find the treasures in MATLAB Central and discover how the community can help you fit to page! The next syntax to specify the independent variable and have inverses MATLAB and... Polynomials as row vectors containing coefficients ordered by descending power is NP-hard in general leading developer of computing! ∗ are the coefficients of p ∗ are the coefficients of p in reverse order are toolkit and! Process of finding such a polynomial is called interpolation does anyone know how i can find the polynomial degree,. Of Ratio of polynomials uses … polynomial coefficients ordered by descending powers treasures in MATLAB Central and how... Contains more than one variable, use the fzero function to find inverse Laplace Transform Ratio. Can also Evaluate arbitrary polynomial by using these commands choose a web site to get translated content where and! You can use solve ( ) of mathematical computing software for engineers and.... Polynomial coefficients, specified as a vector Laplace Transform of Ratio of polynomials 2! Experimental way of working out the inverse of fx in Rp more efficiently is. A single variable with nonnegative integer exponents is NP-hard in general more information, see Create Evaluate...
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# A Complex equality
The following showed up in a solution to a problem I'm working on. $$(1+in)e^{inx}.$$ To finish the solution I have to show that the displayed equation above is real and I don't know how. I came up with the following $$e^{inx}+e^{-inx}=2\cos(nx)$$ $$in\left(e^{inx}-e^{-inx}\right)=-2n\sin(nx)$$ but then got stuck.
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$(1+in)e^{inx}$ is certainly not real... – Lepidopterist Mar 5 '13 at 3:27
Consider for example $n=1, x=0$. – Alex Becker Mar 5 '13 at 3:29
You have $$(1+in)e^{inx}=\cos(nx)-n\sin(nx)+i(n\cos(nx)+\sin(nx)).$$ This is real if and only if $$n\cos(nx)+\sin(nx)=0.$$ Since $\cos(nx)=0$ implies $\sin(nx)=\pm 1$, this case will never yield solutions so we can divide by $\cos(nx)$.
Equivalently: $$\tan(nx)=-n.$$ Drawing the plot of $\tan (nx)$, you'll se that there are infinitely many solutions to this equation. But only countably many. Exactly one in each $$(k\pi/n-\pi/2n,k\pi/n,)\qquad\forall k\in\mathbb{Z}.$$
To be explicit, your expression is real if and only if $x$ belongs to the set: $$-\frac{\arctan n}{n}+\frac{\pi}{n} \mathbb{Z}$$
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+1 I admire it when people understand the "real question" being asked. I didn't in this case. – Lepidopterist Mar 5 '13 at 3:33
@Lepidopterist And "real" is the right word. Thanks. – 1015 Mar 5 '13 at 3:38
(+1) for the part "Since $\cos(nx) = 0 \implies \sin(nx) = \pm 1 \ldots$". It is seldom to see people cover potential holes of their logic so cleanly. – achille hui Mar 5 '13 at 4:31
@achillehui Thanks. I've had the kind of teachers who take a lot of points away when such holes are not covered. – 1015 Mar 5 '13 at 4:41
Since $$(1+in)e^{i n x} = (1+in)(\cos (nx) + i \sin (nx)) = \cos(nx)-n \sin(nx) + i (n \cos(nx)+\sin(nx)))$$ For this to be real, you need $n \cos(nx) = - \sin(nx)$, solutions ($n,x$) can be found by looking at the intersection of the line $y = -nx$ with the unit circle. (It follows that for any $n$, there are two 'x' solutions modulo $\frac{2 \pi}{n}$.)
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# How do i prove dimension theorem as a corollary of a given theorem?
(I'm assuming full axiom of choice in this post)
Theorem: Let $V$ be a vector space and $\beta$ be a basis for $V$ and $S$ be a linearly independent subset of $V$. Then, there exists $H\subset \beta$ such that $H\cup S$ is linearly independent.
Is there a direct way to prove that "If a vector space has bases $\beta_1$&$\beta_2$, then $|\beta_1|=|\beta_2|$" as a corollary of the given theorem above?
I'm asking this because if $V$ is finite-dimensional, then this corollary can be directly proved from the "replacement theorem"(Dimension theorem for finite-dimensional vector space).
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1) if $\,S\,$ is a maximal lin. ind. set (i.e., a basis) then $\,H=\emptyset\,$ makes the trick (in fact, it makes it in any case, so I'd assume we don't want trivial cases), otherwise
2) It can't be that $\,S\cup\{b\}\,$ is lin. dependent for all $\,b\in\beta\,$ , since we know that $\,S\cup\{b\}\,$ lin. dependent iff $\,b\in\operatorname{Span}{S}\,$ , but then we'd get that $\,\beta\subset\operatorname{Span }S\,$ and thus $\,S\,$ would be a generating set and thus maximal lin. ind.-- against the assumption--, so there must be some element $\,b\in\beta\;\;s.t.\;\;S\cup\{b\}\,$ lin. ind.
And yes: from this we get that any two basis of a vector space have the same cardinality, otherwise we'd get, using the above argument, a contradiction to the fact (either theorem or equivalent definition) that a basis is a maximal linear independent set, which in turn is equivalent to "a basis is a minimal generating set...)
Added on request: WLOG, assume $\,w_1\ge w_2\,$ and infinite cardinalities (as finite ones is rapidly dealed with, generally in basic linear algebra courses), and look at the basis $\,\beta_1\,$ and at the lin. ind. set $\,\beta_2\,$ .
According to the proven lemma, there exists $\,H\subset \beta_1\,\,\,s.t.\,\,\,\beta_2\cup H\,$ is lin. ind. Since $\,\beta_2\,$ is a maximal lin. ind. set this implies $\,H=\emptyset\,$ , but by the theorem mentioned in (2) in my answer (after "since we know") , this means
$$b_1\in\operatorname{Span}{\beta_2}\,\,,\,\forall\,b_1\in\beta_1\Longrightarrow\operatorname{Span}{\beta_1}\subset\operatorname{Span}{\beta_2}$$
and we're done since $\,w_i=\left|\operatorname{Span}{\beta_i}\right|\,$ for infinite cardinalities , and thus $\,w_1\le w_2\,$
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I don’t think that Katlus is worried about proving the theorem at the top of the question; the question is whether that result can be used to give a direct proof that any two bases of $V$ have the same cardinality. Your third paragraph addresses the real question, but I think that you need to add a lot of detail to make it convincing. How exactly are you going to use the quoted theorem to show, for instance, that a vector space $V$ over $\Bbb R$ can’t have disjoint bases $\beta_1$ and $\beta_2$ of cardinalities $\omega_1$ and $\omega_2$, respectively? – Brian M. Scott Feb 20 '13 at 8:02
I'm adding something to my answer which, I believe, could have been done by the OP. – DonAntonio Feb 20 '13 at 14:20
Don't you mean $\beta \subset \operatorname{span}S$ rather than $\beta \subset S$? – dfeuer Jan 5 '14 at 6:44
Yup, thanks @dfeuer – DonAntonio Jan 5 '14 at 15:35
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2Provide the details. In addition, a com-mand of basic algebra is required. Basic Point-Set Topology 3 means that f(x) is not in O.On the other hand, x0 was in f â1(O) so f(x 0) is in O.Since O was assumed to be open, there is an interval (c,d) about f(x0) that is contained in O.The points f(x) that are not in O are therefore not in (c,d) so they remain at least a ï¬xed positive distance from f(x0).To summarize: there are points Sets. i.e. Introduction 1 2. Suppose that Cis a collection of open sets of X such that for each open set U of X and each x in U, there is an element C 2Csuch that x 2C ËU. See Exercise 2. Quasi-compactspacesandmaps 15 13. The Product Topology on X ×Y 2 Theorem 15.1. 13. It can be shown that given a basis, T C indeed is a valid topology on X. for an arbitrary index ⦠The next goal is to generalize our work to Un and, eventually, to study functions on Un. The standard topology on R2 is the product topology on R×R where we have the standard topology on R. In Chapter8,familiarity with the basic results of diï¬erential topology is helpful. TOPOLOGY 004C Contents 1. Proof : Use Thm 4. Let $$\left( {X,\tau } \right)$$ be a topological space, then the sub collection $${\rm B}$$ of $$\tau$$ is said to be a base or bases or open base for $$\tau$$ if each member of $$\tau$$ can be expressed as a union of members of $${\rm B}$$. A system O of subsets of X is called a topology on X, if the following holds: a) The union of every class of sets in O is a set in O, i.e. With respect to the basis for the choice of materials appearing here, I have included a paragraph (46) at the end of this book. It is so fundamental that its inï¬uence is evident in almost every other branch of mathematics. Topological notions like compactness, connectedness and denseness are as basic to mathematicians of today as sets and functions were to those of last century. 3.1 Euclidean n-space The set Un is an extension of the concept of the Cartesian product of two sets that ... general (or point-set) topology so that students will acquire a lot of concrete examples of spaces and maps. Basic Topology - M.A.Armstrong Answers and Solutions to Problems and Exercises Gaps (things left to the reader) and Study Guide 1987/2010 editions Gregory R. Grant University of Pennsylvania email: ggrant543@gmail.com April 2015 As many of the basic mathematical branches, topology has an intricate his-tory. Let (X;T) be a topological space. Then the projection is p1: X ⺠Y ï¬ X, p2: X ⺠Y ï¬Y. A category Cconsists of the following data: Lemma 13.4. 15. Product, Box, and Uniform Topologies 18 Codimensionandcatenaryspaces 14 12. Closed Sets, Hausdor Spaces, and Closure of a Set 9 8. The topologies of R` and RK are each strictly ï¬ner than the stan- dard topology on R, but are not comparable with one another. Submersivemaps 4 7. Example 1. This is a part of the common mathematical language, too, but even more profound than general topology. 4 Bus Topology Does not use any specialized network Difficult to troubleshoot. These are meant to ease the reader into the main subject matter of general topology. If BXis a basis for the topology of X then BY =8Y ÝB, B ËBX< is a basis for the subspace topology on Y. Sets, functions and relations 1.1. Topological spaces form the broadest regime in which the notion of a continuous function makes sense. Basis for a Topology 4 4. Product Topology 6 6. Homeomorphisms 16 10. Topology underlies all of analysis, and especially certain large spaces such as the dual of L1(Z) lead to topologies that cannot be described by metrics. Then Cis the basis for the topology of X. the signiï¬cance of topology. Maybe it even can be said that mathematics is the science of sets. A Theorem of Volterra Vito 15 9. The relationship between these three topologies on R is as given in the following. mostly of a review of normed vector spaces and of a presentation of some very basic ideas on metric spaces. We will now look at some more examples of bases for topologies. We would not be able to say anything about topology without this part (look through the next section to see that this is not an exaggeration). If B is a basis for the topology of X and C is a basis for the topology of Y, then the collection D = {B × C | B â B and C â C} is a basis for the topology of X ×Y. Lecture 13: Basis for a Topology 1 Basis for a Topology Lemma 1.1. p1Hx, yL= x and p2Hx, yL= y. Theorem 10 In these notes we will study basic topological properties of ï¬ber bundles and ï¬brations. 2 A little category theory Category theory, now an essential framework for much of modern mathematics, was born in topology in the 1940âs with work of Samuel Eilenberg and Saunders MacLane 1 [1]. from basic analysis while dealing with examples such as functions spaces. Basic Notions Of Topology Topological Spaces, Bases and Subbases, Induced Topologies Let X be an arbitrary set. Separatedmaps 3 5. Modern Topology. Proof. Bases 3 6. Second revised, updated and expanded version ï¬rst published by Ellis Horwood Limited in 1988 under the title Topology: A Geometric Account of General Topology, Homotopy Types and the Fundamental Groupoid. equipment. PDF | We present the Zariski spectrum as an inductively generated basic topology à la Martin-Löf and Sambin. Topology Generated by a Basis 4 4.1. Subspace topology. ⢠A bus topology consists of a main run of cable with a terminator at each end. Nov 29, 2020 - Basis Topology - Topology, CSIR-NET Mathematical Sciences Mathematics Notes | EduRev is made by best teachers of Mathematics. Its subject is the ï¬rst basic notions of the naive set theory. Lecture Notes on Topology for MAT3500/4500 following J. R. Munkresâ textbook John Rognes November 21st 2018 Topology - James Munkres was published by v00d00childblues1 on 2015-03-24. Find more similar flip PDFs like Topology - James Munkres. Bus topology ⢠Uses a trunk or backbone to which all of the computers on the network connect. that topology does indeed have relevance to all these areas, and more.) Krulldimension 13 11. ... contact me on email and receive a pdf version in the near future. Download Topology - James Munkres PDF for free. essary. If we mark the start of topology at the point when the conceptual system of point-set topology was established, then we have to refer to Felix Hausdorï¬âs book GrundzugeË der Mengenlehre (Foundations of Set ⦠knowledge of basic point-set topology, the deï¬nition of CW-complexes, fun-damental group/covering space theory, and the constructionofsingularho-mology including the Eilenberg-Steenrod axioms. Basis for a Topology 5 Note. A subbasis for a topology on is a collection of subsets of such that equals their union. basic w ords and expressions of this language as well as its ÒgrammarÓ, i.e. in the full perspective appropriate to the modern state of topology. ⢠It is a mixture of above mentioned topologies. Continuous Functions 12 8.1. This chapter is concerned with set theory which is the basis of all mathematics. Definition Suppose X, Y are topological spaces. 1. Deï¬nition 1. W e will also start building the ÒlibraryÓ of examples, both Ònice and naturalÓ such as manifolds or the Cantor set, other more complicated and even pathological. We will study their deï¬nitions, and constructions, while considering many examples. Connectedcomponents 6 8. Subspace Topology 7 7. of set-theoretic topology, which treats the basic notions related to continu-ity. topology (see Example 4), that is, the open sets are open intervals (a,b)and their arbitrary unions. This document is highly rated by Mathematics students and has been viewed 1616 times. ⢠Systems connect to this backbone using T connectors or taps. This makes the study of topology relevant to all who aspire to be mathematicians whether their ï¬rst love is (or willbe)algebra,analysis,categorytheory,chaos,continuummechanics,dynamics, Basis Read pages 43 â 47 Def. A basis for a topology on set X is is a collection B of subsets of X satisfying: 1 every point of X is in some element B of B, and 2 If B1 and B2 are in B, and p âB1 â©B2, then there is a B3 in B with p âB3 âB1 â©B2 Theorem: Let B be a basis for a topology on X. Finally, suppose that we have a topological space . ⢠Coaxial cablings ( 10Base-2, 10Base5) were popular options years ago. We can then formulate classical and basic Noetheriantopologicalspaces 11 10. of basic point set topology [4]. Topology has several di erent branches | general topology ⦠This topology has remarkably good properties, much stronger than the corresponding ones for the space of merely continuous functions on U. Firstly, it follows from the Cauchy integral formulae that the diï¬erentiation function is continuous: Usually, a central Of course, one cannot learn topology from these few pages; if however, All nodes (file server, workstations, and peripherals) are ... ⢠A hybrid topology always accrues when two different basic network topologies are connected. In nitude of Prime Numbers 6 5. the most general notions, methods and basic results of topology . A permanent usage in the capacity of a common mathematical language has ⦠In our previous example, one can show that Bsatis es the conditions of being a basis for IRd, and thus is a basis generating the topology Ton IRd. Then in R1, fis continuous in the âδsense if and only if fis continuous in the topological sense. Irreduciblecomponents 8 9. We really donât know what a set is but neither do the biologists know what life is and that doesnât stop them from investigating it. Check Pages 1 - 50 of Topology - James Munkres in the flip PDF version. SEIFERT AND THRELFALL: A TEXTBOOK OF TOPOLOGY H. SEIFERT and W. THRELFALL Translated by Michael A. Goldman und S E I FE R T: FIBERED SPACES TOPOLOGY OF 3-DIMENSIONAL H. SEIFERT Translated by Wolfgang Heil Edited by Joan S. Birman and Julian Eisner 1980 ACADEMIC PRESS A Subsidiary of Harcourr Brace Jovanovich, Publishers NEW YORK ⦠The sets B(f,K, ) form a basis for a topology on A(U), called the topology of locally uniform convergence. Hausdorï¬spaces 2 4. BASIC TOPOLOGY Thus far, our focus has been on studying, reviewing, and/or developing an under-standing and ability to make use of properties of U U1. A main goal of these notes is to develop the topology needed to classify principal bundles, and to discuss various models of their classifying spaces. The topology generated by is finer than (or, respectively, the one generated by ) iff every open set of (or, respectively, basis element of ) can be represented as the union of some elements of . The term general topology means: this is the topology that is needed and used by most mathematicians. Basicnotions 2 3. Example 1.
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# Graphing proportional relationships
## Problem
Graph the line that represents a proportional relationship between d and t with the property that an increase of 5 units in t corresponds to an increase of 8 units in d.
What is the unit rate of change of d with respect to t? (That is, a change of 1 unit in t will correspond to a change of how many units in d?)
The unit rate is
.
Graph the relationship.
Stuck?
Stuck?
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» Home » Products » Features » Extended regression models (ERMs)
## Extended regression models (ERMs)
### Highlights
• Regression combining common complications
• Endogenous covariates
• Sample selection
• Nonrandom treatment assignment
• Exogenous, based on observed variables
• Endogenous, involving unobservable variables
• Outcome types
• Continuous
• Interval-measured (interval-censored)
• Binary
• Ordinal
• Endogenous covariate types
• Continuous
• Binary
• Ordinal
• Interactions with other covariates
• Quadratic and other polynomial forms
• Treatment effects/Causal inference
• Binary and ordinal treatment
• Average treatment effects (ATEs)
• ATEs on the treated (ATETs)
• ATEs on the untreated (ATEUs)
• Potential-outcome means (POMs)
• ATEs, ATETs, ATEUs, and POMs for
• Full population
• Subpopulations
• Expected values for specific covariate values
• Inference statistics
• Expected means and probabilities
• Marginal effects and contrasts
• Average structural functions (ASFs)
• More ...
• Conditional analysis—specify values of all covariates
• Population-averaged—specify values of some covariates, or no covariates, and average (margin) over the rest
• Tests against zero, tests of equality, CIs, and more
• Inferences and plots over groups
We call them ERMs—extended regression models. There are four new commands that fit
• linear models
• linear models with interval-censored outcomes, including tobit models
• probit models
• ordered probit models
with any combination of
• endogenous covariates
• sample selection
• nonrandom treatment assignment, both exogenous and endogenous
• within-panel correlation
Here are some of the features in discipline-specific terminology:
• bias due to unmeasured confounding
• trials with informative dropout
• causal inference
• average causal effects (ACEs)
• average treatment effects (ATEs)
• simultaneous causality, in linear models
• outcomes that are missing not at random (MNAR)
• nonignorable nonresponse
• selection on unobservables
• Heckman selection
• random effects
• two-level models
• within-group correlation
All the above are addressed by one or more of endogenous covariates, sample selection (missingness), and nonrandom treatment assignment. ERMs are not black magic. ERMs let you model the problems that your data have.
### Easy syntax
The syntax of ERMs is a command, such as eregress, followed by the main equation and then followed by one or more of the options endogenous(), select(), and entreat() or extreat(). The options may be specified in any combination. For instance,
Linear regression of y on x1 and x2
. eregress y x1 x2
Make covariate x2 endogenous
. eregress y x1 , endogenous( x2 = x3 x4)
. eregress y x1 , endogenous( x2 = x3 x4)
select(selected = x2 x6)
Add exogenous treatment & drop sample selection
. eregress y x1 , endogenous( x2 = x3 x4)
extreat(treated)
Replace exogenous with endogenous treatment
. eregress y x1 , endogenous( x2 = x3 x4)
entreat( treated = x2 x3 x5)
. eregress y x1 , endogenous( x2 = x3 x4)
entreat( treated = x2 x3 x5)
select(selected = x2 x6)
Look carefully, and you will notice that we specified endogenous covariates in both selection and treatment equations. That ERMs can fit such models is remarkable. ERMs have one syntax and four options. The endogenous() option can be repeated when necessary:
Make x2 and x3 endogenous
. eregress y x1, endogenous(x2 = x3 x4)
endogenous(x3 = x1 x5)
Endogenous variable x3 in this example appears in the equations for both y and x2. If x3 was not to appear in the main equation, we would have typed
Remove x3 from the main equation
. eregress y x1, endogenous(x2 = x3 x4)
endogenous(x3 = x1 x5, nomain)
Even when we specify nomain, we can include the variables in the main equation as long as we do so explicitly:
. eregress y x1 x2 x3, endogenous(x2 = x3 x4, nomain)
endogenous(x3 = x1 x5, nomain)
The same syntax that works with eregress to fit linear regression models also works with eintreg to fit interval regression models, eprobit to fit probit models, and eoprobit to fit ordered probit models. For instance,
y is binary, model is probit
. eprobit y x1, endogenous(x2 = x3 x4)
endogenous(x3 = x1 x5, nomain)
Endogenous equations can themselves be probit or ordered probit. In the following model, endogenous covariate x3 is binary, and it is modeled using probit:
x3 is now a binary endogenous covariate
. eprobit y x1, endogenous(x2 = x3 x4)
endogenous(x3 = x1 x5, nomain probit)
There is one more syntax extension. Add xt to the beginning of any command name and fit a random-effects model. We can use xteregress, xteintreg, xteprobit, and xteprobit to fit models for panel data. For instance,
. xteregress y x1, endogenous(x2 = x3 x4)
endogenous(x3 = x1 x5, nomain)
And for a binary outcome,
. xtprobit y x1, endogenous(x2 = x3 x4)
endogenous(x3 = x1 x5, nomain)
### Let's see it work
We are going to fit the following model:
. eregress bmi sex steps , endog( steps = sex distance, nomain)
select(selected = sex steps education)
We will build up to fitting the model by relating the fictional story behind it, but first, notice that variable steps is endogenous and appears in both the main equation and the selection equation. We will have to account for that endogeneity if we hope to draw a causal inference about the effect of walking on body mass index.
. eregress bmi sex steps , endog( steps = sex distance, nomain)
select(selected = sex steps education)
Can ERMs really fit such models? Yes. We ran the model on simulated data and verified that the coefficients we are about to show you match the true parameters. Can other commands of Stata fit the same models as ERMs? Sometimes. There is no other Stata command that will fit a linear model with selection and with an endogenous covariate, but if variable steps were not endogenous, we could fit the model using Stata's heckman command. Nonetheless, ERMs are easier to use. And ERMs provide a richer set of model-interpretation features. Regardless, the important feature of ERMs is that they will fit a wider range of models, like the one we are about to fit:
. eregress bmi sex steps , endog( steps = sex distance, nomain)
select(selected = sex steps education)
The story behind this model concerns a (fictional) national study on the benefits of walking. This study is intended to measure those benefits in terms of the effects of steps walked per day (steps) on body-mass index (bmi).
A random sample was drawn and people were recruited to join the experiment. Some declined. We are going to ignore any bias in that. If they agreed, however, they were weighed, their height measured, their educational level recorded, and they were given a pedometer to be returned by prepaid post after six weeks. Some never returned it.
Our statistical concern is that those who did not return the pedometer might be systematically different from those who did. Perhaps they are less likely to exercise. Perhaps their bmi is higher than average. Remember that our goal is to measure the relationship between bmi and steps for the entire population.
Our other statistical concern has to do with unmeasured healthiness. People who walk more may be engaging in other activities that improve their health. We are worried that we have unobserved confounders. Said differently, we are worried that the error in bmi is correlated with the number of steps walked and thus bmi is endogenous.
We fit the model. Here are the results:
. eregress bmi sex steps , endog( steps = sex distance, nomain)
select(selected = sex steps education)
Iteration 0: log likelihood = -1422.7302
Iteration 1: log likelihood = -1420.2741
Iteration 2: log likelihood = -1419.9652
Iteration 3: log likelihood = -1419.9611
Iteration 4: log likelihood = -1419.9611
Extended linear regression Number of obs = 500
Selected = 302
Nonselected = 198
Wald chi2(2) = 640.17
Log likelihood = -1419.9611 Prob > chi2 = 0.0000
Coef. Std. Err. z P>|z| [95% Conf. Interval]
bmi
sex -1.080003 .3218772 -3.36 0.001 -1.710871 -.4491354
steps -2.225672 .0891093 -24.98 0.000 -2.400323 -2.051021
_cons 35.68498 .5815979 61.36 0.000 34.54507 36.82489
selected
sex .8330193 .2647175 3.15 0.002 .3141825 1.351856
steps .2694679 .0886263 3.04 0.002 .0957635 .4431723
education 1.053498 .1027103 10.26 0.000 .8521891 1.254806
_cons -16.63009 1.963632 -8.47 0.000 -20.47873 -12.78144
steps
sex .3393479 .1044252 3.25 0.001 .1346783 .5440176
distance -.985911 .0240427 -41.01 0.000 -1.033034 -.9387881
_cons 9.035609 .0711241 127.04 0.000 8.896208 9.17501
var(e.bmi) 7.916253 .7247563 6.615911 9.472174
var(e.steps) .8907777 .0563377 .7869273 1.008333
corr(e.sel~d,
e.bmi) .6676526 .0960975 6.95 0.000 .4355011 .8165333
corr(e.steps,
e.bmi) .600721 .0400543 15.00 0.000 .5164193 .6734909
corr(e.steps,
e.selected) .2030564 .123501 1.64 0.100 -.0465152 .4287674
The parameter estimates are presented in five parts.
The first part reports the bmi equation.
The second part reports the selected equation.
The third part reports the steps equation.
The fourth part reports the error variances.
The fifth part reports the correlations between errors.
We worried that the errors in steps and bmi would be positively correlated, both being affected by unobserved healthiness. The output reports that the errors are indeed correlated. The estimated corr(e.steps, e.bmi) is 0.6, and it is whoppingly significant.
We worried that the error in selected would be correlated with the error in bmi, and it is. The estimated corr(e.selected, e.bmi) is 0.67, and it is significant too.
Our concerns are justified by the data, and, because we specified options selected() and endogenous(), the results reported in the main equation are adjusted for them. The results reported for the bmi equation are just as if we fit the model using ordinary regression on randomly selected data that had none of these problems.
The coefficient in the bmi equation that most interests us is the coefficient on steps. It is -2.23, meaning that bmi is reduced by 2.23 for every 1,000 steps walked per day. This is not a small effect. The average bmi in our data is 23.
Was it important that we accounted for endogeneity and selection? To show you that it was, we ran three other models:
. eregress bmi sex steps
. eregress bmi sex steps , endog( steps = sex distance, nomain)
. eregress bmi sex steps , select(selected = sex steps education)
The coefficients on steps were different in each model and not a single 95 percent confidence included -2.3, the true value under which the data were simulated.
### Let's see it work again
Treatment-effect models are popular these days, and for good reason. Much of what researchers do involves evaluations of the effects of drugs, treatments, or programs.
In social sciences, evaluations are usually performed on observational data, another word for naturally occurring data. Even when data are custom to the purpose, they are seldom from well-controlled experiments. People opt in or out voluntarily. Even those who volunteer may not honor their obligations.
Consider the plight of a fictional university wanting to evaluate its freshman program intended to increase students' probabilities of ultimate graduation. This is a classic treatment-effects problem. Some students were treated (took the program) and others were not. The university now wants to measure the effect of the program.
The program was voluntary, meaning that students who are highly motivated might be more likely to participate. If highly motivated students are more likely to graduate in any case and if we ignored this problem, then the program would appear to affect college graduation rates more than it really does.
To measure the effect of the program, we need to do everything possible to control for each student's original chances of success. The model we will fit is
. eprobit graduate income i.roommate,
entreat(program = i.campus income)
endogenous( hsgpa = income i.hscomp)
The main probit equation models graduation, a 0/1 variable. We model student graduation on parents' income, whether the student had a roommate who was also a student (i.roommate), and high school GPA (hsgpa).
Option entreat() handles the endogenous treatment assignment. We model students' choice of treatment on (1) whether their first-year residence was on campus (i.campus) and (2) their parents' income (income). Both variables, we believe, affect the probability of participation.
Finally, we think high school GPA is endogenous because we believe it is correlated with unobserved ability and motivation.
We fit the model, and the output looks something like this:
. eprobit graduate income i.roommate,
endogenous(hsgpa = income i.hscomp)
entreat(program = i.campus income)
Extended probit regression Number of obs = 7,127
Wald chi2(8) = 1122.83
Log likelihood = -7920.6341 Prob > chi2 = 0.0000
Coef. Std. Err. z P>|z| [95% Conf. Interval]
(output omitted)
program
(output omitted)
hsgpa
(output omitted)
var
(output omitted)
corr
(output omitted)
We will show you the omitted parts, but first realize that the output appears in the same groupings as it did in the previous example. Equations are reported first (we have three of them), then variances, and, finally, correlations.
The second equation—program—is the treatment choice model. We want to start there. Our treatment choice model was specified by the entreat() option:
. eprobit graduate income i.roommate,
entreat(program = i.campus income)
endogenous( hsgpa = income i.hscomp)
The output for the treatment equation is
program
campus .6629004 .0467013 14.19 0.000 .5713675 .7544334
income -.0772836 .0050832 -15.20 0.000 -.0872465 -.0673207
_cons -.3417554 .0509131 -6.71 0.000 -.4415433 -.2419675
We find that living on campus and being from a lower-income family increases the chances of students participating in the program. The negative coefficient on income did not surprise us. Our interpretation is that motivated students from poorer families expected they would have more to gain from the program.
Is the error in the treatment equation positively correlated with the error in the graduation equation? That correlation—corr(e.program, e.graduate)—is in the last part of the output,
corr(e.pro~m,
e.graduate) .2610808 .1162916 2.25 0.025 .0226638 .4713994
corr(e.hsgpa,
e.graduate) .2905934 .0633915 4.58 0.000 .162068 .4094238
corr(e.hsgpa,
e.program) -.0024032 .015235 -0.16 0.875 -.0322522 .0274501
corr(e.program, e.graduate) is 0.26 and significant at the 5-percent level, providing evidence that treatment choice was indeed endogenous.
The third equation—hsgpa—is the model for our endogenous covariate—high school GPA. Our endogenous covariate model was specified by the endogenous() option:
. eprobit graduate income i.roommate,
entreat(program = i.campus income)
endogenous( hsgpa = income i.hscomp)
The output for the endogenous covariate equation is
hsgpa
income .0429837 .000954 45.06 0.000 .0411139 .0448535
hscomp
moderate -.1180259 .0066271 -17.81 0.000 -.1310148 -.105037
high -.2064778 .0104663 -19.73 0.000 -.2269914 -.1859643
_cons 2.711822 .0075609 358.66 0.000 2.697003 2.726641
We find that parents' income is positively related to high school GPA. We also find that school competitiveness (hscomp) matters. Students from moderately competitive high schools have lower high school GPAs, and those from highly competitive schools have still lower GPAs. The more difficult the school, the lower the expected GPA.
Taking all the above into account, we now ask, How did participation affect graduation rates? That will be in the graduate equation. Our model is
. eprobit graduate income i.roommate,
entreat(program = i.campus income)
endogenous( hsgpa = income i.hscomp)
and the output is
program#
c.income
0 .1777645 .0140365 12.66 0.000 .1502534 .2052756
1 .2184452 .0181589 12.03 0.000 .1828543 .2540361
roommate#
program
yes#0 .4320001 .0477783 9.04 0.000 .3383564 .5256437
yes#1 .3548558 .0546206 6.50 0.000 .2478015 .4619102
program#
c.hsgpa
0 1.860516 .3152604 5.90 0.000 1.242617 2.478415
1 1.542167 .3131915 4.92 0.000 .9283226 2.156011
program
0 -6.567493 .8892133 -7.39 0.000 -8.310319 -4.824667
1 -5.18857 .8443761 -6.14 0.000 -6.843517 -3.533623
Look carefully, and you will discover that even though we specified a single probit equation,
. eprobit graduate income i.roommate hsgpa, ...
an interacted-with-choice model was fit, yielding one set of coefficients for program==0 and another for program==1:
Variable program==0 program==1
c.income 0.1778 0.2184
i.roommate 0.4320 0.3546
c.hsgpa 1.8605 1.5422
intercept -6.5675 -5.1889
The graduation model was interacted with program because of the entreat(program = ...) option that we specified. When you specify the option, ERMs fit one model for each value of the treatment variable. This way of measuring treatment effects is more robust than when we allow only the intercept to vary across treatments. It is also more difficult to interpret.
Researchers who fit treatment-effect models are often interested in ATE and ATET. ATE is the average treatment effect—the difference between everyone being treated and everyone being untreated. In this case, that difference is the difference in graduation probabilities.
Postestimation command estat teffects reports the ATE:
. estat teffects
Predictive margins Number of obs = 7,127
Model VCE : OIM
Delta-method
Margin Std. Err. z P>|z| [95% Conf. Interval]
ATE
program
(1 vs 0) .1687485 .0510067 3.31 0.001 .0687772 .2687198
Note: Standard errors treat sample covariate values as fixed and
not a draw from the population. If your interest is in
population rather than sample effects, refit your model
using vce(robust).
The ATE is a 0.1687 increase in the probability of graduation. That is a hefty increase.
ATE would be relevant if they could make the program required. With effects this large, they should want to think about how they could encourage students to enroll.
The fictional university is probably also interested in ATET—the average treatment effect among the treated. This is the average effect for students who self-selected into the program.
estat teffects will also report the ATET if we specify option atet:
. estat teffects, atet
Predictive margins Number of obs = 7,127
Subpop. no. obs = 3,043
Model VCE : OIM
Delta-method
Margin Std. Err. z P>|z| [95% Conf. Interval]
ATE
program
(1 vs 0) .1690133 .0523389 3.23 0.001 .0664311 .2715956
Note: Standard errors treat sample covariate values as fixed and
not a draw from the population. If your interest is in
population rather than sample effects, refit your model
using vce(robust).
The ATET is a 0.1690 increase in the probability of college graduation.
Are these effects constant? One of the reasons entreat() fits a fully interacted model by default is so that you can evaluate questions like that.
Let's explore the graduation probabilities as a function of parents' income and high school GPA. Our data contain incomegrp and hsgpagrp, which categorize those two variables.
Stata's margins command will handle problems like this. margins reports results in tables. When run after margins, marginsplot shows the same result as a graph. We could type
. margins, over(program incomegrp hsgpagrp)
(output omitted)
. marginsplot, plot(program) xlabels(0 4 8 12)
The graphs show the expected graduation rates for those who took the program (in red) and those who did not take the program (in blue). The four panels are GPA groups. The x axis of each graph is parents' income.
The program helps those with lower GPAs more and also those with moderately high GPAs from low-income families.
We like these graphs. Many researchers will want to graph the ATE. Here it is:
. margins r.program, over(incomegrp hsgpagrp) predict(fix(program))
(output omitted)
. marginsplot, by(hsgpagrp) xlabels(0 4 8 12)
### Tell me more
Find out more about extended regression models for panel data.
ERMs are documented in their own manual. It covers syntax and usage in detail, a much deeper development of the concepts, the statistical formulation of ERMs, and much more. See the Stata Extended Regression Models Reference Manual.
The Stata Extended Regression Models Reference Manual also demonstrates ERMs on ordered probit models and interval-measured outcomes models. It demonstrates other combinations of endogenous(), select(), extreat(), and entreat().
Here are links to examples from the manual that demonstrate specific models:
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# Prim's algorithm
In computer science, Prim's algorithm is a greedy algorithm that finds a minimum spanning tree for a connected weighted undirected graph. This means it finds a subset of the edges that forms a tree that includes every vertex, where the total weight of all the edges in the tree is minimized. The algorithm was developed in 1930 by Czech mathematician Vojtěch Jarník and later independently by computer scientist Robert C. Prim in 1957 and rediscovered by Edsger Dijkstra in 1959. Therefore it is also sometimes called the DJP algorithm, the Jarník algorithm, or the Prim–Jarník algorithm.
Other algorithms for this problem include Kruskal's algorithm and Borůvka's algorithm. These algorithms find the minimum spanning forest in a possibly disconnected graph. By running Prim's algorithm for each connected component of the graph, it can also be used to find the minimum spanning forest.
Prim's algorithm starting at vertex A. In the second step, BD is chosen to add to the tree instead of AB arbitrarily, as both have weight 2. Afterwards, AB is excluded because it is between two nodes that are already in the tree.
## Description
### Informal
Initialize a tree with a single vertex, chosen arbitrarily from the graph. Grow the tree by one edge: of the edges that connect the tree to vertices not yet in the tree, find the minimum-weight edge, and transfer it to the tree. Repeat step 2 (until all vertices are in the tree).
### Technical
If a graph is empty then we are done immediately. Thus, we assume otherwise.
The algorithm starts with a tree consisting of a single vertex, and continuously increases its size one edge at a time, until it spans all vertices.
Input: A non-empty connected weighted graph with vertices V and edges E (the weights can be negative). Initialize: Vnew = {x}, where x is an arbitrary node (starting point) from V, Enew = {} Repeat until Vnew = V: Choose an edge {u, v} with minimal weight such that u is in Vnew and v is not (if there are multiple edges with the same weight, any of them may be picked) Add v to Vnew, and {u, v} to Enew Output: Vnew and Enew describe a minimal spanning tree
## Time complexity
Prim's algorithm has many applications, such as in the generation of this maze, which applies Prim's algorithm to a randomly weighted grid graph.
Minimum edge weight data structure Time complexity (total)
binary heap and adjacency list O((|V| + |E|) log |V|) = O(|E| log |V|)
Fibonacci heap and adjacency list O(|E| + |V| log |V|)
A simple implementation of Prim's, using an adjacency matrix graph representation and linearly searching an array of weights to find the minimum weight edge, to add requires O(|V|2) running time. Switching to an adjacency list representation brings this down to O(|V||E|), which is strictly better for sparse graphs. However, this running can be greatly improved further by using heaps to implement finding minimum weight edges in the algorithm's inner loop.
A first improved version uses a heap to store all edges of the input graph, ordered by their weight. This leads to an O(|E| log |E|) worst-case running time. But storing vertices instead of edges can improve it still further. The heap should order the vertices by the smallest edge-weight that connects them to any vertex in the partially constructed minimum spanning tree (MST) (or infinity if no such edge exists). Every time a vertex v is chosen and added to the MST, a decrease-key operation is performed on all vertices w outside the partial MST such that v is connected to w, setting the key to the minimum of its previous value and the edge cost of (v,w).
Using a simple binary heap data structure, Prim's algorithm can now be shown to run in time O(|E| log |V|) where |E| is the number of edges and |V| is the number of vertices. Using a more sophisticated Fibonacci heap, this can be brought down to O(|E| + |V| log |V|), which is asymptotically faster when the graph is dense enough that |E| is ω(|V|).
Demonstration of proof. In this case, the graph Y1 = Yf + e is already equal to Y. In general, the process may need to be repeated.
## Proof of correctness
Let P be a connected, weighted graph. At every iteration of Prim's algorithm, an edge must be found that connects a vertex in a subgraph to a vertex outside the subgraph. Since P is connected, there will always be a path to every vertex. The output Y of Prim's algorithm is a tree, because the edge and vertex added to tree Y are connected. Let Y1 be a minimum spanning tree of graph P. If Y1=Y then Y is a minimum spanning tree. Otherwise, let e be the first edge added during the construction of tree Y that is not in tree Y1, and V be the set of vertices connected by the edges added before edge e. Then one endpoint of edge e is in set V and the other is not. Since tree Y1 is a spanning tree of graph P, there is a path in tree Y1 joining the two endpoints. As one travels along the path, one must encounter an edge f joining a vertex in set V to one that is not in set V. Now, at the iteration when edge e was added to tree Y, edge f could also have been added and it would be added instead of edge e if its weight was less than e, and since edge f was not added, we conclude that
$w(f) \ge w(e).$
Let tree Y2 be the graph obtained by removing edge f from and adding edge e to tree Y1. It is easy to show that tree Y2 is connected, has the same number of edges as tree Y1, and the total weights of its edges is not larger than that of tree Y1, therefore it is also a minimum spanning tree of graph P and it contains edge e and all the edges added before it during the construction of set V. Repeat the steps above and we will eventually obtain a minimum spanning tree of graph P that is identical to tree Y. This shows Y is a minimum spanning tree.
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Q&A
# Filter Impedance Consideration
+2
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In a lot of textbooks, filters seem to be designed around a matching source and load impedance. However, If I have a filter stage between an antenna and an LNA, wouldn't I want the load impedance(input to the LNA) to be large with respect to the source(antenna) in order to not attenuate the signal even further?
I guess another way to phrase this is why do we care about maximum power transfer at this stage and not preserving as much of the signal amplitude as possible instead?
Why should this post be closed?
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Apart from the need to match impedances to prevent possibilities of signal reflections and the knock-on issue of signal nulls at your receiver LNA input, an antenna "expects" to be terminated in the "right" impedance in order to get best performance.
The ratio of E-field to H-field of a radio wave turns out to be volts per amp and that, as you probably know, is measured in ohms. In other words, the signal travelling towards your antenna experiences the "impedance of free space" and that is about 377 ohms. In effect your antenna is an impedance transformer converting a signal with an impedance of 377 ohms to something around 50 ohms (antenna type dependent). This effectively reduces the voltage by a ratio $\sqrt{\frac{377}{50}}$ if it were at all possible to measure voltage in free-space directly.
An antenna is like a fishing net - it has an effective surface area (despite it possibly looking just like a single wire) and, that "fishing net" is "capturing" both an electric field (volts per metre) and a magnetic field (amps per metre). Together, when multiplied you get watts per square metre hence, the antenna effective area is "capturing" watts (usually sub pico watts).
To convert that power into a signal-voltage, you need a resistor i.e. the load resistance required by the antenna to make it work most effectively.
Looking at things from another direction, 50 ohms (being a pretty normal standard for radio input and output impedance) does not generate a whole lot of thermal noise voltage for a given bandwidth and, this is important because, thermal noise can be a very significant factor in limiting how small a signal a particular radio design can effectively receive and demodulate. Keeping to a common impedance (i.e. 50 ohms or thereabouts) is a way of keeping signal-to-noise ratio as good as possible.
But, if you have a LNA that has 1 kohm input impedance (resistive) then there's absolutely no problem in using a filter that can convert impedance from around the 50 ohm mark up to 1 kohm. You wouldn't use resistors of course because that just wastes signal power but, you would use L-Pads, T-networks or $\pi$ networks to convert impedance without power loss.
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If I have a filter stage between an antenna and an LNA, wouldn't I want the load impedance(input to the LNA) to be large with respect to the source(antenna) in order to not attenuate the signal even further?
Not necessarily. What you want is maximum power transfer, not maximum voltage. Power is the limiting factor, and the domain where signal to noise ratio really needs to be considered.
If you have an antenna with 50 Ω output impedance and an LNA with 1 kΩ input impedance, for example, then much of the power received by the antenna will go unused, and signal to noise ratio will suffer as a result.
Consider the extremes. If the antenna is completely unloaded, then no power is delivered by it because the output current is 0. If the antenna is shorted, then no power is delivered by it because the voltage is 0. The maximum power transfer happens when the load impedance matches the source impedance, which is 50 Ω in this example.
In the case of a 1 kΩ LNA on a 50 Ω antenna, you want something in between that presents a 50 Ω load to the antenna, but drives the LNA with 1 kΩ impedance. When no power is lost, then such a converter would actually cause a higher output voltage by a factor of sqrt(1000 / 50) = 4.5. Put another way, you get a 4.5x bump in voltage seen by the LNA due to proper impedance matching. That's 13 dB better than with the original impedance mismatch.
The above assumes a perfect lossless converter, which of course doesn't exist. However, various L-C networks or even RF transformers can do better than 13 dB loss. Let's say your matching network has 3 dB loss. That means you're still 10 dB better off than with the original impedance mismatch.
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# [texhax] \section text in cross-refs
Sat Jul 16 06:43:25 CEST 2005
On Sat, July 16, 2005 2:47 am, Alan Litchfield said:
>
> Is there a package that will place \section{} text inside cross
> references?
nameref.sty does the job for you. You need to use \nameref instead of
\ref. nameref.sty is part of hyperref bundle.
Best regards
--
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Grain Reconstruction edit page
By grain reconstruction we mean the subdivision of the specimen, or more precisely the measured surface of the specimen, into regions of similar orientation which we then call grains. Note that there is no canonical definition of what is a grain. The grain reconstruction method that is default in MTEX is based on the definition of high angle grain boundaries which are assumed at the Mittelsenkrechten between neighbouring measurements whenever their misorientation angle exceeds a certain threshold. According to this point of view grains are regions surrounded by grain boundaries.
In order to illustrate the grain reconstruction process we consider the following sample data set
## Basic grain reconstruction
We see that there are a lot of not indexed measurements. For grain reconstruction, we have three different choices how to deal with these unindexed regions:
1. leave them unindexed
2. assign them to the surrounding grains
3. a mixture of both, e.g., assign small notindexed regions to the surrounding grains but keep large notindexed regions
By default, MTEX uses the first method.
The second parameter that is involved in grain reconstruction is the threshold misorientation angle indicating a grain boundary. By default, this value is set to 10 degrees.
All grain reconstruction methods in MTEX are accessible via the command calcGrains which takes as input an EBSD data set and returns a list of grain.
The reconstructed grains are stored in the variable grains. Note that also the notIndexed measurements are grouped into grains. This allows later to analyze the shape of these unindexed regions.
To visualize the grains we can plot its boundaries by the command plot.
## Filling notindexed holes
It is important to understand that MTEX distinguishes the following two situations
1. a location is marked as notindexed
2. a location does not occur in the data set
A location marked as notindexed is interpreted by MTEX as at this position, there is no crystal, whereas for a location that does not occur in the data set is interpreted by MTEX as: it is not known whether there is a crystal or not. Just to remind you, the later assumption is nothing special as it applies at all locations but the measurement points.
A location that does not occur in the data is assigned in MTEX to the same grain and phase as the closest measurement point - this may also be a notindexed point. Hence, filling holes in MTEX means to erase them from the list of measurements, i.e., instead of telling MTEX there is no crystal we are telling MTEX: we do not know what there is.
The extremal case is to say whenever there is a not indexed measurement we actually do not know anything and allow MTEX to freely guess what happens there. This is realized by removing all not indexed measurements or, equivalently, computing the grains only from the indexed measurements
We observe, especially in the marked grains, how MTEX fills notindexed regions and connects otherwise separate measurements to grains. As all information about not indexed regions were removed the reconstructed grains fill the map completely
Inside of grain B, there is a large not indexed region and we might argue that is not very meaningful to assign such a large region to some grain but should have kept it not indexed. In order to decide which not indexed region is large enough to be kept not indexed and which not indexed regions can be filled it is helpful to know that the command calcGrains also separates the not indexed regions into "grains" and we can standard grain functions like area or perimeter to analyze these regions.
We see that we have 1139 not indexed regions. A good measure for compact regions vs. cluttered regions is the quotient between the area and the boundary length. Lets, therefore, plot the "not indexed grains" colorized by this quotient
Regions with a high quotient are blocks which can be hardly correctly assigned to a grain. Hence, we should keep these regions as not indexed and only remove the not indexed information from locations with a low quotient.
We see that that all the narrow not indexed regions have been assigned to the surounding grains while the large regions have been left unindexed. Finally, the image with the raw EBSD data and on top the grain boundaries.
## Non convex data sets
By default MTEX uses the convex hull when computing the outer boundary for an EBSD data set. This leads to poor results in the case of non convex EBSD data sets.
We see that the grains badly fill up the entire convex hull of the data points. This can be avoided by specifying the option tight for the determination of the outer boundary.
|
{}
|
# Events Archive
## Juan Collar
#### New directions in coherent elastic neutrino-nucleus scattering
##### Physics Colloquium
July 2, 2020
Zoom | Thursday, 3:30 pm
## The Fuzzy Nanoparticle, the Fuzz, and the Water Slab
These three will meet with us via Zoom Friday at noon.
THey won't start their act until 12:15.
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglu
##### MRSEC Baglunch
June 26, 2020
Zoom | Friday, 12:00 pm
## The family that zooms together blooms together
#### ... well maybe
We can talk about the one-electron accelerator from the colloquium. They're having a naming contest : ). I think the electron lasts long enough in there to think up a name. My nomination: Atto boy.
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglu
##### MRSEC Baglunch
June 19, 2020
Zoom | Friday, 12:00 pm
## Sergei Nagaitsev
#### Grand challenges in Accelerator and Beam Physics
##### Physics Colloquium
June 18, 2020
Zoom | Thursday, 3:30 pm
## Michael Aizenman, Princeton
June 15, 2020
Zoom | Monday, 1:30 pm
## What does happen when flopping particles talk to each other?
Tune in Friday at noon to find out.
As usual, the revelations only come at 12:15, after we've shot the breeze a little bit.
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
June 12, 2020
Zoom | Friday, 12:00 pm
## Washington (Wati) Taylor
##### Theory Seminar
June 10, 2020
Zoom | Wednesday, 1:30 pm
## Ki-Seok Kim, POSTECH Korea
##### Theory Seminar
June 8, 2020
Zoom | Monday, 1:30 pm
## slow day at the baglunch
Please join is if you like. Bring thoughts, pictures, links, jokes, etc.
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
June 5, 2020
Zoom | Friday, 12:00 pm
## Carlos Wagner
#### Open Questions in Particle Physics
The Standard Model of Particle Physics is perhaps the most successful theory developed in the history of mankind. It explains a large diversity of physical phenomena, from what holds atoms and nuclei together, to the accurate prediction of the transformation (decay) of heavy particles into lighter ones, and of observables that have been measured with a precision of more than a part in a billion. Moreover, the discovery of the Higgs confirms the Standard Model explanation of the origin of the mass of elementary particles. This amazing theory, however, leaves many open questions. The most puzzling feature is that the Standard Model could have in principle answered most of them, but missed its chance to do so. I will discuss these missed opportunities, thereby describing the properties of this beautiful but complex theory. I will also briefly present the paths we have taken to solve these mysteries of nature by going beyond the Standard Model description.
##### Physics Colloquium
June 4, 2020
Zoom | Thursday, 3:30 pm
## K. Dane Wittrup, MIT
##### Molecular Engineering
June 3, 2020
ERC 161 | Wednesday, 2:00 pm
## Luping Yu, University of Chicago
#### New Ladder Molecules and their Electric and Optical properties
##### Chemistry
June 1, 2020
Zoom | Monday, 3:45 pm
## Gabriel Cuomo, EPFL
June 1, 2020
Zoom | Monday, 1:30 pm
## how molecular motors could make a droplet twirl
Doors open at noon for foolery
Main event at 12:15
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
May 29, 2020
Zoom | Friday, 12:00 pm
## Dmitri Talapini, University of Chicago
#### New chemistry of low-dimensional materials
##### Chemistry
May 26, 2020
Zoom | Tuesday, 3:45 pm
## Deadbeats in the actin chain gang
Fopic of the week:
Deadbeats in the actin chain gang
People trickle in around noon to exchange well wishes and news. Some bring jokes, videos....
An organized discussion begins at 12:15
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
May 22, 2020
Zoom | Friday, 12:00 pm
## Peter Littlewood and Vincenzo Vitelli
#### Dynamical phase transitions at many-body exceptional points
Spontaneous synchronization is at the core of many natural phenomena. Your heartbeat is maintained because cells contract in a synchronous wave; some bird species synchronize their motion into flocks; quantum synchronization is responsible for laser action and superconductivity. The transition to synchrony, or between states of different patterns of synchrony, is a dynamical phase transition that has much in common with conventional phase transitions of state – for example solid to liquid, or magnetism – but the striking feature of driven dynamical systems is that the components are “active”. Consequently quantum systems with dissipation and decay are described by non-Hermitian Hamiltonians, and active matter can abandon Newton’s third law and have non-reciprocal interactions. This substantially changes the character of many-degree-of-freedom dynamical phase transitions, and the critical phenomena in their vicinity, since the critical point is an “exceptional point” where eigenvalues coalesce.
We will illustrate this in two very different systems – a Bose-Einstein condensate of polaritons, and flocking of birds.
##### Physics Colloquium
May 21, 2020
Zoom | Thursday, 3:30 pm
## Cody Long, Cornell University
#### Constraints on Standard Model Constructions in F-theory
I will argue that the following three statements cannot all be true: (i) our vacuum is a type IIB /F-theory vacuum at moderate-to-large h^{1,1}, (ii) the \alpha^\prime-expansion is controlled via the supergravityapproximation, and (iii) there are no additional gauged sectorsfrom seven-branes. I will motivate this in large-scale ensemble studies in F-theory, and discuss the possible phenomenological consequences.
##### Theory Seminar
May 20, 2020
Zoom | Wednesday, 1:30 pm
## David Mazziotti, University of Chicago
#### Some Recent Advances in Quantum Computing for Quantum Chemistry
Quantum computing has the potential to transform our ability to predict chemistry from quantum mechanics. In this talk I will discuss some recent advances in quantum computing for quantum chemistry in my research group.
##### Chemistry
May 18, 2020
Zoom | Monday, 3:45 pm
## Chong Wang, Perimeter Institute
#### A theory of deconfined pseudo-criticality
It has been proposed that the deconfined criticality in (2+1)d - the quantum phase transition between a Neel anti-ferromagnet and a valence-bond-solid (VBS) - may actually be pseudo-critical, in the sense that it is a weakly first-order transition with a generically long correlation length. The underlying field theory of the transition would be a slightly complex (non-unitary) fixed point as a result of fixed points annihilation. This proposal was motivated by existing numerical results from large scale Monte-Carlo simulations as well as conformal bootstrap. However, an actual theory of such complex fixed point, incorporating key features of the transition such as the emergent SO(5)symmetry, is so far absent. Here we propose a Wess-Zumino-Witten (WZW) nonlinear sigma model with level k=1, defined in 2+ϵ dimensions, with target space S^(3+ϵ) and global symmetry SO(4+ϵ). This gives a formal interpolation between the deconfined criticality at d=3 and the SU(2)_1 WZW theory at d=2 describing the spin-1/2 Heisenberg chain. The theory can be formally controlled, at least to leading order, in terms of the inverse of the WZW level 1/k. We show that at leading order, there is a fixed point annihilation at d*≈2.77, with complex fixed points above this dimension including the physical d=3 case. The pseudo-critical properties such as correlation length, scaling dimensions and the drifts of scaling dimensions as the system size increases, calculated crudely to leading order, are qualitatively consistent with existing numerics.
May 18, 2020
Zoom | Monday, 1:30 pm
## Touch base
Feel very free to bring an amusing tidbit or video, or zoom trick or google drive trick, or hat trick or Comment
See you at noonish tomorrow
As you saw from last week, you don't have to wait until I arrive and you can stay after I leave.
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
May 15, 2020
Zoom | Friday, 12:00 pm
## Wen Wei Ho, Harvard
May 11, 2020
Zoom | Monday, 1:30 pm
## a gas that thinks for itself
Drift in around noon, show-and-tells are encouraged.
12:15 is the main event.
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
May 8, 2020
Zoom | Friday, 12:00 pm
## Jeremias Aguilera Damia, Centro Atomico Bariloche
May 4, 2020
Zoom | Monday, 1:30 pm
## Dmitry Krotov, IBM Research
#### A Few Ideas from Neurobiology and Physics for Unsupervised Learning
Abstract
Despite great success of deep learning, a question remains to what extent the computational properties of deep neural networks are similar to those of the human brain, and how the biological systems can further inform design of new algorithms for machine learning. In this talk, I will present two ideas from neurobiology: local learning motivated by Hebbian plasticity and sparse expansive network motifs present in olfactory systems of many organisms. These ideas can be used for designing a learning algorithm and network architectures that make it possible to learn powerful representations in an unsupervised way - directly from unlabeled data. Learning these representations does not require a backpropagation training. Instead, it utilizes local biologically plausible layer-wise learning, which is significantly faster than the backpropagation training. The utility of these algorithms will be demonstrated on classification and similarity search and retrieval tasks. I will also describe a simple dynamical system of particles moving under repulsive forces that captures an intuition behind the proposed learning algorithm.
##### JFI Special Seminar
May 1, 2020
Zoom | Friday, 1:00 pm
## Self Introductions
#### Origami Bit
Bring an unfolded sheet of office paper and you too can make the Origami Bit, in just four folds. A little opener before the main event.
If you want to play, bring a picture to show about a science thing that you like, and tell who you are and what group you're in. Put those things on your picture, too. Please keep this self-introduction to a minute or less
The time is 12:00, to shoot the breeze, tell jokes or news, and eat
Then at 12:15 we can also listen to each other's self introductions.
For the Zoom link, please signup to the baglunch mailing list: https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
May 1, 2020
Zoom | Friday, 12:00 pm
## On Growth and Form
#### The coffee stain, revisited
Meet and greet at noon
at Zoom
Main event: 12:15
https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
April 24, 2020
Zoom | Friday, 12:00 pm
## Getting under the skin of non-Hermitian skin modes
Self assembly: noon at Zoom
(Feel free to arrive early; I will aim to be there before noon.)
Self actuation: 12:15
https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
April 17, 2020
Zoom | Friday, 12:00 pm
## Mikhail Shapiro, California Institute of Technology
##### Molecular Engineering
April 15, 2020
ERC 161 | Wednesday, 2:00 pm
## Touch base…
#### with luck, an old friend or two will come and say hi
Bring food to Zoom at 12:00
Bring something funny or cute to be screen-shared if you have it.
https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
April 10, 2020
Zoom | Friday, 12:00 pm
## Gabriel Orebi Gann, UC Berkeley
##### Physics Colloquium
April 9, 2020
KPTC 106 | Thursday, 3:30 pm
#### the evolution of mutation rates
Bring food to Zoom at 12:00
Bring something funny or cute to be screen-shared
Hear about the cross-eyed genes at 12:15
https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
April 3, 2020
Zoom | Friday, 12:00 pm
## Kang Kuen Ni, Harvard University
##### Physics Colloquium
April 2, 2020
KPTC 106 | Thursday, 3:30 pm
## Slack Talk
https://lists.uchicago.edu/web/info/mrsec-baglunch"
##### MRSEC Baglunch
March 27, 2020
Zoom | Friday, 12:00 pm
## Zoom Lunch
#### Bring a Tidbit
Hi everyone -- It would be good to see you after a vertiginous week. By this time you might have a good joke or picture or web site to show. Meanwhile, the MRSEC leaders were busy with last Monday's virtual reverse site visit, and Margaret Gardel agreed to give us a brief update
https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
March 20, 2020
Zoom | Friday, 12:00 pm
## Steven Cundiff, Department of Physics, University of Michigan
#### Optical Multidimensional Coherent Spectroscopy of Semiconductor Nanostructures
The concept of multidimensional Fourier transform spectroscopy originated in NMR where it enabled the determination of molecular structure. The key concept is to correlate what happens during multiple time periods between pulses by taking a multidimensional Fourier transform. The presence of a correlation, which is manifest as an off-diagonal peak in the resulting multidimensional spectrum, indicates that the corresponding resonances are coupled. Migrating multidimensional Fourier transform spectroscopy to the optical regime is difficult because phases are critical. I will give an introduction to optical two-dimensional coherent spectroscopy, using an atomic vapor as simple test system, but also show unexpected results due to atomic interactions. I will then present our use of it to study optical resonances in semiconductor nanostructures including quantum wells, self-organized quantum dots and colloidal nanocrystals.Host: Christopher Melnychuk via email at cmelnychuk@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas by email at bthomas@uchicago.edu or at 2-7156.
##### The Tuesday JFI Seminar
March 17, 2020
GCIS W301 | Tuesday, 3:45 pm
## Alexander Eychmüller,Technische Universität Dresden
#### Chemistry and physics of nanocrystals, 2D materials and aerogels: Review of my group’s current research
##### Chemistry
March 13, 2020
Kent 120 | Friday, 1:45 pm
## Peko Hosoi, MIT
##### Physics Colloquium
March 12, 2020
KPTC 106 | Thursday, 3:30 pm
#### A Laboratory Analog of the Parker Spiral
Many rotating stars have magnetic fields that interact with the winds they produce. The Sun is no exception. The interaction between the Sun's magnetic field and the solar wind gives rise to the heliospheric magnetic field -- a spiraling magnetic structure, known as the Parker Spiral, which pervades the solar system. In this talk, I will report the creation of a laboratory model of the Parker spiral system based on a rapidly-rotating plasma magnetosphere and the measurement of its global structure and dynamic behavior. This laboratory system exhibits regions where the plasma flows evolve similarly to many magnetized stellar winds. We observe the advection of magnetic field into an Archimedean spiral and the ejection of quasi-periodic plasma blobs into the stellar outflow, which mimics the observed plasmoids that fuel the slow solar wind. The Parker spiral system mimicked in the laboratory can be used for studying solar wind dynamics in complementary fashion to conventional space missions such as NASA's Parker Solar Probe mission.
##### Computations in Science
March 11, 2020
KPTC 206 | Wednesday, 12:15 pm
## Qian Chen, Department of Chemistry, University of Illinois at Urbana-Champaign
#### Cancelled
I will discuss my group’s recent progress on applying low-dose liquid-phase TEM to synthetic and biological systems. In the first system, we directly image the otherwise elusive crystallization pathways of nanosized colloids into superlattices, where the discreteness and multi-scale coupling effects complicate the free energy landscape and the application forms of the final superlattices. We find that there exist similarities to the prevalent model system of micron-sized colloids, such as a non-classical two-step crystallization pathway, and an agreement with the capillary wave theory. But there are also differences, in particular, a universal layer-by-layer growth mode that we observe consistently for diverse nanoparticle shapes. Single particle tracking, trajectory analysis, and simulations combined unravel the energetic and kinetic features rendering this crystal growth mode possible and universal at the unexplored nanoscale, enabling advanced crystal engineering. In the second system, we sandwich and capture moving membrane proteins in their native lipid and liquid environment at nm resolution. The proteins exhibit real-time “fingering” fluctuations, which we attribute to dynamic rearrangement of lipid molecules wrapping the proteins. The conformational coordinates of protein transformation obtained from the real-space movies are used as inputs in our molecular dynamics simulations, to verify the driving force underpinning the function-relevant fluctuation dynamics. This platform invites an emergent theme of structural biophysics as we foresee. Host: Bozhi Tian via email at btian@uchicago.edu or at 2-8749. Persons with a disability who may need assistance please contact Brenda Thomas by email at bthomas@uchicago.edu or at 2-7156.
##### The Tuesday JFI Seminar
March 10, 2020
GCIS W301 | Tuesday, 3:45 pm
## Chen Yang, Boston University
#### Design Photoacoustic Nanomaterial Interface to Fire and Reconnect Neurons
##### Chemistry
March 9, 2020
Kent 120 | Monday, 3:45 pm
## Ohyun Kwon, UCLA
#### Beyond Phosphine Organocatalysis
##### Chemistry
March 9, 2020
Kent 120 | Monday, 3:45 pm
## Burak Guzelturk, Argonne National Laboratory
#### Monitoring Photoinduced Structural Responses in Functional Photoactive Materials
##### Chemistry
March 9, 2020
GCIS E223 | Monday, 2:30 pm
## Jordan Cotler - Stanford University
#### Emergent unitarity in de Sitter from matrix integrals
I will discuss Jackiw-Teitelboim gravity with positive cosmological constant as a model for de Sitter quantum gravity. We will explore the quantum mechanics of the model, and show that there is a Hilbert space of asymptotic states at past and future infinity, along with an S-matrix encoding infinite-time evolution. This evolution is not unitary, although it is unitary on a subspace of asymptotic states, up to non-perturbative corrections. This non-unitary is due to universes which evolve into a crunch singularity. We also study topology-changing processes including the nucleation of baby universes. There is significant evidence that this 1+1 dimensional model is dual to a 0+0 dimensional matrix integral. We find that the Hilbert space and time evolution comprising the 1+1D de Sitter physics arise rather robustly from universal properties of the level repulsion of eigenvalues in the random matrix theory.
March 9, 2020
MCP 201 | Monday, 1:30 pm
## Allison Narayan, University of Michigan
#### Biocatalysis and complex molecule synthesis
##### Chemistry
March 6, 2020
Kent 120 | Friday, 1:45 pm
## Redefining the landscape - Women in STEM
Redefining the landscape - Women in STEM is an upcoming PSD & PME exhibit and speaker series featuring narratives and images of the women who are shaping STEM.
##### Molecular Engineering
March 5, 2020
ERC Atrium | Thursday, 3:00 pm
## Kai Zhang, PhD, Biochemistry UIUC
#### Bidirectional optical control of neurotrophin signaling during cell differentiation and embryonic development
The neurotrophin signaling pathway regulates a wide spectrum of cellular functions such as cell survival, proliferation, differentiation, and apoptosis. It also plays a key role in cell fate determination during embryonic development. Evidence suggests that the signaling output of the neurotrophic pathway varies with its temporal kinetics. However, a quantitative delineation of signaling kinetics is limited due to a lack of tools that allows precise control of the neurotrophic signaling in time and space. Non-neuronal optogenetics, an emerging technology that utilizes light to control intracellular signaling pathways, offers an alternative solution to address this challenge. In this presentation, I will introduce optogenetic systems recently developed in our laboratory that allow for reversible and bidirectional optical control of the neurotrophin signaling pathway in intact cells and in developing Xenopus laevis embryos. I will also discuss the limitations of current non-neuronal optogenetics and update you with current progress in the field in overcoming these limitations.
##### Biophysical Dynamics
March 3, 2020
GCIS W301 | Tuesday, 12:00 pm
## Moungi Bawendi, Massachusetts Institute of Technology
#### Playing with excitations and light: Perovskite nanoparticles as a potential source of quantum light, and Short Wave Infrared In-Vivo Bio-imaging.
##### Chemistry
March 2, 2020
Kent 120 | Monday, 3:45 pm
#### S-matrix chaos and thermodynamics
March 2, 2020
MCP 201 | Monday, 1:30 pm
## Eliot Kapit, Colorado School of the Mines
#### Noise-Tolerant Quantum Speedups in Quantum Annealing Without Fine Tuning
Quantum annealing is a powerful alternative model for quantum computing, which can succeed in the presence of environmental noise even without error correction. However, despite great effort, no conclusive proof of a quantum speedup (relative to state of the art classical algorithms) has been shown for these systems, and rigorous theoretical proofs of a quantum advantage generally rely on exponential precision in at least some aspects of the system, an unphysical resource guaranteed to be scrambled by random noise. In this work, we propose a new variant of quantum annealing, called RFQA, which can maintain a scalable quantum speedup in the face of noise and modest control precision. Specifically, we consider a modification of flux qubit-based quantum annealing which includes random, but coherent, low-frequency oscillations in the directions of the transverse field terms as the system evolves. We show that this method produces a quantum speedup for finding ground states in the Grover problem and quantum random energy model, and thus should be widely applicable to other hard optimization problems which can be formulated as quantum spin glasses. Further, we show that this speedup should be resilient to two realistic noise channels ($1/f$-like local potential fluctuations and local heating from interaction with a finite temperature bath), and that another noise channel, bath-assisted quantum phase transitions, actually accelerates the algorithm and may outweigh the negative effects of the others. The modifications we consider have a straightforward experimental implementation and could be explored with current technology
##### JFI Special Seminar
February 28, 2020
GCIS E223 | Friday, 1:00 pm
## Alberto Fernandez-Nieves, Georgia Tech and University of Barcelona
#### Active nematics & topological defects in curved and flat space
We will discuss recent results with active nematics confined to either toroidal or flat space. We will first describe how curvature affects defect arrangement on tori. We will show that despite the intrinsic activity and out-of-equilibrium character of the system, there are still remnants of the expected curvature-induced defect unbinding predicted for nematics in their ground state. Activity, however, augments the behavior leading to unexpected defect distributions. We will then focus on defect orientation and show that on flat space, there is short-range orientational correlations without long-range orientational order.
Friday, 28 FEBRUARY 12:00 noon: conversation over baglunch
12:15 seminar begins
##### MRSEC Baglunch
February 28, 2020
GCIS E123 | Friday, 12:00 pm
## Eric Sharpe, Virginia Tech
February 26, 2020
MCP 201 | Wednesday, 1:30 pm
## Denis Bartolo, ENS Lyon
#### Flocks and crowds: a Gulliver trave
For centuries, applying an external pressure difference has remained the only solution to flow a liquid in a pipe. Over the last ten years, by engineering soft materials from self-propelled units, we have learned how to drive fluids from within. In the first part of my talk I will show how to assemble spontaneously flowing liquids from interacting colloidal robots. I will then show how to infer the hydrodynamics of these active fluids from the sole inspection of their fluctuation spectra. In the second part of my talk I will show that the same concepts and tool can be effectively use to account for the flows of pedestrian crowds walking on the streets of a windy city.
##### Computations in Science
February 26, 2020
KPTC 206 | Wednesday, 12:15 pm
## Dominika Zgid, Department of Chemistry, University of Michigan
#### Towards Accurate Quantum-Mechanical Calculations beyond Density Functional Theory
I will present a detailed discussion of self-energy embedding theory (SEET) which is a quantum embedding scheme allowing us to describe a chosen subsystem very accurately while keeping the description of the environment at a lower cost. SEET is applied to molecular examples where commonly our chosen subsystem is made out of a set of strongly correlated orbitals while the weakly correlated orbitals constitute an environment. Such a self-energy separation is very general and to make this procedure applicable to multiple systems a detailed and practical procedure for the evaluation of the system and environment self-energy is necessary. I will focusing our discussion on many practical implementation aspects such as the choice of best orbital basis, impurity solver, and many steps necessary to reach chemical accuracy.
Finally, on a set of carefully chosen molecular and solid examples, I will demonstrate that SEET, which is a controlled, systematically improvable Green's function method can be as accurate as established wavefunction quantum chemistry methods. Host: David Mazziotti via email damazz@uchicago.edu or at 4-1762. Persons with a disability who may need assistance please contact Brenda Thomas by email at bthomas@uchicago.edu or at 2-7156.
##### The Tuesday JFI Seminar
February 25, 2020
GCIS W301 | Tuesday, 3:45 pm
## Glenn Wagner, Oxford University
#### How to realize the quantum Hall effect in curved space in strained graphene
The quantum Hall effect in curved space has been the subject of many theoretical investigations in the past, but devising a physical system to observe this effect is hard. Previous work has indicated that electronic excitations in strained graphene realize Dirac fermions in curved space in the presence of a background pseudo-gauge field, providing an ideal playground for this. However, the absence of a direct matching between a numerical, strained tight-binding calculation of an observable and the corresponding curved space prediction has hindered realistic predictions. In this talk, I will sketch how to derive the low-energy Hamiltonian from the tight-binding model and map it to the curved-space Dirac equation. Using a strain profile that produces a constant pseudo-magnetic field and a constant curvature, one can compute the Landau level spectrum with real-space numerical tight-binding calculations and find excellent agreement with the prediction of the quantum Hall effect in curved space. I will conclude by discussing experimental schemes for measuring this effect.
February 25, 2020
MCP 201 | Tuesday, 1:30 pm
## Sarah Reisman, California Institute of Technology
#### Necessity is the Mother of Invention: Natural Products and the Chemistry They Inspire
##### Chemistry
February 24, 2020
Kent 120 | Monday, 3:45 pm
## Andy Lucas, Stanford University
#### Mathematics of operator growth in quantum many-body systems
The Lieb-Robinson theorem is a classic result in mathematical physics which proves that in a quantum system with local interactions, the commutators of local operators essentially vanish outside of a “light cone” with an emergent, finite velocity. This result has numerous applications, from bounding classical simulatability of quantum systems to constraining entanglement growth, and many-body operator growth and chaos. In this talk, I will present new frameworks for understanding operator growth and chaos in quantum many-body systems, both with local and without local interactions, which provide qualitative improvements over existing techniques. Using these techniques, I will prove two previously open problems: (1) in spin chains with interactions that fall off with distance faster than 1/r^3, commutators of local operators can be made arbitrarily small outside of a “linear light cone” which grows at a finite velocity, just as in local systems; (2) the scrambling time for an operator to grow large in the Sachdev-Ye-Kitaev model of N fermions grows no slower than log N, when N is large but finite. These non-perturbative bounds on the many-body Lyapunov exponent are within a factor of 2 of previously calculated exponents in perturbation theory in 1/N.
February 24, 2020
MCP 201 | Monday, 1:30 pm
## Hill Harman, University of California - Riverside
#### Boron-Doped Acenes for the Redox Activation of Small Molecules
##### Chemistry
February 21, 2020
Kent 120 | Friday, 1:45 pm
## Suri Vaikuntanathan, University of Chicago
#### Robustness in minimal models of biochemical oscillators
Biochemical oscillations are ubiquitous in biology and allow organisms to properly time their biological functions. Two biologically relevant observables in these biochemical oscillator circuits are the coherence and time period of oscillations. In this talk, I will discuss minimal Markov state models of non-equilibrium biochemical networks that support oscillations. In particular, I will discuss how a high energy consumption budget can make these quantities robust in a variety of settings.
##### Computations in Science
February 19, 2020
KPTC 206 | Wednesday, 12:15 pm
## Alex Spokoyny UCLA
#### Boron Cluster Building Blocks and Synthetic Reagents
##### Chemistry
February 17, 2020
Kent 120 | Monday, 3:45 pm
###### Mon 17
February 17, 2020
MCP 201 | Monday, 1:30 pm
## Too much semiannual amplitude in the daily temperature
#### Who ordered that?
Really talk about the weather: 12:15
##### MRSEC Baglunch
February 14, 2020
GCIS E123 | Friday, 12:00 pm
## William Lanouette, Atomic Heritage Expert and Author
##### Physics Colloquium
February 13, 2020
KPTC 106 | Thursday, 3:30 pm
## Jianfeng Lu, Duke University
#### Coordinate-Descent Full Configuration Interaction
The leading eigenvalue problems arise in many applications. When the dimension of the matrix is super large, such as for applications in quantum many-body problems, conventional algorithms become impractical due to computational and memory complexity. In this talk, we will describe some recent works on new approaches for the leading eigenvalue problems based on randomized and coordinate-wise methods. In particular, we will introduce the coordinate-descent full configuration interaction for quantum chemistry problems.
(joint work with Yingzhou Li and Zhe Wang).
##### JFI Special Seminar
February 13, 2020
GCIS W301 | Thursday, 1:30 pm
## Marko Lončar, Harvard
#### New Opportunities with Old Optical Materials
Lithium niobate (LN) is an “old” material with many applications in optical and microwave technologies, owing to its strong electro-optic (EO) coefficient, second order nonlinearity, and piezoelectricity. Conventional - discrete - LN components, the workhorse of the optoelectronic industry for many decades, are reaching their limits, however. I will discuss our efforts aimed at the development of integrated LN photonic platform aimed at applications in optical communications (classical and quantum) and microwave photonics. Examples include high-performance (EO) modulators, EO and Kerr frequency combs, ad frequency converters. Diamond is another “old” material with remarkable properties! It is transparent from the ultra-violet to infrared, has a high refractive index, strong optical nonlinearity and a wide variety of light-emitting defects of interest for quantum communication, computation and sensing. I will discuss our recent efforts focused on the control of silicon vacancy color center using nanomechanical devices including free-standing nanobeams and surface acoustic waves.
##### Molecular Engineering
February 12, 2020
ERC 161 | Wednesday, 2:00 pm
## Jeremy England, GSK AI
#### Cancelled
##### Computations in Science
February 12, 2020
KPTC 206 | Wednesday, 12:15 pm
## Yun Liu, University of Illinois
#### New Functions in Organic Materials through Molecular Designs
##### Chemistry
February 11, 2020
Kent 120 | Tuesday, 1:45 pm
## Matthew Good, PhD, Cell & Devel Biol and Bioengineering, Upenn
#### Sequence Determinants & Fidelity of RGG Domain Condensation to Form Membraneless Organelles
Coacervation of intrinsically disordered proteins (IDPs) commonly underlies formation of membraneless organelles, which compartmentalize molecules intracellularly in the absence of a lipid membrane. However, to date, protein coacervation cannot be predicted from primary sequence. Using a combination of predictive coarse-grained modeling, in vitro characterization and in vivo expression we characterized the chemical determinants of IDP phase separation for the disordered RGG domain from the scaffold protein LAF-1. We identified regions that have high contact probability and deletion of which significantly disrupt protein condensation in vitro and in vivo. We designed sequence variants to investigate the role of charge patterning on phase behavior and found that shuffled sequences with greater charge segregation dramatically enhances propensity to phase separate. Mutation of tyrosine to phenylalanine, or arginine to lysine, dramatically perturbed RGG phase separation, and all-atom models highlight the special role of arginine in sp2-pi interactions. Building off of this platform we are identifying chemical principles that regulate the fidelity of selective protein coacervation and prevent inappropriate mixing of disordered proteins. Finally, we demonstrate the utility of RGG-based constructs for cellular engineering. By layering enzymatic and optical regulatory handles to regulate protein solubility and valency, we can control protein condensation to form synthetic membraneless organelles in cells. Together, these studies identify key biophysical principles of RGG domain condensation, including conserved motifs, critical residues and charge patterning, while also advancing a predictive framework to identify and design sequences that phase separate.
##### Biophysical Dynamics
February 11, 2020
GCIS W301 | Tuesday, 12:00 pm
## Eric Kool, Stanford University
#### Designer Nucleotides and Molecular Probes of DNA Repair
##### Chemistry
February 10, 2020
Kent 120 | Monday, 3:45 pm
## Sasha Migdal, New York University
#### Mathematics of operator growth in quantum many-body systems
The loop equations in turbulence are reviewed, both theory and comparison with numerical experiments and some physical experiments as well. We propose the model of 3D Turbulent statistics as String Theory on the phase boundaries of the 3D Ising model. Both mathematical justification from the Euler and Helmholtz equations and the resulting physical properties are discussed, time permitting.
February 10, 2020
MCP 201 | Monday, 1:30 pm
## Capturing the texture of a fracture by quantitative measures
Mangiamo 12:00
Parliamo 12:15
##### MRSEC Baglunch
February 7, 2020
GCIS E123 | Friday, 12:00 pm
## Meg Urry, Yale University
#### 2020 Equity, Diversity and Inclusion Colloquium
##### Physics Colloquium
February 6, 2020
GCIS W301 | Thursday, 3:30 pm
## Xufeng Zhang, Center for Nanoscale Materials, Argonne National Laboratory
#### Experimental Observation of an Exceptional Surface in Hybrid Magnonic Systems
Exceptional points (EPs) are singularities of eigen-energies in a non-Hermitian system that is open to the environment. Intriguing phenomena have been previously observed around EPs, including exceptional sensitivity, unidirectional signal propagation, etc. However, these demonstrations of EPs are limited to zero-dimensional points and one-dimensional lines. In this talk, I will show the first experimental realization of an exceptional surface (ES) – a continuous three-dimensional surface of EPs. This is achieved by constructing a four-dimensional synthetic space, taking advantage of the multiple independent tuning parameters of a cavity magnon polariton system. Magnon polaritons are hybrid excitations of electromagnetic waves and spin waves, which have recently emerged as a promising candidate for coherent information processing. The observed ES in the magnon polariton system can further coalesce into an exceptional saddle point in the four-dimensional parameter space, which exhibits novel complex anisotropic behaviors. This work provides a new pathway to engineer non-Hermitian systems, and opens up new application opportunities such as robust mode conversion and high-sensitivity sensing. Host: Peter Littlewood, 4-9879 or via email to littlewood@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### JFI Special Seminar
February 5, 2020
GCIS W301 | Wednesday, 2:00 pm
## Justin Burton, Emory University
#### Intermittent Dynamics and "Turbulence" in a Many-Body System
Complex systems are known to exhibit emergent properties that are missing on the constituent level. An example is the appearance of intermittent transitions between distinct dynamical states. Using a levitated, quasi-2D layer of charged microparticles, our recent experiments (Gogia et al., PRL, 2017) showed that a nonequilibrium, many-body system can display intermittent dynamics by switching between an ordered, crystalline state and a gas-like, excited state. The emergent dynamics are a direct consequence of coupling between the inertial dynamics, structural disorder induced by particle size variation, and external noisy forcing. The behavior can be reproduced is a simulation with as little as 50 particles. The key lies in a separation of energy scales. Energy pumped into one degree of freedom will eventually couple non-linearly to other excitable modes and thermalize the system. The behavior bears a striking resemblance to the transition to turbulence in pipe flow, where increasing the flow velocity leads to intermittent "puffs" of turbulence. This transition also depends sensitively on disorder through the roughness of the pipe walls. In analogy to the Reynolds number, we are able to describe our system through a simplified set of equations and a single dimensionless number characterizing the ratio of external forcing to dissipation. This analogy may help identify the minimal ingredients for observing such intermittent, turbulent dynamics in other discrete systems.
##### Computations in Science
February 5, 2020
KPTC 206 | Wednesday, 12:15 pm
## Tobin Marks, Northwestern University
#### Soft Matter-Hard Matter Synergy for Flexible Electronics and Solar Cells
##### Chemistry
February 5, 2020
GCIS W301 | Wednesday, 12:00 pm
## Mufan Li, University of California Berkeley
#### Designing Electrocatalytic Sites at the Atomic Level
##### Chemistry
February 4, 2020
ERC 401 | Tuesday, 3:15 pm
## Rebecca Kramer-Bottiglio, Yale University
#### Programmable Composites for Stiffness-Changing and Shape-Shifting Soft Robots
Soft robots have the potential to adapt their morphology, properties, and behavioral control policies towards different tasks or changing environments. This adaptive capability is often inspired by biological systems. For instance, humans can transition between forceful and gentle tasks by controlling the stiffness of skeletal joints through co-contraction of antagonistic sets of muscles. In another example, the remarkably dexterous motion achieved by skeleton-free animal parts such as elephant trunks, octopus arms, and human tongues is attributed to selective contraction of layers of uni-directional muscle fibers. During this talk, I will present recent work towards programmable composites that address variable stiffness properties and variable trajectory motions inspired by these capabilities in animals. First, I will present a particulate additive designed to undergo a repeatable solid-liquid phase change within a polymeric matrix and demonstrate its use to achieve unprecedented changes in bulk material stiffness and elasticity. The solid-liquid phase change of low-melting-point metallic inclusions allows a composite to dramatically adjust its mechanical response, as demonstrated in two matrix materials: a thermoset epoxy and a silicone elastomer. Second, I will describe a soft composite lamina comprised of an elastic matrix with uni-directionally embedded inextensible fibers and an adhesive backing, which was inspired by soft body control strategies using fiber- architectures. In contrast to existing soft actuators with fixed deformation trajectories, this composite is simply placed on the surface of an inflatable body to govern its deformation trajectory, can be re-arranged in-situ to change this trajectory, and is created using a high throughput, automated manufacturing process.
##### Molecular Engineering
February 4, 2020
ERC 161 | Tuesday, 11:00 am
## Tobin Marks, Northwestern University
#### Surface Science Meets Homogeneous Catalysis. Surfaces as Unique Activators and Ligands
##### Chemistry
February 3, 2020
Kent 120 | Monday, 3:45 pm
## Pallab Goswami, Northwestern University
#### Topology of three-dimensional Dirac semimetals: a tale of SO(5) monopoles and Hopf defects
Three-dimensional massless Dirac fermions can describe the dynamics of ultra-relativistic particles, as well as the low-energy physics of emergent, gapless excitations for many solid-state systems that preserve spatial-inversion and time-reversal symmetries. Such solid-state materials are collectively known as Dirac semimetals, which support linear touching of two Kramers-degenerate bands at isolated points in momentum space. For example, the massless Dirac fermions can arise as stable excitations in Cd3As2 and Na3Bi, and also as unstable excitations at topological quantum phase transitions in bismuth-antimony alloys and indium doped bismuth selenide.
What are the bulk topological invariants of Dirac semimetals? Are the surface states of stable Dirac semimetals topologically protected? In this talk, I will provide affirmative answers to these open questions, by considering minimal models of band-structures for Dirac semimetals. These models generally involve a five-component vector field defined in momentum space, whose amplitude vanishes at Dirac points. By addressing the nature of non-Abelian SO(5) Berry’s vector potential, I will show that the topological properties of unstable and stable Dirac semimetals can be respectively understood in terms of Hopf defects and a pair of monopole and anti-monopole. I will discuss the absence of helical Fermi arcs, the precise nature of surface states, and the bulk-boundary correspondence for stable Dirac semimetals, and additional experimental consequences for many materials.
February 3, 2020
MCP 201 | Monday, 1:30 pm
## Tyrel McQueen, John Hopkins University
#### The Materials Synthesis Frontier
Materials chemistry by design is the rational prediction and creation of functional materials with defined properties. Its goal is to meet current and future societal needs for better or more complex materials, from biocompatible materials in medicine to lightweight alloys for space applications and energy generation, storage, and transport. Unfortunately, materials chemistry has lagged other sub-fields in an extremely critical area: the ability to selectively make and break bonds in the solid state. This is due to limited synthetic methodology and method development. True materials by design cannot be achieved until reliable synthetic capabilities are developed that can actually produce the specified materials. In this talk, I will highlight the progress being made in such synthesis by design, with a particular focus on quantum materials – a class of material in which quantum phenomena not only underlie but are ‘writ large’ across macroscopic materials. Examples will range from utilizing materials discovery to test theories of the high photovoltaic performance of halide perovskites, to the development of exfoliatable quantum magnets that reveal new phenomenology as a consequence of the dimensional reduction.
##### Chemistry
January 31, 2020
Kent 120 | Friday, 1:45 pm
## Jessie Shelton, UIUC
#### Exploring the Cosmologies of Dark Sectors
One generic scenario for the dark matter of our universe is that it resides in a hidden sector: it talks to other dark fields more strongly than it talks to the Standard Model. This class of models is well-motivated by high-scale theories such as string theory, can easily accomodate the null results observed in terrestrial detectors to date, and --perhaps most importantly -- can produce a wide variety of interesting signals in both terrestrial and astrophysical observables. I'll walk through some minimal cosmological origin stories for such dark sectors and explore their consequences for where and how we might look for the footprints of dark states today.
##### Physics Colloquium
January 30, 2020
KPTC 106 | Thursday, 3:30 pm
## Alex Levine, UCLA
#### Cancelled
##### Computations in Science
January 29, 2020
KPTC 206 | Wednesday, 12:15 pm
## Jens Koch, Northwestern University
#### Intrinsically Protected Superconducting Qubits: From Concepts to Realization
The transmon qubit owes its success to robust protection from the detrimental effects of 1/f charge noise, and to its relative simplicity as one of the smallest anharmonic superconducting circuits. However, the transmon remains fully sensitive todepolarization processes, making T1 limitations an
ongoing challenge. Several proposals exist for achieving universal protection from both depolarization and dephasing in superconducting qubits - among them the 0-π qubit and the current mirror qubit. In this talk, I will present the overarching concepts of disjoint-support wavefunctions and robust ground state degeneracy, and illustrate how they emerge in concrete circuits. Following a discussion of spectra and coherence-times estimates for the 0-π qubit, I will address some of the new challenges associated with simulating and operating protected qubits. Finally, I will discuss new data on the first experimental realization of the 0-π qubit in the Houck lab. Host: Aashish Clerk, aaclerk@uchicago.edu or by phone at 4-2943 For more information please contact Alisha Manning-Beard at amannie@uchicago.edu or by phone at 4-2351.
##### Molecular Engineering
January 29, 2020
ERC 201B | Wednesday, 11:00 am
## Joel Yuen-Zhou, Department of Chemistry, University of Calfornia-San Diego
#### Polariton Chemistry: Molecules in Optical Cavities
Organic molecules interact strongly with confined electromagnetic fields in plasmonic arrays or optical microcavities owing to their bright transition dipole moments. This interaction gives rise to molecular polaritons, hybrid light-matter quasiparticles. Molecular polaritonics opens doors for new room-temperature opportunities for the nontrivial control of physico-chemical properties of molecular assemblies [1]. In this talk, I’ll showcase some of these opportunities that we have been theoretically (and, together with our experimental collaborators) exploring in the past few years. I will briefly discuss the relevant time and energy scales associated with molecular polaritons [1,2] and strategies to exploit them to control photoexcited processes including singlet fission [3], triplet harvesting [4], remote and topologically-protected energy transfer [5-7], and anomalous nonlinear optical effects [8,9,10]. Finally, I will conclude by explaining how vibrational polaritons can steer ground-state chemical reactions even in the absence of optical pumping [11], or be used to realize exotic processes such as remote control of chemical reactions [12]. Host: Suri Vaikuntanathan via email at svaikun@uchicago.edu or at 2-7256. Persons with a disability who may need assistance please contact Brenda Thomas by email at bthomas@uchicago.edu or at 2-7156.
##### The Tuesday JFI Seminar
January 28, 2020
GCIS W301 | Tuesday, 3:45 pm
## Connor Bischak, University of Washinton
#### From Solar Cells to Bioelectronics: The Interplay Between Electron and Ion Transport in Soft Semiconducting Materials
##### Chemistry
January 28, 2020
Kent 101 | Tuesday, 1:45 pm
## Stefano Sacanna, New York University
#### Engineering Colloidal Matter
##### Molecular Engineering
January 28, 2020
ERC 201 | Tuesday, 1:00 pm
## Brandi Cossairt, University of Washington
#### Interfacial Chemistry of Colloidal Nanocrystals to Direct Energy Conversion
We are interested in developing colloidal nanocrystals for wide-ranging applications in energy conversion. Our approach leverages the extraordinary properties of nanoscale systems by applying the design principles of molecular inorganic chemistry. This talk will focus on two key research themes. First, we will explore interfacial chemistry concepts to control the inner-sphere reactivity of colloidal electrocatalysts for multi-proton, multi-electron transformations. Ligand etching, ligand exchange, and covalent functionalization will be presented as complementary methods to alter electrocatalytic interfaces by tuning the activity, selectivity, and bulk interfacial properties. Second, we will explore how interfacial chemistry can be used to control the photophysics, reactivity, and assembly of colloidal semiconductor nanocrystals for emissive applications. Ultimately, we are viewing nanocrystal interfaces as platforms for coordination chemistry that will direct function.
##### Chemistry
January 27, 2020
Kent 120 | Monday, 3:45 pm
## Gregory Tarnopolsky, Harvard University
#### Origin of flat bands in Twisted Bilayer Graphene
Origin of flat bands in Twisted Bilayer Graphene, Gregory Tarnopolsky, Harvard University
Several years ago, in a continuum model of the Twisted Bilayer Graphene, a dramatic flattening of electronic low energy bands was observed numerically at a magic angle of 1.1 degrees. This theoretical discovery is believed to provide a foundation for the various interacting phenomena which were recently observed experimentally near this magic angle, including unconventional superconductivity and correlated insulators.
In this talk I will present a variant of the continuum model where the bands are exactly flat at a series of magic angles, the biggest of which is 1.1 degrees. I will exhibit an analytic derivation of this and show that the wave functions of the exactly flat band are reminiscent of the Lowest Landau Level ones. I will also discuss application of this for a construction of the Laughlin wave function in Twisted Bilayer Graphene.
January 27, 2020
MCP 201 | Monday, 10:30 am
## Steven Banik, Stanford University
#### Hijacking the Lysosome for Targeted Protein Degradation
Multifunctional molecules have redefined how both small molecules, such as catalysts, and large biomolecules, such as cellular enzymes and receptors, can be exploited for gain-of-function processes. In the former, examples of iodoarene and hydrogen bond donor catalysts highlight how multiple functionalities can act cooperatively for asymmetric fluorination reactions and the generation of reactive cationic intermediates from stable precursors. In the latter, targeted protein degradation has emerged as a powerful strategy to address the canonically difficult-to-drug proteome enabled by multifunctional molecules. However, current technologies are limited to targets with cytosolically-accessible and ligandable domains. As the primary molecular interactors with other cells, secreted and plasma membrane proteins play direct roles in oncogenesis, immune modulation, and aging-related diseases. I will discuss how the development of conjugates capable of binding both a cell surface lysosome targeting receptor and the extracellular domain of a target protein enables degradation of secreted and transmembrane proteins from the cell surface. These lysosome targeting chimeras (LYTACs) consist of a target-binding moiety (e.g. small molecules, antibodies) fused to agonist ligands for the cation-independent mannose-6-phosphate receptor (CI-M6PR), and degrade disease-relevant proteins such as apolipoprotein E4, EGFR, and PD-L1. Mechanistic analysis of LYTAC selectivity using functional genomics revealed new cellular machinery responsible for CI-M6PR recycling, and analysis of selectivity using quantitative proteomics enabled target interactome analysis. Further in vivo work suggests unique opportunities for targeted protein degradation approaches using LYTACs. The strategy outlined here provides a blueprint for expansion of a variety of tailored multifunctional molecules to allow for selective extracellular and transmembrane protein trafficking to lysosomes.
##### Chemistry
January 24, 2020
Kent 102 | Friday, 1:45 pm
## a fluidic race to the bottom thwarted by diffusion
#### Bets, anyone?
12:00 pre-race chitchat
12:15 they're off!
##### MRSEC Baglunch
January 24, 2020
GCIS E123 | Friday, 12:00 pm
## Elisabeth Bik, Harbers Bik LLC
#### Research Misconduct - The Dark Side of Science
Science builds upon science. Even after peer-review and publication, science papers could still contain problematic data, either generated by honest errors or by intentional misconduct. If not addressed post-publication, such papers containing incorrect or even falsified data could lead to wasted time and money spent by other researchers trying to reproduce those results. Elisabeth Bik is a science integrity forensics detective who left her paid job in industry to search for misconduct in scientific papers, specializing in duplicated and manipulated images. She has done a systematic scan of 20,000 biomedical papers in 40 journals and found that about 4% of these contained inappropriately duplicated images. In her talk she will present her work and discuss several types of science misconduct.
##### Physics Colloquium
January 23, 2020
KPTC 106 | Thursday, 3:30 pm
## Jolene Reid, University of Utah
#### Data Science Tools for Selectivity Prediction in Chiral Phosphoric Acid Catalysis
##### Chemistry
January 23, 2020
Kent 101 | Thursday, 1:45 pm
## Rebecca Schulman, The John Hopkins University
#### Programming the dynamics of biomolecular material devices using coupled biomolecular reaction circuitry
Modern machinery and biological cells consist of structural components, sensors and components that compute and orchestrate a material’s behavior. Integrating sensing, functionality and molecular computation into soft and biomolecular materials could make it possible to construct active and functional devices with applications in biotechnology and biological research, the design of nanoscale devices for computing and directing efficient chemical synthesis, processing and cleanup. I will describe an approach for designing and scaling the complexity and functionality of these materials and how it is used to build self-regulating biomolecular devices that self-assemble and reconfigure and for self-healing material features. I will also describe hydrogels whose shape change is directed by DNA signals that can be used to sense proteins, small molecules and mechanical signals and in response induce specific motion programs and ongoing work to use these devices for diagnostics and to construct autonomous soft robots and new materials for tissue engineering.
##### Molecular Engineering
January 23, 2020
ERC 161 | Thursday, 11:00 am
## Martin Bazant, MIT
#### Shock Electrodialysis for Ion-Selective Water Purification
Electrochemical interfaces often undergo instabilities in shape or composition, which are notoriously difficult to control in engineering applications. The first part of this talk will describe three types of moving interfaces – viscous fingers, deionization shocks, and metal dendrites – whose stability can be controlled by electrokinetic phenomena in charged porous media, with applications to electrically enhanced oil recovery, water purification by shock electrodialysis, and energy storage in metal batteries. The second part of the talk will describe how driven electrochemical reactions can alter the thermodynamic stability of solid or liquid interfaces, with applications to Li-ion batteries, electrodeposition, and biological patterns. Finally, it will be shown that the physics of pattern formation (in these and other examples) can be learned directly from image data, by solving PDE-constrained inverse problems.
##### Molecular Engineering
January 22, 2020
ERC 161 | Wednesday, 2:00 pm
## Rebecca Schulman, Johns Hopkins University
#### Programming the dynamic behavior of biomolecular materials and nanostructures using DNA circuits and reaction networks
Biological materials operate far from equilibrium and their dynamic behavior adapts to the surrounding environment as a result of coupling to chemical, mechanical and transport processes and networks of interacting signals that interpret environmental signals and control downstream kinetics. I will describe two model systems we have developed to explore the design principles for these types of responsive materials. Engineered semiflexible filaments, DNA nanotubes, can be used understand how reaction kinetics, diffusion, and chemical reaction networks can regulate growth. Nanotubes can be assembled into structures such as bridges between molecular endpoints or hierarchical networks. DNA polymerization-induced hydrogel shape change can be directed by chemical circuits that interpret upstream signals and produce outputs that initiate a shape change response. These circuits, by amplifying chemical signals, can induce high-energy changes in material shape in response to small amounts of chemical inputs. In these hydrogels the dynamics of shape change are governed by the interplay of DNA polymerization, signal transduction, transport of oligonucleotides and water, and polymer network remodeling, many of which operate on similar time scales. I will conclude by discussing how coupling hydrogel shape change with force sensors could be used for mechanical feedback.
##### Computations in Science
January 22, 2020
KPTC 206 | Wednesday, 12:15 pm
## Paul Zimmerman, College of Literature, Science and the Arts, University of Michigan
#### Chemical Thinking in Electronic Wave Functions: The Centrality of the Bond
Chemical physics of electrons can be imagined to begin with a well-known, central type of wave function: the atomic orbital. This core idea leads to a wide array of acronymized computational theories to address interactions amongst many electrons and many atoms, especially when molecules are involved. In turn, these theories are anchored by full configuration interaction, the benchmark method that provides exact results (given a specific AO basis). Full configuration interaction is famously intractable, however, due to its massive computational cost (exponential scaling). Details hidden in this narrative, however, may guide researchers to new paths in overcoming these costs: the chemical bond contains substantial structure that can be used to organize the many-electron waves. This talk will introduce the exact electronic wave function problem, explain why it is so important to chemistry, and demonstrate a possible way to solving it in polynomial time. A new acronym will appear (iFCI) with potential for near-exact solutions to electronic energies and wave functions. Host: David Mazziotti via email at damazz@uchicago.edu or 4-1762. Persons with a disability who may need assistance please contact Brenda Thomas by email at bthomas@uchicago.edu or at 2-7156.
##### The Tuesday JFI Seminar
January 21, 2020
GCIS W301 | Tuesday, 3:45 pm
## Tao Xie, Zhejiang University
#### Dynamic Covalent Polymer Networks
##### Molecular Engineering
January 21, 2020
ERC 201 | Tuesday, 3:00 pm
## José Faraldo-Gómez, PhD, NHLBI, NIH
#### Exploring how membrane proteins influence membrane morphology and vice versa
##### Biophysical Dynamics
January 21, 2020
GCIS W301 | Tuesday, 12:00 pm
## Diana Iovan, University of California - Berkeley
#### Transition Metals at the Interface of Chemistry and Biology: Catalysis and Cell Signaling
Transition metals play central roles in numerous biological processes, participating in catalysis at active sites of metalloenzymes as well as engaging in cellular signaling events. Of note, the enzymatic C–H hydroxylation reactivity of cytochrome P450 has inspired the development of strategies for the selective and efficient conversion of hydrocarbon feedstocks into value-added products. To this end, our investigations of high-spin iron dipyrrinato complexes revealed the importance of a unique high-spin ferric iminyl electronic configuration for C–H amination processes. Studies also highlighted the access to a di-iron bridging imido that can catalytically transfer the N-group into allylic and benzylic C–H bonds. Understanding the electronic structure considerations in our systems permitted us to tune the iron dipyrrin complexes to accomplish a diastereoselective C–H amination protocol. Beyond transition metal catalysis, motivated by the implications of copper ions in diseases, we sought to elucidate the emerging role of copper in interacting with proteins and modulating enzymatic activity. To this end, we explored activitybased protein profiling approaches to identify Cu-regulated metalloproteins and proposed methods to leverage the Cu-dependency of such targets for therapeutics.
##### Chemistry
January 17, 2020
Kent 102 | Friday, 1:45 pm
#### actin filaments have one floppy end
Meet, eat 12:00
discuss 12:15
##### MRSEC Baglunch
January 17, 2020
GCIS E123 | Friday, 12:00 pm
## Andreas Wallraff, ETH Zurich
#### Realizing Fault-Tolerant Superconducting Quantum Processors
Superconducting circuits are a prime contender both for addressing noisy intermediate-scale quantum (NISQ) problems and for realizing universal quantum computation in fault-tolerant processors. Superconducting circuits also play an important role in state of the art quantum optics experiments at microwave frequencies and provide interfaces in hybrid systems when combined with semiconductor quantum dots, color centers or mechanical oscillators. In this talk, I will discuss our experimental efforts towards realizing quantum error correction in superconducting circuits, which is an essential ingredient for reaching the full potential of fault-tolerant universal quantum computation. We pursue an approach based on the surface code in which we redundantly encode a logical qubit into a set of physical qubits. Using seven superconducting qubits, we have experimentally implemented the smallest viable instance of such a surface code, capable of repeatedly detecting any single error. We perform our experiments in a multiplexed device architecture [1], which enables fast, high fidelity, single-shot qubit readout [2], unconditional reset [3], and high fidelity single and two- qubit gates. Using ancilla-based stabilizer measurements, we initialize the cardinal states of the encoded logical qubit with high fidelity. We then repeatedly check for errors using the stabilizer readout and observe that the logical quantum state is preserved with a lifetime and coherence time longer than those of any of the constituent qubits, when no errors are detected [4]. Thus, we demonstrate an enhancement of the conditioned logical qubit coherence times beyond the coherences of its best constituent physical qubits. We are extending our current device architecture to a 17 qubit surface code, capable of not only detecting errors but also correcting errors using real-time feedback as demonstrated in our recent entanglement stabilization experiment [5].
References
[1] J. Heinsoo et al., Phys. Rev. Applied 10, 034040 (2018)
[2] T. Walter et al., Phys. Rev. Applied 7, 054020 (2017)
[3] P. Magnard et al., Phys. Rev. Lett. 121, 060502 (2018)
[4] C. Kraglund Andersen et al., arXiv:1912.09410 (2019)
[5] C. Kraglund Andersen et al., npj Quantum Information 5, 69 (2019)
##### Physics Colloquium
January 16, 2020
KPTC 106 | Thursday, 3:30 pm
## Joshua Buss, University of Wisconsin
#### Managing Redox Equivalents in Small Molecule Activation, Group Transfer, and Catalysis Madison
Small molecules are central to biological energy cycles and represent promising building blocks for commodity chemicals and solar fuels. The valorization of these feedstocks through selective transformations, however, is often challenging to control and mechanistically complex. The reduction of CO2 and CO to C≥2 products, is a topical example and is central to closing an anthropogenic carbon cycle. A series of Mo complexes, bearing a conserved terphenyl diphosphine ligand scaffold, shed light on important mechanistic aspects of both CO reductive catenation and CO2 reduction. Low temperature synthesis maps out the elementary steps by which C1 oxygenates are reduced and coupled at a single metal site; spectroscopy, kinetics, and isotopic labeling provide key insights into reaction design elements to control mechanistic branching points. Contrasting this reductive chemistry, oxidation of MoIV≡E complexes (E = N, P, C) can provide a route to productive E–E coupling. This process, germane to NH3 and H2O oxidation, is dictated by the degree of spindelocalization and radical character at the terminally bound atom. The same fundamental principles of controlling single electron transfers can be applied to catalyst speciation. Mechanistic probes highlight the importance of kinetically tuned reductants in maintaining catalyst activity in Cucatalyzed site-selective radical-relay C–H functionalization. These examples showcase that careful management of redox equivalents in both stoichiometric and catalytic reactions controls the selective (de)construction of chemical bonds, leveraging fundamental mechanistic understanding to achieve challenging transformations.
##### Chemistry
January 15, 2020
Kent 102 | Wednesday, 1:45 pm
## Wim van Rees, MIT
#### Theory, simulation, and design of thin elastic shape-shifting sheets
Recent progress in additive manufacturing and materials engineering has led to a surge of interest in shape-changing plate and shell-like structures. Such structures are typically manufactured in a planar configuration and, when exposed to an ambient stimulus such as heat or humidity, morph into their desired three-dimensional geometry. Viewed through the lens of differential geometry and elasticity, the application of the physical stimulus can be interpreted as a local change in the metric tensor field of the sheet. In this talk I will present my contributions to the theory and simulation of the sheet's elastic response to such a metric change, considering both the forward and the inverse problem. I will show how these developments have led to the design and experimental realization of a multi-material 4D printed lattice that can undergo complex, predictable 3D shape changes when subjected to a temperature difference.
##### Computations in Science
January 15, 2020
KPTC 206 | Wednesday, 12:15 pm
## Christopher Jarzynski, University of Maryland, College Park
The quantum adiabatic theorem governs the evolution of a wavefunction under a slowly time- varying Hamiltonian. I will consider the opposite limit of a Hamiltonian that is varied impulsively: an infinitely strong perturbation U(x,t) is applied over an infinitesimal time interval. When the strength and duration of the perturbation scale appropriately, the impulse causes the wavefunction y(x,t) to undergo a sudden displacement and/or deformation. Remarkably, this evolution is described by a purely classical construction. I will use these results to showhow tailored impulses can be used to control the behavior of a quantum wavefunction, in one or more degrees of freedom. Host: Aashish Clerk, 4-4568 or via email at aaclerk@uchicago or contact Alicia Bearden-Mannie,4-2351 or via email at amannie@uchicago.edu.
##### Molecular Engineering
January 15, 2020
ERC 201B | Wednesday, 11:00 am
## Cindy Regal, Department of Physics, University of Colorado-Boulder
#### Explorations in Cold Collisions and Magnetometry with Atoms in Optical Tweezers
Optical tweezers have become a powerful platform for individual control of single neutral atoms for quantum simulation and computing. But how does one get a single-atom source in the first place, and are there optimal ways to approach the collisional physics required to isolate a single atom? I present work in which we use a cooling technique known as grey molasses to address the complex interplay of cooling and collisional blockade physics in microscopic traps. I will also present work in which we used our optical tweezer apparatus to identify a method to extract absolute magnetic field directions using reconstruction of microwave polarization. We are now transitioning this idea to atomic vapor cells to create a sensitive and absolute vector magnetometer.Host: Aziza Suleymanzade, via email at azizas@uchicago.edu or by phone at 2-8928. Persons with a disability who may need assistance please contact Brenda Thomas by email at bthomas@uchicago.edu or at 2-7156.
##### The Tuesday JFI Seminar Cohosted by JFI Women in Science
January 14, 2020
GCIS W301 | Tuesday, 3:45 pm
## Philip Shushkov, California Institute of Technology
#### Wishing upon a star: New methods for the description of the collisional reduction of CO2 and other open quantum systems
##### Chemistry
January 14, 2020
Kent 101 | Tuesday, 1:45 pm
## Y. Shirley Meng, University of California San Diego
#### Advanced Characterization for Long Life High Energy Battery Materials
High energy long life rechargeable battery is considered as key enabling technology for deep de-carbonization. Energy storage in the electrochemical form is attractive because of its high efficiency and fast response time. Besides the technological importance, electrochemical devices also provide a unique platform for fundamental and applied materials research since ion movement is often accompanied by inherent complex phenomena related to phase changes, electronic structure changes and defect generation. In this seminar, I will discuss a few new perspectives for energy storage materials including new fast ion conductors, new intercalation compounds and their interfacial engineering. With recent advances in characterization tools and computational methods, we are able to explore ionic mobility, charge transfer and phase transformations in electrode materials in-operando, and map out the structure-properties relations in functional materials for next generation energy storage and conversion. Moreover, I will discuss a few future priority research directions for electrochemical energy storage.
##### Molecular Engineering
January 14, 2020
ERC 161 | Tuesday, 11:00 am
## Chris Jarzynski, University of Maryland
#### Scaling down the laws of thermodynamics
Thermodynamics provides a robust conceptual framework and set of laws that govern the exchange of energy and matter. Although these laws were originally articulated for macroscopic objects, nanoscale systems also exhibit “thermodynamic¬-like” behavior – for instance, biomolecular motors convert chemical fuel into mechanical work, and single molecules exhibit hysteresis when manipulated using optical tweezers. To what extent can the laws of thermodynamics be scaled down to apply to individual microscopic systems, and what new features emerge at the nanoscale? I will describe some of the challenges and recent progress – both theoretical and experimental – associated with addressing these questions. Along the way, my talk will touch on non-equilibrium fluctuations, “violations” of the second law, the thermodynamic arrow of time, nanoscale feedback control, strong system-environment coupling, and quantum thermodynamics.
##### Chemistry
January 13, 2020
Kent 120 | Monday, 3:45 pm
## Po-Shen Hsin, Caltech
#### Lorentz symmetry fractionalization and duality in (2+1)d Po-Shen Hsin, Caltech
I will introduce a new discretetransformation in quantum field theories with Z2 1-form global symmetry thatacts on line operators (point-like excitations). Then I will discussapplications to Chern-Simons matter dualities in (2+1)d.
January 13, 2020
MCP 201 | Monday, 1:30 pm
## Matthew Good, PhD, Cell & Devel Biol and Bioengineering, Upenn
#### Sequence Determinants & Fidelity of RGG Domain Condensation to Form Membraneless Organelles
Coacervation of intrinsically disordered proteins (IDPs) commonly underlies formation of membraneless organelles, which compartmentalize molecules intracellularly in the absence of a lipid membrane. However, to date, protein coacervation cannot be predicted from primary sequence. Using a combination of predictive coarse-grained modeling, in vitro characterization and in vivo expression we characterized the chemical determinants of IDP phase separation for the disordered RGG domain from the scaffold protein LAF-1. We identified regions that have high contact probability and deletion of which significantly disrupt protein condensation in vitro and in vivo. We designed sequence variants to investigate the role of charge patterning on phase behavior and found that shuffled sequences with greater charge segregation dramatically enhances propensity to phase separate. Mutation of tyrosine to phenylalanine, or arginine to lysine, dramatically perturbed RGG phase separation, and all-atom models highlight the special role of arginine in sp2-pi interactions. Building off of this platform we are identifying chemical principles that regulate the fidelity of selective protein coacervation and prevent inappropriate mixing of disordered proteins. Finally, we demonstrate the utility of RGG-based constructs for cellular engineering. By layering enzymatic and optical regulatory handles to regulate protein solubility and valency, we can control protein condensation to form synthetic membraneless organelles in cells. Together, these studies identify key biophysical principles of RGG domain condensation, including conserved motifs, critical residues and charge patterning, while also advancing a predictive framework to identify and design sequences that phase separate.
Margaret Gardel (host).
##### Biophysical Dynamics
January 11, 2020
GCIS W301 | Saturday, 12:00 pm
## how DNA can alter actin's nematic defects
food-mediated self assembly: 12:00
idea mediated discussion: 12:15
##### MRSEC Baglunch
January 10, 2020
GCIS E123 | Friday, 12:00 pm
## Angela Olinto, University of Chicago
#### Space Observatories of the Highest Energy Particles: POEMMA & EUSO-SPB
What are the mysterious sources of the most energetic particles ever observed? What are the sources of energetic cosmic neutrinos? How do particles interact at extreme energies?
Building on the progress achieved by the ground-based Auger Observatory in studying cosmic particles that reach 100 EeV, an international collaboration is working on space and sub-orbital missions to answer these questions. The Extreme Universe Space Observatory (EUSO) on a super pressure balloon (SPB) is designed to detect ultra-high energy cosmic rays (UHECRs) from above. EUSO-SPB1 flew in 2017 with a fluorescence telescope. EUSO-SPB2 is being built to observe both fluorescence and Cherenkov from UHECRs and neutrinos. These sub-orbital missions lead to POEMMA, the Probe Of Extreme Multi-Messenger Astrophysics, a space mission designed to discover the sources of UHECRs and to observe neutrinos above 20 PeV from energetic transient events. POEMMA will open new Multi-Messenger windows onto the most energetic events in the Universe, enabling the study of new astrophysics and particle physics at these otherwise inaccessible energies.
##### Physics Colloquium
January 9, 2020
KPTC 106 | Thursday, 3:30 pm
## Ana Maria Rey, JILA and Department of Physics University of Colorado
#### Observation of Dynamical Phase Transitions in Cold Atomic Gases
Non-equilibrium quantum many-body systems can display fascinating phenomena relevant for various fields in science ranging from physics, to chemistry, and ultimately, for the broadest possible scope, life itself. The challenge with these systems, however, is that the powerful formalism of statistical physics, which have allowed a classification of quantum phases of matter at equilibrium does not apply.
Therefore, using controllable cold atomic systems to shed light on the organizing principles and universal behaviors of dynamical quantum matter is highly appealing. One emerging paradigm is the dynamical phase transition (DPT) characterized by the existence of a long-time-average order parameter that distinguishes two non- equilibrium phases. I will report the observation of a DPT in two different but complementary systems: a trapped quantum degenerate Fermi gas [1] and long lived arrays of atoms in an optical cavity [2]. I will show how these systems can be used to simulate iconic models of quantum magnetism with tunable parameters and to probe the dependence of their associated dynamical phases on a broad parameter space. Besides advancing quantum simulation our studies pave the ground for the generation
of metrologically useful entangled states which can enable real metrological gains via quantum enhancement.
##### Molecular Engineering
January 9, 2020
ERC 161 | Thursday, 11:00 am
## Eric Dufresne, ETH Zürich
#### The Mechanics of Soft Interfaces
Surface tension has dramatic and well-understood impacts on simple liquids. It forces small droplets to ball up, and drives liquids into narrow channels. At small scales, these interfacial forces influence a wider range of materials and pose a number of open questions.
I will describe microscopic experiments probing the interfaces of soft materials, including polymer networks and lipid bilayers. Here, the interplay of surface tension and elasticity qualitatively changes the phenomena of wetting and adhesion. First, I will describe how we exploit these effects to investigate the surface tension of soft solids. These experiments reveal fundamental differences with familiar liquid surface tension. While the surface tension of simple liquids is a constant scalar quantity, the surface tension of solids is an anisotropic and strain-dependent tensor. It is characterized not only by an interfacial energy, but also by surface shear and dilational moduli. The physical origins of these quantities are essentially unexplored. Second, I will describe new experiments investigating the adhesion of colloidal particles to lipid bilayers. Here, the competition of surface tension, bending rigidity, and interfacial energy can drive the assembly of large scale structures.
##### Computations in Science
January 8, 2020
KPTC 206 | Wednesday, 12:15 pm
## Eric Dufresne, ETH Zürich
#### Growing Droplets in Cells and Gels
To function effectively, living cells compartmentalize myriad chemical reactions. In the classic view, distinct functional volumes are separated by thin oily-barriers called membranes. Recently, the spontaneous sorting of cellular components into membraneless liquid-like domains has been appreciated as an alternate route to compartmentalization.
I will review the essential physical concepts thought to underly these biological phenomena, and outline some fundamental questions in soft matter physics that they inspire. Then, I will focus on the coupling of phase separation to elastic stresses in polymer networks. Using a series of experiments spanning living cells and synthetic materials, I will demonstrate that bulk mechanical stresses dramatically impact every stage in the life of a droplet, from nucleation and growth to ripening and dissolution.
These physical phenomena suggest new mechanisms that cells could exploit to regulate phase separation, and open new routes to the assembly of functional materials
##### Biophysical Dynamics
January 7, 2020
GCIS W301 | Tuesday, 12:00 pm
## Luca Delacretaz, Uchicago
#### Hydrodynamic Tails in CFT and the Large Delta Expansion
The late time physics of interacting Quantum Field Theories at finite temperature is controlled by hydrodynamics. For CFTs this implies that heavy operators -- which are generically expected to create thermal states -- can be studied semi-classically. I will show that hydrodynamic loops universally fix the OPE coefficients C_{HH'L}, on average, of all neutral light operators with two non-identical heavy ones, as a function of the scaling dimension and spin of the operators. These methods can be straightforwardly extended to CFTs with global symmetries, and generalize recent EFT results on large charge operators away from the case of minimal dimension at fixed charge.
January 6, 2020
MCP 201 | Monday, 1:30 pm
## W. Benjamin Rogers, Brandeis University
#### Programming dynamic pathways to self-assembly using DNA nanotechnology
DNA is not just the stuff of our genetic code; it is also a means to build new materials. For instance, grafting DNA onto small particles can, in principle, 'program' the particles with information that tells them exactly how to put themselves together--they 'self-assemble.' Recent advances in our understanding of how this information is compiled into specific interparticle forces have enabled the assembly of crystalline phases. However, programmable assembly of other user-prescribed structures, such as aperiodic solids, liquids, or other mesophases remains elusive. Furthermore, the dynamic pathways by which DNA-based materials self-assemble are largely unknown. In this talk, I will present experiments showing that: (1) combining DNA-grafted particles with free DNA oligomers dispersed in solution can create suspensions with new types of assembly pathways; and (2) we can quantify the dynamic pathways to self-assembly, such as nucleation and growth, using a combination of microfluidics, video microscopy, and image analysis. Whenever possible, I will describe attempts to understand and model our observations using simple physical arguments.
##### Computations in Science
December 11, 2019
KPTC 206 | Wednesday, 12:15 pm
## John Weeks, Institute for Physical Science and Technology & Department of Chemistry and Biochemistry - University of Maryland
#### Solvation, Structure, and Simulations of Systems with Strong Coulomb Interactions: The Long and Short of It
ong ranged Coulomb interactions play a major role in determining the thermodynamics, structure, and dynamics of condensed phases, but present significant challenges to theory and computer simulations. Standard treatments use Ewald sums to account for distant periodic images of charges in the simulation cell. This can add significant overhead to computer simulations and hampers the development of simple local pictures and analytic theory.
Here we describe new and ongoing work using Local Molecular Field (LMF) theory to provide a unified description of nonuniform charged and polar fluids and biopolymers. LMF theory introduces a general mapping that relates the structure and thermodynamics of a nonuniform system with long-ranged Coulomb or van der Waals interactions to those of a simpler "mimic system" with effective short ranged interactions that accurately incorporate the averaged effects of the long-ranged interactions. We show that LMF theory can be viewed as a natural generalization of ideas leading to the classical van der Waals equation for uniform simple liquids like Argon.
We use LMF theory to describe the very different behavior of the cation-anion pair correlation function in dilute aqueous solutions of NaCl and CaCl2 and the hydration and association of apolar Argon and Fullerene solutes in water. This approach leads to a Short Solvent (SS) model, with truncated solvent Coulomb interactions and screened long ranged Coulomb interactions only between charged solutes. The SS model accurately describes the interplay between local hydrogen bond configurations, solute core interactions, and the long ranged dielectric screening of distant solute charges, effects that are difficult to capture in standard implicit solvent models. Host: Gregory Voth via email at gavoth@uchicago.edu or at 2-9092. Persons with a disability who may need assistance please contact Brenda Thomas by email at bthomas@uchicago.edu or at 2-7156.
##### The Tuesday JFI Seminar Presents The 2nd Annual Rice-Berry Lecture
December 10, 2019
GCIS W301 | Tuesday, 3:45 pm
## Francesco Paesani, University of California San Diego
#### Modeling Hydration, One Molecule at a Time: Realistic Computer Simulations Through Data-Driven Many-Body Models
##### Chemistry
December 9, 2019
Kent 120 | Monday, 3:45 pm
## Chaoming Jian, Stanford
#### Measurement-indeed criticality in random quantum circuits
In this talk, I will present the study of the critical behavior of the entanglement transition induced by projective measurements in (Haar) random unitary quantum circuits. I will present a replica approach that maps the calculation of the entanglement entropies in such circuits onto a two-dimensional statistical mechanics model. In this language, the area- to volume-law entanglement transition can be interpreted as an ordering transition in the statistical mechanics model. I will discuss the general scaling properties of the entanglement entropies and mutual information near the transition using conformal invariance. I will focus on a more detailed analysis in the limit of infinite on-site Hilbert space dimension in which the statistical mechanics model maps onto percolation. In particular, this analysis yields the exact value of the universal coefficient of the logarithm of subsystem size in the Rényi (including Von Neumann) entropies. I also will discuss how to access the generic transition at finite on-site Hilbert space dimension from this limit, which is in a universality class different from 2D percolation.
December 9, 2019
MCP 201 | Monday, 1:30 pm
## Physics with A Bang! Holiday Lecture and JFI Open House
Students, families, teachers and especially the curious are invited to attend our annual Holiday Lecture and Open House. See fast, loud, surprising and beautiful physics demos performed by Profs. Heinrich Jaeger and Sidney Nagel. Talk to scientists about their latest discoveries. Participate in hands-on activities related to their research.
Saturday, December 7th, 2019
Kersten Physics Teaching Center
5720 S. Ellis Ave., Chicago, IL
Lecture repeated at 11am and 2pm
Open House and Demo Alley from 12pm-4pm
Lab Tours in the afternoon
Doors for the Lectures open 30 minutes before each show. Admission to this event is free. Please note: there will be no online registrations, and will be a first to arrive, first ticketed event. We do not guarantee availibility of seating, but shows will also be streamed live to alternate venues.
This event is sponsored by the James Franck Institute, the Department of Physics, the Office of the Executive Vice President for Research, Innovation and National Laboratories, and the Materials Research Science & Engineering Center. The organizer of the Open House is Prof. Sarah King.
For those needing special assistance, please send an email to ecs@uchicago.edu.
##### Special JFI Seminar
December 7, 2019
KPTC 106 | Saturday, 11:00 am
## Art McDonald, Queen’s University, Canada
#### Deep Underground Measurements in Fundamental Physics and Astrophysics
By going deep underground and creating ultra-clean detectors it is possible to address some very fundamental questions about our Universe: How does the Sun burn? What are the detailed properties of neutrinos and of the dark matter particles that make up 26% of our Universe and influence how it evolves? With the Sudbury Neutrino Observatory (SNO) we went 2 km underground to observe new properties of neutrinos that are beyond the Standard Model of Elementary Particles and also confirmed that the models of how the Sun burns are very accurate. With SNO+, we are now seeking new properties of neutrinos through measurement of the neutrino-less double beta decay of 130 Te. The Global Argon Dark Matter Collaboration is pursuing measurements at the SNOLAB (Canada) and Gran Sasso (Italy) underground laboratories with the DEAP- 3600, DarkSide-20k and Argo experiments, using liquid argon as a target for interactions by Weakly Interacting Massive Particles (WIMPs). By these measurements, we hope to push the sensitivity for detecting such potential Dark Matter particles by several orders of magnitude and perhaps observe a whole new type of matter.
##### Physics Colloquium
December 5, 2019
KPTC 115 | Thursday, 3:30 pm
## Irmgard Bischofberger, MIT
#### On Flow and Failure: Pattern Formation from Instabilities in Complex Fluids
The invasion of one fluid into another of higher viscosity is unstable in a quasi-two dimensional geometry. This viscous-fingering instability typically produces complex patterns that are characterized by repeated branching of the evolving structure. When one of the fluids is replaced by a complex fluid, the system still displays a wide range of morphologies, but their underlying mechanisms can be fundamentally altered. We explore the formation of these new patterns by considering colloidal suspensions of different concentration. (i) We sandwich a colloidal gel between two parallel plates and induce an instability at the air/gel interface by lifting the upper plate at a constant velocity. Remarkably, the viscous-fingering instability resulting from the invasion of air fingers into the gel is suppressed below a critical lift velocity and above a critical initial gap thickness. We show that the onset of the instability is determined by a critical rate of viscous energy dissipation in the gel that is proportional to the gel’s yield stress, providing a quantitative criterion for instabilities in colloidal gels. (ii) Expanding our studies to dense suspensions that exhibit discontinuous shear-thickening behavior as a response to an applied stress allows us to probe transitions from flow instabilities to fractures. Displacing a cornstarch suspension by a pressure-controlled injection of air, we observe smooth fingering in the fluid regime and different modes of fractures, ranging from slow branched cracks to single fast fractures. We discuss strategies to predict and control these different failure modes in dense suspensions.
##### Computations in Science
December 4, 2019
KPTC 206 | Wednesday, 12:15 pm
## Philip E. Dawson PhD, Department of Chemistry, Scripps
#### Chemoselective ligation - from protein engineering to DNA encoded libraries
##### Biophysical Dynamics
December 3, 2019
GCIS W301 | Tuesday, 4:00 pm
## Victor Galitski, Department of Physics, University of Maryland
#### Quantum Lyapunov Exponents
Classical chaotic systems exhibit exponential divergence of initially infinitesimally close trajectories, which is characterized by the Lyapunov exponent. This sensitivity to initial conditions is popularly known as the "butterfly effect." Of great recent interest has been to understand how/if the butterfly effect and Lyapunov exponents generalize to quantum mechanics, where the notion of a trajectory does not exist. In this talk, I will introduce the measure of quantum chaoticity – a so-called out-of-time-ordered four-point correlator (whose semiclassical limit reproduces classical Lyapunov growth), and use it to describe quantum chaotic dynamics and its eventual disappearance in the standard models of classical and quantum chaos – Bunimovich stadium billiard and standard map or kicked rotor [1]. I will describe our recent results on the quantum Lyapunov exponent in these single-particle models as well as results in interacting many-body systems, such as disordered metals [2]. The latter many-body model exhibits an interaction-induced transition from quantum chaotic to non-chaotic dynamics, which may manifest itself in a sharp change of the distribution of energy levels from Wigner-Dyson to Poisson statistics. I will conclude by formulating a many-body analogue of the Bohigas-Giannoni-Schmit conjecture. References: [1] "Lyapunov exponent and out-of-time-ordered correlator's growth rate in a chaotic system," E. Rozenbaum, S. Ganeshan, and V. Galitski, Physical Review Letters 118, 086801 (2017)
[2] "Non-linear sigma model approach to many-body quantum chaos," Y. Liao and and V. Galitski, Physical Review B 98, 205124 (2018)
##### The 1st Tuesday JFI Colloquium
December 3, 2019
GCIS W301 | Tuesday, 3:45 pm
## Tom Muir, Princeton University
#### Painting Chromatin with Synthetic Protein Chemistry
##### Chemistry
December 2, 2019
Kent 120 | Monday, 3:45 pm
## Gregory Falkovich, Weizmann Institute of Science
#### Wonders of viscous electronics
Quantum-critical strongly correlated systems feature universal collision-dominated collective transport. Viscous electronics is an emerging field dealing with systems in which strongly interacting electrons flow like a fluid. Such flows have some remarkable properties never seen before. I shall describe recent theoretical and experimental works devoted, in particular, to a striking macroscopic DC transport behavior: viscous friction can drive electric current against an applied field, resulting in a negative resistance, recently measured experimentally in graphene. I shall also describe conductance exceeding the fundamental quantum-ballistic limit, field-theoretical anomalies, freely flowing viscous currents and other wonders of viscous electronics. Strongly interacting electron-hole plasma in high-mobility graphene affords a unique link between quantum-critical electron transport and the wealth of fluid mechanics phenomena.
December 2, 2019
MCP 201 | Monday, 1:30 pm
## Andrea Alu, CUNY Advanced Science Research Center
#### Metamaterials Based on Broken Symmetries
In this talk, I discuss our recent research activity in electromagnetics, nano-optics, acoustics and mechanics, showing how suitably tailored meta-atoms and suitable arrangements of them open exciting venues to realize new phenomena and devices for light, radio-waves and sound. I discuss venues to largely break Lorentz reciprocity and realize isolation without the need of magnetic bias, based on broken time-reversal symmetry induced by mechanical motion, spatio-temporal modulation and/or nonlinearities. I also discuss how broken symmetries in space and space-time can open the opportunity to induce topological order in metamaterials. Another class of interesting metamaterials based on broken symmetries are parity-time symmetric metamaterials, which are asymmetric in space, but symmetric upon parity and time inversion. In the talk, I will also discuss the impact of these concepts from basic science to practical technology, from classical waves to quantum phenomena. Host: Aashish Clerk at 4-4568 or via email at aaclerk@uchicago.edu. Persons needing further assistance please contact Alicia Bearden Mannie at 4-2351 or by email at amannie@uchicago.edu
##### Molecular Engineering
December 2, 2019
ERC 161 | Monday, 10:00 am
## Michael Murrell - Department of Physics & Biomedical Engineering
#### Broken Time Reversal Symmetry and the Efficiency of Biological Machines
Biological systems are driven far from equilibrium through the consumption and dissipation of energy. However, it is unclear if the quality or efficiency of a biological process is enhanced the further the system is driven from equilibrium. To address this fundamental question, we develop experimental approaches to control the consumption of energy in biological systems, and theoretical approaches to measure its dissipation. Together, we gain an understanding of the regulation of energy during the assembly and performance of biological machinery across diverse time and length-scales. At the molecular scale, we develop technologies to precisely coordinate the de novo assembly of the protein-based mechanical machinery of the cell and control its consumption of chemical energy. In doing so, we seek to mimic the physical behaviors of living cells through modulating the internal, non-equilibrium “activity”. At the mesoscopic scale, we study the physical behaviors of cells and tissues by abstracting them as driven liquids, whose behaviors are described by models of capillarity and wetting adapted to reflect activity gleaned from molecular studies. At all scales, we apply frameworks from stochastic thermodynamics to estimate dissipation and the production of entropy using phase space fluxes and the breaking of time reversal symmetry. Together, these experimental and theoretical methods can enable an understanding of the relationship between dissipation and the efficiency of biological processes. In addition, we will show how these methods provide a comprehensive description for how active stresses generated at the molecular level translate to the physical behaviors of cells and tissues, and have significant impacts on phenotypic outcomes such as cancer metastasis, and wound healing. Host: Danielle Schell, 2-8928 or via email at dscheff@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### Tuesday Seminar - JFI Women in Science
November 26, 2019
GCIS W301 | Tuesday, 3:45 pm
## Jing-Yuan Chen, Stanford
#### Enhanced Thermal Hall Effect in Nearly Ferroelectric Insulators
Thermal Hall measurement has become increasingly important in condensed matter physics. In the context of recent experimental observations of an unexpectedly large thermal Hall conductivity in insulating La2CuO4 and SrTiO3, collaborators and I theoretically explored conditions under which acoustic phonons can give rise to such a large thermal Hall effect. Both the intrinsic and extrinsic contributions to the thermal Hall conductivity are large in proportion to the dielectric constant and the flexoelectric coupling. While the intrinsic contribution is still orders of magnitude smaller than the observed effect, an extrinsic contribution proportional to the phonon mean free path appears likely to account for the observations, at least in SrTiO3. We predict a larger intrinsic and/or extrinsic contribution to thermal Hall effect in certain insulating perovskites. I will discuss the implications for existing and future thermal Hall experiments, as well as new theoretical problems to explore.
November 26, 2019
MCP 201 | Tuesday, 1:30 pm
## David Grier Prize Minisymposium
#### David Grier Prize in Innovation in Biophysical Sciences Finalist Minisymposium
David Grier Prize inInnovation in Biophysical Sciences Finalist Minisymposium
Featuring
Kourtney Kroll Sosnick & Rock groups speaking on Engineering a Light Driven Molecular Motor
Wen-Hung Chou Gardel & Kovar groups speaking on Regulation of Myosin II Filament Assembly
by the Actin Cytoskeleton
Elizabeth White, Scherer & Dinner groups speaking on Correlating Insulin Granule Intracellular Dynamics & Exocytosis Using FRET Voltage Sensors
##### Biophysical Dynamics
November 26, 2019
GCIS W301 | Tuesday, 11:30 am
## Thomas E. Albrecht-Schmitt, Florida State University
#### Chemistry Beyond Plutonium: How Relativity Alters Electronic Structure in Heavy Elements
##### Closs Lecture
November 25, 2019
Kent 120 | Monday, 3:45 pm
## Ramis Movassagh, Cambridge Research Center
#### Highly entangled spin chains: Exactly solvable counter-examples to the area law
In recent years, there has been a surge of activities in proposing "exactly solvable" quantum spin chains with surprising high amount of ground state entanglement--exponentially more than critical systems that have $\log(n)$ von Neumann entropy. We discuss these models from first principles. For a spin chain of length $n$, we prove that the ground state entanglement entropy is $\sqrt(n)$ and in some cases even extensive (i.e., extensive $n$) despite the underlying Hamiltonian being: (1) Local (2) Having a unique ground state and (3) Translationally invariant in the bulk. These models have rich connections with combinatorics, random walks, Markov chains, and universality of Brownian excursions. Lastly, we develop techniques for proving the gap. As a consequence, the gap of Motzkin and Fredkin spin chains are proved to vanish as 1/n^c with c>2; this rules out the possibility of these models to be relativistic conformal field theories in the continuum limit. Time permitting we will discuss more recent developments in this direction and 'generic' aspects of local spin chains.
November 25, 2019
MCP 201 | Monday, 1:30 pm
## Brainstorming about MRSEC open house
What would be your favorite goofy or awesome thing to show our young visitors on Friday December 7th? We have many hours to entertain and inspire them with hands-on demos and lab tours. What about kids who came last year and are looking for something new? Have we got enough?
What about simulations? In prior years we had stunning hands-on computer demos of chaos, critical phenomena, simulated scattering and reaction events, piling games, We probably have even better ones now. Do you have ideas?
What about everyday life science effects like how color images on a computer screen are made, or how ice becomes less slippery when it gets colder or how to ride your bike in the rain without getting mud on your back? or how to reveal the speed of fluttering leaves by analyzing a movie of a tree.
to get on this mailing list, go to
https://lists.uchicago.edu/web/info/mrsec-baglunch
##### MRSEC Baglunch
November 22, 2019
GCIS E123 | Friday, 12:00 pm
## Vanessa Wood, Chair, MaDe, ETH Zürich
#### Understanding and Optimizing Solution- Processed Systems
Solution- and slurry-processing techniques offer possibilities for scalable and low-cost manufacturing. Today, these techniques enable technologies such as lithium ion batteries and promise to play a future role in a wide variety of electronic, photonic, and electrochemical systems. Materials and devices made from these approaches often have hierarchical structures and complex interfaces. To realize the full potential of solution-processed systems, understanding structure- performance relationships is critical. In this talk, I will present examples of how my group uses neutrons, electrons, and photons to characterize structure at different length scales and to gain insights into performance limitations of solution- processed systems, including lithium ion batteries and nanocrystal-based optoelectronics. I will then describe how we apply these findings to develop design guidelines for systematic improvement of materials and devices.
##### Molecular Engineering
November 21, 2019
BSLC 115 | Thursday, 2:00 pm
## Rebecca Willett, University of Chicago
#### Leveraging physical models in machine learning
Machine learning, at its heart, is the process of learning from examples. However, in many scientific domains, we not only have training data or examples from which to learn, but also physical models of either the data collection mechanism or the underlying physical phenomenon. In this talk, I will describe two settings in which physical models can be incorporated within a machine learning framework to yield improved predictive performance. First, we will consider using training data to help solve ill-posed linear inverse problem such as deblurring, deconvolution, inpainting, compressed sensing, and superresolution. Recent advances in machine learning and image processing have illustrated that it is often possible to learn a regularizer from training data that can outperform more traditional regularizers. We will see that whether or how a forward model is leveraged can significantly impact how many training samples are needed to achieve a target accuracy. Second, we will examine using a combination of observational data and simulated data to improve subseasonal climate forecasts. Treating both types of data as co-equal training samples can bias many learning methods and yield misleading results. I will describe an alternative framework that combines observational data with a correlation graph that can be estimated from large ensemble climate model outputs, and we will see how this approach leads to more accurate forecasts. Finally, we will discuss open problems and future directions at the intersection of machine learning and the physical sciences.
##### Computations in Science
November 20, 2019
KPTC 206 | Wednesday, 12:15 pm
## Michael Crommie, University of California-Berkeley
#### Using Topology to Engineer Bottom-Up-Synthesized Graphene Nanoribbons
The idea of classifying materials by their topological properties is useful for predicting their behavior, especially at interfaces between insulators. When topologically distinct insulators are fused together then metallic states arise at the interfaces between them. This concept, which has been so fruitful in condensed matter physics for 3D and 2D materials, has recently been extended to 1D graphene nanoribbons (GNRs), which can now be classified by topology [1]. A single 0D interface between two 1D GNRs having dissimilar topology cannot support a full metallic band like higher-dimensional topological insulators, but it can generate the most basic constituent of a metal: a single, unpaired electron localized to a protected state in the GNR bandgap. By engineering multiple topological interfaces within a GNR it is thus possible to controllably position unpaired electrons that quantum mechanically interact and produce new GNR electronic and magnetic behavior. Achieving such fine topological control, however, requires the synthesis of precise, atomically-defined nanoscale interfaces. I will discuss how we have accomplished this by using new chemistry-based bottom-up synthesis techniques that enable us to build perfect interfaces between topologically distinct GNR segments. Scanning tunneling microscopy allows us to image and spectroscopically probe the resulting topologically-protected electronic states that reside at these interfaces. This technique has enabled us to engineer the band structure of semiconducting GNRs in new ways, to create metallic GNRs, and to synthesize new GNR-based quantum dot systems that are potentially useful for quantum information applications. The work I will describe lies at the boundary of condensed matter physics and organic chemistry, and is an example of the power of blending concepts from these two fields. Host: Jiwoong Park, 4-3179 or via emailjwpark@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
November 19, 2019
GCIS W301 | Tuesday, 3:45 pm
## Nigel Goldenfeld PhD, Physics, UIUC
#### Stochastic Turing patterns in oceans, brains & biofilms
Why are the patterns of plankton in the ocean so patchy? Why do frequently described geometrical hallucinations tend to fall into one of four different classes of pattern? Why don't we see hallucinations all the time? And why do populations in ecosystems tend to have noisy cycles in abundance? This talk explains how these phenomena all arise from the discreteness of the underlying entities, be they the on-off states of neurons or the numbers of bacteria in a fluid volume of ocean, or the number of signaling molecules in a biofilm. I explain how tools from statistical mechanics can yield insights into these phenomena, and report on a range of studies that include the operation of the primate visual cortex, the behavior of signalling molecules in a forward-engineered synthetic biofilm, and the fluctuating patterns and populations of marine organisms.
##### Biophysical Dynamics
November 19, 2019
GCIS W301 | Tuesday, 12:00 pm
## Latha Venkataraman, Columbia University
#### Quantum interference based single-molecule insulators
##### Chemistry
November 18, 2019
Kent 120 | Monday, 3:45 pm
## Victor-luca Iliesiu, Princeton University
#### Two-dimensional gravity, gauge fields and the statistical mechanics of near-extremal black holes
The low-energy behavior of near-extremal black holes can be understood from the near-horizon AdS_2 region. In turn, this region is effectively described by using Jackiw-Teitelboim gravity coupled to Yang-Mills theory. We show that such a two-dimensional model of gravity coupled to gauge fields is soluble for an arbitrary choice of gauge group and gauge couplings. Specifically, we determine the partition function of the theory on two-dimensional surfaces of arbitrary genus and with an arbitrary number of boundaries. When solely focusing on the contribution from surfaces with disk topology, we show that the gravitational gauge theory is described by the Schwarzian theory coupled to a particle moving on the gauge group manifold. Such a theory is expected to arise as the low energy limit of SYK-like models with a global symmetry. When considering the contribution from all topologies, we show that the theory is described by a novel random matrix ensemble. Finally, we compute the expectation value of various line operators in the gravitational gauge theory and describe their relationship to near-extremal black hole observables.
November 18, 2019
MCP 201 | Monday, 1:30 pm
## Matthew Sigman, University of Utah
#### Integrating Data Science Tools into Reaction Development
##### AbbVie Lecture
November 15, 2019
Kent 120 | Friday, 1:45 pm
## Joseph Checkelsky, MIT
#### Synthesizing “Toy Model” Quantum Materials
Connecting theoretical models for exotic quantum states to real physical systems is a key goal in the study of quantum materials. Among such theoretical models, a “toy model” is one made deliberately simplistic in order to demonstrate new physical concepts and their underlying mechanisms. Such models have proven to be tremendously successful in offering insight into new condensed matter phenomena including those involving electronic topology and correlation. We describe here our recent progress in experimentally realizing “toy model” quantum materials which, in analogy to their theoretical counterparts, are designed to capture simple model systems by lattice and superlattice design. We detail developments in synthesizing and studying magnetic and superconducting materials that allow for new connections to long-standing predictions for unusual topological electronic phases. We close with a perspective for realizing further toy model systems in complex material structures.
Event Type
##### Physics Colloquium
November 14, 2019
KPTC 114 | Thursday, 3:30 pm
## Orit Peleg, University of Colorado
#### Collective Ecophysiology and Physics of Honeybees
Collective behavior of organisms creates environmental micro-niches that buffer them from environmental fluctuations e.g. temperature, humidity, mechanical perturbations etc., thus coupling organismal physiology, environmental physics and population ecology. This talk will focus on a combination of biological experiments, theory and computation to understand how a collective of bees can integrate physical and behavioral cues to attain a non-equilibrium steady state that allows them to resist and respond to environmental fluctuations of forces and flows. We analyze how honeybee clusters (Apis mellifera L.) change their shape and connectivity and gain stability by spread-eagling themselves in response to mechanical perturbations. Similarly, we study how bees in a colony respond to environmental thermal perturbations by deploying a fanning strategy at the entrance that they use to create a forced ventilation stream that allows the bees to collectively maintain a constant hive temperature. When combined with quantitative analysis and computations in both systems, we integrate the sensing of the environmental cues (acceleration, temperature, flow) and convert them to behavioral outputs that allow the swarms to achieve a dynamic homeostasis.
##### Computations in Science
November 13, 2019
KPTC 206 | Wednesday, 12:15 pm
## Margaret Johnson, Department of Biophysics - Johns Hopkins University
#### Control of Multi-Protein Self-Assembly by Membrane Localization
In diverse cellular pathways including clathrin-mediated endocytosis (CME) and viral bud formation, cytosolic proteins must self-assemble and localize to membranes. A wealth of biochemical, structural, and in vivoimaging data has provided deep insight into the seconds-to-minutes long dynamics of these self-assembly processes. Yet it is still remarkably difficult to predict how the stoichiometry of components, membrane bending, or coupling to enzymatic reactions impacts function, and this is where computational modeling can provide important insights. We recently developed novel reaction-diffusion algorithms and software that enable detailed computer simulations of nonequilibrium self-assembly over long time-scales. We have shown through theory and simulation how localization of protein binding partners to the membrane can dramatically enhance binding through dimensionality reduction, providing a trigger for assembly. As a result, we show how tuning the localization strength of proteins to the membrane, via either protein or lipid binding partners, can drive assembly and disassembly of clathrin-coated structures. This will help us to predict how the transition from early clathrin coated structures to productive vesicles is controlled in the cell. Lastly, our generalized computational methods can directly simulate a broad range of assembly processes at the cell-scale, providing a natural companion to quantitative cell biology. Host: Arvind Murugan, 4-3146 or via email at amurugan@uchicago.edu. Persons with a disability who may assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
November 12, 2019
GCIS W301 | Tuesday, 3:45 pm
## Chris Hill, PhD, Department of Biochemistry, University of Utah
#### Structural insights to the mechanism of Vps4 & other AAA unfoldases
Many cellular membrane fission reactions are driven by ESCRT pathways, which culminate in remodeling and disassembly of ESCRT-III polymers by the AAA ATPase Vps4. Recent advances in understanding of the budding machinery will be summarized, with special emphasis on structural studies of Vps4. These findings suggest that translocation and unfolding of substrate is achieved by a hand-over-hand mechanism in which five Vps4 subunits form a helix that is stabilized by binding ATP, while the sixth subunit of the Vps4 hexamer transitions between the ends of the five-subunit helix. The ESCRT-III substrate peptide binds in an extended (beta-strand) conformation against the five helical subunits, with its side chains binding into two arrays of binding pockets that propagate through the hexamer pore, such that each ATP hydrolysis and substrate transition results in translocation of two substrate amino acid residues. In this manner Vps4 and other AAA unfoldases, including Cdc48 and spastin, may unfold their substrate proteins by threading their polypeptide chains through a narrow pore.
##### Biophysical Dynamics
November 12, 2019
GCIS W301 | Tuesday, 12:00 pm
## Laura Gagliardi, University of Minnesota
#### Accurate Quantum Chemical Methods for Excited Electronic States and Transition-Metal Compounds
##### Chemistry
November 11, 2019
Kent 120 | Monday, 3:45 pm
## Yu-An Chen, Caltech
#### Exact bosonization in higher dimensions: from higher group bosonic SPT (symmetry protected topological) phases to Gu-Wen fermionic SPT phases.
November 11, 2019
MCP 201 | Monday, 1:30 pm
## Emily Balskus, Harvard University
#### Deciphering the human microbiota using chemistry
##### Closs Lecture
November 8, 2019
Kent 120 | Friday, 1:45 pm
## Wiggling in time
#### Using AFM to image polymer interfacial terrain
Let's eat at 12:00
Listen and discuss at 12:15
##### MRSEC Baglunch
November 8, 2019
GCIS E123 | Friday, 12:00 pm
## Lars Peter Hansen, University of Chicago
#### Climate Change: Uncertainty and Economic Policy
Geophysicists examine and document the repercussions for the earth’s climate induced by alternative emission scenarios and model specifications. Using simplified approximations, they produce tractable characterizations of the associated uncertainty. Meanwhile, economists write simplified damage functions to assess uncertain feedbacks from climate change back to the economic opportunities for the macroeconomy. How can we assess both climate and emissions impacts, as well as uncertainty in the broadest sense, in social decision-making?
In this lecture, Lars Peter Hansen will provide a framework for answering this question by embracing recent decision theory and tools from asset pricing, and applying this structure with its interacting components in a revealing quantitative illustration. In 2013, Hansen was a recipient of the Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel for his work advancing understanding of asset prices through empirical analysis. He is the director of the Macro Finance Research Program (MFR) and the David Rockefeller Distinguished Professor at the University of Chicago.
For more on “Pricing Uncertainty Induced by Climate Change,” read a reflection from Lars Peter Hansen, watch a conversation with co-author Michael Barnett or read the full paper.
##### Physics Colloquium
November 7, 2019
KPTC 113 | Thursday, 3:30 pm
## Anatoli Polkovnikov, Department of Physics, Boston University
#### Constructing Local Counterdiabatic Protocols in Complex Systems
In this talk I will discuss general idea of counterdiabatic driving allowing one to implement adiabatic protocols without usual long time constraints. The implications of such counterdiabatic driving range from designing efficient energy transfer in heat engines to quick high fidelity reparation of quantum states. While such protocols can not be exactly implemented in chaotic systems, one can design very good proxies for them and realize them without introducing additional controls using Floquet protocols. Studying an example of a specific nonintegrable spin model I will show that the generators of adiabatic transformations are highly anisotropic in the coupling space allowing one to define adiabatic flows connecting families of Hamiltonians. These flows are very reminiscent of Renormalization Group flows. I will also show that near singular (massively degenerate) points one can define special (dark) states which are very stable to adiabatic deformations. Such special states are analogous to recently discovered quantum scars. I will also mention how these ideas can be applied to construct effective low energy Hamiltonians extending the Schrieffer Wolff transformation beyond the perturbative regime. Host: Michael Levin, 2-7286 or via email to malevin@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### JFI Special Seminar
November 6, 2019
GCIS W301 | Wednesday, 2:30 pm
## Bill Baker, Skidmore, Owings & Merrill LLP
#### Maxwell, Rankine, Airy and Modern Structural Engineering Design
The lecture will review some of the seminal contributions of James Clerk Maxwell, William John Macquorn Rankine and George Biddell Airy to the theory of structures and how those theories can be applied to modern structural engineering design. William F. Baker is a consulting structural engineering partner at Skidmore, Owings & Merrill LLP where he has led the structural engineering practice for more than 20 years. Bill is best known for the development of the “buttressed core” structural system for the Burj Khalifa, the world’s tallest manmade structure. In addition to his work on supertall buildings, Bill’s expertise also extends to long-span roof structures and specialty structures. He has also collaborated with numerous artists, including Jamie Carpenter, Iñigo Manglano-Ovalle, James Turrell, and Jaume Plensa. Bill is an Honorary Professor at the University of Cambridge; he has received honorary doctorates from the University of Stuttgart, Heriot-Watt University, the Illinois Institute of Technology and the University of Missouri; the Gold Medal from the Institution of Structural Engineers (IStructE), the American Society of Civil Engineers (ASCE) Lifetime Award for Design; the Gustav Magnel Gold Medal from the University of Ghent; the Fazlur Rahman Khan Medal from the Council on Tall Buildings and Urban Habitat; and the Fritz Leonhardt Preis (Germany). He is a Fellow of both the ASCE and the IStructE, and a member of the National Academy of Engineering (USA) and an International Fellow of the Royal Academy of Engineering (United Kingdom). Bill is currently collaborating with faculty members from MIT, Cambridge, ETH/Zurich, and EPFL/Lausanne on a book intended to make Maxwell’s structural engineering work accessible to the modern engineer.
##### Computations in Science
November 6, 2019
KPTC 206 | Wednesday, 12:15 pm
## Mehran Kardar, Department of Physics, MIT
#### Diversity, Tolerance, and Maturation of the Adaptive Immune Response
The adaptive immune system protects the body from the ever-changing landscape of foreign microorganisms. The two arms of the adaptive immune system, T cells and B cells, mount specific responses to pathogens by utilizing the diversity of their receptors, generated through hypermutation. T cells recognize and clear infected hosts when their highly variable receptors bind sufficiently strongly to complexes formed with antigen-derived peptides displayed on the cell surface. To avoid auto-immune responses, a process of "Thymic Selection" ensures that only self-tolerant receptors (binding weakly to self peptides) are engaged. B cells generate antibodies that strongly bind and inactivate antigens (toxic targets). Potent antibodies are generated through the process of “Affinity Maturation" which is akin to evolution at a rapid pace. Methods from Statistical Physics can be used to model and elucidate these processes, as will be demonstrated through several examples. Host(s): Suri Vaikuntanathan, 2-7256 or via email to svaikunt@uchicago.edu and Vincenzo Vitelli, 4-8829 or by at viterlli@uchicago.edu. Persons who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
November 5, 2019
GCIS W301 | Tuesday, 3:45 pm
## Masahiro Hotta, Tohoku University
#### Quantum Information Capsules and Generalized Partners in Condensed Matters and Quantum Fields
Entangled many-body systems and quantum fields are capable of playing a role of quantum memory storage. When unknown parameters are imprinted to one subsystem by a fixed local unitary operation, we have three different quantum pictures for storing the information, Schmidt partner (ordinary partner), generalized partner, and quantum information capsule. In the first part of this talk, we will argue a counter-intuitive phenomenon of multiple qudits. Strong chaos generated by fast scrambling at high temperature yields an ordered information storage structure with decoupled quantum information capsules. A rotational isometry emerges in quantum Fisher information matrices. In the second part of this talk, I will provide a general formula of a purification partner mode associated with a particle mode detected by a generalized Unruh-DeWitt particle detector in quantum field theory. For particle creation processes by expanding universes and moving mirrors, we will discuss how a quantum field stores information of the expanding parameter and mirror trajectories in a detected particle and its partner. The moving mirror results may be expected to be checked by future experiments in quantum optics.
November 5, 2019
MCP 201 | Tuesday, 1:30 pm
## Terry Hwa, PhD, Department of Physics, University of California at San Diego
#### Bacterial growth laws & the origin of dimensional reduction
Extensive quantitative experiments on the model bacterium E. coli have established that many bacterial behaviors are organized in simple manners in accordance to the rate of cell growth. The existence of these simple empirical relations (growth laws) despite myriads of complex molecular interactions is a striking manifestation of a tremendous degree of dimensional reduction occurring in living cells. I will describe how the growth laws can be used to make accurate predictions of bacterial behaviors and discuss how the magic of dimensional reduction can be accomplished by bacterial cells through an ‘activity-based’ mode of gene regulation.
##### Biophysical Dynamics
November 5, 2019
GCIS W301 | Tuesday, 12:00 pm
## Jefferson Chan, University of Illinois, Urbana-Champaign
#### Expanding the Chemical Tool Box for Acoustic-based Imaging of Cancer
##### Chemistry
November 1, 2019
Kent 120 | Friday, 1:45 pm
## The gel that knew too much
Eat 12:00
Main event: 12:15
##### MRSEC Baglunch
November 1, 2019
GCIS E123 | Friday, 12:00 pm
## Zhirong Huang, Stanford University
#### X-ray Free-Electron Lasers: Past, Present and Future
The world’s first hard X-ray Free Electron Laser (FEL), Linac Coherent Light Source (LCLS), started its operation 10 years ago at SLAC and opened a new era of ultrafast X-ray science. The success of the LCLS inspired the worldwide development of X-ray FELs. At the present moment, LCLS is undergoing a major upgrade to provide significant enhancement in its capability. In this talk, I will describe the physical mechanism and characteristics of X-ray FELs, present some of the most exciting results in LCLS, and discuss R&D challenges for future opportunities.
##### Physics Colloquium
October 31, 2019
KPTC 112 | Thursday, 3:30 pm
## Lukas Muechler
#### Flatiron Institute, New York
In this talk I will discuss notions of how strong correlations and topology can be found in molecular systems. Motivated by the concept of Mobius aromatics in organic chemistry, I extend the recently introduced concept of fragile Mott insulators (FMI) to ring-shaped molecules with repulsive Hubbard interactions threaded by a half-quantum of magnetic flux ($hc/2e$). In this context, a FMI is the insulating ground state of a finite-size molecule that cannot be adiabatically connected to a single Slater determinant, i.e., to a band insulator, provided that time-reversal and lattice translation symmetries are preserved. I establish a duality between Hubbard molecules with $4n$ and $4n+2$ sites, with $n$ integer. A molecule with $4n$ sites is an FMI in the absence of flux but becomes a band insulator in the presence of a half-quantum of flux, while a molecule with $4n+2$ sites is a band insulator in the absence of flux but becomes an FMI in the presence of a half-quantum of flux.
Based on these results, I propose a topological classification of molecules and their chemical reactions with and without many-body interactions. I consider 0-dimensional molecular Hamiltonians in a real-space tight-binding basis with time-reversal symmetry and an additional spatial reflection symmetry. On a single particle level, the reflection symmetry gives rise to a perplectic structure which can be probed by a Wilson loop after a flux-insertion. The classification in terms of Wilson loops remains stable in the presence of many-body interactions, which can be explained by the presence of zeros of the interacting single particle Green's function. I argue that this topological classification has a universal contribution to the rate constants of chemical reactions and apply my theory to a class of reactions studied by Woodward and Hoffmann, where a reflection symmetry is preserved along a one-dimensional reaction path.
##### Special JFI Seminar
October 31, 2019
GCIS E123 | Thursday, 12:30 pm
## Yonggang Huang Walter P. Murphy Professor of Engineering Northwestern University
#### Mechanics-guided Deterministic 3D Assembly
Complex three-dimensional (3D) structures in biology form naturally to provide essential functions in even the most basic forms of life. Compelling opportunities exist for analogous 3D architectures in human-made devices, but design options are constrained by existing capabilities in materials growth and assembly. We report routes to previously inaccessible classes of 3D constructs in advanced materials, including device-grade silicon. The schemes involve geometric transformation of 2D micro/nanostructures into extended 3D layouts by compressive buckling. Designs inspired by kirigami/origami, releasable multilayers and engineered substrates enable the formation of mesostructures with a broad variety of 3D geometries, either with hollow or dense distributions. Demonstrations include experimental and theoretical studies of more than 100 representative geometries, from single and multiple helices, toroids, and conical spirals to structures that resemble spherical baskets, cars, houses, cuboid cages, starbursts, flowers, scaffolds, each with single- and/or multiple-level configurations. Morphable 3D mesostructures whoese geometries can be elastically altered can be further achieved via nonlinear mechanical buckling, by deforming the elastomer platforms in different time sequences. Compatibility with the well-established technologies available in semiconductor industries suggests a broad range of application opportunities.
##### Molecular Engineering
October 30, 2019
ERC 301B | Wednesday, 3:45 pm
## Ben Nachman, Lawrence Berkeley National Laboratory
#### Exploring hypervariate phase space with likelihood-free and label-free deep learning
Precise scientific analysis in collider-based particle physics is possible because of complex simulations that connect fundamental theories to observable quantities. These simulations have been paired with multivariate methods for many years in search of the smallest distance scales in nature. Deep learning tools hold great promise to qualitatively change this paradigm by allowing for holistic analysis of data in its natural hyperdimensionality with thousands or millions of features instead of up to tens of features. These tools are not yet broadly used for all areas of data analysis because of the traditional dependence on simulations. In this talk, I will discuss how we can change this paradigm in order to exploit the new features of deep learning to explore nature at sub-nuclear distance scales. In particular, I will show how neural networks can be used to (1) overcome the challenge of intractable hypvervariate probability density modeling and (2) learn directly from (unlabeled) data to perform hypothesis tests that go beyond any existing analysis methods. The talk will end with a brief discussion of challenges for hypervariate deep learning analysis. While my examples will be from particle physics, it is likely that these tools have a much broader applicability across fundamental physics and beyond. I will keep the particle physics jargon minimal in order to facilitate discussions about connections to your area of science!
##### Computations in Science
October 30, 2019
KPTC 206 | Wednesday, 12:15 pm
## Ben O'Shaughnessy, Columbia University
#### How Does the Actomyosin Contractile Ring Divide Cells?
Cells use actomyosin contractility for many purposes. Actomyosin-mediated forces regulate cell shape, power migration of immune cells, create cortical flows to establish cell polarity in early embryos, and power coordinated deformations during tissue morphogenesis. Among the most important and intensively studied actomyosin cellular systems is the cytokinetic contractile ring that constricts and divides cells at the end of the cell cycle during cytokinesis. This remarkable machine generates sufficient force for division, but with the right timing and constriction rate to accurately partition chromosomes to the two daughter cells. I will describe our efforts to understand the cytokinetic contractile ring in fission yeast, using computational modeling, analytical approaches and experiment. Fission yeast offers a unique opportunity for realistic experimentally-driven mathematical modeling of the ring, because many key components are biochemically characterized and their amounts measured throughout cytokinesis. Moreover, their organization is beginning to emerge from conventional and super-resolution microscopies. This talk will address several fundamental questions about this cellular machine. How does the contractile ring generate tension? How does it remain functional while shedding its parts and shortening? How do the myosin-II isoforms and other components coordinate to produce organization and force? How are contractile instabilities combatted? What sets the constriction rate, and how does this depend on tension? From theoretical analysis, experimental measurements of ring tension and a wealth of experimental background, I will argue that for fission yeast a rather unified picture emerges that answers these questions.
Host: Gregory Voth, 2-9092 or via email gavoth@uchicago.edu. Persons who need assistance please contact Brenda Thomas, 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
October 29, 2019
GCIS W301 | Tuesday, 3:45 pm
## Ray Moellering:,University of Chicago
#### Chemical Proteomic Platforms to Expose and Exploit Novel Metabolic Signals in Disease
##### Chemistry
October 28, 2019
Kent 120 | Monday, 3:45 pm
## Ron Naaman, Department of Chemical and Biological Physics, Weizmann Institute
#### The Relation Between Chiral Molecules and the Electron Spin - The Key to Almost Everything
Spin based properties, applications, and devices are commonly related to magnetic effects and to
magnetic materials. However, we found that chiral organic molecules act as spin filters for photoelectrons transmission, in electron transfer, in electron transport. The new effect, termed Chiral Induced Spin Selectivity (CISS), [ 1 , 2 ] was found, among others,in bio-molecules and in bio-systems. It has interesting implications for the production of new types of nano-size spintronics devices [ 3 , 4 ] and on electron transfer in biological systems. We
observed that charge polarization in chiral molecules is accompanied by spin polarization. This finding sheds new light on enantio-specific interactions and it allows to construct novel methods for enantio-separation.[ 5 ] It also opens new ways in interface-spintronics, when chiral molecules are adsorbed on semiconductor surfaces [ 6 ] or on ferromagnetic substrates.
[1] R. Naaman, Y.Paltiel, David Waldeck, Nature Reviews Chemistry 3, 250 (2019).
[2] R. Naaman, D. H. Waldeck Ann. Rev. Phys. Chem. 66, 263 (2015).
[3] O. Ben Dor, S. Yochelis, A. Radko, K. Vankayala, E. Capua, A. Capua, S.-H. Yang, L. T.
Baczewski, S. S. P. Parkin, R. Naaman, and Y. Paltiel, Nat. Comm., 8, 14567 (2017).
[4] K. Michaeli, V. Varade, R. Naaman, D. Waldeck, Journal of Physics: Condensed Matter, 29,
103002 (2017).
[5] K. Banerjee-Ghosh, O. Ben Dor, F. Tassinari, E. Capua, S. Yochelis, A. Capua, S.-H. Yang,
S. S. P. Parkin, S. Sarkar, L. Kronik, L. T. Baczewski, R. Naaman, Y. Paltiel, Science 360, 1331
(2018).
[6] E. Z. B. Smolinsky, A. Neubauer, A. Kumar, S. Yochelis, E. Capua, R. Carmieli, Y.Paltiel,
R. Naaman, K. Michaeli, J. Phys. Chem. Lett. 10, 1139 (2019).HOST: Steven J. Sibner, 2-7193 or by email to 2-sibner@uchicago.edu
##### JFI Special Seminar
October 28, 2019
GCIS W301 | Monday, 1:30 pm
## Jennifer Prescher, University of California, Irvine
#### Spying on Cellular Communication with Chemical Tools and Noninvasive Imaging
Cellular networks drive diverse aspects of human biology. Breakdowns in cell-to-cell communication also underlie numerous pathologies. While cellular interactions play key roles in human health and disease, the mechanisms by which cells transact information in vivo are not completely understood. The number of cells types involved, the timing and location of their interactions, the molecular cues exchanged, and the long-term fates of the cells remain poorly characterized in most cases. This is due, in part, to a lack of tools for observing collections of cells in their native habitats. My group is developing novel imaging probes to “spy” on cells and decipher their communications in vivo. Examples of these probes, along with their application to studies of cancer progression and host-pathogen interactions, will be discussed.
##### Chemistry
October 25, 2019
Kent 120 | Friday, 1:45 pm
## Donna Strickland, University of Waterloo Event Type
#### Generating High-Intensity, Ultrashort Optical Pulses
With the invention of lasers, the intensity of a light wave was increased by orders of magnitude over what had been achieved with a light bulb or sunlight. This much higher intensity led to new phenomena being observed, such as violet light coming out when red light went into the material. After Gérard Mourou and I developed chirped pulse amplification, also known as CPA, the intensity again increased by more than a factor of 1,000 and it once again made new types of interactions possible between light and matter. We developed a laser that could deliver short pulses of light that knocked the electrons off their atoms. This new understanding of laser-matter interactions, led to the development of new machining techniques that are used in laser eye surgery or micromachining of glass used in cell phones.
##### Physics Colloquium
October 24, 2019
KPTC 111 | Thursday, 3:30 pm
## David Schwab, CUNY
#### How noise affects the Hessian spectrum in overparameterized neural networks
Stochastic gradient descent (SGD) forms the core optimization method for deep neural networks, contributing to their resurgence. While some theoretical progress has been made, it remains unclear why SGD leads the learning dynamics in overparameterized networks to solutions that generalize well. Here we show that for overparameterized networks with a degenerate valley in their loss landscape, SGD on average decreases the trace of the Hessian of the loss. We also show that isotropic noise in the non-degenerate subspace of the Hessian decreases its determinant. In addition to explaining SGDs role in sculpting the Hessian spectrum, this opens the door to new optimization approaches that guides the model to solutions with better generalization. We test our results with experiments on toy models and deep neural networks.
##### Computations in Science
October 23, 2019
KPTC 206 | Wednesday, 12:15 pm
## Hanhee Paik, IBM Q - T. J. Watson Research Center
#### Benchmarking Quantum Computers and Future Directions for Superconducting Quantum Hardware
While the fully fault-tolerant universal quantum computing system is still many years ahead, building an early quantum computer with quantum advantage becomes a feasible near-term milestone that we can realistically plan. Increasing number of near-term applications has been accelerating the development of quantum hardware in the industries, and as quantum system size grows, we need a whole system metric to evaluate the level of hardware performance. I would like to introduce the quantum volume (arXiv:1811.12926) as a system-level metric that quantifies quantum computational power of early quantum computing processors, and will present an example of performance comparison among IBM Q public quantum processors in the cloud. The quantum volume depends on various individual component metrics such as gate fidelity and crosstalk. I will discuss some of the challenges in building superconducting quantum hardware and suggest few directions to improve the quantum volume. Host: Aziza Suleymanzade, 2-8928 or via email at azizadubna@gmail.com. Persons who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday Seminar - JFI Women in Science
October 22, 2019
GCIS W301 | Tuesday, 3:45 pm
## Johan Elf PhD, Molecular Systems Biology, Department of Cell & Molecular Biology Uppsala University, Sweden
#### Imaging-based live cell CRISPRi screening
Our ability to connect genotypic variation to biologically important phenotypes has been seriously limited by the gap between live cell microscopy and library-scale genomic engineering. Specifically, this has restricted studies of intracellular dynamics to one strain at a time and thus, generally, to the impact of genes with known function. I will show how in situ genotyping of a library of E. coli strains after time-lapse imaging in a microfluidic device overcomes this problem. We determine how 235 different CRISPR interference (CRISPRi) knockdowns impact the coordination of the replication and division cycles of E. coli by monitoring the location of replication forks throughout on average >500 cell cycles per knockdown. The single-cell time-resolved assay allows us to determine the distribution of single-cell growth rates, cell division sizes, and replication initiation volumes. Subsequent in situ genotyping allows us to map each phenotype distribution to a specific genetic perturbation in order to determine which genes are important for cell cycle control. I will also discuss the implications for mechanistic models of replication initiation.
##### Biophysical Dynamics
October 22, 2019
GCIS W301 | Tuesday, 12:00 pm
## Suri Vaikuntanathan, University of Chicago
##### Chemistry
October 21, 2019
Kent 120 | Monday, 3:45 pm
## Ying Lin, Caltech
#### Anomalies and Bounds on Charged Operators
We study the implications of 't Hooft anomaly (i.e. obstruction to gauging) on conformal field theory, focusing on the case when the global symmetry is Z2. Using the modular bootstrap, universal bounds on (1+1)-dimensional bosonic conformal field theories with an internal Z2 global symmetry are derived. The bootstrap bounds depend dramatically on the 't Hooft anomaly. In particular, there is a universal upper bound on the lightest Z2 odd operator if the symmetry is anomalous, but there is no bound if the symmetry is non-anomalous. In the non-anomalous case, we find that the lightest Z2 odd state and the defect ground state cannot both be arbitrarily heavy. We also consider theories with a U(1) global symmetry, and comment that there is no bound on the lightest U(1) charged operator if the symmetry is non-anomalous. We end with a discussion about the constraints on symmetry-protected gapless phases and introduce the notion of "category-protected gapless phases.
October 21, 2019
MCP 201 | Monday, 1:30 pm
## Gregory Girolami, University of Illinois
##### Chemistry
October 18, 2019
Kent 120 | Friday, 1:45 pm
## Sand castles with quantum dots
Self-assemble 12:00
Self-activate 12:15
##### MRSEC Baglunch
October 18, 2019
GCIS E123 | Friday, 12:00 pm
## Cristina Marchetti, University of California Santa Barbara
#### Active Topology
In two-dimensional systems, such as thin films of superfluids, crystals, liquid crystals and magnets, topological defects are key to understanding the transition between ordered and disordered states. Almost fifty years ago, Berezinskii, Kosterlitz and Thouless showed that these systems disorder through a topological phase transition associated with the proliferation of unbound pairs of vortices of opposite charge. The essence of this transition relies on the mapping of the statistical physics of defects onto a Coulomb gas. In active liquid crystals, topological defects become motile particles and drive the transition from spontaneous laminar flow to self-sustained turbulent-like motion. In this talk I will outline the statistical physics of defects in active nematics and their possible role in materials science and biology. By viewing the active nematic as a collection of swarming and interacting active defects, the onset of active turbulence can be described as an activity-driven defect unbinding transition. A hydrodynamic theory of a gas of unbound defects captures a new state of hierarchically organized active matter - a defect flock where defects themselves line up and order into a collectively flowing liquid. The hydrodynamic treatment of active defects provides a framework to address fundamental questions of defect organization in active matter and paves the way for the design of active devices with targeted transport functionalities through the controlled variation of activity.
##### Physics Colloquium
October 17, 2019
KPTC 110 | Thursday, 3:30 pm
## Rebecca Kramer-Bottiglio, Yale University
#### From Particles to Parts—Building Multifunctional Robots with Programmable Robotic Skins
Robots generally excel at specific tasks in structured environments, but lack the versatility and adaptability required to interact-with and locomote-within the natural world. To increase versatility in robot design, my research group is developing robotic skins that can wrap around arbitrary deformable objects to induce the desired motions and deformations. Our robotic skins integrate programmable composites to embed actuation and sensing into a planar substrate that may be applied-to, removed-from, and transferred-between different objects to create a multitude of controllable robots with different functions to accommodate the demands of different environments. We have shown that attaching the same robotic skin to a deformable object in different ways, or to different objects, leads to unique motions. Further, we have shown that combining multiple robotic skins enables complex motions and functions. During this talk, I will demonstrate the versatility of this soft robot design approach by showing robotic skins in a wide range of applications - including manipulation tasks, locomotion, and wearables - using the same 2D robotic skins reconfigured on the surface of various 3D soft, inanimate objects.
##### Computations in Science
October 16, 2019
KPTC 206 | Wednesday, 12:15 pm
## Joerg Wrachtrup, University of Stuttgart,Germany
#### Nanoscale quantum sensing
The accuracy of measurements is limited by quantum mechanics. Ingenious demonstrations, like measuring gravitational fields or time have explored accuracy limits and reached fundamental obstructions. Yet, precision measurements so far are restricted to macroscale and dedicated environments.
In the talk, Prog. Wrachtrup will discuss spin quantum sensors comprising single electron spins plus a nuclear spin quantum register. With such a system we measure a variety of quantities, including electric and magnetic fields, temperature, and force. We use nuclear spins to enhance the measurement accuracy of the electron spin, serving as ancillary quantum memory bits or as quantum register for quantum Fourier transformation. Prog. Wrachtrup will present a variety of applications ranging from quantum simulations to imaging of magnetic nanostructures, precision measurements of mass changes or the structure of thin liquid layers on surfaces.
##### PME Distinguished Colloquium
October 16, 2019
ERC 161 | Wednesday, 11:00 am
## Dmitry Abanin, University of Geneva
#### Non-Equilibrium Dynamics Through the Prism of Quantum Entanglement
Remarkable experimental advances of the past decade have opened the door to probing highly non-equilibrium dynamics of quantum many-body systems. When an interacting system is prepared in a non-equilibrium state, its evolution often leads to an effective thermal equilibrium. However, as was recently demonstrated theoretical and experimentally, that there are quantum phases of matter which do not thermalize, and therefore cannot be described by statistical mechanics. In this talk, I will describe how using insights from quantum entanglement of many-body states enabled progress in understanding such phases. I will focus on three distinct mechanisms to avoid thermalization: many-body localization (MBL), the recently discovered quantum many-body scars, and frustrated glassy spin systems. Non-thermalization protects quantum coherence, leading to a wealth of new dynamical phenomena and opening attractive opportunities for controlling quantum matter.Host: Michael Levin, 2-7286 or via email to maleavin@uchicago.edu. Persons who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
October 15, 2019
GCIS W301 | Tuesday, 3:45 pm
## Stefano Sacanna, New York University
#### Engineering Colloidal Matter
##### Chemistry
October 14, 2019
Kent 120 | Monday, 3:45 pm
## Jeff McMahon, University of Michigan
#### Advancing CMB Cosmology: ACTPol, Simons Observatory, and CMB-S4
Measurements of the cosmic microwave background (CMB) are a powerful probe of the origin, contents, and evolution of our Universe. CMB measurements continue to improve according to a Moore’s law under which the mapping speed of experiments improves by an order of magnitude roughly every five years. This rapid progression in our ability to measure the CMB has translated into a series of scientific advances including showing our universe to be spatially flat, constraining inflationary and alternative theories of the primordial universe, and providing a cornerstone for our precision knowledge of the Lambda-CDM model. Observations with the current generation of experiments, including Advanced ACTPol, will soon produce improved cosmological constraints. Building on this work, in the coming decade Simons Observatory and ultimately CMB-S4 will: pass critical thresholds in constraints on inflation and light relativistic species; provide improved measurements of dark energy, dark matter, neutrino masses, and enable searches for new surprises.
In this talk I present the design and status of measurements with Advanced ACTPol and how we are building on this work to realize the next generations of experiments including Simons Observatory and CMB-S4. I will highlight the technological advances that underlie the rapid progress in measurements including: polarization sensitive detectors which simultaneously observe in multiple colors; metamaterial optical elements; and overall advances in experimental design. I will present preliminary new results from ACTPol and conclude with science forecasts for the coming decade.
##### Physics Colloquium
October 14, 2019
KPTC 109 | Monday, 3:30 pm
#### Chiral charge dynamics in Abelian gauge theories at finite temperature
he chiral anomaly present in the standard model can have important phenomenological consequences, especially in cosmology and heavyions physics. In this talk, I will focus on the contribution from the Abelian gauge fields. Despite an absence of topologically distinct sectors, they have a surprisingly rich vacuum dynamics, partly because of the chiral anomaly. I will present results obtained from real-time classical lattice simulations of a U(1) gauge field in the presence of a chiral chemical potential. They account for short distance fluctuations, contrary to effective descriptions such as Magneto-Hydrodynamics (MHD). I will discuss various phenomena, like inverse magnetic cascade, which occur in this system. In particular, in presence of a background magnetic field, the chemical potential exponentially decays. The associated chiral decay rate is related to the diffusion of the Abelian Chern-Simons number in a magnetic background, in the absence of chemical potential. The rate obtained from the simulations is an order of magnitude larger than the one predicted by MHD. If this result is shown to be robust under corrections such as Hard Thermal Loops, it will call for a revision of the implications of fermion number and chiral number non-conservation in Abelian theory at finite temperature.
October 14, 2019
MCP 201 | Monday, 1:30 pm
## Out in the PSD & PME Exhibit and Speaker Series
We invite you to join us for the inaugural: OUT IN THE PSD & PME EXHIBIT & SPEAKER SERIES
Celebrating the voices of LGBTQ+ people and allies in STEM.
The exhibit will feature portraits of our community members and narratives about the often life-long process of coming out.
Opening Reception: October 11, 2019, 4 - 6pm in the ERC Atrium
##### Molecular Engineering
October 11, 2019
ERC Atrium | Friday, 4:00 pm
## Shinsei Ryu, University of Chicago
#### Holographic Quantum Matter and Entanglement Negativity
Quantum entanglement has been proven to be a key concept in condensed matter physics. It provides conceptual foundations to develop deep understanding of many-body quantum systems, and uncovers many novel phenomena in condensed matter physics. In this talk, I will discuss the entanglement negativity, a measure of quantum entanglement valid for mixed quantum states, in the context of holographic systems -- these are quantum many-body systems which admit their descriptions in terms of gravitational theory in one higher dimensions. We in particular discuss a holographic object which is dual to the entanglement negativity in holographic quantum matter.
##### Physics Colloquium
October 11, 2019
KPTC 108 | Friday, 3:30 pm
## Ed Bertschinger, MIT
#### Departments That Excel In Equity, Diversity, and Inclusion at Chicago and Across the Nation
Women and people of color are severely underrepresented in many STEM departments, especially in physical sciences and engineering. Professional societies and universities have issued reports full of recommendations, but change is slow and difficult. This talk will identify departments that are most successful in diversifying bachelor's and doctoral degrees in STEM. Using data on student and faculty demographics, departmental practices where they are known, and interviews where they are available, I will present evidence as to how successful departments in physics, engineering, and other STEM departments at Chicago, MIT, and across the nation succeed in creating environments where all students can thrive.
##### Physics Colloquium
October 10, 2019
KPTC 107 | Thursday, 3:30 pm
## Massimiliano Delferro, PhD., Argonne National Laboratory
#### Catalytic Recycling and Upcycling of Polyofins
Synthetic polymers are ubiquitous and critical to the function of modern life. However, the ubiquity of polymers has resulted in an enormous and growing amount of polymer waste, which has a long lifetime in the environment and is inefficient to recycle. Here, we have discovered Well-dispersed Pt nanoparticles supported on SrTiO3 nanocuboids by atomic layer deposition were shown to be capable of converting PE (8,000 – 158,000 Da) into value-added high-quality liquids (HQLs) by hydrogenolysis at 170 psi H2 and 300 °C under solvent-free conditions. Adsorption of PE on the catalytic surfaces plays a significant role in selective hydrogenolysis, as shown by catalytic, solid-state NMR of adsorbed 13C-enriched PE, and density functional theory. We attribute the formation of uniform low dispersity products to a combination of preferential binding of high molecular weight PE on the catalyst surface and stronger adsorption of PE to Pt than to the SrTiO3 support.
##### Molecular Engineering
October 10, 2019
ERC 201 | Thursday, 1:00 pm
###### Thu 10
The STEM Broader Impacts Fair provides outreach and volunteer opportunities for faculty, graduate students, and students in the College. Participants will meet organizations looking to work with scientists at every level. The 2019 Broader Impacts Fair will occur October 10 from 12-2:00 p.m. in the ERC Atrium.
If you represent an organization that offers outreach and volunteer opportunities for scientists and STEM students, please complete this form or contact Jennifer Woods at jqwoods@uchicago.edu
##### Molecular Engineering
October 10, 2019
ERC Atrium | Thursday, 12:00 pm
## Feng Wang, Department of Physics, University of California Berkeley
#### Engineering Correlation and Topology in Two-Dimensional Moire Superlattices
Van der Waals heterostructures of atomically thin crystals offer an exciting
new platform to design novel electronic and optical properties. In this talk,
I will describe how to engineer correlated and topological physics using
moire superlattice in two dimensional heterostructures. I will show that we
can realize and control extremely rich condensed matter physics, ranging
from correlated Mott insulator and superconductivity to ferromagnetism
and topological Chern insulator, in a single device featuring the ABC
trilayer graphene and boron nitride moire superlattices.
##### JFI Special Seminar
October 10, 2019
GCIS E123 | Thursday, 10:30 am
## Arvind Murugan, University of Chicago
#### Transients in physics and biology
We tend to characterize simple and complex systems in terms of their steady state properties. Transients before reaching a steady state are seen as a temporary annoyance, even in non-equilibrium systems. However, transients are all important in understanding a system in a time varying environment where the environmental changes are neither slow (adiabatic) nor fast compared to the internal dynamics of the system. We show how transients can be exploited to counter fast evolving viruses, design adaptable materials and to implement recursive Bayesian algorithms using biomolecules. Along the way, we discuss choices a physicist has in picking problems in biology and roads not taken.
##### Computations in Science
October 9, 2019
KPTC 206 | Wednesday, 12:15 pm
## Cory Dean, Department of Physics - Columbia University
#### Engineering 2D Materials With a Twist
Atomically thin crystals such as graphene, boron nitride and the transition metal dichalcogenides continue to attract enormous interest. Encompassing a wide range of properties, including single-particle, topological and correlated phenomenon, these 2D materials represent a rich class of materials in which to explore both novel physical phenomenon and new technological pursuits. By integrating these materials with one another, an exciting new opportunity has emerged in which entirely new layered heterostuctures can be fabricated with emergent properties beyond those of the constituent materials. In this talk I will discuss some of our recent efforts where, by tuning the geometry of these heterostructures at the nanoscale, we are able to realize yet a new level of control over their electronic properties. In particular I will discuss the significant role played by the rotational alignment between adjacent layers and the approach we are taking towards manipulating this degree of freedom to dynamically tune device properties in ways that are not possible with conventional materials.
Host: Jiwoong Park, 4-3179 or via email at jwpark@uchicago.edu. Persons who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu
##### The Tuesday JFI Seminar
October 8, 2019
GCIS W301 | Tuesday, 3:45 pm
## Sophie Dumont, PhD, Cell & Tissue Biology, UCSF
#### Cell Division: Mechanical Integrity with Dynamic Parts
The spindle segregates chromosomes at cell division. To perform its function, the spindle must be flexible and dynamic over short timescales, and yet maintain its architecture, integrity and function over long timescales. How it does so is poorly understood. I will begin by presenting our efforts to understand how the mammalian spindle’s steady-state architecture emerges, far from equilibrium. We show that microtubule minus-end clustering is required for the spindle to reach a steady-state geometry – and that without it the spindle becomes turbulent. I will then present our work aiming to understand ho! w the spindle’s mechanical integrity emerges from its dynamic parts. Inspired by Nicklas’ classic experiments, we pull on the mammalian spindle inside cells using microneedles, and use this approach to probe how different spindle components are dynamically connected in space and time. Looking forward, we hope that this work will inform on simple design rules that allow the spindle to be dynamic yet robust – two properties central to its function.
##### Biophysical Dynamics
October 8, 2019
GCIS W301 | Tuesday, 12:00 pm
## John Anderson, University of Chicago
#### Synthesis and Reactivity of a Terminal Co Oxo Complex
##### Chemistry
October 7, 2019
Kent 120 | Monday, 3:45 pm
## Anton Kapustin, Caltech
#### Chiral central charge and the Thermal Hall effect on the lattic
It is well-known that the zero-temperature Hall conductance of a 2d system can be interpreted both as a bulk transport coefficient and a U(1) anomaly for the edge modes. The former interpretation allows one to write down a simple formula for it (Kubo formula). The latter interpretation explains why Hall conductance is a topological invariant. In this talk I will explain the difficulties in extending these considerations to the thermal Hall conductance and how they are overcome. I will argue that the thermal Hall conductance should be regarded as an exact 1-form on the parameter space rather than a function. I will explain how to write-down a Kubo-like formula for this 1-form. Further, I show that the low-temperature thermal Hall conductance of a gapped 2d system is robust under arbitrary deformations which do not close the gap and can be identified with the chiral central charge for the edge modes. This provides the bulk-boundary correspondence for the chiral central charge.
October 7, 2019
MCP 201 | Monday, 1:30 pm
## How to cook a turbulent puff using vortex rings
#### How does nature eat it up?
12:00 Eat. Bring a puff
12:15 See the puff motion picture
##### MRSEC Baglunch
October 4, 2019
GCIS E123 | Friday, 1:00 pm
## David Miller, University of Chicago
#### Exploring the Particle Universe at the Energy Frontier
Quarks and gluons are ubiquitous in the debris of the proton-proton collisions of the Large Hadron Collider (LHC), but they can also signal the presence of massive particles that are signs of new physics: they are the needle in the proverbial haystack…of needles. However, for the first time in the history of particle physics, the collision energy at the LHC is often well above the scale of electroweak symmetry breaking. I will walk you through why the LHC is such a fantastic “quark and gluon” machine, how new techniques to image the events observed at the LHC allow us probe jets — the observable manifestation of quarks and gluons — in exquisite detail, and present results in searching for signs of new physics using Lorentz-boosted object tagging approaches in the ATLAS Experiment. These techniques are being deployed with great success successfully in searches for new particles and precision measurements of the Standard Model, in both of which my group is deeply involved. I will then look toward the future and describe new instrumentation and algorithms that we’re developing to identify and record Lorentz-boosted hadronic objects in future runs of the LHC.
##### Physics Colloquium
October 3, 2019
KPTC 106 | Thursday, 3:30 pm
## Daniel Fisher, Stanford University
#### Evolution, Ecology, and Chaos: Questions and Simple Models
Recent observations of bacterial populations in the laboratory and in natural environments have exacerbated long-standing puzzles about evolution: Can evolution in a fixed environment continue forever? Why is there so much diversity on all scales, including coexistence of many within-species variants? A key role of theory in biology is to ask what is truly puzzling and what can already arise in simple models and thus should perhaps not be so puzzling. Some progress on these questions by statistical physics approaches will be the focus of this talk.
##### Computations in Science
October 2, 2019
KPTC 206 | Wednesday, 12:15 pm
## Yueh-Lin (Lynn) Loo, Ph.D., Princeton University, the Director, Andlinger Center for Energy and the Environment and Chemical & Biological Engineering Department
#### Making Smart Windows Smarter: symbiotic pairing of near-UV solar cells with electrochromic windows for visible light + heat management in architectural applications
##### Molecular Engineering
October 2, 2019
ERC 161 | Wednesday, 11:00 am
#### "Ask me anything” with the Physical Review Editors
The Physical Review journals published by APS have served as the bedrock of physics research for a long time. Technological developments and a changing publishing landscape are posing challenges to long-held publishing traditions. Join this editorial session and get answers to your questions about publishing in physics from the editors for Physical Review.
The Editors: Serena Bradde (Physical Review E) received her Ph.D. from SISSA in Trieste, Italy. She did postdoctoral research at the Memorial Sloan Kettering Cancer Center (NYC), the Institut Pasteur (France), and the CUNY (NYC). She joined Physical Review E in 2016. Her expertise is in theoretical statistical and biological physics and complex systems.
Dario Corradini (Physical Review X) received his Ph.D. in computational physics from University Roma Tre, Italy. He did his postdoctoral research at Boston University and as a CNRS research fellow at Pierre and Marie Curie University (Paris) and at École Normale Supérieure. He joined PRX in 2015. His expertise include theoretical statistical physics of complex liquids and ionic materials, as well as biological and environmental physics.
##### Special Seminar
October 2, 2019
GCIS W301 | Wednesday, 10:00 am
## Aparna Baskaran, Department of Physics - Brandeis University
#### Active Matter: Applying Materials Physics Paradigm to
Active matter is a term that has come to describe diverse systems from flocking animals to the cytoskeleton of a cell. In this talk I will give an overview of the theoretical paradigm that unifies these diverse systems and discuss some results from minimal models for self propelled particles and suspension of cytoskeletal filaments. Host: Suri Vaikuntanathan, 2-7256 or via email to svaikuntanathan@uchicago.edu. Persons who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The 1st Tuesday JFI Colloquium
October 1, 2019
GCIS W301 | Tuesday, 4:00 pm
## Will Greenleaf, Stanford
#### Exploring the physical genome…
##### Biophysical Dynamics
September 30, 2019
GCIS W301 | Monday, 12:00 pm
## Closs Lecture: Professor Dr. Benjamin List: Max-Planck-Institute
#### Very Strong and Confined Chiral Acids: Universal Catalysts for Asymmetric Synthesis?
##### Closs Lecture
September 27, 2019
Kent 120 | Friday, 1:45 pm
## Boris Rybtchinski, Weizmann Institute of Science
#### Noncovalent Aqua Materials
Materials based on small molecules that are held together by noncovalent interactions can offer an alternative to conventional polymer materials for applications that require adaptive and stimuli-responsive features. However, it is challenging to engineer macroscopic noncovalent materials that are sufficiently robust for practical applications. We will describe our work on “aqua materials” based on well-defined organic molecules. These materials are uniquely assembled in aqueous media, where they harness the strength of the hydrophobic and π-π interactions to achieve robustness. Despite their high stability, these supramolecular systems can dynamically respond to external stimuli. We discuss design principles, fundamental properties and applications of two classes of aqua materials: (1) supramolecular gels and (2) nanocrystalline arrays. The functional materials based on them include recyclable filtration membranes for preparative nanoparticle separation, water purification and catalysis, as well as nanocrystalline films for switchable surface coatings and optoelectronic devices.
##### Molecular Engineering
September 25, 2019
ERC 201 | Wednesday, 11:00 am
## Bo Huang, Pharmaceutical Chemistry and Biochemistry/Biophysics, University of California, San Francisco
#### Mapping the inner world of cells
Cellular processes are orchestrated by a large number of biomolecules in a spatially and temporally coordinated manner within a tiny volume. To uncover the underlying organizational principles and their functional relevance, we are developing new fluorescent labeling methods and microscopy techniques to systematically map the spatial localization, temporal dynamics and activity profiles of proteins. In particular, we have developed the split fluorescent protein tagging method that allows large-scale generation of cell lines with endogenously-labeled proteins by CRISPR/Cas9-mediated gene editing. Correspondingly, we have also built a single-objective high-resolution light-sheet microscope that enables high-throughput imaging of these cell lines. These tools have led to out elucidation of how cytoplasmic protein granules formed by oncogenic kinase fusions activate Ras signaling in cancer cells.
##### Biophysical Dynamics
September 24, 2019
GCIS W301 | Tuesday, 12:00 pm
## Anatoly B. Kolomeisky, Rice Univerity
#### When Will the Cancer Start?
Cancer is a genetic disease that results from accumulation of unfavorable mutations. As soon as genetic and epigenetic modifications associated with these mutations become strong enough, the uncontrolled tumor cell growth is initiated, eventually spreading through healthy tissues. Clarifying the dynamics of cancer initiation is thus critically important for understanding the molecular mechanisms of the cancer appearance and spreading. Here we present a new theoretical approach to evaluate the dynamic processes associated with the cancer initiation. It is based on a discrete-state stochastic description of the formation of tumors as a fixation of unfavorable mutations in tissues. Using a first-passage analysis, the probabilities for the cancer to appear and the average times before it happens, which are viewed as fixation probabilities and fixation times, respectively, are explicitly calculated. It is predicted that the slowest cancer initiation dynamics is observed for neutral mutations, while it is fast for both advantageous and, surprisingly, disadvantageous mutations. The method is applied for estimating the cancer initiation times from clinical data on lifetime cancer risks for 28 different types of cancer. It is found that the higher probability of the cancer to occur does not necessary lead to the fast times of starting the cancer. This suggests that both lifetime risks and cancer initiation times must be used to evaluate the possibility of appearance of the cancer tumor. The analogy of cancer initiation processes with chemical reactions is discussed. Our theoretical analysis helps to clarify the microscopic aspects of cancer initiation processes.
##### Chemistry
September 23, 2019
Kent 120 | Monday, 3:45 pm
## Macropolis: A Chicagoland Polymer Symposium
Join us for this celebration of soft matter science occurring in the greater Chicago area!
This inaugural polymer science symposium is planned as the first of many of its kind. The event, to be held at the University of Chicago this year, will be hosted at Northwestern University for the next symposium.
Plenary lectures will feature faculty, postdocs, and students from both universities. Registration is free but required for lunch. For the full schedule and to register, visit the event's microsite.
##### Special Event
September 20, 2019
ERC 161 | Friday, 9:00 am
## Claudia Felser, Max Planck Institute Chemical Phyics of Solids
#### Magnetic Weyl Semimetals
Topology a mathematical concept became recently a hot topic in condensed matter physics and materials science. One important criteria for the identification of the topological material is in the language of chemistry the inert pair effect of the s-electrons in heavy elements and the symmetry of the crystal structure [1]. Beside of Weyl and Dirac new fermions can be identified compounds via linear and quadratic 3-, 6- and 8- band crossings stabilized by space group symmetries [2]. In magnetic materials the Berry curvature and the classical AHE helps to identify interesting candidates. Magnetic Heusler compounds were already identified as Weyl semimetals such as Co2YZ [3,4], in Mn3Sn [5,6,7] and Co3Sn2S2 [8,9,10]. The Anomalous Hall angle helps to identify even materials in which a QAHE should be possible in thin films. Besides
this k-space Berry curvature, Heusler compounds with non-collinear magnetic structures also possess real-space topological states in the form of magnetic antiskyrmions, which have not yet been observed in other materials [11]. Host: Peter Littlewood, 2-9879 or via email at littlewood@uchicago.edu. Persons who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### Joint JFI & PME Seminar
September 12, 2019
ERC201 | Thursday, 3:00 pm
## Efi Efrati, Weizmann Institute of Science
#### Rotational diffusion of a molecular cat: Fractional statistics in the harmonic three-body problem
##### Computations in Science
September 11, 2019
KPTC 206 | Wednesday, 12:15 pm
## Closs Lecture: Professor Zahra Fakhraai: University of Pennsylvania
#### Understanding Glass Transition Through Interfacial Properties
##### Chemistry
September 9, 2019
Kent 120 | Monday, 3:45 pm
## Alexei Tkachenko, Center for Functional Nanomaterials, Brookhaven National Laboratory
#### New facets of Floppy Networks: from soft matter to hard (and back).
Floppy Networks (FNs) play a prominent role in soft condensed matter physics, from polymeric gels and rubber to biomolecules, glasses, and granular materials. FNs provide valuable insight into the origin of anomalous mechanical and thermal properties in these systems. In my talk, I will discuss how the very same concept of FN emerges in the context of a family of open-framework ionic solids, which can be conceptualized as Coulomb floppy networks. One remarkable example is ScF_3. This material exhibits a number of unusual properties, including quantum structural phase transition near ambient pressure and negative thermal expansion (NTE). Our microscopic theory traces these effects to the FN-like crystalline architecture, which is stabilized by the net electrostatic repulsion that plays the role similar to the osmotic pressure in a polymeric gel. NTE in this type of inorganic solids has essentially the same origin as in gels and rubber. Our theory provides an accurate quantitative description of NTE, compressibility, and structural phase diagram, all in excellent agreement with multiple experiments. Entropic stabilization of criticality explains the observed phase behavior, while significant entropic contribution to elasticity accounts for the marked discrepancy between the experimentally observed compressibility and its ab initio calculation.
Finally (as a bonus track) I will discuss our new results in another classical problem related to FNs: the configurational entropy of a Random Closed Packing of hard spheres.
##### JFI Special Seminar
September 4, 2019
GCIS E123 | Wednesday, 12:00 pm
## Liquid crystal elastomer gnocchi
12:00 eat. Don't eat the gnocchi
##### MRSEC Baglunch
August 29, 2019
GCIS E123 | Thursday, 1:00 pm
## Professor Dr. Kallol Ray, Humboldt-University Berlin
#### Small Molecule Activation At Transition Metal Centers: Structure-Function Correlations
##### Chemistry
August 28, 2019
| Wednesday, 1:15 pm
## James Sellers, PhD, NHLBI, NIH
#### Probing the motile & mechanical properties of nonmuscle myosin 2
##### Biophysical Dynamics
August 26, 2019
GCIS W301 | Monday, 12:00 pm
## Étienne Fodor, University of Cambridge
#### Active matter far from equilibrium: Work, dissipation and phase transitions
Active matter is a paradigm of soft materials made of a large number of interacting agents, ranging from colonies of bacteria to assemblies of biomimetic micro-swimmers, where individual self-propulsion leads to dynamics and structures without any equilibrium equivalent. The dissipation at the basis of activity offers the opportunity to design smart materials, for instance to extract work with unprecedented protocols, for which generic guiding principles are still lacking. Moreover, controlling dissipation allows one in principle to select which order emerges at large scale, by promoting phase transitions whose properties are yet to be studied.
First, I will present design strategies for active engines which exploit specifically nonequilibrium effects, such as the autonomous motion of asymmetric obstacles and the lack of an equation of state in active fluids. I will discuss how to optimize their efficiency in terms of the protocol details and, when possible, compare their performances with thermal engines. Second, I will examine the emergence of spontaneous order when changing dissipation. Using large deviation techniques, I will describe unexpected phase transitions, for instance towards a collective motion despite the lack of aligning interactions, and rationalize the microscopic mechanisms triggering such collective effects.
##### MRSEC Baglunch
August 23, 2019
GCIS E123 | Friday, 1:00 pm
## Patrick McCall, PhD, Max Planck Instof Molec Cell Biol & Genetics Dresden
#### Measuring protein phase equilibria in situ via quantitative phase microscopy
Many membrane-less compartments in eukaryotic cells are protein-rich biomolecular condensates formed via phase separation from the cyto- or nucleoplasm. Condensate physicochemical properties, such as protein concentration, mesh size, and viscoelasticity, emerge from the interactions of the constituent molecules, and are thought to be tuned over evolutionary time to facilitate the specific biological functions of the compartments. However, a predictive understanding of how condensate properties are encoded by the amino acid sequences of scaffold proteins, which contribute the bulk of the non-aqueous condensate mass, is currently lacking. Although existing polymer physics models have provided guidance, limitations of many conventional experimental methods to accurately measure the protein concentration in the condensed phase often restricts characterization of protein condensation equilibria to the measurement of the dilute phase. This limitation severely impairs quantitative assessment of competing physical models and thereby the elucidation of the relevant biophysical picture. To address this, we use quantitative phase microscopy and optical diffraction tomography to measure the 3D refractive index distribution of protein-rich droplets following in vitro phase separation, from which we calculate the protein concentration of the condensed branch of the two-phase coexistence curve. We focus on the phase equilibria of constructs derived from TAF15, the ancestral member of the well-studied FUS/EWSR1/TAF15 protein family, and find protein concentrations in the condensed phase to typically exceed 400 mg/ml over a wide range of temperatures and ionic strengths, greatly exceeding the concentrations we estimate from confocal fluorescence microscopy. Comparison of phase diagrams of different protein constructs sheds light on the link between protein sequence and phase equilibria in vitro, providing an essential reference for experiments and perturbations in vivo.
##### Biophysical Dynamics
August 22, 2019
GCIS W301 | Thursday, 9:00 am
## Development of a 100 GeV tabletop particle collider…
#### with sound
eat, 12:00
collider: 12:15
##### MRSEC Baglunch
August 16, 2019
GCIS E123 | Friday, 1:00 pm
## Some like it tense
#### or how proteins detect osmotic load
1:00 Special guest: US
1:15 Regular guest reveals Nature's Secret
##### MRSEC Baglunch
August 9, 2019
GCIS E123 | Friday, 1:00 pm
## transverse shocks in an odd viscosity medium
I try to show up with the speaker at noon so whoever is there can talk
At 12:15 our discussion of transverse shocks in an odd viscosity medium would start
##### MRSEC Baglunch
July 26, 2019
GCIS E123 | Friday, 12:00 pm
## Nancy Forde, Department of Physics, Simon Fraser University
#### Interrogating protein flexibility and stability at the single-molecule level
Collagen is the fundamental structural protein in vertebrates and is widely used as biomaterial, for example as a substrate for tissue engineering. In spite of its prevalence and mechanical importance in biology, the mechanics of its triple-helical structure are surprisingly controversial: its flexibility is unresolved, as is its response to stress. My research group has been investigating these properties through single-molecule experiments. To do so, we have developed imaging algorithms to use in atomic-force microscopy, described models for polymers with inherent curvature, and built a new instrument for high-throughput single-molecule force spectroscopy, the mini-radio centrifuge force microscope (MR.CFM). I’ll describe what we have learned about collagen’s flexibility and stress response, why these properties are important, and how our work resolves some of the many contentious findings regarding collagen’s mechanics. Of broader relevance, I will also highlight potential applications of this work to other biological systems.
##### Biophysical Dynamics
July 19, 2019
GCIS W301 | Friday, 2:00 pm
## Graham R. Fleming
#### 70th Birthday Symposium
Graham Fleming was born in Barrow, England on December 3,
1949. He received his B.S. with honors in Chemistry from the
University of Bristol in 1971 and his Ph.D. in physical chemistry
from University College London and the Royal Institution in
1974. Fleming held postdoctoral appointments at Caltech,
University of Melbourne, and the Royal Institution. In 1979,
Fleming joined the University of Chicago ultimately becoming the
Arthur Holly Compton Distinguished Service Professor in 1987.
At UChicago, Fleming served as Chair of the Chemistry
Department and helped found the Institute for Biophysical
Dynamics. In 1997, Fleming moved his research group to UC
Berkeley where he served as Professor of Chemistry and the
founding director of the Physical Biosciences Division at Lawrence
Berkeley National Laboratory, founding director of the California
Institute for Quantitative Biosciences (QB3), Deputy Laboratory
Director at LBNL, and Vice-Chancellor for Research.
Fleming’s research group develops and uses advanced
multidimensional ultrafast spectroscopic methods to study
complex condensed phase dynamics in systems ranging from
solvated small molecules to natural photosynthetic complexes as
well as nanoscale systems such as single-walled carbon nanotubes
and organic photovoltaics.
Program:
8:30 am Registration and Breakfast
9:00 am Welcome
9:10 am Lin Chen, ANL & Northwestern Univ.
9:55 am Tomas Mancal, Charles University in Prague
10:40 am Coffee
11:10 am Min Cho, Korea University
11:55 am Select Letters from Friends and Colleagues
12:00 pm Lunch (Atrium)
1:00 pm David Jonas, University of Colorado, Boulder
1:45 pm John Wright, University of Wisconsin, Madison
2:30 pm Coffee
3:00 pm Norbert Scherer, University of Chicago
3:45 pm Karl Freed, University of Chicago
4:15 pm Brent Kreuger, Hope College
6:00 pm Sepia (dinner by invitation)
123 North Jefferson St, Chicago
##### JFI Special Seminar
July 15, 2019
GCIS W301 | Monday, 8:30 am
## on leaves, flowers and seed slugs
#### geometry and mechanics
Meet to eat: 12:00
Stay to play: 12:15
##### MRSEC Baglunch
July 12, 2019
GCIS E123 | Friday, 12:00 pm
## Alfons van Blaaderen Soft Condensed Matter, Debye Institute for NanoMaterials Science, Utrecht University
#### Surprises in the Self-Assembly of Particles in Spherical Confinement
About 6 years ago our group started research at developing methodologies to structure matter at multiple length scales by self-assembly (SA). Presently, we see the induced SA of particles inside slowly drying droplets dispersed in an emulsion system and the resulting supraparticles (SPs) as a powerful generally applicable methodology of hierarchical SA. We found that making the shape of the particles the dominant factor in the SA is the most versatile way to use this route also for complex particle shapes and mixtures of particles. One of our first findings by both experiments and computer simulations was that spherical particles self-assembled inside a spherical confinement do not have their equilibrium bulk face centered cubic, close packed, crystal arrangement, but instead adopt an icosahedral symmetry. It turns out this icosahedral symmetry is the lowest free energy state up until roughly 100.000 particles [1]. Icosahedral packings are known not to be able to regularly pack in 3D space and are known e.g. for clusters of atoms interacting through a Lennard-Jones potential. However, it was not known that shape and thus entropy alone would favor this symmetry as well when it is induced by the spherical confinement. In recent work, we have extended our results to include the effects of particles shape (e.g. using rounded cube shaped particles) [2], rod-shaped particles [3], plate-shaped and binary particle systems. We will discuss how these changes affect the SA and how such SPs can be analyzed quantitatively on the single particle level in 3D by electron microscopy tomography [1-4]. We will also show our first more applied work on creating SPs with tunable light emission [5,7], for which the emission properties are modified by Mie Whispering Gallery Modes [6], and that are able to lase as well [7]. For a binary mixture of hard particles that form so-called MgZn2 Laves Phase crystals in bulk we find 3D icosahedral quasicrystals to be induced by the spherical confinement (unpublished work [8]) allowing us for the first time to determine on the single particle level in 3D the structure of a quasicrystal and with computer simulations study how these systems nucleate and grow.
##### JFI Special Seminar
July 3, 2019
KPTC 206 | Wednesday, 10:30 am
## Cristina Paulino, PhD, Department of Structural Biology & Enzymology Groningen Biomolecular Sciences & Biotechnology Institute (GBB) University of Groningen
#### Cryo-EM studies on membrane transporters reveal new mechanistic insights
##### Biophysical Dynamics
July 2, 2019
GCIS W301 | Tuesday, 12:00 pm
## Nanoparticle Templating of Ultra-thin and Highly Porous Polymer Membranes
12:00 eating time
12:15 Science time
##### MRSEC Baglunch
June 28, 2019
GCIS E123 | Friday, 12:00 pm
## Dr. Peter S. Burns, Department of Physics, University of Colorado-Boulder
#### Towards Quantum Transduction with an Improved Electro-Opto-Mechanical Converter
A quantum link between microwave and optical frequencies is a crucial element of future quantum networks. We have developed an efficient electro-optic converter by coupling a single vibrational mode of a SiN membrane to both a superconducting microwave resonator and a high-finesse optical cavity. This converter operates at T < 100 mK temperatures with 47% conversion efficiency. Discovering that vibrational noise produces correlations between microwave and optical outputs, we implement a classical feedforward protocol that improves the recovery of a weak, upconverted signal and reduces added noise by 59%, to 38 photons, for this high-efficiency device. Our results introduce an intriguing alternative method for handling errors introduced by thermal noise. The main contributions to this added noise are thermally driven mechanical motion, undesired interactions between the laser and the superconducting circuit, and microwave circuit parameter noise. In order to address these sources of noise, we have redesigned the optical cavity, introduced phononic shielding, and fabricated the superconducting circuit from NbTiN instead of Nb. With these design innovations we hope to reduce the added noise below the one photon threshold for quantum operations.
##### JFI Special Seminar
June 26, 2019
GCIS E223 | Wednesday, 11:00 am
## Supercritical Water
#### from universality to personality
Meet to eat: 12:00
Listen and discuss: 12:15
##### MRSEC Baglunch
June 21, 2019
GCIS E123 | Friday, 12:00 pm
## IBD Science@theInterface
#### Machine Learning in Biology
The 15th Annual IBD Science@theInterface is scheduled for this FRIDAY, JUNE 21st.
The symposium’s theme this year is “Machine Learning in Biology” and will be held in the Knapp Center for Biomedical Discovery, Room 1103, beginning at 10:30.
The speakers will cover a wealth of topics, with something for everyone, schedule below. The talks will followed by a reception for all symposium attendees.
Welcome, Michael Rust
Session 1, Benoit Roux, Moderator
10:30-11:15
Pratyush Tiwary, University of Maryland, College Park
Learning to learn: accurate, efficient sampling of (bio)molecular rare events
11:15-12:00
Reverse-engineering Stochastic Dynamics: Quasi-species Evolution, Complex Disease Processes and Beyond
12:00-1:00 lunch (will be provided)
Session 2, Mike Rust, Moderator
1:00-1:45
Aly Azeem Khan, Toyota Technological Institute at Chicago
New computational approaches to understand immune function
1:45-2:30
Christina Leslie, Sloan Kettering Institute
Decoding chromatin states in immune and cancer cells
2:30-3:00 break
Session 3, Arvind Murugan, Moderator
3:00-3:45
Mona Singh, Princeton University
Integrative approaches to discover cancer genes
3:45-4:3
Loïc Royer, Chan Zuckerberg Biohub
Pushing the Limits of Fluorescence Microscopy with adaptive imaging and machine learning
4:30 Reception
##### Biophysical Dynamics
June 21, 2019
KCBD 1103 | Friday, 10:30 am
## Matt Jaffe, University of California, Berkeley
#### Atom interferometry in an optical cavity
Matter wave interferometry has become a powerful tool for precision measurement and metrology. Optical resonators, meanwhile, are a ubiquitous tool for the coherent control of light. We have combined these two components to build the first atom interferometer inside of an optical cavity. I will present techniques and measurements enabled by and performed with this apparatus. The resonant power enhancement and mode-filtering of the cavity provide strong, smooth wavefronts for manipulating atoms. Very recently, this has led to record-breaking interferometer durations of up to 15 seconds using an optical lattice. It has also enabled a high-fidelity adiabatic passage technique which allows for coherent momentum transfer of up to hundreds of photons. We have used this cavity atom interferometer to explore three types of interactions with an in-vacuum source mass: (i) gravity, (ii) a novel force mediated by blackbody radiation, and (iii) "screened" forces arising from certain dark energy models. I will discuss each of these topics, as well as an outlook for future applications.
##### JFI Special Seminar
June 17, 2019
GCIS E223 | Monday, 3:30 pm
## Thomas Chalopin, Collège de France
#### Light-spin interactions in atomic dysprosium: non-classical spin states and synthetic dimensions
The combination of a large spin J = 8 and narrow optical transitions makes bosonic dysprosium an ideal platform for engineering strong light-spin interactions. In our experiments, we use off-resonant laser beams close to the intercombination line at 626 nm to induce non-linear spin coupling in the electronic ground state of dysprosium.
In the first part of this talk, I will describe the implementation of the celebrated one-axis twisting Hamiltonian [Kitagawa et. al., PRA 47 5138 (1993)]. We experimentally realize a superposition of coherent spin-states with opposite magnetizations, that we call a 'kitten' state. We show that this highly sensitive state can be used in the context of quantum metrology, and we experimentally measure an enhanced sensitivity to external magnetic field by a factor 13.9(1.1), close to the Heisenberg limit G = 2J = 16. We also show that the combination of single magnetic sublevel resolution and arbitrary spin rotations enables us to measure the optimal sensitivity of non-gaussian (oversqueezed) states, well above the capability of squeezed states, and more robust to environmental noise than superposition states.
In the second part of the talk, I will discuss the realization of synthetic Landau levels using dysprosium atoms. A synthetic spatial dimension is encoded in the large spin of dysprosium, and additional spin-orbit coupling yields to the emergence of an artificial gauge field. In an analogy with a charged particle in an external magnetic field, the low-energy spectrum of our system exhibits the same characteristics as Landau levels. Although our experimental results are still preliminary, we are able to probe the main features of the Lowest Landau level: propagating edge modes, closed cyclotron orbits and the emergence of an anomalous velocity.
##### JFI Special Seminar
June 17, 2019
GCIS E223 | Monday, 1:15 pm
## Niklas Mueller, Brookhaven National Laboratory
#### Constructing phase space distributions with internal symmetries
We discuss an ab initio world-line approach to constructing phase space distributions in systems with internal symmetries. Starting from the Schwinger-Keldysh real time path integral in quantum field theory, we derive the most general extension of the Wigner phase space distribution to include color and spin degrees of freedom in terms of dynamical Grassmann variables. The corresponding Liouville distribution for colored particles, which obey Wong's equation, has only singlet and octet components, while higher moments are fully constrained by the Grassmann algebra. The extension of phase space dynamics to spin is represented by a generalization of the Pauli-Lubanski vector; its time evolution via the Bargmann-Michel-Telegdi equation also follows from the phase space trajectories of the underlying Grassmann coordinates. Our results for the Liouville phase space distribution in systems with both spin and color are of interest in fields as diverse as chiral fluids, finite temperature field theory and polarized parton distribution functions. We also comment on the role of the chiral anomaly in the phase space dynamics of spinning particles. Our formulation may be extended to a generating functional for hydrodynamics with internal symmetries, relevant for chiral fluids in QCD and beyond.
June 10, 2019
PRC 201 | Monday, 1:30 pm
## Aishwarya Kumar, Penn State University
#### Neutral atom quantum computing: Quantum gates and Maxwell's demon
Atoms trapped in optical lattices are promising qubit candidates for quantum computers. I will describe the control that we have developed over the internal and motional states, as well as the positions of Cesium atoms trapped in a 3D optical lattice. We can execute arbitrary, site-selective single qubit gates with high fidelity (0.996) and low crosstalk (0.002). Initially, only a random half of the lattice sites are occupied with a single atom due to pairwise light assisted collisions. After cooling to the 3D vibrational ground state of the trap, most of the entropy is associated with this random occupation of the lattice. I will show how we move single atoms to generate fully filled sub-lattices, significantly lowering the entropy and creating a desirable starting point for a quantum computation. This “sorting” process is also an implementation of a Maxwell’s demon. I will also outline the path to implementing high fidelity entangling gates in this system and realize a 50 qubit quantum computer in the near future.
##### JFI Special Seminar
June 10, 2019
GCIS E223 | Monday, 11:00 am
## Critical exceptional point:
#### From Bose-Einstein condensate to active matter
Eat and kibitz: 12:00
Listen and kibitz: 12:15
##### MRSEC Baglunch
June 7, 2019
GCIS E123 | Friday, 12:00 pm
## David Saltzberg, University of California Los Angeles
#### How did Amy and Sheldon win their Nobel Prize?
Since 2006, I worked with the writers and other crew of the television situation comedy, The Big Bang Theory which just aired its season finale. I will talk about my experiences putting my University of Chicago physics PhD to work helping the writers and others tell this story as their "science consultant." Along the way, I've learned that comedy is an empirical subject. I'll share a few of the other things I learned about working with creative and dedicated people in an industry seemingly far from my own.
##### Physics Colloquium
June 6, 2019
KPTC 106 | Thursday, 3:30 pm
###### Thu 6
The susceptibility of quantum information to decoherence makes error correction an important area of research. However, the majority of quantum error correction protocols are accompanied by a significant hardware and software overhead. One way to mitigate the overhead is by hardware-efficient encoding and autonomous error correction. For superconducting quantum circuits, this goal can be achieved by storing information in high-Q harmonic oscillators, using Schrödinger cat-states. This encoding requires a highly nonlinear, six-quanta process for autonomously stabilizing the manifold of quantum information. I will present theory and experimental results on obtaining the eight-wave mixing nonlinearity using Raman-assisted cascading of four-wave mixing processes. I will also present a circuit design for cancelling unwanted Hamiltonian terms, like cross-Kerr interactions, which introduce uncorrected errors in our code space. We believe this combination of Hamiltonian engineering and hardware design will result in a completely error protected logical qubit.
##### JFI Special Seminar
June 6, 2019
GCIS E223 | Thursday, 1:30 pm
## IME Distinguished Colloquium Series - Ralph Colby
Professor Ralph Colby from Penn State University will speak as part of the IME Distinguished Colloquium Series.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
June 5, 2019
KCBD 1103 | Wednesday, 4:00 pm
## Atac Imamoglu, ETH Zurich
#### Many-body Optical Excitations in Solid-State Systems
Two dimensional materials provide new avenues for synthesizing compound quantum systems. Monolayers
with vastly different electric, magnetic or optical properties can be combined in van der Waals
heterostructures which ensure the emergence of new functionalities; arguably, the most spectacular example
to date is the observation of strong correlations and low electron density superconductivity in Moire
superlattices obtained by stacking two monolayers with a finite twist angle. Optically active monolayers such
as molybdenum diselenide provide a different "twist" as they allow for investigation of nonequilibrium
dynamics in van der Waals heterostructures by means of femtosecond pump-probe measurements. Moreover,
interactions between electrons and the elementary optical excitations such as excitons or polaritons, provide
an ideal platform for investigation of quantum impurity physics, with possibilities to probe both Fermi- and
Bose-polaron physics as well as mixtures with tunable density of degenerate fermions and bosons.
After introducing the framework we use to describe many-body optical excitations in van der Waals
heterostructures, I will describe two recent developments in the field. The first experiment uses pump-probe
measurements to demonstrate how exciton-electron interactions beyond the non-self-consistent T-matrix
approximation lead to optical gain by stimulated cooling of exciton-polaron-polaritons. The second experiment shows that a tri-layer system, consisting of two semiconducting monolayers separated by an insulating layer, could lead to hybridization of intra- and inter-layer excitons. The latter has potentialapplications ranging from strongly interacting polaritons to reaching Feshbach resonance condition in exciton-electron scattering.Host: Jonathan Simon, 2-9661 or via email at simonjon@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The 1st Tuesday JFI Colloquium
June 4, 2019
GCIS W301 | Tuesday, 4:00 pm
## Carlos Bustamante: University of California,Berkeley
#### Division of Labor Among the Subunits of a Highly Coordinated Ring ATPase
Many transport processes in the cell are performed by a diverse but structurally and functionally related family of
proteins. These proteins, which belong to the ASCE (Additional Strand, Conserved E) superfamily of ATPases, often form
mutimeric rings. Despite their importance, a number of fundamental questions remain as to the coordination of the
various subunits in these rings. Bacteriophage phi29 packages its 6.6 mm long double-stranded DNA using a pentameric
ring nano motor This portal motor is ideal to investigate these questions and is a remarkable machine that must
overcome entropic, electrostatic, and DNA bending energies to package its genome to near-crystalline density inside the
capsid. Using optical tweezers, we find that this motor can work against loads of up to ~55 picoNewtons on average,
making it one of the strongest molecular motors ever reported. We establish the force-velocity relationship of the
motor. Interestingly, the packaging rate decreases as the prohead fills, indicating that an internal pressure builds up due
to DNA compression attaining the value of ~3 MegaPascals at the end of packaging. This pressure, we show, is used as
part of the mechanism of DNA injection in the next infection cycle. We have used high-resolution optical tweezers to
characterize the steps and intersubunit coordination of the pentameric ring ATPase responsible for DNA packaging in
bacteriophage Phi29. By using non-hydrolyzable ATP analogs and stabilizers of the ADP bound to the motor, we establish
where DNA binding, hydrolysis, and phosphate and ADP release occur relative to translocation. Surprisingly, a division
of labor exists among the subunits: while only 4 of the subunits translocate DNA, all 5 bind and hydrolyze ATP,
suggesting that the fifth subunit fulfills a regulatory function. Furthermore, we show that the motor not only can
generate force but also torque. We characterize the role played by the special subunit in this process and identify the
symmetry-breaking mechanism in the motor. Finally, we have begun to investigate the physical basis of the inter-
subunit communication that results in this almost “clockwork” coordination. Mutants of the crucial arginine finger
residue permit us to dissect the network of interactions involved in this coordination.
##### Harkins Lecture
June 4, 2019
Kent 120 | Tuesday, 1:45 pm
## Carlos Bustamante: University of California,Berkeley
#### The Ribosome Modulates Nascent Protein Folding and Nascent Protein Folding can Modulate the Ribosome ActivityThe Ribosome Mandates Nascent Protein Folding and Nascent
Proteins are synthesized by the ribosome and generally must fold to become functionally active. Although it is commonly assumed that the ribosome affects the folding process, this idea has been extremely difficult to demonstrate. We optical tweezers to investigate the folding of single ribosome-bound stalled nascent polypeptides of T4 lysozyme synthesized in a reconstituted in vitro translation system. Significantly, we find that the ribosome slows the formation of stable tertiary interactions and the attainment of the native state relative to the free protein. Incomplete T4 lysozyme polypeptides misfold and aggregate when free in solution, but they remain folding-competent near the ribosomal surface. These results suggest that the ribosome not only decodes the genetic information and synthesizes polypeptides, but also promotes efficient de novo attainment of the native state. On the other hand, interactions between the nascent polypeptide and the ribosome exit tunnel represent one mode of regulating synthesis rates. The SecM protein arrests its own translation, and release of arrest at the translocon has been proposed to occur by mechanical force. Using optical tweezers, we demonstrate that arrest of SecM-stalled ribosomes can indeed be rescued by force alone and that the force needed to release stalling can be generated in vivo by a nascent chain folding near the ribosome tunnel exit. We formulate a kinetic model describing how a protein can regulate its own synthesis by the force generated during folding, tuning ribosome activity to structure acquisition by a nascent polypeptide.
##### Harkins Lecture
June 3, 2019
Kent 120 | Monday, 1:45 pm
## Amos Yaron, Technion
#### Probing anomalous driving
I will describe two novel effects that may be observed once one drives a system whose underlying matter content generate an ’t Hooft anomaly. The effects are tied to the existence of quasi-normal modes of magnetically charged black branes at low temperatures and to features of Chern-Simons Maxwell dynamics in an asymptotically AdS geometry.
June 3, 2019
PRC 201 | Monday, 1:30 pm
#### Universality and individuality in neural dynamics across large populations of recurrent networks
Currently neuroscience is undergoing a data revolution, where many thousands of neurons can be measured at once. These new data are extremely complex and will require a major conceptual advance in order to infer the underlying brain computations from them. In order to handle this complexity, systems neuroscientists have begun training deep networks, in particular recurrent neural networks (RNNs), in order to make sense of these newly collected, high-dimensional data. These RNN models are often assessed by quantitatively comparing neural dynamics of the model with the brain. However, the nature of the detailed neurobiological inferences one can draw from such comparisons remains elusive. For example, to what extent does training RNNs to solve simple tasks, prevalent in neuroscientific studies, uniquely determine the low-dimensional dynamics independent of neural architectures? Or alternatively, are the learned dynamics highly sensitive to different neural architectures? Knowing the answer to these questions has strong implications on whether and how to use task-based RNN modeling to understand brain dynamics. To address these foundational questions, we study populations of thousands of RNN architectures commonly used to solve neuroscientifically motivated tasks and characterize their dynamics. We find the geometry of the dynamics can be highly sensitive to different network architectures. Moreover, we find that while the geometry of neural dynamics can vary greatly across architectures, the underlying computational scaffold: the topological structure of fixed points, transitions between them, limit cycles, and aspects of the linearized dynamics, often appears universal across all architectures. Overall, this analysis of universality and individuality across large populations of RNNs provides a much needed foundation for interpreting quantitative measures of dynamical similarity between RNN and brain dynamics.
##### Physics Colloquium
May 30, 2019
KPTC 106 | Thursday, 3:30 pm
## Xiaoming Mao, University of Michigan
#### Topological floppy modes in aperiodic networks and a mechanical duality theorem
Topological states of matter have been intensively studied in crystals, leading to fascinating phenomena such as scattering-free edge current in topological insulators. However, the power of topological protection goes well beyond ordered crystal lattices. In this talk we explore how topology protects mechanical edge modes in messy, noncrystalline, systems. We will use disordered fiber networks and quasicrystals as our examples, to demonstrate how topological edge floppy modes can be induced in these structures by controlling their geometry. Fiber networks are ubiquitous in nature and especially important in bio-related materials. Establishing topological mechanics in fiber networks may shed light on understanding robust processes in mechanobiology. Quasicrystals show unusual orientational order with quasiperiodic translational order. We found that a bulk topological polarization can be defined for mechanics of quasicrystals that is unique to their non-crystallographic orientational symmetry. References: (1) Di Zhou, Leyou Zhang, Xiaoming Mao, “Topological Edge Floppy Modes in Disordered Fiber Networks”, Phys. Rev. Lett. 120, 068003 (2018); (2) Di Zhou, Leyou Zhang, Xiaoming Mao, “Topological Boundary Floppy Modes in Quasicrystals”, arXiv:1809.09188 (2018).
##### Computations in Science
May 29, 2019
KPTC 206 | Wednesday, 12:15 pm
## Josh Vura-Weis, Department of Chemistry - UIUC
#### What Did the Metal Know, and When Did She Know It? Ultrafast XUV Spectroscopy Reveals Short-lived States in Transition Metal Complexes and Organohalide Perovskites
X-ray absorption near edge spectroscopy (XANES or NEXAFS) is a powerful technique for electronic structure determination. However, widespread use of XANES is limited by the need for synchrotron light sources with tunable x-ray energy. Recent developments in extreme ultraviolet (XUV) light sources using the laser-based technique of high-harmonic generation have enabled core-level spectroscopy to be performed on femtosecond to attosecond timescales. We have extended the scope of tabletop XUV spectroscopy and demonstrated that M2,3-edge XANES, corresponding to 3p→3d transitions, can reliably measure the electronic structure of first-row transition metal coordination complexes with femtosecond time resolution. We use this ability to track the excited-state relaxation pathways of photocatalysts and spin crossover complexes. In semiconductors such as CH3NH3PbI3, distinct signals are observed for photoinduced electrons and holes, allowing the dynamics of each carrier to be tracked independently. This work establishes extreme ultraviolet spectroscopy as a useful tool for mainstream research in inorganic, organometallic, and materials chemistry.Host: Andrei Tokmakoff, 4-7696 or via email to tokmakoff@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
May 28, 2019
GCIS W301 | Tuesday, 4:00 pm
## Congjun Wu (UCSD)
#### Symmetry and Correlation Aspects of Quantum Dynamics
Symmetry and correlation are fundamental aspects of condensed matter physics. A solid state textbook typically starts with crystalline symmetries as classified by space group, and proceeds with the Bloch theorem which sets up the framework of electron’s quantum behavior under crystalline symmetries. We have generalized these concepts to dynamic systems by proposing “dynamic crystal” and updating the Bloch theorem. A new structure of “space-time group” is constructed for describing dynamic symmetries, including the space-time intertwined symmetries of “time-screw-rotation” and “time-glide-reflection”. Dynamic crystal applies to a large class of systems including laser-driven solid state crystals, dynamic photonic crystals and optical lattices. On the other hand, the real frequency responses at high energies is a hardcore problem of strong correlation physics. Our new progress is to employ integrable methods to investigate spin dynamics arising from the Bethe string states, which are exotic many-body excitations of high energy magnon anti-bound states. In particular, the 3-string excitations, i.e., the 3-body anti-bound states, are identified for the first time by comparing the characteristic spectra lines in the electron-spin-resonance spectroscopy measurement on SrCo2V2O8 with the theory calculations.
##### JFI Special Seminar
May 28, 2019
E223 | Tuesday, 10:00 am
## Teri W. Odom: Northwestern University
#### Plasmon-molecule Interactions in Confined Volumes
##### Chemistry
May 24, 2019
Kent 120 | Friday, 1:45 pm
## Elizabeth Simmons, University of California San Diego
#### Gender Equity , Power Structures, and Implicit Bias in Stem Elizabeth Simmons, University of San Diego
This presentation will start by reviewing data of the current status of gender equity in STEM disciplines and summarizing social science research that illuminates some causes of gender disparities in STEM. With this context established, the focus will shift to how women enter into leadership roles in academic settings, what they experience, and how gender impacts the way they exercise their authority. The final part of the talk will discuss how we can all contribute to changing the face of leadership for the future, to the benefit of all of us in STEM
##### Physics Colloquium
May 23, 2019
KPTC 106 | Thursday, 3:30 pm
## IME Distinguished Colloquium Series - Sven Rogge
Professor Sven Rogge from the University of New South Wales will speak as part of the IME Distinguished Colloquium Series.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
May 22, 2019
KCBD 1103 | Wednesday, 4:00 pm
## Joshua Shaevitz, Princeton University
#### Self-driven phase transitions in living matter
The soil dwelling bacterium Myxococcus xanthus is an amazing organism that uses collective motility to hunt in giant packs when near prey and to form beautiful and protective macroscopic structures comprising millions of cells when food is scarce. I will present an overview of how these cells move and how they regulate that motion to produce different phases of collective behavior. Inspired by recent work on active matter and the physics liquid crystals, I will discuss experiments that reveal how these cells generate nematic order, how defect structure can dictate global behavior, and how Myxo actively tune the Péclet number of the population to drive a phase transition from a gas-like flocking state to an aggregated liquid-droplet state during starvation.
##### Computations in Science
May 22, 2019
KPTC 206 | Wednesday, 12:15 pm
## Gabriela S. Schlau-Cohen, The Department of Chemistry, MIT
#### Action at the Nanoscale: Single-molecule Studies of Protein Motion
Biological systems exhibit sophisticated responses to environmental and chemical perturbations, often involving conformational motions of their protein building blocks. These motions have been difficult to resolve due to limitations in sensitivity, specificity, and time resolution. We present advances in the analysis of single-molecule data that overcomes these limitations, resolving multiple, microsecond dynamics occurring in parallel within individual proteins. Using single-molecule methods, we explore two processes: (1) photoprotective quenching in oxygenic photosynthesis, gaining a mechanistic understanding of how photosynthetic systems respond to sunny conditions; and (2) the molecular-level motions of the target of cancer drugs, identifying previously hidden connections between the extracellular and intracellular domains of this important protein. Host: Sara Massey, chamberlinsc@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
May 21, 2019
GCIS W301 | Tuesday, 4:00 pm
## Greg Verdine: Harvard University
#### Pages from the Playbook of Nature
##### Chemistry
May 20, 2019
Kent 120 | Monday, 3:45 pm
## Alexios Pilychronakos
#### Generalized Calogero Models and their Hydrodynamics
Calogero-like models and their continuous descriptions appear in various physical systems and have a rich mathematical structure. Some time ago Abanov, Wiegmann and Bettelheim obtained a "dual" formulation of these models that make their soliton excitations manifest. I will use a first-order formulation of Calogero-like models in terms of a generating function to naturally generate their dual form and identify solitons as particles of negative mass. Using this formulation the dual form of Calogero particles in external quartic, trigonometric and hyperbolic potentials is obtained, which were known to be integrable but had no known dual formulation. Their fluid mechanics is also obtained using an intuitive "sawdust" approach. The nontrivial case of elliptic potentials will also be discussed.
May 20, 2019
PRC 201 | Monday, 1:30 pm
## Matthew B. Francis, University of California, Berkeley
#### Versatile Oxidative Coupling Reactions for Site-Selective Protein Modification
##### Chemistry
May 17, 2019
Kent 120 | Friday, 1:45 pm
## Ania Bleszynski Jayich, University of California Santa Barbara
#### TBA
##### Physics Colloquium
May 16, 2019
KPTC 106 | Thursday, 3:30 pm
## Anne McNeil: University of Michigan
#### Precision Conjugated Polymer Synthesis & Applications
##### Chemistry
May 16, 2019
GCIS W301 | Thursday, 1:15 pm
## Martin Falk
#### Simple models for (mostly) biological heterpolymers
Over the past two decades, there have been dramatic developments in our ability to functionalize submicron scale objects with molecules enabling specific interactions between building blocks. However, the range of structures that we can create still pales in comparison to the impressive complexity of structures formed from biopolymers. We would ideally like to understand if there are design principles that can be learned from biology, and adopted in order to design complex structures from simpler heteropolymers. We explore this possibility in the context of chromatin (the term applied to DNA and its associated proteins) and in the context of collagen, and conclude with a discussion of ongoing simulation and experimental work on the folding of 7-particle colloidal clusters.
##### MRSEC Baglunch
May 16, 2019
GCIS E123 | Thursday, 12:00 pm
## David Lentik, Stanford
#### Avian Inspired Design
Many organisms fly in order to survive and reproduce. My lab focusses on understanding bird flight to improve flying robots—because birds fly further, longer, and more reliable in complex visual and wind environments. I use this multidisciplinary lens that integrates biomechanics, aerodynamics, and robotics to advance our understanding of the evolution of flight more generally across birds, bats, insects, and autorotating seeds. The development of flying organisms as an individual and their evolution as a species are shaped by the physical interaction between organism and surrounding air. The organism’s architecture is tuned for propelling itself and controlling its motion. Flying animals and plants maximize performance by generating and manipulating vortices. These vortices are created close to the body as it is driven by the action of muscles or gravity, then are ‘shed’ to form a wake (a trackway left behind in the fluid). I study how the organism’s architecture is tuned to utilize these and other aeromechanical principles to compare the function of bird wings to that of bat, insect, and maple seed wings. The experimental approaches range from making robotic models to training birds to fly in a custom-designed wind tunnel as well as in visual flight arena’s—and inventing methods to 3D scan birds and measure the aerodynamic force they generate—nonintrusively—with a novel aerodynamic force platform. The studies reveal that animals and plants have converged upon the same solution for generating high lift: A strong vortex that runs parallel to the leading edge of the wing, which it sucks upward. Why this vortex remains stably attached to flapping animal and spinning plant wings is elucidated and linked to kinematics and wing morphology. While wing morphology is quite rigid in insects and maple seeds, it is extremely fluid in birds. I will show how such ‘wing morphing’ significantly expands the performance envelope of birds during flight, and will dissect the mechanisms that enable birds to morph better than any aircraft can. Finally, I will show how these findings have inspired my students to design new flapping and morphing aerial robots.
##### Computations in Science
May 15, 2019
KPTC 206 | Wednesday, 12:15 pm
## Dr. Logan Clark & Dr. Rachel G. Farber, James Franck Institute, University of Chicago
#### Building Quantum Materials Out of Light & Atomic-Scale Growth Mechanism of Niobium Hydrides on Hydrogen Infused Nb(100)
L. Clark - TITLE & ABSTRACT: “Building Quantum Materials Out of Light” -
Can quantum materials be built out of light? Ordinary photons, which freely propagate at the speed of light and don’t interact with each other at all, certainly will not form ordered materials. However, we have used a gas of ultracold atoms in an optical cavity to mediate strong collisions between photons, thus creating conditions suitable to highly ordered states of light. In this system, we have recently observed photon pairs forming topologically-ordered Laughlin states, commencing our exploration into quantum materials made from light. R.G. FARBER TITLE & ABSTRACT: “Atomic-Scale Growth Mechanism of Niobium Hydrides on Hydrogen Infused Nb(100)” -
Niobium (Nb) is the current standard for superconducting radio frequency (SRF) accelerator cavities due to its ultra-low surface resistance (Rs) and high cavity quality factor (Q) at operating temperatures of ~ 2 K. It is known that SRF cavity surface composition and contaminant incorporation is directly related to Q; hydrogen incorporation, which results in the formation of Nb hydrides, has been identified as a major source of decreased Q. There is not, however, a fundamental understanding of the growth mechanism for Nb hydrides. We have investigated Nb(100) samples infused with hydrogen using low-temperature scanning tunneling microscopy (LT-STM) to elucidate the atomic-scale growth mechanism of Nb hydrides. In addition, results from Fermi National Accelerator Laboratory have revealed the beneficial effects of nitrogen doping on SRF cavity performance. To understand the effects of nitrogen doping on Nb hydride growth, ongoing studies are focused on elucidating hydride growth behavior on Nb(100) samples infused with both hydrogen and nitrogen.
##### JFI Special Joint Postdoc Seminar
May 14, 2019
GCIS W301 | Tuesday, 4:00 pm
## Michael Green: University of California, Irvine
#### Insights into biological C-H bond activatiion
##### Chemistry
May 13, 2019
Kent 120 | Monday, 3:45 pm
## Luis Bettencourt, University of Chicago
#### TBA
##### Physics Colloquium
May 9, 2019
KPTC 106 | Thursday, 3:30 pm
## IME Distinguished Colloquium Series - Darrell Irvine
Professor Darrell Irvine from Massachusetts Institute of Technology will speak as part of the IME Distinguished Colloquium Series.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
May 8, 2019
KCBD 1103 | Wednesday, 4:00 pm
## Thierry Emonet, Yale University
#### Conflicts and synergies between individuality and collective behavior
Cells live in communities where they interact with each other and their environment. By coordinating individuals, such interactions often result in collective behavior that emerge on scales larger than the individuals that are beneficial to the population. At the same time, populations of individuals, even isogenic ones, display phenotypic heterogeneity, which diversifies individual behavior and enhances the resilience of the population in unexpected situations. This raises a dilemma: although individuality provides advantages, it also tends to reduce coordination. I will report on our recent experimental and theoretical efforts that use bacterial chemotaxis as model system to understand, the origin of individual cellular behavior and performance, and how populations of cells reconciliate individuality with group behavior.
##### Computations in Science
May 8, 2019
KPTC 206 | Wednesday, 12:15 pm
## Zohar Komargodski, Weizmann
#### Dynamics of Quantum Field Theory in 2+1 Dimensions with Chern-Simons Interactions
May 7, 2019
PRC 201 | Tuesday, 2:00 pm
## Bruce Berne, Columbia University
#### Molecular Dynamics: a Personal Retrospective
##### Rice-Berry Lecture
May 6, 2019
Kent 120 | Monday, 3:45 pm
## Cristiano Ciuti, Université de Paris, MPQ, CNRS, France
#### Quantum Cavities: From Vacuum Manipulation to Photon Simulation of Quantum Materials
In this talk, I will discuss two emerging frontier topics concerning quantum optical cavities. In the first part, I will show how the vacuum field of an electromagnetic resonator can dramatically control the dc magnetotransport of a 2D electron gas without illumination [1,2]. In the second part, I will present recent theoretical results via the corner-space renormalization [3] in finite-size systems revealing how 1D and 2D lattices of quadratically-driven electromagnetic resonators can simulate magnetic phase transitions in the quantum critical regime [4].
##### JFI Special Seminar
May 6, 2019
KPTC 206 | Monday, 2:00 pm
## Gregory Fu, CALTECH
#### Photoinduced, Copper-Catalyzed Substitution Reactions of Alkyl Electrophiles
##### Kharasch Lecture
May 3, 2019
Kent 120 | Friday, 1:45 pm
## Malleable matter: Designing disordered metamaterials by natural aging
Bring good cheer and merriment: 12:00
Bring brains : 12:15
##### MRSEC Baglunch
May 3, 2019
GCIS E123 | Friday, 12:00 pm
## FORUM 2019
#### Facilities Open-house Research Users Meeting
FORUM 2019
Facilities Open-house Research Users Meeting
Are innovation and resourcefulness part of your company's mission and philosophy?
Please join us for our first UChicago FORUM event focused on getting to know students, public access instrumentation facilities, and other regional resources.
What is the FORUM?
The FORUM is one of several ways for industry to see how resources, research, and talent at the University of Chicago aligns with their innovation needs.
Many companies are unaware of the opportunities available on campus. These opportunities include a variety of ways to get your foot in the door to test the waters. These opportunities include
Senior design projects in materials chemistry and engineering,
Advanced instrumentation and training available at hourly rates,
Project and internship based talent recruitment, as well as
Discovery of how faculty research topics are aligned with your innovation efforts.
Other avenues include networking with translational technology experts at the Polsky Center for Innovation and Entrepreneurship and other groups on or associated with the campus.
Register Now!
Who is this meeting for?
Corporate decision makers, Industrial/corporate scientists and engineers involved with:
Innovation Design & Implementation
Chemical Engineering
Process Development
Materials Science & Engineering
Failure Analysis
Materials Characterization
Also - Targeted talent recruitment of undergraduates and graduate students through internships, senior design projects, and consulting opportunities.
Tentative itinerary -
8:15 - 9:00 am Registration / Breakfast & Coffee
9:00 - 9:15 am Opening Remarks
9:15 - 10:30 am Project snapshots
10:30 - 11:00 am BREAK
11:00 - 11:45 am Keynote talk - Dr. Maria Kokkori (The Art Institute of Chicago)
11:45 - 1:00 pm Networking LUNCH
1:00 - 2:00 pm Poster session
2:00 - 3:00 pm Breakout sessions
3:00 - 4:00 pm. Facility Tours (limited space! - Sign up early)
##### MRSEC Special Event
May 3, 2019
ERC 161 | Friday, 8:15 am
## Phil Morrison, University of Texas, Austin
#### Joint CAM Colloquium
Physical models that describe the dynamics of matter, whether they be discrete, like those for interacting particles or dust, or continuum models, like those for fluids and plasmas, possess structure. Structure may manifest by sets of conservation laws resulting from Galilean or Poincare invariance, or by the property of entropy production giving relaxation to thermal equilibrium. Ultimately, structure arises from an underlying Hamiltonian form that may or may not be maintained in approximations and/or reductions of various kinds.
I will survey the Hamiltonian structure possessed by a variety of models, with an emphasis on a general magnetofluid model and Vlasov-Maxwell theory. In addition I will discuss structure preservation in numerical implementation. Although symplectic integration has been well studied and widely used for _x000C_finite-dimensional systems, the preservation of the structure that occurs in continuum models such as extended magnetohydrodynamics with generalized helicities, is considerably more difficult to implement. Progress in developing a discrete version of the Maxwell-Vlasov system that preserves its Hamiltonian structure, and its numerical implementation will be discussed.
##### Computations in Science
May 2, 2019
Eckart Hall 202 | Thursday, 4:00 pm
## Kawtar Hafidi, Argonne National Laboratory
#### Next Generation Nuclear Experiments: Toward 3D Imaging of Nuclei Kawtar Hafidi, Argonne National Laboratory
Inclusive deep inelastic scattering experiments have been instrumental in advancing our understanding of the Quantum Chromodynamics (QCD) structure of nuclei and the effect of nuclear matter on the structure of bound hadrons. A great example is the observation by the European Muon Collaboration (EMC) of a deviation of the deep inelastic structure function of a nucleus from the sum of the structure functions of the free nucleons, the so-called EMC effect. On the theory side, despite decades of theoretical efforts with increased sophistication, a unifying physical picture of the origin of the EMC effect is still a matter of intense debate. To reach the next level of our understanding of nuclear QCD and unravel the partonic structure of nuclei, experiments need to go beyond the inclusive measurements and focus on exclusive and semi-inclusive reactions. In this talk, results of the first exclusive measurement of deeply virtual Compton scattering off He-4 will be presented. Future measurements at Jefferson Lab 12 GeV using a new Low Energy Recoil Tracker will be discussed. We will conclude by introducing the importance of an Electron Ion Collider with high polarized luminosity and variable energy with comprehensive recoil detection in probing the gluonic and sea quark landscape of nuclei.
##### Physics Colloquium
May 2, 2019
KPTC 106 | Thursday, 3:30 pm
## Rafael Jaramillo, The Department of Materials Science, MIT
#### Mechanism and New Applications of Large and Persistent Photoconductivity
ABSTRACT: Abstract: Large and persistent photoconductivity (LPPC) in semiconductors is due to the trapping of photo-generated minority carriers at crystal defects. Theory suggests that anion vacancies in II-VI semiconductors are responsible for LPPC due to negative-U behavior, whereby two minority carriers become kinetically trapped by lattice relaxation following photo-excitation [1-2]. By performing a detailed analysis of photoconductivity in CdS, we provide experimental support for this negative-U model of LPPC [3]. We also show that LPPC is correlated with sulfur deficiency. We use this understanding to vary the photoconductivity of CdS films over nine orders of magnitude, and vary the LPPC characteristic decay time from seconds to 10,000 seconds, by controlling the activities of Cd2+ and S2- ions during chemical bath deposition. We suggest a screening method to identify other materials with long-lived, non-equilibrium, photo-excited states based on the results of ground-state calculations of atomic rearrangements following defect redox reactions, with a conceptual connection to polarons and organic dyes.
We apply our knowledge of defect physics in CdS to propose and design a new type of semiconductor device – the donor level switch (DLS), which operates by switching individual defects between deep-donor and shallow-donor states. We study DLS behavior by making two-terminal devices using hole injection layers to control the charge state of sulfur vacancies. We also apply our knowledge to study the influence of LPPC on the performance of CIGS thin-film solar cells.
If time allows we will also cover recent results from our group on infrared optical properties and phase-change functionality in transition metal di-chalcogenides (TMDs), and early results on growth and the opto-electronic performance of sulfide perovskite semiconductors.
[1] S. B. Zhang, S.-H. Wei & A. Zunger, Phys. Rev. B 63, 075205 (2001).
[2] S. Lany & A. Zuner, Phys. Rev. B 72, 035215 (2005).
[3] H. Yin, A. Akey & R. Jaramillo, Phys. Rev. Mater. 2, 084602 (2018).
##### Joint JFI & IME Seminar
May 2, 2019
GCIS 500A | Thursday, 2:00 pm
#### Viscoelastic response of quantum Hall states
One hallmark of topological phases with broken time reversal symmetry is the appearance of quantized non-dissipative transport coefficients, the archetypical example being the quantized Hall conductivity in quantum Hall states. Here I will talk about a new non-dissipative transport coefficients that appear in such systems - the Hall viscosity. In the first part of the talk, I will start by reviewing previous results concerning the Hall viscosity, including its relation to a topological invariant known as the shift when rotational symmetry is preserved. Next, I will show how the Hall viscosity can be computed from a Kubo formula, and the experimental implications this insight yields. In the second part of the talk, I will examine the fate of the Hall viscosity when rotational symmetry is broken. Through a combination of field theory and numerical techniques, I will show that rotational symmetry breaking allows for the introduction of a new topological quantum number characterizing quantum Hall states. I will present results on the stress response of quantum Hall systems in a tilted magnetic field. In addition to the Hall viscosity, I will show that the stress tensor acquires an unusual anisotropic ground state average, leading to anomalous elastic response functions.
May 1, 2019
PRC 201 | Wednesday, 1:30 pm
## Pankaj Mehta, Boston University
#### Toward a Statistical Mechanics of Microbiomes
A major unresolved question in microbiome research is whether the complex ecological patterns observed in surveys of natural communities can be explained and predicted by fundamental, quantitative principles. Bridging theory and experiment is hampered by the multiplicity of ecological processes that simultaneously affect community assembly and a lack of theoretical tools for modeling diverse ecosystems. In the first part of the talk, I will present a simple ecological model of microbial communities that reproduces large-scale ecological patterns observed across multiple experimental settings including compositional gradients, clustering by environment, diversity/harshness correlations, and nestedness. Surprisingly, our model works despite having a “random metabolisms” and “random consumer preferences”. This raises the natural of question of why random ecosystems can describe real-world experimental data. In the second, more theoretical part of the talk, I will answer this question by showing that when a community becomes diverse enough, it will always self-organize into a stable state whose properties are well captured by a “typical random ecosystems”. If time permits, I will also highlight surprising connections between ecological dynamics, constrained optimization, and kernel-based machine learning methods such as Support Vector Machines.
Talk is based on: Advani et al J. Stat. Phys (2018); Golford et al Science (2018); Marsland et al. PLoS Comp Bio (2019); arXiv:1809.04221;arXiv:1901.09673; arXiv:1904.02610; unpublished
##### Computations in Science
May 1, 2019
KPTC 206 | Wednesday, 12:15 pm
## Gregory Fu, CALTECH
#### Nickel-Catalyzed Substitution Reactions of Alkyl Electrophiles
##### Kharasch Lecture
May 1, 2019
GCIS W301 | Wednesday, 12:00 pm
## Jay Foley, The Department of Chemistry, William Patterson University
#### Jay Foley, The Department of Chemistry, William Patterson University
The interaction between light and nanostructures can give rise to a number of different resonant phenomena, including plasmon resonances in metal nanoparticles, excitonic resonances in semiconductor nanoparticles, and scattering resonances in dielectric nanoparticles. An exciting feature of these resonant phenomena is that they provide opportunities to control the flow of optical energy at the nanoscale, a prospect which has important implications for renewable energy technologies among others. Creating hybrids of various nanoscale materials can often lead to new emergent phenomena, giving us yet more levers of control over light at the nanoscale. I will discuss two classes of hybrid nanostructures that give rise to emergent phenomena that show promise for energy conversion applications. The first class of hybrids includes multilayer planar nanomaterials whose emergent properties allow us to control how they radiate heat. The second class of hybrids consists of dielectric and metal nanospheres whose emergent properties offer new routes for light initiated energy transfer, including hot-carrier transfer and resonance energy transfer, to small molecules. I will describe ongoing efforts to develop simple but accurate theoretical and computational techniques to study and design these systems. Host: David Mazziotti, 4-1762 or via email at damazz@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
April 30, 2019
GCIS W301 | Tuesday, 4:00 pm
## Kharasch Lecture: Professor Gregory Fu, Caltech
#### Nucleophilic Substitution Reactions: A Radical Alternative to Sn1 and Sn2 Reactions
Classical methods for achieving nucleophilic substitutions of alkyl electrophiles (SN1 and SN2) have limited scope and are not generally amenable to enantioselective variants that employ readily available racemic electrophiles. In this presentation, we will describe how the combination of radical chemistry and transition-metal catalysis has opened the door to addressing the challenges of reactivity and of enantioselectivity in nucleophilic substitution reactions of secondary and tertiary alkyl electrophiles.
##### Chemistry
April 29, 2019
Kent 120 | Monday, 3:45 pm
## Kristan Jensen, San Francisco State University
#### de Sitter, SYK, and coadoint orbits
April 29, 2019
PRC 201 | Monday, 1:30 pm
## Philippe Bourrianne, Mechanical Engineering, MIT, Cambridge, MA, USA
#### Colloids and liquids from suspensions to superhydrophobicity
Colloidal suspensions are ubiquitous in our daily life. Micrometric particles dispersed in a solvent are indeed present in common liquids such as paints, inks or even food products. We will discuss the properties of those colloidal suspensions from their liquid phase to solid deposits after drying.
First, colloidal suspensions exhibit a wide range of rheological behaviors from shear-thinning to yield stress fluids. We will focus on the shear-thickening transition when dense suspensions experience a dramatic increase in viscosity above a critical shear-stress. By changing the physico-chemistry of the particles, we can tune this rheological transition and thus understand the interactions involved in this behavior.
Increasing concentration can also be noticed during drying when solvent evaporates: particles finally form a solid deposit. After drying, a drop of a colloidal suspension leads to a variety of patterns from coffee-stain to more homogeneous coatings in paintings. We will discuss the effect of the initial concentration of particles on the drying pattern and on the subsequent mechanical instabilities.
Finally, after the whole drying of the colloidal suspension, coatings are achieved. Depending of the nature of the particles, we can tune the wettability of the substrate up to superhydrophobic solid. We will briefly discuss how such a water-repellent substrate can allow levitation of liquids.
We are grateful to host Thomas Videbaek for arranging this visit.
##### MRSEC Baglunch
April 26, 2019
GCIS E223 | Friday, 3:00 pm
## Professor Yan Xia: Stanford University
#### Building and Breaking Strained Molecular Ladders to Develop Antiaromatic and Force-Responsive Materials
##### Chemistry
April 26, 2019
Kent 120 | Friday, 1:45 pm
## Herbert Mayr, Ludwig-Maximilians-Universität München
#### Mythology in Organic Chemistry: How Obsolete Concepts Survive
##### Chemistry
April 25, 2019
Kent 102 | Thursday, 4:00 pm
## Ritchie Patterson, Cornell University
#### Mastering Bright Electron Beams
Bright electron beams enable electron microscopy, brilliant X-ray sources, and collisions that probe the interactions of elementary particles. They are also essential for semiconductor device fabrication, the sterilization of medical equipment and the production of heat shrink tubing and tires. Achieving increased brightness and extending the scientific and industrial reach of these beams poses basic scientific questions about beam production, acceleration and transport, whose answers will require expertise spanning disciplines from ab initio physics, materials science, surface chemistry, and mathematics to accelerator physics. A new NSF Science and Technology Center, the Center for Bright Beams, has been formed to do exactly this. The colloquium will present some of the key scientific questions involved in producing and using future bright beams and Center for Bright Beams early results.
##### Physics Colloquium
April 25, 2019
KPTC 106 | Thursday, 3:30 pm
## Andrew Houck, The Department of Electrical Engineering, Princeton University
#### Many-body Quantum Optics in Superconducting Circuits
Superconducting circuits provide an excellent platform for the study of non-equilibrium quantum simulation and quantum simulation in exotic lattices. In circuit QED, a superconducting qubit mediates very strong effective photon-photon interactions. In networks of circuit QED elements, a competition between hopping and interactions can be realized, leading to steady state phase transitions in a damped driven system. Here, we will discuss dynamical phase transitions in a circuit QED dimer and dissipative phase transitions observed in a one-dimensional lattice, tunable interactions in a bandgap medium, and progress towards understanding lattices in curved space.Host: Jonathan Simon, 2-9661 or via email at simonjon@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### JFI Special Seminar
April 25, 2019
KPTC 206 | Thursday, 12:00 pm
## IME Distinguished Colloquium Series - Jeffrey Moore
Professor Jeffrey Moore from University of Illinois will speak as part of the IME Distinguished Colloquium Series.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
April 24, 2019
KCBD 1103 | Wednesday, 4:00 pm
## Naomi Ginsburg, The Department of Physics, University of California-Berkeley
#### How Do Emerging Light Harvesting Materials Form, Transform, and Transport Energy at the Nanoscale?
We are interested in the optoelectronic properties and the spatiotemporal nature of photogenerated energy carrier transport of emerging semiconducting materials, broadly defined. These materials include not only semiconductors who basic building blocks are atoms but also those made of small particles or molecules, including the aggregates of molecular pigments involved in photosynthesis. Those of greatest interest to us are ones that spontaneously assemble into organized and/or densely packed solid structures starting from the solution phase or whose structures can be thermodynamically or kinetically transformed. What are the multiscale relationships between the dynamics and products of material formation and transformation and the emergent electronic properties of these materials? How does disorder, as an inherent byproduct of the assembly process, affect these properties both locally and macroscopically?
To answer these questions I will provide examples of our work to elucidate the mechanisms for ultrafast photoinduced energy transport and for the slower dynamics of material transformations in a wide range of emerging, heterogeneous electronic materials. This work has often required the development of spectroscopic nano-imaging modalities with new, more appropriate combinations of spatial sensitivity and temporal resolution. As examples, I will take you first on a journey with transient optical elastic scattering to reveal the nature of energy flow–structure correlations for various photogenerated species in virtually any semiconductor. In related materials, we will then explore the nature of structural phase transitions both at and away from equilibrium using cathodoluminescence microscopy – the mapping of light emitted from a sample in a scanning electron microscopy – and in situ X-ray scattering.
Host: Sara Sohail,2-6066 or via email at skhess@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### Closs Lecture
April 24, 2019
GCIS W301 | Wednesday, 2:15 pm
## Risi Kondor, University of Chicago
#### Covariant neural network architectures for learning physics
Deep neural networks have proved to be extremely effective in image recognition, machine translation, and a variety of other data centered engineering tasks. However, generalizing neural networks to learning physical systems requires a careful examination of how they reflect symmetries. In this talk we give an overview of recent developments in the field of covariant/equivariant neural networks. Specifically, we focus on three applications: learning properties of chemical compounds from their molecular structure, image recognition on the sphere, and learning force fields for molecular dynamics. The work presented in this talk was done in collaboration with Brandon Anderson, Zhen Lin, Truong Son Hy, Horace Pan, and Shubhendu Trivedi.
##### Computations in Science
April 24, 2019
KPTC 206 | Wednesday, 12:15 pm
## Joseph Mindell, MD-PhD, NINDS-NIH
#### Protons to Patients: Evaluating the role of the chloride transporter ClC-7 in lysosomal function
Lysosomes are essential focal points of cellular metabolism, digesting a wide range of macromolecules provided by endocytosis or autophagy. To this end, lysosomes rely on their highly acidic luminal pH to promote the function of their many enzymes, a pH generated by the action of a v-Type proton pumping ATPase. Since this transporter is electrogenic, parallel ion movements must occur to dissipate the generated membrane potential and promote bulk proton flux. The Cl-/H+ antiporter, ClC-7, has been proposed to play this role, moving Cl- in parallel to protons. However, the function of ClC-7 has been controversial, with conflicting reports on its contribution to lysosomal acidification. I will discuss recent work aimed at understanding the role of ClC-7 and other proteins in the acidification process. My lab uses a multipronged approach, utilizing a variety of methods to probe these processes, from flux studies in isolated organelles to knockout mice and quantitative imaging methods. In addition I will report on two patients with a novel disease manifested as widespread lysosomal dysfunction but no bone abnormalities, who both have the same missense mutation in ClC-7. Acidification defects in cells from these patients, along with electrical currents from the mutant transporter provide novel insight into ClC-7 function. These findings provide strong support for an important role of ClC-7 in the lysosomal acidification process and suggest opportunities for therapies for these patients.
##### Biophysical Dynamics
April 23, 2019
GCIS W301 | Tuesday, 12:00 pm
## Yogi Surendranath: MIT
#### Bridging Molecular and Heterogeneous Electrocatalysis Through Graphite Conjugation
##### Chemistry
April 22, 2019
Kent 120 | Monday, 1:45 pm
## Jon Sorce, Stanford University
#### Tensor Networks and Emergent Spacetime in AdS/CFT
One of the most remarkable insights gleaned from studying the AdS/CFT correspondence is that information about the structure of spacetime can be recovered by studying entanglement in the underlying quantum-gravitational degrees of freedom. As such, there is good evidence to believe that understanding entanglement in quantum systems is essential to understanding the emergence of spacetime in quantum gravity. In this talk, I will present recent on work in which general principles from quantum information theory are used to distill emergent geometric structures—so-called “tensor networks”—from arbitrary states in quantum field theory. When these states are chosen from conformal field theories in the AdS/CFT correspondence, the tensor network geometry matches the spacetime geometry of the AdS bulk.
April 22, 2019
PRC 201 | Monday, 1:30 pm
## Mechanical duality
Discussion over lunch: 12:00
Discussion over duality: 12:15
##### MRSEC Baglunch
April 19, 2019
GCIS E123 | Friday, 12:00 pm
## AbbVie Visit Day
#### Hosted by Chemistry and My CHOICE
To register for lunch, afternoon seminars and Q&A session please go to https://abbvieday2019.eventbrite.com
9:30am Jay Cui (Associate Director, AbbVie Ventures) "Landscape in Early Investments in Life Sciences"
RESERVATION REQUIRED: Contact Prof. Dickinson dickinson@uchicago.edu
12:00pm Lunch with Trainees ~ Limited seats available. Registration required.
1:15pm SEMINARS:
Amanda Dombrowksi (Sr. Scientist II) "Enabling and Accelerating Drug Discovery with Chemistry Technologies"
Aleks Baranczak (Sr. Scientist) "Mechanistic Characterization at the Molecular Level: Chemical Biology in Drug Discovery"
##### Chemistry
April 19, 2019
Kent 120 | Friday, 9:30 am
## Rob Phillips, California Institute of Technology
#### How Schrodinger's Cat Became a Cat
##### Physics Colloquium
April 18, 2019
KPTC 106 | Thursday, 3:30 pm
## Detlef Lohse, University of Twente
#### Evaporation of multicomponent droplets
While the evaporation of a single component droplet meanwhile is pretty well understood, the richness of phenomena in multicomponent droplet evaporation keeps surprising us. In this talk we will show and explain several of such phenomena, namely evaporation-triggered segregation thanks to either weak solutal Marangoni flow or thanks to gravitational effects, and the evaporation of ternary liquid droplet, which can lead to spontaneous nucleation of droplets consisting of a new phase. We will also show how this new phase can be utilized to self-lubricate the droplet in order to suppress the coffee stain effects. The research work shown in this talk combines experiments, numerical simulations, and theory.
##### Computations in Science
April 18, 2019
GCIS E223 | Thursday, 2:00 pm
## Johanna Knapp, University of Vienna
#### GLSMs, CYs, and Localization
Gauged linear sigma models (GLSMs) can be used to study Calabi-Yaus and their moduli spaces. Recent results in supersymmetric localization have made it possible to compute exact, i.e. fully quantum corrected, quantities that are relevant in string compactifications directly in the GLSM. After a review of the general framework, I will present some recent applications, with focus on the sphere and hemisphere partition function of the GLSM.
##### Theory Seminar
April 17, 2019
PRC 201 | Wednesday, 1:30 pm
## Nikta Fakhri, MIT
#### Thermodynamics of active matter
Cellular structures constantly consume and dissipate energy on a variety of spatiotemporal scales in order to function. While progress has been made in elucidating their organizing principles, much of their thermodynamics remains unknown. In this talk, I will address the question: why measure dissipation in such nonequilibrium systems? I will show that by measuring a multi-scale irreversibility (time-reversal asymmetry) one can extract model-independent estimates of the time-scales of energy dissipation based on time series data collected in an experimental biological system. I further demonstrate that the irreversibility measure maintains a monotonic relationship with the underlying biological nonequilibrium activity. The basic idea of estimating irreversibility for various levels of coarse-graining is quite general; we expect it to lead to important inferences whenever there is a well-defined notion of dissipative scale.
##### Computations in Science
April 17, 2019
KPTC 206 | Wednesday, 12:15 pm
## Lulu Qian, The Department of Bioengineering, Caltech
#### Algorithmic and Architectural Foundations for Programmable Molecular Machines: DNA Robots, Information-processing Circuits, and Reconfigurable Nanostructures
The primary focus of my lab is to help establish the algorithmic and architectural foundations for artificial molecular machines, through rationally designed and synthesized nucleic-acid systems that exhibit programmable behaviors. We aim to better understand how complex network behaviors arise from simple molecular building blocks, to establish forward engineering principles for information processing with molecules, to precisely manipulate matter at the nanoscale and embed control within biochemical environments, and eventually, to create artificial molecular machines that approach the complexity and sophistication of the natural ones and are fully programmable by humans.
In this talk, I will discuss our recent contributions in three areas: molecular robots, information-processing circuits, and reconfigurable DNA nanostructures.
First, we developed molecular robots that autonomously and collectively perform a sophisticated mechanical task: exploring the surface of a DNA nanostructure, picking up multiple types of cargo molecules and sorting each type to a designated location (Thubagere et al., Science, 2017). This work exploits random walks for energy-efficient mechanical behaviors, demonstrates the importance of simple algorithms and modular building blocks, and provokes further development of general-purpose molecular robotics.
Second, we created biochemical circuits that can classify highly complex and noisy molecular information, based on the similarity to a set of memories stored in DNA-based artificial neural networks (Cherry et al., Nature, 2018). This work shows how competition between molecules can be used to process complex information, establishes the record for how much intelligence can be built into artificial molecular machines, and paves the way for programming molecules to learn from their environment.
Finally, we invented a hierarchical and recursive strategy that allows DNA nanostructures with increasing sizes and arbitrary patterns to be created using a small and constant set of unique DNA strands (Tikhomirov et al., Nature, 2017). Subsequently, we discovered a simple yet powerful mechanism that controls the dynamic interactions between complex DNA nanostructures. Utilizing this mechanism, we demonstrated information-based autonomous reconfiguration in systems of interacting DNA nanostructures (Petersen et al., Nature Communications, 2018). Together, the two approaches provide significantly advanced structural components for building artificial molecular machines.
I hope to illuminate an ever-more-promising future for molecular sciences, empowered by the advances in DNA nanotechnology and molecular programming – a field that has its roots in physics, computer science, and engineering, and is anticipated to revolutionize the methods in many othe
##### The Tuesday JFI Seminar
April 16, 2019
GCIS W301 | Tuesday, 4:00 pm
## Eric Klein, PhD, Rutgers University-Camden
#### Adaptation to phosphate-limitation in Caulobacter crescentus
Bacteria are constantly encountering new environmental conditions that require a variety of adaptations including metabolism, gene expression, and cellular morphology. In our model organism, Caulobacter crescentus, adaptation to phosphate limitation includes the dramatic elongation of its polar stalk appendage. Recent work from our lab has shown that stalk elongation and adaptation to phosphate starvation involves changes in membrane composition, peptidoglycan organization, and sugar metabolism. Importantly, our findings have implications for other bacterial species related to pathogenesis and cell growth.
##### Biophysical Dynamics
April 16, 2019
GCIS W301 | Tuesday, 12:00 pm
## Thomas Muir: Princeton University
#### Painting Chromatin with Synthetic Protien Chemistry
##### Chemistry
April 15, 2019
Kent 120 | Monday, 3:45 pm
## Emil Yuzbashyan, Rutgers University
#### Integrable time-dependent Hamiltonians
In the emerging field of coherent many-body dynamics, we seek to understand the behavior of an isolated quantum many-body system driven far from equilibrium by changing its Hamiltonian in time. In this talk, I will identify a general class of many-body and matrix Hamiltonians for which this problem is exactly solvable. In particular, I will outline a way to make the parameters (e.g., the interaction strength) of certain quantum integrable models time-dependent without breaking their integrability.
Interesting many-body models that emerge from this approach include a superconductor with the interaction strength inversely proportional to time, a Floquet BCS superconductor, and the problem of molecular production in an atomic Fermi gas swept through a Feshbach resonance as well as various models of multi-level Landau-Zener tunneling. I will solve the non-stationary Schrodinger equation exactly for all these models and discuss some interesting physics that emerges at large times.
April 15, 2019
PRC 201 | Monday, 1:30 pm
## The heart of crumpling
#### or how to (in)crease your core
Bring your food to eat at 12:00
Bring a tidbit to tell
The story begins at 12:15
##### MRSEC Baglunch
April 12, 2019
GCIS E123 | Friday, 12:00 pm
## William Unruh, University of British Columbia
#### Experimental Measurement of the Hawking emission (?)
Hawking's discovery 45 years ago that black holes, instead of ever growing sinks of energy, emitted radiation and very slowly shrank in size and mass, was one of the most surprising discoveries of physics in the 20th century. Of course physics in an experimental or at least observational science. But small enough black holes to see this effect are rare.
However analogies exist in which one could hope to see this effect, namely flowing fluids where the velocity of flow exceeds the velocity of sound. While
the classical correlate of this has been measured for surface waves in water, recently the quantum effect has also been measured for sound waves in a BEC. I will review the Hawking effect, the measurement in water and these new measurements where one can claim to have seen at least some of the quantum effects of the Hawking process.
##### Physics Colloquium
April 11, 2019
KPTC 106 | Thursday, 3:30 pm
## Bernhard Breit, Albert-Ludwigs - University Freiburg
#### Rhodium-Catalyzed Addition of Pronucleophiles to Alkynes and Allenes: An Atom-Efficient Alternative to the Tsuji-Trost Reaction
##### Special Organic Syntheses Lecture
April 11, 2019
GCIS W301 | Thursday, 2:00 pm
## IME Distinguished Colloquium Series - Rohit Karnik
Professor Rohit Karnik from Massachusetts Institute of Technology will speak as part of the IME Distinguished Colloquium Series.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
April 10, 2019
KCBD 1103 | Wednesday, 4:00 pm
## Oskar Hallatschek, UC Berkeley
#### The role of jackpot events in the dynamics of evolution
Luria and Delbrück discovered that mutations that occur early during a growth process lead to exceptionally large mutant clones. These mutational “jackpot” events are thought to dominate the genetic diversity of growing cellular populations, including biofilms, solid tumors and developing embryos. In my talk I show that jackpot events can be generated not only when mutations arise early but also when they occur at favourable locations, which exacerbates their role in adaptation and disease. I will also consider the impact of recurrent jackpot events, which lead to a bias favoring alleles that happen to be present in the majority of the population. I argue that this peculiar rich-get-richer phenomenon is a general feature of evolution driven by rare events.
##### Computations in Science
April 10, 2019
KPTC 206 | Wednesday, 12:15 pm
## Zeger Hens, The Department of Inorganic & Physical Chemistry, Ghent University
#### Stimulated Emission by Colloidal Quantum Dots
Reducing the size of materials down to a few nanometer is a powerful approach to control material properties by design. A case in point are semiconductors, where size quantization leads to a size- and shape-dependent band gap once crystal dimensions become comparable or smaller than the exciton Bohr radius; an observation first made almost 40 years ago.
This talk explores the opportunities size reduction brings for creating new optical gain materials. Using free carrier gain in bulk semiconductors as a reference, we discuss 4 different model systems, each exemplifying a different mechanism to attain net stimulated emission.
First, we focus on large perovskite nanocrystals. This example helps introducing the experimental methods we use to characterize gain materials and shows that weakly confined semiconductors have gain characteristics highly similar to the corresponding bulk material. Next, we highlight the impact of size quantization using stimulated emission by CdSe/CdS quantum dots as a second example, which is introduced as a unique model system of band-edge gain by quantum dots. Interestingly, we show that tweaking the core and shell dimensions provides unique possibilities to tune the optical gain characteristics of these materials.
Building on the conditions that yield the lowest gain thresholds in CdSe/CdS quantum dots, we discuss two possibilities to overcome intrinsic limitations of band-edge gain. First, we turn to two-dimensional colloidal nanoplatelets, were we show that stimulated emission through excitonic molecules leads to a combination of low gain thresholds and high gain coefficients. Finally, we propose transitions involving localized band-gap states, exemplified by HgTe quantum dots, as a way to achieve nearly thresholdless gain by colloidal semiconductor nanocrystals. We conclude this presentation by a short outlook on the prospects and challenges on using colloidal quantum dots as a gain material for microlasers. Host(s): Philippe Guyot-Sionnest, 2-7461; Email-pgs@uchicago.edu & Dmitri Talapin, 4-2607; Email - dvtalapin@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or via email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
April 9, 2019
GCIS W301 | Tuesday, 4:00 pm
## Monika Scholz, PhD, Princeton
#### Reading the mind of the worm: Brain-wide neural dynamics predict behavior in C. elegans
How does a nervous system control animal behavior? While models of behavior and neural computation exist, investigating the connection experimentally is challenging in even the simplest organisms. It is only recently that tools have become available to image the behavior and neural dynamics simultaneously in the roundworm C. elegans. Its small nervous system with only 302 neurons and stereotyped behaviors allow us to probe how well simple models perform in predicting behavior from neural dynamics alone. We use a suite of microscopy tools and a calcium-sensitive fluorescent protein to image the activity of a large number of neurons in the animals brain during locomotion. Using a linear model, we predict forward and backward velocity as well as turns and turn direction from neural activity. Using our model and the animals neural activity, we can predict the worms posture for up to 10 seconds. I will discuss the implications for understanding how neural networks encode information and how this information could be used in coordinating complex motor tasks.
##### Biophysical Dynamics
April 9, 2019
GCIS W301 | Tuesday, 12:00 pm
## Richa Batra, Creative Machines Lab, Columbia University
#### Particle Robotics: Statistical Mechanics of Loosely Coupled Robotic Components
Traditional robots typically consist of highly-engineered modules, each performing specialized roles to complete
complex tasks. While these robots are accomplishing functions of increasing complexity with greater precision,
they frequently struggle when presented with novel environments, or the failure of a single component. This talk
will explore robotic systems inspired by biology and nature, in which adaptable and resilient behaviors are
achieved by combining and coordinating relatively simple components. Like atoms forming crystals, cells
contracting muscle tissue, or ants foraging for food, complexity can arise from relatively simpleparts.
The robotic system presented, called particle robotics, exploit statistical mechanics of loosely coupled components. This
talk will mainly focus on a particle robot where each component, or particle, is only capable of uniform volumetric oscillations.
The oscillations of the individual particles can be phase-modulated by a global signal. Despite the amorphous
configurations and lack of direct control, we find that we are able to coordinate the overall behavior of the robot. We
demonstrate the scalability and resilience of such robots, both to noisy components and to component failure. In addition,
particle robots comprising components that exhibit different individual behaviors will be presented. The particle robotics
paradigm presented here suggests that large-scale, amorphous robotic systems can exhibit deterministic behavior even
when composed of simple stochastic component.
##### Special JFI Seminar
April 9, 2019
GCIS E123 | Tuesday, 11:30 am
## Floyd Romesberg, The Scripps Research Institute
#### A Semi-Synthetic Organism that Stores and Retrieves Increased Genetic Information
##### Closs Lecture
April 8, 2019
Kent 120 | Monday, 4:00 pm
## Zhihao Zhuang, University of Delaware
#### Chemical Approaches for Investigating Protein Deubiquitination
The human ubiquitin proteasome system is involved in many cellular processes, including protein quality control, epigenetic regulation, DNA damage repair and tolerance. Many cellular events are regulated through reversible protein ubiquitination. Deubiquitinases (DUBs) as an important class of enzymes in the ubiquitin proteasome system have been associated with various human diseases including cancer, neurological disorders, and viral infection. DUBs are emerging as promising targets for pharmacological intervention and major efforts targeting DUBs for drug discovery are underway. I will discuss the development of a series of novel DUB probes for elucidating the ubiquitin chain linkage and target protein specificity of DUBs. We also developed cell-permeable DUB probes that allow profiling of DUB activities in intact cells. Using the newly developed probes and chemical proteomics approaches, exciting new findings on the DUB specificity and catalysis were obtained. Our efforts led to much needed tools and approaches for understanding the complex biology of protein ubiquitination and will drive the drug discovery efforts targeting the many DUBs in humans.
##### Chemistry
April 5, 2019
Kent 120 | Friday, 1:45 pm
## Luca Grandi, University of Chicago
#### TBA
##### Physics Colloquium
April 4, 2019
KPTC 106 | Thursday, 3:30 pm
## Christof Sparr, University of Basel
#### Cataltic Cascade Reactions Inspired by Polyketide Biosynthesis
##### Special Organic Syntheses Lecture
April 4, 2019
GCIS W301 | Thursday, 1:30 pm
## Semyon Klevtsov, University of Cologne
#### Geometric responses of Quantum Hall states
One way to understand the Quantum Hall effect is to consider QH wave functions on Riemann surfaces. Electromagnetic and gravitational responses correspond to varying metric and magnetic field and
quantized coefficients are encoded in Chern classes on associated parameter (moduli) spaces. We report on our recent work and discuss various questions arising in this approach.
April 3, 2019
PRC 201 | Wednesday, 3:00 pm
## Greg Bewley, Cornell University
#### The structure of turbulence and of granular beds
My work centers on turbulence, both its intrinsic properties and its role in various environmental settings. Over a bed of sand, it lifts and transports the grains. Left to itself, the turbulence slowly dissipates and disappears. In the first part of my talk, I will introduce experiments motivated by the question of how quickly turbulence consumes kinetic energy. Surprisingly we do not generally know how to predict the consumption rate, though the process underlies general turbulence phenomena and modeling. What we found is that the rate is invariant with respect to changes in the intensity of the turbulence, so long as the flow is slow relative to the speed of sound. I will introduce a new experiment in which we observe how the picture changes when the flow is no longer so slow. In the second part of my talk, I describe an experiment motivated by the question of how turbulence deforms granular beds. The experiments reveal a new mechanism that produces bedforms, a mechanism associated with fluctuating pressure gradients generated in a fluid-saturated particle bed by a plate oscillating in the water above it.
##### Computations in Science
April 3, 2019
KPTC 206 | Wednesday, 12:15 pm
## David Weiss, The Department of Physics, Penn State University
#### Quantum Computing with Neutral Atoms
I will present our approach to making a quantum computer
using atoms in a 3D optical lattice. I will focus on our recent
demonstration of perfect lattice filling in 4x4x3 and 5x5x2 arrays,
which involved an experimental realization of Maxwell's demon. I will
also describe how we have accomplished high fidelity single qubit gates
(0.997) and high fidelity lossless state detection (0.9994).ost: Cheng Chin, 2-7192 or via email at cchin@jfi.uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
April 2, 2019
GCIS W301 | Tuesday, 4:00 pm
## Nan Hao, PhD. UCSD
#### Systems biology of single-cell aging
##### Biophysical Dynamics
April 2, 2019
GCIS W301 | Tuesday, 12:00 pm
## Brian M. Stoltz, California Institute of Technology
#### Complex Natural Products as a Driving Force for Discovery in Organic Chemistry
##### Bristol-Myers Squibb Lecture
April 1, 2019
GCIS W301 | Monday, 4:00 pm
## Nicholas Meanwell, Bristol-Myers Squibb
#### Inhibitors of HIV-1 Maturation
##### Bristol-Myers Squibb Lecture
April 1, 2019
GCIS W301 | Monday, 3:00 pm
## Ronak Soni, Stanford University
#### Scalar Asymptotic Charges and Dual Large Gauge Transformations
In recent years soft factorization theorems in scattering amplitudes have been reinterpreted as conservation laws of asymptotic charges. In gauge, gravity, and higher spin theories the asymptotic charges can be understood as canonical generators of large gauge symmetries. Such a symmetry interpretation has been so far missing for scalar soft theorems. We remedy this situation by treating the massless scalar field in terms of a dual two-form gauge field. We show that the asymptotic charges associated to the scalar soft theorem can be understood as generators of large gauge transformations of the dual two-form field. The dual picture introduces two new puzzles: the charges have very unexpected Poisson brackets with the fields, and the monopole term does not always have a dual gauge transformation interpretation. We find analogs of these two properties in the Kramers-Wannier duality on a finite lattice, indicating that the free scalar theory has new edge modes at infinity that canonically commute with all the bulk degrees of freedom.
April 1, 2019
PRC 201 | Monday, 1:30 pm
## Arvind Murugan, University of Chicago
#### Materials that learn from examples
We usually design materials to target desired behaviors defined in a top-down manner. Learning theory offers an alternative where desired behaviors are defined by a list of examples. In learning, a material changes as it physically experiences such examples. We then test the material to see if it has the “correct” response to novel conditions never seen before (‘generalization’). Can real materials ‘learn’ from their history in this manner? We study the physical requirements for such information processing in terms of disorder, non-equilibrium driving and non-linearities using theory and experiments in disordered sheets, elastic networks, and molecular self-assembly.
##### Computations in Science
March 27, 2019
KPTC 206 | Wednesday, 12:15 pm
## Muhittin Mungan, University of Bonn
#### Cyclic Annealing, Random Maps & Memories
Disordered magnets, martensitic mixed crystals, and glassy solids can be irreversibly deformed by subjecting them to external deformation. The
deformation produces a smooth, reversible response punctuated by abrupt
relaxation glitches". Under appropriate repeated forward and reverse
deformation producing multiple glitches, a strict repetition of a single
sequence of microscopic configurations often emerges. It turns out that
the athermal evolution of the system configuration from glitch to glitch
can be described as a pair of maps that map states into one-another. One
map U controls forward deformation; a second map D controls reverse
deformation. The disorder of the system renders these maps random. We
will first consider iterations of a given sequence of forward and
reverse maps. Such maps necessarily produces a convergence to a fixed
cyclic repetition of states covering multiple glitches. Using numerical
sampling, we characterize the convergence properties of four types of
random maps implementing successive physical restrictions. These maps
show only the most qualitative resemblance to annealing simulations.
However, they suggest further properties needed for a realistic mapping
scheme. Formulating the irreversible part of the dynamics in terms of a
pair of maps (U,D) allows one to understand phenomena such as
return-point memory entirely in terms of the properties of these maps.
After briefly reviewing these types of features, we discuss how such a
formulation can help us in understanding the formation of memory in
matter. This is ongoing joint work with T. Witten, M.Terzi, I. Regev,
K. Dahmen and S. Sastry. Host: Thomas Witten, 2-0947 or via email at t-witten@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### JFI Special Seminar
March 26, 2019
GCIS E223 | Tuesday, 4:00 pm
## IME Distinguished Colloquium Series - Alberto Salleo
Professor Alberto Salleo from Stanford University will speak as part of the IME Distinguished Colloquium Series.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
March 20, 2019
KCBD 1103 | Wednesday, 4:00 pm
## Hana El-Samad, University of California, San Francisco
#### Biological control: The versatile ways in which cells use feedback loops
In 1939, Walter Cannon wrote in his book The Wisdom of the Body: “The living being is an agency of such sort that each disturbing influence induces by itself the calling forth of compensatory activity to neutralize or repair the disturbances”. Since this remarkable statement that postulates the use of feedback control to support life, we have come to appreciate that the use of feedback loops is ubiquitous at every level of biological organization, from the gene to the ecosystem. In this talk, we introduce a technology to study feedback operation in endogenous biological systems. We also discuss some recent progress in building feedback control systems with biological molecules that can modulate the operation of cellular pathways
##### Computations in Science
March 20, 2019
KPTC 206 | Wednesday, 12:15 pm
## Monica Allen, The Department of Physics, University of California-San Diego
#### Visualization of Topological States of Matter Using Microwave Impedance Microscopy
A main thrust of condensed matter physics concerns the discovery of new electronic states in emerging materials. One example is the rapidly expanding class of topological materials, which are posited to enable realization of non-abelian particles and topological quantum computing. In this talk, I will discuss how exotic phenomena can arise from the interplay of ferromagnetism and topology. We employ microwave impedance microscopy (MIM), which characterizes the local complex conductivity of a material, to directly image chiral edge modes and phase transitions in a magnetic topological insulator. Finally, I will outline how MIM could be used in the future to visualize and manipulate Majorana modes, an emerging platform for quantum information processing.Host: David Schuster at 2-7191 or David.Schuster@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu
##### The Tuesday JFI Seminar
March 19, 2019
GCIS W301 | Tuesday, 4:00 pm
## Raymond Kapral, University of Toronto
#### Molecular Machines and Synthetic Motors: Active Motion on Nanoscales
Molecular machines or motors in the cell operate under nonequilibrium
conditions and extract chemical energy from their surroundings to perform a
variety of transport and other biological functions. Synthetic nanomotors
without moving parts also operate under nonequilibrium conditions using
chemical energy to move in solution, and can transport cargo and perform
other functions. The operations of these tiny motors differ markedly from
their macroscopic counterparts. The mechanisms that lead to the directed
motion of chemically-powered motors, as well as some of their potential
applications, will be discussed. Since both molecular machines and synthetic
motors must respect the basic laws of dynamics while functioning under
nonequilibrium conditions, there are similarities between how these very
different nanomotors function. Systems containing many synthetic motors can
display collective behavior leading to active self-assembly, swarming and
other collective states that differ from those in systems at equilibrium, and
these new structures will also be described.
##### Chemistry
March 18, 2019
Kent 120 | Monday, 3:45 pm
## Guanyu Zhu, IBM T.J. Watson Research Center
#### Universal logical gate sets with constant-depth circuits for topological and hyperbolic quantum codes
A fundamental question in the theory of quantum computation is to understand the ultimate space-time resource costs for performing a universal set of logical quantum gates to arbitrary precision. To date, common approaches for implementing a universal logical gate set, such as schemes utilizing magic state distillation, require a substantial space-time overhead.
In this work, we show that braids and Dehn twists, which generate the mapping class group of a generic high genus surface and correspond to logical gates on encoded qubits in arbitrary topological codes, can be performed through a constant depth circuit acting on the physical qubits. In particular, the circuit depth is independent of code distance d and system size. The constant depth circuit is composed of a local quantum circuit, which implements a local geometry deformation, and a permutation of qubits, separated by a distance of O(d). The permutation can be implemented by moving qubits or as a constant depth circuit using long-range SWAP operations (with a range set by d) on immobile qubits. Our results apply to both the abelian stabilizer codes (such as the surface code), and also to non-abelian Turaev-Viro codes.
When applied to anyon braiding or Dehn twists in the Fibonacci Turaev-Viro code based on the Levin-Wen model, our results demonstrate that a universal logical gate set can be implemented on encoded qubits in O(1) time through a constant depth unitary quantum circuit, and without increasing the asymptotic scaling of the space overhead. Our results for Dehn twists can be extended to the context of hyperbolic Turaev-Viro codes as well, which have constant space overhead (constant rate encoding). This implies the possibility of achieving a space-time overhead of O(d/log d), which is optimal to date for generic logical circuits.
These discoveries can greatly reduce the space and time overhead of fault-tolerant quantum computation, and in particular, significantly reduce the number of physical qubits per logical qubits. From a conceptual perspective, our results reveal a deep connection between the geometry of quantum many-body states and the complexity of quantum circuits. Our scheme also demonstrates at a fundamental level the significant advantage of long-range connectivity in quantum architectures for implementing fault-tolerant quantum computation.
March 18, 2019
PRC 201 | Monday, 12:00 pm
## Ramón Latorre, PhD, University of Valparaíso, Chile
#### Calcium- and voltage-activated (BK) channel: gating & modulation by auxiliary subunits
##### Biophysical Dynamics
March 14, 2019
GCIS W301 | Thursday, 12:00 pm
#### Enantioselective Chemical Synthesis Methods via Cooperative Catalysis
##### Chemistry
March 13, 2019
Kent 102 | Wednesday, 4:00 pm
## Maciej Koch-Janusz, ETH, Zurich
#### Information Theory, Machine Learning and the Renormalization Group
Physical systems differing in their microscopic details often display strikingly similar behaviour when probed at macroscopic scales. Those universal properties, largely determining their physical characteristics, are revealed by the renormalization group (RG) procedure, which systematically retains ‘slow’ degrees of freedom and integrates out the rest. We demonstrate a machine-learning algorithmbased on a model-independent, information-theoretic characterization of real-space RG, capable of identifying the relevant degrees of freedom and executing RG steps iteratively without any prior knowledge about the system. We apply it to classical statistical physics problems in 1 and 2D: we demonstrate RG flow and extract critical exponents. We also prove results about optimality of the procedure.
##### The JFI Theory Seminar
March 13, 2019
KPTC 206 | Wednesday, 12:00 pm
## Jennifer Dionne, PhD, Stanford University
#### Inside Out: Visualizing chemical transformations & light-matter interactions with nanometer-scale resolution
In Pixar’s Inside Out, Joy proclaims, “Do you ever look at someone and wonder, what’s going on inside?” My group asks the same question about materials whose function plays a critical role in energy and biologically-relevant processes. This presentation will describe new techniques that enable in situ visualization of chemical transformations and light-matter interactions with nanometer-scale resolution. We focus in particular on i) ion-induced phase transitions; ii) optical forces on enantiomers; and iii) nanomechanical forces using unique electron, atomic, and optical microscopies. First, we explore nanomaterial phase transitions induced by solute intercalation, to understand and improve materials for energy and information storage applications. As a model system, we investigate hydrogen intercalation in palladium nanocrystals. Using environmental electron microscopy and spectroscopy, we monitor this reaction with sub-2-nm spatial resolution and millisecond time resolution. Particles of different sizes, shapes, and crystallinities exhibit distinct thermodynamic and kinetic properties, highlighting several important design principles for next-generation storage devices. Then, we investigate optical tweezers that enable selective optical trapping of nanoscale enantiomers, with the ultimate goal of improving pharmaceutical and agrochemical efficacy. These tweezers are based on plasmonic apertures that, when illuminated with circularly polarized light, result in distinct forces on enantiomers. In particular, one enantiomer is repelled from the tweezer while the other is attracted. Using atomic force microcopy, we map such chiral optical forces with pico-Newton force sensitivity and 2 nm lateral spatial resolution, showing distinct force distributions in all three dimensions for each enantiomer. Finally, we present new nanomaterials for efficient and force-sensitive upconversion. These optical force probes exhibit reversible changes in their emitted color with applied nano- to micro-Newton forces. We show how these nanoparticles provide a platform for understanding intra-cellular mechanical signaling in vivo, using C. elegans as a model organism.
##### Biophysical Dynamics
March 12, 2019
GCIS W301 | Tuesday, 12:00 pm
## William A. Tisdale, MIT
#### Excitons, Entropy, and Nonequilibrium Transport in Semiconductor Nanomaterials
Structure, surface chemistry, and energetic disorder can dramatically affect excited state dynamics in low-dimensional systems. Using a combination of ultrafast laser spectroscopy, time-resolved optical microscopy, and kinetic modeling, I will show how these effects manifest in assemblies of colloidal quantum dots (QD) and atomically thin 2D semiconductors, which are promising components of next-generation photovoltaic and lighting technologies. In particular, I will demonstrate the counterintuitive role of entropy in the nonequilibrium population dynamics of excitons and charge carriers in nanoscale systems.
##### Chemistry
March 11, 2019
Kent 120 | Monday, 3:45 pm
## Xiangfeng Duan, UCLA
#### Van der Waals Integration Before and Beyong 2D Materials
The heterogeneous integration of dissimilar materials is a long pursuit of material science community and has defined the material foundation for modern electronics and optoelectronics. The current material integration strategy such as chemical epitaxial growth usually involves strong chemical bonds and is typically limited to materials with strict structure match and processing compatibility. Van der Waals (vdW) integration, in which pre-fabricated building blocks are physically assembled together through weak vdW interactions, offers an alternative bond-free material strategy without lattice and processing limitations, as exemplified by 2D vdW heterostructures. In this talk I will discuss the development, challenges and opportunities of this emerging approach, generalizing it for flexible integration of diverse material systems beyond 2D, and prospect its potential for creating artificial heterostructures or superlattices beyond the reach of existing materials.
##### Chemistry
March 8, 2019
Kent 120 | Friday, 1:45 pm
## Frank Graziani, Lawrence Livermore National Laboratory
#### High Energy Density Physics and Modeling of Extreme States of Matter
High energy density physics (HEDP) is the study of matter at extreme conditions where energy densities are in excess of 10^12 ergs/cc or equivalently, pressures are in excess of 1 Mbar. HEDP spans a wide range of phenomena, from the deep interiors of the giant planets to the hot plasmas typical of stellar interiors. Matter in the HEDP regime can involve some combination of the following phenomena, collective effects, electron degeneracy, radiation, atomic kinetics, strong particle-particle correlations, non-equilibrium and hybrid quantum-classical behavior. In this overview, I will explain why HEDP is an intellectually challenging and exciting research area that impacts basic science, energy, and national security. I discuss the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) which uses the concept of inertial confinement fusion (ICF) to create conditions where pressures far exceed 1 Mbar. The remainder of the talk is devoted to an important component of executing experiments at NIF or any other HEDP facility-simulation. I discuss the spectrum of computational approaches HEDP scientists use to model their experiments. I discuss the strengths and weaknesses of the various computational approaches and briefly touch on two recent advances that may hold promise to enhancing the current weaknesses. The talk ends with a discussion of the High Energy Density Sciences Center, which is an outreach organization at LLNL that is building a HEDP community through interactions of LLNL scientists with academic collaborators.
##### Physics Colloquium
March 7, 2019
KPTC 106 | Thursday, 4:00 pm
## John Briggs PhD, LMB-MRC
#### How to assemble a retrovirus: the view from cryo-electron microscopy
##### Biophysical Dynamics
March 7, 2019
GCIS W301 | Thursday, 12:00 pm
## Richard Schrock, MIT
#### Recent Advances in Olefin Metathesis with Molybdenum Catalysts
Molybdenum imido catalysts that are asymmetric at the metal, Mo(NR)(CHR')(X)(Y), where X and Y are different monoanionic ligands (e.g., a sterically demanding terphenoxide and a chloride or pyrrolide), have led to dramatic improvements in olefin metathesis chemistry in the last two years. Advances include the synthesis of monoaryloxide (X) chloride (Y) imido catalysts, kinetically E-selective macrocyclic ring-closing metathesis catalysts, stereoselective (Z or E) olefin metathesis reactions that use electron-poor olefins (ClCH=CHCl, CF3CH=CHCF3, BrCH=CHF, NCCH=CHCN), and ROMP reactions that yield cis,syndiotactic-A-alt-B copolymers from enantiomerically pure monomers. Mo=CHX complexes where X = Cl, Br, CF3, phosphonium, or CN have now been structurally characterized. The latest results concern the synthesis of the first catalytically active molybdenum oxo alkylidene complexes through addition of water to alkylidyne complexes. Other findings will be discussed as time permits.
##### Hillhouse Lecture
March 4, 2019
Kent 102 | Monday, 3:45 pm
## Jennifer Lin, IAS
#### Entanglement in gauge theories and gravity
In this talk I’ll review how to define entanglement entropy in lattice gauge theories, and explain why an analogy between EE in emergent gauge theories and in AdS/CFT suggests that the entropy of a black hole is related to a measure on the gauge group in the bulk. I’ll then provide an explicit example of this in Jackiw-Teitelboim gravity.
March 4, 2019
PRC 201 | Monday, 1:30 pm
## Jennifer Roizen, Duke University
#### Alcohol and Amine Derivatives Guide Position-Selective C–H Functionalization Reactions
Free radical reactions represent an important and versatile class of chemical transformations. Nitrogen-centered radical applications remain underexplored due to the lack of convenient methods for their generation. Recent advances have improved access to nitrogen-centered radicals through photoredox-mediated oxidation of two such directing groups: amides and sulfonamides. Guided by this approach, we hypothesized that alcohols, masked as sulfamate esters, and amines, masked as sulfamides, could engage in photoredox-mediated oxidation to furnish nitrogen-centered radicals that could guide C–H functionalization reactions.
Moreover, our directed technology has been inspired by one of the most reliable and powerful known reactions to guide C–H functionalization reactions: the Hofmann–Löffler–Freytag (HLF) reaction, which uses amines or amides as directing groups. Like many of the most robust radical-mediated technologies to direct the activation of tertiary and secondary centers, the HLF reaction is guided through 1,5-hydrogen-atom transfer (HAT) processes, which proceeds through a kinetically-favorable six-membered ring transition state. By contrast, few reports describe 1,6-HAT with a traceless linker, such as an alcohol masked as a sulfamate ester or an amine masked as a sulfamide, and there are no general strategies to enable masked alcohols or amines to direct functionalization of aliphatic -C(sp3)–H centers. This talk will outline this novel strategy to harness alcohols and amines to replace C–H bonds at -C(sp3)–H centers, which are not generally accessible to directed functionalization. We will demonstrate that C–H abstraction can be robustly coupled with varied functionalization reactions. This talk will highlight the first generalizable synthetic strategy to functionalize -C(sp3)–H bonds based on masked alcohols or amines, to push the boundaries of organic chemistry at a fundamental level and benefits drug discovery.
##### Chemistry
March 1, 2019
Kent 120 | Friday, 1:45 pm
## Jane Wang, Cornell University
#### Insect Flight: from Newton’s law to Neurons
Insects are the first evolved to fly, and to fly is not to fall. How does an insect fly, why does it fly so well, and how can we infer its ‘thoughts’ from its flight dynamics? We have been seeking mechanistic explanations of the complex movement of insect flight. Starting from the Navier-Stokes equations governing the unsteady aerodynamics of flapping flight, we worked to build a theoretical framework for computing flight. This has led to new interpretations and predictions of the functions of an insect’s internal machinery that orchestrate its flight. I will discuss our recent computational and experimental studies of the balancing act of insets: how a dragonfly recovers from falling upside-down and how a fly balances in air. In each case, the physics of flight informs us about the neural feedback circuitries underlying their fast reflexes.
##### Physics Colloquium
February 28, 2019
KPTC 106 | Thursday, 4:00 pm
## Thomas V. Magee, Senior Research Director at Pfizer
#### Discovery of Ketohexokinase (KHK) Inhibitor PF-06835919 for the Treatment of Fatty Liver and Metabolic Disease: From Fragments to Clinical Candidate
##### Chemistry
February 28, 2019
Kent 102 | Thursday, 4:00 pm
## Amy Weeks, University of California, San Francisco
#### New Chemoenzymatic Tools for Dissecting Proteolytic Signaling Pathways
Proteolysis is a key post-translational modification that regulates a wide array of biological processes in human health and disease, including viral infection, cancer progression, organismal development, and neurodegeneration. However, few tools are available to identify proteolysis sites with single amino acid resolution. We have developed next-generation enzymatic tools that enable unbiased capture and sequencing of neo-N termini generated by proteolytic cleavage. These probes are based on subtiligase, a rationally designed variant of the serine protease subtilisin, which catalyzes a ligation reaction between a peptide ester and the N-terminal amine of a peptide or protein. We characterized ligation efficiency for >25,000 enzyme-substrate pairs, leading to the identification of a panel of subtiligase variants that enhance sequence coverage of the cellular N terminome. We have also developed a strategy for spatially-restricted N-terminal tagging that enables global analysis of proteolytic cleavage events at the plasma membrane. Using this technique, we have sequenced proteolytic cleavage sites in >500 human membrane proteins. By combining plasma membrane-targeted subtiligase with pharmacological protease inhibitor treatment, we have begun to define the proteases responsible for specific cleavage events. In combination with its ease of use, the high specificity and resolution of live-cell, subtiligase-catalyzed proteolysis mapping provide a powerful tool for dissecting proteolytic signaling pathways.
##### Chemistry
February 28, 2019
GCIS W301 | Thursday, 11:00 am
## Xiang Cheng, University of Minnesota
#### From Flocking Birds to Swarming Bacteria: A Study of the Dynamics of Active Fluids
Active fluids are a novel class of non-equilibrium complex fluids with examples across a wide range of biological and physical systems such as flocking animals, swarming microorganisms, vibrated granular rods, and suspensions of synthetic colloidal swimmers. Different from familiar non-equilibrium systems where free energy is injected from boundaries, an active fluid is a dispersion of large numbers of self-propelled units, which convert the ambient/internal free energy and maintain non-equilibrium steady states at microscopic scales. Due to this distinct feature, active fluids exhibit fascinating and unusual behaviors unseen in conventional complex fluids. Here, combining high-speed confocal microscopy, holographic imaging, rheological measurements and biochemical engineering, we experimentally investigate the dynamics of active fluids. In particular, we use E. coli suspensions as our model system and illustrate three unique properties of active fluids, i.e., (i) abnormal rheology, (ii) enhanced diffusion of passive tracers and (iii) emergence of collective swarming. Using theoretical tools of fluid mechanics and statistical mechanics, we develop a quantitative understanding of these interesting behaviors. Our study illustrates the general organizing principles of active fluids that can be exploited for designing “smart” fluids with controllable fluid properties. Our results also shed new light on fundamental transport processes in microbiological systems.
##### Computations in Science
February 27, 2019
KPTC 206 | Wednesday, 12:15 pm
## Arjun Yodh, The Department of Physics & Astronomy
#### Soft Matter Potpourri
##### The Tuesday JFI Seminar
February 26, 2019
GCIS W301 | Tuesday, 4:00 pm
## Istvan Racz, University of Warsaw
#### On the use of evolutionary methods in spaces of Euclidean signature
Two examples of physical interest will be presented. Both, contrary to the folklore, demonstrate that evolutionary methods may also play significant role in spaces of Euclidean signature. First, the propagation of the constraints is considered. It is shown that once a clear separation of the evolutionary’ and constraint equations is done, the subsidiary equations satisfied by the constraint expressions form a first order symmetric hyperbolic system regardless whether the ambient Einsteinian space is of Lorentzian or Euclidean signature. Second, the constraints of Einstein's theory of gravity are considered. Since the seminal observations of Lichnerowicz and York these equations are usually referred to as a semilinear elliptic system. It will be shown that–according to the choice of the dependent variables–the constraints may have different characters. In particular, they may take the form of either a parabolic-hyperbolic or a strongly hyperbolic system. Some of the recent developments related to these alternative choices will also be discussed.
##### Relativity Seminar
February 26, 2019
PRC 215 | Tuesday, 11:30 am
## Jessica McIver, Caltech
#### Gravitational wave astrophysics: a new era of discovery
Future gravitational wave observations will provide exciting new insight into key open questions in astrophysics, including the distribution of stellar remnants in the Universe, the evolution of compact binary systems, galaxy formation, the expansion of the Universe, and the explosion mechanism of core-collapse supernovae. I will highlight major outstanding challenges in gravitational wave astrophysics, including extracting transient signals from the noisy data of present and future detectors. I will present new data science techniques to address these challenges and enable future multi-messenger discoveries. I will discuss how the rapidly developing field of gravitational wave astrophysics will shape our understanding of the Universe, including the growing global interferometer network, the next generation of terrestrial interferometers, and the Laser Interferometer Space Antenna (LISA).
##### Relativity Seminar
February 25, 2019
PRC 201 | Monday, 3:00 pm
## Daniel Jafferis, Harvard University
#### Stringy ER=EPR
I will discuss how the correspondence between an entangled state of black holes and the ER wormhole spacetime can be understood as a string duality. In a pure NS background, it is a worldsheet duality involving a condensate of entangled strings. A main ingredient is the Lorentzian prescription for euclidean time winding vertex operators in angular quantization.
February 25, 2019
PRC 201 | Monday, 1:30 pm
## Marc Kamionkowski, Johns Hopkins University
#### Heretical hypotheses in the hunt for dark matter
We have known for a reasonable fraction of a century that most of the matter in the Universe is dark, and for several decades that it cannot be baryonic. The nature of this dark matter has, however, been elusive. The prevailing weakly-interacting massive particle (WIMP) hypothesis that have long been theorists preferred guess faces considerable pressure from an array of null searches, and this has led theorists to consider previously unpalatable alternatives. I will discuss the rise, and possible fall, of an idea that connected LIGO’s discovery of black-hole binaries to dark matter. I will also discuss recent ideas (motivated in part by an intriguing recent experimental result) that involve particles with enhanced couplings to ordinary matter.
##### Physics Colloquium
February 21, 2019
KPTC 106 | Thursday, 4:00 pm
## Greg Voth, Wesleyan University
#### A new view of the dynamics of turbulence from measurements of rotations of particles with complex shapes
Non-spherical particles in turbulent flows are important in a wide range of problems including ice crystals in clouds, fibers in paper-making, marine plankton, and additives for turbulent drag reduction. We have developed experimental methods for precise tracking of the position and orientation of non-spherical particles in intense 3D turbulence. Using 3D printed particles, we can fabricate a wide range of shapes and explore how particle orientation and rotation are affected by particle shape. We find particles are strongly aligned by the turbulence. A simple picture in which particles are aligned by the fluid stretching they experience explains many of the key observations about how particles align and rotate. This same picture sheds new light on some old problems about how vorticity aligns with the strain rate tensor in turbulent flows. It has also allowed us to create a fascinating particle shape which we call a chiral dipole that shows a preferential rotation direction in isotropic turbulent flow.
##### Computations in Science
February 20, 2019
KPTC 206 | Wednesday, 12:15 pm
## Kenneth Schweizer, The Department of Chemistry, University of Illinois at Urbana - Champaign
#### Activated Dynamics in Glass Forming Colloidal, Molecular and Polymeric Liquids: From Structural Relaxation to Functional Materials
Understanding the spectacular slowing down of relaxation and mass transport in glass-forming liquids over 14 or more decades in time remains a grand scientific challenge. Moreover, many advanced materials employ viscous liquids, gels or amorphous solids in applications such as separation membranes, barrier coatings, ion-conductors and functional nanocomposites. I will present an overview of our work the past 5 years on developing a predictive, microscopic, force-based theory for activated relaxation that spans the Arrhenius, dynamic crossover and deeply supercooled regimes of colloidal, molecular and polymeric systems. The theory is based on density fluctuations as the slow variable and the trajectory-level concept of a dynamic free energy that controls intermittent motion. The irreversible re-arrangement event is of a mixed local-nonlocal character involving large amplitude hopping on the cage scale coupled to longer range collective elastic distortion of the surrounding liquid. Connections between thermodynamics, structure, dynamic elasticity and slow relaxation emerge naturally. Chemical complexity is treated based on a physically motivated coarse-graining idea that identifies a small number of key molecular parameters. Quantitative, no-fit-parameter comparisons with experiment will be presented. Generalization to the materials science problem of penetrant diffusion (gas, aromatic molecules) in polymer liquids and glasses, inspired by ideas from interstitial and polaron transport in solids, will also be discussed. Ongoing related theoretical extensions include quiescent and nonequilibrium relaxation and mechanics in attractive glass and gel-forming polymers, colloids and hybrid nanocomposite systems, large dynamical gradients in thin films, emergent anisotropic entanglement constraints and rheology of (bio)polymers, and active matter. Host: Suri Vaikuntanathan at 2-7256 or via email at svaikunt@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
February 19, 2019
GCIS W301 | Tuesday, 4:00 pm
## Ibrahim Cisse, Physics, MIT,
#### Super-resolution imaging of transcription in live mammalian cells
##### Biophysical Dynamics
February 19, 2019
GCIS W301 | Tuesday, 1:00 pm
## Kadanoff seminar: Zohar Nussinov, Washington University in St. Louis
#### Thermalization bounds, long range correlations, and a universal collapse of the viscosities of supercooled liquids
We will derive bounds on the equilibration times in open and closed systems. For open systems, we will find that thermalization times cannot, typically, be shorter than Planck's constant divided by the temperature; a more general (and accurate) relation involving the heat capacities will be explained. For closed systems, the inequalities that we will obtain suggest that non-adiabatically driven systems may display long range correlations. We will explain how these long range correlations appear in certain soluble models in general spatial dimensions and relate these correlations to the geometry of state manifolds. We will describe how experimental measurements of equilibrated systems may be used to infer the properties of eigenstates of many body Hamiltonians. We will then piece these results together to predict the viscosity and relaxation times of supercooled liquids and glasses. These predictions will be compared to the viscosities and dielectric relaxation times of glass formers of all known types. The comparison shows that the viscosities/relaxation times of all known supercooled liquids collapse onto a universal curve with only one (nearly uniform) liquid dependent parameter over 16 decades. The collapsed universal curve is that predicted by the theory.
February 18, 2019
PRC 201 | Monday, 1:30 pm
## Jim Sethna, Cornell University
#### Sloppy models, differential geometry, and the space of model predictions
Models of systems biology, climate change, ecology, complex instruments, and macroeconomics have parameters that are hard or impossible to measure directly. If we fit these unknown parameters, fiddling with them until they agree with past experiments, how much can we trust their predictions? We have found that predictions can be made despite huge uncertainties in the parameters – many parameter combinations are mostly unimportant to the collective behavior. We will use ideas and methods from differential geometry and approximation theory to explain sloppiness as a ‘hyper-ribbon’ structure of the manifold of possible model predictions. We show that physics theories are also sloppy – that sloppiness may be the underlying reason why the world is comprehensible. We will present new methods for visualizing this model manifold for probabilistic systems – such as the space of possible universes as measured by the cosmic microwave background radiation.
##### Physics Colloquium
February 14, 2019
KPTC 106 | Thursday, 4:00 pm
## Andrei Starinets, University of Oxford
#### Analytic structure of hydrodynamic expansions at large finite coupling
Transport properties of liquids and gases in the regime of weak
coupling can be determined from relevant kinetic equations for
particles or quasiparticles, with transport coefficients typically
proportional to the minimal eigenvalue of the linearized kinetic
operator. At strong coupling, the same physical quantities can in
principle be found from dual gravity, where quasinormal spectra enter
as eigenvalues of the linearized Einstein's equations. We discuss the
problem of interpolating between strong and weak coupling using the
results from higher derivative gravity. We also consider the analytic
structure of all-order hydrodynamic expansions arising from the
associated complex analytic spectral curves and discuss how it is
related to the phenomenon of level crossing in quasinormal spectra of
dual black branes.
##### Theory Seminar
February 13, 2019
PRC 201 | Wednesday, 1:30 pm
## Jörn Dunkel, MIT
#### Wrinkles and spaghetti
Buckling and fracture are ubiquitous phenomena that, despite having been studied for centuries, still pose many interesting conceptual and practical challenges. In this talk, I will summarize recent experimental and theoretical work that aims to understand the role of curvature and torsion in wrinkling and fragmentation processes. First, we will show how changes in curvature can induce phase transitions [1] and topological defects [2] in the wrinkling patterns on curved elastic surfaces. In the second part, we will revisit an observation by Feynman who noted that spaghetti appears to fragment into at least three (but hardly ever two) pieces when placed under large bending stresses. Using a combination of experiments, simulations and analytical scaling arguments, we will demonstrate how twist can be used to control binary fracture of brittle elastic rods [3].
[1] Nature Materials 14, 337 (2015) [2] PRL 116: 104301 (2016) [3] PNAS 115: 8665 (2018)
##### Computations in Science
February 13, 2019
KPTC 206 | Wednesday, 12:15 pm
## Wei Xiong, The Department of Chemistry, University California-San Diego
#### Molecular Polaritons – Janus Particles of Photon and Molecules
Molecular vibrational polaritons, half-light, half-matter hybrid quasiparticles, are studied using ultrafast, coherent 2D IR spectroscopy1. Molecular vibrational-polaritons are anticipated to produce new opportunities in the photonic and molecular phenomena. Many of these developments hinge on fundamental understanding of physical properties of molecular vibrational polaritons. Using 2D IR spectroscopy to study vibrational-polaritons, we obtained results that challenge and advance both polariton and spectroscopy fields. These results invoke new developments in theory for the spectroscopy, discover observation of new nonlinear optical effects and unexpected responses from hidden dark states. We expect these results to have significant implications in novel infrared photonic devices, lasing, molecular quantum simulation, as well as new chemistry by tailoring potential energy landscapes.
1.Xiang, B. et al. Two-dimensional infrared spectroscopy of vibrational polaritons. Proc. Natl. Acad. Sci. 115, 4845–4850 (2018) Host: Prof. Andre Tokmakoff, 2-7696 or via email at tokmakoff@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email to bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
February 12, 2019
GCIS W301 | Tuesday, 4:00 pm
#### The Statistical Mechanics of Hydrogen Bonding at the Liquid Water Interface
The dielectric properties of liquid water are determined in large part by the orientational fluctuations of dipolar water molecules. Near a liquid water-vapor interface these orientational fluctuations are constrained and anisotropic, leading to dielectric properties that differ significantly from their bulk values. These differences are fundamental to interface-selective chemical and physical processes but they are generally difficult to predict. We attempt to understand these differences by considering the statistical mechanics of hydrogen bonding at the liquid water interface. Using a mean-field model, we demonstrate that three-body hydrogen bond defects that are stabilized at the interface contribute significantly to determine the interfacial dielectric properties. We utilize this mean field model to study the properties of hydrophilic interfaces and then adapt this perspective to the development of an order parameter that can be used to mapping the dynamic hydration properties of proteins.
##### Chemistry
February 11, 2019
Kent 120 | Monday, 3:45 pm
## Dima Abanin, University of Geneva
#### New quantum many-body states enabled by erodicity breakdown
The experimental advances in synthetic quantum systems, such as ultracold atoms, have enabled researchers to probe quantum thermalization and its breakdown. Thermalization occurs in ergodic systems and “erases” quantum information contained in the initial many-body states. Therefore, to create long-lived quantum states, it is of particular interest to find mechanisms of thermalization breakdown. One way of suppressing thermalization is by introducing strong quenched disorder, which induces many-body localization (MBL) [1]. MBL systems exhibit a new kind of emergent robust integrability and a wealth of novel dynamical phenomena. Surprisingly, MBL systems may also avoid heating under periodic driving, which opens up the possibility of having stable, Floquet-MBL phases with unusual properties. I will discuss one example of such a phase – a two-dimensional Anomalous Floquet Insulator, characterized by fully localized bulk states and chiral, thermalizing edge states [2].
Further, I will argue that MBL may not be the only way to break ergodicity. I will propose another mechanism, “quantum many-body scarring”, which bears a similarity to the well-known phenomenon of quantum scars in few-body chaos, and leads to a weaker form of ergodicity breaking in a many-body system of Rydberg atoms [3]. Quantum scarring gives rise to a set of non-thermal many-body wave functions immersed in the thermalizing background; when the system is initialized in the physical states which have a high overlap with the non-thermal states, it exhibits many-body revivals and lack of thermalization, which have been observed in a recent experiment [4].
February 11, 2019
PRC 201 | Monday, 1:30 pm
## Cathy Drennan, HHMI / MIT
#### Shake, Rattle, & Roll: Capturing Snapshots of Metalloproteins in Actions
Metalloproteins, or proteins that utilize metals to perform their functions, are responsible for a wide range of activities such as the conversion of greenhouse gas carbon dioxide into cellular biomass. To carry out their functions, these proteins often need to be flexible and assume different conformational states, with units of the protein swinging back and forth to enable reactants to bind the protein or products to leave. In this talk, the conformational gymnastics involved in ribonucleotide reduction are considered. Ribonucleotide reductases (RNRs) are metalloenzymes that convert ribonucleotides (the building blocks of RNA) to deoxyribonucleotides (the building blocks of DNA). RNRs are targets for cancer chemotherapies and have been proposed to be candidates for antimicrobial therapies. In this talk, I will describe how my lab has employed biophysical methods to interrogate how RNRs shake, rattle, and roll to accomplish their critical cellular function.
##### Women in Chemistry
February 8, 2019
Kent 120 | Friday, 1:45 pm
## Special Seminar (Particle Phenomenology): Rafaello Tito D'Agnolo, IAS
#### Naturalness in the Sky
Two questions have driven particle physics in the past decades and have a significance that goes beyond the domain of particle physics itself. One surrounds the nature of electroweak symmetry breaking, the other the microscopic origin of dark matter. Both have answers that seem inevitable in their simplicity, but are challenged by experimental results and contain hidden assumptions. I will present new theoretical perspectives on both questions, unveiling unexpected connections with experiment and a clear path to move forward in our understanding. Intriguingly our original expectations might be almost inverted, with dark matter more easily detectable by Earth-based accelerator experiments and electroweak symmetry breaking leaving an imprint in the Cosmic Microwave Background.
##### Theory Seminar
February 8, 2019
PRC 201 | Friday, 1:30 pm
## Dancing nano-particles in a strobe light
Prelude 12:00
Fugue 12:15
##### MRSEC Baglunch
February 8, 2019
GCIS E123 | Friday, 12:00 pm
## Vidya Madhavan, University of Illinois at Urbana–Champaign
#### Signatures of Dispersing 1D Majorana Channels in an Iron-based Superconductor
Dirac discovered that every fundamental particle must also have an anti-particle which has the opposite charge. When particles and anti-particles meet, they annihilate each other, releasing energy. A Majorana fermion is a special type of fundamental particle which is its own antiparticle. The possible realization of these exotic Majorana fermions as quasiparticle excitations in condensed matter physics has created much excitement. Most recent studies have focused on Majorana bound states which can serve as topological qubits. More generally, akin to elementary particles, Majorana fermions can propagate and display linear dispersion. These excitations have not yet been directly observed, and can also be used for quantum information processing. This talk is focused on our recent work in realizing dispersing Majorana modes. I will describe the conditions under which such states can be realized in condensed matter systems and what their signatures are. Finally, I will describe our scanning tunneling experiments of domain walls in the superconductor FeSe0.45Te0.55, which might potentially be first realization of dispersing Majorana states in 1D.
##### Physics Colloquium
February 7, 2019
KPTC 106 | Thursday, 4:00 pm
## Particle Phenomenology Seminar: Masha Baryakhtar
#### Searching for New Physics with Light and Gravitational Waves
Theories beyond the Standard Model often include new, light, feebly interacting particles whose discovery requires novel search strategies. The QCD axion elegantly solves the strong-CP problem of the Standard Model; axion-like-particles, dark photons, and other ultralight bosons can also appear, and are natural dark matter candidates. First, I will discuss my experimental proposal based on photonic materials, in which bosonic dark matter can efficiently convert to detectable single photons. A prototype experiment is underway, and current experimental techniques promise to reach significant new dark matter parameter space in the 0.1 − 10 eV range.
Second, I will show how the process of superradiance, combined with gravitational wave measurements, turns black holes into nature's laboratories for new ultralight boson searches. When a bosonic particle's Compton wavelength is comparable to the horizon size of a black hole, superradiance converts energy and angular momentum from the black hole into exponentially growing hydrogenic' bound states of bosons. I will present constraints on axions and dark photons from black hole spin measurements, and discuss how these systems may source up to thousands of monochromatic gravitational wave signals, enabling LIGO to discover new particles.
February 6, 2019
PRC 201 | Wednesday, 1:30 pm
## Andrej Košmrlj, Princeton University
#### Phase separation in multicomponent liquid mixtures
Multicomponent systems are ubiquitous in nature and industry. While the physics of binary and ternary liquid mixtures is well-understood, the thermodynamic and kinetic properties of N-component mixtures with N>3 have remained relatively unexplored. Inspired by recent examples of intracellular phase separation, we investigate equilibrium phase behavior and morphology of N-component liquid mixtures within the Flory-Huggins theory of regular solutions. In order to determine the number of coexisting phases and their compositions, we developed a new algorithm for constructing complete phase diagrams, based on numerical convexification of the discretized free energy landscape. Together with a Cahn-Hilliard approach for kinetics, we employ this method to study mixtures with N=4 and 5 components. In this talk I will discuss both the coarsening behavior of such systems, as well as the resulting morphologies in 3D. I will also mention how the number of coexisting phases and their compositions can be extracted with Principal Component Analysis (PCA) and K-Means clustering algorithms. Finally, I will discuss how one can reverse engineer the interaction parameters and volume fractions of components in order to achieve a range of desired packing structures, such as nested "Russian dolls" and encapsulated Janus droplets.
##### Computations in Science
February 6, 2019
KPTC 206 | Wednesday, 12:15 pm
## Emily Weiss - The Department of Chemistry, Northwestern University
#### Regio- and Diastereoselective Triplet-Initiated Intermolecular [2+2] Cycloadditions Photocatalyzed by Visible-light-Absorbing Quantum Dots
Tetrasubstituted cyclobutyl structures are precursors to, or core components of, many important bioactive molecules, including prospective drugs. Light-driven [2+2] cycloaddition is the most direct strategy for construction of these structures. Synthetic applications of [2 + 2] photocycloadditions demand high selectivity, not only for specific coupling products, but also for particular stereo- and regioisomers of those products. Achieving selectivities for (i) a particular regioisomer of the coupled product, (ii) a particular diastereomer of the coupled product, and (iii) homo- vs. hetero-coupling within a mixture of reactive olefins still remains a challenge. Here, we discuss the use of colloidal CdSe quantum dots (QDs) as visible light absorbers, triplet exciton donors, and scaffolds to drive homo- (photodimerization) and hetero- (cross coupling) intermolecular [2+2] photocycloadditions of 4-vinylbenzoic acid derivatives, with >90%, switchable regioselectivity and up to 98% diastereoselectivity for the previously minor syn-head-to-head (HH) or syn-head-to-tail (HT) configurations of the adducts. The diasteromeric ratios (d.r.) we achieve are a factor of 5 - 10 higher than those reported with all other triplet sensitizers. Furthermore, the size-tunable triplet energy of the QD enables regioselective hetero-intermolecular couplings through selective sensitization of only one of the reagent olefins. This is the first example of chemistry driven by triplet-triplet energy transfer from a QD. Host: Rachael Farber via email at rgf33@uchicago.edu . If you need assistance, please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu
##### The 1st Tuesday JFI Colloquium
February 5, 2019
GCIS W301 | Tuesday, 4:00 pm
## Tania Baker, Department of Biology, Massachusetts Institute of Technology
#### AAA+ Unfoldase Motors: Regulators of the Proteome as Activators and Destroyer of Protein Function
##### Biophysical Dynamics
February 5, 2019
GCIS W301 | Tuesday, 1:00 pm
## Particle Phenomenology Seminar: Zhen Liu
#### A pathway to the next discovery
The discovery of the Higgs boson at CERN LHC marks the triumph of 50 years of endeavor of high energy physics. The Higgs discovery is only possible with a joint force between experimentalists and theorists in a phenomenological approach. The phenomenological approach and the Higgs boson itself light the pathway towards the next discovery. In this seminar, I will present my recent work that changes the perspective of the LHC main detectors in searches for a challenging class of new physics signals--long-lived particles (LLPs). The new physics signals are well-motivated by broad categories of new physics models, such as supersymmetry and hidden sector models. I will first identify the advantages of the LHC in comparison with other satellite experiments and then present our novel proposals with new triggers and analysis strategies to fully realize such strength, in close connection with the upcoming detector upgrades with precision timing and high granularity detectors. If time permits, I will briefly discuss a few attempts to probe new physics through novel table-top and non-collider experiments along this path. Finally, I will conclude with a broader picture of the pathway to the next discovery.
##### Theory Seminar
February 4, 2019
PRC 201 | Monday, 4:00 pm
## Kharasch Mini Symposium
2:15 pm - Todd Hyster (Princeton) https://www.hysterlab.com/
2:50 pm - Ellen Sletten (UCLA) http://sletten.chem.ucla.edu/
3:25 pm - Mingji Dai (Purdue) http://www.chem.purdue.edu/dai/
4:00 pm - Coffee Break
4:15 pm - Carolyn Bertozzi (Stanford) https://bertozzigroup.stanford.edu/
##### Chemistry
February 4, 2019
GCIS W301 | Monday, 2:15 pm
## Hannes Pichler, Harvard
#### From many-body physics to quantum information with atomic and photonic systems
Quantum many-body systems have unique properties that give rise to fascinating phenomena and potential applications, ranging from exotic phases of matter to new paradigms for information processing and communication. Novel technological developments in quantum optical systems allow to realize and study complex quantum many-body systems in a controlled way. In this talk I want to discuss examples that highlight how the tools available to control quantum optical system can be employed to bring abstract theoretical concepts to the laboratory, but also pose new theoretical challenges in describing such systems. To this end I will first discuss the physics of arrays of individually trapped Rydberg atoms [1] and the associated quantum many-body phenomena. This includes the equilibrium quantum phase diagram in 1D and the universal quantum critical behavior of the various accessible quantum phase transitions, as well as novel non-equilibrium phenomena such as quantum many-body scars. Moreover I show how these systems can be used to naturally encode combinatorial optimization problems and realize quantum annealers [2]. In the second part of this talk I focus on atom-photon interfaces and present a novel way to create highly entangled states of photons by sequentially generating and correlating photons using a single quantum emitter in a waveguide QED setting. I show that employing novel concepts, such as delayed quantum feedback dramatically expands the class of achievable photonic quantum states and allows to generate states that are universal resources for quantum computation with minimal experimental resources [3].
February 4, 2019
PRC 201 | Monday, 1:30 pm
## Special Seminar (Particle Phenomenology): Andrea Thamm, CERN
#### Beyond the Standard Model: Beyond the LHC
After an introduction to the Standard Model (SM) of Particle Physics and the Large Hadron Collider, I discuss some open questions in the SM, focussing in particular on the hierarchy problem and dark matter. I then describe three theoretical directions which address these open problems: heavy new physics, light new physics and models of dark matter. I discuss their motivations, basic setup and the role future colliders could play in their discovery.
##### Theory Seminar
February 1, 2019
PRC 201 | Friday, 1:30 pm
## Peggy Mason, University of Chicago
#### Empathy: The good, the bad, and the ugly
Both the benefits of empathy and the exceptional human qualities needed to exhibit empathy are widely touted in popular culture. Yet rats appear to act out of other-oriented concern, a putative rat analog of empathy, by releasing a fellow rat that is trapped in a tube. This finding shows that empathically driven helping is not restricted to humans and is a process that occurs in other mammals including rats. Empathic helping is proximally driven by the reinforcing consequences of the act of helping which is rewarding so that helping “feels good.” Nonetheless, empathic helping requires both emotional caring and the ability to down-regulate one’s own emotions. Thus, empathic helping is resource-depleting and can be personally costly. This ultimately drives the selective application of empathic helping to in-group members. Finally, rats appear to be more reinforced by releasing a trapped rat than by seeing a trapped rat receive help, suggesting that the act of helping is more rewarding than is the relief of distress. The dissociation between active helping and help received suggests that those who take actions intended to help may be receiving a reward that may be incommensurate with the help that is in fact received. This can lead individuals to falsely perceive their actions as helpful; Such falsehoods can be counterproductive in the context of medicine, leading physicians who actively treat patients to consider a problem resolved when it is not.
##### Physics Colloquium
January 31, 2019
KPTC 106 | Thursday, 4:00 pm
## Kadanoff Special Seminar: Gil Young Cho, Postech
#### Many-Body Invariants for Multipoles in Higher-Order Topological Insulators
We propose many-body invariants for multipoles in higher-order
topological insulators by generalizing Resta's pioneering work on
polarization. The many-body invariants are designed to measure
multipolar charge distribution in a crystalline unit cell, and they
match the localized corner charge originating from the multipoles. We
provide analytic arguments and numerical proof for the invariants.
Furthermore, we show that the many-body invariants faithfully measure
the physical multipole moments even when the nested Wilson loop
approaches fail to do so.
January 31, 2019
PRC 201 | Thursday, 3:30 pm
## Nichole Yunger Halpern, Harvard
#### Quantum steampunk: Quantum information meets thermodynamics
Thermodynamics has shed light on engines, efficiency, and time’s arrow since the Industrial Revolution. But the steam engines that powered the Industrial Revolution were large and classical. Much of today’s technology and experiments are small-scale, quantum, and out-ofequilibrium. Nineteenth-century thermodynamics requires updating for the 21st century. Guidance has come from the mathematical toolkit of quantum information theory. Quantum information theory describes how we can use nonclassical phenomena (entanglement, uncertainty, discreteness, etc.) to process information in ways impossible with classical hardware. Applying quantum information theory to thermodynamics sheds light on fundamental questions (e.g., how does entanglement spread during quantum thermalization?) and suggests new technologies (e.g., quantum engines). I will overview how quantum information theory can modernize thermodynamics for quantum-information-processing technologies, then will focus on thermalization in quantum many-body systems. I call this combination quantum steampunk, after the steampunk genre of literature, art, and cinema that juxtaposes futuristic technologies with 19th-century settings.
January 31, 2019
PRC 201 | Thursday, 1:30 pm
## Bryan Dickinson, University of Chicago
#### Synthetic Biology Approaches to Study and Exploit RNA Regulation
RNA controls information flow through the central dogma and provides unique opportunities for manipulating cells. However, both fundamental understanding and potential translational applications are impeded by a lack of methods to study and exploit the regulation of RNA. Here, I will present three vignettes on our recent protein engineering and molecular evolution efforts focused on understanding and controlling RNA. First, I will show how our engineered RNA polymerase-based biosensors can be exploited as a new method to harness rapid molecular evolution to solve problems in molecular recognition. Second, I will unveil a new evolution system for creating reverse transcriptases that encode RNA modifications in mutations, which allow us to catalog the precise locations of a poorly-understood RNA methylation modification in mammalian cells. Finally, I will present CRISPR/Cas-inspired RNA targeting system (CIRTS), a new protein engineering strategy for constructing programmable RNA regulatory systems, built entirely from human protein parts. Collectively, our technology development focused around RNA regulation will continue to shed light on how mammalian cells function at a fundamental level, while also opening up new opportunities in molecular evolution and epitranscriptomic biotechnology development.
##### Chemistry
January 31, 2019
GCIS W301 | Thursday, 1:15 pm
## Particle Phenomenology Seminar: Simon Knapen
#### Searching for whispers from beyond the standard model
Searches for high energy signatures from beyond the standard model physics have advanced greatly, but a lot of ground remains to be covered for soft, low energy signals. At the LHC, searches for long-lived particles are such an example, as qualitative gains are possible by making full use of the LHCb cavern in the phase II upgrade. In the context of dark matter direct detection, future single-phonon detectors will be sensitive to dark matter with a mass as low as roughly 10 keV. In this regime, the conventional nuclear recoil picture no longer applies and new theoretical tools are needed to correctly compute the scattering rate. I will discuss the prospects for detector concepts based on superfluid helium and polar material targets, where in the latter case we find a large daily modulation of the scattering rate.
##### Theory Seminar
January 30, 2019
PRC 201 | Wednesday, 1:30 pm
## Arthur Barnard, Stanford University
#### New tools for probing classical and quantum nanomaterials
In this seminar, I will discuss two domains of condensed matter physics elucidated by new tools: thermal motion in nanomechanical structures and quantum electron transport in 2D materials. By picking up individual carbon nanotubes and coupling them with electrostatic gates and optical cavities, we directly read-out non-equilibrium dynamics and observe real-time Brownian motion. We reveal surprising spectral dynamics obscured by existing measurement techniques, shedding light on the physics behind the unexpectedly low quality-factor in room temperature carbon nanotube resonators. In the second part of this seminar, I will explain how we control the flow of electrons in graphene. Drawing from intuitions in ballistic transport and light optics, we produce collimated electron beams to quantitatively study angularly dependent phenomena such as Klein tunneling, and elucidate how electrons start to behave like a fluid as they interact more strongly with each other. Using scanning gate microscopy, we image how electrons can follow non-circular cyclotron orbits in graphene-based superlattices.
##### Special JFI Seminar
January 29, 2019
KPTC 206 | Tuesday, 1:30 pm
## Gurol Suel, University of California San Diego
#### The resilience & dichotomy of bacterial existence
##### Biophysical Dynamics
January 29, 2019
GCIS W301 | Tuesday, 12:00 pm
## Jennifer Lippincott-Schwartz, HHMI
#### Peering Into Cells with New Imaging Technologies
Powerful new ways to image the internal structures and complex dynamics of cells are revolutionizing cell biology and bio-medical research. In this talk, I will focus on how emerging fluorescent technologies are increasing spatio-temporal resolution dramatically, permitting simultaneous multispectral imaging of multiple cellular components. Using these tools, it is now possible to begin constructing an “organelle interactome” describing the interrelationships of different cellular organelles as they carry out critical functions. The same tools are also revealing new properties of the cell’s largest organelle, the endoplasmic reticulum, and how disruptions of its normal function due to genetic mutations may contribute to important diseases. Results from these and other technologies that significantly increase spatial resolution in 3-D, including focused ion beam scanning electron microscopy, will be presented.
##### Chemistry
January 28, 2019
Kent 120 | Monday, 4:00 pm
## Hoi Chun Po, MIT
#### Symmetry shortcuts to topological materials
The discovery of topological insulators unveiled a new class of quantum materials whose physical properties are crucially determined by the interplay between symmetries and topology. In this talk, I will discuss how this discovery points to a natural revision of the paradigm of symmetry analysis of weakly correlated materials. Within this new framework, we further develop a general theory for the diagnosis and classification of topological crystalline materials. Our theory integrates theoretical insights originating from the formal classification of topological phases with conventional first-principles calculations, which enables us to efficiently identify thousands of topological materials candidates scattered across the 230 space groups.
January 28, 2019
PRC 201 | Monday, 1:30 pm
## A surface-grafted polymer brush that can flip a nematic fluid, then flip it back.
Let us dine 12:00
Let us opine 12:15
##### MRSEC Baglunch
January 25, 2019
GCIS E123 | Friday, 12:00 pm
## Pablo Jarillo-Herrero, Massachusetts Institute of Technology
#### Magic Angle Graphene: a New Platform for Strongly Correlated Physics
The understanding of strongly-correlated quantum matter has challenged physicists for decades. Such difficulties have stimulated new research paradigms, such as ultra-cold atom lattices for simulating quantum materials. In this talk I will present a new platform to investigate strongly correlatedphysics, based on graphene moiré superlattices. In particular, I will show that when two graphene sheets are twisted by an angle close to the theoretically predicted ‘magic angle’, the resulting flat band structure near the Dirac point gives rise to a strongly-correlated electronic system. These flat bands exhibit half-filling insulating phases at zero magnetic field, which we show to be a correlated insulator arising from electrons localized in the moiré superlattice. Moreover, upon doping, we find electrically tunable superconductivity in this system, with many characteristics similar to high-temperature cuprates superconductivity. These unique properties of magic-angle twisted bilayer graphene open up a new playground for exotic many-body quantum phases in a 2D platform made of pure carbon and without magnetic field. The easy accessibility of the flat bands, the electrical tunability, and the bandwidth tunability though twist angle may pave the way towards more exotic correlated systems, such as quantum spin liquids or correlated topological insulators.
##### Physics Colloquium
January 24, 2019
KPTC 106 | Thursday, 4:00 pm
## Shenshen Wang, Physics & Astronomy, UCLA
#### Discovering generalist solutions in rough & changing landscapes
Evolving systems, be it an antibody repertoire in the face of mutating pathogens or a microbial population exposed to varied antibiotics, respond to ever changing environments through a constant search for adaptive solutions in high-dimensional fitness landscapes. Generalists are robust performers in varied environmental conditions. For better (induction of broad antibody response) or worse (emergence of multi-drug resistance), it is important to be able to discover these adaptive solutions efficiently. Yet, whether and when environmental changes can grant evolutionary advantage to generalists in the long run remains elusive. We introduce a generic landscape framework to study the evolutionary discovery of generalist solutions in slowly changing environments. We show that alternation between rugged fitness landscapes can enhance the propensity to evolve fit generalists, if the landscapes’ topography balances a tradeoff between prevalence, fitness and accessibility, thus demonstrating a general route toward favoring or avoiding generalists via a proper choice of alternating environments. This has important implications for speeding up the generation of broadly neutralizing antibodies or preventing microbes from evolving multi-drug resistance.
##### Biophysical Dynamics
January 24, 2019
GCIS W301 | Thursday, 1:00 pm
## Shmuel Rubinstein, Harvard
#### The physics of crushing and smashing: Cascades and cataclysmic change
Many of the big problems we are facing involve far from equilibrium systems that entail a cataclysmic change. Climate, turbulence and earthquakes, developmental biology, evolution and even aging and death. These phenomena are rare (sometimes occurring only once) and are entirely irreversible. While understanding the physics of such irreversible processes is of both fundamental and practical importance, these problems also pose unique challenges. These challenges, as they manifest in turbulence, were beautifully portrayed by Richardson:
“Big whirls have little whirls that feed on their velocity, and little whirls have lesser whirls and so on to viscosity” Lewis Fry Richardson (1922)
In his short verse, Richardson captures the essence of the turbulent cascade—the conveyance of kinetic energy across scales that underlies the universal dynamics of turbulent flows. Indeed, such conveyance of important physical quantities (energy, stress, frustration and even information) down and up a vast range of scales underlines the dynamics of many systems. The same applies to how a multi-contact frictional interface will form and break or how correlated defect structures determine the strength of a space-rocket, how an intricate network of creases will form when we crumple a thin sheet or when soda can is smashed. The challenge in understanding these systems is in capturing the events as they occur, keeping up with the dynamics on all scales and at all times. Here, I will review our work on several key irreversible system and introduce the new tools we developed to address their unique evolution and discuss the interesting physics we learned.
##### Computations in Science
January 23, 2019
KPTC 206 | Wednesday, 12:15 pm
## Andrew Potter, Honeywell
#### Entanglement dynamics and topology in driven systems
Dramatic advances in AMO systems and ultra-fast optics have assembled a powerful toolbox for coherently and time-dependently manipulating quantum many-body systems, raising enticing prospects for engineering phases of quantum materials and developing quantum information processing technology. However, conventional wisdom dictates that driven many-body systems should follow the principles of eigenstate thermalization, behaving chaotically and rapidly scrambling stored quantum information.
Surprisingly, this trend can be thwarted by artificially disordering isolated systems to selectively freeze dissipative processes that cause thermalization while enabling long-lived quantum coherent dynamics -- a phenomena dubbed many-body localization (MBL). Driving MBL systems enables new non-equilibrium "phases" of matter with stable dynamical quantum properties that are not possible in equilibrium. This talk will describe how developing new tools to characterize the topology and dynamics of quantum entanglement in MBL systems has enabled substantial progress towards systematically classifying these dynamical phases, understanding their signatures, and designing experimental realizations.
January 22, 2019
PRC 201 | Tuesday, 3:00 pm
## Special Seminar (Particle Phenomenology): Prateek Agrawal
#### Axions at the discovery frontier
The next decade will push the boundary of our understanding of fundamental physics in a number of directions, potentially culminating in new discoveries. I will describe how new theoretical insights are pushing this discovery frontier forward. After a broad overview, I will focus on recent progress in axion physics. Axions are compelling candidates for new physics, and traditional axion models predict a relatively narrow target for experiments. I will present novel mechanisms in cosmology and quantum field theory that broaden this parameter space significantly, motivating new experiments. Such an extension of our search strategy may prove crucial to the discovery of axions.
##### Theory Seminar
January 18, 2019
PRC 201 | Friday, 3:00 pm
## Edbert Sie, Stanford
#### How to Control Quantum Materials with Light
A primary goal of modern condensed matter physics is to discover novel quantum phases of matter and engineer their properties. However, conventional approaches using material synthesis or static electromagnetic fields have enabled only a limited exploration of the phase space and associated symmetries at thermal equilibrium. In this talk, I will discuss how we use light to manipulate the space-time symmetries in materials and discover new quantum phenomena that were previously inaccessible. First, I will show that breaking time-reversal symmetry with light enables us to lift the pseudospin degeneracy in monolayer WS2 and selectively tune their energy levels. Here we can completely disentangle the fundamental light-matter interaction into two previously inseparable quantum processes known as the optical Stark effect and the Bloch-Siegert shift. Second, I will show that manipulating inversion symmetry with light allows us to induce topological phase transitions in the Weyl semimetal WTe2 through strain-tuning the lattice. The induced atomic displacements were crystallographically measured using relativistic electron diffraction at sub-picometer length scale and sub-picosecond time scale. These results offer nonequilibrium pathways for designing tunable quantum properties towards terahertz electronics, quantum information, and energy conversion technologies.
##### JFI Special Seminar
January 18, 2019
KPTC 206 | Friday, 1:30 pm
## Odd elasticity: soft engines from active solids
Food eaten 12:00
Thoughts spoken 12:15
##### MRSEC Baglunch
January 18, 2019
GCIS E123 | Friday, 12:00 pm
## Dominic Else, MIT
#### Topological phases of matter with spatial symmetries
A topological phase is a phase of matter characterized by a non-trivial long-wavelength pattern of quantum entanglement in the ground state of a strongly interacting quantum many-body system. I will describe a very general approach to understand such phases in the presence of spatial symmetries such as translation, rotation and reflection (such phases are often referred to as "crystalline topological phases"). There are several complementary ways to think about this approach, one of which is based on a systematization of the notion of gauging a spatial symmetry; I will also outline a more concrete geometrical picture in terms of "defect networks". Finally, I will show how this new understanding of crystalline topological phases allows for the unification and generalization of results such as the Lieb-Schultz-Mattis theorem for quantum spin systems, which can be reinterpreted as a kind of UV-IR anomaly matching in the presence of a spatial symmetry.
January 17, 2019
PRC 201 | Thursday, 1:30 pm
## Special Seminar (Particle Phenomenology): Yue Zhang
#### New Dark Matter Signals in Neutrino Detectors
Understanding the nature of dark matter is a question lying at the heart of particle physics and cosmology. I will discuss the potential leading role of using our current and near future neutrino experiments in search for a class of dark matter candidates, and a number of associated new signals. With the new generation of neutrino detectors in the coming decade, many ideas can be tested. The complementarity with the other approaches will also be discussed in this talk.
##### Theory Seminar
January 16, 2019
PRC 201 | Wednesday, 2:00 pm
## Eric Spanton, UC Santa Barbara
#### Fractional Chern insulators in graphene heterostructures
Graphene is a highly tunable platform for studying the effects of electron-electron interactions in two dimensions. Encapsulation with a 2D dielectric (hexagonal boron nitride, hBN), and more recently the use of single-crystal graphite top and bottom gates have decreased the electronic disorder to a level suitable for the to study fragile and exotic strongly correlated states. Additionally, control of twist angle between closely-matched crystal lattices allows for unique control of electronic properties, leading to the “Hofstadter butterfly” and more recently unconventional superconductivity. I will describe the first experimental observation of a class of states in nearly aligned hBN/graphene heterostructures called fractional Chern insulators, a close relative of the fractional quantum Hall effect. In graphene, fractional Chern insulators arise in the presence of electron-electron interactions, high magnetic fields, and a long wavelength ‘moire’ superlattice formed by close alignment between hBN and graphene lattices. Twist angle between graphene and hBN, electron density and perpendicular electric field tune the underlying single-particle bands to realize different types of fractional Chern insulators. The realization of fractional Chern insulators opens the door for the study of novel topological phase transitions and exotic defect states.
##### JFI Special Seminar
January 16, 2019
KPTC 206 | Wednesday, 1:30 pm
## Margaret Gardel, University of Chicago
#### Controlling the Shape of Cells within Tissue
Mature epithelial tissues have distinct cellular architecture, which is maintained despite externally applied forces, wounding, and cell division or death. Here we investigate how a model tissue develops and maintains cellular structure by quantifying single cell dynamics and cell shape in newly formed monolayers of MDCK cells. Cells initially aggregate through a process resembling wound healing into a confluent monolayer with elongated cells that remain motile. After formation, individual monolayers evolve over time to reach a similar final state with more hexagonal cell shapes and arrested dynamics, resembling mature epithelial tissues. By quantifying cell trajectories, we observe glassy dynamics controlled by cell shape, which have been previously predicted by vertex models. On substrates of different stiffness, monolayers form and evolve with different cell number density but the same relationship between cell shape and speed suggesting that the dynamics are density independent. We find when inhibiting several regulators of the actin cytoskeleton that cell speed and shape remain correlated but the correlation is shifted toward more elongated cell shapes. The magnitude of this shift differs for each inhibitor but velocity correlation length decreases proportionately to the change in final cell shape. We show that these results can be recapitulated in vertex models which incorporate polarization coupling between neighboring cells. Our results demonstrate that multicellular coordination of cell motility plays an important role in regulation of cell shape and determination of final tissue structure.
##### Computations in Science
January 16, 2019
KPTC 206 | Wednesday, 12:15 pm
## Ke Xu, Department of Chemistry, University of California-Berkeley
#### Multifunctional & Multidimensional Super-resolution Microscopy
Recent advances in super-resolution fluorescence microscopy have led to ~10 nm spatial resolution and exciting new biology. We are developing new approaches to advance beyond the structural (shape) information offered by existing super-resolution methods, and reveal multidimensional information of intracellular functional parameters, including chemical polarity, diffusivity, and reactivity, with nanoscale resolution and single-molecule sensitivity. By adding remarkably rich functional dimensions to the already powerful super-resolution microscopy, we thus open up new ways to reveal fascinating local heterogeneities in live cells. Host: Bozhi Tian, 2-8749 or via email at btian@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
January 15, 2019
GCIS W301 | Tuesday, 4:00 pm
## Ryo Nakano, Nagoya University
#### Study on Olefin Polymerization Toward Utilization of Carbon Dioxide
Although carbon dioxide has attracted broad interest as a renewable carbon feedstock, its favorable nature as a carbon source is inextricably linked to its inherent inertness. Therefore, to overcome the endothermic penalty of carbon-dioxide incorporation, a transformation of carbon dioxide under mild conditions requires a thermodynamic driving force from coupling partners. In this context, copolymerization of carbon dioxide and olefin, which is the largest class of organic chemicals produced today, will be a suitable reaction exploiting the prospective features of carbon dioxide as a C1 bulk feedstock.
From a theoretical consideration on the thermodynamics of olefin/carbon dioxide copolymerization, stepwise and direct copolymerization were investigated. The stepwise approach was successfully demonstrated in butadiene/carbon dioxide copolymerization via a lactone intermediate, as the first example to prepare high-molecular-weight copolymer starting from a bulk alkene and carbon dioxide. For further expansion of the scope of olefins toward monoenes, namely ethylene and propylene, palladium catalyst bearing an NHC-based bidentate ligand (IzQO) was designed rationally. While the CO2/monoene copolymerization was not accomplished, the palladium/IzQO complexes exhibited unique catalytic activities for propylene/polar monomer copolymerization and ethylene/1,1-disubstituted olefin copolymerization.
##### Chemistry
January 14, 2019
Kent 120 | Monday, 3:00 pm
## Why do my flying lego blocks spin and make hinges?
Eatin' time 12:00
Thinkin' time 12:15
##### MRSEC Baglunch
January 11, 2019
GCIS E123 | Friday, 12:00 pm
## Reina Maruyama, Yale University
#### Testing DAMA's Long-standing Claim for Dark Matter Detection
Astrophysical observations give overwhelming evidence for the existence of dark matter. Several theoretical particles have been proposed as dark matter candidates, including weakly interacting massive particles (WIMPs), axions, and more recently their much lighter counterparts, however there has not yet been a definitive detection of dark matter. One group, the DAMA collaboration, has asserted for years that they observe a dark matter-induced annual modulation signal in their NaI(Tl)-based detectors. Their observations seem to be inconsistent with those from other direct detection dark matter experiments under most assumptions of dark matter. In this talk I will describe the current status of the debate and the world-wide experimental effort to test this extraordinary claim. I will report the recent results from the COSINE-100 experiment and our progress toward resolving the current stalemate in the field.
##### Physics Colloquium
January 10, 2019
KPTC 106 | Thursday, 4:00 pm
## Andrew Feguson, Institute for Molecular Engineering, The Univeristy of Chicago
#### Machine Learning Collective Variable Discovery in Colloidal Assembly and Protein Folding
Data-driven modeling and machine learning have opened new paradigms and opportunities in the understanding and design of soft and biological materials. The automated discovery of emergent collective variables within high-dimensional computational and experimental data sets provides a means
to understand and predict materials behavior and engineer properties and function. I will describe our recent work in the use of two machine learning techniques for collective variable discovery within molecular simulation – nonlinear manifold learning using diffusion maps, and nonlinear dimensionality reduction using autoencoding neural networks (“autoencoders”). First, I will describe our applications of graph matching and diffusion maps to determine low-dimensional assembly landscapes for self-assembling patchy colloids. These landscapes connect colloid architecture and prevailing conditions with
emergent assembly behavior, and we use them to perform inverse building block design by rationally sculpting the landscape to engineer the stability and accessibility of desired aggregates. Second, I will describe our use of autoencoders to perform automated discovery of collective variables in proteinfolding. We interleave deep learning variable discovery and enhanced sampling directly within the discovered variables to perform simultaneous on-the-fly variable discovery and accelerated sampling of protein folding funnels.Host: Suri Vaikuntunathan, 2-7256 or via email to svaikunt@uchicago.edu. Persons with a disability who need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
January 8, 2019
GCIS W301 | Tuesday, 4:00 pm
## Su-Yang Xu, MIT
#### Topology and Geometry in Quantum Materials
Finding new phases of matter and understanding their physics are primary goals of condensed matter physics. Advances in quantum physics can in turn breed novel technologies, benefiting our society. Topological states are new phases of matter characterized by a nonzero topological invariant. They can support protected surface/edge states, realize elusive particles, and respond to electric and magnetic fields in unconventional ways. On a more fundamental level, topological physics arise from the geometric properties of the quantum wavefunction, i.e., quantum geometry, which include Berry curvature, Berry connection, quantum metric, etc.
First, I will describe how we search for material platforms that support new topology and quantum geometry. In particular, I will focus on our theoretical predictions and experimental observations of the first Weyl fermion semimetal state in TaAs and later the topological chiral crystal state in RhSi. Second, I will describe nonlinear optoelectronic and transport measurements that can probe Berry curvature and interaction in a symmetry-sensitive way. Specifically, I will show how we use mid-infrared photocurrents to probe the chirality of Weyl fermions and other Berry curvature physics in 3D and 2D topological materials. I will also show our photocurrent detection of a novel electronic instability, the gyrotropic order, in the correlated semimetal TiSe2, and how we use circularly polarized light to manipulate such order via quantum geometrical responses. In the final part, I show how current works suggest ample new exciting possibilities to discover fundamental physics in topological condensed matter physics, which also offers pathways to quantum sensing, information and computation technologies.
##### Special JFI Seminar
January 8, 2019
KPTC 206 | Tuesday, 1:30 pm
## Marc-André Légaré, University of Würzburg
#### Main-Group Metallomimetics: Strategies for Metal-Free Catalysis and Small-Molecule Activation
The importance of transition metals (TMs) in modern catalysis cannot be overstated. TM-based catalysts enable processes that are of tremendous human and economic importance; they have innumerable applications in many industrial sectors. However, the toxicity, price and natural scarcity of many elements that are used in TM catalysis fuel an interest for the development of metal-free catalysts based on the main-group elements.
However, contrary to many catalytically-active TM complexes, classical main-group compounds do not possess the combination of empty and filled orbitals that is crucial for the complex electronic processes involved in the elemental steps of catalytic cycles. The development of catalysts based on the p-block elements thus requires the design and application of unique strategies. In this seminar, I will present two approaches for the metallomimetic application of boron compounds to small-molecule activation, to reduction processes, and to organic functionalization reactions. I will discuss systems that involve the combination of single and multiple active sites in order to mimic the electronic environment of TM complexes. Similarities and differences in the reactivity of main-group compounds and TM complexes will also be highlighted.
##### Chemistry
January 7, 2019
Kent 102 | Monday, 3:00 pm
## Katharine Diehl, Princeton University
#### Illuminating Epigenetic Mechanisms in Cancer with Designer Chromatin
In the eukaryotic cell, the genome is packaged in a nucleoprotein complex known as chromatin. Histones comprise the protein component of chromatin and serve as a hot bed for post-translational modifications (PTMs) that dynamically modulate local chromatin state to control DNA transcription, replication, and repair. Importantly, cancer cells depend on altered epigenetic landscapes to drive genomic instability and aberrant gene expression. In order to precisely target epigenetic misregulation in disease, it is critical to elucidate the mechanistic basis of how specific chromatin states are established and maintained. This talk will discuss how synthetic access to defined chromatin substrates enables the discovery of mechanisms by which histone PTMs modulate the genome. In the first part, a DNA-barcoded mononucleosome library was used to profile the activity of crucial DNA damage sensor enzymes (PARP1/2), uncovering new regulatory features in the DNA damage response. In the second part, designer chromatin substrates were used to investigate an oncogenic histone mutant, revealing details of how this mutation leads to deleterious epigenetic reprogramming. These efforts demonstrate how protein chemistry can be integrated with biochemical, biophysical, and genetic tools to facilitate analysis of the physicochemical principles underlying epigenetic dysregulation.
##### Chemistry
January 4, 2019
Kent 102 | Friday, 1:15 pm
## winner take all: from neural networks to nucleation
Gala reception 12:00
Gala discussion 12:15
##### MRSEC Baglunch
January 4, 2019
GCIS E123 | Friday, 12:00 pm
## Paola Ruggiero (SISSA and INFN)
#### Conformal field theory for inhomogeneous systems: the example of a breathing Tonks-Girardeau gas
Conformal field theory (CFT) has been extremely
successful in describing universal effects in critical one-dimensional
(1D) systems, in situations in which the bulk is uniform. However, in
many experimental contexts, such as quantum gases in trapping
potentials and in several out-of-equilibrium situations, systems are
strongly inhomogeneous. Recently it was shown that the CFT methods can
be extended to deal with such 1D situations: the system's
inhomogeneity gets reabsorbed in the parameters of the theory, such as
the metric, resulting in a CFT in curved space. Here in particular we
make use of CFT in curved spacetime to deal with the
out-of-equilibrium situation generated by a frequency quench in a
Tonks-Girardeau gas in a harmonic trap. We show compatibility with
known exact result and use this new method to compute new quantities,
not explicitly known by means of other methods, such as the dynamical
fermionic propagator and the one particle density matrix at different
times.
December 14, 2018
PRC 201 | Friday, 1:30 pm
## Sebastian Huber, Department of Physics, ETH Zürich
#### Axial Magnetic Fields in Weyl Systems
While acoustic or elastic waves can easily be forced into behaving like electrons on a lattice, it is much harder to find analogies to the physics induced by a magnetic field. In my talk I will show how one can achieve exactly this by using phonons that are described by the relativistic Weyl equation. We engineer an acoustic crystal, where the low energy physics around a chosen frequency resembles the one of a Weyl particle in a magnetic field. We observe the resulting chiral Landau levels and I will present theoretical studies of non-local orbits in the presence of this synthetic magnetic field. Host: Vincenzo Vitelli, 4-8829 or via email to vitelli@uchicago.edu. Persons with a disability who need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The JFI Theory Seminar
December 13, 2018
KPTC 206 | Thursday, 12:15 pm
## Dianne J. Xiao, Stanford University
Hydrocarbons are cheap and abundant feedstocks readily derived from both fossil fuels and emerging renewable resources. Despite their abundance, hydrocarbons have limited applications in chemical synthesis due to the inertness of C–H bonds towards both homolytic and heterolytic bond cleavage. I will share two very different approaches to the selective functionalization of simple hydrocarbons that address these challenges. First, I will highlight a bio-inspired approach to achieve selective alkane hydroxylation using iron-based metal–organic frameworks. The critical influence of both primary and secondary coordination sphere elements on catalyst reactivity, selectivity, and stability will be detailed. Second, I will describe the identification and characterization of a simple heterogeneous base catalyst that converts aromatic hydrocarbons, CO2, and methanol into the corresponding aromatic esters at elevated temperatures. The transformation occurs via a two-step, semi-continuous cycle, and represents the first hydrocarbon CO2 insertion process that does not consume any energy-intensive stoichiometric reagents
##### Molecular Engineering
December 13, 2018
ERC 201B | Thursday, 10:00 am
## Chiara Daraio, Caltech
#### Tunable, On-chip Phononic Devices Operating at MHz Frequencies
Nanoelectromechanical systems (NEMS) that operate in the megahertz (MHz) regime allow energy transducibility between different physical domains. For example, they convert optical or electrical signals into mechanical motions and vice versa. This coupling of different physical quantities leads to frequency-tunable NEMS resonators via electromechanical non-linearities. In this talk, I will describe one- and two-dimensional, non-linear, nanoelectromechanical lattices (NEML) with active control of the frequency band dispersion in the radio-frequency domain (10–30 MHz). Our NEMLs consist of a periodic arrangement of mechanically coupled, free-standing nanomembranes with circular clamped boundaries. This design forms a flexural phononic crystal with a wide and well-defined bandgap. The application of a d.c. gate voltage creates voltage-dependent on-site potentials, which can significantly shift the frequency bands of the device. Additionally, I will discuss the experimental realization of topological nanoelectromechanical metamaterials with protected edge states. These on-chip integrated acoustic components could be used in unidirectional waveguides and compact delay lines for high-frequency signal-processing applications.
##### Computations in Science
December 12, 2018
KPTC 206 | Wednesday, 12:15 pm
## Prof. Sean T. Roberts, Department of Chemistry, University of Texas-Austin
#### Manipulating Energy and Spin for Photon Up- and Down-conversion
The negligible spin-orbit coupling in many organic molecules creates opportunities to alter the energy of excited electrons by manipulating their spin. In particular, molecules with a large exchange splitting have garnered interest due to their potential to undergo singlet fission (SF), a process where a molecule in a high-energy spin-singlet state shares its energy with a neighbor, placing both in a low-energy spin-triplet state. When incorporated into photovoltaic and photocatalytic systems, SF can offset losses from carrier thermalization, which account for ~50% of the energy dissipated by these technologies. Likewise, compounds that undergo SF’s inverse, triplet fusion (TF), can be paired with infrared absorbers to create structures that upconvert infrared into visible light. In this presentation, I will review our group’s efforts to create organic:inorganic structures that use SF and TF for improved light harvesting and photon upconversion. Host: Andrei Tokmakoff, 4-7696 or via email at tokmakoff@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
December 11, 2018
GCIS W301 | Tuesday, 4:00 pm
## Joaquín Rodríguez-López, University of Illinois at Urbana-Champaign
#### Elucidating Electrochemical Energy Materials Through Versatile Electrochemistry
In this seminar, I will discuss how new polymeric and low-dimensional materials, as well as an expanded electroanalytical toolbox for understanding interfaces, are allowing us to discover new synergies at the nano and mesoscale for emerging battery technologies. I will describe in detail one system where nano-scale heterogeneity has an impact on macro-scale performance: novel redox active polymers (RAPs) for size-selective flow batteries. Highly soluble RAPs are new players in redox flow technologies, and as part of our collaboration with the Joint Center for Research Energy Storage (JCESR), we are exploring the opportunities that macromolecular design offers for tuning their electrochemical performance. These investigations span across several areas of knowledge, from the interrogation of individual polymer particles, to the elucidation of new redox polyelectrolyte dynamics, and to the evaluation of flow battery performance. Finally, I will describe how we have applied insightful interfacial design and analysis to better understand other energy technologies such as ion batteries and electrocatalysts. Fundamental pursuit of electrode design principles have led us to investigate intercalation processes in low dimensional materials, and the use of ultra-thin electrodes for creating new charge transfer strategies on hetero-structures.
##### Molecular Engineering
December 11, 2018
ERC 201B | Tuesday, 10:00 am
## C. Rose Kennedy, Princeton University
#### Leveraging Mechanistic Insight to Enable Catalyst-Controlled Chemo-, Regio- & Stereoselective C–C Bond Formation
Mechanistic elucidation provides potent tools for enabling the design of efficient and selective catalytic transformations. Examples of mechanism-guided method development, drawing from the complementary strengths of ion-pairing organocatalysis and organometallic chemistry to achieve selective C–C bond formation, are described.
In the former case, combined experimental and computational analyses delineating the mechanisms of representative amido-thiourea-catalyzed transformations are discussed. Insights from these studies enabled (i) the rational design of linked bis-thioureas that impart enhanced efficiency for enantioselective anion-abstraction catalysis and (ii) the introduction of a synergistic ion-binding strategy for asymmetric catalysis of transformations involving electronically diffuse transition structures.
In the latter case, iron complexes bearing redox-active ligands are explored as catalysts for hydrovinylation and cycloaddition reactions proceeding through the intermediacy of metallacycles. Mechanistically informed ligand designs are leveraged to control metallacycle formation and fate to upgrade olefinic coupling partners with control of chemo-, regio-, and diastereoselectivity. Applications of the resulting cycloadducts for the synthesis of fuels, polymers, and fine chemicals are discussed.
##### Chemistry
December 10, 2018
Kent 102 | Monday, 1:15 pm
## Physics with A Bang! Holiday Lecture and JFI Open House
Students, families, teachers and especially the curious are invited to attend our annual Holiday Lecture and Open House. See fast, loud, surprising and beautiful physics demos performed by Profs. Heinrich Jaeger and Sidney Nagel. Talk to scientists about their latest discoveries. Participate in hands-on activities related to their research.
Saturday, December 8th, 2018
Kersten Physics Teaching Center
5720 S. Ellis Ave., Chicago, IL
Lecture repeated at 11am and 2pm
Open House and Demo Alley from 12pm-4pm
Lab Tours in the afternoon
Doors for the Lectures open 30 minutes before each show. Please note: there will be no online registrations, and will be a first to arrive, first ticketed event. We do not guarantee availibility of seating, but shows will also be streamed live to alternate venues. Those needing special assistance, please send an email to ecs@uchicago.edu.
##### Special JFI Seminar
December 8, 2018
KPTC 106 | Saturday, 11:00 am
## Junichiro Yamaguchi, Waseda University
#### Making Bonds by Breaking Bonds: An Unconventional Approach to Making Molecules
##### Chemistry
December 7, 2018
Kent 120 | Friday, 1:15 pm
## Abigail Vieregg, University of Chicago
#### Discovering the Highest Energy Astrophysical Neutrinos Using a Radio Phased Array
Ultra-high energy neutrino astronomy sits at the boundary between particle physics and astrophysics. The detection of high energy neutrinos is an important step toward understanding the most energetic cosmic accelerators and would enable tests of fundamental physics at energy scales that cannot easily be achieved on Earth. IceCube has detected astrophysical neutrinos at lower energies, but the best limit to date on the flux of ultra-high energy neutrinos comes from the ANITA experiment, a NASA balloon-borne radio telescope designed to detect coherent radio Cherenkov emission from cosmogenic ultra-high energy neutrinos. The future of high energy neutrino detection lies with ground-based radio arrays, which would represent a large leap in sensitivity. I will discuss the demonstrated performance of a new radio phased array design that we have implemented on the ARA experiment at the South Pole and on the new BEACON experiment on White Mountain in California. The radio phased array has improved sensitivity to high energy cosmic particles and will push the energy threshold for radio detection down to overlap with the energy range probed by IceCube.
##### Physics Colloquium
December 6, 2018
KPTC 106 | Thursday, 4:00 pm
## Katlyn K. Meier, Stanford University
#### Spectroscopic Characterization of Unique Iron and Copper Active Sites in Biology
##### Chemistry
December 6, 2018
Kent 120 | Thursday, 12:30 pm
## Diana Qiu, University of California, Berkeley
#### Excitons in Flatland: Exploring and Manipulating Many-body Effects on the Optical Excitations in Quasi-2D Materials
Since the isolation of graphene in 2004, atomically-thin quasi-two-dimensional (quasi-2D) materials have proven to be an exciting platform for both applications in novel devices and exploring fundamental phenomena arising in low dimensions. This interesting low-dimensional behavior is a consequence of the combined effects of quantum confinement and stronger electron-electron correlations due to reduced screening. In this talk, I will discuss how the low-energy optical excitations (excitons) in quasi-2D materials, such as monolayer transition metal dichalcogenides and few-layer black phosphorus, differ from typical bulk materials. In particular, quasi-2D materials are host to a wide-variety of strongly-bound excitons with unusual excitation spectra and massless dispersion. The presence of these excitons can greatly enhance both linear and nonlinear response compared to bulk materials, making them ideal candidates for applications in optoelectronics, energy harvesting, and energy conversion. Moreover, due to enhanced correlations and environmental sensitivity, the electronic and optical properties of these materials can be easily tuned. I will discuss how substrate engineering, stacking of different layers, and the introduction or removal of defects can be used to tune the band gaps and optical selection rules in quasi-2D materials.
##### Molecular Engineering
December 6, 2018
ERC 201B | Thursday, 10:00 am
## Lou Charkoudian, Haverford College
#### Capturing Transient Interactions of Proteins Involved in Natural Product Biosynthesis
How do microorganisms produce chemically diverse and structurally complex molecules? How can humans harness this technology to better human health and the environment? These questions inspire our lab to study acyl carrier proteins (ACPs), which serve as central hubs in polyketide and fatty acid biosynthetic pathways. ACPs are notoriously challenging to study because the fast motions of the ACP phosphopantetheine (Ppant) arm make its conformational dynamics difficult to capture using traditional spectroscopic approaches. In this talk, I will present how the synthetic modification of the terminal thiol of the ACP Ppant arm can transform the ACP reactive site into a vibrational spectroscopic probe that can report on mechanistically-relevant movements of the ACP. I will share stories about how we leverage Ppant probes to resolve conformational dynamics on the picosecond time scale and visualize ACP complex formation with functional catalytic partners. We anticipate that these methods will be valuable in future structural and biosynthetic engineering studies because our approach is generalizable, practical, and scalable. Our studies combine concepts and techniques spanning biochemistry, organic chemistry, bioinformatics, and physical chemistry, and therefore I hope this talk will be of interest to a broad audience.
##### Chemistry
December 5, 2018
GCIS W301 | Wednesday, 1:00 pm
## David Lubensky, University of Michigan
#### Organ size, inflationary embryology, and the statistical physics of tissue growth
One of the enduring mysteries of biology is how organs know to stop growing at the correct size and how those sizes are coordinated so that the animal retains the correct proportions. Here, we discuss several studies that in different ways address the precision with which organ size can be controlled. We first show that there are severe limits to the coordination of the sizes of left and right organs (like the left and right wings of a fruit fly) by chemical signals, suggesting that organ size is set primarily autonomously. We then consider the noisy dynamics of the growth of individuals tissues in the presence of various feedback laws. We find that only certain forms of mechanical feedback can specify a unique organ size. We also show that, even in the simplest, homogeneous case, stochastic growth of an elastic tissue has unexpectedly rich behavior: For example, it exhibits power law correlation functions, reminiscent of those seen in cosmological models, and soft modes that allow for diffusive growth of labelled clones of cells.
##### Computations in Science
December 5, 2018
KPTC 206 | Wednesday, 12:15 pm
## Weixin Tang, Harvard University
#### From Peptide Antibiotics to CRISPR-mediated Synthetic Memories: Tools from the Microbial Arsenal
##### Chemistry
December 5, 2018
GCIS W301 | Wednesday, 11:00 am
## Prof. Christophe Delerue, IEMN- CNRS, Paris
#### Localized Surface Plasmon Resonance in Doped Semiconductor Nanocrystals
Nanocrystals of heavily-doped semiconductors have recently emerged as very promising materials for plasmonics. In contrast to nanocrystals of noble metals, their Localized Surface Plasmon Resonance (LSPR) can be easily tuned in energy by controlling the carrier concentration through doping. In addition, due to the low concentration of carriers compared to metals, the LSPR can be
extended to infrared and near-infrared ranges. Recent experimental studies have demonstrated the existence of LSPR in doped nanocrystals of Si and different types of oxides (ZnO, SnO2, In2O3). However, the physics of the LSPR in these nanocrystals is not totally understood. In the first part of my talk, I will give of general overview of the field of doped semiconductor nanocrystal
plasmonics. In the second part, I will review theoretical studies that we have performed in order to address fundamental issues which are still highly debated. The evolution with doping concentration of the optical processes from single-electron to many-electron transitions will be described. The conditions required for the emergence of collective modes will be discussed. The results of atomistic calculations will be compared with those of more classical approaches. The role of the quantum confinement and the influence of the dopant potential and location will be discussed. The intrinsic mechanisms at the origin of plasmon damping in doped nanocrystals will be analyzed. The results confirm that doped nanocrystals are very promising for the development of IR plasmonics.Host: Philippe Guyot-Sionnest,2-7161 or via email at pgs@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The 1st Tuesday JFI Colloquium
December 4, 2018
GCIS W301 | Tuesday, 4:00 pm
## Srimoyee Sen, University of Washington
#### Anyonic particle-vortex statistics and the nature of dense QCD
I discuss the recent theoretical observation of Z_3 -valued particle-vortex braiding phases in high density QCD and its implications for higgs-confinement complementarity. As a consequence of the braiding phases, certain mesonic and baryonic excitations, in the presence of a superfluid vortex, have orbital angular momentum quantized in units of 1/3. Such non-local topological features can distinguish phases whose realizations of global symmetries, as probed by local order parameters, are identical. If Z_3 braiding phases and angular momentum fractionalization are absent in lower density hadronic matter, as is widely expected, then the quark matter and hadronic matter regimes of dense QCD must be separated by at least one phase transition
December 4, 2018
PRC 201 | Tuesday, 1:30 pm
## Mark Levin, Harvard University
#### Catalytic Manipulation of Reactivity and Selectivity at High-Valent Nuclei
This presentation will examine aspects of reactivity and selectivity discovered through the exploration of the chemistry of high-valent nuclei [Au(III), Pt(IV), and I(III)]. The first part concerns two examples wherein transition metals are examined as substrates for catalytic reactions rather than in their traditional role as catalysts. Operating from this perspective, supramolecular catalysis of C(sp3)-C(sp3) reductive elimination and organoborane catalyzed C(sp3)-CF3 reductive elimination will be discussed, with the latter applied to [18F]-radiotrifluoromethylation. The second section will continue the focus on fluorination through the development of a new aryliodine catalyst for enantioselective olefin difluorination, exploring structural features that improve catalyst robustness and selectivity and enabling the preparation of chiral fluorinated building blocks.
##### Chemistry
December 3, 2018
Kent 120 | Monday, 1:15 pm
## Brad P. Carrow, Princeton University
#### Leveraging Polarizability and Electrophilicity in Catalysts for Challenging Coupling Reactions
A general approach by our group for the development of new catalytic synthetic methods that occur with higher efficiency and selectivity, use simpler reagents, and proceed with lower energy demand involves new ancillary ligand design coupled with fundamental studies of how metal-ligand bonding dictates catalytic reactivity. In this context, the presentation will focus on our recent efforts to discover new phosphorus- and sulfur-based ligands and associated metal catalysts that manifest special properties from seemingly "weak" interactions, for instance London dispersion. Two case studies will be discussed that exemplify such effects and emphasize many lessons yet to be learned about how structure controls reactivity in synthetic catalysts. In one case, a new transmetalation mechanism can be triggered in reactions of low-coordinate Pd complexes possessing polarizable diamondoid substituents, which enables smooth coupling catalysis even with historically unstable organoboron reagents. Studies of oxidative dehydrogenative coupling reactions will also showcase evidence for a C−H bond activation mechanism, termed electrophilic CMD or "eCMD", which has characteristics distinct from established SEAr and concerted metalation-deprotonation (CMD) pathways for C−H functionalization. Transition state analyses suggest this reaction pathway could be a general class of C−H activation manifested by many other transition metal catalysts, and selection rules have been identified for predicting what catalyst structures manifest either classic CMD or eCMD, which occur with unique substrate preferences and selectivity.
##### Chemistry
November 30, 2018
Kent 120 | Friday, 1:15 pm
## Junqi Li, Yale University
#### From Automated Small Molecule Synthesis to Understanding Chiral Phosporic Acid Catalysis
Efforts to discover and optimize new small molecule function are often impeded by limitations in synthetic access to small molecules. This is because small molecule syntheses typically employ strategies and purification methods that are highly customized for each target. Furthermore, the molecular interactions between the catalyst and substrate are often not understood in catalyst-controlled selective reactions, thus impeding the design of new and more selective catalysts. In this seminar, an iterative cross-coupling strategy that enables the systematized and automated synthesis of different types of small molecules will be presented. The second part of the talk will discuss enantio- and site-selective reactions catalyzed by chiral phosphoric acids with a focus on understanding key catalyst-substrate interactions.
##### Chemistry
November 29, 2018
Kent 120 | Thursday, 1:15 pm
## Andrei Parnachev
#### Regge limit in Holographic Conformal Field Theories
We will discuss the Regge limit of correlators in holographic CFTs and its
physical implications. Examples include constraints on the three-point couplings of the stress tensor
and the relation between heavy states in CFT and black holes in dual gravity.
##### Theory Seminar
November 28, 2018
PRC 201 | Wednesday, 1:30 pm
## Felice Frankel
#### More Than Pretty Pictures
Graphics, images and figures — visual representations of scientific data and concepts — are critical components of science and engineering research. They communicate in ways that words cannot. They can clarify or strengthen an argument and spur interest into the research process.
But it is important to remember that a visual representation of a scientific concept or data is a re-presentation and not the thing itself –– some interpretation or translation is always involved. Just as writing a journal article, one must carefully plan what to “say,” and in what order to “say it.” The process of making a visual representation requires you to clarify your thinking and improve your ability to communicate with others.
In this talk, I will show my own approach to creating depictions in science and engineering—the successes and failures. Included will be a discussion about how far can we go when “enhancing” science images.
##### Computations in Science
November 28, 2018
KPTC 206 | Wednesday, 12:15 pm
## Wheland Lecture: Professor Jack W. Szostak, Harvard University
#### The Surprising Chemistry of Nonenzymatic RNA Replication
The RNA genomes of the first cells are thought to have emerged from the nonenzymatic replication of short RNA strands. We have recently found that the template-directed reaction of a primer with activated nucleotide substrates proceeds through an unexpected covalent intermediate. Our kinetic and crystallographic studies have provided insight into the mechanism of this key reaction, and to improvements in RNA copying chemistry that are both more prebiotically plausible and more accurate, efficient, and general.
##### Chemistry
November 28, 2018
GCIS W301 | Wednesday, 12:00 pm
## Prof. Zahra Fakhraai, Department of Chemistry, University of Pennsylvania
#### Understanding Glass Transition Through Interfacial Properties
Free surfaces and interfaces can affect properties of glassy systems over length scales that can be much longer than the intermolecular interaction potential. A fundamental understanding of the magnitude and length scale of these effects can allow us to understand the glass transition phenomenon and engineer nano-scaled materials with unique properties. In this presentation I show two examples of such effects and their use in producing thermally and kinetically stable glass materials. Extensive research in the past two decades has shown that the free surface of glasses, in particular for polymeric and organic glasses, have dramatically faster dynamics, resulting in strong reduction in their glass transition temperature, Tg, in ultra-thin films. We have recently shown that the surface dynamics can be faster by as much as eight orders of magnitude resulting in an apparent glass to liquid transition in molecular glass films as thick as 30 nm. The details of the thickness-dependent relaxation dynamics in thin films can elucidate properties of bulk glass that are key in verifying glass transition models. The enhanced mobility over such a large length scale can also help produce stable glasses with unique molecular packing upon physical vapor deposition.
In another example, we demonstrated that polymers’ thermal stability can be significantly improved in highly confined geometries. Capillary rise infiltration (CaRI) is used to load randomly closed-packed films of nanoparticles with various polymers. By changing the NP diameter, polymer can be confined in length scales as small as 2-3 nm. Under these conditions, entropic and enthalpic effects induced by interfaces play the dominant role in stabilizing the polymer, leading to higher Tg, higher viscosity, and improved resistance to burning and thermal degradation. We discuss the role of various parameters in achieving these thermally stable states. Host: Julia Murphy, jgmurphy102@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
November 27, 2018
GCIS W301 | Tuesday, 4:00 pm
## Yichen Hu, University of Pennsylvania
#### On the Brink of Fractionalization
Systems of strongly interacting particles can give rise to topological phases beyond non-interacting limit. Although unique features of strongly interacting topological phases, such as fractionalization of quantum degrees of freedom, have important applications in quantum information processing, these topological phases are still far from experimental realizations. In this talk, by presenting constructions of two strongly interacting topological phases, I will argue the key mechanism of their realizations is to add interactions near topological phase transitions. I will first introduce a model of interacting Majorana fermions that describes a superconducting phase with Fibonacci topological order. Then I will show that a correlated fluid of electrons and holes, dubbed fractional excitonic insulator phase, can exhibit a fractional quantum Hall effect at zero magnetic field. I will present physical evidence and conjecture that this phase can be realized in a higher angular momentum excitonic paired system in the presence of interactions.
November 27, 2018
PRC 201 | Tuesday, 1:30 pm
## Ethan Garner, PhD, Molecular and Cellular Biology, Center for Systems Biology, Harvard
#### Quantitating the motions of filaments gives insight into how bacteria grow as rods & control their rate of growth
Prof. Garner is hosted by Ed Munro and Sean Crosson
##### Biophysical Dynamics
November 27, 2018
GCIS W301 | Tuesday, 12:00 pm
## Wheland Lecture: Professor Jack W. Szostak, Harvard University
#### The Origin of Cellular Life
To understand the origin of life on Earth, and to evaluate the potential for life on exoplanets, we must understand the pathways that lead from chemistry to biology. Recent experiments suggest that a chemically rich environment that provides the building blocks of membranes, nucleic acids and peptides, along with sources of chemical energy, could result in the emergence of replicating, evolving cells. I will discuss physical mechanisms that enable the growth and division of model protocells, the possible nature of primordial RNA, and the chemistry of its replication.
##### Chemistry
November 26, 2018
Kent 120 | Monday, 4:00 pm
## Emily Sprague-Klein, Northwestern University
#### Hot Electrons & Transient Molecular Dynamics in Plasmonic Nanomaterials
Excitation of localized surface plasmon resonances yield non-equilibrium carrier populations that can then be harnessed to drive site-specific chemical processes at the nanoscale. We demonstrate the first direct detection of the molecular anion radical generated from plasmon-driven electron transfer in tightly confined sub-nanometer gaps under intense visible light irradiation. The energetics of these transient hot electron chemical processes are catalogued in a range of polypyridyl complexes in corroboration with open-shell density functional theory. Techniques for the observation of molecule-surface structural dynamics with high temporal and spatial resolution are discussed. The findings have broad applicability towards designing organic-inorganic hybrid microelectronics and nanoscale chemical reactors for surface redox reactions on the subnanometer scale. Host: Sarah King, 4-3809 or via email to sbking@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### JFI Special Seminar
November 26, 2018
GCIS W301 | Monday, 1:30 pm
## Tania Baker, Department of Biology, Massachusetts Institute of Technology
##### Biophysical Dynamics
November 21, 2018
GCIS W301 | Wednesday, 1:00 pm
## Gabriel Won
#### Glueing together Modular flows with free fermions
e revisit the calculation of multi-interval modular Hamiltonians for free fermions using a Euclidean path integral approach. We show how the multi-interval modular flow is obtained by glueing together the single interval modular flows. Our methods are based on a derivation of the non-local field theory describing the reduced density matrix, and makes manifest it's non-local conformal symmetry and $U(1)$ Kacs-Moody symmetry. We will show how the non local conformal symmetry provides a simple calculation of the entanglement entropy.
November 20, 2018
PRC 201 | Tuesday, 1:30 pm
## Gregory R. Bowman, PhD, Washington University
#### Identifying & Exploiting Protein Shape-shifting
A protein is a dynamic shape-shifter whose function is determined by the set of different structures it adopts. Unfortunately, it is often impossible to experimentally characterize most of these structures with the atomic resolution one would like in order to gain mechanistic insight or design drugs and mutations. The Bowman lab is combining enhanced sampling methods, such as Markov state models (MSMs), with biophysical experiments to overcome this limitation. Using this integrative approach, we are coming to a better understanding of how allosteric signals are transmitted between distant parts of a protein. We are also uncovering cryptic pockets that are absent in available experimental structures and provide new targets for drug development. To test our insights, we are designing and experimentally characterizing small molecules and mutations that exert allosteric control over distant functional sites. Examples of ongoing projects include (1) understanding how mutations give rise to antibiotic resistance, (2) designing allosteric drugs to combat antibiotic resistant infections, (3) understanding allosteric networks in G proteins and designing allosteric anti-cancer drugs, and (4) understanding and interfering with the mechanisms of Ebola infection.
##### Biophysical Dynamics
November 20, 2018
GCIS W301 | Tuesday, 12:00 pm
## Professor Matthew Bogyo, Stanford University
#### Chemical Tools for Identification and Imaging of Hydrolases Involved in the Pathogenesis of Cancer and Infectious Disease
Hydrolases are enzymes that often play pathogenic roles in many common human diseases such as cancer, asthma, arthritis, atherosclerosis and infection by pathogens. Therefore, tools that can be used to dynamically monitor their activity can be used as diagnostic agents, as imaging contrast agents and for the identification of novel enzymes and drug leads. In this presentation, I will describe our efforts to design and synthesize small molecule probes that produce a fluorescent signal upon binding to a hydrolase target. In the first part of the presentation, I will discuss probes targeting the cysteine cathepsins and their application to real-time fluorescence guided tumor resection and other diagnostic imaging applications. In the second half of the presentation, I will present our efforts to identify novel hydrolases in the pathogenic bacteria Staphylococcus aureus that could be targeted to enable both treatment and non-invasive imaging of disease progression.
##### Chemistry
November 19, 2018
Kent 120 | Monday, 4:00 pm
## Professor Oren Petel, Department of Mechanical and Aerospace, Engineering Carleton University
#### Impact Injury Evaluation and Mitigation Strategies Using X-ray Imaging
##### JFI Special Seminar
November 19, 2018
GCIS E223 | Monday, 1:30 pm
## Alex Turzillo, Caltech
#### Free and Interacting Short-Range Entangled Phases of Fermions: Beyond the Ten-Fold Way
It is well-known that sufficiently strong interactions can destabilize some SPT phases of free fermions, while others remain stable even in the presence of interactions. It is also known that certain interacting phases cannot be realized by free fermions. In this talk, we will study both of these phenomena in low dimensions and determine the map from free to interacting SPT phases for an arbitrary unitary symmetry. We will also describe how to compute invariants characterizing interacting phases for free band Hamiltonians with symmetry (in any dimension) using only representation theory.
November 16, 2018
PRC 364 | Friday, 1:30 pm
## Closs Lecture: Professor Lewis Rothberg, University of Rochester
#### What You Don't See Can Hurt You: The Dark Matter Problem in Luminescent Conjugated Polymers
High luminescence yields in solution bode well for easily processed conjugated polymers as the emissive species in photopumped film lasers, biological tags and display technology. The luminescence efficiency in the solid state, however, is often found to be low even when the polymer is doped dilutely into inert hosts. Our recent research involves trying to systematically vary morphology at the single chain level to illustrate the interplay between energy transfer amongst chromophores and aggregation of chromophores in determining the photophysics. We find dramatic variations in behavior as the polymer morphology evolves from extended to collapsed. In the intermediate case, we observe surprising and instructive phenomena that cannot be explained in the context of previous literature models. For example, we show that it is possible to greatly increase photoluminescence by deliberate selective photooxidation of low energy but poorly emitting chromophores. Consequences of this finding include intense luminescence spikes in single chain spectroscopy and the ability to post-process some bulk polymer samples to improve their luminescence efficiency. A revised model of the photophysics accounts for these phenomena and explains the failure of luminescence to scale with molecular weight, an observation fondly labeled “the dark matter problem” by Ivan Scheblykin.
##### Chemistry
November 16, 2018
Kent 120 | Friday, 1:15 pm
## Prof. Frederico Toschi, The Department of Applied Physics, Eindhoven University of Technology (ATU/e)
#### Genetic Competition in Weakly Compressible Turbulent Flows
The genetic competition for biological species living in marine environments can be severely influenced by fluid advection. Very often, in oceans and in lakes, cell generation times are precisely in the inertial range of eddy turnover times and therefore the influence of turbulence must be properly taken into account. We employ both an off-lattice agent-based simulation as well as an on-site density-based model to describe two competing populations in one and in two spatial dimensions under the influence of advecting (turbulent) velocity fields. The novel on-site density-based model allows to accurately and efficiently describe the dynamics of the population and the genetics of large number of individuals, making this the ideal tool to study populations in two dimensions. We find that the presence of compressible turbulent velocity fields can have a very strong effect on genetic competitions. In particular, even in regimes where the overall population structure is approximately unaltered, the flow can significantly diminish the effect of a selective advantage on fixation probabilities. We explain this effect in terms of the enhanced survival of organisms born at the sources in the flow and the influence of Fisher genetic waves. We find for both cases that even in a regime where the overall population structure is approximately unaltered, the flow can significantly diminish the effect of a selective advantage on fixation probabilities. We understand this effect in terms of the enhanced survival of organisms born at sources in the flow and of the influence of Fisher genetic waves. Host: Vincenzo Vitelli, 2-7206 or via email at vitelli@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### JFI / IME Seminar
November 16, 2018
GCIS E123 | Friday, 12:15 pm
## Giorgio Gratta, Stanford University
#### Measuring gravity at short distances and other fun tricks with levitated microspheres
##### Physics Colloquium
November 15, 2018
KPTC 106 | Thursday, 4:00 pm
## Chen-Te Ma, National Taiwan University
#### Bell’s Inequality, Generalized Concurrence and Quantum Entanglement
We demonstrate an alternative evaluation of quantum entanglement by measuring maximum violation of Bell's inequality without performing a partial trace operation in an n-qubit system by bridging maximum violation of Bell's inequality and a generalized concurrence of a pure state. This proposal is realized when one subsystem only contains one qubit and a quantum state is a linear combination of two product states. Finally, a relation of the generalized concurrence of a pure state and the maximum violation of Bell's inequality is also demonstrated in a 2n-qubit state.
November 15, 2018
PRC 201 | Thursday, 2:00 pm
## Tony Gherghetta
#### Naturalizing SUSY with the Relaxion and the Inflaton
##### Theory Seminar
November 14, 2018
PRC 201 | Wednesday, 1:30 pm
## Oni Basu, University of Chicago
#### Single-cell Transcriptomics and Biology using Microfluidics
The basic units of biological structure and function are cells, which exhibit wide variation in regard to both type and state. We assess such variation by simultaneously profiling the transcriptomes of thousands of single mammalian cells (Drop-seq) or nuclei (DroNc-seq), using high-throughput emulsion microfluidics and DNA barcodes. These are accomplished by (a) encapsulating and lysing one cell/nuclei per emulsion droplet, and (b) barcoding RNA contents from each cell/nuclei using unique DNA-barcoded micro-beads, (c) performing Next-Gen Sequencing.
We are using these droplet-based techniques to profile cell types comprising complex tissues in a variety of tissue-types such as the heart and solid tumors in mouse models and human primary tissue. Besides, we are using Drop-seq and DroNc-seq to profile cell-states, particularly cellular heterogeneity in development and differentiation processes using a combination of cell lines, mouse embryonic tissue, in vitro culture, and human induced pluripotent stem cells.
We also develop custom microfluidic devices to study phenotypic responses of cells to different environmental stimuli including physical, bio-chemical and pathogenic stimuli; I will provide some examples to illustrate some applications.
##### Computations in Science
November 14, 2018
KPTC 206 | Wednesday, 12:15 pm
## The Tuesday JFI Seminar - Prof. Aashish Clerk, IME, The University of Chicago
#### Driven-dissipative Quantum Phenomena: from Synthetic Non-reciprocity to New Kinds of Topology
In this talk, I’ll give an introduction to theory work in my group focused on understanding and exploiting driven-dissipative quantum phenomena in engineered quantum systems. I’ll start by discussing work showing how engineered dissipation can make almost any kind of interaction between two subsystems non-reciprocal (i.e. uni-direcitonal). This is provides a systematic approach for designing quantum systems with one-way interactions, with applications ranging from new kinds of quantum measurement devices to unusual many-body effects. In the second part of the talk, I’ll focus on work exploring how two-photon (parametric) driving can be used to realize new kinds of topological bosonic systems. While these systems have Hamiltonians analogous to topological superconductors, their physics is remarkably distinct from their fermionic partners. Among other things, I’ll discuss the surprising properties of a bosonic version of the Kitaev-Majorana chain, and how these ideas could be realized with superconducting quantum circuits. Host: Timothy Berkelbach, 4-9879 or via email at berkelbach@uchicago. Persons with a disability who may need assistance please contact Brenda Thomas 2-7156 or by email to bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
November 13, 2018
GCIS W301 | Tuesday, 4:00 pm
## Hart Goldman, Illinois
#### Dirac Composite Fermions and Emergent Reflection Symmetry about Even Denominator Filling Fractions
Motivated by the appearance of a “reflection symmetry” in transport experiments and the absence of statistical periodicity in relativistic quantum field theories, we propose a series of relativistic composite fermion theories for the compressible states appearing at filling fractions 1/2n in quantum Hall systems. These theories consist of electrically neutral Dirac fermions attached to 2n flux quanta via an emergent Chern-Simons gauge field. While not possessing an explicit particle-hole symmetry, these theories reproduce the known Jain sequence states proximate to filling 1/2n, and we show that such states can be related by the observed reflection symmetry, at least at mean field level. We further argue that the lowest Landau level limit requires that the Dirac fermions be tuned to criticality, whether or not this symmetry extends to the compressible states themselves
November 13, 2018
PRC 201 | Tuesday, 1:30 pm
## Zhen Gu, PhD, UCLA
#### Leverage Physiology for Bioresponsive Drug Delivery
Spurred by recent advances in materials chemistry, molecular pharmaceutics & nanobiotechnology, stimuli-responsive “smart” systems offer opportunities for precisely delivering drugs in dose-, spatial- & temporal-controlled manners. In this talk, I will discuss our ongoing efforts in developing physiological signal-triggered bio-responsive drug delivery systems. I will first present the glucose-responsive synthetic systems for biomimetic delivery of insulin for diabetes treatment. Bio-responsive microneedle patches and vesicle fusion-mediated synthetic beta cells will be emphasized.
I will further discuss the local & targeted delivery of immunomodulatory therapeutics for enhanced cancer therapy. Our latest study utilizing platelets and injectable gels for targeted/local delivery of immune checkpoint inhibitors will be specifically introduced.
##### Biophysical Dynamics
November 13, 2018
GCIS W301 | Tuesday, 12:00 pm
## Mulliken Lecture: Professor Peter Rossky, Rice University
#### Translating the Message in Spectroscopic Probes of Conjugated Molecular Materials
Over recent decades, there have been a steadily increasing number of studies on electronically conjugated materials for use in solar photovoltaic cells, organic transistors, and fluorescent probes. Progress in using semiconducting polymers has been limited by a fundamental lack of knowledge at the nanoscale underlying variations in electro-optical behavior. Hence, in contrast to familiar silicon-based technology, there is a dearth of principles to drive the bottom-up design of material building blocks.
Experiments probe such materials by their response to light, i.e., spectroscopically. The challenge is to interpret the observations in molecular terms. Computational modeling based on the physics of atomistic details and explicit electronic structure is ideally suited to enabling this connection of spectra to structure, since the connection in modeling is unambiguous while the experiment provides a strong constraint on the validity of the model. In this presentation, I will discuss examples of conjugated molecular material systems studied by theoretical, modeling, and experimental approaches that elucidate both atomistic and electronic structure and dynamics in a way inaccessible to either theory or experiment alone. Examples from the area of conjugated polymers and also from biosensors based on GFP will be presented.
##### Chemistry
November 12, 2018
Kent 120 | Monday, 4:00 pm
## Professor David Sarlah, University of Illinois at Urbana-Champaign
#### Dearomative Functionalization Strategies and Synthesis of Anticancer Natural Products"
Small complex molecules are highly desired in all areas of chemistry, but they are also often difficult to access. Selective transformations of aromatic compounds could provide a more direct route to such desirable targets; however, the many challenges associated with dearomative functionalization have left these types of reactions widely underdeveloped. Our group has been developing new strategies that bridge the gap between dearomatization functionalization and alkene chemistry. In pursuit of this goal, we have developed dearomative functionalizations using small molecules – arenophiles – that enable reactions of isolated alkenes in aromatic substrates. Thus, well-established olefin reactions, such as dihydroxylation and reduction, can now be more directly applied to arenes. Additionally, arenophiles in combination with transition metal catalysis provide unique platform and enable the rapid access to a diverse range of products that are both challenging to synthesize via existing methods and complementary to those acquired through biological or chemical dearomative processes. Finally, using this methodology we have recently completed the synthesis of several complex anticancer natural products.
##### Chemistry
November 9, 2018
Kent 120 | Friday, 1:15 pm
## Transient driving that kinetically converts a foe into a friend
body food 12:00
brain food 12:15
##### MRSEC Baglunch
November 9, 2018
GCIS E123 | Friday, 12:00 pm
## Helen Quinn, SLAC
#### Science, Engineering and Art as well –why it is hard to teach science well
will reflect on what we know about teaching science for k-12 students and for undergraduates, how we know it, and what it tells us about good teaching. To teach well you must engineer the right learning conditions with careful design goals for what is to be learned, you must understand both the subject area you wish to teach and something of what research on learning tells us about critical aspects of learning that area (this is known as pedagogical content knowledge or content knowledge for teaching) and then you must be a skilled improvisational performance artist to pull off the lessons as intended, responding to the needs of students who enter your classroom with a wide range of prior knowledge, engaging them all as active participants in the learning.
This talk is based on work I have been doing in the area of science education since my retirement in 2010 from physics research, summarizing what I have learned in the process. Illinois and approximately 30 other states have adopted new science standards based on the NAS study “A Framework for k-12 science education” that I led. This study tried to capture the learning about learning from science education research as well as to shift the goals for what needs to be learned. I will discuss how it, together with research studies focused on teaching physics or other sciences at the undergraduate level, suggests changes in undergraduate teaching approaches as well.
##### Physics Colloquium
November 8, 2018
KPTC 106 | Thursday, 4:00 pm
## IME Distinguished Colloquium Series - Shanhui Fan, Stanford
#### Concepts of Nanophotonics and Energy Applications
Light, or electromagnetic waves, represent one of the most important carriers of heat and energy. New capabilities to manipulate light, as enabled by new classes of electromagnetic structures such as photonic crystals, metamaterials and plasmonic systems, therefore have significant implications for energy applications. In this talk, we will discuss some of these implications, illustrated by examples of our own recent works ranging from radiative cooling to dynamic wireless power transfer.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
November 7, 2018
KCBD 1103 | Wednesday, 4:00 pm
#### Topological Origin of Equatorial Waves
Topology sheds new light on the emergence of unidirectional edge waves in a variety of physical systems, from condensed matter to artificial lattices. Waves observed in geophysical flows are also robust to perturbations, which suggests a role for topology. We show a topological origin for two celebrated equatorially trapped waves known as Kelvin and Yanai modes, due to the Earth’s rotation that breaks time-reversal symmetry. The non-trivial structure of the bulk Poincaré wave modes encoded through the first Chern number of value 2 guarantees existence for these waves. The invariant demonstrates that ocean and atmospheric waves share fundamental properties with topological insulators, and that topology plays an unexpected role in the Earth climate system.
##### Computations in Science
November 7, 2018
KPTC 206 | Wednesday, 12:15 pm
## 1st Tuesday Colloquium - Prof. Mark D. Ediger, University of Wisconsin-Madison
#### Exploring the Limits of Amorphous Packing with Ultrastable Glasses
Glasses formed by cooling a liquid inherit both their structure and their limited stability from the liquid state. In contrast, glasses prepared by vapor deposition can avoid both of these limitations. By utilizing the high mobility present near the free surface of many organic glasses, vapor deposition can build glasses with low enthalpy, high density, and high thermal stability. Based upon their position on the potential energy landscape, these materials approach “ideal glass” packing that otherwise could only be achieved by annealing a liquid-cooled glass for thousands or millions of years. Vapor deposition of organic semiconductors produces glasses with improved properties for organic electronics, including the ability to produce anisotropic glasses with a wide range of structures. Remarkably, this “anti-epitaxy” process uses the free surface structure as its template, rather than the substrate structure. Recent work has shown that optimizing vapor deposition can produce organic light emitting diodes (OLEDs) that are more efficient and have extended lifetimes. Host: Thomas Witten, 2-2-0948 or via email to t-witten@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The 1st Tuesday JFI Colloquium
November 6, 2018
GCIS W301 | Tuesday, 4:00 pm
## Andy LiWang, PhD, Quantitative and Systems Biol, UC Merced
#### Can proteins tell time?
Circadian clocks arose in organisms as an adaptation to the rotation of the earth. These clocks produce involuntary anticipation of sunrise and sunset by generating a succession of biochemical phases. In this talk, the mechanism of a model system, that of cyanobacteria, will be described. Briefly, it depends on phosphorylation, long-range allostery, dynamics, and protein metamorphosis. Because a simple mixture of clock proteins and ATP generate a persistent macroscopic rhythm, the mechanism of the clock can be studied in real time as it ticks. Now, signal transduction pathways have been reconstituted with the oscillator so that rhythmic transmission of clock signals can be studied in vitro.
##### Biophysical Dynamics
November 6, 2018
GCIS W301 | Tuesday, 12:00 pm
## Luca Delacretaz, Stanford University
#### Bounds on transport and thermalization from positivity
November 6, 2018
PRC 215 | Tuesday, 12:00 pm
## Professor Daniel G. Nocera, Harvard University
#### Food and Fuel from Sunlight, Air and Water
##### Chemistry
November 5, 2018
Kent 120 | Monday, 4:00 pm
## Naama Barkai, PhD, Molec Genetics and Physics, Weizmann
#### Robustness & scaling in embryonic development
Naama Barkai, PhD, Departments of Molecular Genetics and of Physics of Complex Systems, Weizmann Institute of Science is the 2018-19 Frederick Seitz Lecturer in Interdisciplinary Science.
Informal reception will follow Dr. Barkai's presentation in the lobby of the KCBD
##### Biophysical Dynamics
November 5, 2018
KCBD 1103 | Monday, 1:30 pm
## Professor Peter G. Wolynes, Rice University
#### Energy Landscape Theory: From Folding Proteins to Folding Chromosomes
The statistical mechanics of energy landscapes has resolved the paradoxes of how information-bearing matter can assemble itself spontaneously. I will explain how our current understanding of protein folding landscapes not only leads to successful schemes for predicting protein structure from sequence but also has given quantitative insight into how folding and function shape molecular evolution. While protein folding is, in the main, thermodynamically controlled and not kinetically limited, longer structures in the cell can assemble in a kinetically controlled, nonequilibrium fashion. Nevertheless, I will show how energy landscape theory provides tools for extracting from low resolution experimental structural methods and kinetic information about the structure and cooperative dynamics of chromosomes.'
##### Chemistry
November 2, 2018
Kent 120 | Friday, 1:15 pm
## Transient driving that kinetically converts a foe into a friend
Eat 12:00
Action 12:15
##### MRSEC Baglunch
November 2, 2018
GCIS E123 | Friday, 12:00 pm
## Marcos Santander, The University of Alabama
#### Exploring the high-energy sky with neutrinos and gamma rays
In 2013 the IceCube neutrino observatory, a cubic-kilometer particle detector deployed deep within the South Pole glacier, announced the first detection of an astrophysical flux of high-energy neutrinos in the TeV-PeV range. This breakthrough discovery has prompted a wide-ranging observational effort aimed at identifying the sources of the neutrino flux by combining IceCube measurements with observations spanning the entire electromagnetic spectrum. Gamma rays in particular provide a powerful tool to search for neutrino source counterparts as both particles are produced in high-energy hadronic interactions. The detection and study of neutrino sources would not only signify the start of a new form of astronomy, but could also solve long-standing questions in high-energy astrophysics such as the origin of high-energy cosmic rays. This talk will introduce the IceCube detector, summarize recent results from multi-messenger searches of neutrino sources and present an overview of current and future gamma-ray follow-up observations, especially with the Cherenkov Telescope Array, a ground-based facility for very-high-energy gamma-ray astronomy currently under construction.
##### Physics Colloquium
November 1, 2018
KPTC 106 | Thursday, 4:00 pm
## Saebyeok Jeong, Stony Brook
#### Opers, surface defects, and Yang-Yang functional
In this talk, I will introduce a gauge theoretical derivation of a correspondence which relates quantization of integrable system to symplectic geometry [1]. First, I will briefly review how the Hitchin integrable systems are associated with the class S theories. The Hitchin moduli space is identified with the moduli space of flat connecitons, with a distinctive Lagrangian submanifold of opers. It is suggested that the holomorphic functions on the space of opers are the (off-shell) spectra of the quantum Hitchin Hamiltonians [2]. Moreover, the conjecture in [4] states that the generating function for the space of opers is equal to the effective twisted superpotential of the class S theory on the two-dimensional omega-background. I will show a gauge theoretical derivation of the correspondence. The derivation involves the following key ingredients:
1) Use half-BPS codimension-two (surface) defects in the class S theories to construct the opers and their solutions.
2) Analytically continue the surface defects partition functions to build connection formulas of the solutions.
3) Construct a Darboux coordinate system relevant to the correspondence.
4) Compute the monodromies of opers from 2) and compare with the expressions from 3) The direct comparison establishes the desired identity.
##### Theory Seminar
October 31, 2018
PRC 201 | Wednesday, 1:30 pm
## Timothy C. Berkelbach, University of Chicago
#### Stochastic Quantum Chemistry
Exact many-particle quantum mechanics has a prohibitive cost that grows exponentially with the size of the system. Most modern quantum chemistry is built on approximations that result in more tractable algorithms with polynomial scaling, but which qualitatively fail for many important problems. I will describe an alternative approach that uses stochastic techniques to circumvent this prohibitive cost (i.e. a flavor of quantum Monte Carlo). In particular, this approach is based on a very general and recently-developed framework for stochastic linear algebra called "fast randomized iteration", due to Lim and Weare. I will describe the FRI algorithm, its application to challenging problems in quantum chemistry, and its advantages over similar techniques.
##### Computations in Science
October 31, 2018
KPTC 206 | Wednesday, 12:15 pm
## The Tuesday JFI Seminar - Prof. Christos Panagopoulos, Nanyang Techenilogical University, Singapore
#### Tunable Room Temparature Skyrmions
The electric field experienced by a travelling electron translates, in its rest frame, to a magnetic field proportional to its velocity – a relativistic effect which is notable in crystalline lattices with heavy atoms. The Zeeman interaction between the electron spin and this effective magnetic field is equivalent to the coupling of the electronic spin and momentum degrees of freedom, known as spin-orbit coupling (SOC). Importantly, SOC effects are greatly enhanced in reduced dimensions: inversion symmetry is broken at the surface or interface, and the resultant electric field couples to the spin of itinerant electrons. Host: Timothy Berkelbach, 4-9879 or via email to berkelbach@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
The states induced by engineering SOC and inversion symmetry breaking in magnetic materials open a broad perspective, with impact in the technology of spin topology. For example, in conventional ferromagnets the exchange interaction aligns spins and the anisotropy determines energetically preferred orientations. Meanwhile, the interaction generated by SOC and broken inversion symmetry induces a relative tilt between neighbouring spins. Magnetic skyrmions – finite-size two-dimensional (2D) ’whirls’ of electron spin – form due to the competition between these ‘winding’ & ‘aligning’ exchange interactions.
Skyrmions have several compelling attributes as prototype memory elements, namely their (1) nontrivial spin topology, protecting them from disorder and thermal fluctuations, (2) small size and self-organization into dense lattices and (3) particle-like dynamics, manipulation and addressability. Using a novel materials architecture we developed recently, I will address quantifiable insights towards understanding skyrmion stability and dynamics, and directions for exploiting their properties in nanoscale devices at room temperature.
##### The Tuesday JFI Seminar
October 30, 2018
GCIS W301 | Tuesday, 4:00 pm
## Yizhi You, Princeton Center for Theoretical Physics
#### Fracton phase of matter: Lattice models, gauge theories and realizations
Fracton phase of matter shares many features of topological order, including long-range entangled ground states and non-trivial braiding statistics. At the same time, fracton phase contains subextensive ground-state degeneracy and the restricted mobility of quasiparticle which exclude itself from the TQFT paradigm. In this talk, I start from several fracton lattice models and demonstrate their relation with gauged subsystem symmetric SPT phase. Further, I will present a theoretical framework for higher Chern-Simons theory in 3D which realizes a deconfined U(1) fracton phase. In the end, I propose an experiment platform for realizing diverse fracton stabilizer codes based on interacting nanowires, which enables us to fabricate a zoology of fracton states and thus provides a powerful novel avenue to the realization of stable quantum memory and fault-tolerant quantum computing.
October 30, 2018
PRC 201 | Tuesday, 12:00 pm
## Professor Daniel Palanker, Department Ophthamology & Hansen Experimental Physics Laboratory, Stanford University
#### Photovoltaic Restoration of Sight in Retinal Degeneration
Retinal degenerative diseases lead to blindness due to loss of the “image capturing” photoreceptors, while neurons in the “image-processing” inner retinal layers are relatively well preserved. Information can be reintroduced into the visual system using electrical stimulation of the surviving inner retinal neurons. Some electronic retinal prosthetic systems have been already approved for clinical use, but they provide low resolution and involve very difficult implantation procedures. We developed a photovoltaic subretinal prosthesis which converts light into pulsed electric current, stimulating the nearby inner retinal neurons. Visual information is projected onto the retina from video goggles using pulsed near- infrared (~880nm) light. This design avoids the use of bulky electronics and wiring, thereby greatly reducing the surgical complexity. Optical activation of the photovoltaic pixels allows scaling the implants to thousands of electrodes.
In preclinical studies, we found that prosthetic vision with subretinal implants preserves many features of natural vision, including flicker fusion at high
frequencies (>20 Hz), adaptation to static images, center-surround organization and non-linear summation of subunits in receptive fields, providing high spatial resolution. Initial results of the clinical trial with our implants (PRIMA, Pixium Vision) having 100µm pixels, as well as preclinical measurements, confirm that spatial resolution of prosthetic vision can reach the sampling density limit. For a broad acceptance of this technology by millions of patients who lost central vision due to age-related macular degeneration, visual acuity should exceed 20/100, which requires pixels smaller than 25µm. I will describe the fundamental limitations in electro-neural interfaces and 3-dimensional configurations which should enable such a high spatial resolution. Ease of implantation of these wireless modules, combined with high resolution opens the door to highly functional restoration of sight.
Host: Bozhi Tian, 2-8749 or via email at btian@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### Special JFI Seminar
October 29, 2018
GCIS W301 | Monday, 1:30 pm
## Professor Matthew Kanan, Stanford University
#### Re-sourcing Chemicals
This talk will describe our recent efforts to turn CO2 into a carbon source for commodity chemicals. Our goal is to develop scalable processes in which the use of CO2 affords a clear chemical advantage over conventional fossil fuel–based routes. I will first describe new carboxylation chemistry to generate (di)-carboxylic acids that have high-volume applications. Conventional carboxylation methodology relies on extremely energy-intensive reagents. We have found systems in which simple carbonate salts deprotonate un-activated C–H bonds, generating carbon-centered nucleophiles that react with CO2 to form C–C bonds. As one application, we used this chemistry to develop a high-yielding route from inedible biomass to furan-2,5-dicarboxylic acid (FDCA), a monomer that is currently being pursued as a replacement for terephthalic acid in polyester synthesis. To generalize this strategy, we have recently developed nanostructured carbonates that can perform hydrocarbon C–H insertion. In a two-step cycles, these materials convert arenes, CO2, and alcohols into aromatic esters with no use of stoichiometric reagents or generation of waste products. In the second part of my talk, I will describe our work on electrochemical systems for generating C2 feedstock chemicals. We have pioneered the use of grain boundaries to create metastable active surfaces for CO2 and CO reduction and recently elucidated a structural model to explain grain boundary effects. I will discuss the prospects for exploiting grain boundary effects in electrosynthesis and the design of prototype reactors that provide high synthesis rates and concentrated product streams.
##### Chemistry
October 29, 2018
Kent 120 | Monday, 1:15 pm
## Professor Jiaoyang Jiang, University of Wisconsin-Madison
#### Specificity, Function and Regulation of Protein O-GIcNAc Modification
The N-acetylglucosamine (O-GlcNAc) modification is an essential glycosylation that has been identified on over 1,000 proteins. It dynamically modulates protein functions and regulates numerous biological processes in physiology and disease. O-GlcNAc modification is added by O-GlcNAc transferase (OGT) and removed by O-GlcNAcase (OGA). Despite recent progress, challenges remain to decipher the biological roles of O-GlcNAc modification and its regulation by OGT and OGA on a broad range of substrates that lack an apparent sequence motif. In this talk, I will present our recently developed structural biology and chemical biology approaches to start revealing the specificity, function and regulation of O-GlcNAc modification.
##### Chemistry
October 26, 2018
Kent 120 | Friday, 1:15 pm
## William Irvine, University of Chicago
#### Spinning Top-ology
Geometry, topology and broken symmetry play a powerful role in determining the physics of materials. In this colloquium I will talk of activated materials and fluids built out of mechanically spinning components and show how the subtle interplay of structure, time-reversal and parity leads to `odd' solid and fluid mechanics. In particular I will discuss a simple kind of active meta-material – coupled gyroscopes – that naturally encodes non-trivial topology in its vibrational spectrum. In particular, I will show how topology can emerge not only in ordered gyro materials but also their amorphous counterparts. We will then foray into activated colloidal gyro fluids and see how breaking symmetry under parity leads to chiral surface states and odd instabilities driven by viscous forces. We will use these chiral waves as a tool to observe the presence of odd (or Hall) viscosity in our chiral fluid.
##### Physics Colloquium
October 25, 2018
KPTC 106 | Thursday, 4:00 pm
## Professor Marc Fontecave, Collège de France
#### FeS Clusters and Thiolation Reactions: Lessons from tRNA- and Protein-modifying Enzymes
Living cells are full of molecules containing sulfur atoms, for example biotin, lipoic acid, thiamin but also a variety of nucleosides within transfer RNAs and inorganic cofactors such as iron-sulfur (FeS) clusters. However, how these compounds are biosynthesized and how sulfur atoms are incorporated into organic substrates are still open fascinating questions. The discovery that important enzymes involved in thiolation reactions are FeS enzymes belonging to the Radical-SAM (S-Adenosyl-Methionine) enzyme superfamily, such as biotin synthase or lipoate synthase, has suggested a novel function for FeS clusters. It is proposed that they serve, in these enzymes, as a sulfur storage system from which sulfur atoms can be delivered to activated substrates during thiolation. The chemistry of Radical-SAM enzymes in the specific context of these reactions will thus be presented. However, other results, in particular from our laboratory, have challenged this theory since we have shown, during our functional and structural characterization of tRNA- and protein-sulfurating FeS enzymes (methylthiotransferases and thiolases) that thiolation can occur without mobilization of the sulfur atoms of the FeS clusters. Here we discuss these alternative mechanisms.
##### Chemistry
October 25, 2018
Kent 120 | Thursday, 1:15 pm
## Pedro Saenz, MIT
#### Spin lattices of walking droplets
Understanding the self-organization principles and collective dynamics of non-equilibrium matter remains a major challenge despite considerable progress over the last decade. In this talk, I will introduce a hydrodynamic analog system that allows us to investigate simultaneously the wave-mediated self-propulsion and interactions of effective spin degrees of freedom. Millimetric liquid droplets can walk across the surface of a vibrating fluid bath, self-propelled through a resonant interaction with their own guiding wave fields. A walking droplet, or ‘walker', may be trapped by a submerged circular well at the bottom of the fluid bath, leading to a clockwise or counter-clockwise angular motion centered at the well. When a collection of such wells is arranged in a 1D or 2D lattice geometry, a thin fluid layer between wells enables wave-mediated interactions between neighboring walkers. Through experiments and mathematical modeling, we demonstrate the spontaneous emergence of coherent droplet rotation dynamics for different types of lattices. For sufficiently strong pair-coupling, wave interactions between neighboring droplets may induce local spin flips leading to ferromagnetic or antiferromagnetic order. Transitions between these two forms of order can be controlled by tuning the lattice parameters. More generally, our results reveal a number of surprising parallels between the collective spin dynamics of wave-driven droplets and known phases of classical condensed matter systems. This suggests that our hydrodynamic analog system can be used to explore universal aspects of active matter and wave-mediated particle interactions, including spin-wave propagation and topologically protected dynamics far from equilibrium.
##### Computations in Science
October 24, 2018
KPTC 206 | Wednesday, 12:15 pm
#### Wilson Loops, Wyckoff Positions, and Wannier Functions: New Developments in Stable and Fragile Topology
The interplay of topology and geometry has been -- and continues to be -- a rich area of study for condensed matter physics. Recently, we have realized that spatial symmetries allow for the stabilization of topological phases much more exotic than those that can be found with time-reversal symmetry alone. Examples include topological crystalline insulators, "hourglass Fermion" phases, and Dirac and double-Weyl semimetals. In this talk, I will review recent developments in the theory of band representations which highlight the role of Wannier functions and holonomy in explaining the origins of topological crystalline behavior. I will show how this relates to several new ideas, such as symmetry indicators, topological phases with high co-dimension boundary states, and the "fragile" topology of isolated groups of bands. Finally, I will discuss how non-symmorphic symmetries can protect novel topological surface states, which can be diagnosed through the holonomy of Bloch functions.
October 24, 2018
PRC 201 | Wednesday, 11:00 am
## MRSEC Surface Metrology Workshop
#### in cooperation with Olympus
8:30 AM : Breakfast
9:00 AM: Introduction to LEXT OLS5000 Laser Confocal Microscope, Guangnan Meng, PhD
10:00 AM: Coffee Break
10:15 AM: MRSEC Student Talks: Applications
11:30 AM: A Few Things You Need to Know About Surface Roughness: Guangnan Meng, PhD
12:15 PM: Lunch (registration required)
1:00 PM - 5:00 PM: Sample Demonstrations and Discussions
https://www.surveymonkey.com/r/9QBQFRN
##### MRSEC Workshop
October 24, 2018
GCIS W301 | Wednesday, 9:00 am
## Prof. Michael Grünwald, Department of Chemistry, University of Utah
#### Orientational Order in Self-Assembled Nanocrystal Superlattices
Self-assembly of nanocrystals into functional materials requires precise control over nanoparticle interactions in solution, which are dominated by organic ligands that densely cover the surface of nanocrystals. In this talk, I will present a computational study of ligand effects in the self-assembly of small, non-spherical nanocrystals. We focus on nanocrystals with cuboctahedral and truncated octahedral shape and determine their self-assembly behavior as a function of ligand length and solvent quality. Our model, which is based on a coarse-grained description of ligands and a schematic representation of solvent effects, reproduces the experimentally observed superstructures, including recently observed superlattices with partial and short-ranged orientational alignment of nanocrystals. We show that small differences in nanoparticle shape, ligand length and coverage, and solvent conditions, can lead to markedly different self-assembled superstructures due to subtle changes in the free energetics of ligand interactions. Our results help explain the large variety of different reported superlattices self-assembled from seemingly similar particles and can serve as a guide for the targeted self-assembly of nanocrystal superstructures. Host: Suri Vaikuntanathan, 2-7256 or via email at svaikunt@uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
October 23, 2018
GCIS W301 | Tuesday, 4:00 pm
## Professor Marc Fontecave, Collège de France
#### Carbon Dioxide to Fuels: from Enzymes to Bioinspired Catalysts
##### Chemistry
October 23, 2018
Kent 120 | Tuesday, 1:15 pm
## Yuhai Tu, PhD, IBM
#### Nonequilibrium physics in biochemical oscillations
A central problem in systems biology is how living systems manage to perform precise functions (development, replication, signaling, etc.) by using inherently noisy biochemical networks. What are the molecular mechanisms for control? What are the design principles for the underlying biochemical networks? What are the energy costs for regulation? In this talk, we will present some recent results to address these general questions in biochemical oscillatory systems. We will discuss the molecular mechanism and energy cost for enhancing the accuracy and synchronization of biochemical oscillators [1]; and the design principles for oscillatory biochemical networks to achieve both high entrainability and low phase fluctuations [2].
[1] “The free-energy cost of accurate biochemical oscillations”, Y. Cao, H. Wang, Q. Ouyang, and Yuhai Tu, Nature Physics, 11, 772, 2015.
[2] “Design principles for enhancing phase sensitivity and suppressing phase fluctuations simultaneously in biochemical oscillatory systems”, C. Fei, Y. Cao, Q. Ouyang, and Yuhai Tu, Nature Communications, doi:10.1038/s41467-018-03826-4, 2018.
##### Biophysical Dynamics
October 23, 2018
GCIS W301 | Tuesday, 12:00 pm
## Chemistry Colloquium: Professor Naoto Chatani, Osaka University
#### Development of New Catalytic Reactions Involving the Activation of Traditionally Inert Bonds
Organic molecules contain a variety of chemical bonds. Organic synthesis involves the cleavage of a chemical bond and the formation of a new chemical bond. However, not all of the chemical bonds in organic molecules have been used in organic synthesis. Thus, organic synthesis is heavily dependent on the reactivity of chemical bonds. If so-called unreactive bonds were to be used directly in organic synthesis, new possibilities for developing new synthetic methodologies would arise. We have utilized, not only the activation of C-H bonds, but also the activation of unreactive single bonds, such as C-C, C-O, C-N, and C-F bonds, and the activation of C-C triple bonds and C-O double bonds, in our quest to develop new types of transformations that will lead to further diversification in the field of organic synthesis.
##### Chemistry
October 22, 2018
Kent 120 | Monday, 4:00 pm
## Professor Michael J. Hatridge, Department of Physics, University of Pittsburgh
#### Qubit Measurement with Two-Mode Squeezed Light
High fidelity qubit measurement is essential for scalable, fault-tolerant quantum computing. In superconducting circuits, qubit readout with fidelity above 99% has been achieved by using a quantum-limited parametric amplifier such as the Josephson Parametric Converter (JPC) as the first stage amplifier. However, the Signal-to-Noise Ratio (SNR) of such readout is fundamentally limited by quantum fluctuations in the coherent readout pulse. Alternatively, readout with squeezed light can be used to reduce fluctuation along certain quadratures and thus improve the SNR. In this talk, we demonstrate a readout scheme with two-mode squeezed light both produced and amplified by JPCs in an interferometer unbalanced by a transmon qubit/cavity. This configuration has been predicted to improve the SNR compared to readout with both coherent states and single-mode squeezed light. We have demonstrated a 50% improvement in SNR compared to coherent state readout, and find that the system actual works best when when we deliberately break the path for signals in the system, so that only the fluctuations passing through it interfere. We'll also discuss the prospects for placing qubits on both arms of the interferometer and performing measurements which generate remote entanglement between them.
##### JFI Special Seminar
October 22, 2018
GCIS E223 | Monday, 3:30 pm
## Inorganic/Organic Seminar: Professor Hemamala Karunadasa, Stanford University
#### Between the Sheets: The Molecular Chemistry of Hybrid Perovskites
The tools of synthetic chemistry allow us to tune molecules with a level of precision not yet accessible with inorganic solids. We have investigated hybrid perovskites that couple organic small molecules with the optical and electronic diversity of extended inorganic solids. I will share our current understanding of these materials, whose technologically relevant properties are highly amenable to synthetic design.
The 3D lead-iodide perovskites have recently been identified as low-cost absorbers for high-efficiency solar cells. Although the efficiencies of devices with perovskite absorbers have risen at an impressive rate, the materials’ intrinsic instability and toxicity may impede their commercialization. I will discuss methods developed by our group to address these problems. The 2D hybrid perovskites have dramatically different properties from their 3D congeners. We discovered that some 2D perovskites emit broadband white light (similar to sunlight) when excited by UV light. I will discuss how these materials, which do not contain extrinsic dopants or obvious emissive sites, could emit every color of visible light. Although the organic molecules in hybrid perovskites have mostly played a templating role, we have investigated their role in engendering reactivity. I will describe reactions that occur between the inorganic sheets, which allow these nonporous solids to capture small molecules.
##### Chemistry
October 19, 2018
Kent 120 | Friday, 1:15 pm
## Can a large packing be assembled from smaller ones ?
Eat 12
##### MRSEC Baglunch
October 19, 2018
GCIS E123 | Friday, 12:00 pm
## Jean Dalibard, Collège de France
#### Exploring Flatland with cold atoms
The physics of many-body systems strongly depends on their dimensionality. For example, in a two-dimensional world, most standard phase transitions towards an ordered state of matter like crystals or magnets would not occur because of the increased role of fluctuations. However, non-conventional phase transitions can still take place, as understood by Kosterlitz and Thouless (2016 Nobel prize). In this talk I will present some important features of Flatland physics explored with cold atomic gases, such as the existence of a superfluid transition that occurs in the absence of Bose-Einstein condensation. I will also discuss out-of-equilibrium properties of these atomic 2D gases, in connection with the so-called Kibble-Zurek mechanism.
##### Physics Colloquium
October 18, 2018
KPTC 106 | Thursday, 4:00 pm
## IME Distinguished Colloquium Series - Prashant Kamat
Professor Prashant Kamat from University of Notre Dame will speak as part of the IME Distinguished Colloquium Series.
Event will be followed by a reception from 5 pm to 6 pm at ERC in IME’s 2nd floor lounge/atrium area
##### Molecular Engineering
October 17, 2018
KCBD 1103 | Wednesday, 4:00 pm
## Peizhi Du, Maryland University
#### Hybird seesaw leptogenesis and TeV singlets
The appealing feature of inverse seesaw models is that the neutrino mass emerges from the exchange of TeV scale singlets with sizable Yukawa couplings, which can be tested at colliders. However, the tiny Majorana mass splitting between TeV singlets is left unexplained. Moreover, we argue that these models suffer from a structural limitation that prevents a successful thermal leptogenesis if Yukawa couplings are unsuppressed. In this talk, I will introduce a hybrid seesaw model, where we replace the mass splitting with a coupling to a high scale seesaw module including a TeV scalar. I will show that this structure achieves the goal of filling both the above gaps with couplings of order unity. The necessary structure automatically arises embedding the seesaw mechanism in composite Higgs models. Our hybrid seesaw models have an interesting interplay between high scale and TeV scale physics in leptogenesis and enlarges the range of allowed high scale singlet masses.
##### Theory Seminar
October 17, 2018
PRC 201 | Wednesday, 1:30 pm
## Andrew Ferguson, University of Chicago
#### Machine learning design of self-assembling colloidal crystals and inference of protein folding funnels
Data-driven modeling and machine learning have opened new paradigms and opportunities in the understanding and design of soft and biological materials. Colloidal particles with tunable anisotropic surface interactions are of technological interest in fabricating responsive actuators, biomimetic encapsulants, and photonic crystals with omnidirectional band gaps. In the first part of this talk, I will describe our applications of nonlinear manifold learning to determine low-dimensional assembly landscapes for self-assembling patchy colloids. These landscapes connect colloid architecture and prevailing conditions with emergent assembly behavior, and enable inverse building block design by rational sculpting of the landscape to engineer the stability and accessibility of desired aggregates. Rational engineering of structural and functional polymers and proteins requires an understanding of the underlying free energy landscapes dictating thermodynamic stability and kinetic folding pathways. In the second part of this talk, I will describe an approach integrating ideas from dynamical systems theory and nonlinear manifold learning to reconstruct multidimensional protein folding funnels from the time evolution of single experimentally-measurable observables.
##### Computations in Science
October 17, 2018
KPTC 206 | Wednesday, 12:15 pm
## Lee Lecture: Professor Susumu Kitagawa, Kyoto University
#### Chemistry and Application of Soft Porous PCP/MOF
e have found unique porous properties of PCPs/MOFs, which possess flexible or dynamic porous frameworks, reversibly responding to external stimuli, not only chemical but also physical. They were developed in an effort to realize dynamic porous and collective functionality not found in conventional materials. Their compositions of metal ions and organic molecules have achieved diversity in the electronic states. That is, the spatial and electronic structures can be altered, realizing magnetic and dielectric properties as well as oxidation− reduction functions. Besides normal storage, such MOFs have vast potential for separation with an extremely high selectivity, high-efficiency storage, and catalysis, as well as sensing and actuator functions. For these reasons, many studies investigate these materials. In this lecture, I discuss porous materials with capabilities that exceed current ones and the future research direction.
##### Chemistry
October 17, 2018
GCIS W301 | Wednesday, 12:00 pm
## Jessica M.J. Swanson, The University of Chicago
#### Unraveling Multistep Kinetic Mechanisms Behind Coupled Ion Exchange: A Case Study on Cl-/H+ Exchangein ClC Antiporters
Understanding complex mechanisms such as transmembrane ion exchange by proteins in molecular, thermodynamic, and kinetic detail remains a significant challenge. In this talk, I will present a new approach to integrate experimental and simulation data to fully characterize Cl–/H+ exchange in ClC antiporters. Rate coefficients are first calculated with reactive and polarizable molecular dynamics simulations and then optimized within a coupled kinetic (Markov state) model to reproduce experimental data. This produces a set of solutions that not only predict new properties but also reveal insight into the series of transitions that define the mechanism, the molecular origin of the unusual 2.2:1 Cl–/H+ stoichiometry, and the influence of protein orientation. I will explain how the consistent exchange ratio is a consequence of kinetic coupling and how the lack of large protein conformational changes suggests a more facile evolutionary connection between chloride channels and more evolved antiporters. Finally, I will discuss how an ensemble of different stochastic exchange pathways, as opposed to a single series of distinct transitions, culminates in the macroscopic observables and thereby helps to explain the underlying molecular mechanism.
##### Biophysical Dynamics
October 16, 2018
GCIS W301 | Tuesday, 12:00 pm
## Lee Lecture: Professor Susumu Kitagawa, Kyoto University
#### Porous Coordination Polymers/Metal Organic Frameworks
Permanent porosity for coordination networks in solids was discovered and demonstrated with gas sorption experiments (1997), whose materials are now known as porous coordination polymers (PCPs) or metal-organic frameworks (MOFs). They are an emerging class of microporous solids combining the modularity of inorganic structural building units (nodes) with organic ligands (linkers) that can be tailored through organic synthesis. This particular combination of designability and the structural porosity of MOFs has led to explosive growth in their application to gas storage/separation, catalysis, ion conductivity, chemical sensing, and drug delivery systems. To date, MOFs are classified as a new category of porous materials, as opposed to the conventional classifications of inorganic and carbon materials. Researchers in the world synthesized a wide variety of MOFs and developed the comprehensive structural chemistry. We have developed the chemistry of coordination space, focusing on functionalities, and discovered flexible MOFs (soft porous crystals) which to date are another dimension of porous materials.
MOFs have been extensively researched in both academia and industry. Industrial syntheses are rapidly advancing. Researchers in both academia and industry are producing MOFs materials for use in purification, storage, transportation, and conversion, vital to addressing energy and environmental issues and contributing to human welfare.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
October 15, 2018
Kent 120 | Monday, 4:00 pm
## Dr. Christa Flühmann, Department of Physics, ETH Zurich
#### An Encoded Qubit in a Trapped-ion Oscillator
I will present recent experiments demonstrating a qubit encoded in the harmonic motion of a single trapped 40Ca+ ion [1]. The usage of the oscillator allows to study a logical qubit with a single quantum system, while in contrast commonly used error-correction schemes are based on arrays of many physical qubits. The approximate logical code states are formed from a periodically spaced superposition of displaced squeezed components, which has theoretically been shown to have optimal performance for a large set of errors [2, 3]. Our first time demonstration of these qubits is based on coupling the ion motional oscillator to an internal state ancillary qubit, which we can subsequently readout. This indirect readout of the oscillator via the ancillary qubit we have previously interpreted as a modular position or momentum measurement and explored the relations between sequences of these measurements [4]. Such sequences allow us to create the logical codes states as well as measure their spatial and momentum probability densities, revealing the non-local features simultaneously present in both densities. Using the modular measurements we further implement logical state readout in the Pauli basis which we demonstrate on the six cardinal states of the Bloch sphere for which we reach an average square fidelity of 87.3 ± 0.7%. We implement the logical Pauli gates by displacements of the oscillator and realize arbitrary single qubit operations by modifying the modular measurements slightly. We analyze the performance of a universal single logical qubit gate set by performing process tomography, for Pauli gates we reach process fidelities of ≈ 97%, while for continuous rotations we achieve fidelities of ≈ 89%.
##### JFI Special Seminar
October 15, 2018
GCIS E223 | Monday, 3:30 pm
## MRSEC Lunch 'n Learn Workshop
#### HORIBA Duetta Fluorescence and Absorbance Spectrometer
Come see the worlds’ fastest 2 in 1 Fluorescence and Absorbance Spectrometer
Duetta
A Game Changing Spectrometer Concept
• UV-Vis-NIR Fluorescence Detection Wavelength Range from 250 to 1,100 nm
• Full 3-D Fluorescence EEM Acquisition in Less Than One Second
• Best in Class Fluorescence Sensitivity Specification of 6,000:1 RMS for Water Raman
• Automatic Correction for Primary
and Secondary Inner Filter Effects (IFE)
• High Fidelity Molecular Fingerprinting with Unique A-TEEMTM
(Absorbance-Transmittance Excitation Emission Matrix) Technology
• Millisecond CCD Detection of Entire Fluorescence Spectrum
##### MRSEC Workshop
October 12, 2018
ERC 301B | Friday, 11:30 am
## Stephan Meyer
#### Equity, Diversity and Inclusion
##### Physics Colloquium
October 11, 2018
KPTC 106 | Thursday, 4:00 pm
## Paul Oehlmann, Virgina Tech
#### Gauged Superconformal matter from exotic F-theory fibrations
We consider 6 dimensional supergravity theories coupled to gauged superconformal matter. The physics is extracted from F-theory on smooth torus fibered Calabi-Yau threefolds. The superconformal matter resides at points in the base of the fibration that are either smooth, in the case of (1,0) superconformal matter, or orbifold singularities in the (2,0) case.
Smoothness of the the full geometry implies exotic fiber behavior over those points
such as non-flat and multiple fibers that we analyze in detail. The topology of those
fibers and the full geometry allows an interpretation for the superconformal matter which
can be verified by analyzing their deformation spaces.
##### Theory Seminar
October 10, 2018
PRC 201 | Wednesday, 1:30 pm
## Shinsei Ryu, University of Chicago
#### Topology and entanglement detected by partial transpose
Quantum many-body systems exhibit very rich phenomena unexpected from their classical counterparts. In this talk, I will focus on a quantum information theoretical operation -- partial transpose -- which is useful in detecting quantum entanglement. I will describe how partial transpose can be used to detect topology and entanglement in quantum many-body systems, ranging from topological phases of condensed matter to systems which have holographic dual descriptions. In particular, I will describe the constructions of topological invariants using partial transpose, and possible holographic dual objects corresponding to entanglement negativity, which is an quantum entanglement measure constructed by using partial transpose.
##### Computations in Science
October 10, 2018
KPTC 206 | Wednesday, 12:15 pm
## Omrie Ovdat, Technion
#### Vacancies in Graphene: Dirac Physics and Fractional Vacuum Charges
Significant interest has lately been devoted to the study of vacancies in graphene obtained by removing a neutral carbon atom. The presence of a single vacancy has interesting and unexpected consequences. It leads to the occurrence of a stable charge of order unity localized at the vacancy site and interacting with other charges of the conductor by means of an Coulomb potential. It also breaks the symmetry between the two triangular graphene sublattices hence inducing zero energy states at the Dirac point. These features have been noticed, however, their precise underlying mechanism and its relation to Dirac physics, if any, are yet to be investigated. Here we show the fractional and pseudo-scalar nature of this stable vacancy charge originating from the vacuum and insensitive to screening effects. A continuous Dirac model is presented which relates zero modes to vacuum fractional charge and to parity symmetry breaking. This relation, constitutes an Index theorem and is achieved by using particular chiral boundary conditions, which map the vacancy problem onto edge state physics and link zero energy states to topological features of the bulk alike the Hall effect or physics of kinks, vortices and monopoles. Vacancies in graphene thus allow to realize prominent features of $2+1$ quantum electrodynamics, e.g., charge fractionalization and parity breaking, but without coupling to a gauge field.This essential difference makes vacancy physics relatively easy to implement and an interesting playground for topological charge switching.
October 9, 2018
PRC 201 | Tuesday, 4:00 pm
## JFI Tuesday Seminar - Prof. Jean Dalibard - College de France
#### Topological Protection in Quantum Gases
How can one classify the states of matter? Beyond well-known
arguments based on geometrical symmetries, the application of concepts
originating from topology is currently leading to fascinating
developments. These concepts were initially proposed in condensed matter
physics in order to describe the Quantum Hall effect, and they are now
spreading over many fields of research, notably in atomic physics and
optics. In this lecture, I will present some robust properties that
characterize topological matter formed with atomic gases, which persist
when one modifies the system parameters or add some disorder. I will
also explain how these concepts can lead to novel devices that take
advantage of topological robustness. Host: Cheng Chin, 2-7192 or via email to cchin@jfi.uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The Tuesday JFI Seminar
October 9, 2018
GCIS W301 | Tuesday, 4:00 pm
## Nathan Seiberg, IAS
#### Recent advances in 2+1d QFT
We will review recent developments in the study of quantum field theory in 2+1 dimensions. Newly discovered subtleties in the analysis of the short distance behavior of these theories have uncovered surprising properties. They help motivate a rich web of conjectures about the long distance behavior of these systems. These conjectures describe new phases and new phase transitions between them. Also, in many cases these transitions have several different dual descriptions. These new developments were motivated by ideas in high energy physics, string theory, and condensed matter physics. And they have potential applications in these fields.
October 9, 2018
PRC 215 | Tuesday, 1:30 pm
## Chemistry Colloquium: Professor Masaru Kuno, University of Notre Dame
#### Single Semiconductor Nanostructure Extinction Spectroscopy
There has been thirty years of emission-based single particle microscopy and spectroscopy since Moerner’s seminal single molecule study. While highly successful in revealing the properties of matter hidden by ensemble averages, the limits of emission-based microscopies have now become apparent. To address recognized future needs and, in particular, the need to go beyond fluorescent specimens, single particle extinction techniques have been developed. Motivating this has been the desire to acquire information about the electronic structure of nanoscale materials difficult to obtain otherwise using either ensemble or emission-based single particle measurements. Circumstances where single particle extinction measurements offer superior alternatives to traditional microscopies/spectroscopies include situations where the material of interest is non-emissive or where current syntheses yield ensembles with large size and/or compositional distributions that hide the underlying spectral response of a material. Most relevant, though, are cases where information about the underlying electronic structure of a material -something directly encoded in its absorption- is less forthcoming and is at best inferred indirectly using emission-based approaches.
This talk describes the inherent problems associated with measuring the extinction of low dimensional semiconductors. It simultaneously describes the fundamental operating principles of two common extinction techniques while highlighting their achievements. It then reviews what exactly we have learned about the fundamental physics of CdSe, a model semiconductor nanosystem. The talk ends by describing the future development of new single particle extinction methodologies such as infrared photothermal heterodyne imaging.
##### Chemistry
October 8, 2018
Kent 120 | Monday, 4:00 pm
## Inorganic/Organic Seminar: Professor Keary Mark Engle, The Scripps Research Institute
#### Catalytic Methods for Selective Functionalization of C–C π-Bonds
Vicinal (1,2-disubstituted) functional group motifs are ubiquitous in structurally complex small molecules that are of academic and industrial importance, including many widely used pharmaceutical agents. Many such functional group combinations, however, remain exceptionally challenging to synthesize. The goal of research in the Engle lab is to develop a general catalytic platform for alkene and alkyne difunctionalization to introduce a diverse array of functional groups at each of the two carbon atoms in a programmable fashion. Our central hypothesis is that is that coordination of a π-Lewis acidic metal, such as palladium(II), to the alkene will promote nucleophilic attack and that the resultant organometallic species can be trapped with an electrophile to furnish the desired 1,2-difunctionalized product. In the overall net transformation, one of the two new functional groups is introduced in the form of a nucleophile, and the other in the form of an electrophile. Directing groups are used to control the regiochemical course of the reaction and stabilize key alkylmetal intermediates. These concepts have been used to expand the synthetic toolkit to include new retrosynthetic disconnections, including “homo-Michael” addition and β,γ-vicinal dicarbofunctionalization of alkenyl carbonyl compounds.
##### Chemistry
October 5, 2018
Kent 120 | Friday, 1:15 pm
## David Schimitz, University of Chicago
#### Neutrino Physics at Long and Short Baselines: The DUNE and SBN Experiments at Fermilab
The study of neutrinos over the past 60 years has revealed an incredible amount about the Standard Model of elementary particles, despite neutrinos being one of the most challenging areas of exploration in particle physics. This combination, a seeming contradiction, motivates continued experimental effort at a grand scale to reveal the neutrinos’ further secrets. One of the global centers of neutrino physics research is at Fermilab, forty miles west of campus, which hosts the future Deep Underground Neutrino Experiment, DUNE, and the ongoing Short-Baseline Neutrino experiment, SBN. In this talk, I will review some of the biggest past discoveries in neutrino physics and preview the exciting future ahead with these new experiments at unprecedented scales and with world-leading reach for new discoveries.
##### Physics Colloquium
October 4, 2018
KPTC 106 | Thursday, 4:00 pm
## Xiao Chen, KITP, UC Santa Barbara
#### Operator dynamics and quantum chaos: an approach from Brownian circuit
Operator scrambling is a crucial ingredient of quantum chaos. Specifically, in the quantum chaotic system, a simple operator can become increasingly complicated under unitary time evolution. This can be diagnosed by various measures such as square of the commutator (out-of-time-ordered correlator), operator entanglement entropy etc. In this talk, we discuss operator dynamics in three representative models: a 2-local spin model with all-to-all interaction, a chaotic spin chain with long-range interactions, and the quantum linear map. In the first two examples, we explore the operator dynamics by using the quantum Brownian circuit approach and transform the operator spreading into a classical stochastic problem. Although the speeds of scrambling are quite different, a simple operator can eventually approach a "highly entangled" operator with operator entanglement entropy taking a volume law value (close to the Page value). Meanwhile, the spectrum of the operator reduced density matrix develops a universal spectral correlation which can be characterized by the Wishart random matrix ensemble. In contrast, in the third example (the quantum linear map), although the square of commutator can increase exponentially with time, a simple operator does not scramble but performs chaotic motion in the operator basis space determined by the classical linear map. We show that once we modify the quantum linear map such that operator can mix in the operator basis, the operator entanglement entropy can grow and eventually saturate to its Page value, thus making it a truly quantum chaotic model.
October 4, 2018
PRC 215 | Thursday, 2:30 pm
## Special Seminar: Professor Li Deng, Brandeis University / Westlake University
#### Activation of Nucleophiles for Asymmetric Reaction with Organic Molecules
Organic molecule-mediated selective catalysis (i.e. selective organocatalysis) has evolved into a generally applicable, powerful strategy for asymmetric synthesis over the past few years. This lecture will present synthetic and mechanistic studies focusing on the development of weak-bonding organocatalysis directed towards the activation of nucleophiles for realizing asymmetric transformations of synthetic importance.
##### Chemistry
October 4, 2018
GCIS W301 | Thursday, 2:30 pm
## Marija Vucelja, University of Virginia
#### Adaptation of a bacterial population and the adaptive immune system of bacteria with CRISPR
The CRISPR (clustered regularly interspaced short palindromic repeats) mechanism allows bacteria to defend adaptively against phages and other invading genomic material. The CRISPR machinery acquires short genomic sequences from the "invaders" and in this way builds up a memory of past infections. With a new encounter of an invading sequence, this memory is accessed, and in a successful outcome, the invader is neutralized. I will introduce a population dynamics model where immunity can be both acquired and lost. I will describe the predictions of this model and suggest experiments.
Adaptation, where a population evolves increasing _x000C_fitness in a fixed environment is often thought of as a hill climbing process on a _x000C_fitness landscape. With a fi_x000C_nite genome, such a process eventually leads the population to a _x000C_fitness peak, at which point _x000C_fitness can no longer increase through individual beneficial mutations. Instead, the ruggedness of typical landscapes due to epistasis between genes or DNA sites suggests that the accumulation of multiple mutations can allow the population to continue increasing in _x000C_fitness. By using a spin-glass type model for the _x000C_fitness function that takes into account microscopic epistasis, we _x000C_find that hopping between metastable states can mechanistically and robustly give rise to a slow, logarithmic average _x000C_fitness trajectory.
##### Computations in Science
October 3, 2018
KPTC 206 | Wednesday, 12:15 pm
## IME Distinguished Colloquium Series - Arup Chakraborty
Professor Arup Chakraborty from Massachusetts Institute of Technology will kick off the IME Distinguished Colloquium Series with an hour-long talk.
##### Molecular Engineering
October 3, 2018
ERC 161 | Wednesday, 11:00 am
## 1st Tuesday Colloquium - Prof. David DeMille, Yale University
#### Diatomic Molecules as Quantum Tools
Our group is pursuing a wide range of physics goals, by applying techniques of modern atomic physics to the more complex system of diatomic molecules. For example, we use the strong electric field inside a polar molecule to amplify the observable effect from an electric dipole moment (EDM) of the electron, a CP-violating effect predicted in many extensions to the Standard Model of particle physics. We recently set a new upper limit on the electron EDM, placing severe bounds on many models of new physics at the TeV energy scale. In parallel, our group has developed the first methods for laser cooling and trapping of molecules. These techniques will enable interesting new frontiers in quantum many-body physics and quantum chemistry, as well as next-generation EDM searches. Host: Cheng Chin, 2-7192 or via email to cchin@jfi.uchicago.edu. Persons with a disability who may need assistance please contact Brenda Thomas at 2-7156 or by email at bthomas@uchicago.edu.
##### The 1st Tuesday JFI Colloquium
October 2, 2018
GCIS W301 | Tuesday, 4:00 pm
## Tobias Walther, PhD, Harvard
#### The Phase of Fat: Mechanisms & Physiology of Lipid Storage
##### Biophysical Dynamics
October 2, 2018
GCIS W301 | Tuesday, 12:00 pm
## Stuck Inside a Protein With the Deformation Blues Again
Noon is when we eat and laugh and talk
12:15 is when the subject is revealed
##### MRSEC Baglunch
September 28, 2018
GCIS E123 | Friday, 12:00 pm
## Dr. Quentin Ficheux, Ecole Normale Superieure
#### Dynamics of a Qubit while Simultaneously Monitoring its Relaxation and Dephasing
Measuring a spin-1/2 along one direction projectively maximally randomizes the outcome of a following measurement along a perpendicular direction. Here, using either projective or weak measurements, we explore the dynamics of a superconducting qubit for which we measure simultaneously the three components x, y and z of the Bloch vector.
The x and y components are obtained by measuring the two quadratures of the fluorescence field emitted by the qubit. Conversely the z component is accessed by probing an off-resonant cavity dispersively coupled to the qubit. The frequency of the cavity depends on the energy of the qubit and the strength of this last measurement can be tuned from weak to strong in situ by varying the power of the probe.
In this experiment, the tracked system state diffuses inside the Bloch sphere and performs a random walk whose steps obey specific rules revealing the backaction of incompatible quantum measurements. The associated quantum trajectories follow a variety of dynamics ranging from diffusion to Zeno blockade. Their peculiar dynamics highlight the non trivial interplay between the backaction of the two aforementioned incompatible measurements.
##### JFI Special Seminar
September 27, 2018
GCIS E123 | Thursday, 11:00 am
## Frontiers of Molecular Engineering
Join us in Chicago to discover how molecular engineering approaches are driving significant breakthroughs across a broad range of research disciplines and applications, from batteries to biotechnology, and learn of the key challenges for the future. Attendees will be exposed to the current state of the art across diverse areas of research, with an emphasis on the development of an interdisciplinary approach.
This two-day symposium is supported by Molecular Systems Design & Engineering, The Institution of Chemical Engineers (IChemE), the National Science Foundation (NSF), and the Institute for Molecular Engineering at the University of Chicago.
The programme will feature invited speakers plus a poster session.
Topics will include:
Energy storage and conversion
Biotechnology
Computational material design
Capture and separations technologies
Assembly of soft and biological materials
Catalysis
Machine learning and data science in material design
##### Molecular Engineering
September 27, 2018
ERC 161 | Thursday, 9:00 am
## Lorenz Eberhardt, ETH
The purpose of the talk is twofold. I will first report on progress made on the problem of finding a holographic dual of the large N=4 background AdS3xS3xS3xS1. I will discuss the BPS spectrum of the background in detail, both from a string theory and a supergravity point of view. This allows us to make a proposal for the CFT dual, at least for specific values of the fluxes.
In a second part of the talk, I will discuss the string theory spectrum on AdS3 backgrounds away from the pure NS-NS flux point, where a WZW description of the worldsheet theory exists. The theory with R-R flux can be described in the hybrid formalism by a sigma-model on a supergroup coupled to ghosts. I will explain how to solve this sigma-model in the plane-wave limit and reproduce the plane-wave spectrum from the hybrid formalism
##### Theory Seminar
September 26, 2018
PRC 201 | Wednesday, 1:30 pm
## Professor Yoon-Young Kim, Seoul National University
#### Total Longitudinal-Transverse Mode Conversion through Anisotropic Elastic Metamaterials
Professor Yan Yoon’s research is focused on elastic metamaterials and mechanics-based design and optimization. His research has been recognized with many awards including, most recent awards, Seoul National University Award for Academic Excellence (2017), KSCM (Korean Society for Computational Mechanics) Computational Mechanics Award (2017), APACM (Asian-Pacific Association for Computational Mechanics) Award for Computational Mechanics (2016), and ASSMO (Asian Society for Structural and Multidisciplinary Optimization) Award (2016). He has also given a number of keynote/plenary lectures in international conferences, including recent plenary lectures at the World Congress of Computational Mechanics (2016), World Congress of Structural and Multidisciplinary Optimization (2017) and the International Conference on Emerging Technologies in Mechanical Engineering (2018).
Elastic waves in solids carry both longitudinal and transverse waves. The particle motions in the longitudinal and transvere modes take place along the parallel and perpendicular directions to the direction of propagation, respectively. Their propagation speeds are also different due to the difference in their impedances. Therefore, no longitudinal (transverse) mode can be totally converted to the transverse (longitudional) mode unless the wave propagation direction is allowed to alter. Here, we show that the unidirectional total mode conversion from the longitudinal mode to the transvese mode (and vise versa) is possible if our elaborately designed anisotropic metamaterial converter is used. As a critical application of the discovered phenomenon of total mode conversion that is enabled by a metamaterial, we will present new-generation ‘ultrasonic non-invasive flow sensors’ that clamp to the outside of a fluid-flowing pipe. We will show how the new sensors can overcome the technical limiations of currently available flow sensors.
Prof. Yoon led the National Creative Research Initiatives Centers designated by the Korean Ministry of Science and Technology from 2002 to 2011. He was the President of the KSME (Korean Society of Mechanical Engineers) and is the President of the KSCM (Korean Society for Computational Mechanics). He is also a Vice-President of the ISSMO (International Society of Structural and Multidisciplinary Optimization) and the President of the ASSMO (Asian Society of Structural and Multidisciplinary Optimization). He (has) served as editors in several international journals. He is a member of KAST (Korean Academy of Science and Technology) and a member of NAEK (National Academy of Engineering), Korea. He also works as advisory professors for Samsung Electronics, Samsung Advanced Institute of Technology, and SEMES. He also (has) served as an international board member of KTH (Royal Institute of Technology, Sweden), an external review member of University of Tokyo, RACE, and a foreign review member of Beijing Institute of Technology, the Mechanics Program.
##### JFI Special Seminar
September 25, 2018
GCIS E123 | Tuesday, 4:00 pm
#### Path integrals, finite temperature, and lattices
Surprisingly, partition functions for some model systems in statistical mechanics are invariant under formally reflecting the sign of temperature, T: +T -> -T. We call this T-reflection invariance. Clearly, partition functions for generic statistical systems cannot be invariant under T-reflection. However, in this talk we focus on finite-temperature path integrals and give a general picture for why finite-temperature path integrals in quantum field theory *should* behave well under T-reflection. We probe this general picture in the context of the harmonic oscillators (in one-dimension) and in conformal field theories on the two-torus (in two-dimensions) and in the mathematics of modular forms. We find that the relevant path integrals are often invariant only up to overall T-independent phases, which could be naturally interpreted as new anomalies under large coordinate transforms.
September 25, 2018
PRC 201 | Tuesday, 12:00 pm
## Special Seminar: Professor Thomas Teets, University of Houston
#### Synthetic Strategies to Optimize Photophysical and Photoredox Properties of Organometallic Complexes
This talk describes complementary synthetic approaches to control and enhance the excited-state properties of organometallic complexes. Bis-cyclometalated iridium complexes have emerged as champion compounds in a number of applications requiring efficient phosphorescence and excited-state redox chemistry. Outstanding challenges include the design of compounds with efficient, stable blue luminescence, and overcoming the typically poor photoluminescence quantum yields of red to near-infrared-emitting complexes. Our efforts have resulted in new designs for robust blue-emitting complexes, using strongly σ-donating acyclic diaminocarbene supporting ligands. These complexes are prepared by unconventional routes relying on the electrophilic reactivity of coordinated isocyanides. In a separate effort, we have employed nitrogen-containing, π-donating ancillary ligands in the development of new bis-cyclometalated iridium complexes which are efficient red and near-infrared phosphors or potent photoreductants. And finally, a more recent thrust in our group has produced a modular self-assembly strategy to prepare multi-chromophore arrays featuring cyclometalated iridium, providing easy access to a class of supramolecular constructs which are rich platforms for studying fundamental aspects of excited-state dynamics and may function as ratiometric environmental sensors.
##### Chemistry
September 20, 2018
GCIS W301 | Thursday, 1:00 pm
## Anomalous subdiffusion of highly-charged, membrane-covered nanoparticles
munch bites: 12:00
Crunch bytes: 12:15
##### MRSEC Baglunch
September 14, 2018
GCIS E123 | Friday, 12:00 pm
## Mind the gap: Fluctuations as a mechanism for thickness selection
Eat at noon. Talk at 12:15
##### MRSEC Baglunch
August 31, 2018
GCIS E123 | Friday, 12:00 pm
## My simulated discontinuous shear thickening---a first-order transition?
Eat: noon
Delve: 12:15
##### MRSEC Baglunch
August 24, 2018
GCIS E123 | Friday, 12:00 pm
## Closs Lecture: Professor Jin-Quan Yu, The Scripps Research Institute
#### Enantioselective and Remote C-H Activation Reactions
##### Chemistry
August 13, 2018
Kent 120 | Monday, 4:00 pm
## Professor Yu Zhao, National University of Singapore
#### Catalytic Enantioselective Redox-Neutral Processes for Efficient Chemical Synthesis
The development of economical and selective catalytic processes is essential for the promotion of sustainable chemical synthesis. My research group at National University of Singapore focuses our efforts on the development of catalytic enantioselective redox-neutral transformations to access valuable chiral building blocks in organic synthesis. Such methods have the significant advantage of circumventing the redundant oxidation/reduction steps to reduce waste production in chemical synthesis. In particular, the stereo-convergent preparation of chiral amines and N-heterocycles from readily available racemic alcohols through borrowing hydrogen, and new processes of enantioselective isomerization of alkenyl alcohols will be discussed in details.
##### Chemistry
July 30, 2018
Kent 120 | Monday, 4:00 pm
## Bacteria communication on a glowing film?
Eat: 12:00
Meet: 12:15
##### MRSEC Baglunch
July 27, 2018
GCIS E123 | Friday, 12:00 pm
## We learn from papers, but what can paper learn?
Meet, eat 12:00
Brainy meat 12:15
##### MRSEC Baglunch
July 20, 2018
GCIS E123 | Friday, 12:00 pm
## NAMBU,FANO AND MY FIRST MARCH MEETING ABSTRACT
#### by regular participant James E. Clark
Bring food at 12:00
Talk begins at 12:15
##### MRSEC Baglunch
July 13, 2018
GCIS E123 | Friday, 12:00 pm
## Tuan Tran, Nanyang Technological University
#### Critical conditions for jumping of electrowetting droplets
A droplet resting on a solid surface stretches further with an applied electric field. Turning off the field, the droplet pulls back to its initial state and may jump up from the surface against gravitational force. In this study, we ask and attempt to answer a simple question: What is the condition for such droplets to detach from the surface? We found that the key factors of jumping condition include the friction and pinning effect at the contact line. The friction at the contact line is responsible for most of the viscous dissipation, while contact line pinning acts as an energy barrier to prevent detachment. We propose a simplified model capturing these effects in the jumping condition and provide an experimental validation to the model. The results highlight the crucial role of contact line dynamics in dynamical wetting phenomena.
##### Computations in Science
July 11, 2018
KPTC 206 | Wednesday, 12:30 pm
## Dr. Abhinendra Singh, City College of New York
#### Towards a General Constitutive Model of Dense Frictional Suspensions
The mechanism of shear thickening in dense suspensions has been shown to be consistent with a transition from lubricated rheology, where close interactions between suspended particles take place through a thin liquid film, to a frictional rheology, wherein particles experience frictional contacts. Particle simulations that led to this concept have been successful in quantitatively reproducing the non-Newtonian shear behavior of discontinuous shear thickening suspensions [1].
As a step towards developing a constitutive model for such materials, we extend the method presented by Wyart-Cates [2] for lubricated and frictional rheologies that is applicable to both shear and normal stresses for non-colloidal suspensions and demonstrate the agreement between such a model and the simulation results [3]. Through this approach we develop a flow-state map of this material.
The challenge of extension of this framework for constitutive modeling of colloidal suspensions remains. In order to guide the efforts to tackle this challenge, we examine the role of cohesive forces on the shear rheology of colloidal suspensions. This is achieved through the inclusion of interparticle repulsive and cohesive forces in addition to hydrodynamic and frictional forces that have been present in our particle simulations [4]. These simulations at low to intermediate strength of cohesion show yield stress at low stress, followed by shear thinning and eventual shear thickening at high values of stress. For high strength of cohesion shear thickening is obscured. Including the details about yield stress and shear thinning, an extension to the shear thickening model to cohesive non-Brownian dense frictional suspension is proposed.
##### JFI / IME Seminar
June 25, 2018
ERC 201 | Monday, 12:00 pm
## cell networks that won't make your skin crawl
Bring food 12:00
Listen 12:15
##### MRSEC Baglunch
June 22, 2018
GCIS E123 | Friday, 12:00 pm
## Eun-Gook Moon, KAIST, Korea
#### Topological defects and phase transitions in 2D correlated systems
The Landau paradigm of phase transitions is one of the backbones in critical phenomena. With a Z2 symmetry, it describes the Ising universality class whose central charge is one half (c = 1/2) in two spatial dimensions (2D). Motivated by recent experiments in strongly correlated systems, which show possibilities beyond the Landau paradigm, we propose an exotic universality class of a Z2symmetry breaking transition with c=1. We argue that controlling topological defects may realize the exotic class. In addition to novel critical exponents, we find that the onset of an order parameter may be super-linear in contrast to the sub-linear onset of the Ising class. We argue that a super-linear onset of a Z2 order parameter without breaking a bigger symmetry than Z2 is evidence of exotic phenomena, and our results are applied to recent experiments in phase transitions at pseudo-gap temperatures. If time allows, we discuss topological phase transitions in Kitaev quanatum spin liquids and their signals
June 21, 2018
PRC 201 | Thursday, 1:30 pm
## Professor Kazuaki Ishihara, Nagoya University
#### Rational Design of High Performance Catalysts on Acid-Base Combination Chemistry
##### Chemistry
June 15, 2018
Kent 120 | Friday, 1:15 pm
## You CAN teach an old foam new tricks
#### come and see how
12:00 the seance, with eating
12:15 the main event
##### MRSEC Baglunch
June 15, 2018
GCIS E123 | Friday, 12:00 pm
## 2018 Science@theInterface Symposium
Session 1
10:30-11:30 Joerg Bewersdorf, PhD, Yale University
3D and Multicolor Live-cell Super-resolution Microscopy for Cell Biological Research
11:30-12:00 Marco Allodi, PhD, University of Chicago
Optical Resonance Imaging: an Optical Analog to MRI for Widefield Ultrafast Imaging
12:00-12:45 lunch
Session 2
12:45-1:45 Sara Abrahamsson, PhD, University of California, Santa Cruz
Multi-Focus SIM development for studying transcription and chromatin dynamics
1:45-2:45 Aydogan Ozcan, PhD, University of California, Los Angeles
Deep Learning-enabled Computational Imaging
2:45-3:00 break
Session 3
3:00- 3:30 Xiaolei Wang, PhD, University of Chicago
3D single insulin granule tracking reveals anisotropic dynamics in Beta cells
3:30-4:30 Fei Chen, PhD, Broad Institute
From cells to tissues: Tools for understanding in situ tissue organization
##### Biophysical Dynamics
June 15, 2018
BSLC 109 | Friday, 10:30 am
## JFI Presents - "Women in Chemistry" -Francesca Serra, John Hopkins University
#### Liquid Crystals for Self-Assembly
Soft materials are a promising tool to explore controllable energy landscapes. Liquid crystals, in particular, combine reconfigurability, unique optical properties and the possibility of directing their self-assembly via the bounding surfaces. These fluids with long-range orientational order possess elastic energy and can generate topological defects, two useful tools for assembly. I will show two examples of interplay between liquid crystal confinement and control of assembly. In one setting, microparticles can be precisely directed to desired locations by modulating the orientation of nematic liquid crystals using topography. An undulated boundary generates small elastic distortions in liquid crystals that can precisely direct the motion of colloidal particles and induce a transformation of the topological defect associated to the particle. In my second example, an array of topological defects in nematic liquid crystals is generated by applying an electric field and it is made regular by appropriate patterning of the electrodes. The defect array can thus form a square lattice of defects, regular over several millimeters, and ideal to create tunable optical gratings. For further information please contact the Host, Sara Zinn via email at szinn@uchicago.edu. Persons who has a disability and may need assistance please contact Brenda Thomas at 2-7156 or bthomas@uchicago.edu. Hosted by Women in Chemistry (WIC)
Funded in Part by Student Government
##### JFI Special Seminar
June 12, 2018
GCIS W301 | Tuesday, 4:00 pm
## Stephanie Palmer, The University of Chicago
##### Physics Colloquium
June 8, 2018
KPTC 106 | Friday, 2:30 pm
## Driving creepy repulsive flow
#### (with movies)
Eat 12:00 (before movies)
Talk 12:15
##### MRSEC Baglunch
June 8, 2018
GCIS E123 | Friday, 12:00 pm
## Prof. Zhi Ping (Gordon) Xu, University of Queensland
#### Tailoring Inorganic Nanoparticles for Efficient Cancer Therapy and Imaging
I will first introduce two types of inorganic nanoparticles, i.e. layered double hydroxide (LDH) and lipid-coated calcium phosphate (LCP) nanoparticles, and then demonstrate their high potential as the drug/gene delivery platforms. I will present a few examples to show efficient co-delivery of functional small interfering RNA (siRNA) and anti-cancer drug to cancer cells for the synergic inhibition. I will also talk about our recent results for target delivery of siRNA to treat cancers.
In the second part, I will present our recent research using clay nanoparticles as vaccine adjuvants to promote higher and long-term immune responses against cancer and bacteria. We have noted that LDH is able to readily load model antigen ovalbumin (OVA) and the toll-like receptor ligand CpG together, promote higher levels of specific antibodies, and modulate the immune response from Th2 bias towards the preferred polarity Th1 for anti-cancer purpose. We have found that LDH and hectorite (HEC) nanoparticles as adjuvants to promote stronger and long-lasting immune responses against the infectious bacteria.
In the final part, I will demonstrate the capability of inorganic nanoparticles as positron emission tomography (PET) and magnetic resonance imaging (MRI) contrast agents for cancer imaging and detection.
##### Chemistry
June 7, 2018
GCIS 500B | Thursday, 4:00 pm
## Andrei Tokmakoff, University of Chicago
#### The Ultrafast Structural Dynamics of Protons in Liquid Water
As omnipresent as liquid water is, we still struggle to understand its chemistry at a molecular scale. It is not just a solvent but its rapidly
changing network of hydrogen bonds shapes and changes solutes within it. The conceptual and technical challenges of studying such problems are nowhere more apparent than when investigating the transport of an excess proton in water, since it is only distinguishable as an excess charge imbedded in the liquid. Proton transfer in water has long been attributed to a sequential displacement of protons along a chain of hydrogen bonds, but there is little experimental evidence to describe the solvation structure of this charge defect and how it changes in charge transfer. I will describe research being performed to visualize the molecular dynamics of excess protons in liquid water using new techniques in ultrafast 2D IR spectroscopy.
##### Molecular Engineering
June 7, 2018
ERC 201 | Thursday, 11:00 am
## Raghu Mahajan, IAS, Princeton
#### The Conformal Bootstrap at Finite Temperature
June 4, 2018
PRC 201 | Monday, 1:30 pm
## Dr. Reatha Clark King
#### Distinguished Alumna Lecture
Dr. Reatha Clark King received her early education in a one-room schoolhouse at Mt. Zion Baptist Church. After graduating as valedictorian of Moultrie High School for Negro Youth, she attended Clark College in Atlanta on scholarship, where she earned a double BS in chemistry and mathematics. A Woodrow Wilson Fellowship brought her to the University of Chicago for her MS in Chemistry, which she obtained in 1960. She remained for her PhD under Ole Kleppa, graduating in 1963 with a thesis titled “Contributions to the Thermochemistry of the Laves Phases.” Dr. King then became the first female African American research chemist at the National Bureau of Standards, where she won the Meritorious Publication Award for a paper on fluoride flame calorimetry. In 1968, Dr. King joined York College (CUNY) as a faculty member, eventually becoming associate dean for the Division of Natural Science and Mathematics and associate dean for academic affairs. She earned an MBA from Columbia College during a sabbatical. In 1977, Dr. King became president of Metropolitan State University in Minneapolis. Her eleven-year tenure in this position is remembered for substantial expansion of the college, as well as increased recruitment of women and minorities. Following a stellar career in research and academia, Dr. King spent the next fourteen years in industry as vice president of General Mills Corporation and President/Executive Director of General Mills Foundation. She has served on the boards of several corporations and nonprofit organizations, including Exxon Mobil, H. B. Fuller, Wells Fargo, Allina Health Systems, and American Council on Education, and has been a trustee of Clark Atlanta University, Carleton College, and the University of Chicago. She has received many awards, including the Defender of Democracy Award from the Martin Luther King, Jr. National Memorial Project Foundation, National Association of Corporate Directors Director of the Year, Exceptional Black Scientist Award from CIBA-GEIGY, International Citizen Award from the International Leadership Institute, Louis W. Hill, Jr. Fellowship in Philanthropy, and Ebony Magazine’s Top 50 Black Executives in Corporate America. She has been inducted into the Delta Sigma Theta sorority for public service and recognized with 14 honorary doctorate degrees.
##### Chemistry
June 1, 2018
GCIS W301 | Friday, 3:30 pm
## Thomas Faulkner, The University of Illinois, Urbana-Champaign
#### Why is negative energy density bad, and how does quantum information constrain it
Negative energy density can arise naturally in Quantum Field Theory, the theoretical framework with which we describe fundamental particle physics and the matter which makes up our universe. However too much negative energy density can lead to pathologies when considering the dynamics of spacetime in which this matter resides. This dynamics is governed by Einstein’s equations which relates such energy densities to the curvature of spacetime. In this talk I will discuss conjectured bounds on negative energy density and sketch very recent general proofs of these bounds. The methods we use combine causality considerations with concepts taken from the study of quantum information.
##### Physics Colloquium
May 31, 2018
KPTC 106 | Thursday, 4:00 pm
## The Tuesday JFI Seminar - Prof. Yan Yu, Department of Chemistry, Indiana University
#### Spatially Organizing Biointerfaces to Interrogate Immune Functions
The immune system functions on the basis of intricately organized chemical reactions and physical forces. Examples range from the engulfment of invading bacteria that relies on a fine balance of competing mechanical forces, to the activation of T-lymphocytes that requires collective interactions between thousands of receptors at the junction between cells. Owing to the complexity of these processes, understanding immune functions using traditional biological tools is highly challenging. In this talk, I will present my group’s research progress towards designing unique biointerfaces to enable the quantitative understanding and manipulation of immune functions. Our research so far has capitalized on Janus particles, which, like the two-faced Roman god Janus, are made chemically, biologically, optically or magnetically asymmetric. We developed Janus particle-based toolsets for measuring cell dynamics in multi-dimensions beyond translational motion and for spatiotemporally controlling cell functions. Using these methods, we uncovered new dynamics and mechanisms in immune processes, from phagocytosis to intracellular trafficking, which would otherwise be difficult to access with traditional means. For further information please contact Brenda Thomas at 773-702-7156 or via email at bthomas@uchicago.edu. You may also contact the Host, Bozhi Tian at 773-702-8749 or via email to btian@uchicago.edu.
##### The Tuesday JFI Seminar
May 29, 2018
GCIS W301 | Tuesday, 4:00 pm
#### MRSEC presents: A Mini Workshop
Presentation: 10:00 a.m. - 10:45 a.m.
Short break
Faculty Panel: 10:45 a.m. - 11:30 a.m.
##### MRSEC Workshop
May 29, 2018
GCIS W301 | Tuesday, 10:00 am
## Grayson L. Jackson, University of Minnesota
#### Nanoconfined Water and Water-mediated Ion Transport in Model Membrane Materials
The ill-defined pore morphologies and connectivities of conventional membrane materials have hampered a clear understanding of the relationship between pore geometry, pore interfacial chemistry, and ultimate membrane performance. Derived from the self-assembly of ionic amphiphiles in concentrated aqueous media, lyotropic liquid crystals (LLCs) are a well-defined materials platform for uncovering these fundamental membrane structure-property relationships due to their monodisperse, sub-3 nm pores decorated with amphiphile headgroup chemical functionalities (Figure 1). Beyond fundamental studies, network (N) phase LLCs are coveted for membrane applications by virtue of their co-continuous aqueous and hydrocarbon domains, yet their non-constant mean curvature interfaces limit their thermodynamic stabilities. In this presentation, I will describe our efforts to understand how pore diameter and interfacial curvature (concave or convex) affects H+ transport in LLCs formed by sulfonate amphiphiles, which unexpectedly reveal that convex nanopores have significantly higher H+ conductivities. Complementary quasielastic neutron scattering (QENS) studies of the confined water dynamics in LLCs with convex nanopores indicate that water diffusion depends sensitively on nanopore geometry and interfacial esults suggest that proton exchange membranes (PEMs) with convex nanopores may exhibit enhanced performances.
##### JFI Special Seminar
May 25, 2018
GCIS E223 | Friday, 3:00 pm
## Christopher Uyeda, Purdue University
#### Catalysis at Metal–Metal Bonds
The discovery of new catalysts is central to the pursuit of more efficient and sustainable processes in organic synthesis. Whereas mononuclear transition metal complexes have been widely utilized in reaction methodology, the scope of both stoichiometric and catalytic processes for complexes of higher nuclearity is comparatively limited. In principle, multinuclear complexes might engage in unprecedented modes of reactivity by binding substrates or engaging in redox processes that span multiple metal centers. New classes of catalysts that can capitalize on these cooperativity effects have the potential to exhibit activity or selectivity profiles that complement or surpass existing mononuclear systems.
Our group has been developing new platforms that support coordinatively unsaturated and reactive metal–metal bonds. In pursuit of this goal, we have developed a naphthyridine–diimine ligand that was used to prepare dinuclear complexes of mid-to-late first-row transition metals. The redox-active nature of these ligands imparts rich redox chemistry to these complexes, enabling an array of multielectron oxidation and reduction reactions. The applications of these complexes to catalytic processes relevant to organic synthesis will be presented.
Persons with a disability may call (773) 702-0388 in advance for assistance.
##### Chemistry
May 25, 2018
Kent 120 | Friday, 1:15 pm
## Rudolf Grimm, The University of Innsbruck
#### Impurities in an ultracold Fermi sea: Quasiparticles, phase separation, and more
Impurity physics has emerged as a new branch of research in the field of atomic quantum gases. A central feature is the wide tunability of interactions between the impurities and the surrounding medium. By using magnetically controlled Feshbach resonances, regimes of strong interactions can be reached, which reveal intriguing many-body physics. After a general introduction into the field, I will present our experiments on fermionic and bosonic potassium impurities immersed in a deeply degenerate Fermi sea of lithium atoms. For fermionic impurities, we study the spectrum of quasiparticle excitations and the regime where the Fermi-liquid picture breaks down. Moreover, we observe the formation dynamics of quasiparticles in real time. For bosonic impurities, we observe small-sized Bose-Einstein condensates and, for strong repulsive interactions, their phase separation from the Fermi sea. If time permits, I will also introduce a new quantum gas mixture (dysprosium and potassium) with great prospects for future research on fermionic quantum gases.
##### Physics Colloquium
May 24, 2018
KPTC 106 | Thursday, 4:00 pm
## Charles M. Lieber, Harvard University
#### Nanoelectronic Tools for Brain Science
Nanoscale materials enable unique opportunities at the interface between the physical and life sciences, for example, by integrating nanoelectronic devices with cells and/or tissue to make possible bidirectional communication at the length scales relevant to biological function. In this presentation, I will overview a new paradigm for seamlessly merging nanoelectronic arrays and circuits with the brain in three-dimensions (3D). First, the design consideration of matching structural, mechanical and topological characteristics of neural probes and brain tissue will be discussed, thus leading to the new concept of tissue-like mesh electronics. Second, quantitative time-dependent histology studies demonstrating the absence of a tissue immune response on at least a year time-scale, as well as interpenetration of neurons and neurofilaments through the open mesh electronics structures will be presented. Third, uniquely, stable electrophysiology data demonstrating the capability to track and stably record from the will describe several current directions of research, including studies that push the limits of the mesh design paradigm and work focused on fundamental brain science problems, including aging and vision. Finally, the opportunities for future developments will be discussed.
##### Chemistry
May 24, 2018
GCIS W301 | Thursday, 4:00 pm
## Louise Berben, University of California, Davis
#### Redox Chemistry of Al(III) Metal-Ligand Complexes
In this talk I will describe the chemistry of Group 13 metal complexes with redox-active ligands. The synthesis and characterisation of iminopyridine and bis(imino)pyridine complexes of Al(III), Ga(III) and In(III) will be described along with a presentation of their structural and electronic properties. Bis(ligand) complexes of Al, Ga and In are each shown to undergo five reversible electron transfer events and each of the charge states have been structurally characterized. Using techniques including EPR and NIR spectroscopy, we characterized the mixed-valent states for each complex and characterize them as Class III, fully delocalized (Al), and Class II/III (Ga and In). The lowered electronic coupling in complexes of the heavier Group 13 elements arises from involvement of a three-state MV system where the unpaired electron spends more time on the Group 13 ion. The reactivity of the Al complexes will also be discussed in detail, including the mechanisms for ligand-based proton transfer that mediate the activation of polar bonds such as those in alcohols and amines. Dehydrogenation reactions are initiated by the bond activation reactions and these include the conversion of formic acid into CO2 and H2 and the conversion of benzylamine into imine with loss of H2 and NH3. Ligand-based proton and electron transfer is also promoted by various redox active ligands supported by Al. Control of the electrocatalytic mechanism for H2 evolution, based on ligand design, will be described.
##### Chemistry
May 24, 2018
Kent 120 | Thursday, 1:00 pm
## Niall M. Mangan, Northwestern University
#### Identification of Hybrid Dynamical Systems via Clustering and Sparse Regression
Inferring the structure and dynamical interactions of complex systems is critical to understanding and controlling their behavior. Hybrid systems are challenging to identify because the parameters and equation structure may change across multiple dynamical regimes. Key examples include varying transmission rates in epidemiological problems and legged locomotion. Many current methods focus on inferring a model for the system and detecting switching points in a time-centric framework. One can reframe the problem by clustering in data-driven coordinates, such that similar dynamical behavior is close together, and then use the sparse identification of nonlinear dynamics (SINDy) method to identify different dynamical regimes. I will discuss model selection using SINDy and information criteria. I will then demonstrate the success of the method hybrid-SINDy on a spring-mass model and a simple infectious disease model with time-dependent transmission rates. I will also investigate robustness to noise and cluster-size.
##### Computations in Science
May 23, 2018
KPTC 206 | Wednesday, 12:15 pm
## Debanjan Chowdhury, MIT
#### Towards a universal description of non-Fermi liquid metals with critical Fermi surfaces
Numerous strongly correlated materials display non-Fermi liquid properties over a broad range of temperatures. One of the remarkable features observed in many of these systems is the apparent universality of the phenomenology, in spite of the completely distinct microscopic details. Inspired by the rich phenomenology of such non-Fermi liquids, I will construct examples of translationally invariant solvable models of metals, composed of lattices of Sachdev-Ye-Kitaev dots with identical local interactions. These models display crossovers as a function of temperature into regimes with local quantum criticality and non-Fermi liquid behavior. I will show the existence of sharply defined critical Fermi-surfaces in the non-Fermi liquid regime, that give rise to quantum oscillations in the magnetization as a function of an external magnetic field, in the absence of quasiparticle excitations. I will discuss the implications of these results for fundamental bounds on relaxation rates and speculate on possible coarse grained descriptions of a class of intermediate scale non-fermi liquid behavior in generic correlated metals.
May 22, 2018
PRC 201 | Tuesday, 1:30 pm
## Stefano di Talia, PhD, Duke Medical Center
#### Cell cycle synchronization in development and regeneration
##### Biophysical Dynamics
May 22, 2018
GCIS W301 | Tuesday, 12:30 pm
## Valeria Molinero, Univesity of Utah
#### ce formation in the atmosphere: a molecular perspective
Crystallization of water in clouds is critical for precipitation and to determine the radiative properties of the atmosphere. Despite decades of research, there are still significant uncertainties in the prediction of the rates of ice nucleation, and about what is the structure of the ice crystals that form under different atmospheric conditions. In this presentation I will discuss our work using molecular simulations and theory to elucidate the microscopic pathways of ice formation, the structure and interfaces of atmospheric ices, and the role of soluble molecules, surfaces, and pores on controlling the rates and mechanisms of ice nucleation.
##### Molecular Engineering
May 22, 2018
ERC 201B | Tuesday, 11:00 am
## Harry Gray, Caltech
#### Living with Oxygen
High-valent iron-oxos are intermediates in biological reactions critical to life on earth, notably including oxygen reduction to water by cytochrome oxidase and steroid oxygenation by cytochrome p450. Jay winkler and i recently discovered that oxygenases and other enzymes that require oxygen for function have chains of tryptophans and tyrosines that extend from active-site regions to protein surfaces. We think it likely that hole tunneling through these trp/tyr chains protects redox enzymes from oxidative destruction.
##### Chemistry
May 21, 2018
Kent 120 | Monday, 4:00 pm
## Sergei Moroz, Technical University Munich
#### Effective field theory of a vortex lattice in a bosonic superfluid
Using boson-vortex duality, we formulate a low-energy effective theory of a two-dimensional vortex lattice in a bosonic Galilean-invariant compressible superfluid. The excitation spectrum contains a gapped Kohn mode and an elliptically polarized Tkachenko mode that has quadratic dispersion relation at low momenta. External rotation breaks parity and time-reversal symmetries and gives rise to Hall responses. We extract the particle number current and stress tensor linear responses and investigate the relations between them that follow from Galilean symmetry. We argue that elementary particles and vortices do not couple to the spin connection which suggests that the Hall viscosity at zero frequency and momentum vanishes in a vortex lattice.
May 21, 2018
PRC 201 | Monday, 1:30 pm
## Mark Lautens, University of Toronto
#### Improving Efficiency Through Catalytic and Multicatalytic Reactions
Oxidative addition and reductive elimination are two fundamental steps common to many different catalytic reactions. Insertion into C-X bonds is particularly prevalent as one of the first steps in a catalytic cycle.
We have been exploring the synthetic potential associated with reversible oxidative addition into carbon-halogen bond and recently developed a palladium catalyzed carboiodination reaction.1 This lecture will describe the scope and limitations of the reaction including recent work that has expanded the scope. 2-3
We have also been exploring the value of combining catalysts and substrates in a multicomponent multicatalyst strategy (MC)2R.4 Recent advances will be presented.
C-H Functionalization remains one of the most active areas of research in organic chemistry.5 We will present our recent advances in this field.
##### Chemistry
May 18, 2018
Kent 120 | Friday, 1:15 pm
## What stops my heavy fluid film from from falling?
12:00 time to eat
12:15 time to ponder
##### MRSEC Baglunch
May 18, 2018
GCIS E123 | Friday, 12:00 pm
## Michel Devoret, Yale University
#### Catching and Reversing a Quantum Jump Mid-flight
The basic phenomenon of quantum jumps between two states of a system driven by a deterministic force while undergoing continuous monitoring is exploited in precision quantum measurements and plays a key role in our fundamental understanding of open quantum systems. Quantum jumps are emblematic of the special nature of randomness in quantum theory. Although it had been argued in the past that their nature is discontinuous, modern measurement theory stipulates that the state of the system evolves continuously during a jump. Even more remakable, in the case of a system possessing at least 3 states, it was shown theoretically that it is possible i) to obtain an advance warning that the jump is about to occur, and consequently ii) to reverse it if was initiated by a coherent drive. We have successfully implemented the indirect QND measurement of a superconducting artificial atom transition from its ground state G to a dark state D by monitoring the occupancy of an auxiliary bright level B connected to G by a Rabi drive. By conditioning the tomography and manipulation of the G-D manifold on the non-occupancy of the B level for a deterministic duration, we catch and even reverse the jump (1). Our experimental results, in agreement with the predictions of quantum trajectories theory with essentially no adjustable parameters, supports the point of view that a single system under continuous, efficient observation can have a time-dependent wavefunction inferred from the record of previous measurements. [1] Z. Minev, S.O. Mundhada, S. Shankar, P. Reinhold, R. Guttierez, R.J. Schoelkopf, M. Mirrahimi, H. Carmichael, M.H. Devoret (2017).
##### Physics Colloquium
May 17, 2018
KPTC 106 | Thursday, 4:00 pm
## Professor Michael L. Neidig, University of Rochester
#### Intermediates and Mechanism in Iron-Catalyzed Cross-Coupling
Despite the increasing development of iron-based catalysts for organic synthesis, a detailed molecular level understanding of these systems has remained largely elusive. This limitation is in stark contrast to palladium chemistry, where detailed studies of active catalyst structure and mechanism have provided the foundation for the continued design and development of catalysts with novel and/or improved catalytic performance. The use of an experimental approach combining advanced inorganic spectroscopies (Mössbauer, magnetic circular dichroism, electron paramagnetic resonance), density functional theory studies, synthesis and kinetic analyses enables the direct evaluation of the active iron species and insight into the mechanisms of catalysis in iron-catalyzed reactions in organic synthesis, including iron-catalyzed cross-coupling. Previous studies from our group using this approach have established the active iron species in iron-bisphosphine catalyzed cross-coupling of mesityl Grignard reagents and primary alkyl halides1 as well as phenyl nucleophiles and secondary alkyl halides.2 Of particular interest are iron-catalyzed cross-couplings with simple ferric salts where we have previously reported the isolation and characterization of [MgCl(THF)5][FeMe4], an intermediate in the reduction pathway of simple ferric salts with methylmagnesium bromide.3 This presentation will focus on recent studies, including the isolation, characterization and reactivity of iron-ate species of relevance to cross-coupling such as [MgCl(THF)5][Fe8Me12],4 as well as recent developments in systems combining iron salts and ligand additives.
##### Chemistry
May 17, 2018
GCIS W301 | Thursday, 1:00 pm
## Douglas Tobias, University of California - Irvine
#### Protein Hydration Water
Proteins present rough, chemically heterogeneous and dynamic surfaces to their surrounding solvent, which for many proteins is primarily aqueous. Roughly a monolayer of water, the so-called "hydration water", is perturbed structurally and dynamically by interaction with a protein molecule. I will present results from experimental and molecular dynamics simulation studies that exemplify the anomalous properties of protein hydration water and reveal differences in the behavior of water near folded soluble proteins, intrinsically disordered proteins, and membrane proteins. Hydration water is crucial for protein function. I will also present both experimental and simulation results that elucidate the mechanism by which functionally important protein motions are coupled to water dynamics. Finally, I will discuss teh nature and range of protein-water collective fluctuations, and the similarities and differences between the dynamics of protein-confined water at ambient temperature and bulk water at low temperature.
##### Molecular Engineering
May 17, 2018
ERC 201 | Thursday, 11:00 am
## Ariel Amir, Harvard
#### From single-cell variability and correlations across lineages to the population growth
Cells of all domains of life must coordinate their cell cycle meticulously in order for protein levels, cell size and DNA replication to be appropriately regulated and to be able to prevent stochastic fluctuations from accumulating over time. These control mechanisms will lead to correlations in various cellular traits across the lineage tree (notably, size and generation times). I will present a recent model we developed for understanding cellular homeostasis and characterizing these correlations and fluctuations. I will discuss the implications of these correlated fluctuations on the population growth. In contrast to the dogma, we find that variability may be detrimental to the population growth, suggesting that evolution would tend to suppress it.
##### Computations in Science
May 16, 2018
KPTC 206 | Wednesday, 12:15 pm
## The Tuesday JFI Seminar - CLOSS LECTURE - Prof. Lauren Webb, Department of Chemistry, University of Texas-Austin
#### Electrostatic and Electrodynamic Fields in Lipid Bilayer Membranes
Lipid bilayer membranes are complex, dynamic, and functional structures composed of a wide diversity of lipids, proteins, small molecules, and water organized in heterogeneous domains through noncovalent interactions. The structure and motion of these molecules generate large electric fields within the interior of the membrane that are critical to membrane structure and function. Here, we describe how vibrational spectroscopy of unnatural nitrile chromophores places throughout the membrane structure is used to measure electrostatic fields in peptides intercalated in free-standing lipid bilayer membranes of increasing chemical complexity. In combination with electrodynamics simulations, these experiments highlight how common small molecules such as cholesterol dramatically affect membrane structure and dynamics through large changes to membrane electric fields.For further information please contact Brenda Thomas at 773-702-7156 or by email at bthomas@uchicago.edu. You may also contact the Host,Sara Massey at chamberlainsc@uchicago.edu.
##### The Tuesday JFI Seminar
May 15, 2018
GCIS W301 | Tuesday, 4:00 pm
## Robert G. Roeder, PhD, Rockefeller University
#### Mechanisms underlying the cooperative functions of transcriptional coactivators
##### Biophysical Dynamics
May 15, 2018
GCIS W301 | Tuesday, 1:30 pm
## Lee Lecture: Professor Peidong Yang, University of California Berkeley
#### CO2 + H2O + Sunlight = Chemical Fuels + O2
Solar-to-chemical (STC) production using a fully integrated system is an attractive goal, but to-date there has yet to be a system that can demonstrate the required efficiency, durability, or be manufactured at a reasonable cost. One can learn a great deal from the natural photosynthesis where the conversion of carbon dioxide and water to carbohydrates is routinely carried out at a highly coordinated system level. There are several key features worth mentioning in these systems: spatial and directional arrangement of the light-harvesting components, charge separation and transport, as well as the desired chemical conversion at catalytic sites in compartmentalized spaces. In order to design an efficient artificial photosynthetic materials system, at the level of the individual components: better catalysts need to be developed, new light-absorbing semiconductor materials will need to be discovered, architectures will need to be designed for effective capture and conversion of sunlight, and more importantly, processes need to be developed for the efficient coupling and integration of the components into a complete artificial photosynthetic system. In this talk I will begin by discussing the challenges associated with fixing CO2 through traditional chemical catalytic means, contrasted with the advantages and strategies that biology employs through enzymatic catalysts to produce more complex molecules at higher selectivity and efficiency. I then discuss a number of different photosynthetic biohybrid systems (PBS) architectures from the last few years, and the numerous strategies to interface biotic and abiotic components. Each demonstrates the advantages of PBSs in converting sunlight, H2O and CO2 into food, fuels, pharmaceuticals, and materials. Finally, I will outline the future of this field, opportunities for improvement, and its role in sustainable living here on Earth, and beyond.
Persons with a disability may call (773) 795-5843 in advance for assistance
##### Chemistry
May 15, 2018
Kent 120 | Tuesday, 12:00 pm
## Lee Lecture: Professor Peidong Yang, University of California Berkeley
#### Semiconductor Nanowire Building Blocks: From Flux Line Pinning to Artificial Photosynthesis
Semiconductor nanowires, by definition, typically have nanoscale cross-sectional dimensions, with lengths spanning from hundreds of nanometers to millimeters. These subwavelength structures represent a new class of semiconductor materials for investigating light generation, propagation, detection, amplification, and modulation. After more than two decade of research, nanowires can now be synthesized and assembled with specific compositions, heterojunctions, and architectures. This has led to a host of nanowire photonic and electronic devices, including photodetectors, chemical and gas sensors, waveguides, LEDs, microcavity lasers, and nonlinear optical converters. Nanowires also represent an important class of nanostructure building blocks for photovoltaics as well as direct solar-to-fuel conversion because of their high surface area, tunable bandgap, and efficient charge transport and collection. In this talk, I will present a brief history of nanowire research for the past two decades and highlights several recent examples in our lab using semiconductor nanowires and their heterostructures for photonic and energy applications.
##### Chemistry
May 14, 2018
Kent 120 | Monday, 4:00 pm
## Bertrand Halperin, Harvard University
#### What's going on at v=5/2?
Recentexperiments have cast doubt on our understanding of the even-denominatorfractional quantized Hall state with quantum number ν=5/2, which was first observed in1987, in GaAs. Based on numerical calculations, it has long been believed thatthe ground state should be topologically equivalent to either the “Pfaffian”wave function, proposed by Moore and Read, or its particle-hole conjugate, the“Anti-Pfaffian”. Though the two states have many common features, and they haveexactly the same energy in a model that ignores perturbations that break theparticle-hole symmetry of a spin-polarized half-filled Landau level, they aretopologically distinct. In particular,their chiral central charge K, whichdetermines the quantized thermal conductance of their edge states, should havedifferent values, viz., K=7/2 and K=3/2, respectively. Recent measurements designed to distinguishbetween these two possibilities point, instead, to a value K=5/2. I shall review somerecent attempts to understand this situation, as well as speculations aboutother even-denominator quantized Hall states observed in various materials.
May 14, 2018
PRC 201 | Monday, 1:30 pm
## SPECIAL JFI Seminar- CLOSS LECTURE - Prof. David Liu, Department of Chemistry & Chemical Biology
#### Base Editing: Chemistry on a Target Nucleotide in the Genome of Living Cells
Point mutations represent the majority of known human genetic variants associated with disease but are difficult to correct cleanly and efficiently using standard genome editing methods. In this lecture I will describe the development, application, and evolution of base editing, a novel approach to genome editing that directly converts a target base pair to another base pair in living cells without requiring DNA backbone cleavage or donor DNA templates. Through a combination of protein engineering and protein evolution, we recently developed two classes of base editors (BE4 and ABE) that together enable all four types of transition mutations (C to T, T to C, A to G, and G to A) to be efficiently and cleanly installed at target positions in genomic DNA. The four transition mutations collectively account for most known human pathogenic point mutations. Base editing has been successfully performed in a wide range of organisms including bacteria, fungi, plants, fish, frogs, mammals, and even human embryos. We have recently expanded the scope of base editing by enhancing its efficiency, product purity, targeting scope, and DNA specificity. We also show that base editing can function in vivo in post-mitotic somatic cells that do not support efficient homology-directed repair. Finally, we have used our phage-assisted continuous evolution (PACE) system to rapidly evolve Cas9 and base editor variants (xCas9, xCas9-BE3, and xCas9-ABE) with both broadened PAM compatibility and higher DNA specificity. Base editing can be used to correct pathogenic point mutations, introduce disease-suppressing mutations, and create cell and animal models of human disease. Host: Chang Liu via email at changliu@uchicago.edu. Persons with a disability who may need assistace please contact Brenda Thomas at 773-702-7156 or by email at bthomas@uchicago.edu
##### JFI Special Seminar
May 11, 2018
GCIS W301 | Friday, 4:00 pm
## Shouheng Sun, Brown University
#### Synthetic Tuning of Nanoparticles to Achieve High Efficiency in Electrocatalysis
Developing highly efficient catalysts is crucial for building practical electrochemical devices for energy conversions and for fuel generation. Here we present a new strategy to control Pt-alloy nanoparticle (NP) catalytic efficiency in acid for highly efficient electrochemical reduction or oxidation reactions.
Using FePt as a model system, we have demonstrated that solid solution structured A1-FePt NPs can be converted to chemically ordered tetragonal L10-FePt NPs. These L10-FePt NPs are not only magnetically hard but also chemically robust against Fe leaching in acid. The fully ordered core/shell L10-FePt/Pt NPs show much enhanced catalysis for not only oxygen reduction reaction (ORR) in 0.1 M HClO4, but also hydrogen evolution reaction (HER) in 0.5 M H2SO4. The concept has been successfully extended to other alloy NP systems. For example, the core/shell L10-CoPt/Pt NPs show even higher activity than the L10-FePt/Pt for ORR, surpassing DOE 2020 targets in both activity and durability. Interestingly, by doping a small percentage of Au into the L10-MPt/Pt, the L10-MPt/PtAu NPs become highly efficient in catalyzing electrochemical oxidation of formic acid, methanol or ethanol without noticeable CO poisoning on the Pt surface. Our studies demonstrate a reliable way of tuning NP core/shell structure to enhance shell catalysis for important energy conversion reactions.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
May 11, 2018
Kent 120 | Friday, 1:15 pm
## Daniel McKinsey, The University of California, Berkeley
#### Probing Sub-GeV Dark Matter with Superfluid Helium
I will describe a dark matter detection technology that will be sensitive to nuclear recoils of sub-GeV dark matter, using superfluid helium as a target. I will briefly review the state of the field of direct dark matter detection, describe motivations to search for sub-GeV dark matter particles and then explain the merits of superfluid helium as a detector material. These include good kinematic matching to low mass dark matter, excellent intrinsic radiopurity, and its unique ability to be cooled down as a liquid to milli-Kelvin temperatures. We propose to read out the recoil signals by calorimetry based on transition edge sensor readout. Calorimeters submerged in the liquid will measure prompt scintillation photons with near-100% efficiency, while the long-lived rotons and phonon excitations will be detected by quantum evaporation of helium atoms from the liquid surface, into vacuum, and then onto a calorimeter array. The binding energy from helium absorption to the calorimeter surface allows for the amplification of these quantum evaporation signals, allowing sub-eV recoil energy thresholds. Taking into account the relevant backgrounds and detector discrimination power based on the light:heat ratio, sensitivity projections show that a small detector (~kg scale) can already explore new parameter space.
##### Physics Colloquium
May 10, 2018
KPTC 106 | Thursday, 4:00 pm
## Daniel Mindiola, University of Pennsylvania
#### Titanium-Carbon Multiple Bonds and Their Roles in the Catalytic Dehydrogenation of Volatile Alkanes and Methane Olefination
##### Chemistry
May 10, 2018
Kent 102 | Thursday, 4:00 pm
## Entrapment into orderly growth
¿Coming soon? Come at noon! to eat.
##### MRSEC Baglunch
May 10, 2018
GCIS E123 | Thursday, 12:00 pm
## Suchitra Sebastian, The University of Cambridge
#### The Emergent Fundamental – Exotic Collective Phenomena in Correlated Materials
n the quest to understand our universe, complex materials comprising billions of interacting electrons provide new insight akin to probing alternative universes. Where elementary excitations are considered the fundamental fabric of our universe, we find exotic phenomena defined by novel collective excitations to emerge in correlated electron systems, offering a glimpse of the new fundamental. I will discuss experimental tools by which we can discover and understand such unconventional phases of matter, in particular by fine-tuning materials universes under extreme conditions such as applied pressure and high applied magnetic fields. I will explore examples from my work on materials families such as copper oxide high temperature superconductors, and dual metal-insulating rare earth systems, which display strikingly unusual emergent physical properties requiring new paradigms of understanding.
##### Physics Colloquium
May 9, 2018
KPTC 106 | Wednesday, 4:00 pm
## Ralf Riedinger, University of Vienna
#### Optical Quantum Control of Mechanical Oscillators
Mechanical memory elements, directly coupled to photons at designed telecom wavelengths, possess many advantageous features as nodes for large area quantum networks. While impressive experiments like ground state cooling and phonon lasing have recently been demonstrated, genuine non-Gaussian optical quantum control thus far remains elusive. In this talk, I will discuss how the non-linearity of single photon detection can be employed to create non-trivial quantum states. I present recent experimental results on the optical generation of single phonon Fock states and remote entanglement of two massive mechanical oscillators, using silicon optomechanical crystals. Our work introduces mechanical memory elements based in silicon photonics as a new resource for future quantum information systems.
##### JFI Special Seminar
May 9, 2018
GCIS E223 | Wednesday, 1:30 pm
## Leigh Orf, University of Wisconsin
#### Simulating and visualizing the most devastating thunderstorms
Tornadoes are among nature's most destructive forces. The most violent, long-lived tornadoes form within supercell thunderstorms. In this seminar, results from simulations of tornado-producing supercell thunderstorms at ultra-high resolution will be presented, as well as the technical challenges involved in conducting, analyzing and visualizing such simulations.
In a control simulation, tornado formation occurs in concert with processes not clearly seen in previous supercell simulations. Visualizations of model fields presented at very high temporal resolution (up to 1/6 of a second, the model time step) will be presented. These animations reveal a fascinating combination of processes that lead to the formation of a long lived very violent tornado that persists for well over an hour. In order to facilitate the saving and visualizing of large amounts of model data, a file system was developed that utilizes the HDF file format and ZFP lossy file compressio! n, and th is file system and associated middleware, dubbed LOFS, will be also described.
##### Computations in Science
May 9, 2018
KPTC 206 | Wednesday, 12:15 pm
## Johannes Jotterbach
#### Unsupervised Machine Learning on the Rigetti Quantum Computer
The fourth tutorial in the Quantum Computing Tutorial Series
##### Molecular Engineering
May 9, 2018
ERC 161 | Wednesday, 12:00 pm
## Nicholas Melosh, PhD, Materials Science & Engineering, Stanford
#### Engineering Inorganic-Biological Interfaces: Nanofluidic Cell Access & Massively Parallel Brain-Machine Interfaces
##### Biophysical Dynamics
May 8, 2018
GCIS W301 | Tuesday, 12:30 pm
## Delia Milliron, University of Texas at Austin
#### Surface Depletion in Conducting Metal Oxide Nanocrystals
Synthetic control over colloidal metal oxide nanocrystals has advanced so that aliovalent dopants can be introduced, producing degenerately doped semiconductors, such as indium tin oxide (ITO), with metal-like optical properties. The localized surface plasmon resonance (LSPR) absorption of these nanocrystals lies in the infrared range, while their large bandgap makes them transparent to visible light. Since the LSPR absorption can be modulated electrochemically, applications including smart windows that dynamically control solar heat gain can be envisioned. I will discuss how the depletion of electron density near the surface of the conducting nanocrystals controls the extent of modulation achievable; material parameters such as dopant concentration and nanocrystal size can be tuned to achieve desirable dynamic response. Depletion also creates a barrier to electron transport between nanocrystals in a thin film. Orders of magnitude enhancement in conductivity of transparent conductive thin films is demonstrated by tuning dopant spatial distribution and nanocrystal surface chemistry to minimize depletion.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
May 7, 2018
Kent 120 | Monday, 4:00 pm
## Katherine A. Schreiber, Purdue University
#### Hydrostatic Pressure Studies of the Second Landau Level of a Two-Dimensional Electron System
The fractional quantum Hallstates are important phases of the two dimensional electron system in galliumarsenide, known for displaying perfect quantization of the Hall resistance. Ofparticular interest are the ν = 5/2 and ν = 7/2 quantum Hall states, predictedto host non-Abelian statistics. However, these states are not yet wellunderstood because they are so fragile, so new and refined experimentaltechniques are required to learn more about them. Hydrostatic pressure appliedto a semiconductor system changes the band structure, so we may use it tochange the energy scales influencing the quantum Hall states. Motivatedtherefore to probe the ν = 5/2 and ν = 7/2 quantum Hall states, we appliedpressure up to 30 kbar to our GaAs sample. Excitingly, we observed apressure-induced phase transition at ν = 5/2 and ν = 7/2 from fractionalquantum Hall state to nematic phase, a spontaneously broken rotational symmetryphase displaying significant resistance anisotropy. This was the first time atransition from a fractional quantum Hall state to nematic phase was observedat ν = 5/2 and ν = 7/2 in a two-dimensional electron system in the absence ofan external symmetry breaking field. The transition appears to be a quantumphase transition that occurs at the same critical magnetic field for both the ν= 5/2 and ν = 7/2 states, suggesting that electron-electron interactions play adominant role as a mechanism for this transition.
May 7, 2018
PRC 201 | Monday, 1:30 pm
## Chi Wu, The Chinese University of Hong Kong
#### Anti-biofouling: How a polymer brush repels proteins and our novel integrated design
Grafting a layer of chains on a surface to form a polymer brush has been considered as an effective approach to make it anti-biofouling (less protein adsorption). The anti-biofouling property has been qualitatively attributed to the hydration of such a polymer brush with a layer of immobile water molecules and the steric effect; namely, the adsorption decreases monotonically as the polymer grafting density (σ) increases. However, there is no quantitative and satisfactory explanation why the adsorption starts to increase when σ is sufficiently high and why polyethylene glycol (PEG) still remains as one of the best to repel proteins. We have looked the captioned question from another angle: the entropic elasticity instead of the protein-surface interaction, i.e., the enthalpy change.
Considering that each grafted chain is confined inside a cylindrical “pore/tube” made of its neighboring chains, as shown in the right figure, we found its optimal length by minimizing its free energy (A) that contains the exclude volume interaction and the chain elasticity (both of them have an entropic nature) [1, 2]; estimated how A depends on σ and the chain length (L); and calculated its thermal energy-agitated chain conformation fluctuation that slows down the adsorption kinetically. After comparing A with the thermal energy, we are able to predict how both L and affect the protein repelling and explain why PEG performs better than others. Our predictions are surprisingly and quantitatively comparable with those literature results [3, 4].
We will also illustrate how to develop some novel anti-biofouling coatings for shipyard/marine applications by using an integrated design that combines different existing strategies; namely, the self-polishing, the self-structure and the self-generated soft and dynamic surface [5, 6].
##### Molecular Engineering
May 7, 2018
ERC 301B | Monday, 11:00 am
## Ming-Yu Ngai, Stony Brook University
#### Development of Novel Chemical Tools for Accessing Unexplored Chemical Spaces
Synthetic methodologies that allow access to new chemical spaces are of paramount importance to modern drug discovery. Fluorine-containing compounds represent a unique c2hemical space that has caused a fundamental paradigm change in life science research over the past 50 years. There is a significant gap, however, between the needs of the chemical industry and the current methodological efficiency of incorporating fluorinated moieties into organic compounds. To bridge this gap, one of our research programs aims to develop novel reagents and general transformations for the synthesis of fluorinated compounds. In this lecture, I will present our recent efforts to establish mild and operationally simple reactions for the installation of understudied trifluoromethoxy (OCF3) group and polyfluoroalkoxy (ORf) groups into organic molecules. These groups are appealing as they can often enhance molecular efficacy by increasing metabolic stability, promoting binding affinity with targets, and improving cellular membrane permeability of the parent compounds. Nevertheless, due to the lack of general synthetic methods for the introduction of these fluorinated groups, their potential has not been fully exploited in pharmaceutical, agrochemical, and materials applications. Thus, we hope that our research program will allow access to and study of unexplored chemical spaces to aid the discovery and development of new drugs, biocompatible materials, bio-probes, and imaging agents.
##### Chemistry
May 4, 2018
Kent 120 | Friday, 1:15 pm
## Lena F. Kourkoutis, Cornell University
#### New frontiers in cryo-electron microscopy: From Probing Low Temperature Electronic Phases to Processes at Liquid/Solid Interfaces
Scanning transmission electron microscopy techniques have enables direct visualization and quantification of the structure, chemistry and bonding of interfaces, reconstructions, and defects. So far, most efforts in the physical sciences have focused on room temperature measurements where atomic resolution spectroscopic mapping has been demonstrated. For many materials, including those that exhibit electronic and structural phase transitions below room temperature and systems that involve liquid/solid interfaces, measurements at low temperature are required. Operating close to liquid nitrogen temperature gives access to a range of emergent electronic states in solid materials and allows us to study processes at liquid/solid interfaces immobilized by rapid freezing.
In this talk, I will discuss our approach to study two processes at the anode-electrolyte interface in lithium metal batteries (LMBs), uneven deposition of lithium metal leading to dendrite growth and the breakdown of electrolyte to form a “solid-electrolyte interphase” (SEI) layer, processes which result in capacity fade and safety hazards. By combining cryo-electron microscopy with cryo-FIB lift out, we provide nanoscale compositional information about intact SEI layers in cycled LMBs and track local bonding states at interfaces, leading to new insights into SEI and dendrite formation (Figure right).
We further demonstrate sub-Å resolution imaging of crystalline solids at cryogenic temperature, and map the nature and evolution of incommensurate charge order in a manganites. We measure picometer-scale displacive modulations of the cations, distinct from existing manganite charge-order models, and reveal temperature-dependent phase inhomogeneities in the modulations, such as shear deformations and topological defects. At temperatures well below T c phase coherence emerges (Figure left). Using cryo- STEM, the role of the lattice in a variety of low temperature electronic phases can now be quantified with high resolution and precision.
##### Physics Colloquium
May 3, 2018
KPTC 106 | Thursday, 4:00 pm
## IME Distinguished Colloquium Series: Ronald Germain
#### Combining Imaging and Cell-based Systems Analysis to Develop a Deep Understanding of Immunity
Recent advances in genomic, flow cytometric, and imaging technologies have increasingly emphasized highly multiplexed examination of biological systems at the single cell level. Our dynamic and static imaging methods, including newly devised highly multiplex 3D methods, have begun to provide a comprehensive spatiotemporal understanding of immune system operation in situ. A key theme that has emerged from this work is the role of fine grained levels of tissue organization in producing efficient adaptive immune responses from an inherently inefficient, sparse system. Our studies have also revealed that several paradigmatic views of cell behavior are not accurate when examined in vivo, while studies of innate immune myeloid cells have provided new insights into regulation of inflammatory tissue damage. At the system biology level, RNA-seq as well as mass-spectrometric examination of cell state (CyTOF analysis) have led to the putative definition of an increasingly large number of cell subsets, approaching the ‘snowflake’ paradigm of every cell being unique. In this lecture, I will discuss some of the key issues pertaining to the origin of variation in RNA and protein expression among what appear to be members of a single cell subset (e.g., TCR transgenic, naïve, resting CD8+ T cells), how such variation affects cellular responses to stimulation, and how predictable, functional biology emerges in an organism with cells, especially rare members of the adaptive immune system, occupying diverse microstates at any given time. Issues to be discussed include: (i) whether cells respond in an ‘instantaneous’ manner dependent on momentary microstate or integrate signals over time as the state changes to decrease the heterogeneity of response, (ii) whether clustering algorithms applied to RNA-seq data reveal stable differentiated subsets of cells or transient fluctuation in sets of co-regulated genes, and (iii) whether individual cells with multiple receptors whose expression varies in time respond with full integration of multiple signals or if biology emerges from the sum of distinct behaviors of individual cells.
This research was supported by the Intramural Research Program of NIAID, NIH.
##### Molecular Engineering
May 3, 2018
ERC 161 | Thursday, 11:00 am
## Ray Moellering, University of Chicago
#### Integrated Chemical Proteomic Platforms to Probe Metabolic Signaling Across Scales of Space, Time and Reactivity
Biological systems are inherently heterogeneous, both at the molecular level (e.g., encoded proteins existing in distinct posttranslational modification states) and the cellular level (e.g., organization of biomolecules to distinct regions of a cell or distinct cells within a tissue). To understand regulatory mechanisms in these systems under normal or diseased states, we must be able to probe biomolecular function in native environments across scales of space and time. Existing proteomic platforms provide quantitative snapshots of the proteins present in a biological sample, yet these methods typically require homogenization of samples, signal-averaging over thousands-to-millions of cells, and provide no information on protein function. Therefore, innovation in the development chemical probes and technology platforms is needed to study protein activity within complex native environments. In the first part of this talk I will describe the development of new chemical probes and complimentary proteomic technologies to enable quantitative measurements in the proteome in native biological contexts – ranging from subcellular complexes, single cells, primary tissues to live animals. In the second half of this talk I will describe the integration of these platforms to discover new roles for reactive endogenous metabolites as intracellular signals in normal and diseased biological states, as well as the potential to regulate these signals for therapeutic benefit. Both halves of the talk will emphasize the role of these integrated chemical proteomic platforms as a discovery engine to identify novel targets for diagnostic and therapeutic development in human disease.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
May 2, 2018
Kent 120 | Wednesday, 4:00 pm
## Ned Wingreen, Princeton
#### Magic numbers in protein phase transitions
Biologists have recently come to appreciate that eukaryotic cells are home to a multiplicity of non-membrane bound compartments, many of which form and dissolve as needed for the cell to function. These dynamical "condensates" enable many central cellular functions – from ribosome assembly, to RNA regulation and storage, to signaling and metabolism. While it is clear that these compartments represent a type of separated phase, what controls their formation, how specific biological components are included or excluded, and how these structures influence physiological and biochemical processes remain largely mysterious. I will discuss recent experiments on phase separated condensates both in vitro and in vivo, and will present theoretical results that highlight a novel “magic number” effect relevant to the formation and control of two-component phase separated condensates.
##### Computations in Science
May 2, 2018
KPTC 206 | Wednesday, 12:15 pm
## Phillip L. Geissler, PhD, Chemistry, UC Berkeley
#### Driven to distraction: Nonequilibrium fates in biomolecular self-assembly
##### Biophysical Dynamics
May 1, 2018
GCIS W301 | Tuesday, 12:00 pm
## Bloch Lecture: Dr. Carl Decicco, Bristol-Myers Squibb
#### Innovation in Drug Discovery and Promising New Medicines
Developing medicines is a complex process. Recent advances in drug discovery have led to transformational new drugs in cardiovascular disease, hepatitis C, Auto-immunity and the exciting and rapidly advancing field of Immuno-oncology. As we investigate new compounds, we are building off of a growing body of evidence that has accumulated over time, illuminating pathways of disease and providing insight into the optimal drug targets. These breakthroughs are leading to transformational new therapies that are having a profound impact on the lives patients and their families. This lecture will focus on important contributions to medicine from the BMS laboratories.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
April 30, 2018
Kent 120 | Monday, 4:00 pm
## Zlatka Minev, Department of Applied Physics, Yale University
#### To Catch and Reverse a Quantum Jump Mid-Flight
A quantum system driven by a weak deterministic force while under strong continuous energy measurement exhibits quantum jumps between its energy levels. This celebrated phenomenon is emblematic of the special nature of randomness in quantum physics. The times at which the jumps occur are reputed to be fundamentally unpredictable. However, certain classical phenomena, like tsunamis, while unpredictable in the long term, may possess a degree of predictability in the short term, and in some cases it may be possible to prevent a disaster by detecting an advance warning signal. Can there be, despite the indeterminism of quantum physics, a possibility to know if a quantum jump is about to occur or not? In this paper, we answer this question affirmatively by experimentally demonstrating that the completed jump from the ground to an excited state of a superconducting artificial atom can be tracked, as it follows its predictable "flight," by monitoring the population of an auxiliary level coupled to the ground state. Furthermore, we show that the completed jump is continuous, deterministic, and coherent. Exploiting this coherence, we catch and reverse a quantum jump mid-flight, thus preventing its completion. This real-time intervention is based on a particular lull period in the population of the auxiliary level, which serves as our advance warning signal. Our results, which agree with theoretical predictions essentially without adjustable parameters, support the modern quantum trajectory theory and provide new ground for the exploration of real-time intervention techniques in the control of quantum systems, such as early detection of error syndromes.
##### JFI Special Seminar
April 30, 2018
GCIS E223 | Monday, 3:00 pm
## Eric Bergshoeff, University of Goettingen
#### Newton-Cartan Gravity in Action
In the first part of this talk I will give a short review of the frame-independent formulation of Newtonian gravity, called Newton-Cartan Gravity, and explain why there is a renewed interest into non-relativistic gravity in general. In the second part I will discuss, as a particular application, a recent proposal for an Effective Field Theory describing a massive spin-2 mode (the so-called GMP mode) in the Fractional Quantum Hall Effect.
April 30, 2018
PRC 201 | Monday, 1:30 pm
## Timothy Newhouse, Yale
#### Total Synthesis of Neurologically Active Terpenoid Natural Products
This talk will describe the total synthesis of neurologically active terpenoid natural products using novel strategies and methodologies for step-efficient syntheses. Methodological developments in the area of allyl-palladium catalysis will be described in detail that have allowed for alpha,beta-dehydrogenation of a variety of carbonyl compounds. Unique strategies and key retrosynthetic disconnections are guided by computational investigation.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
April 27, 2018
Kent 120 | Friday, 1:15 pm
## Cooperative swirling within cell colonies
We eat our food at noon
We watch swirling at 12:15
##### MRSEC Baglunch
April 27, 2018
GCIS E123 | Friday, 12:00 pm
## Martin Zwierlein, Massachusetts Institute of Technology
#### Strongly Interacting Fermi Gases under the Microscope
Strongly interacting fermions govern the physics of e.g. high-temperature superconductors, nuclear matter and neutron stars. The interplay of the Pauli principle with strong interactions can give rise to exotic properties that we do not even understand at a qualitative level. In recent years, ultracold Fermi gases of atoms have emerged as a pristine platform for the creation and study of strongly interacting systems of fermions. Near Feshbach resonances, such gases display superfluidity at 17% of the Fermi temperature. Scaled to the density of electrons in solids, this corresponds to superfluidity far above room temperature. Confined in optical lattices, fermionic atoms realize the Fermi-Hubbard model, believed to capture the essence of cuprate high-temperature superconductors. In recent experiments on two-dimensional Fermi gases under a microscope, we observe metallic, Mott insulating and band insulating states with single-site, single-atom resolution. The microscope allows for the site-resolved detection of charge and spin correlations, and for a direct measurement of the transport properties of the Fermi-Hubbard model.
##### Physics Colloquium
April 26, 2018
KPTC 106 | Thursday, 4:00 pm
## Martin van Hecke, Leiden Institute of Physics
#### Sequential Mechanical Metamaterials
Ordered sequences of motions govern the morphological transitions of a wide variety of natural and man-made systems, while the ability to interpret time-ordered signals underlies future smart materials that can be (re)programmed and process information. After a short introduction to mechanical metamaterials, we introduce here two novel classes of mechanical metamaterials, that can (1) exhibit sequential output and (2) are sensitive to sequential input. To obtain metamaterials that translate a global uniform compression into a precise multistep pathway of reconfigurations, we combine strongly nonlinear mechanical elements with a multimodal hierarchical structure, and demonstrate multi-step reconfigurations of digitally manufactured metamaterials. To obtain metamaterials that are sensitive to a sequence of mechanical inputs, we introduce the notion of non-commuting metamaterials. Our work aims to establish generic principles for infusing metamaterials with sequential input and output.
##### Computations in Science
April 25, 2018
KPTC 206 | Wednesday, 12:15 pm
## The Tuesday JFI Seminar - CLOSS LECTURE - Prof. Garnet Chan, Department of Chemistry, Princeton University
#### Recent Progress in Quantum Chemistry
I will review some of the recent progress made in my group in quantum chemistry methodology and its applications across a variety of problem areas, including metalloenzyme electronic structure, the precision modeling of materials, and the theory of high temperature superconductivity. If time permits, I will also discuss some recent ideas in the areas of quantum dynamics and quantum algorithms on quantum computers.For further information please contact Brenda Thomas at 773-702-7156 or by email at bthomas@uchicago.edu. You may also contact the Host, Polina Navotnaya at pnavotnaya@uchicago.edu
##### The Tuesday JFI Seminar
April 24, 2018
GCIS W301 | Tuesday, 4:00 pm
## Harkins Lecture: Xiaowei Zhuang, Howard Hughes Medical Institute, Harvard University
#### Illuminating Biology at the Nanoscale and Systems Scale by Imaging
Dissecting the inner workings of a cell requires imaging methods with molecular specificity, molecular-scale resolution, and dynamic imaging capability such that molecular interactions inside the cell can be directly visualized. However, the diffraction-limited resolution of light microscopy is substantially larger than molecular length scales in cells, making many sub-cellular structures difficult to resolve. Another major challenge in imaging is the low throughput in the number of molecular species that can be simultaneously imaged, while genomic-scale throughput is desired for investigating systems level questions. In this talk, I will describe two imaging methods that overcome these challenges and their biological applications. I will first describe STORM, a super-resolution imaging method that overcomes the diffraction limit. This approach allows multicolor and three-dimensional imaging of living cells with nanometer-scale resolution. I will present both technological advances and biological applications of STORM, with focus on recent biological discoveries enabled by STORM. I will then describe MERFISH, a single-cell transcriptome and chromosome imaging method that allows numerous RNA species and genomic loci to be imaged in individual cells. This approach enables mapping of the spatial organization of the transcriptome and genome inside cells and distinct cell types in complex tissues.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
April 23, 2018
Kent 120 | Monday, 4:00 pm
## K.C. Nicolaou, Rice University
#### The Art and Science of Organic Synthesis and its Impact on Biology and Medicine
This lecture will cover advancements in chemical synthesis and their applications to biomedical research. A number of examples of total syntheses featuring cascade reactions and other novel strategies and methods will be presented. The impact of the synthetic strategies and technologies developed in these endeavors on biology and medicine through analogue design, synthesis and biological investigations will also be discussed.
##### Chemistry
April 20, 2018
Kent 120 | Friday, 1:15 pm
## As I Lie Dying: A nanoparticle spins towards its demise
#### It's not as sad as it sounds…
Eat 12:00
Saga: 12:15
##### MRSEC Baglunch
April 20, 2018
GCIS E123 | Friday, 12:00 pm
## Geoff Coates, Cornell University
#### In Pursuit of the Perfect Plastic
Society depends on polymeric materials more now than at any other time in history. Although synthetic polymers are indispensable in a diverse array of applications, ranging from commodity packaging and structural materials to technologically complex biomedical and electronic devices, their synthesis and disposal pose important environmental challenges. The focus of our research is the development of sustainable routes to polymers that have reduced environmental impact. This lecture will focus on our research to transition from fossil fuels to renewable resources for polymer synthesis, as well as the development of polymeric materials designed to bring positive benefits to the environment.
##### Molecular Engineering
April 20, 2018
SCL 240A&B | Friday, 11:00 am
## Rama Ranganathan, The University of Chicago
##### Physics Colloquium
April 19, 2018
KPTC 106 | Thursday, 4:00 pm
## William Dichtel, Northwestern University
#### Rapid Sequestration of Organic Micropollutants From Water Using Porous Cyclodextrin Polymers
Organic micropollutants, such as pesticides and pharmaceuticals, have raised concerns about negative effects on ecosystems and human health. These compounds are introduced into water resources by human activities, and current wastewater treatment processes do not remove them. Activated carbons are the most widespread adsorbents used to remove organic pollutants from water, but they have several deficiencies, including poor removal of relatively hydrophilic micropollutants, inferior performance in the presence of naturally occurring organic matter, and energy intensive regeneration processes. β-cyclodextrin, an inexpensive, sustainably produced derivative of glucose, encapsulates micropollutants in water. We link β-cyclodextrin into permanently porous polymers that bind micropollutants with adsorption rate constants 15 to 200 times greater than competing adsorbent materials. The polymers bind pollutants with high affinity, yet can be easily regenerated and reused. We also recently modified our original polymer design to target perfluorinated compounds such as PFOA, which are environmentally persistent associated with negative effects at trace concentrations.
##### Molecular Engineering
April 19, 2018
ERC 201 | Thursday, 11:00 am
## Alfred Crosby, University of Massachusetts Amherst
#### Materials Mechanics for Impulsive Movement
Nature provides amazing examples of high velocity, high acceleration, impulsive movements that can be repeated numerous times over the course of an organism’s lifetime. Synthetic, or engineered, devices, on the other hand, are often challenged to achieve comparable performance across a wide range of size scales. Common to nature’s examples, including mantis shrimp and trap-jaw ants, is the integration of three essential components for elasticity-assisted movement: an actuator, spring, and latch. Elasticity-assisted motion has been utilized for thousands of years to amplify the power of natural or synthetic actuators; however, the scaling physics of these multi-component systems, especially in light of materials design, have not been widely considered. Here, we discuss our group’s efforts, within a multi-university collaborative team, to lay a foundation for understanding the role that materials properties and structure play in the performance of impulsive systems in nature with an eye toward aiding the development of engineered devices that can overcome current limitations. We first discuss the mechanics of elastic recoil and a set of systematic experiments on a resilin-like synthetic material. The results from this study leads to a common framework for describing the roles of geometry and materials properties for controlling duration, velocity, and acceleration. We then introduce recent advances of using mesoscale polymers, which build upon previously introduced concepts from our group, to develop high rate, large strain, microscale actuators. Collectively, these examples highlight the integrative approach of our group and how we use bio-inspired materials mechanics to inspire new technologies and provide fundamental insight.
##### Computations in Science
April 18, 2018
KPTC 206 | Wednesday, 12:15 pm
## Sriram Kosuri, UCLA
#### Synthetic Approaches to Understanding Biology
I will discuss three projects in our lab where we develop new technologies to allow for the construction and functional testing of large libraries of reporters to explore (1) human genetic variation and splicing, (2) structure/function of antibacterial gene target homologs, and (3) human G-protein coupled receptors.
##### Molecular Engineering
April 18, 2018
ERC 161 | Wednesday, 10:00 am
## Susan Marqusee MD/PhD, UCBerkeley
#### Watching protein folding on & off the ribosome
##### Biophysical Dynamics
April 17, 2018
GCIS W301 | Tuesday, 12:00 pm
## Mulliken Lecture: Professor John P. Perdew, Temple University
#### The SCAN Density Functional: Predictive Power of 17 Exact Constraints
Kohn-Sham density functional theory in principle predicts the exact ground-state energy and electron density of a many-electron system via the solution of self-consistent one-electron Schrödinger equations. Only the exchange-correlation energy as a functional of the density needs to be approximated. For materials discovery, the approximations need to be computationally efficient, predictive, and usefully accurate. The SCAN (strongly constrained and appropriately normed) meta-generalized gradient approximation was constructed to satisfy all 17 known exact constraints that a semi-local functional can satisfy (compared to 11 for the PBE GGA). SCAN is further fitted to appropriate norms, non-bonded systems for which a semi-local functional can be accurate for exchange and correlation separately. SCAN recognizes and provides different GGA-like descriptions for covalent single bonds, metallic bonds, and van der Waals (vdW) bonds. Here I will review the functional itself, along with its long-range vdW extension SCAN+rVV10. I will also review applications to properties of diversely-bonded systems, including ferroelectricity, density and structure of liquid water, crystal structure stability, surface properties of transition metals, and critical pressures for structural phase transitions of semiconductors. The accuracy of SCAN is often comparable to or better than that of a hybrid functional, at lower computational cost and without any fitting to bonded systems.
##### Chemistry
April 16, 2018
Kent 120 | Monday, 4:00 pm
## Jian Kang, National High Magnetic Field
#### Interplay between nematicity and superconductivity in tron-based superconductors
Theiron-based high-Tc superconductors exhibit several remarkable features,including the multi-orbital character and the ubiquity of the nematic phase. One consequence of the multi-orbital Fermi surface isthat the spin-fluctuation mediated pairing interactions are sensitive to theorbital spectral weight at the Fermi surface, leading to several differentpossible gap structures, such as nodeless s±, nodal s±, and d-wave. Focused on the orbital order induced in the nematic phase,I will discuss how the nematic order can manipulate the properties of SC. Ourcalculation shows that not only Tc is enhanced, but moreimportantly, the gap structure becomes a mixture of nearly degenerate s andd-wave states by increasing the external strain. This mixture of s and d wavepairing channels has been recently found in the superconducting phase of thebulk FeSe, when SC occurs deeply insider the nematic phase.
April 16, 2018
PRC 201 | Monday, 1:30 pm
## Poul Nissen, PhD, Aarhus University, Denmark
#### Structure and dynamics of P-type ATPase
Active transport plays a major role in cells. In brain, Na,K-ATPase activity alone accounts for an estimated 40-70% of ATP hydrolysis. Also Ca2+-ATPases of the same P-type ATPase family contribute critically to ion homeostasis in all cell types. These activities are fundamental to life, and malfunction is linked to a range of disorders such as neurological and cardiovascular diseases. Using primarily membrane protein crystallography combined with biochemical and electrophysiological studies, single-molecule FRET, molecular dynamics simulations, modelling, & in vivo models, we have contributed to our growing insight into the mechanistic concepts and functional cycle of the mammalian Na,K-ATPase and Ca2+-ATPase ion pumps. Recently we have also initiated cryoEM studies supported by a large Danish-Swedish cryoEM network, and defined rationales for new X-ray and neutron scattering studies based on the emerging facilities at the MAX IV synchrotron and European Spallation Source in Lund and the European XFEL and Petra3 X-ray sources in Hamburg. Hosted by Benoit Roux and Eduardo Perozo
##### Biophysical Dynamics
April 16, 2018
BSLC 205 | Monday, 12:00 pm
## Wesley A. Chalifoux, University of Nevada
#### Alkyne Annulations: A Toolkit for Accessing Chemical Diversity from Terpenoids to Conjugated Materials
Readily available alkyne-containing compounds are attractive as high-energy starting materials that allow an efficient, step- and atom-economical synthesis of a host of useful chemical products. Alkynes and polyynes can be used as linchpins in multicomponent and tandem reactions to provide rapid access to biologically pertinent terpenoid scaffolds. The alkyne functional group also allows for the facile synthesis of novel nanographenes and contorted – even chiral – polycyclic aromatics. Alkynes even allow for a mild, non-oxidative (non-Scholl) bottom-up synthesis of atomically precise graphene nanoribbons (GNRs). Synthetic achievements in both of these areas (terpenoid scaffolds and carbon-rich materials) will be presented in this seminar.
##### Chemistry
April 13, 2018
Kent 120 | Friday, 1:15 pm
## Transient structured fluctuations in a two-dimensional liquid with shouldered pair interaction
Eat and Kibbitz: 12:00
Hear: 12:15
##### MRSEC Baglunch
April 13, 2018
GCIS E123 | Friday, 12:00 pm
## Heather Knutson, California Institute of Technology
#### Seeking Clues to Explain the Diverse Architectures of Exoplanetary Systems
Over the past two decades ongoing surveys have detected thousands of new planetary systems around nearby stars. These systems include apparently single gas giant planets on short period orbits, closely packed systems of up to 5-6 “mini-Neptunes”, and solar-system-like architectures with either one small planet or no planets interior to 0.5 AU. Despite our success in cataloguing the diverse properties of these systems, we are still struggling to develop narratives that can explain their divergent evolutionary paths. In my talk I will describe two promising new avenues of investigation, including constraints on the compositions of short-period planets and statistical studies of the frequency of outer gas giant and stellar companions in these systems. Taken together, these observations provide important clues that can be used to determine whether or not the observed population of short period exoplanets formed in situ or migrated in from farther out in the disk.
##### Physics Colloquium
April 12, 2018
KPTC 106 | Thursday, 4:00 pm
## Professor Hisashi Yamamoto, Professor and Director of Molecular Catalyst Research Center, Chubu University; Arthur Holly Compton Distinguished Professor Emeritus, The University of Chicago; Professor of Emeritus, Nagoya University
#### From Lewis Acid Catalyst to Catalytic Peptide Synthesis
Catalytic peptide synthesis is the long-standing problems for chemical synthesis. One of the most difficult problems for previous synthesis is that the required activated carboxylic acid which caused 1) the racemization of the product and 2) the equimolar usage of the activated ester unit results significant amounts of side products. These issues result difficult to purify the product from by-products.
Generally, Lewis acid catalyst interacts the basic site of molecule and activates another functional group nearby the activated site. Because of the activation by Lewis acid catalyst, even simple methyl ester is able to be used for the reaction. This activation process will avoid any racemization path since the coordination of Lewis acid to the methyl ester may not be attacked by the amide oxygen intramoleculaly. For the basic site (anchor) of the molecules, we are able to use hydroxyl group or equivalents, such as hydroxyl amine, oxime, or BOC protecting amino groups. Lewis acid catalyst can be used various metal alkoxides such as Ta or Nb alkoxides with 1-10 mol% loading. Generally, the amidation proceeds without using any solvent from room temperature up to 80oC in quantitative yields.
With this simple procedure in hand, we are able to introduce the new amino acid unit to the polypeptide chain in two steps with high yields. The proposed process has huge potential for future drug industry.
##### Chemistry
April 12, 2018
GCIS W301 | Thursday, 1:00 pm
## Thomas Cech, PhD, Chemistry and Biochemistry, University of Colorado Boulder, HHMI
#### Shedding some Light on the Dark Matter of the Genomic Universe
In all of life on Earth, information flows from DNA to RNA to Protein. Thus, RNA has a role as a message, transmitting the information encoded in our chromosomal DNA. LncRNAs (long noncoding RNAs) have long been the “dark matter” of the genome, but they also have active roles in biology, even acting as enzymes (ribozymes). Another lncRNA is found in the telomerase RNP, which extends the DNA at chromosome ends and thereby contributes to genome stability. Finally, the binding of lncRNAs to PRC2 helps regulate epigenetic silencing of gene expression.
##### Biophysical Dynamics
April 11, 2018
BSLC 115 | Wednesday, 2:00 pm
## Ward Lopes, NVIDIA
#### A Careers-in-science discussion with a UChicago Alumnus
Ward Lopes is a Sr. Research Scientist who works on display research. His main research interests are applications of dynamic, computer generated holography and holographic optical elements in virtual-, augmented-, and mixed-reality. Prior 2015, Ward focused on self-assembly processes in soft condensed matter and applications of holography in optical micromanipulation and microscopy. Ward has publications on a variety of topics from nano-scale self-assembly and nanotechnology, bio-physics, holographic optical trapping, laser physics, to measurement techniques in the geosciences. Prior to joining NVIDIA, Ward was a physics professor at Williams College and at Mount Holyoke college, and was the Director of Product Research at Arryx, Inc. While at Arryx, he was awarded the R&D 100 Award by R&D Magazine for the 100 “most technologically significant products introduced into the marketplace” for the BioRyx200 system (a holographic optical trapping system).
##### Careers In Science
April 11, 2018
KPTC206 | Wednesday, 2:00 pm
## Michael Shelley, NYU Courant, Flatiron Institute
#### Active Mechanics in the Cell
Many fundamental phenomena in eukaryotic cells -- nuclear migration, spindle positioning, chromosome segregation -- involve the interaction of often transitory structures with boundaries and fluids. I will discuss the interaction of theory and simulation with experimental measurements of active processes within the cell. This includes understanding the force transduction mechanisms underlying nuclear migration, spindle positioning and oscillations, as well as how active displacement domains of chromatin might be forming in the interphase nucleus.
##### Computations in Science
April 11, 2018
KPTC 206 | Wednesday, 12:15 pm
## The Tuesday JFI Seminar - Prof. Sriram Ramaswamy, Indian Institute of Science
#### Active Soft Matter and Other Stories
Active Matter was formulated to incorporate living materials into the capacious fold of condensed-matter and statistical physics. My talk will discuss the successes of this approach on scales from micrometres to kilometres in living and artificial systems; relate active-matter problems to more familiar nonequilibrium phenomena such as sedimentation; and highlight our recent work on (in)stability, defects, flocking and collective trapping, especially in artificial realisations of collective motility.
For further information please contact Brenda Thomas at 773-702-7156 or via email at bthomas@uchicago.edu. You may also contact the Host, Suri Vaikuntanathun at 773-702-7256 or by email at svaikunt@uchicago.edu.
##### The Tuesday JFI Seminar
April 10, 2018
GCIS W301 | Tuesday, 4:00 pm
## Aron Pinczuk, Columbia University
#### Experimental studies of magnetoroton modes of fractional Quantum hall fluids
Quantum Hall phases are archetypes of the remarkable many-electron physics that emerges in electron fluids under conditions of greatly reduced dimensionality.
Magnetoroton modes are characteristic low-energy excitations that manifest underlying fundamental interactions in fractional quantum Hall fluids.
Inelastic light scattering methods at very low temperatures are experimental venues to study low-lying excitations of quantum Hall fluids. Of particular interest are the
excitation modes that demonstrate novel quantum liquid behavior and that offer insights on unexpected collective responses. Besides magnetorotons, low-lying spin wave modes that probe rotational invariance of spin are of interest here.
This presentation considers inelastic light scattering studies of low-lying excitations that probe intriguing physics of quantum Hall fluids. Early results in the partially populated lowest Landau level, at filling factors n=1/2 and n=1/3, will be reviewed. More recent results considered are observations of excitations of the electron fluids that reside in the partially populated second Landau level (filling factors n=5/2 and n=7/3).
April 9, 2018
PRC 201 | Monday, 1:30 pm
## Lucy Colwell, Department of Chemistry, University of Cambridge
#### Using Evolutionary Sequence Variation to Build Predictive Models of Protein Structure and Function
The evolutionary trajectory of a protein through sequence space is constrained by its function. Collections of sequence homologs record the outcomes of millions of evolutionary experiments in which the protein evolves according to these constraints. The explosive growth in the number of available protein sequences raises the possibility of using the natural variation present in homologous protein sequences to infer these constraints and thus identify residues that control different protein phenotypes. Because in many cases phenotypic changes are controlled by more than one amino acid, the mutations that separate one phenotype from another may not be independent, requiring us to understand the correlation structure of the data. We show that models constrained by the statistics of the multiple sequence alignment are capable of predicting key aspects of protein function. These include (i) the inference of residue pair interactions that are accurate enough to predict all atom 3D structural models; and predictions of (ii) binding interactions between different proteins and (iii) binding between protein receptors and their target ligands.
The challenge is to distinguish true interactions from the noisy and under-sampled set of observed correlations in a large multiple sequence alignment. Current methods ignore the phylogenetic relationships between sequences, potentially corrupting the identification of covarying positions. Here, we use random matrix theory to demonstrate the existence of a power law tail that distinguishes the spectrum of covariance caused by phylogeny from that caused by phenotypic interactions. The power law is essentially independent of the phylogenetic tree topology, depending on just two parameters - the sequence length, and the average branch length of the tree. We demonstrate that these power law tails are ubiquitous in the large protein sequence alignments used to predict contacts in 3D structure, as predicted by our theory, and confirm that truncating the corresponding eigenvectors improves contact prediction. Finally, I will discuss current efforts to further enhance these methods using recent advances in deep learning. Persons with disability who may need assistance please contact Brenda Thomas at 773-702-7156 or by at bthomas@uchicago.edu or Host: Stephanie Palmer, 773-702-0771 or via email at sepalmer@uchicago.edu
##### JFI Special Seminar
April 9, 2018
KPTC 206 | Monday, 12:00 pm
## Sylvia T. Ceyer, Massachusetts Institute of Technology
#### Delving Below and Beyond the Surface
Catalytic surface reactions depend not only on adsorbed species but also on absorbed species. Experiments that document the distinctive reactivity of a H atom embedded in the bulk of a Ni metal catalyst are described. In particular, a H atom emerging from the bulk onto the surface is transiently more energetic by about 24 kcal/mol compared to a H atom adsorbed on the surface. Consequently, it is the reactive species in hydrogenation of adsorbed ethylene and acetylene, respectively, while a H atom adsorbed on the Ni surface is not reactive. These results demonstrate that bulk H is not solely a source of surface bound H in catalytic hydrogenation as proposed 60 years ago, but rather, a reactant with a distinctive chemistry of its own.
In cases where the surface is a reactant rather than a catalyst, a scattering approach has shown two likely origins for the factor of 103 to 104 high etching rate of Si by XeF2 than by F2: significant vibrational excitation of the Si lattice upon initial collision of the massive XeF2, prior to abstraction of the first F atom by Si, and second, the gas phase dissociation of the XeF abstraction product that produces a small fraction of F atoms that are aimed back at the Si surface. This study is a possible example of collisional energy transfer to a surface playing a critical role in the probability of a molecule-surface reaction and is the first documentation of dissociation of a product of a surface reaction in the gas phase.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
April 9, 2018
Kent 120 | Monday, 9:00 am
## Kharasch Lecture: Professor Stephen Buchwald, MIT
#### Palladium-Based Methodology in Imaging and Bioconjugation
We have started to apply methodology related to Pd-catalyzed C-N coupling to the preparation of isotopically labelled compounds for the purposes of imaging (cf. J. Am. Chem. Soc. 2017, 139, 7152). Additionally, we are working in a variety of areas dealing with the functionalization of biomolecules including peptides, proteins and antibodies (Nature, 2015, 526, 687, Org. Lett. 2017, 19, 4263).
This lecture will describe: 1) Our work on the preparation of 11C-labelled small molecules and peptides. 2) The development of technology for the functionalization of peptides and proteins. 3) A new method for the synthesis of stapled peptides. 4) Applications to the preparation of antibody drug conjugates.
##### Chemistry
April 6, 2018
Kent 120 | Friday, 1:15 pm
## How sound makes turtles and trees in mid-air
Come with food at noon
Get ready to fly at 12:15
##### MRSEC Baglunch
April 6, 2018
GCIS E123 | Friday, 12:00 pm
## Michael Brenner, Harvard University
#### The quest to observe the Turbulent Cascade in real time
##### Physics Colloquium
April 5, 2018
KPTC 106 | Thursday, 4:00 pm
## Novartis Lecture: Professor Shannon S. Stahl, University of Wisconsin-Madison
#### Practical Aerobic and Electrochemical Oxidation Reactions
Research in the Stahl lab targets the discovery, development, and mechanistic understanding of new catalysts and catalytic processes, especially related to oxidation reactions. As the most abundant and environmentally benign oxidant available, molecular oxygen is the quintessential oxidant, but controlling its reactivity to achieve selective oxidation of organic molecules presents considerable fundamental and practical challenges. Until recently, aerobic oxidation reactions were virtually never used in process-scale synthesis of fine chemicals, agrochemicals or pharmaceuticals, and they were rarely used in laboratory syntheses. This talk will present a general catalytic strategy for aerobic oxidation reactions, inspired by oxidase enzymes, that is designed to enable widespread use of O2 as an oxidant in chemical synthesis. Fundamental and practical advances in this area will be presented, including highlights of industrial collaborations that have played an important role in these efforts. The "oxidase" approach to aerobic oxidation reactions is conceptually similar to electrochemical redox reactions. Both reaction classes feature the coupling of two independent half-reactions. The aerobic oxidation reactions employ a single catalyst site for both steps, while the electrochemical half-reactions take place at independent electrodes. The relationship between these reactions will be presented, together with recent examples of electrosynthetic oxidation reactions that we have developed.
##### Chemistry
April 5, 2018
GCIS W301 | Thursday, 3:45 pm
## Novartis Lecture: Professor Tianning Diao, New York University
#### Strategies for Promoting Nickel-Catalyzed Alkene Functionalization
Ni catalysts have recently emerged as appealing tools in organic synthesis, allowing access to new reactivity in cross-coupling and opening up new avenues in synthesis. Despite the growing use of Ni catalysts, mechanistic understanding of Ni-catalyzed reactions is inadequate, partly due to complex radical intermediates that complicate mechanistic studies. Our group explores the unique reactivity of Ni catalysts from a fundamental perspective, combining mechanistic approaches with method development. I will present three strategies to tame the reactivity of Ni catalysts. Redox-active ligands stabilize Ni(I) and Ni(III) intermediates and allow classic two-electron transformations to take place on a Ni(I)/Ni(III) platform. In addition, we explored Ni-initiated radical formation from alkyl halides to reductively functionalize alkenes. Finally, we show that dinuclear Ni complexes can react cooperatively, facilitating two-electron redox processes by accepting/donating one electron at each metal center.
##### Chemistry
April 5, 2018
GCIS W301 | Thursday, 3:00 pm
## Novartis Lecture: Professor Mikhail G. Shapiro, California Institute of Technology
#### Molecular Engineering for Non-Invasive Imaging and Control of Cellular Function
The study of biological function in intact organisms and the development of targeted cellular therapeutics necessitate methods to image and control cellular function in vivo. Technologies such as fluorescent proteins and optogenetics serve this purpose in small, translucent specimens, but are limited by the poor penetration of light into deeper tissues. In contrast, most non-invasive techniques such as ultrasound and magnetic resonance imaging – while based on energy forms that penetrate tissue effectively – are not effectively coupled to cellular function. Our work attempts to bridge this gap by engineering biomolecules with the appropriate physical properties to interact with magnetic fields and sound waves. In this talk, I will describe our recent development of biomolecular reporters and actuators for ultrasound. The reporters are based on a unique class of gas-filled protein nanostructures from buoyant photosynthetic microbes. These proteins produce nonlinear scattering of sound waves, enabling their detection with ultrasound. I will describe our recent progress in understanding the biophysical and acoustic properties of these biomolecules, engineering their mechanics and targeting at the genetic level, developing methods to enhance their detection in vivo and expressing them heterologously as acoustic reporter genes. Our actuators are based on temperature-dependent transcriptional repressors, which provide switch-like control of bacterial gene expression in response to small changes in temperature. We have genetically tuned these repressors to activate at thresholds within the biomedically relevant range of 32ºC to 46ºC, and constructed genetic logic circuits to connect thermal signals to various cellular functions. This allows us to use focused ultrasound to remote-control engineered bacteria in vivo.
##### Chemistry
April 5, 2018
GCIS W301 | Thursday, 2:00 pm
## Novartis Lecture: Dr. Katsumasa Nakajima, Novartis Institutes for BioMedical Research
#### Building an Arsenal of Small Molecule DGAT1 Inhibitors to Battle Metabolic Syndrome
Obesity is characterized as excess accumulation of body fat (triglyceride) and contributes to a diagnosis of metabolic syndrome, which is associated with increased risk of cardiovascular disease and diabetes. To battle metabolic syndrome, we initiated a drug discovery program targeting diacylglycerol acyltransferases 1 (DGAT1) which catalyzes the final committed step of triglyceride synthesis. After screening using recombinant human DGAT1 enzyme, diamide and benzimidazole classes of DGAT1 inhibitors were discovered. The diamide compounds were potent DGAT1 inhibitors in vitro but initially lacked suitable molecular properties to inhibit DGAT1 in vivo. Introduction of an aromatic ring as the amide N substituent was found effective to produce an orally bioavailable molecule that potently inhibits DGAT1 in vivo from this series. The benzimidazole series required first optimization of in vitro potency by adding amide and propionic acid groups to the core structure, though these groups kept the molecule from being effectively absorbed in vivo after oral administration. Conversion of the amide to oxadiazole as amide bioisostere and dimethylation at ɑ position in the propionic acid successfully addressed the issue, providing another potent, orally bioavailable DGAT1 inhibitor. This compound demonstrated chronic efficacy by reducing body weight gain in a diet induced obese dog model and was advanced to the clinical investigation along with pradigastat, aminopyridine class of DGAT1 inhibitor that was also developed in our group.
##### Chemistry
April 5, 2018
GCIS W301 | Thursday, 1:15 pm
## IME Distinguished Colloquium Series: Demetri Psaltis, EPFL
##### Molecular Engineering
April 5, 2018
ERC 161 | Thursday, 11:00 am
## Benjamin B. Machta, Princeton University
#### When and why is a simpler model better?
Science is filled with toy models: abstractions of complicated systems that ignore microscopic details even when they are known. For a special class of models in physics, the renormalization group rigorously justifies the use of effective theories containing just a small number of relevant parameters. This philosophy seems to apply more broadly, even when the renormalization group cannot be used. But why? In this talk I will discuss an information theory approach to answering this question, or at least towards quantifying it. I will first review that typical models are sloppy, defined by a hierarchy in parameter importance. I will argue that sloppiness is both necessary and sufficient for a microscopic system to be amenable to description by a simpler effective theory. I will then show how renormalizable models become sloppy as their data is coarse-grained. Finally I will discuss our recent efforts to use the structure of these models to choose simpler effective theories automatically.
##### Computations in Science
April 4, 2018
KPTC 206 | Wednesday, 12:15 pm
## Kharasch Lecture: Professor Stephen Buchwald, MIT
#### Asymmetric Hydrofunctionalization Processes for Organic Synthesis
The availability of a general method for the catalytic conversion of olefins into enantiomerically enriched amines has eluded chemists for decades. We have recently developed a simple copper-catalyzed technique to effect such a transformation. This lecture will describe our progress, applications of our methodology as well as our current view of the mechanism of the hydroamination process. In addition, we will describe our progress in developing new catalytic processes for carbon-carbon bond formation that utilize alkyl copper intermediates.
##### Chemistry
April 4, 2018
GCIS W301 | Wednesday, 12:00 pm
## The JFI First Tuesday Colloquium - Prof. Ignacio Franco, Department of Chemistry, University of Rochester
#### Stark Control of Electrons
A general goal in our quest to control matter and energy is the design of strategies to control electronic properties and electron dynamics using coherent laser sources. In addition to its interest at a fundamental level, lasers permit manipulation on an ultrafast timescale opening the way to control the ability of matter to chemically react, conduct charge, absorb light, or other properties, in a femto to attosecond timescale.
In this talk, I will summarize our efforts to understand electronic decoherence processes in molecules that are deleterious to interference-based scenarios for the laser control. In addition, I will discuss how, through Stark effects, non-resonant light of intermediate intensity (non-perturbative but non-ionizing) can be used to generate “laser-dressed” molecules and materials with non-equilibrium properties that can be very different from those observed by matter near thermodynamics equilibrium. In particular, I will discuss how Stark effects can be employed to turn transparent nanomaterials into broadband absorbers, and to generate currents in nanoscale junctions.For further information please contact Brenda Thomas at 773-702-7156 or via email at bthomas@uchicago.edu. You may also contact the Host: Timothy Berkelbach 773- 834-9879 or by email at berkelbach@uchicago.edu.
##### The 1st Tuesday JFI Colloquium
April 3, 2018
GCIS W301 | Tuesday, 4:00 pm
## Thomas T. Perkins, PhD, JILA & University of Colorado Boulder
#### Probing the equilibrium folding dynamicsof individual bacteriorhodopsin molecules with 1-μs resolution
##### Biophysical Dynamics
April 3, 2018
GCIS W301 | Tuesday, 12:00 pm
## Kharasch Lecture: Professor Stephen Buchwald, MIT
#### Palladium-Catalyzed Carbon-Heteroatom Bond-Forming Reactions for Organic Synthesis
Cross-coupling methodology is an indispensable part of the everyday repertoire of synthetic organic chemists. Among the many possibilities, we have focused a great deal of attention on the Pd-catalyzed formation of C-N bonds (Chem. Rev., 2016, 116, 12564); a mechanistic pathway for this transformation is shown below. This methodology has been widely utilized throughout academia and industry.
Crucial to our success in the development of new and more generally applicable methods has been our discovery and use of biaryl monodentate phosphine ligands. These have been licensed for manufacture on large scale to eight companies and are available, in many cases, on very large scale (100's of Kg produced). This methodology has been widely utilized throughout academia and industry.
The history of our work up to the most recent developments will be discussed.
##### Chemistry
April 2, 2018
Kent 120 | Monday, 4:00 pm
## Jiehang Zhang, University of Maryland
#### Engineered Quantum Spin Systems: Out-of Equilibrium
Quantum mechanics prescribes exponential scaling of the Hilbert space dimension in many-body systems, which presents both challenges and new opportunities for understanding strongly correlated matter, especially since novel custom-built systems are now available. I will describe such efforts on engineering quantum systems atom by atom, precisely controlling them with laser-driven interactions, and increasing the system size up to a regime where the capabilities of classical computers are challenged.
I will focus on the platform of trapped atomic ions, where a combination of excellent coherence time and high-fidelity measurements has enabled many applications, ranging from simulating condensed matter physics, to quantum computation. We represent spin qubits with electronic levels of ions in a Coulomb crystal, and entangle them through tailored laser pulses. I will present recent experiments using these systems to study dynamical phase with individual resolution for more than 50 spins, as well as non-equilibrium driven matter. I then conclude with future prospects.
##### JFI Special Seminar
April 2, 2018
GCIS E223 | Monday, 3:00 pm
## Jennifer Cano, Princeton University
#### Topological Quantum Chemistry
The past decade's apparent success in predicting and experimentally discovering distinct classes of topological insulators (TIs) and semimetals masks a fundamental shortcoming: out of 200,000 stoichiometric compounds extant in material databases, only several hundred of them are topologically nontrivial. Are TIs that esoteric, or does this reflect a fundamental problem with the current piecemeal approach to finding them? To address this, we propose a new and complete electronic band theory that highlights the link between topology and local chemical bonding, and combines this with the conventional band theory of electrons. We classify the possible band structures for all 230 crystal symmetry groups that arise from local atomic orbitals, and show which are topologically nontrivial. We show how our topological band theory sheds new light on known TIs, and demonstrate the power of our method to predict new TIs.
April 2, 2018
PRC 201 | Monday, 1:30 pm
## Dr. Jordan Meier, National Cancer Insitute
#### Illuminating Acetylation's Dark Matter with Chemoproteomics
A paradox of modern acetylation biology is that the while number of sites of acetylation has climbed rapidly, the number of enzymes thought to catalyze this process has stayed relatively constant. Here we describe the utility of chemical proteomic methods to discover and characterize novel mechanisms of acetylation in endogenous cellular contexts. Our studies highlight an expanded landscape of regulatory acetylation in gene expression control, as well as new strategies to investigate the metabolic regulation and small molecule inhibition of acetyltransferases in cells.
Persons with a disability may call (773) 795-5843 in advance for assistance.
##### Chemistry
March 30, 2018
Kent 120 | Friday, 1:15 pm
## Fred Chong, The University of Chicago
#### Scaling up Quantum Computers
Quantum computing is at an inflection point, where 50-qubit (quantum bit) machines have been built, 100-qubit machines are just around the corner, and even 1000-qubit machines are perhaps only a few years away. These machines have the potential to fundamentally change our concept of what is computable and demonstrate practical applications in areas such as quantum chemistry, optimization, and quantum simulation.
Yet a significant resource gap remains between practical quantum algorithms and near-term machines. Programming, compilation and control will play a key role in increasing the efficiency of algorithms and machines to close this gap.
I will outline the grand research challenges in closing this gap, including programming language design, software and hardware verification, defining and perforating abstraction boundaries, cross-layer optimization, managing parallelism and communication, mapping and scheduling computations, reducing control complexity, machine-specific optimizations, and many more. I will also describe the resources and infrastructure available for tackling these challenges.
##### Physics Colloquium
March 29, 2018
KPTC 106 | Thursday, 4:00 pm
## Ken Kamrin, MIT
#### Modeling flowing granular material as a continuum: Surprising complexity meets surprising simplicity
Granular materials are common in everyday life but are historically difficult to model. This has direct real-world ramifications owing to the prominent role granular media play in multiple industries and in terrain dynamics. One can attempt to track every grain with discrete particle methods, but realistic systems are often too large for this approach and a continuum model is desired. However, granular media display unusual behaviors that complicate the continuum treatment: they can behave like solid, flow like liquid, or separate into a “gas”, and the rheology of the flowing state displays remarkable subtleties.
To address these challenges, in this talk we develop a family of continuum models and numerical solvers, which permit quantitative modeling capabilities for general problems and certain reduced-order approaches for problems of intrusion, impact, driving, and locomotion in grains. To calculate flows in general cases, a rather significant nonlocal effect is evident, which is well-described with our recent nonlocal model accounting for grain cooperativity within the rheology. On the other hand, to model just intrusion forces on submerged objects, we will show, and explain why, many of the experimentally observed results can be captured from a much simpler tension-free frictional plasticity model. This approach gives way to some surprisingly simple general tools, including the granular Resistive Force Theory, and a broad set of scaling laws inherent to the problem of granular locomotion. These scalings are validated experimentally and in discrete particle simulations suggesting a new down-scaled paradigm for granular locomotive design, on earth and beyond, to be used much like scaling laws in fluid mechanics. We close with ongoing efforts expanding into wet granular flows, multi-scale approaches, and self-optimizing wheels for off-road traction.
##### Computations in Science
March 28, 2018
KPTC 206 | Wednesday, 12:15 pm
## Seppe Kuehn, University of Illinois at Urbana-Champaign
#### Constraints on eco-evolutionary dynamics in bacterial communities
Can we predict evolutionary and ecological dynamics in microbial communities? I argue that understanding constraints on biological systems provides a path forward to build predictive models. I present two vignettes which illustrate the power of elucidating constraints. First, we ask how constraints on phenotypic variation can be exploited to predict evolution. We select Escherichia coli simultaneously for motility and growth and find that a trade-off between these phenotypes constrains adaptation. Using genetic engineering, high- throughput phenotyping and modeling we show that the genetic capacity of an organism to vary traits can qualitatively depend on its environment, which in turn alters its evolutionary trajectory [eLife, 2017]. Our results suggest that knowledge of phenotypic constraints and genetic architecture can provide a route to predicting evolutionary dynamics. Second, in nature microbial populations are subjected to nutrient fluctuations but we know little about how communities respond to these fluctuations. Using automated long-term single cell imaging and custom continuous-culture devices we subject bacterial populations to nutrient fluctuations on multiple timescales._x000B_We find populations recover faster from large, frequent fluctuations. Our observation is explained by a model that captures constraints on the rate at which populations transition from planktonic and aggregated lifestyles.
##### Molecular Engineering
March 27, 2018
ERC 161 | Tuesday, 11:00 am
## Epistasis: the link between protein sequence and function
#### A new approach shows promise
Epstasis is the observed statistical correlation of mutations affecting a given protein.
A new approach shows promise
Come at noon to eat and talk
Discussion launch time 12:15
##### MRSEC Baglunch
March 23, 2018
GCIS E123 | Friday, 12:00 pm
## Bill Archer, Los Alamos Laboratory
#### Computing in the Los Alamos Weapons Program
Los Alamos has continuously been on the forefront of scientific computing since it helped found the field. This talk will explore the rich history of computing in the Los Alamos weapons program. The current status of computing will be discussed, as will the expectations for the near future.
##### Physics Colloquium
March 21, 2018
KPTC 106 | Wednesday, 4:00 pm
## March Meeting rehash: moiré graphene superconductivity, etc.
I hope you can make it to the baglunch tomorrow. If you went to the March meeting, I hope you'll bring your favorite tidbit to tell us about. One dramatic announcement was the report of superconductivity in a bilayer of graphene. How does that work?? Come with your daffiest ideas.
12:00 would be a great time to show up with your food if you don't want to miss anything
12:15 ---you won't miss too much.
##### MRSEC Baglunch
March 16, 2018
GCIS E123 | Friday, 12:00 pm
## Aleksandra Vojvodic, University of Pennsylvania
#### Computationally predicting chemistry of transition-metal compound materials
Fueling the planet with energy, chemicals and food are central challenges of the 21st century. Most materials we see in our everyday life have seen at one point or another a catalyst material of a complex nature. I will demonstrate how we today can computationally predict new catalyst materials through a careful analysis of the surface chemistry at the atomic-scale level enabled by access to advanced computational approaches.
I will present our studies on electrochemical water splitting including both of its subreactions: the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Computationally we have identified a new highly active two-dimensional (2D) transition-metal carbide HER catalyst and transition-metal oxide OER catalysts that have been experimentally synthesized, characterized and tested. The OER catalysts belong to the perovskite group of oxide materials or are oxides based on earth abundant metal elements. I will also share our recent insights on the reactivity and activity of metal-supported thin layers, nanoparticles of oxides and heterostructured oxide systems. Finally, I will discuss our recent findings on oxygen incorporation chemistry into non-stoichiometric oxides.
##### Molecular Engineering
March 15, 2018
ERC 201 | Thursday, 11:00 am
## Gediminas Juzeliūnas, Vilnius University, Lithuania
#### Synthetic spin-orbit coupling for ultracold atoms
Currently there is a great deal of activities in studying the spin-orbit coupling (SOC) for ultracold atoms. One of the challenges is to experimentally produce a two-dimensional (2D) SOC of the Rashba type, as well as a 3D Weyl SOC for the center of mass motion of ultracold atoms [1]. In particular, it was proposed that the 2D and 3D SOC can be generated by laser-dressing atomic internal states [1] or using a periodic sequence of magnetic gradient pulses [2]. Here we shall review these activities and also talk about the omnidirectional Spin-Hall effect [3] which can manifest for Weyl spin-orbit coupled ultracold atoms. We shall also discuss another way of creating the 2D SOC using ultracold atoms confined in bilayer structures [4-5]. An interplay between the inter-layer tunneling, intra-layer Raman coupling and intra-layer atom-atom interaction gives rise to an effective 2D SOC providing diverse ground-state configurations for bilayer Bose-Einstein condensates (BEC) [4] and degenerate Fermi gases [5].
##### JFI Special Seminar
March 14, 2018
KPTC 206 | Wednesday, 4:00 pm
## Roy Beck-Barkai , Tel-Aviv University
#### From kB to kB: Universal and efficient entropy estimation using a compression algorithm
Entropy and free-energy estimation are key in thermodynamic characterization of simulated systems ranging from spin models through polymers, colloids, protein structure, and drug-design. Current techniques suffer from being model specific, requiring abundant computation resources and simulation at conditions far from the studied realization. In this talk, I will present a novel universal scheme to calculate entropy using lossless compression algorithms and validate it on simulated systems of increasing complexity. Our results show accurate entropy values compared to benchmark calculations while being computationally effective. In molecular-dynamics simulations of protein folding, we exhibit unmatched detection capability of the folded states by measuring previously undetectable entropy fluctuations along the simulation timeline. Such entropy evaluation opens a new window onto the dynamics of complex systems and allows efficient free-energy calculations.
##### Computations in Science
March 14, 2018
KPTC 206 | Wednesday, 12:15 pm
## The Tuesday JFI Seminar - Lutz Maibum, Department of Chemistry, University of Washington
#### Spatial Organization of Complex Lipid Bilayers: Emergent Order Across Multiple Scales
Cellular membranes are bilayers made of a large number of different types of phospholipids, sterols, and proteins. Their spatial organization is of fundamental importance for a large number of elementary biological processes including cell signaling and membrane trafficking. It has become clear that phospholipids and sterols contribute significantly to the lateral structure of such membranes. The order that emerges from their interactions spans multiple length scales, which necessitates the use of a wide range of models to study membrane organization with computational methods. In this talk I present our principal discoveries of membrane structure across multiple scales, including new aspects of the condensing effect of cholesterol, the rich phase behavior of multicomponent bilayers, and the effect of membrane fluctuations on protein interactions.
##### The Tuesday JFI Seminar
March 13, 2018
GCIS W301 | Tuesday, 4:00 pm
## Charles M. Lieber, Harvard University
#### Nanoelectronic Tools for Brain Science
##### Chemistry
March 12, 2018
Kent 120 | Monday, 4:00 pm
## Peter Schauss, Princeton University
#### Quantum gas microscopy of many-body dynamics in Fermi-Hubbard and Ising systems
The ability to probe and manipulate cold atoms in optical lattices at the atomic level using quantum gas microscopes enables quantitative studies of quantum many-body dynamics. While there are many well-developed theoretical tools to study many-body quantum systems in equilibrium, gaining insight into dynamics is challenging with available techniques. Approximate methods need to be benchmarked, creating an urgent need for measurements in experimental model systems. In this talk, I will discuss two such measurements.
First, I will present a study that probes the relaxation of density modulations in the doped Fermi-Hubbard model. This leads to a hydrodynamic description that allows us to determine the conductivity. We observe bad metallic behavior that we compare to predictions from finite-temperature Lanczos calculations and dynamical mean field theory.
Second, I introduce a new platform to study the 2D quantum Ising model. Via optical coupling of atoms in an optical lattice to a low-lying Rydberg state, we observe quench dynamics in the resulting Ising model and prepare states with antiferromagnetic correlations.
##### JFI Special Seminar
March 12, 2018
KPTC 206 | Monday, 2:00 pm
## Chang-Tse Hsieh, IPMU
#### Symmetry-protected critical phases, generalized Lieb-Schultz-Mattis theorem, and global anomalies in (1+1) dimensions
The robustness of gaplessness in the presence of symmetries is one of the characteristics of the edge states of one-dimensional symmetry-protected topological (SPT) phases. These edge states, as the symmetries are realized in an on-site manner, can not exist alone and must arise on the boundary of one-higher dimensional SPT phases. This situation can, however, be circumvented for a 1d system with non-on-site symmetries, such as lattice translation symmetry, in the case that a nontrivial 2d bulk is absent. In this talk, I will discuss the quantum criticality in purely 1d lattice systems that is protected by translation symmetry together with some other on-site symmetries, from the perspective of ('t Hooft) anomaly matching. Examples include the charged fermions and SU(N) spin chains. The Lieb-Schultz-Mattis theorem, in the framework of field theory, is also re-derived and generalized.
March 12, 2018
PRC 201 | Monday, 1:30 pm
## Liantao Wang
#### Future of Particle Physics: LHC and beyond
Particle physics entered a new era after the discovery of the Higgs boson. The Standard Model has left open many important questions, such as the origin of electroweak scale and identity of the dark matter. Searching for answers to these questions will be the main goal for particle physics in the decades to come. I will review the status of theoretical ideas and experimental searches for new physics, with focus on recent developments. I will also offer my perspective on possible future directions, including the next steps in the searches at the LHC, as well as other on-going and future experiments.
##### Physics Colloquium
March 8, 2018
KPTC 106 | Thursday, 4:00 pm
## Sean M. Gibbons, PhD, MIT
#### Individual-specific eco-evolutionary dynamics in the human gut microbiome
Dr. Gibbons will be hosted by BPHYS first-years, Vil Zsolnay and Elizabeth White.
##### Biophysical Dynamics
March 6, 2018
GCIS W301 | Tuesday, 12:00 pm
## JR Schmidt, University of Wisconsin-Madison
#### Physics-based force fields for next-generation accuracy and transability in molecular simulations
I will present a general methodology for generating accurate and transferable "physics-based" ab initio force fields for use in “next generation” molecular dynamics simulations. These force field models incorporate explicit terms to account for the dominant forces in (non-reactive) intermolecular interactions: exchange repulsion, electrostatics, polarization, and dispersion. This approach opens exciting possibilities for modeling chemical systems for which little or no experimental data exists. I will present a variety of applications, including those involving metal-organic framework materials, organic liquids, ionic liquids. The transferable nature of the force field models allows for their utilization for a wide variety of chemical systems. Building on that work, I will also present a number of recent developments that enable a significant increase in the accuracy of ab initio force fields via new approaches for modeling short-range Pauli repulsion and for capturing the local anisotropy of inter-atomic interactions (e.g. in the vicinity of a "lone pair"). These latter advances open up the possibility for even higher accuracy and transferability in a wide variety molecular simulation contexts.
##### Chemistry
March 5, 2018
Kent 120 | Monday, 4:00 pm
## Anatoly Dymarsky, University of Kentucky
#### Defining thermalization time
The conventional picture of how an isolated chaotic system thermalizes suggests that starting from a out of equilibrium state, the system reaches the equilibrium within Thouless time - the time necessary for the slowest (diffusive) mode to propagate across the whole system. Once that happened the system is expected to be fully ergodic i.e. its behavior should be independent of the initial conditions. It is in this regime a quantum system is expected to be described by a random matrix theory. Accordingly Thouless energy is usually associated with the energy scale of applicability of the random matrix description. In this talk we show that the conventional picture is too naive. By introducing a new characteristic of quantum systems which is sensitive to thermalization time, we show that the energy scale at which Eigenstate Thermalization Hypothesis ansatz reduces to the random matrix theory is parametrically different from the Thouless scale.
March 5, 2018
PRC 201 | Monday, 1:30 pm
## Vincenzo Vitelli
#### From LEGO to Active Fluids
This colloquium offers a gentle introduction to the physics of topological materials using vivid mechanical demonstrations. The distinctive property of topological materials is the existence of states and excitations that are robust (or protected) against structural deformations, changes in material parameters or imperfections. We concentrate on two examples of topologically protected states: the folding motions of origami-like structures and sound propagation in active fluids composed of self-propelled particles. In both cases we trace the mathematical origin of physical robustness to elegant notions of topology.
##### Physics Colloquium
March 1, 2018
KPTC 106 | Thursday, 4:00 pm
## Dr. Tanay Roy, Tata Institute of Fundamental Research
#### Multi-mode Superconducting Circuits for Building Programmable Multi-qubit Quantum Processors
Quantum processors are capable of providing enormous speedup to certain problems by exploiting classically inaccessible paths. A vast majority of the small-scale quantum processors demonstrated so far in solid-state systems rely on the nearest-neighbor coupling. The limited connectivity and native gates restricted between two qubits hinder efficient implementation of many quantum algorithms. In this talk, I will introduce the “trimon” [1], a longitudinally coupled three-qubit system based on a multi-mode superconducting circuit. I will first describe how we can achieve universal programmability by utilizing elementary controlled-controlled-rotations and all-to-all connectivity. Reconstruction of the density matrix for an arbitrary three-qubit state is accomplished using a joint readout scheme. I will then discuss the performance of the single-pulse generalized Toffoli gates and the preparation of different two- and three-qubit entangled states. Another unique feature of this system is the ability to implement error-free CCZ gate [2] which simplifies the construction of various quantum oracles. I will demonstrate these capabilities by executing various quantum algorithms like Deutsch-Jozsa, Bernstein-Vazirani, Grover, quantum Fourier transform etc. on the three-qubit processor. Finally, I will discuss the possibility of building larger quantum processors using these longitudinally coupled multi-qubit systems.
##### JFI Special Seminar
March 1, 2018
ERC 201 | Thursday, 1:30 pm
## IME Distinguished Colloquium Series: Jeff Snyder, Northwestern University
#### Dislocation strain as the mechanism of phonon scattering at grain boundaries
For 50 years, we have commonly been using Casimir’s theory that describes the scattering of heat-carrying lattice vibrations (phonons) on the sample boundaries to also describe the reduction of thermal conductivity due to grain boundaries. In the frequency-independent Casimir model, phonons simply cannot travel across the boundaries, which is not the case in grain boundaries. This and a growing body of experimental and computational evidence shows that the modification of the Casimir model is necessary for grain boundaries. In this talk I will discuss our analysis of phonon scattering that controls the thermal conductivity of many common thermoelectric materials. We find that the grain boundary dislocation strain model can substitute for the Casimir model. More importantly, the two models can be distinguished at low temperature in fine-grained materials such that experimental evidence supports the grain boundary dislocation strain model. In this way, we suggest that grain boundaries themselves are best conceptualized as a collection of dislocations. Since strain and grain boundary structures can vary, we should be able to engineer grain boundaries or grain complexions (including extrinsic atoms) to disrupt phonon transport without harming electron transport.
##### Molecular Engineering
March 1, 2018
ERC 161 | Thursday, 11:00 am
## Michelle Driscoll, Northwestern University
#### Mind the gap: a cascade of instabilities created by rotating beads near a floor
Does a rotating bead always spin in place? Not if that bead is near a surface: rolling leads to translational motion, as well as very strong flows around the bead, even quite far away. These flows strongly couple the motion of nearby microrollers (rotating beads), which leads to a rich variety of collective effects. Using experiments in tandem with large-scale 3D simulations, we have shown that driving a compact group of microrollers leads to a new kind of flow instability, whose wavelength is controlled not by the driving torque or the fluid viscosity, but a geometric parameter: the microroller's distance above the container floor. Furthermore, under the right conditions, stable, compact clusters we term "critters" can emerge from the unstable interface. Our simulations and experiments suggest that these critters are a stable state of the system, move much faster than individual rollers, and quickly respond to a changing drive. We believe that critters are unique in that they are clusters which form only with hydrodynamic interactions; no interparticle potentials are needed to create these structures. Furthermore, as compact, self-assembled structures which can easily be remotely guided, critters may offer a promising tool for microscopic transport.
##### Computations in Science
February 28, 2018
KPTC 206 | Wednesday, 12:15 pm
## Video Rate Atomic Force Microscopy Workshop
#### MRSEC and Asylum Research (Oxford Instruments)
This informative free workshop will include lectures and hands-on demonstrations for researchers who want to better understand how AFM can capture dynamic processes at the nanoscale. Topics will specifically cover video-rate AFM and the latest innovations for electrochemistry and nanomechanics / mechanobiology applications. The workshop is ideal for those that have AFM experience, as well as those who would like to learn more about incorporating AFM into their research. Registration is free, however, due to limited seating, all attendees must register.
##### MRSEC Workshop
February 28, 2018
ERC 201B | Wednesday, 9:00 am
## Bozhi Tian - Department of Chemistry - The University of Chicago
#### Physical Biology and Material Dynamics at Hard/Soft Interfaces
Although there are numerous studies on either hard or soft materials, our understanding of the fundamentals at hard/soft interfaces has been limited. As different types of energy (such as electrostatic, mechanical, thermal, and chemical energies) display diverse scaling behaviors and can converge, an appropriate selection of the length scale is critical for promoting new scientific discoveries across these interfaces. My group integrates material science with biophysics to study several hard/soft interfaces. We synthesize new materials and probe interfacial dynamics, with particular focus at the sub-micrometer and sub-cellular length scales. Our unique and extensive contributions have: (1) enabled non-genetic, freestanding, and semiconductor-based biological modulation; (2) revealed new dynamic aspects of liquid alloy droplets in semiconductor synthesis; and (3) exploited the dynamic behaviors of minerals or granular materials in polymeric matrices.
##### The Tuesday JFI Seminar
February 27, 2018
Kent 120 | Tuesday, 4:00 pm
## Toshikaze Kariyado, National Institute for Materials Science, Tsukuba
#### Designing Topological States in Graphene with Nano Holes
Gapping out Dirac cones in honeycomb lattice model has been playing key roles in finding new topological phases of matter, like Haldane’s seminal work on quantum anomalous Hall effect (QAHE) or Kane-Mele’s work on quantum spin Hall effect (QSHE). Note, however, that QAHE and QSHE require magnetism (time-reversal symmetry breaking) or spin-orbit coupling (SOC), respectively. A possible and magnetism/SOC free method to have finite gap in graphene is to introduce regularly aligned holes into a graphene sheet [1]. (Or, to make graphene antidot lattice, aka graphene nanomesh.) Here, we analyze the electronic structures of graphene nanomeshes in terms of topology [2]. Interestingly, it is found that a nanomesh where holes form triangular lattice and a nanomesh where holes form honeycomb lattice are topologically distinct with each other. The topological nontriviality is confirmed by explicitly calculating interface tates between the two regions of triangular and honeycomb nanomeshes, whose band structure has counterpropagating nature resembling to the one for helical edge states in QSH states. In addition to the interface state, we also diagnose the topology of the system by symmetry of the wave function, i.e., by a topological crystalline insulator viewpoint. It is demonstrated that the parity
index against 2D spatial inversion is a key quantity to detect topology in our system.
February 27, 2018
GCIS E123 | Tuesday, 2:00 pm
## Chad M. Rienstra, University of Illinois Urbana-Champaign
#### Molecular Fibrils and Sponges: Insights into Parkinson's Disease and Antifungal Drugs from NMR Spectroscopy
My research addresses fundamental questions about molecular structure and function of non-crystalline solids utilizing magic-angle spinning solid-state NMR spectroscopy along with a range of other chemical and biophysical methods. In this seminar, I will describe our recent results reporting the first high-resolution structure of full length alpha-synuclein fibrils, the protein most abundant in Lewy bodies and implicated in Parkinson’s disease propagation, and the mode of action of the antifungal drug amphotericin B, which binds and extracts sterols from lipid bilayers.
##### Chemistry
February 26, 2018
Kent 120 | Monday, 4:00 pm
## Vedika Khemani, Harvard University
February 26, 2018
PRC 201 | Monday, 1:30 pm
## Sihong Wang, Postdoctoral Fellow, Department of Chemical Engineering, Stanford University
#### Merging Electronics with Living Systems: From Intrinsically Stretchable Materials and Devices to Mechanical Energy Harvesting
The vast amount of biological mysteries and biomedical challenges faced by human provide a prominent drive for seamlessly merging electronics with biological living systems (e.g. human bodies) to achieve long-term stable functions. Towards this trend, the main bottlenecks are the huge mechanical mismatch between the current form of rigid electronics and the soft biological tissues, as well as the limited lifetimes of the battery-based power supplies.
In this talk, I will first describe a new form of electronics with skin-like softness and stretchability, which is built upon a new class of intrinsically stretchable polymer materials and a new set of fabrication technology. As the core material basis, intrinsically stretchable polymer semiconductors have been developed through the physical engineering of polymer chain dynamics and crystallization based on the nanoconfinement effect. This fundamentally-new and universally-applicable methodology enables conjugated polymers to possess both high electrical-performance and extraordinary stretchability. Then, proceeding towards building electronics with this new class of polymer materials, the first polymer-friendly manufacturing process has been designed for large-scale intrinsically stretchable transistor arrays—the core device building-blocks for electronics. As a whole, these renovations in the material basis and technology foundation have led to the realization of circuit-level functionalities for the processing of biological signals, with unprecedented mechanical deformability and skin conformability. In the second part of the talk, I will introduce the invention and development of triboelectric nanogenerators as a new technology for mechanical energy harvesting, which provides a solution for sustainably powering electronics. The discussion will span from the establishment of basic operation mechanisms, the design strategies of material and device structure towards high energy conversion efficiency, to the hybridization with Li-ion batteries for effective energy storage. Equipping electronics with human-like form-factors and biomechanically-driven power supplies has opened a new paradigm for wearable and implantable bio-electronic tools for biological studies, personal healthcare, medical diagnosis and therapeutics.
##### Molecular Engineering
February 26, 2018
ERC 161 | Monday, 12:00 pm
## Pedro Lopes, Sherbrooke
#### Signatures of the chiral anomaly in phonon dynamics
The past decade of condensed matter physics has put a great weight in the importance of topological phenomena. Our particular interest here are Weyl semi-metals. Differently from its gapped insulating and superconducting topological cousins, the low-energy physics of Weyl semi-metals is not restricted to its surface, with bulk electronic properties being governed by linearly dispersing bands. An effective 3+1D Lorentz symmetry thus develops in these materials, settling Weyl semi-metals as prime candidates for comparative and analogue high-energy physics studies. In this context, we consider the phenomenon of the chiral anomaly, which in the high-energy context controls the decay rates of neutral pions into photons. In condensed matter, this phenomenon is traditionally understood to give rise to novel electronic transport phenomenology, whose verification, however, has been seen with controversy in the literature. To avoid such controversies, we present in this talk a detour from transport phenomena and show that optical properties of lattice oscillations carry singular signatures of the chiral anomaly. These come about by means of a novel type of polariton effect and are restricted only to certain classes of lattice oscillations in mirror symmetry broken Weyl semi-metals. Our proposed signatures of the condensed matter chiral anomaly then provide a robust alternative to transport while simultaneously constraining the systems to be studied, helping guide experimental efforts."
February 23, 2018
PRC 201 | Friday, 1:30 pm
## Peng Liu, University of Pittsburgh
#### Computational Studies of Functionalization of C-H, C-C Bonds and Olefins
##### Chemistry
February 23, 2018
Kent 120 | Friday, 1:15 pm
## Hui Cao, Yale University
#### Mesoscopic Optics
Random scattering of light, e.g., in paint, cloud and biological tissue, is a common process of both fundamental interest and practical relevance. The interference of multiply scattered waves leads to remarkable phenomena in mesoscopic physics such as Anderson localization and universal conductance fluctuations. In applications, optical scattering is the main obstacle to imaging or sending information through turbid media. Recent developments of adaptive wavefront shaping in optics enabled imaging and focusing of light through opaque samples. By selective coupling to high or low transmission eigenchannels, we varied the transmission of a laser beam through a highly scattering system by two orders of magnitude, and drastically changed the energy density distribution inside the system. Furthermore, we utilized the multiple scattering of light in a random structure to realize a chip-scale spectrometer. The speckle pattern is used as a fingerprint to recover an arbitrary spectrum. Such a spectrometer has good spectral resolution and wide frequency range of operation.
##### Physics Colloquium
February 22, 2018
KPTC 106 | Thursday, 4:00 pm
## Xiaoyuan (Shawn) Chen, National Institute of Biomedical Imaging and Bioengineering
#### Cancer Nanotheranostics
Theranostics (Rx/Dx) aims to develop molecular diagnostic tests and targeted therapeutics with the goals of individualizing treatment by targeting therapy to an individual's specific disease subtype and genetic profile. It can be diagnosis followed by therapy to stratify patients who will likely respond to a given treatment; it can also be therapy followed by diagnosis to monitor early response to treatment and predict treatment efficacy; it is also possible that diagnostics and therapeutics are co-developed (nanotheranostics). This talk will give examples of how to assemble both inorganic and organic/polymeric materials for multimodality cancer imaging and drug/gene delivery.
##### Chemistry
February 21, 2018
Kent 120 | Wednesday, 3:00 pm
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# Determining excitated state of an electron of an $\rm H$ atom
Suppose we have an electron of $\rm{H}$ atom( suppose it is at 4th shell). But it can't remain in the excited state for a long time. So it can jump to 1st ,2nd or the 3rd orbital. What is the factor that decides whether the electron will jump to any one of the lower energy state orbitals. Or is that random?
The most usual one is the electric dipole approximation, which is clearly dominant. The probability is proportional to $\langle \phi_{final} | \vec{r} | \phi_{initial} \rangle$
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Table 4.
Analysis of Maximum Likelihood Estimates for the Full Logistic Regression Model Related to Odds of Readmission
• a P<.05.
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×
# INO 2015
Here are the question papers with solutions of INOs (Indian National Olympiads) held on 31 Jan, 2015 and 1 Feb, 2015.
Note
1. You might have to append extension .pdf on downloading.
2. It would be nice if someone can provide me a link for INMO.
3. Abbreviations:
• INChO:Indian National Chemistry Olympiad
• INAO: Indian National Astronomy Olympiad
• INBO: Indian National Biology Olympiad
• INPhO:Indian National Physics Olympiad
• INJSO: Indian National Junior Science Olympiad
Note by Pranjal Jain
3 years ago
MarkdownAppears as
*italics* or _italics_ italics
**bold** or __bold__ bold
- bulleted- list
• bulleted
• list
1. numbered2. list
1. numbered
2. list
Note: you must add a full line of space before and after lists for them to show up correctly
paragraph 1paragraph 2
paragraph 1
paragraph 2
[example link](https://brilliant.org)example link
> This is a quote
This is a quote
# I indented these lines
# 4 spaces, and now they show
# up as a code block.
print "hello world"
# I indented these lines
# 4 spaces, and now they show
# up as a code block.
print "hello world"
MathAppears as
Remember to wrap math in $$...$$ or $...$ to ensure proper formatting.
2 \times 3 $$2 \times 3$$
2^{34} $$2^{34}$$
a_{i-1} $$a_{i-1}$$
\frac{2}{3} $$\frac{2}{3}$$
\sqrt{2} $$\sqrt{2}$$
\sum_{i=1}^3 $$\sum_{i=1}^3$$
\sin \theta $$\sin \theta$$
\boxed{123} $$\boxed{123}$$
## Comments
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- 2 years, 11 months ago
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Astronomy:
Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. 1 150111000025 8 150610000449 15 150711000690 22 151010001014 29 151210001307 36 151611001550 2 150111100019 9 150611000414 16 150711000691 23 151011001009 30 151210001312
3 150210000105 10 150611000419 17 150711100674 24 151110101115 31 151210001315
4 150210100098 11 150710000712 18 150711100678 25 151111101104 32 151210001319
5 150211100094 12 150710100707 19 150711100679 26 151111101106 33 151510101513
6 150511100304 13 150711000685 20 150711100680 27 151111101107 34 151511001511
7 150610000429 14 150711000687 21 150711100683 28 151210001305 35 151511101506
Cut off score: 58/100
Biology:
Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. 1 150100010067 8 150400010277 15 150600010522 22 151000011086 29 151200011391 2 150100010077 9 150400110229 16 150600010528 23 151001111026 30 151200011405 3 150200010162 10 150401110224 17 150600010529 24 151100011228 31 151200011409 4 150200010172 11 150500010360 18 150600010532 25 151100011236 32 151200111343 5 150201110112 12 150500010368 19 150800010904 26 151100011264 33 151200111348 6 150201110113 13 150500010376 20 150800110854 27 151200011386 34 151300111446 7 150301110192 14 150600010518 21 151000011075 28 151200011388 35 151400011497 Cut off score: 167/300
Chemistry:
Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Roll No. Roll No. 1 150111100018 8 150701100717 15 150711100669 22 150801100849 29 151001111026 36 151511101505 2 150201100114 9 150701100721 16 150711100671 23 150810100841 30 151100101188 37 151511101506 3 150210100098 10 150701100732 17 150711100674 24 150810100843 31 151110101115
4 150211100095 11 150710100696 18 150711100678 25 150811100838 32 151111101107
5 150410100219 12 150710100703 19 150711100679 26 150901100938 33 151200101373
6 150410100220 13 150711100665 20 150711100683 27 151000101047 34 151201101327
7 150511100303 14 150711100666 21 150800100881 28 151001101037 35 151400101481
Cut off score: 65.5/112.5
Junior Science:
Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. 1 150220000091 8 150720000560 15 150720000627 22 151020000990 29 151120001096 2 150320000179 9 150720000561 16 150820000829 23 151020000991 30 151120001097 3 150420000210 10 150720000572 17 150820000831 24 151020000994 31 151120001098 4 150520000294 11 150720000598 18 150820000835 25 151020000996 32 151120001102 5 150620000378 12 150720000605 19 150820000836 26 151020000999 33 151220001268 6 150620000396 13 150720000606 20 150920000917 27 151120001090 34 151220001272 7 150720000556 14 150720000615 21 150920000919 28 151120001095 35 151220001286Cut off score: 39/90
Physics: Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. Sr. No. Roll No. 1 150111100019 8 150501100329 15 150701100732 22 150711100681 29 151201001336 2 150211100094 9 150511000306 16 150711000687 23 150711100683 30 151201101325 3 150211100095 10 150601000469 17 150711000693 24 150801100849 31 151211101294 4 150401100226 11 150601100458 18 150711100674 25 151001001040 32 151401001476 5 150401110224 12 150611000413 19 150711100678 26 151001101033 33 151401101473 6 150411100216 13 150701100717 20 150711100679 27 151001111026 34 151401101474 7 150501000339 14 150701100728 21 150711100680 28 151111101106 35 151511001511 Cut off score: 55.5/100
- 2 years, 11 months ago
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Congrats to all those selected for OCSCs!
- 2 years, 11 months ago
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Thanks.
- 2 years, 11 months ago
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For which one you got selected?
- 2 years, 11 months ago
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INCHO
- 2 years, 11 months ago
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How much had you got?
- 2 years, 11 months ago
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67
- 2 years, 11 months ago
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Congrats Ronak!! Good Luck for OCSC! Will you be attending? JEE?
- 2 years, 11 months ago
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Camp is just after JEE
- 2 years, 11 months ago
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Oh I see! Good luck then.
- 2 years, 11 months ago
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Camp is after JEE I think.
- 2 years, 11 months ago
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How do you know the roll number of Mvs Saketh
- 2 years, 11 months ago
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I know how much marks he got, that was well above cut-off.
- 2 years, 11 months ago
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Congrats @Mvs Saketh
- 2 years, 11 months ago
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Did you get selected ?
- 2 years, 11 months ago
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HBCSE site is loading
- 2 years, 11 months ago
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It has crashed again , but it was half loaded, and they have uploaded the results.
- 2 years, 11 months ago
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Slow internet :(
- 2 years, 11 months ago
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I'm getting 58 in INPhO, 73.5 in INChO.
Marks my friends have got in INPhO : 36, 42, 43.5.
Marks my friends have got in INChO : 33, 40.5, 41, 54.
- 3 years ago
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OMG! @Agnish Kumar Behera That's too damn awesome. You qualified 2 IOTC's Did you make it to INBO-OCSC this year also ? What was your score in INBO? How are you so good at all 3 sciences? Is your target JEE/PMT/pure science?
- 2 years, 10 months ago
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I'll be joining IISc this year.. :)
I got 188 in INBO but sadly I wont be attending the Bio OCSC this year..
- 2 years, 10 months ago
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Congrats. Really nice. Make it to IPHO!
- 2 years, 10 months ago
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So you want to become a researcher in basic sciences.
- 2 years, 10 months ago
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Yep.. :)
Whats your aim Ronak ?
- 2 years, 10 months ago
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bro you got a passport? (they say its needed ) but this time IPHO/ICHO in mumbai only, so we shouldnt need one right?
- 2 years, 10 months ago
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Thanks and best of luck , i shall update the stats now,, :)
- 3 years ago
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A friend of mine got 18 in INPhO. Please update your stats. :)
- 3 years ago
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no offense to your friend but that wont significantly contribute to the data in any manner, but yes i will still update it :)
- 3 years ago
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May increase my chances of selection if rest 250 people get 18 :p
- 3 years ago
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it will increase everyones chances :P but then we would have a great deal to worry about the next generation which is ours
- 3 years ago
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Lol, true =P
- 3 years ago
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Arpan Banerjee has pointed out the true reason, 'HOPE', for which I have provided the marks of my friend.. :P
- 3 years ago
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@Shriram S B @Uchiha Itachi and other INPHO participants, help me make a statistical prediction by going to http://inpho-blogspot-2015.blogspot.in/
- 3 years ago
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@Mvs Saketh Many more marks have been posted at the blog. Please update stats.
- 3 years ago
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@Mvs Saketh well, i study at allen,Kota. 8 students qualified for inpho (including me).i have already posted marks of 3 of them. another one:51 . i do not exactly know the marks of rest of the students but the guy who got 51 told me that all others got in the range of 41 to 50 .
- 3 years ago
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@Mvs Saketh Two highest from reso are 43 and 65. I don't know about other coachings
- 3 years ago
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Thankyou :)
- 3 years ago
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is Bhavya getting that 65
- 3 years ago
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Yes, I wonder how will he get JEE-1 with such performance
- 3 years ago
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But why would he get AIR 1 in JEE ??Is he that good.?? There are many others in Kota .
- 3 years ago
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None like him. I don't like praising him but he got AIR-1 in KVPY in 11th. He has won Gold medal for India in Astronomy Olympiad held in Lithuania last year. He also bronze medal in IJSO held in Iran in class 10th.
- 3 years ago
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He seems to be on the right track for AIR 1. but you have to keep in mind that Chitraang Murdia did not have any medals in any olympiads before appearing for JEE but still got AIR 1 by a huge margin .After all everyone starts the Exam from 0 marks no matter how many certificates or medals he may have.
- 3 years ago
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He didn't had medals by that time because IO's were scheduled later. =P
- 2 years, 11 months ago
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what about incho
- 3 years ago
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Mine are much less 43. Though 5-6 are getting 60+.
- 3 years ago
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I am also in reso.. Do you mean reso kota or overall?
- 3 years ago
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Reso kota
- 3 years ago
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but i got selected for InChO AND GOT 35 MARKS in InChO . Is there any chance of me getting selected tocamp???
- 2 years ago
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hi avinesh :D
- 2 years ago
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i am studying in class 11
- 2 years ago
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how much did all your friends get in INChO
- 1 year, 12 months ago
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Did any receive scorecard for inpho pls post your marks
- 2 years ago
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not yet
- 2 years ago
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Check the 2016 thread.
- 2 years ago
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I feel the cutoff would be 40 as other than Yukawa qs last two parts and 3 eqn 3 variables of resistances question everything was jee level. How much are all of you expecting.
- 2 years ago
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use this thread
https://brilliant.org/discussions/thread/ino-2016/
- 2 years ago
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which part 3 eqns 3 variables
- 2 years ago
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The resistances found in the graphing part are not the actual Rab,Rbc,Rca. For example from the graph we got 5.66 which is not rca but rca-effective which is formed by ab,bc in series which are in turn parallel with ca.
- 2 years ago
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In last question in 2nd part in finding energy do we had to do -du/dr and then do it equal to centripetal force for getting mv^2 and then simply add the potential energy to write total energy
- 2 years ago
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@A A I substituted v from mvr=nh/2pi. Is that correct?
- 2 years ago
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might be higher
- 2 years ago
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what was the level of inpho 2016 acc to all of you
- 2 years ago
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Solutions out How much do you expet
- 2 years ago
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39
- 2 years ago
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@A A very well
me 29
- 2 years ago
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@A A I feel some answers in the last question are wrong. They have used u(symbol mu) wrongly in many places where m should be present.
- 2 years ago
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How much d u think will be the cutoff?
- 2 years ago
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I think it will definitely be above 35
- 2 years ago
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exactly
- 2 years ago
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easier than previous ones, i'll say
- 2 years ago
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How was INAO 2016 for everyone?
- 2 years ago
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how was inao 2016 for 11th
- 2 years ago
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It went okay, I guess. Want to compare answers?
- 2 years ago
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Well , I gave INAO jr but paper was same. I expect 49-54. Any chance for OSCS ?
- 2 years ago
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Wait till the performance card comes. Last year's cutoff was only 37.5 so if you get what you expect, you'll almost surely be in.
- 2 years ago
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So would any one of you be glad to give any tips about inpho2016 and incho2016 @Ronak Agarwal @Pranjal Jain @Mvs Saketh
- 2 years, 1 month ago
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Bhaiya if you dont mind can i ask your score in NSEP And NSEC
- 2 years, 1 month ago
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Well actually both of them went way bad... Physics 138 Chem 134
- 2 years, 1 month ago
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I Got 70 in physics and 98 in chemistry :(
- 2 years, 1 month ago
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That a very good score in 11th, I don't remember my 11th marks
Are you eligible for the centre top 10% certificate?
- 2 years, 1 month ago
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How can i know whether i am eligible ? is there a procedure?
- 2 years, 1 month ago
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ask Abhishek sir, he gave me the certificate last year
- 2 years, 1 month ago
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Is there a thread on discussion for 2015?
- 2 years, 2 months ago
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where can i find students selected for apho 2015
- 2 years, 11 months ago
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Could you give its full form ?
- 2 years, 11 months ago
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asian physics olympiad
- 2 years, 11 months ago
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Congratulations to all those who have been selected for the OCSC 2015. Personally, I never believed for an instant that the cutoff could be below 60 :P
- 2 years, 11 months ago
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congrats to all who got selected.
- 2 years, 11 months ago
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INMO results are declared.
- 2 years, 11 months ago
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Cutoffs INAO 58 INPHO 55.5 INCHO 65.5
- 2 years, 11 months ago
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cutoff 55.5 for inpho
- 2 years, 11 months ago
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Damn, what about others?
- 2 years, 11 months ago
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ya it will be very hard for those very near and below the cutoff to digest but take it lightly coz there are many other bigger things than this to succeed
- 2 years, 11 months ago
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That's ok.. Just missed in both though.. Anyway, congrats! You got into Physics OCSC!
- 2 years, 11 months ago
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At what time will the results be out?
- 2 years, 11 months ago
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Now the HBCSE page is also not opening!!
- 2 years, 11 months ago
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i know, same here, they are updating the results , i am pretty sure
- 2 years, 11 months ago
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What is taking them so much time?!?
- 2 years, 11 months ago
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I even think so. Just put the results on site.
- 2 years, 11 months ago
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Post cutoff here if anyone is able to open.
- 2 years, 11 months ago
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same here, anxiety at its peak, and wonder whats taking them so long
- 2 years, 11 months ago
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same here, just can't control myself.
- 2 years, 11 months ago
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Just tell if you guys have decided to call off waiting for the result and back to JEE
- 2 years, 11 months ago
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how much are you getting in inpho
- 2 years, 11 months ago
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Your marks?
- 2 years, 11 months ago
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Very low marks .I have a 44. My all INO marks are in that range,INAO 46,INCho 52 .I have no hope but just want to know who get selected as it is then whom I will see at JEE-15
- 2 years, 11 months ago
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did you get selected in apho
- 2 years, 11 months ago
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Did they put Apho list?
- 2 years, 11 months ago
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i dont know
- 2 years, 11 months ago
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Congrats @Mvs Saketh !! Good luck for OCSC! Will you be attending camp? Just before JEE?
- 2 years, 11 months ago
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i am sure that u r definitely in inpho camps
- 2 years, 11 months ago
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hopefully
- 2 years, 11 months ago
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Sure they will publish the result today? Saketh,do you when will KVPY guys publish the result?
- 2 years, 11 months ago
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They will publish it near the board results time, (i heard) , so i am not so eager for it yet, Tentative means today is what they predecided but it might change if needed, though it rarely changes
- 2 years, 11 months ago
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KVPY results after board exam result.Last year,it was around this time.If it was during that time,I have been wasting a few minutes each day taking the kvpy website
- 2 years, 11 months ago
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What is the board results time.
- 2 years, 11 months ago
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few days after JEE main i suppose
- 2 years, 11 months ago
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So you want to say that they will post the result after 3 weeks or so.
- 2 years, 11 months ago
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perhaps, i have a friend who said such was the case last year, but you already know it since you qualified
- 2 years, 11 months ago
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Unless results are out, I can't say anything.
- 2 years, 11 months ago
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Yes forget it anyway, i just want the OCSC camp right now
- 2 years, 11 months ago
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Unable to reach hbcse website
- 2 years, 11 months ago
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Server not responding. Hopefully they are uploading result now.
- 2 years, 11 months ago
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Is anyone getting access to HBCSE website?I cannot wait anymore
- 2 years, 11 months ago
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http://www.downforeveryoneorjustme.com/http://olympiads.hbcse.tifr.res.in/
- 2 years, 11 months ago
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What is this.
- 2 years, 11 months ago
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I checked if the website is down and it says yes, the server is not responding.
- 2 years, 11 months ago
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Looks like the site is back again.
- 2 years, 11 months ago
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Do you have any Idea why results aren't out till now?
- 2 years, 11 months ago
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56 in inpho
- 2 years, 11 months ago
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Nice Marks,where do you go for coaching?
- 2 years, 11 months ago
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@Rishabh Garg How much did you get in INPhO?
- 2 years, 12 months ago
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Could you guys advice me for NSEJS. Please tell resources you used . Please don't see the levels and say 'you are already ready'.
Thanks in advance ! $$\ddot\smile$$
- 2 years, 12 months ago
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hey friends! please help me. I have got 41.5 in INPHO. However, from official solution, i should be getting around 50. Should i go for re-evaluation??
- 3 years ago
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Hey , I know It's off the Topic , But Please can anyone tell me from where I can get Previous Year free JEE MAINS ( AIEEE) paper's from , net . I did not get appropriate link !
I want specifically unsolved paper of AIEEE ! Thank's it will be great help!
- 3 years ago
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Unfortunately i dont solve AIEEE past papers, only JEE main and advanced mock tests so i do now know of any online source
- 3 years ago
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Here are from 2007 to 2010
- 3 years ago
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please post your incho marks. mine is 51.5
- 3 years ago
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Hey guys, I just received my performance card. I got 56.5, and there's a friend of mine who got 59.5. What do you think the qualifying score will be?
- 3 years ago
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please visit http://inpho-blogspot-2015.blogspot.in/
as for the cutoff, no one can predict with certainty, but it can be predicted very well if we know some of the highest marks, so please help
- 3 years ago
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@ALL- it would be of great help if any one could findout a few marks from Andhra pradesh students and report, because they performed exceptionally well in NSEP and knowing their inpho marks will undoubtably reveal significant data,
Also some of you are from Mumbai, so i suppose you can find out your friends marks as well as mumbai has serious talent,
Lastly i would also request those from Kota which is the hub of IIT JEE prep ,@Pranjal Jain to kindly tell any marks (good ones espectially) they know of their friends,
That would be great help :)
- 3 years ago
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Sorry I was busy, I'll let you know in the morning.
- 3 years ago
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ah bro, can you please let me know :) i am a bit tensed
- 3 years ago
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thanks, :)
- 3 years ago
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a small mistake happened. Please remove 54 from your list. I've got slightly higher(56). But I've posted it already in the blog mentioned by you. Sorry!!
- 3 years ago
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ok, i shall update it,
- 3 years ago
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i think the cutoff might go even higher than 64 as andhra prahesh students have scored much much higher than almost all of us present in this discussion
- 3 years ago
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indeed it can, it may even cross 70 ,
and hence i want you to please tell me some of their marks since you know ,
- 3 years ago
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i think you mistook me, sorry i was talking about marks about nsep and guessed about inpho
- 3 years ago
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ah,, you think, ok well , only time will tell,
But if you do get to know some marks, do share,
- 3 years ago
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two 56 should not come as i already told. That 56 already present is my score
- 3 years ago
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they have posted in the site you mentioned saw just now great scores
- 3 years ago
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Bro, i am unable to see, can you please tell me the scores, (comments are not getting loaded)
- 3 years ago
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Marks from AP: 64,64,69,71,72 Sheshank Agarwal got 69.5 (not from AP)
- 3 years ago
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Thank you, though i am glad that i am still in the game and not very far behind from them,
- 3 years ago
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Puts me out of the game for sure... ;)
- 3 years ago
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Same for me :p
- 3 years ago
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In response to Arpan Banerjee if you haven't received your certificate yet you can send an email to nc_olympiad@hbcse.tifr.res.in and they will send it by post. that's how I got mine.
- 3 years ago
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Thanks :) It just came in the post.
- 3 years ago
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Hey I got 42.5 in INAO and 45.5 in INPhO!!. Are there any chances???? I know it is not at all a good score!!.
- 3 years ago
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@Pranjal Jain said the cutoff for INPhO will be 45... But who knows..
- 3 years ago
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You are raising my hopes. By the way, Thank you!!.
- 3 years ago
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Please post the marks by candidates you know
- 3 years ago
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I did not receive my certificate for qualifying NSEP. I got one for qualifying NSEC when i went to give INCHO but I didn't receive after INPHO. What should I do?
- 3 years ago
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I received my nsep certificate today by post.Perhaps you should wait......
- 3 years ago
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Did you get it along with your performance card or seperately?
- 3 years ago
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Separately.
- 3 years ago
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Did you get 54?
- 3 years ago
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what about you?
- 3 years ago
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Just a 49 :(
- 3 years ago
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pranjal jain is saying that cutoff for inpho will be around 45. what do you think?
- 3 years ago
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do you know any other marks
- 3 years ago
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My friend got 38 but he was saying he might apply for re-evaluation.
- 3 years ago
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yes
- 3 years ago
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can you guys check out https://secure.hbcse.tifr.res.in/ipho2015/ . do we participants have to complete this form or is it for the olympiad supervisors. if we have to do it then what is our registeration code? Also can someone please explain how the bending of light about massive bodies is explained by a classical theory(it is the ipho logo for this year)?(http://www.ipho2015.in/ipho2015/logo)
- 3 years ago
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It seems that the link you have given is for countries to register for IPhO which is to be held in Mumbai this year.
- 3 years ago
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I am expecting around 40-45 marks in INPHO and similar in INCHO.. Won't be able to make the cut i guess. Haven't received the performance card yet though. It hasnt come today and there's no post on sunday so i think it'll come by monday.
- 3 years ago
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please post your inpho marks at this blogspot so i can make a statistical analsys ,if you wish :) (when the card arrives)
http://inpho-blogspot-2015.blogspot.in/
- 3 years ago
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@Mvs Saketh how to find field due to induced charges in electrostatics? asked in inpho to calculate force between a metallic sphere and a point charge
- 3 years ago
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Yeah use image theory, we can treat this situation as equivalent to a charge at centre with magnitude q+qR/D and another image charge in the usual position (at LD=R^2 point) (or inverse point of charge (external)) , with magnitude -qR/D and now calculate force using coulumbs law,
This question requires a much deeper understanding of image theory which i fortunately had due to solving many problems regarding it already from online websites,, i believe those who do not know image theory or only know the basics of it will take too long to figure this one out and hence might leave it,, i hope that helps me :P
- 3 years ago
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thanks, it helped me
- 3 years ago
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what is the performance card of inpho dated?
- 3 years ago
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Well, it is said around 19th in site, but also told to wait till 27th before contacting, more importanly, u must have given the exact address of your home or wherever you want to recieve it and the recievers details (if its not you)
- 3 years ago
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are there 2 teams for this years' inpho?
- 3 years ago
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I think IPhO will be held in India this year. So yes, there will be 2 teams
- 3 years ago
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Its ipho, but so what ? why two teams, if its a home game?
- 3 years ago
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I don't know the reason but I think yes, its a rule!
- 3 years ago
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maybe but either way it is mentioned in site that only 35 students selected from inpho but then the site is outdated
- 3 years ago
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I got 49.5 in inpho . just received my performance card. is there any chance of selection??
- 3 years ago
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@Pranjal Jain what do you think would be the expected cutoff for INPHO, this year, i know u didnt give but u might have heard something or so, i got 68 in inpho, , but yes definitely cutoff will be above 50 or 60, or god forbid 70, in which case i am done, but its not predictable,
but ur thoughts?
- 3 years ago
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68, you got it quite nice marks( monster marks), I am here just regretting over myself.
- 3 years ago
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actually bro i commited silly mistakes, i mean i am also tired of telling this repeatedly, but you wont believe that like a stupid idiot, i plotted even graph incorrectly, and almost questions answer part i got wrong values , even though i had a calculator, (because i did not properly plot graphs) i really thank the checker for step marking because if it was objective paper, i would have got 45 or so,
and well, trust me you would have found the paper pretty easy :) (except maybe the last question because it was not mentioned, assume Bohr quantisation, )
- 3 years ago
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this year's paper was difficult that last years' paper
- 3 years ago
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well bro both this year and last year paper was easy, except the black hole problem this year which i think is against the spirit of IPHO that sufficient information must be provided for questions out of syllabus,, and it is wrong to not mention that assume bohr quantisation in the question , because how can one know that a black hole proton atom behaves the same way as a hydrogen atom, also there were too many graphs this year, so indeed cutoff should be a bit lower,
but one thing is sure, it is not really so much paper dependent but more student dependent, if less people perform well, than low cutoff and so on, so no one can really predict, so just relax and wait till march 16
- 3 years ago
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i too had to leave that black hole problem for the very same reason.i thought this years inpho was a bit too mathematical(the 1st question itself) and calculative(the electrostatics question to find potential,thermodynamics question) which is against my liking. I knew almost no theory behind any of the graph questions but managed to get them right by pure mathematics(give any moron a bunch of values and he can plot the graph).According to me ,the best question(to check physics understanding) was the one in which they asked what would happen if angle of incidence=0(that glass slab question).and the hbcse guys answered that very elegantly too.Mathematics must only be used as a language to convey great ideas of Physics.The above question is the one in which one actually understands the meaning of limits(that we can answer for i=0+d and i=0-d (d is very small)but there is no such thing as i=0 exactly).
- 3 years ago
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Well , i agree with the black hole part and also that graph questions were stupid except for the inference from the graph, that was beautiful, like boiling point and latent heat, and yes give any moron values and he/she can plot a graph, that is very true.
But i rather think it was too experimental, and graphing doesnt check any ones innovation, rather electrostats problem was the most beautiful problem i think, but yes i agree one thing surely, that the values they gave sucked, i mean the numbers must be such that they cancel out and give a nice clean value so we know we are right and we can recheck, but the expressions in the electrostatic problems were very long and unfriendly,
- 3 years ago
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No idea but I am sure you are selected!! Congrats! =P
- 3 years ago
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i dont know bro, dont raise my hopes too much :P
because this year paper was bit easy , except for the black hole problem but i ended up doin too many stupid mistakes like forgetting to write a 2 in the denominator, plotting T vs t inplace of dT/dt vs t , and all, cost me much,
thanks to step marking though , well yes i can understand that ur statement is based on past year results like 60 percent cutoff in 2014 , and 50 percent was in 2013, but then it was 75 in 2012,,
i guess it all depends on my relative performance now, i hope others too have done silly mistakes like me :P
- 3 years ago
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Lol exactly =P
- 3 years ago
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i think i wont get it.....definitely
- 3 years ago
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i too did a silly mistake costing my 10 valuable marks
- 3 years ago
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is the answer to question 6(c) in inpho frozen solution correct?
- 3 years ago
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how much did u get, just curious, :) (in inpho)
- 3 years ago
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is the answer to 6(c) correct?
- 3 years ago
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sorry but can you please tell what the question was, just say like optics ka 3rd part, or say electrostats' 3rd part and so, i remember the whole paper but i dont know the numbers of each question
- 3 years ago
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black hole, finding energy to dissociate bhp
- 3 years ago
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oh i didnt do that one, i just left it as i have already said i found it hard :)
- 3 years ago
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oh ok but anyway i didn't notice that the question asked numerical answer and i wrote only the expression
- 3 years ago
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u wil definitely get step marking so chill
- 3 years ago
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havent received it yet?
- 3 years ago
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but i will definitely get less than u
- 3 years ago
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could inpho cutoff be above 53 and incho cutoff be above 50?????
- 3 years ago
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For INChO, yes
For INPhO, no
- 3 years ago
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according to tentative keys or corrected(yet to come) keys?
- 3 years ago
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According to corrected keys
- 3 years ago
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ok thanks
- 3 years ago
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What could be the expected cutoff for inpho and incho?
- 3 years ago
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INPhO- maybe 45, INChO- maybe 60
- 3 years ago
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but i think for inpho it wont be as low as 45 because this time it was for 100(total)
- 3 years ago
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I didn't took INPhO, that's what I have heard.
- 3 years ago
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thanks
- 3 years ago
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Comment deleted Feb 04, 2015
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Well, I qualified NSEA and NSEC, so I took INAO and INChO. Not expecting selection in either. Only 35 selections!
- 3 years ago
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No idea about cutoff! I'll let you know after getting some data from my friends. And never mind I really won't like to disclose my INChO marks as I totally messed it up!
- 3 years ago
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Did anybody get their INAO performance card??
- 3 years ago
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Yes, I got it.
- 3 years ago
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How much did you score??
- 3 years ago
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30
- 3 years ago
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Do you know anybody else's marks?What about INCHO?When will it come?
- 3 years ago
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Bhavya must be getting 70+, for INChO I got certificate of NSEC yesterday only.
- 3 years ago
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Even I got my olympiad certificates today.What are the highest scores there for other subjects?
- 3 years ago
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Can someone explain how the answer of Q4(a) is V2 = 4V/9 as given in the HBCSE answers?
- 3 years ago
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answer to that question is wrong
- 3 years ago
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IMR Press / JOMH / Volume 18 / Issue 11 / DOI: 10.31083/j.jomh1811211
Open Access Original Research
Health Perceptions of Korean and Japanese Adolescents During the Prolonged COVID-19 Pandemic: An Importance Performance Analysis
Show Less
1 Department of Physical Education, College of Education, WonKwang University, 54538 Ik San, Republic of Korea
2 Department of Physical Education, Graduate School of Education, Sogang University, 04107 Seoul, Republic of Korea
3 Department of Physical Education, Japan Women’s College of Physical Education, 157-0061 Tokyo, Japan
4 Department of Digital Business Japanese Jangan University, 18331 Hwasung-si, Republic of Korea
5 Department of Physical Education, College of Education, Korea University, 02841 Seoul, Republic of Korea
6 Department of Sports and International Studies, Ninppon Sport Science University, 158-8508 Tokyo, Japan
These authors contributed equally.
§These authors contributed equally.
J. Mens. Health 2022, 18(11), 211; https://doi.org/10.31083/j.jomh1811211
Submitted: 28 June 2022 | Revised: 29 July 2022 | Accepted: 8 August 2022 | Published: 11 November 2022
(This article belongs to the Special Issue Sports, Exercise and Physical Activities during the COVID-19 Pandemic)
This is an open access article under the CC BY 4.0 license.
Abstract
Background: This study compares and analyzes the importance and performance of Korean and Japanese adolescents’ health awareness in the long COVID-19 pandemic situation. Methods: A frequency analysis was conducted on data collected from 1341 Korean and Japanese adolescents in September 2021 through online and offline surveys to confirm their characteristics (reliability was verified through Cronbach’s $\alpha{}$). A paired sample test was conducted to analyze health awareness differences and performance of each variable between Korean and Japanese middle-school students and between male and female participants, substantiated by importance-performance analysis (IPA). Results: First, Korean adolescents perceived importance for all factors of health perception greater as compared to their Japanese counterparts. Second, performance differences between Korean and Japanese adolescents were especially significant in hygiene management, disease management and physical activity. Third, in Quadrant 4 of the IPA matrix, there were similarities and differences in a particular factor of health perception between Korean and Japanese adolescents. On this basis, we proposed measures emphasizing the importance of health, to enhance Korean and Japanese adolescents’ performance. Conclusions: It is important for national government, public education institutions, and families to couple a therapeutic approach with a preventive and management approach that encourages periodic exercise, desirable diet, and adequate sleep when exploring measures to maintain and promote adolescents’ health.
Keywords
importance-performance analysis
COVID-19
health perceptions
Korean
Japanese
1. Introduction
The onset of the coronavirus disease 2019 (COVID-19) in November 2019 and the consequent use of face masks and social distancing practices have significantly disrupted life as we know it [1]. Social distancing practices and a contactless way of life have been some of the key consequences of this changing world [1]. Experts predict the impossibility of returning to the pre-COVID-19 life even after the eradication of the virus [1]. It is anticipated that this contactless way of life will persist even post COVID-19.
Sedentary time increased, and physical activity reduced during the COVID-19 pandemic [2, 3]. Concerns about elevated sedentary time raised before the pandemic have intensified during the outbreak. Such lifestyle changes have increased the percentage of the obese [4]. Countries struck by COVID-19 report several psychological problems, including depression and anxiety [3].
These problems are not confined to the adult population but rage across adolescents as well [5, 6]. Schools—where Korean adolescents spend most of their day—have focused on anti-COVID-19 measures to halt the virus’s spread [4]. Indoor exercise facilities actively utilized by adolescents before the pandemic have closed. Other potential channels that could spread the virus, movement within schools and extracurricular sports activities (e.g., school sports clubs, afterschool sports, time fillers, Saturday sports day activity) have also been controlled [7]. Adolescents engage less in voluntary outdoor activities, as they fear contracting COVID-19. With controlled physical activities within and outside the school, adolescent health problems have emerged [8]. Educational authorities are sensitively reacting to these societal issues pertaining to academics and childcare. They focus on measures to run curricular physical education (PE) classes amid environmental changes provoked by the COVID-19 pandemic, such as online classes [9]. Educational interests in comprehensive issues of adolescent health and physical activity are minimal.
The situation is similar in Japan. The percentage of Japanese schools that implemented temporary closure of specific grade levels and classes in response to the prevalent COVID-19 cases was still high at 13.8% as of February 9, 2022, and 8.5% as of March 9, 2022 [10]. Amidst such conditions, 31.5% of elementary schools provided safe home exercise guides [10]. The percentages of schools providing exercise guidance decrease with advancing grade levels: 36.0% among elementary schools, 25.1% among middle schools, and 21.1% among high schools [10]. However, reduced physical activities have been reported across a range of age groups [11]. Concerns have been raised about the decline in children’s physical fitness [10], polarization of exercise habits [12, 13], decrease in physical activity and life satisfaction among college students [11, 14], and the decline of physical activity in the elderly [15].
Previous studies on adolescents’ health during the COVID-19 pandemic examined adolescents’ mental health, and most reported a deterioration in adolescent mental health during the pandemic. The COVID-19 pandemic elevated depression, anxiety, social isolation, maladaptation, stress, and physical health deterioration among adolescents [5, 14, 15, 16, 17, 18, 19]. Further, the prevalence of obesity has risen [20], and physical activities markedly declined among adolescents during the pandemic [21, 22, 23]. Many countries ordered the closure of indoor and outdoor sports facilities, such as swimming pools, playgrounds, and gyms [20]. Such measures limited adolescents’ physical activities and induced their social isolation [24]. Adolescent health-related quality of life (HRQoL) has reduced [25] with their lifestyle [5, 26, 27]. These can be attributed to the closure of schools, the primary place of physical activity among adolescents, or restrictions of physical activities within schools even after their reopening [28, 29]. In their importance-performance analysis (IPA) of health perceptions among Korean adolescents during the COVID-19 pandemic, Lee, So, and Youn [5] discovered disparities between therapeutic and preventive health factors. A follow-up study analyzed health perception differences according to the types of virtual Physical Education classes in transitioning from Physical Education classes to online classes [6].
The objective of this study is to conduct an empirical analysis by applying a modified IPA technique that divides Korean and Japanese adolescents’ health perceptions during the COVID-19 pandemic into six domains: mental health management, disease management, physical activity management, sleep management, diet management, and hygiene management. The specific research questions are as follows: First, we ascertain differences in the importance and performance of health perception between Korean and Japanese adolescents. Second, differences in importance and performance of health perception between male and female adolescents are ascertained. Finally, we examine differences in the importance-performance matrix between Korean and Japanese, male and female adolescents.
2. Materials and Methods
2.1 Participants
The study population comprised Korean and Japanese adolescents who took a PE class during the 2021 pandemic. A total of 1341 adolescents from two middle schoolers in Seoul, Korea (A, B) and two middle schools in Tokyo, Japan (C, D) were chosen as participants using convenience sampling, a nonprobability sampling method, from September to October 2021 (participants aged 13–15). Online (Google forms) and offline questionnaires were administered. Informed consent was obtained from all participants involved in the study. The results of the study participants are shown in Table 1.
Table 1.Participants’ demographic characteristics.
Characteristic Category Number (n) Percentage (%) Gender Male 617 46.0 Female 724 54.0 Nationality Korea (Seoul) 676 50.4 Japan (Tokyo) 665 49.6 Total 1341 100.0
2.2 Instruments
Instruments used in previous studies deemed appropriate for use were employed here. Participants’ demographics were set to gender and nationality, both assessed as nominal variables. The Health Perception Scale developed by Ware [30] and validated by Lee, So, and Youn [5]; and Yoo, Han, Youn, and Jung [6] was modified for use. Sub-variables were divided into six categories: mental health management, disease management, physical activity management, sleep management, eating habits management, and hygiene health management. They were assessed on a 5-point Likert rating scale with “strong yes” (5 points), “yes” (4 points), “normal” (3 points), “no” (2 points), and “not at all” (1 point). Each score was calculated independently. We used the IPA questionnaire in our study. IPA is an analysis method that evaluates importance and achievement to accurately pursue research goals, and it is used in various studies on educational program evaluation [31].
The IPA method was first used by Martilla and James [32] in the 1970s. IPA is used for customer satisfaction surveys in the marketing field. Recently, the judgment of its application and results has become concise and clear, so it is used in various studies such as those evaluating educational and experiential programs.
As it uses the average value of importance and satisfaction, the IPA method is not statistically complicated and has the advantage of being able to draw results quickly and easily. First, the importance-performance is measured. Second, the measured values are displayed on the X and Y axes’ coordinates of each of the four quadrants. Third, the implications are assigned based on the distribution of measured values in each section. The contents of the PA matrix are presented in Fig. 1 (Ref. [32]).
Fig. 1.
Importance – Performance Matrix [32].
In this way, the IPA method helps in effective improvement and development by confirming the problem’s priority or improvement direction through the survey results [31, 33]. The IPA method includes both traditional and modified techniques. Traditional IPA methods only concentrate on specific segments [34]. An alternative IPA survey was used to supplement this. This alternative IPA uses relative importance, making it possible to reflect perceptual changes to prevent problems concentrated in the second and third quadrants [34, 35]. Therefore, the revised method was used to obtain more accurate and reasonable results by supplementing the existing IPA method and its result problems.
2.3 Reliability of Instruments
We tested reliability using Cronbach’s $\alpha{}$ based on the criteria where a value of 0.80 or higher indicated good reliability, whereas 0.6 or lower implied low internal consistency [36]. Accordingly, a health perception sub-variable for Korean and Japanese adolescents was found to lie between 0.702 and 0.940.
This can be evaluated as high internal consistency because Cronbach’s $\alpha{}$ was 0.7, or higher than the standard of 0.6 [37]. A Cronbach’s $\alpha{}$ of 0.7 to 0.95 was also recognized as a confidence tolerance range [38]. The reliability of the item was judged to be high, and was used in this study. The reliability of verification results is shown in Table 2.
Table 2.Reliability analysis.
Variable Cronbach’s $\alpha$ Mental health management Importance 0.880 Performance 0.876 Disease management Importance 0.796 Performance 0.702 Physical activity management Importance 0.879 Performance 0.840 Sleep management Importance 0.864 Performance 0.793 Diet management Importance 0.851 Performance 0.743 Hygiene management Importance 0.940 Performance 0.884
2.4 Procedure and Data Collection
We collected data between June and October 2021 through online (Google forms) and offline questionnaires from Korean and Japanese adolescents. A pilot test was conducted on 300 Korean and 300 Japanese adolescents from June 1 to 30, 2021. The main questionnaire was administered between September and October 2021 to 1,433 (742 Korean, 691 Japanese) students. After excluding 7 questionnaires for missing responses and 85 questionnaires with unsuitable responses, a total of 1341 questionnaires were included in the analysis. Collected data were analyzed using the SPSS 18.0 software (IBM Corp., Armonk, NY, USA), from November 3 to 16, 2021. First, we analyzed participants’ demographic characteristics with frequency analysis. Second, we assessed the instrument’s reliability using Cronbach’s $\alpha{}$. Third, we conducted a paired sample test comparing the average value of each result to analyze differences in the degree of health awareness between Korean and Japanese middle-school students as well as the degree of importance and execution for each variable.
Finally, to verify each variable’s importance and execution, a modified IPA was conducted [33] from December 1 to 10, 2021. Results of the traditional IPA indicated that the attributes of importance and achievement were not mutually independent, which could lead to misinterpretation [32, 39, 40]. In contrast, modified IPA can prevent the problem of concentrating attributes on quadrants I and III of the traditional method, reducing errors and yielding more accurate results [34]. The data collection analysis and text writing were translated into Korean, Japanese, and English for a cross-review by both Korean and Japanese authors.
3. Results
3.1 Importance and Performance Comparisons of Korea and Japan
First, a paired samples t-test was performed to compare perceived importance between Korean and Japanese adolescents, and statistically significant differences in the perceived importance for all variables were noticed. Second, a paired samples t-test to examine differences in performance between Korean and Japanese adolescents. There were statistically significant differences in health perception between the two countries for mental health, disease management, physical activity, and hygiene management, but not for sleep management and diet management. The results are shown in Table 3.
Table 3.Importance and performance comparisons between Korean and Japanese adolescent.
Variable Korea Japan T p M SD M SD Mental health management Importance 4.57 0.51 4.30 0.75 7.550*** 0.000 Performance 4.02 0.73 3.92 0.85 3.032** 0.002 Disease management Importance 4.58 0.53 4.37 0.74 5.992*** 0.000 Performance 4.23 0.66 4.17 0.78 3.375** 0.001 Physical activity management Importance 4.23 0.74 4.06 0.88 4.045*** 0.000 Performance 3.52 1.02 3.36 1.09 3.370** 0.001 Sleep management Importance 4.46 0.63 4.31 0.81 3.934*** 0.000 Performance 3.58 0.95 3.59 0.95 0.763 0.446 Diet management Importance 4.40 0.68 4.28 0.85 2.973** 0.003 Performance 3.79 0.88 3.90 0.89 –1.283 0.200 Hygiene management Importance 4.69 0.46 4.47 0.72 6.484*** 0.000 Performance 4.42 0.54 4.24 0.71 5.339*** 0.000 ***p $<$ 0 .001, **p $<$ 0.01, *p $<$ 0.05.
3.2 Importance and Performance Comparisons between Gender
First, we performed a paired samples t-test to compare perceived importance between male and female adolescents. Statistically significant differences in the importance of gender were found only in physical activity. Second, we performed a paired samples t-test to examine differences in the performance between male and female adolescents. A statistically significant difference between the performance of both genders in physical activity, sleep management, meal management, and systemic health was noticed. However, hygiene and disease management did not show a statistically significant difference. The results are shown in Table 4.
Table 4.Importance and performance comparisons between male and female adolescents.
Variable Male Female t p M SD M SD Mental health management Importance 4.45 0.66 4.42 0.65 0.753 0.452 Performance 4.05 0.79 3.93 0.78 2.622** 0.009 Disease management Importance 4.49 0.65 4.47 0.65 0.657 0.511 Performance 4.28 0.69 4.21 0.73 1.789 0.074 Physical activity management Importance 4.20 0.82 4.11 0.80 2.092* 0.037 Performance 3.63 1.05 3.32 1.04 5.394*** 0.000 Sleep management Importance 4.42 0.73 4.37 0.71 1.154 0.249 Performance 3.82 0.92 3.43 0.92 7.839*** 0.000 Diet management Importance 4.37 0.76 4.32 0.76 1.128 0.260 Performance 3.95 0.90 3.80 0.85 3.297** 0.001 Hygiene management Importance 4.56 0.60 4.59 0.62 –1.020 0.308 Performance 4.31 0.65 4.34 0.64 –0.866 0.386 ***p $<$ 0 .001, **p $<$ 0.01, *p $<$ 0.05.
3.3 IPA for both Countries and Genders
First, we generated the IPA matrix for Korean adolescents with the mean importance score of 4.49 and mean performance score of 3.93 as the reference values. The IPA matrix for Japanese adolescents was generated with the mean importance score of 4.30 and mean performance score of 3.86 as the reference values. The results are displayed in Table 5 and Fig. 2.
Table 5.Health perception factor distribution in Korean and Japanese, male and female adolescents.
Category Criteria Group Factor distribution Quadrant I (Concentrate here) Importance↑, Performance↑ Country Korea hygiene management, disease management, mental health management Japan hygiene management, disease management, mental health management Gender Male hygiene management, disease management, mental health management Female hygiene management, disease management, mental health management Quadrant II (Keep up the good work) Importance↑, Performance↓ Country Korea none Japan sleep management Gender Male none Female none Quadrant III (Low priority) Importance↓, Performance↓ Country Korea physical activity management, sleep management, diet management Japan physical activity management Gender Male physical activity management, sleep management, diet management Female physical activity management, sleep management, diet management Quadrant IV (Possible overkill) Importance↓, Performance↑ Country Korea none Japan diet Gender Male none Female none
Fig. 2.
IPA Matrix – Factors (countries).
Second, we generated the IPA matrix for male adolescents with a mean importance score of 4.42 and a mean performance score of 4.01 as the reference values. The IPA matrix for female adolescents was generated with the mean importance score of 4.38 and mean performance score of 3.84 as the reference values. The results are displayed in Table 5 and Fig. 3.
Fig. 3.
IPA Matrix – Factors (gender).
4. Discussion
This study analyzed the perceived importance and performance of health-related factors during the COVID-19 pandemic among Korean and Japanese adolescents using the IPA. It discussed its major findings considering previously published research.
First, Korean adolescents perceived all health-related factors as compared to their Japanese counterparts. Specifically, its importance for each population markedly differed for categories of “mental health”, “hygiene management”, “disease management”, “physical activity”, and “sleep management”.
Such differences are evident in the health levels and health-promoting policies of the two countries. Japan boasts the best global health and health achievement, while Korea is not included in the top 30 countries for these indices [41]. We can conclude that Japan has achieved a high level of health, where individuals have managed their own health, facilitated by the implementation of national health-promotion policies since the 1970s. Another key reason underlying this achievement is that Japanese schools impart knowledge about disease prevention, including infections through PE and health education classes, from elementary school to high school [42, 43, 44]. In Korea, national health-promotion policies implemented in the 2000s are still being actively enforced [45]. Therefore, Korean adolescents, more exposed to Korean versions of health-promotion projects led by both national and local governments and schools, perceive the importance of health. Conversely, Japan currently promotes individual health management, evidenced by the fact that a mandatory lockdown was never enforced in Japan during the COVID-19 pandemic despite school closure orders. Japanese adolescents are thus less exposed to health-promoting policies, as compared to their Korean counterparts, probably contributing to their relatively low perceived health importance.
Korean adolescents showed higher performance in four health domains, while performance did not differ in two domains for either population. Performance in “hygiene management”, “disease management”, and “physical activity” significantly differed between the two populations.
National and local government-led anti-COVID-19 measures—the K anti-infection system—including school closure and conversion to online courses, have enhanced Korean adolescents’ hygiene management and disease management [45]. The Japanese Ministry of Education, Culture, Sports, Science and Technology actively publishes reference materials dealing with prevalent infections, and adolescents actively engage in independent hygiene management or disease management [46, 47]. Japan provided many PE and club activities in schools before the COVID-19 pandemic through which students engaged in adequate physical activity [41, 48, 49]. In Korea, since 2010, schools have implemented several activities through PE, sports clubs, sports leagues, afterschool activities, and Saturday sports [45]. The COVID-19 pandemic hit both countries at a crucial time, with schools implementing distancing, no physical contact policies, and limited PE classes, in response to the pandemic. Japanese adolescents’ physical activities seem more influenced by such measures.
Second, male adolescents attach more importance to the “physical activity” factor than female adolescents. This was confirmed even before advent of the COVID-19 pandemic [50]. It is believed that this preference for physical activity among boys more than girls continues through the pandemic. Male adolescents showed higher practical performance for factors of “sleep management”, “physical activity”, “meal management”, and “mental health” than female adolescents, and there were no perceived differences in “hygiene” and “disease management” factors. We can interpret “sanitation management”, “disease management”, and the actual ability of both men and women to implement them, as successful anti-epidemic policies of the governments, municipalities, and school sites for both countries. There was no significant difference between male and female adolescents [10]. With the low ability of female adolescents to implement “sleep management”, “physical activity”, “meal management”, and “mental health”, developing and applying various educational programs to solve these problems is necessary. Regarding female adolescents’ “physical activity” factors, which are relatively low as compared to male adolescents in both importance and implementation, the program takes into account the emotions of female adolescents determined by the COVID-19 pandemic situation [51] and implements various program strategies [52] to overcome prejudice.
Quadrant II factors indicate high importance but low performance, and factors in this quadrant call for urgent improvement. None of the health-related factors for Korean male and female adolescents belonged in this quadrant. However, “sleep management” was placed in this quadrant for Japanese adolescents. Japanese adolescents have been reported to sleep longer during the COVID-19 pandemic [58], indicating poor sleep quality (e.g., regularity, deep sleep) [37]. Actively promoting sleep management, including sleep quality, is as essential as imparting its importance to adolescents amid the extended pandemic.
Quadrant III factors (low priority) indicates low importance and performance and do not require more improvement beyond the current level. For Korean male and female adolescents, physical activity, sleep management, and diet, had low importance and performance. For Japanese adolescents, only physical activity was placed in this quadrant.
The problems of diet and sleep among Korean adolescents are attributable to the irregularity of in-person school days and online classes during the COVID-19 pandemic. Students enjoy regular, nutritionally balanced meals when going to school; they however have difficulty consuming meals regularly or enjoying nutritionally balanced meals during online learning. They often skip breakfast, lunch, or eat hurriedly due to short lunchtime [59, 60]. Students also enjoy late-night snacks, and even physically attending school, eat quickly or inadequately to prevent contracting COVID-19. The increased rate of junk food consumption is a critical cause of diet-induced health problems. Adolescents’ consumption of junk foods such as carbonated drinks, fast food, and ramen, leads to poorly balanced diets of vegetables, fruits, milk. This impairs health, both directly and indirectly, causing stress, depression, and poor self-evaluations of health [61]. Our results that adolescents showed low perceived importance and performance regarding diet management could be due to the COVID-19 pandemic hindering the formation of diet values [62].
Frequent online classes, exposure to digital media and a smartphone-centered lifestyle caused by restrictions in daily living and physical activities adversely affect their sleep [5, 40]. These results are in line with pre-COVID-19 reports of adolescent health negligence [63]. They suggest that while adolescents perceive the importance of COVID-19 prevention and treatment since the pandemic outbreak, they lack interest in practicing routine behaviors to maintain and promote their health, including sleep and diet management. Education about diet, sleep management, and physical activity should be coupled with interventions that promote these activities. These could prove useful for Korean adolescents amid the prolonged pandemic.
Notably, adolescents from both countries, of both genders showed the lowest importance and performance for physical activity. Scholars worldwide have warned that extended suspension of face-to-face education and outdoor activities during the COVID-19 pandemic exposes students to risks such as obesity, diabetes mellitus, and hypertension [64, 65, 66]. Activity-focused PE classes offered in Korean and Japanese schools have been replaced by hybrid (online + offline) PE classes because of the pandemic. Club and school programs involving sports and physical activities have been restricted [9, 67]. Inadequate engagement in various extracurricular and leisure activities could also have contributed to the low perception of importance and practice of physical activity. Adolescents gained bodyweight faster during school breaks than during school semesters, even before the COVID-19 pandemic [62]. While school classes are currently conducted in a hybrid format, in terms of the amount of physical activity, the pandemic situation is like an extension of the summer break for students. Prior to the pandemic, students could engage in considerable physical activity by commuting to school and back, and participating in various activities, including PE classes [38, 67].
Physical activity is key to a healthy lifestyle, and has evidence-based effects on improvement of physical health (e.g., obesity, physical fitness), mental health (e.g., anxiety, depression, happiness), social life, and lifestyle [68, 69]. Further, physical activity contributes to individuals’ health not only during adolescence but throughout their lives [70]. A sedentary lifestyle undermines human life, evidenced by it being the fourth leading cause of death. Physical activity contributed to mental well-being even during the COVID-19 pandemic [3], and is a non-invasive, cost-effective means of protecting one’s body from viruses by boosting the immune system [4]. Physical activity programs should be systematically designed to involve moderate- to vigorous-intensity exercise instead of simply lengthening the duration of physical activity. A longitudinal study conducted on Japanese adolescents found a significant association between sports club participation during adolescence and reduced mortality risk from cardiovascular disease in adulthood [71]. In Korea, both PE programs and music-incorporated PE programs have been developed to promote adolescent health [72]. Other countries too currently run school-based moderate- to vigorous-intensity physical activity programs for adolescents. Some prime examples are “TAKE 10!” in the United States, the “Schools on the Move” in Finland, and “Smart Moves” in Australia [67]. Several European countries such as France, Germany, and Ireland also provide students with opportunities to participate in diverse moderate- to vigorous-intensity physical activity programs through school PE classes and afterschool programs [73].
It is important to expand opportunities for student participation in systematic moderate- to vigorous-intensity physical activity to promote ideal physical growth and immunity in Korean and Japanese adolescents. Amidst the prolonged COVID-19 pandemic, designing and implementing programs that comprise educational and practice-promoting aspects and consider all health-related factors are essential. This is in opposition to comparing the ranking or levels of diet, sleep management, and physical activity between Korean and Japanese adolescent populations.
Quadrant IV (possible overkill) indicates low importance but high performance and its factors are perceived to be less important than others but practiced more than necessary. Although none of the health-related factors present in this quadrant for Korean male and female adolescents, “diet” was placed in this quadrant for Japanese adolescents. It is highly likely that Japanese adolescents do not perceive diet to be as important as other health-related factors because Japanese culture features enjoyment of small portions of food [41, 74]. As Japan has a well-developed school meal system, adolescents demonstrate high performance in natural diet management [71]. In other words, Japanese people have extremely positive values toward diet culture. It is therefore important to educate Japanese adolescents about the importance of diet and the values of the good eating culture of their country. This will help adolescents practice their current eating culture more effectively and foster a healthier eating culture.
5. Conclusions
Our study presents data on the relationship between perceived importance and performance of health-related factors among Korean and Japanese adolescents, their strategic priorities, as well as health perception disparities between the two groups. These will help evaluate school PE education during the COVID-19 pandemic and design future curricula. Our findings will also provide public and private educational institutions valuable foundational data, to plan and enforce health education, in preparation for the post-COVID-19 era.
It is important for national, government, and public education institutions, and families to couple a therapeutic approach with a preventive and management approach, one that encourages periodic exercise, desirable diet, and adequate sleep while exploring measures to maintain and promote adolescent health. First, the national government, local governments, and schools should continue promoting and educating adolescents in hygiene management, disease management, and mental health management from a therapeutic perspective, to maintain the status quo. Special efforts are also required from both schools and families to manage diet, sleep, and physical activity in both countries, from a preventive perspective.
Physical activity was identified as the most vulnerable health-related factor for Korean and Japanese adolescents, calling for the development of various remote PE programs and efforts to facilitate PE activities during in-person sessions. School curricula must be modified to promote physical activity by promoting in-person PE classes, sports clubs, afterschool sports activities, school sports club leagues, and Saturday sports. To this end, the Office of Education, schools, relevant organizations, teachers, and parents must make the necessary efforts to improve school curricula.
Subsequent studies should expand this sample to more countries, local- and school-grade groups, and comparatively analyze their results with our findings. In-depth interviews, observations, and document analyses are needed to enable a broader and deeper interpretation of IPA results for students and teachers. A mixed methods methodology should be utilized towards more dynamic, persuasive findings and implications.
Author Contributions
H-SY, E-JL, C-MK, and YO designed and conducted the research study. H-SY, E-JL, SR, CM, C-MK, and YO collected and analyzed the data. H-SY, E-JL, C-MK, and YO interpreted the data. E-JL, CM, C-MK, and YO drafted the manuscript. H-SY, E-JL, CM, and YO revised the manuscript’s content. All authors read and approved the final manuscript.
Ethics Approval and Consent to Participate
This study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board (or Ethics Committee) of Wonkwang University in Korea (WKIRB-202009-SB-053) and the Nippon Science University (IRB) (NSSUIRB-021-H083). Informed consent was obtained from all participants.
Acknowledgment
Not applicable.
Funding
This paper was supported by Wonkwang University in 2022.
Conflict of Interest
The authors declare no conflict of interest.
Publisher’s Note: IMR Press stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Publisher’s Note: IMR Press stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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# Bibliothèque
## I Used to Have a Best Friend (But Then He Gave Me an STD)
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## Abstract and Applied Analysis
### A Novel Data-Driven Fault Diagnosis Algorithm Using Multivariate Dynamic Time Warping Measure
#### Abstract
Process monitoring and fault diagnosis (PM-FD) has been an active research field since it plays important roles in many industrial applications. In this paper, we present a novel data-driven fault diagnosis algorithm which is based on the multivariate dynamic time warping measure. First of all, we propose a Mahalanobis distance based dynamic time warping measure which can compute the similarity of multivariate time series (MTS) efficiently and accurately. Then, a PM-FD framework which consists of data preprocessing, metric learning, MTS pieces building, and MTS classification is presented. After that, we conduct experiments on industrial benchmark of Tennessee Eastman (TE) process. The experimental results demonstrate the improved performance of the proposed algorithm when compared with other classical PM-FD classical methods.
#### Article information
Source
Abstr. Appl. Anal., Volume 2014 (2014), Article ID 625814, 8 pages.
Dates
First available in Project Euclid: 6 October 2014
https://projecteuclid.org/euclid.aaa/1412606637
Digital Object Identifier
doi:10.1155/2014/625814
Zentralblatt MATH identifier
07022760
#### Citation
Mei, Jiangyuan; Hou, Jian; Karimi, Hamid Reza; Huang, Jiarao. A Novel Data-Driven Fault Diagnosis Algorithm Using Multivariate Dynamic Time Warping Measure. Abstr. Appl. Anal. 2014 (2014), Article ID 625814, 8 pages. doi:10.1155/2014/625814. https://projecteuclid.org/euclid.aaa/1412606637
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Thread: Prove that for every prime p, there is an irreducible quadratic in Z_p[x]
1. Prove that for every prime p, there is an irreducible quadratic in Z_p[x]
Prove that for every prime p, there is an irreducible quadratic in $Z_p[x]$ (the polynomial ring of the integers mod p).
I have not been able to wrap my brain around this one. Does anyone have any ideas?
I have been looking at $x^2+x+1$ and $x^2+1$, but haven't been able to derive a contradiction.
This is what I have so far: Assume $x^2+1$ is reducible in $Z_p[x]$. Then, $\exists a,b\in Z_p[x]$ s.t. $x^2+1=(x-a)(x-b)=x^2-(a+b)x+ab\Rightarrow a+b=0, ab=1$
Thanks!
2. Originally Posted by Dark Sun
Prove that for every prime p, there is an irreducible quadratic in $Z_p[x]$ (the polynomial ring of the integers mod p).
I have not been able to wrap my brain around this one. Does anyone have any ideas?
I have been looking at $x^2+x+1$ and $x^2+1$, but haven't been able to derive a contradiction.
This is what I have so far: Assume $x^2+1$ is reducible in $Z_p[x]$. Then, $\exists a,b\in Z_p[x]$ s.t. $x^2+1=(x-a)(x-b)=x^2-(a+b)x+ab\Rightarrow a+b=0, ab=1$
Thanks!
if p = 2, consider $x^2 + x + 1.$ for p > 2, choose $a \in \{1, \cdots, p-1 \}$ such that $a$ is not a quadratic residue modulo p. then $x^2 - a$ would be irreducible in $\mathbb{Z}_p[x].$
3. Thanks Dark Knight, this is just the answer I was looking for.
You have helped me a great deal.
I wish you well in your studies!
4. Originally Posted by Dark Sun
Prove that for every prime p, there is an irreducible quadratic in $Z_p[x]$ (the polynomial ring of the integers mod p).
Here is another approach but this is not a good approach at all.
Let $f(x) = x^{p^2} - x$ and let $K$ be its splitting field.
Then we have that $[K:F]=2$, pick any $a\in K - F$ then the minimal polynomial of $a$ must have degree $2$.
Thus, you have found an irreducible polynomial of degree 2.
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# Rambling Thoughts
## ARML
ARML (American Regions Mathematics League) is an annual math contest that takes place every year at four sites around the country. It’s one of my favorite math contests.
ARML is different from most other math contests because it requires teams to travel to one of four central sites. This means that teams have to travel (some times for very long distances) to participate. Inevitably, this means that participation at ARML is not especially high; only 124 teams of fifteen people (in 2010), or less than one percent of the more than 200000 people who participated in the AMC. Teams that do participate at ARML, however, are much more organized; most teams organize several practices before the contest, while some teams prepare for ARML year-round. The team aspect of the contest (3 out of 4 rounds have a team component, together constituting 50% of the total team score) also makes ARML stand out. Indeed, ARML is primarily a team contest, and the team results every year are watched much more closely than the individual high scorers. As a result, ARML is much more social than most other math contests, giving participants a chance to work closely with their team and to meet people from other teams. This social aspect of ARML is what makes ARML enjoyable.
Mathematically, ARML feels different from most other contests. The ARML style is to have problems that look hard but are made much easier through clever tricks. Often, these problems can be solved without being clever, but cleverness can often yield very simple solutions. As an example, consider this year’s coffee mug problem: [EDIT (17 September 2010): Updated with the original wording.]
Let $P(x) = x^2 + 2010 x + 2010$, and let $r$ and $s$ be the roots of $P$. If $Q$ is a quadratic polynomial with leading coefficient 1 and roots $r + 1$ and $s + 1$, compute the sum of the coefficients of $Q(x)$.
This can be bashed out without the quadratic formula or with Vieta’s formulas, but the clever solution is much simpler:
Because $Q$ is monic,
$Q(x) = (x - (r+1))(x - (s+1))$
$= ((x - 1) - r)((x - 1) - s) = P(x-1)$. The sum of the coefficients of $Q(x)$ is $Q(1) = P(0) = 2010$.
Together with the clever tricks, ARML imposes a short time limit on its tests, making it difficult for contestants to finish the team and individual tests. The relay round’s three-minute and six-minute time limits provides a further emphasis on speed. As a result, ARML problems (with the exception of the proof-based Power Question) are usually not very hard mathematically; they’re just hard to do under severe time pressure. This short time limit, along with the small number of questions on ARML, make the results of the contest subject to a lot of random noise. The top teams are usually within a few points (out of 300 points total) of each other, so a five-point team round problem could easily change a team’s ranking by several places. The individual round has only ten problems, so achieving a national high score (usually at least eight problems) requires making no computational errors. Thus, the list of individual high scorers is somewhat meaningless; high scorers often do not repeat as high scorers when they return, and high individual scorers are often as much a result of luck as of mathematical ability.
Evaluating ARML based on the criteria that I listed in my post on Contest Math, we obtain mixed results. ARML, perhaps more than any other contest, highlights the social side of mathematics and hooks people into liking and doing math; though it’s hard to start doing ARML, it’s even harder to stop. Mathematically, though ARML does reinforce the importance of creativity, it does not give particularly challenging problems, and ARML results do not really constitute a good measure of mathematical achievement.
I enjoy ARML primarily based on the social part of the contest, and many people agree with me; the highlight of ARML for some people is the long bus ride to the contest. Indeed, I think of ARML primarily as a social event, with some mathematics to make it look like the participants are actually doing something important.
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###### How to determine epsilon and MinPts parameters of DBSCAN clustering
December 18, 2020
###### Maximum Likelihood Estimation (MLE) and Maximum A Posteriori (MAP) Simply explained
February 8, 2021
http://activisiongamescience.github.io/2016/01/11/Implicit-Recommender-Systems-Biased-Matrix-Factorization/
In today’s post, we will explain a certain algorithm for matrix factorization models for recommender systems which goes by the name Alternating Least Squares (there are others, for example based on stochastic gradient descent). We will go through the basic ALS algorithm, as well as how one can modify it to incorporate user and item biases.
We will also go through the ALS algorithm for implicit feedback, and then explain how to modify that to incorporate user and item biases. The basic ALS model and the version from implicit feedback are discussed in many places (both online and in freely available research papers), but we aren’t aware of any good source for implicit ALS with biases… hence, this post.
## Introduction
Recommendation engines are becoming ubiquitous in the modern consumer landscape. From Netflix’s personalized movie recommendations to Amazon’s raft of suggested items (New For Your, Recommendations for You in the Kindle Store, etc…), to Spotify’s wildly popular personalized Discover Weekly Playlist, recommendation engines have become an essential tool for promoting content discovery and extending consumer engagement.
There has been a proliferation of algorithms in the data science community upon which recommender systems are built, but they all follow the basic central dogma that similar users like similar items. The hard part, of course, is deciding exactly what “similar” means and how to measure it. For Netflix, similar users are users who rate movies similarly. For Spotify, similar users are users who listen to the same kinds of music (a little thought will convince you that these two ideas, while similar, are not really the same).
The simplest type of recommender system, called a collaborative filter, is essentially a literal interpretation of “similar users like similar things” Goldberg1992. Once a metric for similarity is decided on, one just looks at the top rated items of the kk nearest neighbors (with respect to the similarity metric), filters out those items which the user of interest has already seen/consumed, and voila: personalized recommendations.
Collaborative filters have the advantages of being relatively easy to implement and relatively easy to interpret (e.g. we recommended movie A to user 1 because users 2, 3, and 4 all rated it highly and have similar ratings profiles to user 1). This being the Age of Data Science, though, it is no longer enough to have a reasonable explanation. We can actually measure how effectively a recommender system predicts the ratings of users on unseen items. Thus began Netflix’s famous quest for better recommender systems, leading to the famous million dollar prize and eventual solution Bell2008 (by a team of experts working for several years).
Although the recommender system that won the Netflix prize was never put into production (it was a carefully tuned mix of many statistical models, and the marginal gain obtained by implementing all of the models was not worth the technical price compared to simply implementing a few of the best ones), the data science community, and the wider commercial world, learned without a doubt that, while collaborative filters are explainable and easily implementable, one can do significantly better if one is willing to flex a bit of mathematical muscle.
There were essentially two types of recommender systems in the final solution to the Netflix prize, and they have become the bread and butter of the current state of the art: matrix factorization models and restricted Bolzmann machines (RBMs). We will discuss matrix factorization models in this post.
We will be interested in two refinements of the basic matrix factorization model for recommendations: using implicit feedback, and using user and item biases.
## User and Item Biases
It was realized early on, even for collaborative filters, that recommender systems work a lot better if one accounts for user and item biases.
Suppose, for example, that we are trying to predict movie ratings and
• Bob is grouchy and rates items with an average of 2 stars.
• Alice is chipper and cheery and rates things with an average of 4 stars.
Clearly 3 stars from Bob is very different than 3 stars from Alice. If we keep track of the average movie rating for each user (the user bias), and just try to predict the difference from that average, the recommender system works much better.
Similarly, suppose
• Snakes on a Plane gets an average rating (over all users) of 1 star.
• The Shawshank Redemption gets an average rating of 5 stars.
Then a 3 star rating is very different for Snakes on a Plane than for The Shawshank Redemption. If we keep track of the average user rating for each movie (the item bias), and just try to predict the difference from that average, the recommender system also works much better.
Obviously, one should keep track of both user and item biases. (We will explain the technical details below.)
## Implicit Feedback
One of the challenges of recommender systems in the wider commercial world is that one rarely has explicit ratings data (Netflix strongly encourages users to rate movies and leverage the tech built around those ratings).
Instead, user-item interactions like clicks, purchases, song listens (or fast-forwards), etc, are used as a proxy to indicate a preference or distaste for a particular item (possibly very weakly). If a user listens to a song only once, maybe it indicates that they didn’t like the song. However, maybe they were busy or weren’t paying attention and actually would like to hear the song again. If a user listens to a song 100 times, it is a safe bet that they like the song. But it is hard to draw a line between unknown preference and known preference.
This kind of indirect information about user-item preferences is known as implicit feedback, and many smart people have thought long and hard about how to deal with it. We won’t delve much into the modeling of implicit feedback in today’s post. It turns out to be relatively effective to model a user’s preference on a scale of 0 (bad) to 1 (good) instead of modeling the user’s raw number of interactions (or whatever number is actually being measured).
We can interpret the number of user-item interations (song listens, for example) as a measure of our confidence in our model’s prediction for the user’s preference of the item.
Below, we’ll step through the details of how a matrix factorization model can be used to deal with implicit feedback. The basic algorithm we discuss is from the seminal paper Hu2008.
## Basic Matrix Factorization for Recommendations
The most basic matrix factorization model for recommender systems models the rating r^r^ a user u would give to an item i byr^ui=xTuyi,r^ui=xuTyi,
where xTu=(x1u,x2u,…,xNu)xuT=(xu1,xu2,…,xuN) is a vector associated to the user, and yTi=(y1i,y2i,…,yNi)yiT=(yi1,yi2,…,yiN) is a vector associated to the item. The dimension of the vectors is the rank of the model, and the components are called factors.
We can collect the user-item ratings into a matrix Rˆ=(r^ui)R^=(r^ui). First collect the user vectors into a matrixXT=⎛⎝⎜⎜⎜⋮xu1⋮⋮xu2⋮⋯⋯⋯⋮xunusers⋮⎞⎠⎟⎟⎟,XT=(⋮⋮⋯⋮xu1xu2⋯xunusers⋮⋮⋯⋮),
and the item vectors into a matrixYT=⎛⎝⎜⎜⎜⋮yi1⋮⋮yi2⋮⋯⋯⋯⋮yinitems⋮⎞⎠⎟⎟⎟,YT=(⋮⋮⋯⋮yi1yi2⋯yinitems⋮⋮⋯⋮),
then we can express the above model asRˆ=XYT.R^=XYT.
Of course, there is no reason that the “true” user-item matrix R=(rui)R=(rui) should have rank NN, and indeed, we won’t even know the “true” user-item matrix. This model assumes that it can be approximated by a rank NN factorization:R∼Rˆ=XYT.R∼R^=XYT.
In other words, we want to find an nusers×Nnusers×N matrix XX and an nitems×Nnitems×N matrix YY such that Rˆ:=XYTR^:=XYT approximates RR.
Remark We follow the matrix conventions of Hu2008, and machine learning in general. Although the user- and item-factor vectors xuxu and yiyi (and vectors in general) are regarded as column vectors, they are arranged as rows into the composite matrices XX and YY.
## Alternating Least Squares
One popular method for finding the matrices XX and YY given partial information about RR is known as alternating least squares. The idea is to find the parameters xjuxuj and yjiyij (the entries of the matrices XX and YY) which minimize the L2L2 cost functionC=∑u,i∈observed ratings(rui−xTuyi)2+λ(∑u∥xu∥2+∑i∥yi∥2).C=∑u,i∈observed ratings(rui−xuTyi)2+λ(∑u‖xu‖2+∑i‖yi‖2).
The constant λλ is called the regularization parameter and essentially penalizes the components of the matrices XX and YY if they get too large (in magnitude). This is important for numerical stability (and some kind of regularization is almost always used). It has an even more important effect in this setting, though:
Fundamental Observation: If we hold the item vectors YY fixed, CC is a quadratic function of the components of XX. Similarly, if we hold the user vectors XX fixed, CC is a quadratic function of the components of YY.
So in order to minimize CC, one could try the following:
1. Hold the user vectors fixed and solve the quadratic equation for the yjiyij’s. This will (probably) not be the global minimum of CC since we haven’t touched half of the variables (the xjuxuj’s), but we have at least decreased CC.
2. Hold the item vectors fixed and solve the quadratic equation for the xjuxuj’s.
3. Repeat.
Some remarks are in order.
• Since CC is a convex function, and each step of the above algorithm is a minimization, the process must converge at some point.
• There are other methods for minimizing such a convex cost function, for example, gradient descent (or stochastic gradient descent, or batch SGD, etc…). One important difference here is that at each step of our algorithm, we find the exact minimum; we don’t take small steps in a downward direction. So if we do step 1), a second application of step 1) will have no effect: we’re already at the absolute minimum of CC with YY held fixed. It also means that a single iteration of the above algorithm generally moves much further than an iteration of a gradient descent algorithm; i.e. we need fewer iterations for convergence.
The above algorithm is called (for obvious reasons) alternating least squares.
A bit of linear algebra yields the following algorithm (see here, for example):
### Alternating Least Squares (ALS)
1. Initialize the user vectors XX somehow (e.g. randomly).
2. For each item i, let riri be the vector of ratings of that item (it will have n_users components; one for each user). Computeyi=(XTX+λI)−1XTriyi=(XTX+λI)−1XTrifor each item i. (II is the N×NN×N identity matrix.)
3. For each user u, let ruru be the vector of ratings of that user (it will have n_items components; one for each item). Computexu=(YTY+λI)−1YTruxu=(YTY+λI)−1YTrufor each user u.
4. Repeat 2), 3) until desired level of convergence is achieved.
Remark. It is almost always faster to solve the linear system (XTX+λI)yi=XTri(XTX+λI)yi=XTri instead of inverting the matrix (XTX+λI)(XTX+λI) as written in the algorithm (similarly for the user vectors).
## User and Item Biases
As we mentioned above, it turns out that most recommender systems perform better if user and item biases are taken into account.
Suppose we have a ratings system that allows each user to rate each item on a scale of 1 to 5 stars. Suppose we have two users: Alice, who rates items with an average of 4 stars, and Bob, whose average rating is 1.5 stars. If Bob rates some new item with 3 stars, it means something very different than if Alice rates the same item with 3 stars (Bob really liked the new item, Alice didn’t). The difference is what we call user bias.
For an explicit-ratings model (as discussed above, when we have explicit ratings for user-item pairs), one way to account for user bias is to model the actual user-item ratings asrui∼βu+r^ui,rui∼βu+r^ui,
where βuβu is the user bias of user u and r^uir^ui is the model of whatever is left over; for example, r^ui=xTuyir^ui=xuTyi if we use the matrix factorization model discussed above. We can account for item bias in a similar way:rui∼βu+γi+r^ui;rui∼βu+γi+r^ui;
here, γiγi is the item bias of item i.
Remark. If instead of matrix factorization we used a traditional collaborative filter, we would define r^uir^ui via kk-nearest neighbors using some similarity metric (Pearson is a standard choice), βuβu is the average rating of user u over all items, and γiγi is the average rating of item i over all users.
## Biased ALS
User and item biases can be directly incorporated into the ALS algorithm. We model the user-item ratings matrix asrui∼βu+γi+xTuyirui∼βu+γi+xuTyi
and minimize the cost functionCbiased=∑u,i∈observed ratings(rui−xTuyi)2+λ(∑u(∥xu∥2+β2u)+∑i(∥yi∥2+γ2i)).Cbiased=∑u,i∈observed ratings(rui−xuTyi)2+λ(∑u(‖xu‖2+βu2)+∑i(‖yi‖2+γi2)).
Again, because of the regularization, we can hold the user variables fixed and solve for the minimum in the item variables. Then we can hold the item variables fixed and solve for the minimum in the user variables.
The biases βuβu and γiγi appear in CbiasedCbiased without any coefficients, whereas all the other parameters appear at least once with some coefficient. So one approach would be to solve for the biases separately from the other parameters in each step.
It is easier, though, to leverage the work we’ve already done. We can rewrite our cost function at each step so that it looks like an unbiased model, and then just use the same formulas we found above for the unbiased ALS. The trick is to define new vectors that include the biases as components in the right way.
Let ββ be the vector of user biases (with n_users components) and γγ the vector of item biases (with n_items components). Here is the algorithm:
### ALS with Biases
1. Initialize user vectors randomly and set all biases to zero (or initialize them randomly, it doesn’t matter very much).
2. For each item i, define three new vectors :rβi:=ri−βriβ:=ri−βwith components rβui:=rui−βuruiβ:=rui−βu (notice that both vectors have n_users components),x~Tu:=(1,xTu),x~uT:=(1,xuT),andy~Ti:=(γi,yTi).y~iT:=(γi,yiT).Then Cbiased=∑(rβui−x˜Tuy˜i)2+λ(∑u∥x˜u∥2+∑i∥y˜i∥2)Cbiased=∑(ruiβ−x~uTy~i)2+λ(∑u‖x~u‖2+∑i‖y~i‖2). Hence, we find that the item bias and vector can be computed asy˜i:=(γiyi)=(X˜TX˜+λI)−1X˜Trβi.y~i:=(γiyi)=(X~TX~+λI)−1X~Triβ.(II is now the (N+1)×(N+1)(N+1)×(N+1) identity matrix, and X~X~ and Y~Y~ are matrices whose columns are the vectors x~ux~u and y~iy~i as usual.)
3. Now, for each user u, define three new vectors:rγu:=ru−γ,ruγ:=ru−γ,y˜Ti:=(1,yi),y~iT:=(1,yi),andx˜Tu:=(βu,xu).x~uT:=(βu,xu).The user bias and vector can be computed asx˜u:=(βuxu)=(Y˜TY˜+λI)−1Y˜Trγu.x~u:=(βuxu)=(Y~TY~+λI)−1Y~Truγ.
4. Repeat 2), 3) until convergence.
## Implicit Feedback
For many real-world user-item interactions there are no explicit rating data available. However, there is often nontrivial information about the interactions, e.g. clicks, listens/watches, purchases, etc. Such indirect “ratings” information about user-item interactions is known as implicit feedback. Modeling implicit feedback is a difficult but important problem. There are several ways to use the ALS matrix factorization to approach such a model. We present here a standard solution, presented (without bias corrections) in Hu2008.
The basic approach is to forget about modeling the implicit feedback directly. Rather, we want to understand whether user u has a preference or not for item i using a simple boolean variable which we denote by pui.pui. The number of clicks, listens, views, etc, will be interpreted as our confidence in our model.
Following the fundamental idea of matrix factorization models, we try to find a user vector xuxu for each user u and an item vector yiyi for each item i so thatpui∼xTuyi.pui∼xuTyi.It is important to note that we never actually observe puipui! (This is a very different situation than the explicit feedack models, as discussed above, where ruirui is the observer rating.)
Let’s assume the our implicit feedback is a positive integer (number of clicks, number of views, number of listens, etc). That is,rui=# of times user u interacted with item i.rui=# of times user u interacted with item i.
How do we go about finding the vectors xuxu and yiyi given some implicit feedback {rui}{rui}? If a user has interacted with an item, we have reason to believe that pui=1pui=1. The more they have interacted with that item, the stronger our belief in their preference.
To define our model, setpui={10if rui>0if rui=0.pui={1if rui>00if rui=0.We try to minimize the following cost function:Cimplicit:=∑u,i∈observed interactionscui(pui−xTuyi)2+λ(∑u∥xu∥2+∑i∥yi∥2),Cimplicit:=∑u,i∈observed interactionscui(pui−xuTyi)2+λ(∑u‖xu‖2+∑i‖yi‖2),where cuicui is our confidence in pui.pui. That is, the more a user has interacted with an item, the more we penalize our model for incorrectly predicting pui.pui.
If a user has never interacted with an item, it is possible that pui=1pui=1 and the user has just never encountered the item. It is also possible they are actively avoiding the item. To deal with this ambiguity, it is common to define the confidence bycui:=1+αrui,cui:=1+αrui,where αα is a parameter of the model that needs to be tuned to the dataset. There is some empirical evidence that setting it to the sparsity ratio (the ratio of nonzero entries to zero entries) works well; missing entries are often interpreted as slightly negative, and so one could interpret αα as balancing positive and negative interactions. See Johnson2014, for example. Another possibility that works well (and makes the model more robust against power users — those users who interact with items orders of magnitude more often than the average user), which is also mentioned in Hu2008, is to setcui=1+αlog(1+rui/ϵ),cui=1+αlog(1+rui/ϵ),where ϵϵ is yet another data-dependent parameter of the model.
## ALS for Implicit Feedback
The basic idea of the ALS algorithm for matrix factorization applies to minimizing CimplicitCimplicit: if we hold the user (resp. item) vectors fixed, then CimplicitCimplicit depends quadratically on the item (resp. user) vectors. That means we can do the same thing: hold the user vectors fixed and solve for the minimum in the item variables, then hold the item vectors fixed and solve for the minimum in the user variables, and repeat…
Of course, our cost function CimplicitCimplicit is slightly different, so the actual steps involving solving for the minimum look a bit different. The algorithm is as follows.
### Implicit ALS
1. Initialize user vectors.
2. For each item i, let pipi be the vector whose components are puipui (for fixed i, there will be n_users components), let CiCi be the diagonal matrix with cuicui for fixed uu along the diagonal, and let di=Cipidi=Cipi (the reason for defining didi separately will be explained in the remarks about the numpy implementation below). Computeyi=(XTCiX+λI)−1XTdi.yi=(XTCiX+λI)−1XTdi.
3. For each user u, let pupu be the vector whose components are puipui (for fixed u; there will be n_items components), let cucu be the vector whose components are cuicui, let CuCu be the diagonal matrix with cucu along the diagonal, and let du=Cupudu=Cupu. Computexu=(YTCuY+λI)−1YTdu.xu=(YTCuY+λI)−1YTdu.
4. Repeat 2), 3) until convergence.
Remarks
1. As for standard (explicit) matrix factorization models, it is (almost) always better to solve (XTCiX+λI)yi=XTdi(XTCiX+λI)yi=XTdi than to invert the matrix (XTCiX+λI)(XTCiX+λI).
2. Since cui=1+αruicui=1+αrui, which we can write in terms of matrices C:=(cui)C:=(cui) and R:=(rui)R:=(rui) as C=1+αRC=1+αR, the computation in step two can be rewritten asyi=(XTX+λI+αXTRiX)−1XTdi.yi=(XTX+λI+αXTRiX)−1XTdi.The term XTX+λIXTX+λI is independent of i, and can be computed once and reused at each step of the algorithm (similarly for YTY+λIYTY+λI in step 3).
## A Python numpy Implementation of ALS for Implicit Feedback
It turns out that the matrix multiplication XTCiXXTCiX and the matrix-vector product XTdiXTdi are both easier to implement in numpy than to express in standard linear algebra notation. A direct implementation of the algorithm is of course possible, but a small bit of thought improves performance vastly.
#### numpy Implementation Notes
A direct implementation of the matrix product XTCiXXTCiX would be something like
Ci = np.diag(c[i])
XTCiX = np.dot(X, np.dot(Ci, np.dot(X.T)).
But the matrix product np.dot(X, Ci) is just multiplying the rows of XX, in order, by the diagonal elements of CiCi, which is achieved very efficiently by simple numpy broadcasting. So we can achieve the same matrix product via
XTCiX = np.dot(c[i] * X.T, X).
Moreover, since di=pi+αridi=pi+αri (which follows from puirui=ruipuirui=rui), we can rewrite the algorithm in terms of just the scaled raw counts αRαR and the preference pp asyi=(XTX+λI+αXTRiX)−1XT(pi+αri).yi=(XTX+λI+αXTRiX)−1XT(pi+αri).
Hence, we can completely avoid constructing the diagonal matrices CiCi and CuCu.
Finally, when n_users and n_items are large, RR (and hence pp) will generally be sparse matrices. The matrix (XTX+λI+αXTRiX)(XTX+λI+αXTRiX) is, however, N×NN×N and since the number of factors is generally small (on the order of 10), there is no great savings by using a sparse implementation of this matrix. On the other hand, only the user vectors corresponding to nonzero entries of riri (and pipi) are needed in the computation of XTRiXXTRiX and of XT(pi+αri)XT(pi+αri), so if the algorithm is parallelized, it is very useful to only ship those vectors to the workers doing the computation for yiyi (this is, for example, how the Spark implementation works). Our implementation is not parallelized (for the sake of clarity), so we don’t need to worry about shipping data to workers.
## ALS with Biases for Implicit Feedback
As with the standard matrix factorization model, matrix factorization models for implicit feedback tend to work better if user and item biases are accounted for; we introduce parameters βuβu and γiγi as before, and try to fit a modelpui∼βu+γi+p^ui,pui∼βu+γi+p^ui,where p^ui=xTuyip^ui=xuTyi as above, by minimizing the cost functionCbiasedimplicit:=∑u,i∈observed interactionscui(pui−βu−γi−xTuyi)2+λ(∑u(∥xu∥2+β2u)+∑i(∥yi∥2+γ2i)).Cimplicitbiased:=∑u,i∈observed interactionscui(pui−βu−γi−xuTyi)2+λ(∑u(‖xu‖2+βu2)+∑i(‖yi‖2+γi2)).
The interpretation of the biases in this case is slightly different:
• User Bias βuβu: A higher bias βuβu pushes the values of all preferences puipui up for all items; that is, a user with a high bias likes a large variety of items; conversely, a low user bias means the user only likes a small selection of items.
• Item Bias γiγi: A higher item bias γiγi pushes the preferences puipui up for all users; that is, the item is more universally beloved (or mainstream); conversely, a low item bias might indicate a niche item.
Again, the principle of the ALS algorithm applies with appropriate modifications for the new cost function CbiasedimplicitCimplicitbiased. The algorithm is:
### Implict ALS with Biases
1. Initialize user vectors and biases.
2. Define vectorspβi:=pi−β,piβ:=pi−β,x~Tu=(1,xTu),x~uT=(1,xuT),andy~Ti=(γi,yTi).y~iT=(γi,yiT).Then computey~i=(X˜TCiX˜+λI)−1X˜Tdβi,y~i=(X~TCiX~+λI)−1X~Tdiβ,where we have defined dβi=Cipβidiβ=Cipiβ as in the previous implicit ALS algorithm.
3. Define vectorspγu:=pu−γ,puγ:=pu−γ,y~Ti=(1,yTi),y~iT=(1,yiT),andx~Tu=(βu,xTu).x~uT=(βu,xuT).Then computex˜u=(Y˜TCuY˜+λI)−1Y˜Tdγu,x~u=(Y~TCuY~+λI)−1Y~Tduγ,where dγu=Cupγuduγ=Cupuγ.
4. Repeat 2) and 3)
The same remarks apply as for biased ALS and implicit ALS.
##### Amir Masoud Sefidian
Data Scientist, Researcher, Software Developer
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# nLab Élie Cartan
Related Lab entries
Élie Joseph Cartan was a French differential geometer. His results include the classification of complex semisimple Lie algebras (“Cartan classification”), extension of these results to a class of symmetric spaces, the proof of the Lie–Cartan theorem (after Serre sometimes called “Lie's third theorem”) on integration of Lie algebras to Lie groups (Lie proved just the integration to local Lie groups), the method of moving frames, the introduction of Cartan’s connection, numerous results in Riemannian geometry, results related to the formal integrability of PDEs (Cartan involutive equations, Pfaffian system), etc.
Father of Henri Cartan.
category: people
Last revised on October 30, 2020 at 08:22:55. See the history of this page for a list of all contributions to it.
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# Brackets in Boolean ALgebra Distributive Law
What is the purpose of the brackets in all the examples I've seen of the distributive law? Why are there no brackets when distributing an AND term and there are when distributing an OR term? Could I write:
X * (Y + Z) = (X * Y) + (X * Z)?
eg of law. X * (Y + Z) = X * Y + X * Z
X + (Y * Z) = (X + Y) * (X + Z)
Note: I'm very new to boolean algebra
The order of operations is * then +. So $X * Y + X * Z$ means $(X * Y) + (X * Z)$ but $X + Y * X + Z$ means $X + (Y * X) + Z$. That is why the parentheses are necessary in these statements of the laws: $$X * (Y + Z) = X * Y + X * Z$$ $$X + Y * Z = (X + Y) * (X + Z)$$ Sometimes we put in extra parentheses to emphasize the order of operations, as in $$X * (Y + Z) = (X * Y) + (X * Z)$$ $$X + (Y * Z) = (X + Y) * (X + Z)$$
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# Very Long Distance Ethernet connection for Internet and other data (2000 feet)
I am building a house. It's located about 2000 feet away from the nearest Internet cable. I had to run our electrical service underground the whole way, and have already installed a conduit for internet/phone cables from end to end with pull points every 1000 feet.
My question is: what's a cost-effective way to establish a reliable, high-speed Ethernet connection at this distance? It will be used to provide Internet service as well as video/audio feeds and control signals. I think 100 Mbps each direction would be satisfactory as a target max speed for the connection.
We will have electrical power available at both ends of the connection.
I have looked into Ethernet extenders, but the max speed seems to drop drastically as the distance increases.
I would love to use fiber, but I can't find an inexpensive termination method.
I don't think wireless is practical, because we don't have line-of-sight between the endpoints due to a large area of trees.
A satellite or 4G connection is not suitable due to price, speed, and reliability, plus the need for audio/video/control signals across the distance.
Thanks for any guidance!
UPDATE 2016:
I installed RG6 gel-filled direct-bury coax cable (in PVC conduit for added protection) and used Ethernet-to-coax extenders (TrendNet TPA-311) and am VERY pleased with the results. At a cost of $50 or less per device, it's very reasonable cost. Also, RG6 coax, if you shop around, is very cheap. I am able to achieve 60Mbit Internet speed (which is my ISP's max offering in my area) and these devices are very stable - no crashes or need to reboot them. I even installed a T to split the line halfway in order to connect another building to the network. One very important note: Be sure to install high quality grounded surge protection at EACH termination point. I used these. I tried the system without surge protection, and within a week my TPA-311 devices were destroyed. I disassembled them to diagnose the problem and found several components vaporized due to a high energy event. Lesson learned. Since installing surge protection, we've had several large lightning storms and we're still working rock solid. Other installation notes: • Get a cheap coax crimper and bulk coax terminators. They are very easy to install. No need for any expensive tools. • For long pulls, a cable lubricant is absolutely essential. Our first pull of about 800 feet was without lubricant, and I began to doubt we would ever make it. Subsequent pulls (even longer distances) with lubricant were easy. Update after 1.5 years - still working perfectly! Have not needed to replace any components (except a battery in my UPS). Very pleased with this solution! • Define inexpensive and please do tell us at what did you look exactly? Fiber is the only real way that I see. Also, modern Ethernet connections are full-duplex, so you get same speed both ways. There are media converters for gigabit fiber, for example TP-Link MC210CS that are in the$50-60 range. – AndrejaKo Feb 19 '15 at 16:45
• I will second the vote for fiber. Termination is usually handled by a telecom company that has the equipment (you wouldn't buy it for one time use). Once terminated you shouldn't have to deal with it again. Choose your termination form factor such as ST or SC and use a media converter to convert to copper gigabit Ethernet. – Tinkerer Feb 19 '15 at 23:21
• Since the run is entirely on my property past the d-mark, the telco would not touch it. Thus I have to do everything myself. Thus an inexpensive termination (sub $20 USD per termination) would be the goal. – Ryan Griggs Feb 20 '15 at 16:46 • I think the coax solution proposed below by @bigjosh is the most reasonable, due to the cost of coax cable, the ease of termination, and reasonable price of extender hardware. Would love to have fiber, but due to the high cost of connector termination installation (i.e. cleaving tool, etc) I think it's not practical for me :( – Ryan Griggs Feb 20 '15 at 16:48 • Belden's FX Brilliance tool-less terminators might work, but could I cut/polish the fiber with common household tools? (belden.com/docs/upload/…) – Ryan Griggs Feb 20 '15 at 16:54 ## 4 Answers You want an Ethernet over coax extender like this one... https://www.amazon.com/StarTech-com-Gigabit-Ethernet-Unmanaged-Extender/dp/B00AMCKN80/ref=as_sl_pc_ss_til?tag=joshcom-20&linkCode=w01&linkId=B6C47PTXNGHWHVUT&creativeASIN=B00AMCKN80 It should easily be able get you to 100Mbps @ 2000ft (~600 meters) using any supported coax cable... • Thanks for the info. However the problem with that type is that as the distance increases, the speed decreases. Per their spec, at 300m the max speed is 75Mbit/s, and 1km it drops to 10Mbit/s. – Ryan Griggs Feb 19 '15 at 16:48 • I did find this one, which may offer higher speeds: ethernetextender.com/ethernet-extension-products/… – Ryan Griggs Feb 19 '15 at 16:51 • The speed depends on range and cable quality. If you have room in the conduit, you should be able to get 112Mbps @ 2000 feet over RG-11 cable. The length/speed/distance chart for the coax model is available at sgcdn.startech.com/005329/media/sets/EOC1110x_Manual/…. – bigjosh Feb 19 '15 at 16:59 • I like the idea of the coax-based solution. 1) coax is cheap! 2) I can fit multiple RG6 cables in my 1/2" conduit 3) 144Mbps at ~600m with RG6 looks well within spec. 4) the extender hardware seems reasonably priced. THANKS! – Ryan Griggs Feb 19 '15 at 17:36 100Base-FX seems to be right with 2km as its max theoretic distance, and there appear to be converters available at reasonable prices. Or is the termination problem one of attaching the connectors to the end of the fiber? I would have thought it was possible to just order one of the correct length. • Yes the termination (attaching the connectors) is the problem. Trying to pull the cable through the conduit with ends attached would probably damage it. May not even fit, due to size of conduit. – Ryan Griggs Feb 19 '15 at 16:52 • @Ryan Griggs Do research connector types. There's a whole science about that and what's compatible with what, but there are any connectors that have exterior protection for the fiber core and that are same size or smaller than regular 8P8C connector. For example DIN optical connector is very small and then you can get an adapter from that to whatever you want to use in the end. – AndrejaKo Feb 19 '15 at 16:57 • I see termination kits for <$100 on Ali, but don't know how well they work. – Spehro Pefhany Feb 19 '15 at 20:39
• You can buy pre-terminated fiber lengths that are designed to be pulled through ducts. On the ones I bought there was a short section of hoze that covered the connectors. On one end of the hose was a pulling eye, on the other end was an adaptor peice that screwed to the gland on the cable. This gland was in turn bonded to the kevlar reinforcements in the cable. – Peter Green Oct 27 '15 at 11:57
Don't know if this is a practical approach, but maybe you could use power over ethernet repeaters.
One unit typically extends the range by 100m, I've seen one advertised to be chainable six times, so you would get 600m, which is quite close to the 2000ft (it was the ALLNET ALL048600, sorry I only found a German description). Maybe you could provide power from both sides, to easily bridge that distance.
This would also allow gigabit ethernet.
But you would have to buy 6 repeaters - and install them somehow along the line. Doesn't sound like the most reliable solution.
• I can't chain due to no breaks in the conduit. I only have two pull points, each at about 1000 feet. Otherwise, the conduit is buried about 2.5 feet deep. But thanks for the info! – Ryan Griggs Feb 19 '15 at 17:38
• Oh dear, I read something along the line of every 100 feet (missed a zero there) a pull point... never mind my answer then. – Arsenal Feb 19 '15 at 21:12
As long as you have power at the remote end and an approximation of line of sight, Wifi and a yagi at each end would be a fraction of the cost of a cabling run.
• As stated, no line of sight due to heavily wooded area. – Ryan Griggs Feb 20 '15 at 16:44
• @RyanGriggs Maybe you can wireless hop for part of the distance, from home to the trees or the trees to the cable? – markt Feb 20 '15 at 20:44
• Everything is underground, don't want antennas in the middle of the field. Also would have to run at least 75% of the run to get around the trees. Thanks – Ryan Griggs Feb 20 '15 at 22:36
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Lecture 13: Lecture notes
Population Dynamics – Part 2
• Populations with age structure
• Managing natural populations
• Life histories
• Spatial Structure
Remember….. Nt = λtN0
1. This Tells Us Nothing About the Age Distribution of Individuals in the Population
• Why does that matter?
• Most populations that we’re interested in managing have age structure that’s critical to their ecology and their population growth rate
• Age-Specific Fecundities and Age-Specific Mortalities (and age specific rates of movement)
2. Age Structure of Human Populations
• Constant: relatively constant proportion of young to old people. Birth rate is relatively constant.
• Growing: large proportion of young people, high birth rate.
• Shrinking: Population consists of a small proportion of young people, indicating low birth rates.
3.Age-specific rates
• lx survivorship function
• Probability that a newborn individual will survive to age x
• By convention, l1 = 1
• mx (or bx) maternity (birth) function
• Number of female offspring born to a female of age x (between x – ½ and x + ½)
• Sx survival rate
• Proportion of individuals of age x surviving to age x+1 (so l2 = l1 s1)
• Inverse is annual mortality rate
4. Age Structure is Critical to Many Ecological Processes Including Those Vital Rates That Determine Population Change
• RO= Net reproductive rate of a single individual in her lifetime.
• RO= The number of daughters born per female in her lifetime
• RO= l1m1+l2m2+l3m3+…lxmx
• RO= $\sum_{1}^{x} l(x)m(x)$
How can we convert this into a reproductive rate per year?
5. Mean Generation Time: A female’s age when she has her median daughter
T(gen)= $\frac{\sum xl_{x}m_{x}}{\sum l_{x}m_{x}}$
6. Managing Populations For Stable Age Structure
• When age structure is stable, the proportion of individuals in each age class remains constant over time, even as population size varies
• Stable age structure develops when populations grow under constant environmental conditions
7. Constant Environmental Conditions?
• Environmental conditions vary all the time!
• Ecologically, we can consider the environment to be constant if age-specific fecundities and mortalities remain unchanged
• So, constant age-specific fecundities and mortalities promote stable age structure
• We can manipulate (manage) these in an attempt to generate the stable age structure that we want – this is the basic purpose of hunting & fishing licenses
8. Stable age distribution
• Will be reached regardless of what the starting age distribution was
• And will be the same – hence a property of the sx (or lx) and bx terms
• You’ll know it because:
• l will be constant
• Age distribution will be constant
• If the population starts far from the stable age distribution, it will take longer to ‘settle down” on the SAD
9. Managing Bunnies
• First, the population is still growing exponentially
• If natural factors are too slow to operate we may have to impose our own density-dependent mortality
• In other words, we should increase the number or decrease the price of hunting licenses as bunny density goes up
• To get the age structure that we want, we might actually have to feed young bunnies to increase the proportion that survive to age 2…
• …and then shoot them
10. Problem
• How can we calculate the number of licenses we need, the number of young bunnies to feed, and what aged bunnies it’s really best to shoot?
• We could do our demography calculations over and over again, using different age specific mortalities, but that’s a real chore for many organisms
11. Matrix Algebra
• We can use some of the features of matrix algebra to simplify the running of demographic model
• A Leslie Matrix is just a “box” that contains age-specific fecundities and mortalities
• By manipulating a Leslie Matrix and its associated population vector, we can make predictions about populations
12. Assessing and Predicting Population Dynamics
• Whether we’re managing resource populations (fish, timber, deer, etc), protecting endangered species, or studying exotic invasives, we need methods to assess their population dynamics
• You’ve met some simple population models and explored the wonders of the Leslie Matrix
• Population viability analysis is an application of the Leslie matrix for managing rare populations
13. Population Viability Analysis
• A process of identifying the threats faced by a species and evaluating the likelihood that it will persist for a given time into the future
• Oriented towards the conservation and management of rare and threatened species, with the goal of applying the principles of population ecology to improve their chances of survival
14. The Risks of Rarity
• Human actions may cause a species to become rare, but may not directly cause the last individual to perish
• Indeed, we often make a concerted effort to rescue rare species, with uncertain success
• Rare species have a measurable probability of extinction (p[E]) due to deterministic and stochastic factors
• demographic factors result in λ < 1 and will result in extinction
• stochastic factors may lead to extinction even when λ > 1
15. Deterministic Extinction
• When λ < 1, the population declines each year.
• λ < 1 simply means birth rates are less than death rates.
• An example would be poaching mortality in excess of natural reproduction.
• Due to vehicle-caused mortality, the Florida panther has λ =~0.9. Time to extinction is ~ 30 years
16. Stochastic Extinction
• Stochastic = chance variation. A rare population with λ > 1 may go extinct due to chance variation processes.
• These include:
• demographic stochasticity: chance variation in sex ratio of offspring
• environmental stochasticity: chance variation in weather and food supply
• catastrophes: extreme, rare (1- 5 per century environmental events
• genetic stochasticity, including drift and in-breeding
17. PVA Approach
• Population viability analysis is a probabilistic approach to assessing p(E) when λ > 1 but a population faces multiple threats and random (stochastic) variation, it might go extinct
• PVA provides a means to evaluate multiple, varying, interacting factors of that might result in the “extinction vortex”
• PVA takes into account
• demographic risks
• environmental variability
• genetic risks (Ne-dependent) of drift and inbreeding
• episodic catastrophes
• PVA models require age-specific demographic data
18. The Extinction Vortex – small population size causes increased inbreeding and genetic drift, which causes decreased reproduction and survival, which causes reduced population growth rate, which causes smaller population size… and continues spiraling inward.
19. PVA Can Be Used For:
• Planning research and data collection. PVA may reveal that population viability is insensitive to particular parameters. Research may be guided by targeting factors that may have an important impact on extinction probabilities or on the rank order of management options
• Assessing vulnerability. Together with cultural priorities, economic imperatives and taxonomic uniqueness, PVA may be used to set policy and priorities for allocating scarce conservation resources
• Ranking management options. PVA may be used to predict the likely response of species to reintroduction, captive breeding, prescribed burning, weed control, habitat rehabilitation, or different designs for nature reserves or corridor networks
The Distribution and Spatial Structure of Populations
• Spatial patterns
• Dispersal
• Metapopulations
1. Some Key Terms and Concepts
• A population consists of the individuals of a species within some area
• Because the natural environment usually is a mosaic of suitable habitat, species populations often are made up of sub-populations
• The distribution or geographic range of a species is the total geographic area occupied
• Population size is the number of individuals in the total population or a sub-population
• A population thus exhibits spatial structure in the number and spacing of its sub-populations
• The size and spatial distribution of sub-populations (and thus the total population) vary over time
2. Habitat and Niche
• Fundamental niche describes the range of environmental (temperature, moisture, pH, nutrients, vegetation types..) conditions in which an organism is physiologically able to persist
• Realized niche is where the organism is actually found, and is a subset of the fundamental niche determined by predators, competitors, pathogens etc.
• We often equate realized niche with habitat – a description of environmental conditions where a species occurs
3. Ecological niche modeling
• Uses habitat or climatic features
• Predict future range under a changing climate
• May be larger, smaller, different locations
• Predict the eventual distribution of an invading species
4. Modeling fish distributions in Belize
• Species distribution model
• African tilapias: a pan-tropical invader
• Tilapia occurrence data
• Habitat vulnerability
• 7,510 km of river habitat vulnerable (24%) of total
• 0 to 277 meters above sea level
• 1 566 km2 mean watershed area
• 0 to 446 km from sea
• 1 Most important variables: watershed area, elevation
5. Migratory species
• Occupy large ranges
• Depend on existence of spatially distant habitat AND a secure migratory pathway
6. Dispersal integrates sub-populations
• By chance, weather, etc
• From high-density to low-density patches in response to crowding
• From natal patches to find territories, eventual mating opportunities
7. Models of spatial structure
• Metapopulations: patches are of similar quality but vary in size and distance. Intervening habitat is unsuitable.
• Source-sink dynamics: Patches vary in quality, so that b > d in some, b < d in others. Reproductive success in high-quality patches and subsequent dispersal are critical to maintaining population
• (and between-year variation in reproductive success in poor-quality patches may account for occasional outbreaks)
8. Conservation implications of spatial structure
• Maintaining patch connectivity, either by direct corridors or by ensuring that habitat matrix is suitable for dispersing individuals
• Once connectivity is lost, sub-populations are subject to the “risks of rarity”, and probabilistically will “wink out’, one by one
• Dispersal underlies the “rescue effect”, in which a local population temporally is lost but then restored by re-colonization
9. Desert bighorn sheep in California. Larger populations persist longer than smaller populations. All populations less than 50 individuals went extinct within 50 years.
10. Metapopulations
• Change in perspective
• Population size vs. population persistence
• Equilibrium manifested regionally
• Number of populations filling landscape
11. The basic metapopulation model
• p = fraction of occupied patches
• 1-p = fraction unoccupied
• e = probability of an occupied patch going extinct
• Rate of colonization of empty patches depends on occupied patches, empty patches, and colonization rate c
• dp/dt = cp(1-p) - ep
• peqm = 1 – e/c
• In reality, patches vary in size, quality and degree of isolation
12. Implications of Population Structure
• Species formation
• Isolates are more likely to develop into species
• Genetic variation and interchange
• Sub-populations may be subject to differing selection pressures
• Population viability
• Some sub-populations may survive various threats and thus be able to “rescue” lost sub-populations
• The management of populations and habitat are linked
• There are scientific reasons to protect multiple sub-populations (insurance, rescue)
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Their path is not so straightforward. These beta particles are generally in the form of electrons or positrons (which are electrons with a positive electric charge). In Beta decay, a high-energy electron (called a beta particle) is emitted from a neutron in the nucleus of a radioactive atom. Clearly, the reaction appears to conserve charge, but if we start with a neutral Cs atom (55 electrons), the resultant Ba atom is now a positive ion (56 p+, 55 e-). What are the Alpha and Beta Particles? In beta decay. This mechanism is explained in the framework of quantum mechanics. Note that,the Standard Model counts six flavours of quarks and six flavours of leptons. A large amount of radiation of beta particles may cause skin burn and erosion. What is the Charge on the Beta Particle? The beta decay is generally of two types. Let’s give some examples of these other types of radioactive decay. Beta-Minus Decay: In beta minus, a neutron is transformed to yield a proton causing an increase in the atomic number of the atom. consider!the!simplest!formof!βdecaytoillustratethedifficulties.Theprotonandthe! Positrons are emitted with the same kind of energy spectrum as electrons in negative beta decay because of the emission of … 1. Vedantu academic counsellor will be calling you shortly for your Online Counselling session. Pro Lite, Vedantu It still lacks the strength to beat gamma rays. Due to the loss of a proton during beta plus decay, it changes to one element from another. A beta particle is emitted from the nucleus of an atom during radioactive decay. Pro Lite, Vedantu Three primary ways to differentiate this phenomenon are proton decay, neutron decay, and electron decay. Beta particles, high energy electrons, are emitted when a neutron decays to form a proton and an electron. Due to the loss of a proton during beta plus decay. The emission of a positron or an electron is referred to as beta decay. The beta particles emitted are in the form of ionizing radiation, also called beta rays or beta emission. So in beta decay, an electron is ejected from the nucleus. Positron and neutrino travel from the nucleus which has less proton than before. Let's do beta decay. Beta Particles: β can be positrons or high speed electrons. Beta particles are energetic electrons, they are relatively light and carry a single negative charge. Both of these have less mass and are neutral particles. These emissions are named as radiation. The beta decay occurs via the weak interaction. Beta particles are electrons or positrons (electrons with positive electric charge, or antielectrons). It is at this elementary level that weak interaction steps in. These particles can achieve relativistic speed, which is compared to the speed of light. Cobalt-60 is a nuclide that β− decays in the following manner: 60Co → 60Ni + β−+ neutrino. Radioactive materials produced cosmic rays continuously into the atmosphere. In this decay, a neutron is converted to yield a proton, making an increment in the atomic number of the atom. Beta emitters are harmful to our bodies. A beta particle (β-particle) is an electron or positron having very high speed and energy and is emitted during radioactive decay of nucleus during beta decay process. The nucleus will lose an electron or positron when a nucleus emits a beta particle. Antineutrino is the antimatter. The rate of radioactive element decays can be expressed as a half-life, which means the total time required for one-half the given quantity of isotope. In most practically interesting cases, single beta decay is energetically forbidden for such nuclei, because when β and ββ decays are both allowed, the … The W– boson then decays into abeta particle and anantineutrino. Radioactive beta decay can be defined as the property of several elements available naturally along with isotopes produced artificial isotopes of the elements. The beta particle, which may be either negatively charged (negatrons) or positively charged (positrons), originates from the nucleus of an atom. It is necessary to memorize the whole phenomenon to understand nuclear calculations with this Greek letter without any further notation. A beta particle that is positively charged is called a positron. During beta decay one of two down quarks changes into an up quark by emitting a W– boson (carries away a negative charge). 2. This process is a weak interaction decay process. The positron is accompanied by a neutrino, an almost massless and chargeless particle. Beta particles with energy of 0.5 MeV have a range of about one metre in air. If a beta source enters the body, it causes tissue damage and can increase the risk of cancer.Figure 2 shows the relative levels of penetration of a variety of different radiation types. Similarly, if a neutron is converted to a proton, it is known as β- decay. 4. the numbers at the top and bottom give the same totals on both sides Polonium nuclei have 84 protons, so their nuclear charge is +84. Ans: Ionizing radiation is categorized into three groups, such as alpha particles, beta particles, and gamma-ray. We can take an example as, after the ongoing beta-minus decay, an atom of carbon, which possesses 6 protons, will become an atom of nitrogen with 7 protons. Exposure to beta ra… (Note this isn't the comlete equation – see page 16.) As can be seen from the figure, the weak interaction changes one flavor of quark into another. Potassium-40 is a beta emitter. In general, the up quark reabsorb immediately the negative charge and returns to the down quark state. Beta decay (β) and electronic capture change the composition of protons and neutrons in a nucleus, the electric charge of the nucleus increasing or decreasing by one. As another characteristic signature of these transformations, other particles that cannot be detected are emited: neutrinos or antineutrinos. In this type of decay, a neutron which is present inside the atom’s nucleus converts into a proton in beta minus decay. The beta particle has the same mass and charge as an electron. There are three major types of radioactive decay: alpha decay, beta decay and gamma decay. The conservation of electric charge is required in this reaction. Beta decay is governed by the weak interaction. The first discovered was “ordinary” beta decay and is called β− decay or electron emission. If a neutral neutron which transforms into proton electrically, another electrically negative particle will be produced. These particles carry either a single positive (positron) or negative (electron) charge. One is beta minus (β-), and the other one is beta plus (β+). The beta plus decay conservation law also earns a positron and neutrino. The beta particles follow a very zig-zag paththrough absorbing material. beta decay. Beta decay is the loss of an electron from the nucleus of an atom. Ans: There are two types of beta decay, such as beta plus and beta minus/. We saw in the previous video that you represent an electron, since it has a negative one charge, you put a negative one down here, it's not a proton, nor is it a neutron, so we put a zero here. One of protons or neutrons can be transformed into a different form. Also, conservation of charge takes place. It is possible because they have a small mass and can release high energy. Rather than the alpha particles, beta particles are much less ionized. Pro Lite, CBSE Previous Year Question Paper for Class 10, CBSE Previous Year Question Paper for Class 12. It’s the result of a type of decay on radioactive materials. The three processes are electron emission, positron (positive electron) emission, and electron capture. Radioactivity comes under a dangerous phenomenon but is quite useful. The symbol β− represents an electron emitted in nuclear beta decay. The decay of 14C and 14N is the best example of beta minus decay. β-decay is accompanied by the emission of an antineutrino, β + decay is accompanied by the emission of a neutrino. Thus the set of all nuclides with the same A can be introduced; these isobaric nuclides may turn into each other via beta decay. Though an atom summons a proton at the time of beta-minus decay, it alters from one element to another. Note that,the Standard Model counts six flavours of quarks and six flavours of leptons. This process is equivalent to the process, in which a neutrino interacts with a neutron. Also, conservation of charge takes place. The neutrinois a particle emitted in beta decay that was unanticipated and is of fundamental importance. That neutron may be thought of as a combination of a beta particle (negative charge) with a proton (positive charge). It undergoes the beta decay: 9091Th234 → 91Pa234 + -1e0 (electron or the β-particle) Here, one electron is released. The existence of this fugitive intermediate, whose properties had been predicted by theory in the late 1960s, has been confirmed experimentally in 1983. Key characteristics of beta radiation are summarized in following points: 1. The mass of a beta particle is around 1/2000th of a proton. Beta minus decay. The range of penetration of beta particles is greater than the alpha particles. A down quark in a neutron, whose electric charge is -e/3, frequently emits a negative charge -e. Its charge is now +2e/3. It has become an up quark. This process is equivalent to the process, in which a neutrino interacts with a neutron. 3. The antineutrino has no rest mass nor electric charge and does not interact readily with matter. They are a type of ionizing radiations. 2. In positron emission, also called positive beta decay (β +-decay), a proton in the parent nucleus decays into a neutron that remains in the daughter nucleus, and the nucleus emits a neutrino and a positron, which is a positive particle like an ordinary electron in mass but… Read More; radioactivity classifications Ans: Beta particles possess a charge of -1. During beta-plus decay, a proton in an atom's nucleus turns into a neutron, a positron and a neutrino. Electron and the positron are generated to obey the law of conservation of charge. For example, after undergoing beta-minus decay, an atom of carbon (with 6 protons) becomes an atom of nitrogen (with 7 protons). These materials keep our planet warm. The atomic number is continuously changing in every single decay so that some different elements, such as parent atoms and daughter atoms, are formed. The electron and antineutron travel from the nucleus, which now has more than one proton before it started. This third interaction is considered weak because beta decays that are the most visible manifestation are very slow transformations that happen rarely. Usually, the beta emission is denoted by the Greek letter. It is the counterpart of neutrinos. Protons can be charged straight to form neutrons and vice-versa by using these three methods. During beta decay, the proton in the nucleus is transformed into a neutron and vice versa. The first theory of beta decay was made in 1934 by the great Italian physicist Enrico Fermi, at a time when the existence of quarks was not suspected and the one of neutrinos only hypothetical. ZAX → Z - 1AY + e$^{+}$ + vN = p + e$^{+}$ + v. Beta-decay or β decay represents the disintegration of a nucleus to become a daughter through beta particle emission. They lose energy through rapid interaction with matter, so they are lighter in mass. This variation of charge is compensated by the emission of a charged particle - an electron or a positron - or, more rarely, by the capture of an electron. The beta plus decay conservation law also earns a positron and neutrino. Beta plus decay: Beta plus decay happens when a proton changes into a neutron, giving out a positron. Here, the mass of the daughter nucleus remains constant, and a different element is formed. 1. Their mass is equal to the mass of the orbital electrons with which they are interacting and unlike the alpha particle a much larger fraction of its kinetic energy can be lost in a single interaction. Beta Decay. In the case of beta-minus decay mechanism is as follows. Beta decay, any of three processes of radioactive disintegration by which some unstable atomic nuclei spontaneously dissipate excess energy and undergo a change of one unit of positive charge without any change in mass number. The negative charge briefly emitted and immediately reabsorbed is carried by an unstable particle called the W-minus boson. Since the 1970s, we know that when a nucleon changes its nature (proton or neutron), it is because one of the constituents (up or down quark) transformes itself from one species into another. Systems of Particles and Rotational Motion, Vedantu The section on beta emission on the previous page (radioactive decay and nuclear equations) focussed predominantly on beta-minus emission. The lifetimes of unstable nuclei are extremely variable (quarter of an hour for a free neutron, one week for iodine-131, thirty years for cesium-137, a billion years for potassium-40), but all these periods, including the quarter of an hour of the neutron, are very long for the nuclear clocks. The beta plus decay conservation law also earns a positron and neutrino. They move through air or other materials, and their path becomes desultory. A very small minority of free neutron decays (about four per million) are so-called "two-body decays", in which the proton, electron and antineutrino are produced, but the electron fails to gain the 13.6 eV energy necessary to escape the proton, and therefore simply remains bound to it, as a neutral hydrogen atom. In this type of beta decay, in essence all of the neutron decay energy is carried off by the antineutrino. What are the Properties of Beta Particles? Also, conservation of charge takes place. Beta decay or β decay represents the disintegration of a parent nucleus to a daughter through the emission of the beta particle. In beta minus decay, the change in atomic configuration is; ZAX → Z + 1AY + e$^{-}$ + v$^{-}$N = p + e$^{-}$ + v$^{-}$. It differs from the electron in its origin. To make a balance in the conservation of charge, the nucleus produces an electron and an antineutrino in this process. There are two types of beta decay, namely, beta minus (β-) and beta plus (β+). During beta decay one of two down quarks changes into an up quark by emitting a W– boson (carries away a negative charge). The mass number of daughter nucleus = 234 - 0 = 234 remained the same and the atomic number (Z) or the charge number = 90 + 1 = 91, got incremented by 1. This electron-neutrino W decay mode, the most economical in energy occurs in the phenomena of radioactivity. And the only difference in writing alpha decay reactions and beta, positron, or gamma, is knowing the Mass and Charge of each of these particles or radiation. Beta decay (β) and electronic capture change the composition of protons and neutrons in a nucleus, the electric charge of the nucleus increasing or decreasing by one. Related topic : α decay : tunnel effect There are actually three types of beta decay. One example is 40 K, which undergoes all three types of beta decay (beta minus, beta plus and electron capture) with half life of 1.277×10 9 years. Beta particles are generally electrons, which move very quickly with a lot of energy. As can be seen from the figure, the weak interaction changes one flavor of quark into another. If the boson decays in the extraordinarily short time elapsing between its emission and its reabsorption, a beta-minus decay occurred. Sorry!, This page is not available for now to bookmark. The we… Ans: A beta particle that is negatively charged is equivalent to an electron. Since an atom gains a proton during beta-minus decay, it changes from one element to another. They range from tens of centimeters in the air, which is energy-dependent; however, in the case of materials, it is a few. Here, a proton turns into a neutron; a positron and a neutrino inside an atom’s nucleus. Though they move through air or other materials, their path becomes desultory. Radioactive atoms possess a certain amount of energy and produce electromagnetic waves spontaneously. They do less damage to a given quantity of energy deposition generally. 2 alpha!decay,!angular!momentumplays!a!crucial!role!in!understanding!the!process.!Let!us! The mass of the beta particle is half of one-thousandth of the mass of a proton. . Nuclear reactors and particle accelerators utilize nuclear materials to produce radioactive material. Mass-Charge balance is your key to learning how to write decay reactions. If an electron is involved, the number of neutrons in the nucleus decreases by one and the number of protons increases by one. A beta decay process consists of carbon-14. Alpha particles are not as dangerous as compared to others when it comes to external exposure. It is the phenomenon that opened a door into the world of sub atoms and influenced the beginning of the nuclear revolution. This resulting path of particle is longer t… When studying nuclear reactions in general, there is typically little information or concern about the chemical state of the radioactive isotopes, because because the … The neutrino was not even proposed in theory until more than 20 years after beta decay was known to involv… The maximal energy of the beta decay electron (in the process wherein the neutrino receives a vanishingly small amount of kinetic energy) has been measured at 0.782 ±.013 MeV. Beta (\ (\beta^-\)) decay is the release of an electron by the change of a neutron to a proton. Beta radiation is slightly more penetrating than alpha radiation, but still not nearly as penetrating as gamma radiation. Here, a neutron is neutral, but the proton possesses a positive charge.
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## solving for x: log_7(1) = x - 2
Complex numbers, rational functions, logarithms, sequences and series, matrix operations, etc.
### solving for x: log_7(1) = x - 2
log_7(1)=x-2
softballprincess9
Posts: 1
Joined: Tue Nov 10, 2009 6:16 am
The equivalent exponential equation is:
. . . . .$7^{x\, -\,2}\, =\, 1$
What must the power on seven be, to simplify to a value of 1? Set the power equal to this value, and solve the resulting linear equation.
stapel_eliz
Posts: 1785
Joined: Mon Dec 08, 2008 4:22 pm
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# Very simple tcolorbox with picture in header
I try to add picture.png in header of tcolorbox. I want to place this picture in bottom title belt.
This is my box:
\newtcolorbox{SimpleBox}{
breakable,
enhanced,
colback=red!0!white,
colframe=red!75!black,
title={\large Simple box},
}
How I can add picture.png?
When I add before } line
\hfill\smash{\raisebox{-11pt}{\includegraphics[width=1cm,height=1cm]{picture.png}}}
I achieve errors...
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You have to add it inside the title option:
\documentclass{article}
\usepackage{mwe} % just for the example
\usepackage[most]{tcolorbox}
\newtcolorbox{SimpleBox}{%
breakable,
enhanced,
colback=red!0!white,
colframe=red!75!black,
title={\large Simple box\hfill%
\smash{\raisebox{-11pt}{\includegraphics[width=1cm,height=1cm]{example-image}}}},
}
\begin{document}
\begin{SimpleBox}
Some Text
\end{SimpleBox}
\end{document}
Substitute example-image with your picture.png
-
I think mwe package is perfect for such dummy image use. – percusse Apr 8 '14 at 9:54
@percusse You're right. – karlkoeller Apr 8 '14 at 9:54
@HarishKumar I know. Just in case the image is not in the OP's TeX path. – karlkoeller Apr 8 '14 at 9:58
@karlkoeller, thank you. And how I can place picture.png on left side of title? – Ama Apr 8 '14 at 10:02
@ama invert the two things inside the title – karlkoeller Apr 8 '14 at 10:11
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# Running Qualification & Profiling Tool Benchmark
2. Connect to the sparkrunner pod.
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kubectl exec --stdin --tty sparkrunner-0 -- /bin/bash
3. If you have completed any of the previous labs there should be Spark logs in the following location /data/eventlogs. We will be using some or all of those logs to run the Qualification & Profiling Tool Benchmark. Confirm the existence of Spark logs with the following command:
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cd /home/spark
ls /data/eventlogs
• You should see an output that looks something like this:
4. From the list above, select one or more files to use with the following command. You can process one or more files by specifying them on the command line or you can process all files by using a wildcard
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bash /home/spark/lp-run-qua-pro.sh qualification /data/eventlogs/*
5. The output file from the previous command will be located in the /home/spark/qualification directory. There should be a directory for each log that you processed.
6. The results are in CSV format.
7. The script also creates a tar file that contains html documents. The output file can be found at the following location /data/scps/qualification.tar.gz. You can scp the tarball from the Desktop and view the contents with a browser.
• In the left menu open up the Desktop link and click the VNC connect button.
• Open a terminal on the desktop and run the following commands
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cd ~/Desktop
scp nvidia@172.16.0.10:/data/scps/qualification.tar.gz .
tar xfz qualification.tar.gz
• Open the web browser in the Linux desktop.
• Go the following URL file:///home/nvidia/Desktop/qualification and select one of the application IDs listed. Inside the /ui/html directory open the index.html.
• From the web UI you can find some basic application information such as App Name/App Id/App Duration; the Recommendation column classifies the applications into the following different categories:“Strongly Recommended”, “Recommended”, “Not Recommended”, or “Not Applicable”, the latter indicates that the app has job or stage failures. The Estimated Speed-up column estimates how much faster the application would run on GPU. The speed-up factor is simply the original CPU duration of the app divided by the estimated GPU duration.
8. To run the Profiling Tool we need to go back to the sparkrunner window and run the following command. You can process one or more files by specifying them on the command line or you can process all files by using a wildcard.
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bash /home/spark/lp-run-qua-pro.sh profiling /data/eventlogs/*
9. The output file from the previous command will be located in the /home/spark/ profiling directory. There should be a directory for each log that you processed. Unlike the Qualification Tool there is no option to view these output files using a browser.
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react so rapidly with oxygen they form superoxides, in which the alkali metal reacts with $\ce{O2}$ in a 1:1 mole ratio.. Alkali metal oxides, M2O (M is Li, Na, K, and Rb), have the antifluorite structure (refer to Section 2.2 (e)), and Cs2O is the anti-CdCl2 lamellar structure (refer to Section 4.5 (d)). The heteropolyoxo anions expressed with the general formula [Xn+M12O40](8-n)- (M = Mo, W, and X = B, Al, Si, Ge, P, As, Ti, Mn, Fe, Co, Cu, etc.) Legal. It however shows reversible decomposition in closed container . Polyoxo anions are generated by the condensation of MO6 units by removal of H2O when MoO42- reacts with a proton H+, as is shown in the following equation. Therefore, the whole structure shows Td symmetry. Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. The Mg would burn with a bright white flame. It is also a hard material and used for crucibles or firebricks. Tetragonal and blue black tin oxide, SnO, and red lead oxide, PbO, are layer compounds composed of square pyramids with the metal atom at the peak and four oxygen atoms at the bottom vertices. SnO2 is used in transparent electrodes, catalysts, and many other applications. Discuss the trend of the following: Thermal stability of carbonates of Group 2 elements. The Facts The reactions with oxygen Formation of simple oxides Moreover, various fine ceramics (functional porcelain materials) utilizing the properties of $$\alpha$$-alumina have been developed. As shown in Figure $$\PageIndex{13}$$, the rutile-type structure has TiO6 octahedra connected by the edges and sharing corners. What is the order of thermal stability for oxides, peroxide, superoxide of group 1 elements?? V (V), V (IV), Nb (V), and Ta (V) form similar polyoxo acids although their number is limited. Since beryllium oxide is. The trend, therefore, ranges from acidic oxides at the top ⦠Which of the metal carbonates is most stable thermally? Of the two forms of alumina, Al2O3, $$\alpha$$ alumina and (\gamma\) alumina, $$\alpha$$ alumina takes the corundum structure and is very hard. Many other types of heteropolyoxo anions are known. The charge imbalance of the charge is compensated by the partial oxidation of Fe2+ into Fe3+. Group 2 reactions Reactions with water. Although GeO2 has a rutile-type structure, there is also a $$\beta$$ quartz-type polymorphism. The nitrates are white solids, and the oxides produced are also white solids. Stability of oxides decreases down the group. Is it possible to generalize chemical stability of group of materials versus the others? BeCO 3 â BeO + CO 2. Especially quicklime, CaO, is produced and used in large quantities. The structures of polyoxoacids are now readily analyzed with single crystal X-ray structural analysis, 17O NMR, etc. Start studying Reactions of Group 2 Oxides and Hydroxides, and trends in solubility. There are many polyoxo acids and their salts of Mo(VI) and W (VI). It is a flammable gas, which is used in the manufacturing of various inorganic and organic chemicals. It has a 2-dimensional lamellar structure in which the chains of edge-sharing octahedra MoO6 are corner-linked. This is called stabilized zirconia. Zirconium dioxide, ZrO2, has a very high melting-point (2700 °C), and is resistant to acids and bases. Take the test now! Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students. They are obtained by calcination of the metal carbonates. The carbonates become more stable to heat as you go down the Group. 2. It has many chemical uses including as a catalyst, a catalyst support, and in chromatography. Because of their usefulness as industrial catalysts or for other purposes, polyoxoacids are again being studied in detail. Oxygen shows -2 oxidation state in general except in OF. Perovskite, CaTiO3, is an ABO3 oxide (the net charge of A and B becomes 6+), and it has a structure with calcium atom at the center of TiO3 in the ReO3 structure (Figure $$\PageIndex{16}$$). Missed the LibreFest? Surface treatment with tin oxide enhances heat reflectivity of glasses. Hence, more is the stability of oxide formed, less will be stability of carbonates. The stability of "normal" oxides decreases, while that of superoxides increases going down the group. Among this kind of compounds, BaTiO3, commonly called barium titanate, is especially important. There is very little known about the surface structures of transition metal oxides, but their bulk crystal structures are well researched.The approach to determine the surface structure is to assume the oxides are ideal crystal, where the bulk atomic arrangement is maintained up to and including the surface plane. The dioxides of Sn, Pb, and other transition metals with small ionic radii take rutile-type structures (Figure $$\PageIndex{13}$$), and the dioxides of lanthanide and actinide metals with large ionic radii take fluorite-type structures. Peroxide M2O2 (M is Li, Na, K, Rb, and Cs) can be regarded also as the salts of dibasic acid H2O2. Crystal field stabilization energies (refer to Section 6.2 (a)) differ depending on whether the crystal field of the oxygen atoms is a regular trahedron or octahedron. It explains why it is difficult to observe many tidy patterns. 3) Anhydrous CaCl 2 is also used as a desiccant ( drying agent in laboratory). Reactivity of group 2 metals increases down the group Magnesium burns in steam to produce magnesium oxide and hydrogen. Unless otherwise noted, LibreTexts content is licensed by CC BY-NC-SA 3.0. Superoxide MO2 (M is K, Rb, and Cs) contains paramagnetic ion O2-, and is stabilized by the large alkali metal cation. A common misconception is that decrease in polarisation of the carbonate ion due to decreased charge density results in thermal stability decreasing down the group, rather than the reverse. This can be explained as follows: The size of lithium ion is very small. 26. The history of polyoxoacids is said to have started with J. Berzelius discovering the first polyoxoacid in 1826, with the formation of yellow precipitates when he acidified an aqueous solution containing Mo (VI) and P (V). 2 and O 2F 2 The stability of +6 oxidation state decreases and +4 oxidation state increases due to inert pair effect. It is also much more important in Group 2 than in Group 1 where the ions only carry one positive charge. In the normal rutile-type structure, the distance between adjacent M atoms in the edge-sharing octahedra is equal, but some rutile-type metal oxides that exhibit semiconductivity have unequal M-M-M distances. Tungsten trioxide, WO3, is the only oxide that shows various phase transitions near room temperature and at least seven polymorphs are known. Magnesium and calcium nitrates normally ⦠Abstract The formation of four hitherto unknown lead tellurium oxides â PbTeO3, PbTe2O5, Pb2TeO4 and Pb2Te2O6 â was observed in the gas phase by means ⦠Lead oxide is strongly oxidizing and used for the manufacture of chemicals, and PbO2 forms in a lead batteries. The kinetics of the reaction MeO x â Me+x/2 O 2 is discussed. So boiling point in correct order is N a F < N a C l < N a B r < N a I. Spinel, MgAl2O4, has a structure in which Mg2+ occupy 1/8 of the tetrahedral cavities and Al3+ 1/2 of the octahedral cavities of a ccp array of oxygen atoms (Figure $$\PageIndex{15}$$). Chemistry zimsec chapter 24 group iv 1. The smaller ions on top will have more polarizing effect on oxygen than the bigger ones at the bottom of the group as the nucleus is closer to the oxygen atom. As heteropolyoxo anions contain metal ions of the highest oxidation number, they are reduced even by very weak reducing agents and show mixed valence. This ferroelectric functional material is used in nonlinear resistance devices (varistor). They are prepared by heating the metal powder in an oxygen atmosphere at about 800 °C. Na2O2 is used industrially as a bleaching agent. A number of studies on the solution chemistry of dissolved anions have been performed. Group 17: Group 18: Period 3 oxides: Na 2 O: MgO : Al 2 O 3: SiO 2: P 4 O 6: SO 2: Cl 2 O no oxide : Trend in bond character: ionic â â â â covalent Trend in structure: (25 o C, 100 kPa) 3-dimensional ionic lattice â 3-dimensional covalent network â discrete covalent molecules Do you understand this? All the nitrates in this Group undergo thermal decomposition to give the metal oxide, nitrogen dioxide and oxygen. Other ternary oxides of group 14â16 elements were not observed in the gas phase. The stability of -2 oxidation state decreases down the group due to increase in atomic size and decrease in electronegativity. Stability of oxides decreases down the group. Those consisting only of metal, oxygen, and hydrogen atoms are called isopolyacids and those containing various other elements (P, Si, transition metals, etc.) i.e. High temperature X-ray studies confirmed the strong anisotropy of thermal expansion in the case of RuO 2 and IrO 2. So, as the thing goes, Lithium forms oxides(M2O) one oxygen balanced by two lithium atoms. are called heteropolyacids. This page looks at the effect of heat on the carbonates and nitrates of the Group 2 elements â beryllium, magnesium, calcium, strontium and barium. Ensure you provide a clear explanation for the thermal stability of Group 2 carbonates. It however shows reversible decomposition in closed container. The uses of the oxides of group 14 elements are mentioned below. Mercury oxide, HgO, is a red crystallline compound that is formed when mercury nitrate is heated in air. As we move down the alkali metal group, we observe that stability of peroxide increases. BeC0 3 âBeO + C0 2. Which of the following carbonates decomposes readily at low temperatures? What a nightmare! Their melting points are very high and all are refractory. The salts of polyacids have counter-cations such as sodium or ammonium instead of protons. These polymorphs have the ReO3-type three-dimensional structure with corner-sharing WO octahedra. Since these oxides are very volatile and poisonous, they should be handled very carefully. As a result, the spread of negative charge towards another oxygen atom is prevented. Hence, more is the stability of oxide formed, less will be stability of carbonates. In the corundum structure, 2/3 of the octahedral cavities in the hcp array of oxygen atoms are occupied by M3+. Therefore, the size and form of heteropolyoxo anions in the crystal precipitation are decided by the choice of acid, concentration, temperature, or the counter cation for crystallization. The acid-base behavior of the Group 4 oxides. The stability of peroxide and superoxide of alkali metals increase as we go down the group. THERMAL STABILITY OF THE GROUP 2 CARBONATES AND NITRATES This page looks at the effect of heat on the carbonates and nitrates of the Group 2 elements - beryllium, magnesium, calcium, strontium and barium. Down the group, the relative stability of the +4 oxidation state decrease and the relative stability of the +2 oxidation state increase. Except for BeO (Wurtz type), the basic structure of Group 2 metal oxides MO is the rock salt structure. Alternatively, M2O is obtained by the pyrolysis of M2O2 after complete oxidation of the metal. Since beryllium oxide is high stable, it makes BeCO3 unstable. Have questions or comments? Therefore, when the metal component is a transition metal, the energy difference is one of the factors to determine which of A2+ or B3+ is favorable to fill the tetrahedral cavities. The most important structure of the oxides of this composition is the corundum structure (Al, Ga, Ti, V, Cr, Fe, and Rh). Watch the recordings here on Youtube! PbO2 usually has a rutile-type structure. Especially quicklime, CaO, is produced and used in large quantities. It is used as an oxidation reagent in organic chemistry. Hence, more is the stability of oxide formed, less will be stability of carbonates. are formed. Rhenium and tungsten oxides are important compounds with this composition. $12 [MoO_{4}]^{2-} + HPO_{4}^{2-} \xrightarrow{H^{+}} [PMo_{12}O_{40}]^{3-} + 12 H_{2}O$. The LibreTexts libraries are Powered by MindTouch® and are supported by the Department of Education Open Textbook Pilot Project, the UC Davis Office of the Provost, the UC Davis Library, the California State University Affordable Learning Solutions Program, and Merlot. Therefore the electrostatic attractive forces between the positive ions and the delocalized electrons weaken. There is the increase in disorder as the crystal lattice breaks up, but a corresponding increase in order in the water - which varies depending on the sizes and charges of the ions present. The oxides of the elements at the top of Group 4 are acidic, but this acidity decreases down the group. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The salt containing one or more atoms of oxygen such as oxides ,hydroxides ,carbonate ,bicarbonate ,nitrite ,nitrate ,sulphates ,oxalates and phosphates are called oxo salts. Thus, a heteropolyoxo anion can serve as an electron sink for many electrons, and heteropolyoxo anions exhibit photo-redox reactions. Solution for group 1 elements with that of group 2 on the basis of the following:⦠Although the Keggin structure is somewhat complicated, it is very symmetrical and beautiful and is the most typical structure of heteropolyoxo anions. For example, FeO has the composition FexO (x = 0.89-0.96) at 1000 °C. Except for BeO (Wurtz type), the basic structure of Group 2 metal oxides MO is the rock salt structure. The structure contains metal atoms above and below the layer of oxygen atoms alternately and in parallel with the oxygen layers (Figure $$\PageIndex{11}$$).
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# Problem concerning the use of Pigeonhole (Box) principle
Question:
Take any $$37$$ integers from the set {$${1,2,…,112}$$}. Show that there will always exist two integers $$x,y$$ out of those $$37$$ integers such that $$\mid x-y \mid \in \{9,10,19\}$$.
Approach:
What have I done so far:
Let $$S=$$ {$${1,2,…,112}$$}
We partition the set into subsets $$S_i$$ of the form $$\{x, x+9, x+19\}$$. Then the difference of any two elements is in $$\{9, 10, 19 \}$$, which is easy to see.
The following partitions are made (for $$x=1, 2, \cdots , 9$$): $$\{1, 10, 20 \}, \{2, 11, 21 \}, \cdots, \{9, 18, 28\}$$ Then next we choose $$x=29$$ to maintain the disjoint sets essential for our proof. This gives the disjoint sets $$\{29, 38, 48\}, \cdots, \{37, 46, 56 \}$$ and similarly $$\{85, 94, 104 \}, \cdots, \{93, 102, 112 \}$$
However as the quick reader may see that the numbers $$\{19, 47, 75, 103\}$$ do not occur in any set. However, I decide to do a case by case analysis of the situations. Name this set as $$X$$.
Suppose, initially, that out of the $$37$$ integers in our selection, none belong to $$X$$. Then it follows from Dirichlet's box principle that at least two elements are from the same set (i.e. from one of the subsets that we partitioned $$S$$ into) then the claim is valid.
Now suppose that one element from $$X$$ is in our selection, say $$19$$ then if at least one of $$9, 28, 29, 38$$ is in our selection, then the claim is valid.
Suppose none of these are present, and we are deficit in four integers. We can now select any four integers from the remaining numbers and the box principle guarantees that at least two are from the same set.
For, even if all $$3$$ other elements of $$X$$ are now present, there is one empty slot which can be filled using the other subsets from where we already have at least one element in our choice of $$37$$ numbers.
I hope this is comprehensible because my combinatorics proof writing abilities are horrible. I am preparing for Olympiads and also for being a good Mathematician in general. Thank you for the help :)
Edit:
It seems I didn't enter my main question, apologies. Is my solution correct?
• What is your question? Feb 24 '18 at 17:09
• I understand the math question. Are you asking whether your solution is correct? Feb 24 '18 at 17:12
• @saulspatz yes sorry Feb 24 '18 at 17:13
• I have trouble understanding the two paragraphs starting with, "Suppose none of these are present ..." I'm not saying they're wrong, just difficult to follow. It might be better to say, "Suppose none of them are present. Then the remaining 36 choices come from as set of 107 elements ..." Feb 24 '18 at 17:19
• @saulspatz i want to say that if from our selection of the 37 integers in S, at least one of 9, 28, 29, 38 are present in addition with our choice of 19, then we have our claim. Then we suppose that none of these are present, so 19 cannot form the pair required. Feb 24 '18 at 17:21
Nice job, I think your reasoning is all there but it will help to break down your argument a little bit, to make it easier to read.
First you partitioned the interval $\{1,\cdots 112\}$ into $37$ sets, all of the form $S_x = \{x, x+9, x+19\}$ except for the exceptional set $X = \{19, 47, 75, 103\}$. Then we examine how $X$ interacts with the $S_x$. For any $z \in \{1,\cdots 112\}$, define $$B_z = \big\{y \in \{1,\cdots 112\} \text{ such that } |y-z| \in \{9,10,19\} \big\}$$
We make the important observation that for each $y \in X$, $B_y \supset S_{y-10}$. That is to say, for each element we place in $X$, we invalidate an additional $S_x$.
Now we have to place $37$ elements among the $37$ sets.
Suppose we place $0 \leq n \leq 4$ elements in $X$. This leaves $37 - n$ elements to place among the $36$ $S_x$. From the above observation, $n$ choices of the $S_x$ will immediately result in elements a 'bad' distance apart. So only $36 - n$ choices of the $S_x$ are viable. We are thus placing $37 - n$ elements in $36 - n$ of the $S_x$, and by pidgeonhole, one of the $S_x$ must contain two elements.
• Thank you so much. I am very new to Olympiad Combinatorics and in fact this is my first takedown on an AoPS combi problem. Your contribution fixes my proof altogether. Thank you so much. I still need a way to hone my proof writing skills. Thanks again :) Feb 24 '18 at 18:15
• Don't worry! The creative part of the problem was figuring out how to construct a partition and apply the pigeonhole principal, and you got that. The rest will follow naturally from practice, and especially practicing verbal math communication with other human beings. Feb 24 '18 at 18:37
Just to show another possible way to tackle the problem.
Taking $S=\{1,\,2,\, \cdots,\,112\}$ or $S=\{0,\,1,\, \cdots,\,111\}$ or any set of $112$ consecutive integers clearly does not change the problem. Let's fix $S=\{0,\,1,\, \cdots,\,111\}$.
Then taking the set $T$ of $37$ integers, it is also clear that if we shift it as to have the minimum at $0$ does not change the problem.
Therefore we can start $T$ as $\{0,\, 1,\, 2,\, \cdots,\, 8\}$ (tot. of $9$ integers)
after which we shall jump the set $\{9,\, \cdots,\,18\}$ and $\{19,\, \cdots,\,27\}$ , i.e. $19$ integers.
The most compact way that we can proceed with is to repeat the above starting with $28$.
To reach to $|T|=37$ we need to fix $4$ banned sets, i.e. $76$ integers.
But $112-76=36 < 37$, so we cannot avoid that at least one integer be in banned set.
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# Pic16F628 + portexpander I2C
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#### kowey
##### New Member
A humble request from a new visitor!
For a couple of days now, I have been trying to connect a PIC16F628 with a port expander (Philips PCF8574) via I2C. Alas, without succes. Hardware looks OK, the port expander works well (with arduino), the pic is OK: mplab, pickit2, win2K. Compiles and burns without problems. Pullups on both lines (15K). Everything mounted on a breadboard, connections checked umpteen times with a digital multimeter. No, SCL and SDA are not reversed!
Here is my code:
http://pebblescorner.be/robotics/test.asm
Alas, I do not have an oscilloscope, so I cannot see what is going on. I do see that SDA and SCl are high when not busy.
I thought that I really understood the whole I2C thing, but now I am beginning to doubt even that. So, in order to check that out too, I tried one of the excellent tutorials of
Nigel's PIC Tutorial Page (tutorial 6.1: eeprom and LCD).
I constructed the whole thing on a breadboard, (an 24C2 instead of a pcf8574), compiled Mr. Goodwin's code, burned & turned on the power, and read: "writing ...efg" on the LCD. An error! With I2C again! Ohoh!!
I have spend so much time at it lately that my wife has started giving me "the look". Any hint or advice is very much appreciated! It could even save my marriage! (Just joking)
Thanks, and keep up the good works.
#### jimlovell777
##### New Member
I was having a similar issue not to long ago and in my case a noisy power supply was to blame so better filtering on your supply might be worth trying. Also of course keep the data and clock lines short and as noise free as possible on a breadboard.
#### blueroomelectronics
##### Well-Known Member
Why not use a PIC with I2C hardware like the 16F88?
#### be80be
##### Well-Known Member
I'd tell what it is but I don't think you'll believe me. Your using the pickit2 for power. Can't do that have to power the chip with 5 volts on it's own and not have the pickit2 hooked up. I did the same thing for a week couldn't get Nigel Tutorial to work thought
I had bad chips Lol unhook the pickit2 and power it up with my supply and away she went. See your using RB6 and 7 same pins the pickit2 use to program with it kills the signal.
Both b6 and b7 are tied to gnd with 4.7K resistors. One more variable in the works.
Having a pullup and pulldown resistor creates a voltage divider. You need to move the ICSP SDA line to another pin
That's what happens the pickit2 pulls RB6 and RB7 to gnd with 4.7 ohm resistor
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#### kowey
##### New Member
Dear Be80be:
quote:"...I'd tell what it is but I don't think you'll believe me. Your using the pickit2 for power. ...". Indeed I do not: after burning, I always disconnect the pickit2 and use a battery for power. But your hint is very wellcome indeed and it will be most helpfull for future projects.
Mr. Jimlovell777, I see that my datalines are not only ridiculously long, they are nicely coiled so that the workbench is not too cluttered. Dimwit has perhaps created an induction-coil. Even a 16F88 would probably object to that! I 'll sort that out and see if that helps....
Thank all of you for considering my problem.
#### blueroomelectronics
##### Well-Known Member
Since you have a PK2 you could rig it up to capture the SCK, SDA using the logic tool mode.
#### be80be
##### Well-Known Member
Well that's what made mine not work and there 1 more are you building in debug in mplab or release use release
I constructed the whole thing on a breadboard, (an 24C2 instead of a pcf8574), compiled Mr. Goodwin's code, burned & turned on the power, and read: "writing ...efg" on the LCD. An error! With I2C again! Ohoh!!
You sure you have a 10k pulling them up
the SCL and SDA because that's the error you get when floating.
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#### AtomSoft
##### Well-Known Member
not sure if its just me not knowing but i thought when you set the TRIS it just sets the direction and you still have to set the PORT value itself.
Code:
send_start_bit
;initialize: SDA and SCL must be high
bsf STATUS,RP0
bsf I2C_TRIS,SDA
bsf I2C_TRIS,SCL
nop
;send start bit by bringing SCL low
bcf I2C_TRIS,SCL
bcf STATUS,RP0
return
should be more like:
Code:
send_start_bit
;initialize: SDA and SCL must be high
bsf STATUS,RP0
bcf I2C_TRIS,SDA
bcf I2C_TRIS,SCL
bsf I2C_PORT,SDA
bsf I2C_PORT,SCL
nop
;send start bit by bringing SCL low
bcf I2C_PORT,SCL
bcf STATUS,RP0
return
When setting the TRIS a 1 = input and a 0 = output. so you have to set both to output and then set low/high.
If im right and i think i am lol you have to repair alot of that code
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#### AtomSoft
##### Well-Known Member
Try this:
Code:
LIST p=16F628 ;tell assembler what chip we are using
include "P16F628.inc" ;include the defaults for the chip
__config 0x3D18 ;sets the configuration settings (oscillator type etc.)
cblock 0x20 ;start of general purpose registers
counta ;used in delay routine
countb ;used in delay routine
countc ;used in delay routine
countx ;used in delay routine
flags
w_temp ;temp storage used by isr
status_temp
;general registers used by I2C
I2C_data ;here comes the data that will be send
I2C_buffer ;buffer used during the writing of a byte
I2C_index ;7>6>5>4>3>2>1
I2C_failure ;I2C_failure > 0: true (1) or false(0)
I2C_countdown_tries ;if this is zero = total failure!!
I2C_counter ;counter used by waiting for ACK
endc
I2C_PORT equ PORTB
I2C_TRIS equ TRISB
#define SDA 7
#define SCL 6
org 0x0000 ;org sets the origin, 0x0000 for the 16F628,
;this is where the program starts running
goto main
;**************************************************************************
;I2C LOW LEVEL STUFF BEGINS HERE******************************************
;**************************************************************************
low_SDA
bsf STATUS,RP0
bcf I2C_TRIS,SDA
bcf STATUS,RP0
bcf I2C_PORT,SDA
return
low_SCL
bsf STATUS,RP0
bcf I2C_TRIS,SCL
bcf STATUS,RP0
bcf I2C_PORT,SCL
return
high_SDA
bsf STATUS,RP0
bcf I2C_TRIS,SDA
bcf STATUS,RP0
bsf I2C_PORT,SDA
return
high_SCL
bsf STATUS,RP0
bcf I2C_TRIS,SCL
bcf STATUS,RP0
bsf I2C_PORT,SCL
return
SCL_pulse
call high_SCL
call low_SCL
return
reset_I2C_registers
clrf I2C_buffer ;buffer used during the writing of a byte
clrf I2C_index ;7>6>5>4>3>2>1
clrf I2C_failure ;I2C_failure > 0: true (1) or false(0)
movlw d'100'
movwf I2C_countdown_tries ;if this is zero = total failure!!
movwf I2C_counter ;counter used by waiting for ACK
return
;*************************************************************************
send_start_bit
;initialize: SDA and SCL must be high
bsf STATUS,RP0
bcf I2C_TRIS,SDA
bcf I2C_TRIS,SCL
bcf STATUS,RP0
bsf I2C_PORT,SDA
bsf I2C_PORT,SCL
nop
;send start bit by bringing SCL low
bcf I2C_PORT,SCL
return
;**************************************************************************
send_stop_bit
;initialize: SDA and SCL must be high
bsf STATUS,RP0
bcf I2C_TRIS,SDA
bcf I2C_TRIS,SCL
bcf STATUS,RP0
bsf I2C_PORT,SCL
nop
;send stop bit by bringing SDA high
bsf I2C_PORT,SDA
return
;**************************************************************************
send_bit_high ;beginnig SDA and SCL low
call high_SDA
call SCL_pulse
return
;**************************************************************************
send_bit_low ;beginnig SDA and SCL low
call low_SDA
call SCL_pulse
return
;**************************************************************************
wait_for_ack
;SDA should be high! The slave is expected to bring it low
call high_SDA
call high_SCL
;prepare counter
movlw d'100'
movwf I2C_counter
wait_loop
btfsc I2C_PORT,SDA
goto SDA_is_still_high
goto ack_SDA_is_cleared
SDA_is_still_high
decfsz I2C_counter,f
goto wait_loop
call send_stop_bit
return
ack_SDA_is_cleared
;give a pulse
bsf STATUS,RP0
bsf I2C_TRIS,SCL
nop
bcf I2C_TRIS,SCL
bcf STATUS,RP0
;finished pulsing; clear failure (succes) and return
bcf I2C_failure,0 ;succes
return
;**************************************************************************
send_byte ;the byte should be in the working_register
;bits in the buffer are send MSB first
;prepare
movlw d'8'
movwf I2C_index
movwf I2C_buffer
;send the bits
send_the_bit
btfsc I2C_buffer,7
goto the_bit_is_high
goto the_bit_is_low
the_bit_is_high
call send_bit_high
goto check_if_sending_is_finished
the_bit_is_low
call send_bit_low
call high_SDA
goto check_if_sending_is_finished
check_if_sending_is_finished
decfsz I2C_index,f
goto get_next_bit
return
get_next_bit
rlf I2C_buffer,f
goto send_the_bit
;********************************************************************************
do_write_sequence
;prepare the 7bit-addres of the device, put in the buffer and roll left
;LSB should be 0 when writing
movwf I2C_buffer
rlf I2C_buffer,f
bcf I2C_buffer,0
;start the writing, (startbit + address), wait for ACK, if errors: restart
call send_start_bit
call send_byte
call wait_for_ack
btfsc I2C_failure,0 ;succes?
goto another_try
;now write the data, if errors: restart
movfw I2C_data
call send_byte
call wait_for_ack
btfsc I2C_failure,0 ;succes?
goto another_try
call send_stop_bit
return ;succes!!!!!
another_try
decfsz I2C_countdown_tries,f
goto do_write_sequence ;restart
call send_stop_bit
return ;give up
;**************************************************************************
;I2C LOW LEVEL STUFF ENDS HERE******************************************
;**************************************************************************
setup
;turn comparators off (make it like a 16F84)
movlw 0x07
movwf CMCON ;turn comparators off (make it like a 16F84)
;setup ports
bsf STATUS, RP0 ;select bank 1
;in TRISA and TRISB 0= output, 1 = INPUT
;RA4 and RA5 only POSSIBLE AS OUTPUT
movlw b'11111111'
movwf TRISA ;set PortA all inputs
movlw b'11111111' ;set PortB all inputs
movwf TRISB
clrf OPTION_REG ;disable internal pullups on port-b
bsf OPTION_REG,7
;back to bank0:
bcf STATUS, RP0 ;select bank 0
movlw b'00000000'
movwf PORTA
movwf PORTB ;set all bits off
;NO interrupts:
clrf INTCON ;clear flags and switches
retlw 0
;**************************************************************************
;**************************************************************************
;**************************************************************************
;to wait x msec (max 255!) put x in the working register
;and call this routine (wait_x_msec)
wait_x_msec
Loop_c movwf countc
loop_b movlw d'10'
movwf countb
loop_a movlw d'100'
movwf counta
decfsz counta, f
goto \$-1
decfsz countb, f
goto loop_a
decfsz countc ,f
goto loop_b
return
;**************************************************************************
;**************************************************************************
;**************************************************************************
main
call setup
call reset_I2C_registers
movlw b'100000' ;address of Philips port expander
movlw b'11111111'
movwf I2C_data
loop
movlw d'250'
call wait_x_msec
movlw d'250'
call wait_x_msec
movlw d'250'
call wait_x_msec
movlw d'250'
call wait_x_msec
movlw b'00000000'
movwf I2C_data
call do_write_sequence
movlw d'250'
call wait_x_msec
movlw d'250'
call wait_x_msec
movlw d'250'
call wait_x_msec
movlw d'250'
call wait_x_msec
movlw b'11111111'
movwf I2C_data
call do_write_sequence
goto loop
end
#### jimlovell777
##### New Member
It's supposed to be like that. When using I2c you use resisters to pull the clk and data lines high so anything can talk on the bus by pulling the lines low. If you left the uC pin as an output you'd essentially be shorting the pin to ground, so instead of doing that you switch the pin to input mode (TRIS=1) which makes it high impedance and leaves the bus free to operate. I've really simplified the process and I'm leaving a lot out but if you want to know more about I2c and uC control techniques google it.
Edit: Oh also changing the TRIS value for a pin from Input to Output typically doesn't affect the pins output value, at least with the PIC micros I'm used to dealing with. If you want to know why again try google or look at the block diagram for a pin in a uC datasheet. Microchip PIC datasheets normally include such diagrams.
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#### AtomSoft
##### Well-Known Member
heh i learned to do it one way which never gives me a issue so i stick to it. I know enough about i2c to get it working 100% and about pics as well. Im not the one with the non working I2C so heh maybe you should give advice to the other guy.
#### be80be
##### Well-Known Member
I told you the only time my I2C not working it was the pickit2 pulling RB6 & RB7 low can't power with it. But what Atom is telling you to send data your pins have to be output to receive data your pins need to be input. can't work just setting the tris. Say you set the
Tris to output and thats all you do then it will read as low if you don't set it high It will never go high it will only send out a 0 you what some 01011100 going out that pin.
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Thanks Burt
#### Pommie
##### Well-Known Member
You never set either pin to output and drive it high. The way I²C works is by having pullups so you either have the pin as input and the line gets pulled high by the pullups or you set it to output and low. If you drive the bus high then other devices can't pull it low.
Mike.
#### AtomSoft
##### Well-Known Member
ok but i assumed only 1 device can be used at a time anyway which means it doesnt matter if the others cant use the lines.
#### Pommie
##### Well-Known Member
If you drive the line high then the other device can't send any data back and so a read of any device will not work. If you have somehow got this to work then you have bus contention.
Mike.
#### be80be
##### Well-Known Member
Mike that's not what I'm trying to say what I'm saying is how do you sent data out a input?
You send it out a output right.
So to send data out you set your line to output send the data out 100110 like that when done you change back to input to wait for data to be received
Which is polling the line to see if it gos low.
Now this is what i'm thinking I set to send data out I make my pin high so as no
errors happen clock out my data return to input. Seeing the line is high to start why would you want to come on line low. I no you can't hold the line high or low You have to return to input.
#### Pommie
##### Well-Known Member
Burt,
With I²C you either,
Do nothing (leave as input) to the line and the pullups make it a high.
Pull the line low. Set pin to output and low.
There is never any need to drive it high. And, if you do it will stop working.
Mike.
#### 3v0
##### Coop Build Coordinator
Forum Supporter
Since you have a PK2 you could rig it up to capture the SCK, SDA using the logic tool mode.
This is good advice. It is easier to look at the output then check the code to see why it is wrong.
EDIT: In the PICkit2 programmer software (not MPLAB) go to TOOLS>LOGIC_TOOL to see how to connect the PICkit2 as a logic analyzer.
3v0
#### AtomSoft
##### Well-Known Member
Pommie you are right too but. You can do the same with a pullup and using a normal high/low scheme as output. It wouldnt short because of the resistor.
Im sure he has only 1 device on the bus. I understand its use for multiple I2C devices but this is not the case.
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# From Julius Victor Carus 28 January 1868
Leipzig
Jan 28th. 1868.
My dear Sir,
As the printing of the 2. Volume goes on, rather slowly just now, I have to ask you again some questions.1
On p. 68. you mention again the egyptian Goose as Tadorna aegyptus Of course it will be Anser.2 It didn’t strike me as some authors think, the χηναλώπηξ of the Ancients was Anser Tadorna.
P. 170. Note 109. Ann. de science. nature 2. Sér. Zoolog. This is I think a misprint for Botan., as Decaisne never wrote in the Zoological Series3
P. 229. l. 12 from above “in proportion to the white” must it not be “black”. As it stands now, you say: “the white are sluggish in proportion to the white”.4
I hope your health is pretty well.
Believe me | Yours most sincerely | Prof J. Victor Carus
## CD annotations
3.2 Series] ‘(Dujardin—)’ ink
Top of letter: ‘thirteen for ourselves5 | Last sheets | Clean copy’ pencil
## Footnotes
Carus refers to the German translation of Variation (Carus trans. 1868).
In Variation 2: 68, CD referred to the Egyptian goose as Tadorna Aegyptiacus; he changed the name to Anser Aegyptiacus in the second printing. The species is now known as Alopochen aegyptiacus.
In Variation 2: 170 n. 109, CD reported an observation of Lysimachia nummularia by Joseph Decaisne; Decaisne’s observation appeared in a zoological article by Félix Dujardin (Dujardin 1845). See CD’s annotation.
In Variation 2: 229, CD quoted from M. G. Lewis 1845, p. 100, on the horned cattle of the West Indies: ‘The white [cattle] are terribly “tormented by the insects; and they are weak and sluggish in proportion to the white’” (that is, the cattle were weak and sluggish in proportion to their whiteness).
The number may refer to the number of presentation copies: there are eleven names on CD’s presentation list for the German edition of Variation (see Correspondence vol. 16, Appendix IV).
## Bibliography
Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.
Dujardin, Félix. 1845. Sur le développement des méduses et des polypes hydraires. Annales des Sciences Naturelles. Zoologie 3d ser. 4: 257–81.
Lewis, Matthew Gregory. 1845. Journal of a residence among the negroes in the West Indies. London: John Murray.
Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.
## Summary
Queries concerned with translating vol. 2 of Variation.
## Letter details
Letter no.
DCP-LETT-5809
From
Julius Victor Carus
To
Charles Robert Darwin
Sent from
Leipzig
Source of text
DAR 161: 66
Physical description
2pp †
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# Tag Info
## Hot answers tagged growth-accounting
3
Let $y=Y/L$ and $k=K/L$ be the per-worker levels of output and capital. Observe that $y=Ak^\alpha$. Steady state is given by: $$k^*=sy^*+(1-\delta)k^*,$$ or $$k^*=sA(k^*)^\alpha+(1-\delta)k^*.$$ Doing the algebra: $$k^*=\left(\frac{sA}{\delta}\right)^{\frac{1}{1-\alpha}}.$$ And: y^*=A\left(\frac{sA}{\delta}\right)^{\frac{\alpha}{1-\alpha}}=A^{\frac{1}{1-...
2
I'm pretty sure he means "1 minus the labour share percentage", i.e. he's estimating the capital share of GDP as the proportion of GDP not going to labour. It's not typeset well, but he has used an em-dash (longer) after "GDP" and a minus sign (shorter) after "1".
2
I would say people usually use log-returns for continuous data (although no data is really continuous, not even tick data). And discrete returns when your data is discrete. In the case of GDP, you only get the data every 3 months, so that is as discrete as it gets.
2
Interesting question. In effect, while factor shares were thought to have remained fairly stable over a long time (the first of the Kaldor's facts), more recently they have varied, particularly in the direction of a fall in the labour share. This short paper from (2012) shows that under such scenario, a growth accounting exercise which assumes constant ...
Only top voted, non community-wiki answers of a minimum length are eligible
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# Why sodium is the worst reducing agent in group 1?
Analysing the oxidation enthalpies for $\ce{Li}$, $\ce{Na}$ and $\ce{K}$, we have their respective values:
1. $\ce{Li} = \pu{162 kJ/mol}$
2. $\ce{Na} = \pu{202 kJ/mol}$
3. $\ce{K} = \pu{188kJ/mol}$
Sodium has the largest positive oxidation enthalpy, which means that its oxidation will be less likely to happen according to its Gibbs free energy. But, why does this happens to sodium?
• These are all negative I'm afraid. Jun 30 '17 at 20:56
• I don't think they are... Take Lithium, for example: Dh(sublimation) = 161 kj/mol. Dh(ionization) = 520 kJ/mol. Dh(hydration) = -519 kJ/mol. Jun 30 '17 at 21:46
• Considering that Dh(oxidation) is: Dh = Dh(subli) + Dh(ioniz) + Dh(hydr), it will be positive... Jun 30 '17 at 21:47
• Maybe, no idea why you didn't use standard electrode potentials. Jun 30 '17 at 22:05
• Currently, i am making an analysing of the Dh, Dg and the standard electrode potentials to explain why the elements of the group 1 are the best reducing agents. This was easy to explain, but when i go through the elements of group 1, the Sodium is the problem, because he has a higher Dh(oxidation) and a lower Standard Electrode Potential. This is what i am really stuck, because those two factors will tell that Sodium is the worst Reducing agent on group 1 Jun 30 '17 at 22:09
The general trend in the reactivity of the group 1 elements is that it increases down the group. This can be attributed to the decrease in 1st ionisation energy as the atomic radius increases.
Reducing power can be measured by the standard electrode potential E0. This refers to the half - cell:
$$M^+(aq)+e⇌M(s)$$
If you look at the values for group 1 we see a different pattern:
Electrode Potential (V) Li. -3.02 Na. -2.71 K. -2.92 Rb. -2.99 Cs. -3.02
Lithium has an anomalously large and negative electrode potential. After Li the values become more large and negative, indicating, as you rightly say, that sodium has the lowest reducing power.
The reason for the unusual value for lithium is that E0 values are measured in solution whereas ionisation energies are measured in the gaseous phase.
To turn a metal atom in the solid state into an aqueous ion we can think of a 3 step process:
The metal is atomized. $\ce{Li(s)→Li(g)}$
The metal is ionised. $\ce{Li(g)→Li+(g)+e}$
The ion is hydrated. $\ce{Li+(g) +(aq)→Li+(aq)}$
Steps 1 and 2 are both endothermic, i.e. they require energy. Step 3 is exothermic as it is a bond forming process. It is referred to as the enthalpy of hydration.
The small size of the lithium ion gives it a large charge density and so water molecules are strongly attracted giving a large, negative enthalpy of hydration.
This is the main factor responsible for lithium's large, negative electrode potential.
In aqueous conditions it is as reducing as cesium though much less reactive in anhydrous conditions.
This anomaly accounts for sodium having the lowest reducing power, but only in aqueous conditions.
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# Mathematics Colloquium
## Limiting absorption principle and virtual levels of operators in Banach spaces
### When
November 12, 2021 | 3:30 - 4:30 p.m.
### Where
University Hall 1005
Andrew Comech
### Abstract
Virtual levels, also known as threshold resonances, admit several equivalent characterizations:
1. there are corresponding "virtual states" from a space "slightly weaker" than L^2;
2. there is no limiting absorption principle in their vicinity (e.g. no weights such that the "sandwiched" resolvent is uniformly bounded);
3. an arbitrarily small perturbation can produce an eigenvalue.
We develop a general approach to virtual levels in Banach spaces and provide applications to Schroedinger operators with nonselfadjoint potentials and in any dimension, deriving optimal estimates on the resolvent.
## Renormalization in Conformal Dynamics
### When
October 15, 2021 | 3:30 - 4:30 p.m.
### Where
University Hall 1005
### Speaker
Dr. Nikita Selinger
### Abstract
Renormalization is a technique that allows us to study a dynamical system on small scales by restricting an iterate of the original system to a small part of the original domain. Successful renormalization theories produce rigidity statements: the geometry of an infinitely renormalizable system is completely determined by its combinatorial properties. Studying dynamics of the renormalization operator itself yields understanding of the structure not only of individual dynamical systems but of the parameter space of the class of dynamical systems considered.
I will discuss various renormalization schemes in real and complex discrete dynamical systems and their applications.
## Siegel capture polynomials in parameter spaces
### When
April 19, 2019 | 2:30 - 3:30 p.m.
### Speaker
Dr. Lex Oversteegen (joint with Alexander Blokh, Arnaud Cheritat, Toulouse, Lex Oversteegen, and Vladlen Timorin, Moscow)
### Abstract
We consider the set of cubic polynomials $f$ with a marked fixed point. If $f$ has a Siegel disk at the marked fixed point, and if this disk contains an eventual image of a critical point, we call $f$ a \emph{IS-capture polynomial}. We study the location of IS-capture polynomials in the parameter space of all marked cubic polynomials modulo affine conjugacy. In particular, it is shown that any IS-capture is on the boundary of a unique bounded hyperbolic component determined by the rational lamination of the map. We also relate IS-captures to the cubic Principal Hyperbolic Domain and its closure (by definition, the \emph{cubic Principal Hyperbolic Domain} consists of cubic hyperbolic polynomials with Jordan curve Julia sets).
## Slices of parameter space of cubic polynomials
### When
April 12, 2019 | 2:30 - 3:30 p.m.
### Speaker
Dr. Alexander Blokh (joint with Lex Oversteegen and Vladlen Timorin, Moscow)
### Abstract
In this paper, we study slices of the parameter space of cubic polynomials, up to affine conjugacy, given by a fixed value of the multiplier at a non-repelling fixed point. In particular, we study the location of the \emph{main cubioid} in this parameter space. The \emph{main cubioid} is the set of affine conjugacy classes of complex cubic polynomials that have certain dynamical properties generalizing those of polynomials $z^2+c$ for $c$ in the filled main cardioid.
## A class of Schrodinger operators with convergent perturbation series
### When
April 5, 2019 | 2:30 - 3:30 p.m.
### Speaker
Dr. Ilya Kachkovskiy, Michigan State University
### Abstract
Rayleigh-Schrodinger perturbation series is one of the main tools of analyzing eigenvalues and eigenvectors of operators in quantum mechanics. The first part of the talk is expository and should be accessible to students with working knowledge of linear algebra: I will explain a way of representing all terms of the series in terms of graphs with certain structure (similar representations appear in physical literature in various forms). The second part of talk is based on joint work in progress with L. Parnovski and R. Shterenberg. We show that, for a class of lattice Schrodinger operators with unbounded quasiperiodic potentials, one can establish convergence of these series (which is surprising because the eigenvalues are not isolated). The proof is based on the careful analysis of the graphical structure of terms in order to identify cancellations between terms that contain small denominators. The result implies Anderson localization for a class of Maryland-type models on higher-dimensional lattices.
## The story of the little ell one norm and its friends
### When
March 29, 2019 | 2:30 - 3:30 p.m.
### Speaker
Dr. Carmeliza Navasca
### Abstract
The popularity of sparse ell one norm optimization problem was due to Emmanuel Candes and Terrence Tao via compressed sensing. I will start by introducing the little ell one norm and its minimization. Then, I will describe how and why these sparse optimization problems are useful in solving today’s challenging problems in data science and machine learning. Numerical examples in foreground and background separation in surveillance videos, matrix and tensor completion as well as deep neural network for image classification are included. In this talk, one can observe the interplay of (multi)linear algebra, optimization and numerical analysis with applications in computer science.
This is joint work with Xiaofei Wang (former postdoc at UAB, now Prof at Normal University, China), Ramin Karim Goudarzi, Fatou Sanogo, Ali Fry (former Fast-Track) and Da Yan (CS Prof at UAB).
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# rstudio::conf 2020 Review: Part 2
All talks can be found here: https://resources.rstudio.com/rstudio-conf-2020. I’ve picked 30 talks in total, so will split them into 3 parts with 10 talks each.
Part 1 is here
Part 3 is here
Short and to the point overview of current lay of the land when it comes to TensorFlow bindings in R. There is a number of packages that are covering various areas of TF ecosystem with even more packages planned for release in a near future. One interesting question about adding support for PyTorch in the future and it seems like it’s not a priority at the moment and unlikely to come from RStudio.
Entertaining talk about how you can use tracking data for clustering of NFL plays. The most interesting part for me was more about the fact that actual tools that they’ve used come almost directly from R4DS book, so it kinda validates the approach that RStudio at large has been doing - breed adoption of R tools through concerted effort of producing high-quality education materials. gganimate also had a cameo showing how powerful animation can be.
Another whirlwind of an update about Spark and MlFlow from one of the main contributor/developer of the package. It’s always good to see that pace of the project is actually speeding up with new extensions and bigger and bigger scope.
If you ever wanted to launch Jupyter Notebook in RStudio Server Pro - now you can! Personally, I dislike Jupyter Notebooks quite a lot, but obviously not everyone holds the same position, so it makes sense to have it available. It’s also interesting to see an integration with RStudio Connect where you can easily publish your Jupyter Notebooks and share it with wider organization.
An ode to RMarkdown. As I’m writing this in markdown that eventually will be published to a website running blogdown, I’d say I’m in the same boat, but if you ever need convincing that RMarkdown is the way - watch this talk.
If you want to use dplyr with data.table then there is dtplyr. But what if you want to use tidyr with data.table? Then there is a tidyfast package that implements nesting and unnesting using data.table as a backend. As is often the case, using data.table allows you to improve both speed and memory consumption, so if you are finding yourself struggling on either of these fronts, then data.table can be a way to go.
Deeply thought out talk about how to repay technical debt in a most sustainable way possible. Whole talk is definitely worth watching, but the main idea is that as a person writing code you should take responsibility to create delightful code. How to define what “delightful” means is not easy, but Gordon gives bunch of helpful tips to do so. It is also another talk that is not talking about R in any way since lessons learned apply to literally every single person who ever opened text editor and wrote even a single line of code. It is actually quite cool to see that there are more and more talks that talk about this topic at rstudio::conf since R has a (sometimes deserved) reputation of language that produces difficult to maintain code.
If you have anxiety about running live demos during presentation, then you probably should not watch this presentation. Yihui showed how same document with minimal modifications can be used in 14 different output formats live on stage.
I think, this talk can be summarized with this:
Except instead of identifying a bird, we are adding (gasp!) text formatting to ggplot's. It’s funny how seemingly innocuous things need to have so much effort put into them, but here we are. You can now put this: “Part of this is in italics” in your ggplot labels.
Programming with ggplot2 is probably not that different from programming in R in general. One obvious difference is that visual differences are more difficult to detect, but this where package like vdiffr can help you.
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# In Hoffmann bromamide degradation reaction, find the number of moles of $NaOH$ and $B{r_2}$ used to produce one mole of amine.A) Four moles of $NaOH$ and two moles of $B{r_2}$ B) Two moles of $NaOH$ and two moles of $B{r_2}$ C) Four moles of $NaOH$ and one moles of $B{r_2}$ D) One moles of $NaOH$ and one moles of $B{r_2}$
Verified
119.4k+ views
Hint: Hoffmann bromamide degradation reaction, as the name suggests is the degradation of an amide by treating it with bromine in an aqueous or ethanolic solution of sodium hydroxide to form a primary amine. By finding out the equation for this reaction, we can find the number of moles of $NaOH$ and $B{r_2}$ used.
$RCON{H_2} + B{r_2} + 4NaOH \to RN{H_2} + N{a_2}C{O_3} + 2NaBr + 2{H_2}O$ where R is taken as a general aliphatic or aromatic organic compound.
From the above equation, it is clear to us that four moles of $NaOH$ and one mole of Bromine are used to produce one mole of amine in Hoffmann bromamide degradation reaction. Therefore the answer is four moles of Sodium hydroxide and one mole of Bromine are required.
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# Largest eigenvalues of sparse inhomogeneous Erd\H{o}s-R\'enyi graphs
Abstract : We consider inhomogeneous Erd\H{o}s-R\'enyi graphs. We suppose that the maximal mean degree $d$ satisfies $d \ll \log n$. We characterize the asymptotic behavior of the $n^{1 - o(1)}$ largest eigenvalues of the adjacency matrix and its centred version. We prove that these extreme eigenvalues are governed at first order by the largest degrees and, for the adjacency matrix, by the nonzero eigenvalues of the expectation matrix. Our results show that the extreme eigenvalues exhibit a novel behaviour which in particular rules out their convergence to a nondegenerate point process. Together with the companion paper [3], where we analyse the extreme eigenvalues in the complementary regime $d \gg \log n$, this establishes a crossover in the behaviour of the extreme eigenvalues around $d \sim \log n$. Our proof relies on a new tail estimate for the Poisson approximation of an inhomogeneous sum of independent Bernoulli random variables, as well as on an estimate on the operator norm of a pruned graph due to Le, Levina, and Vershynin.
Type de document :
Pré-publication, Document de travail
MAP5 2017-17. 2017
Domaine :
https://hal.archives-ouvertes.fr/hal-01528790
Contributeur : Florent Benaych-Georges <>
Soumis le : lundi 29 mai 2017 - 16:59:20
Dernière modification le : mardi 10 octobre 2017 - 11:22:05
### Identifiants
• HAL Id : hal-01528790, version 1
• ARXIV : 1704.02953
### Citation
Florent Benaych-Georges, Charles Bordenave, Antti Knowles. Largest eigenvalues of sparse inhomogeneous Erd\H{o}s-R\'enyi graphs. MAP5 2017-17. 2017. 〈hal-01528790〉
### Métriques
Consultations de la notice
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# Surface¶
This module contains classes describing different surfaces.
A surface is required by both the radiation and the convective models used inside the RCE simulations, and if you don’t set it up default will be a SlabOcean.
Example
Create a surface model, e.g. SlabOcean, and use it in an RCE simulation:
>>> import konrad
>>> surface_temperature_start = ...
>>> surface = konrad.surface.SlabOcean(
>>> temperature=surface_temperature_start)
>>> rce = konrad.RCE(atmosphere=..., surface=surface)
>>> rce.run()
>>> surface_temperature_end = surface['temperature'][-1]
Surface(*args, **kwargs) Abstract base class to define requirements for surface models. FixedTemperature(*args, **kwargs) Surface model with fixed temperature. SlabOcean(*args, **kwargs) Surface model with adjustable temperature.
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# Solids of revolutions and their volumes?
I am currently self-teaching myself some calculus stuff and I am a bit confused about all these methods to find the volumes given a function rotated along the $y$- or $x$-axis? So far I have come across so many videos with different method names which is what confuses me.
Is the Ring Method = Washer = Disc method? I know there is also the shell method, but other than that are there only two methods to finding the volume?
• There are two basic methods. Here's an exercise for you: take the disk of unit radius centered at $(1,1)$, and rotate it against whichever axis you like. What are the volume and surface area of the figure thus obtained ? – Lucian Feb 7 '15 at 7:36
• A washer is just a disk with a concentric hole. It's basically the same method. – David K Mar 9 '15 at 5:48
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Reason for particle decay
1. Jan 30, 2013
why is that particles such as the tau muon have a short lifespan and why is it that particles decay into other partcles? furthermore, what are the process that occur in particle decay?
2. Jan 30, 2013
Staff: Mentor
Physics cannot explain "why" - it can just describe the observations. Tau particles have a possible decay, and it is possible to calculate their lifetime (based on other values, like the muon lifetime), but that does not answer why they decay.
Concerning "how": Well, it can be described as interaction with the W boson.
3. Jan 30, 2013
AbsoluteZer0
In the standard model there are several fundamental forces of nature:
Strong Nuclear Force
-Responsible for binding quarks together as well as protons and neutrons
Weak Nuclear Force
-Responsible for all radioactive decay
Electromagnetic Force
-Occurs between everything that has a charge.
**Gravity has been debated over the years
Each of these forces has a corresponding particle known as a gauge boson that is responsible for carrying out those forces. The Strong Nuclear force is carried out by the Gluon, the Weak Nuclear force is carried out by the W and Z bosons (the W boson has positively charged and negatively charged variants,) and the Electromagnetic force is carried out by the Photon.
In the case of radioactive decay, all radioactive decay occurs as a result of the weak nuclear force. The weak nuclear force is important as it is the only known force that has the potential to change the flavor (characteristics) of a quark. Take, for example, the decay of a proton into a neutron.
A proton is composed of two up quarks and a down quark and a neutron is composed of two down quarks and an up quark.
p → n + w+
The w+ boson then decays into a positron e+ and an electron anti neutrino ̅νe.
So: p → n + e+ + ̅νe.
The positron and antineutrino conserve charge. As a result of the interaction with the w+ boson, one of the up quarks changes into a down quark.
http://en.wikipedia.org/wiki/Standard_Model
Last edited: Jan 30, 2013
4. Jan 30, 2013
Staff: Mentor
Not all, just beta decays.
Alpha decays, gamma "decays", proton emission, neutron emission, cluster decays and fission are independent of the weak force.
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# Spivak Chapter 2, problems 27 (and 28)
To be honest, I have no idea how to even start this problem. I'm sorry I don't have any work to show, but I'm just at a blank. Help?
Chapter 2: Problem 27:
"University B, once boasted 17 tenured professors of mathematics. Tradition prescribed that at their weekly luncheon meeting, faithfully attended by all 17, any members who had discovered an error in their published work should make an announcement of this fact, and propmptly resign. Such an announcement had never actually been made, because no professor was aware of any errors in her or his work. This is not to say that no errors existed, however. In fact, over the years, in the work of every member of the department at least one error had been found, by some other member of the department. This error had been mentioned to all other members of the department, but the actual author of the error had been kept ignorant of the fact, to forestall any resignations. One fateful year, the department was augmented by a visitor from another university, one Prof.X, who had come with hopes of being offered a permanent position at the end of the academic year. Naturally, he was apprised, by various members of the department, of the published errors which had been discovered. When the hoped-for appointment failed to materialize, Prof. X obtained his revenge at the last luncheon of the year. "I have enjoyed my visit here very much", he said, "but I feel that there is one thing that I have to tell you. At least one of you has published an incorrect result, which has been discovered by others in the department." What happened the next year?"
Chapter 2: Problem 28:
After figuring out, or looking up, the answer to Problem 27, consider the following: Each member of the department already knew that Prof.X asserted, so how could his saying it change anything?
-
Could you write the problem or post a link to it? – user10444 Jan 8 '13 at 16:39
@Lob, not all of us have the book, and even if they did it would be nice of you to spare us the effort of getting off the couch. – nbubis Jan 8 '13 at 16:41
@Lob: Welcome to MSE! There are people who do not have easy access to the reference you cite and it is great that you cite the reference, however, can you write out the problem. Also, MSE typically only want one question per posting in case users are searching. Is this homework? If so, please tag it as such. Regards – Amzoti Jan 8 '13 at 16:41
@Freddy It presuposes a lot of things about human nature that don't belong to mathematics... If we apply very specific and restrictive rules, it could be reduced to a much simpler problem. From my point of view, it's just a way to make something simple very complex. – MyUserIsThis Jan 8 '13 at 18:39
@Ferfer93 It is a mathematics puzzle. It is not meant to suggest a professor would actually resign if they learn about an error in their paper. For the sake of the problem, if the professor learns about the error they resign. – Danikar Jan 8 '13 at 18:44
## 1 Answer
First simplify the problem to only 2 professors, call them Prof. A and Prof. B (instead of 17).
On the next meeting after Professor X's statement. Prof. A will expect Prof. B to resign since Prof. A knows about Prof. B's error. When Prof. B does not resign, Prof. A will know it is because Prof. B is aware of an error of Prof. A's. Therefore, Prof. A knows about his error and must resign on the next meeting. Similarly Prof. B will have found out his error and will also resign.
Now think about how this works for 3 professors. Then you can generalize it to n professors and use it for your 17 professor problem.
If a professor knows about 0 errors, he must resign as soon as Professor X makes his statement because he would know the error was his.
If a professor knows exactly $k$ errors, and no one has resigned before the $k$th meeting after Professor X's statement, then he knows all members of the department know about at least $k$ errors which are not their own. So the professor now knows there must be at least $k + 1$ errors that everyone, except the error maker, know about. Since he only knows about $k$ errors, one of the errors must be his own and he must resign.
In the case where there are 17 professors where all professors know about exactly 16 errors. All the professors will resign on the 16th meeting after Professor X made his statement.
-
Oh... I think I get it now. But how do I go about answering 28? – Lob Jan 8 '13 at 17:33
Before Professor X said anything, each professor knew nothing about what the other professors knew. After Professor X said something, then each professor knew that the other professors knew about at least 1 error. And subsequently after each meeting the professors gain more information when the other professor's do not resign. – Danikar Jan 8 '13 at 17:38
But I thought each professor mentions the error to everyone except the guy who made the error? "his error had been mentioned to all other members of the department" or am I interpreting that wrong? – Lob Jan 8 '13 at 18:18
You are correct. However, Professor X's statement provides more information about what the others know. For example in the 3 professor problem from A's perspective. A knows errors for B and C. A knows B knows C's error, and A knows C knows B's error. So A knows no one will resign immediately. However, once C does not resign, A knows that B knows that C knows some error. So unless B knows two errors, he knows C knows an error about him. Thus he must resign. If he does not resign, then A knows B knows 2 errors. And since B wouldn't know an error about himself, B must know an error about A. – Danikar Jan 8 '13 at 18:33
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# [OS X TeX] Float Placement
George LGhio gghi at bordernet.com.au
Sat May 17 08:30:04 CEST 2008
Perhaps I should have pointed out that I use:
\begin{figure}[htbp]
\centering
\includegraphics[width=120mm,height=90mm]{Staff52.jpg}
\caption{Staff 1952 \tiny{Goulburnia}}
\end{figure}\\
George
On 17 May 2008, at 12:58 PM, Richard J Benish wrote:
> I have a float (a pdf figure) that takes up about two thirds of the
> height of a two column page. When I place it in the desired column,
> however, text above and below the float disappears, leaving a lot of
> unwanted blank space.
>
> In the "LaTeX Companion" I see that commands such as \intextsep may
> correct the problem, but I don't find any specific examples, so it's
> not clear exactly what to enter and where. The commands that result in
> the behavior described above are as follows:
>
>
> \begin{figure}[htbp]
> \begin{center}
> \includegraphics[width=0.48\textwidth]{RelSimGPS-Box-1-May-16-08.pdf}
> \label{default}
> \end{center}
> \end{figure}
>
>
> Any suggestions as to exactly how to use the \intextsep command or
> others to fix this problem?
>
> Muchas Gracias.
>
> Richard Benish
>
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GUTS & Inflation
1. Aug 19, 2009
Jim
Can someone please clarify if the energy scales of Inflation & GUTs are identical,
or model-dependent ? One typically sees ~10^15 Gev to 2x10^16 Gev in the literature,
which is a small variance, but its not clear if there are `standard values'.
I am also curious if one can have inflation without GUTs ?
2. Aug 25, 2009
javierR
The scales of inflation and GUTs are independent, so yes, one can have inflation without GUTs. And on the flip side, GUTs don't automatically incorporate inflation. The usually quoted characteristic energy scale of inflation 10^15-10^16 Gev is based on observation. Unlike inflation, GUTs are hypothetical, and the energy scales associated with them are model-dependent. It just so happens that "standard" field theory GUTs require a scale of 10^16 Gev. But there are certainly GUTs, e.g. in theories with at least one extra dimension, in which the characteristic scale is of a different order of magnitude.
3. Aug 25, 2009
Haelfix
Keep in mind, historically, inflation was partially invented to rescue GUT theories in cosmology. GUT theories are amongst the most widely held beliefs (that we can't prove) in the HEP community. They're almost taken for granted.
The problem is many typical models incorporate a preponderous of particles like magnetic monopoles and other various topological defects. Roughly, they should be everywhere, b/c the big bang would copiously produce them and that is flagrantly in violation of observation.
Enter an inflationary epoch somewhere around the GUT scale (typically a little bit higher energy), which dilutes the abundance to observational limits.
4. Aug 26, 2009
friend
Just a thought, particles are created near horizons, e.g. black holes. But acceleration also creates horizons, i.e. Unruh effect. So if space is expanding exponentially (inflation), then every point in space becomes an horizon due to acceleration. So perhaps it is that inflation is what is responsible for the original particles to begin with, and therefore connected in some way to GUT's
Last edited: Aug 26, 2009
5. Aug 31, 2009
Jim
Thanx all for your quik responses !
Haelfix: Agree about the historical correlation. Running with the mSSM value of 2E16 Gev
for the GUT group to split into SU(3) and SU(2)xU(1), this occurs considerably prior to reheating at ~ 2E15 Gev, when FRW evolution kicks in again. The time scales are approx.,
Trh ~ 100Tgut. Clearly, there is a temporal sequence of events here.
In terms of chicken v. egg, accd'g to Guth, inflation began ~ 10^-37 sec. mSSM GUT energy corresponds to a time scale of about 10^-39 sec, which strongly suggests a causal relation, with the GUT symmetry breaking causing the phase transition driving inflation.
Indeed, it seems more aesthetic to have the GUT symmetry breaking initiate inflation, since GUTs correspond to ~ 100-1000 Planck lengths, whereas inflation ranges up into the macroscopic domain ~ centimeters.
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# Kinetic energy subgrid-scale model
(Difference between revisions)
Revision as of 23:27, 18 September 2005 (view source)Zxaar (Talk | contribs)← Older edit Revision as of 23:43, 18 September 2005 (view source)Zxaar (Talk | contribs) Newer edit → Line 1: Line 1: - $k_{\rm sgs} = \frac{1}{2}\left(\overline{u_k^2} - \overline{u}_k^2 \right)$ + The subgrid-scale kinetic energy is defined as
+ :$k_{\rm sgs} = \frac{1}{2}\left(\overline{u_k^2} - \overline{u}_k^2 \right)$ + + + The subgrid-scale stress can then be written as
+ $\tau_{ij} - \frac{2}{3} k_{\rm sgs} \delta_{ij} =-2 C_k k_{\rm sgs}^{1/2} \Delta_f \overline{S}_{ij}$
+ this gives us the transport equation for subgrid-scale kinetic energy
+ $\frac{\partial \overline k_{\rm sgs}}{\partial t} + \frac{\partial \overline u_{j} \overline k_{sgs}} {\partial x_{j}} = - \tau_{ij} \frac{\partial \overline u_{i}}{\partial x_{j}} - C_{\varepsilon} \frac{k_{\rm sgs}^{3/2}}{\Delta_f} + \frac{\partial}{\partial x_{j}} \left( \frac{\mu_t}{\sigma_k} \frac{\partial k_{\rm sgs}}{\partial x_{j}} \right)$ + + + + The subgrid-scale eddy viscosity,$\mu_{t}$, is computed using $k_{\rm sgs}$ as + + + $\mu_{t} = C_k k_{\rm sgs}^{1/2} \Delta_f$ + + Where the filter-size computed from:
+ $\Delta_f = V^{1/3}$
## Revision as of 23:43, 18 September 2005
The subgrid-scale kinetic energy is defined as
$k_{\rm sgs} = \frac{1}{2}\left(\overline{u_k^2} - \overline{u}_k^2 \right)$
The subgrid-scale stress can then be written as
$\tau_{ij} - \frac{2}{3} k_{\rm sgs} \delta_{ij} =-2 C_k k_{\rm sgs}^{1/2} \Delta_f \overline{S}_{ij}$
this gives us the transport equation for subgrid-scale kinetic energy
$\frac{\partial \overline k_{\rm sgs}}{\partial t} + \frac{\partial \overline u_{j} \overline k_{sgs}} {\partial x_{j}} = - \tau_{ij} \frac{\partial \overline u_{i}}{\partial x_{j}} - C_{\varepsilon} \frac{k_{\rm sgs}^{3/2}}{\Delta_f} + \frac{\partial}{\partial x_{j}} \left( \frac{\mu_t}{\sigma_k} \frac{\partial k_{\rm sgs}}{\partial x_{j}} \right)$
The subgrid-scale eddy viscosity,$\mu_{t}$, is computed using $k_{\rm sgs}$ as
$\mu_{t} = C_k k_{\rm sgs}^{1/2} \Delta_f$
Where the filter-size computed from:
$\Delta_f = V^{1/3}$
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# Modeling Polynomials
For the Algebra tiles red are positive and everything else are negative.
$(x-1)^2$
$x^2-2x+1$
$(x+1)^2$
$x^2+2x+1$
$(x-1)(x+1)$
$x^2-1$
The fourth question can not be represent by algebra tiles but by the rules I can fond out the simplist form of the equation.
$(x-1)^3$
$x^3-3x-1$
## One thought on “Modeling Polynomials”
1. emcarthur says:
Just a note the traditionally the red tiles are used as negative. Use Pascals Triangle to expand (x-1)^3 and check your expansion here.
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# American Institute of Mathematical Sciences
July 1998, 4(3): 431-444. doi: 10.3934/dcds.1998.4.431
## On the initial boundary value problem for the damped Boussinesq equation
Received March 1996 Revised April 1997 Published April 1998
The first initial-boundary value problem for the damped Boussinesq equation $u_{t t}-2bu_{t x x}=-\alpha u_{x x x x}+u_{x x}+\beta (u^2)_{x x}, x\in (0,\pi ),\quad t>0,$ with $\alpha, b=const>0,\quad \beta =const\in R^1,$ is considered with small initial data. For the most interesting case $\alpha >b^2$ corresponding to an infinite number of damped oscillations its solution is constructed in the form of a Fourier series which coefficients in their own turn are represented as series in small parameter present in the initial conditions. The solution of the corresponding problem for the classical Boussinesq equation on $[0,T],\quad T<+\infty,$ is obtained by means of passing to the limit $b\rightarrow +0.$ Long-time asymptotics of the solution in question is calculated which shows the presence of the damped oscillations decaying exponentially in time. This is in contrast with the long time behavior of the solution of the periodic problem studied in [30] which major term increases linearly with time.
Citation: Vladimir V. Varlamov. On the initial boundary value problem for the damped Boussinesq equation. Discrete & Continuous Dynamical Systems - A, 1998, 4 (3) : 431-444. doi: 10.3934/dcds.1998.4.431
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2019 Impact Factor: 1.338
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# 2.5.2: Conversion between Degrees and Radians
Most people are familiar with measuring angles in degrees. It is easy to picture angles like $$30^{\circ}$$, $$45^{\circ}$$ or $$90^{\circ}$$ and the fact that $$360^{\circ}$$ makes up an entire circle. Over 2000 years ago the Babylonians used a base 60 number system and divided up a circle into 360 equal parts. This became the standard and it is how most people think of angles today.
However, there are many units with which to measure angles. For example, the gradian was invented along with the metric system and it divides a circle into 400 equal parts. The sizes of these different units are very arbitrary.
A radian is a unit of measuring angles that is based on the properties of circles. This makes it more meaningful than gradians or degrees. How many radians make up a circle?
radian is defined to be the central angle where the subtended arc length is the same length as the radius.
Another way to think about radians is through the circumference of a circle. The circumference of a circle with radius $$r$$ is $$2\pi r$$. Just over six radii (exactly $$2\pi$$ radii) would stretch around any circle.
To define a radian in terms of degrees, equate a circle measured in degrees to a circle measured in radians.
$$360 \text{ degrees}=2\pi \text{ radians}$$, so $$\dfrac{180}{\pi} \text{ degrees}=1 \text{ radian}$$
Alternatively; $$360 \text{degrees}=2\pi$$ radians, so 1 degree=$$\dfrac{\pi}{180}$$ radians
The conversion factor to convert degrees to radians is: $$\dfrac{\pi}{180^{\circ}}$$
The conversion factor to convert radians to degrees is: $$\dfrac{180^{\circ} }{\pi}$$
If an angle has no units, it is assumed to be in radians.
If you were to convert $$150^{\circ}$$ into radians, you would multiply $$150^{\circ}$$ by the correct conversion factor. You would get:
$$150^{\circ} \cdot \dfrac{\pi}{180^{\circ}} =\dfrac{15\pi }{18}=\dfrac{5\pi }{6} \text{ radians}$$
You can check your work by making sure the degree units appear on both the numerator and denominator.
If you were to convert $$\dfrac{\pi }{6}$$ radians into degrees, you would multiply \pi 6 by the correct conversion factor. You would get $$\dfrac{\pi }{6}\cdot \dfrac{180^{\circ} }{\pi }=\dfrac{180^{\circ} }{6}=30^{\circ}$$
Notice \pi appears in both the numerator and denominator and \pi \pi =1.
Example $$\PageIndex{1}$$
Solution
Exactly $$2\pi$$ radians describe a circular arc. This is because $$2\pi$$ radii wrap around the circumference of any circle.
Example $$\PageIndex{2}$$
Convert $$(6\pi )^{\circ}$$ into radians.
Solution
Don’t be fooled just because this has $$\pi$$. This number is about $$19^{\circ}$$.
$$(6\pi )^{\circ} \cdot \dfrac{\pi}{180^{\circ} }=\dfrac{6\pi^2}{180}=\dfrac{\pi^2}{3}$$
It is very unusual to ever have a $$\dfrac{\pi}{2}$$ term, but it can happen.
Example $$\PageIndex{3}$$
Convert $$\dfrac{5\pi }{6}$$ into degrees.
Solution
$$\dfrac{5\pi }{6} \cdot \dfrac{180^{\circ} }{\pi }=\dfrac{5\cdot 30^{\circ} }{1}=150^{\circ}$$
Example $$\PageIndex{4}$$
Convert $$210^{\circ}$$ into radians.
Solution
$$210^{\circ} \cdot \dfrac{\pi}{180^{\circ} }=\dfrac{7\cdot 30\cdot \pi }{6\cdot 30}=\dfrac{7 \pi}{6}$$
Example $$\PageIndex{5}$$
Draw a $$\dfrac{\pi}{2}$$ angle by first drawing a $$2\pi$$ angle, halving it and halving the result. Recall that $$\dfrac{\pi}{2}=90^{\circ}$$.
Solution
### Review
Find the radian measure of each angle.
1. $$120^{\circ}$$
2. $$300^{\circ}$$
3. $$90^{\circ}$$
4. $$330^{\circ}$$
5. $$270^{\circ}$$
6. $$45^{\circ}$$
7. $$(5\pi )^{\circ}$$
Find the degree measure of each angle.
8. $$\dfrac{7 \pi}{6}$$
9. $$\dfrac{5 \pi}{4}$$
10. $$\dfrac{3 \pi}{2}$$
11. $$\dfrac{5\pi }{3}$$
12. $$\pi$$
13. $$\dfrac{\pi }{6}$$
14. $$3$$
15. Explain why if you are given an angle in degrees and you multiply it by $$\dfrac{\pi}{180}$$ you will get the same angle in radians.
To see the Review answers, open this PDF file and look for section 4.1.
## Vocabulary
Term Definition
subtended arc A subtended arc is the part of the circle in between the two rays that make the central angle.
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# Book IV, Prosa 5
Providence rules Fortune
Page 125
'That is true,' I said; 'but it is your kind office to unravel the causes
of hidden matters, and explain reasons now veiled in darkness; wherefore I
beg of you, put forth your decree and expound all to me, since this wonder
most deeply stirs my mind.'
Then said she, smiling, 'Your question calls me to the greatest of all
these matters, and a full answer thereto is well-nigh impossible. For this
is its kind: if one doubt be cut away, innumerable others arise, as the
Hydras heads; and there can be no limit unless a man restrains them by the
most quick fire of the mind. For herein lie the questions of the directness
of Providence, the course of Fate, chances which cannot be foreseen,
knowledge, divine predestination, and freedom of judgment. You can judge
for yourself the weight of these questions. But since it is a part of your
treatment to know some of these, I will attempt to make some advantage
therefrom, though we are penned in by our narrow space of time. But
Page 126
if you enjoy the delights of song, you must wait a while for that pleasure,
while I weave together for you the chain of reasons.'
'As you will,' said I. Then, as though beginning afresh, she spake thus:
'The engendering of all things, the whole advance of all changing natures,
and every motion and progress in the world, draw their causes, their order,
and their forms from the allotment of the unchanging mind of God, which
lays manifold restrictions on all action from the calm fortress of its own
directness. Such restrictions are called Providence when they can be seen to
lie in the very simplicity of divine understanding; but they were called
Fate in old times when they were viewed with reference to the objects which
they moved or arranged. It will easily be understood that these two are
very different if the mind examines the force of each. For Providence is
the very divine reason which arranges all things, and rests with the
supreme disposer of all; while Fate is that ordering which is a part of all
changeable things, and by means of which Providence binds all things
together in their own order. Providence embraces all things equally,
however different they may be, even however infinite: when they are
assigned to their own places, forms, and times, Fate sets them in an
orderly motion; so that this development of the temporal order, unified in
the intelligence of the mind of God, is Providence.
Page 127
The working of this unified development in time is called Fate. These are
different, but the one hangs upon the other. For this order, which is ruled
by Fate, emanates from the directness of Providence. Just as when a
craftsman perceives in his mind the form of the object he would make, he
sets his working power in motion, and brings through the order of time that
which he had seen directly and ready present to his mind. So by Providence
does God dispose all that is to be done, each thing by itself and
unchangeably; while these same things which Providence has arranged are
worked out by Fate in many ways and in time. Whether, therefore, Fate works
by the aid of the divine spirits which serve Providence, or whether it
works by the aid of the soul, or of all nature, or the motions of the stars
in heaven, or the powers of angels, or the manifold skill of other spirits,
whether the course of Fate is bound together by any or all of these, one
thing is certain, namely that Providence is the one unchangeable direct
power which gives form to all things which are to come to pass, while Fate
is the changing bond, the temporal order of those things which are arranged
to come to pass by the direct disposition of God. Wherefore everything
which is subject to Fate is also subject to Providence, to which Fate is
itself subject. But there are things which, though beneath Providence, are
above the course of Fate. Those things are they which are immovably set
nearest the
Page 128
primary divinity, and are there beyond the course of the movement of Fate.
As in the case of spheres moving round the same axis, that which is nearest
the centre approaches most nearly the simple motion of the centre, and is
itself, as it were, an axis around which turn those which are set outside
it. That sphere which is outside all turns through a greater circuit, and
fulfils a longer course in proportion as it is farther from the central
axis; and if it be joined or connect itself with that centre, it is drawn
into the direct motion thereof, and no longer strays or strives to turn
away. In like manner, that which goes farther from the primary
intelligence, is bound the more by the ties of Fate, and the nearer it
approaches the axis of all, the more free it is from Fate. But that which
clings without movement to the firm intellect above, surpasses altogether
the bond of Fate. As, therefore, reasoning is to understanding; as that
which becomes is to that which is; as time is to eternity; as the
circumference is to the centre: so is the changing course of Fate to the
immovable directness of Providence. That course of Fate moves the heavens
and the stars, moderates the first principles in their turns, and alters
their forms by balanced interchangings. The same course renews all things
that are born and wither away by like advances of offspring and seed. It
constrains, too, the actions and fortunes of men by an unbreakable chain of
causes: and these causes must be unchangeable, as they
Page 129
proceed from the beginnings of an unchanging Providence. Thus is the world
governed for the best if a directness, which rests in the intelligence of
God, puts forth an order of causes which may not swerve. This order
restrains by its own unchangeableness changeable things, which might
otherwise run hither and thither at random. Wherefore in disposing the
universe this limitation directs all for good, though to you who are not
strong enough to comprehend the whole order, all seems confusion and
disorder. Naught is there that comes to pass for the sake of evil, or due
to wicked men, of whom it has been abundantly shewn that they seek the
good, but misleading error turns them from the right course; for never does
the true order, which comes forth from the centre of the highest good, turn
any man aside from the right beginning.
'But you will ask, "What more unjust confusion could exist than that good
men should sometimes enjoy prosperity, sometimes suffer adversity, and that
the bad too should sometimes receive what they desire, sometimes what they
hate?" Are then men possessed of such infallible minds that they, whom
they consider honest or dishonest, must necessarily be what they are held
to be? No, in these matters human judgment is at variance with itself, and
those who are held by some to be worthy of reward, are by others held
worthy of punishment. But let us grant that a man could discern between
Page 130
he therefore know the inmost feelings of the soul, as a doctor can learn a
bodys temperature? For it is no less a wonder to the ignorant why sweet
things suit one sound body, while bitter things suit another; or why some
sick people are aided by gentle draughts, others by sharp and bitter ones.
But a doctor does not wonder at such things, for he knows the ways and
constitutions of health and sickness. And what is the health of the soul
but virtue? and what the sickness, but vice? And who is the preserver of
the good and banisher of the evil, who but God, the guardian and healer of
minds? God looks forth from the high watch-tower of His Providence, He
sees what suits each man, and applies to him that which suits him. Hence
then comes that conspicuous cause of wonder in the order of Fate, when a
wise man does that which amazes the ignorant. For, to glance at the depth
of Gods works with so few words as human reason is capable of
comprehending, I say that what you think to be most fair and most conducive
to justices preservation, that appears different to an all-seeing
Providence. Has not our fellow-philosopher Lucan told us how the
conquering cause did please the gods, but the conquered, Cato? What then
surprises you when done on this
Page 131
earth, is the true-guided order of things; it is your opinion which is
perverted and confused. But if there is any one whose life is so good that
divine and human estimates of him agree, yet he must be uncertain in the
strength of his mind; if any adversity befall him, it may always be that he
will cease to preserve his innocence, by which he found that he could not
preserve his good fortune. Thus then a wise dispensation spares a man who
might be made worse by adversity, lest he should suffer when it is not good
for him to be oppressed. Another may be perfected in all virtues, wholly
conscientious, and very near to God: Providence holds that it is not right
such an one should receive any adversity, so that it allows him to be
troubled not even by bodily diseases. As a better man than I has said,
"The powers of virtues build up the body of a good man." It often happens
that the duty of a supreme authority is assigned to good men for the
purpose of pruning the insolent growth of wickedness. To some, Providence
grants a mingled store of good and bad, according to the nature of their
minds. Some she treats bitterly, lest they grow too exuberant with long
Page 132
continued good fortune; others she allows to be harassed by hardships that
the virtues of their minds should be strengthened by the habit and exercise
of patience. Some have too great a fear of sufferings which they can bear;
others have too great contempt for those which they cannot bear: these she
leads on by troubles to make trial of themselves. Some have brought a name
to be honoured for all time at the price of a glorious death. Some by
shewing themselves undefeated by punishment, have left a proof to others
that virtue may be invincible by evil. What doubt can there be of how
rightly such things are disposed, and that they are for the good of those
whom we see them befall? The other point too arises from like causes, that
sometimes sorrows, sometimes the fulfilment of their desires, falls to the
wicked. As concerns the sorrows, no one is surprised, because all agree
that they deserve ill. Their punishments serve both to deter others from
crime by fear, and also to amend the lives of those who undergo them; their
happiness, on the other hand, serves as a proof to good men of how they
should regard good fortune of this nature, which they see often attends
upon the dishonest. And another thing seems to me to be well arranged: the
nature of a man may be so headstrong and rough that lack of wealth may stir
him to crime more readily than restrain him; for the disease of such an one
Providence prescribes a remedy of stores of patrimony: he may see
Page 133
that his conscience is befouled by sin, he may take account with himself of
his fortune, and will perhaps fear lest the loss of this property, of which
he enjoys the use, may bring unhappiness. Wherefore he will change his
ways, and leave off from ill-doing so long as he fears the loss of his
fortune. Again, good fortune, unworthily improved, has flung some into
ruin. To some the right of punishing is committed that they may use it for
the exercise and trial of the good, and the punishment of evil men. And
just as there is no league between good and bad men, so also the bad cannot
either agree among themselves: nay, with their vices tearing their own
consciences asunder, they cannot agree with themselves, and do often
perform acts which, when done, they perceive that they should not have
done. Wherefore high Providence has thus often shewn her strange wonder,
namely, that bad men should make other bad men good. For some find
themselves suffering injustice at the hands of evil men, and, burning with
hatred of those who have injured them, they have returned to cultivate the
fruits of virtue, because their aim is to be unlike those whom they hate.
To divine power, and to that alone, are evil things good, when it uses them
suitably so as to draw good results therefrom. For a definite order
embraces all things, so that even when some subject leaves the true place
assigned to it in the order, it returns to an order, though another, it may
be, lest aught
Page 134
in the realm of Providence be left to random chance. But "hard is it for me
to set forth all these matters as a god," nor is it right for a man to
try to comprehend with his mind all the means of divine working, or to
explain them in words. Let it be enough that we have seen that God, the
Creator of all nature, directs and disposes all things for good. And while
He urges all, that He has made manifest, to keep His own likeness, He
drives out by the course of Fate all evil from the bounds of His state.
Wherefore if you look to the disposition of Providence, you will reckon
naught as bad of all the evils which are held to abound upon earth.
'But I see that now you are weighed down by the burden of the question, and
wearied by the length of our reasoning, and waiting for the gentleness of
song. Take then your draught, be refreshed thereby and advance further the
stronger.
Translated by: W.V. Cooper, J.M. Dent and Company. London, 1902.
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# Can I break a random number into two smaller vectors and consider them as two random numbers?
I have a cryptographically secured RNG that uses a recommended block cipher to generate the random number. As its output, I receive the random number which is very large, but the application requires the usage of two random numbers, and both of them with smaller bit-size of the RNG output.
Can I split the random number into two smaller vectors and consider them as two random numbers? Is this a recommended practice?
• Yes you can and yes this is commonly done. – SEJPM Jan 16 '17 at 17:43
• ... you should however make sure that the bits of the two numbers you take from the larger number do not overlap. – Maarten Bodewes Jan 16 '17 at 18:03
Suppose that you have a pseudorandom generator that, on some seed $s$, outputs $n$ pseudorandom bits, where $n$ is even. Then on a uniformly random input seed $s$, prg$(s) = r$ can be written $r_1 + 2^{n/2}r_2$, with $(r_1,r_2) \in (\{0,1\}^{n/2})^2$. I claim that both $r_1$ and $r_2$ are computationally indistinguishable from uniformly random elements from $\{0,1\}^{n/2}$.
The intuition behind this is as follows: suppose toward contradiction that some polynomial size algorithm can distinguish $r_1$ from random, when $r_1$ is computed as the $n/2$ least significant bits of prg$(s) = r$, for a uniformly random $s$. Now, you are given an $n$-bit string $r$ and must tell whether it is random or it is the output of the PRG. Just decompose $r = r_1 + 2^{n/2}r_2$, and run your distinguisher on input $r_1$: if it tells you that $r_1$ is non-random, then $r$ is non-random (as the distribution of uniformly random $n$-bit numbers is perfectly equal to the distribution obtained by picking two uniformly random $n/2$-bit numbers $r_1,r_2$ and computing $r$ as $r_1 + 2^{n/2}r_2$), hence you can distinguish outputs of the PRG on random seeds from random $n$-bit values, contradicting the fact that the PRG is cryptographically secure. The same argument shows that $r_2$ cannot be distinguished from random.
More generally, fix any size-$k$ subset $S$ of $\{1, \cdots, n\}$, for some $k \leq n$; a similar argument shows that the $k$-bit string obtained by running a secure prg on a random seed, and taking the $k$ bits of the output indexed by $S$, is computationally indistinguishable from random (and the distinguishing advantage of any polytime adversary is at most equal to its distinguishing advantage against the PRG). You can have a bunch of random-looking bit strings just by considering any partition of the bits of your PRG output.
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time limit per test
5 seconds
memory limit per test
256 megabytes
input
standard input
output
standard output
After long-term research and lots of experiments leading Megapolian automobile manufacturer «AutoVoz» released a brand new car model named «Lada Malina». One of the most impressive features of «Lada Malina» is its highly efficient environment-friendly engines.
Consider car as a point in Oxy plane. Car is equipped with k engines numbered from 1 to k. Each engine is defined by its velocity vector whose coordinates are (vxi, vyi) measured in distance units per day. An engine may be turned on at any level wi, that is a real number between - 1 and + 1 (inclusive) that result in a term of (wi·vxi, wi·vyi) in the final car velocity. Namely, the final car velocity is equal to
(w1·vx1 + w2·vx2 + ... + wk·vxk, w1·vy1 + w2·vy2 + ... + wk·vyk)
Formally, if car moves with constant values of wi during the whole day then its x-coordinate will change by the first component of an expression above, and its y-coordinate will change by the second component of an expression above. For example, if all wi are equal to zero, the car won't move, and if all wi are equal to zero except w1 = 1, then car will move with the velocity of the first engine.
There are n factories in Megapolia, i-th of them is located in (fxi, fyi). On the i-th factory there are ai cars «Lada Malina» that are ready for operation.
As an attempt to increase sales of a new car, «AutoVoz» is going to hold an international exposition of cars. There are q options of exposition location and time, in the i-th of them exposition will happen in a point with coordinates (pxi, pyi) in ti days.
Of course, at the «AutoVoz» is going to bring as much new cars from factories as possible to the place of exposition. Cars are going to be moved by enabling their engines on some certain levels, such that at the beginning of an exposition car gets exactly to the exposition location.
However, for some of the options it may be impossible to bring cars from some of the factories to the exposition location by the moment of an exposition. Your task is to determine for each of the options of exposition location and time how many cars will be able to get there by the beginning of an exposition.
Input
The first line of input contains three integers k, n, q (2 ≤ k ≤ 10, 1 ≤ n ≤ 105, 1 ≤ q ≤ 105), the number of engines of «Lada Malina», number of factories producing «Lada Malina» and number of options of an exposition time and location respectively.
The following k lines contain the descriptions of «Lada Malina» engines. The i-th of them contains two integers vxi, vyi ( - 1000 ≤ vxi, vyi ≤ 1000) defining the velocity vector of the i-th engine. Velocity vector can't be zero, i.e. at least one of vxi and vyi is not equal to zero. It is guaranteed that no two velosity vectors are collinear (parallel).
Next n lines contain the descriptions of factories. The i-th of them contains two integers fxi, fyi, ai ( - 109 ≤ fxi, fyi ≤ 109, 1 ≤ ai ≤ 109) defining the coordinates of the i-th factory location and the number of cars that are located there.
The following q lines contain the descriptions of the car exposition. The i-th of them contains three integers pxi, pyi, ti ( - 109 ≤ pxi, pyi ≤ 109, 1 ≤ ti ≤ 105) defining the coordinates of the exposition location and the number of days till the exposition start in the i-th option.
Output
For each possible option of the exposition output the number of cars that will be able to get to the exposition location by the moment of its beginning.
Examples
Input
2 4 11 1-1 12 3 12 -2 1-2 1 1-2 -2 10 0 2
Output
3
Input
3 4 32 0-1 1-1 -2-3 0 61 -2 1-3 -7 33 2 2-1 -4 10 4 26 0 1
Output
490
Note
Images describing sample tests are given below. Exposition options are denoted with crosses, factories are denoted with points. Each factory is labeled with a number of cars that it has.
First sample test explanation:
• Car from the first factory is not able to get to the exposition location in time.
• Car from the second factory can get to the exposition in time if we set w1 = 0, w2 = 1.
• Car from the third factory can get to the exposition in time if we set , .
• Car from the fourth factory can get to the exposition in time if we set w1 = 1, w2 = 0.
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# An Elementary Way to Calculate the Gaussian Integral
## Fred Akalin
### January 06, 2011
While reading Timothy Gowers's blog I stumbled on Scott Carnahan's comment describing an elegant calculation of the Gaussian integral $\int_{-\infty}^{\infty} e^{-x^2} \, dx = \sqrt{\pi}\text{.}$ I was so struck by its elementary character that I imagined what it would be like written up, say, as an extra credit exercise in a single-variable calculus class:
Exercise 1. (The Gaussian integral.) Let $F(t) = \int_0^t e^{-x^2} \, dx \text{, }\qquad G(t) = \int_0^1 \frac{e^{-t^2 (1+x^2)}}{1+x^2} \, dx \text{,}$ and $H(t) = F(t)^2 + G(t)$.
1. Calculate $H(0)$.
2. Calculate and simplify $H'(t)$. What does this imply about $H(t)$?
3. Use part b to calculate $F(\infty) = \displaystyle\lim_{t \to \infty} F(t)$.
4. Use part c to calculate $\int_{-\infty}^{\infty} e^{-x^2} \, dx\text{.}$
Although this is simpler than the usual calculation of the Gaussian integral, for which careful reasoning is needed to justify the use of polar coordinates, it seems more like a certificate than an actual proof; you can convince yourself that the calculation is valid, but you gain no insight into the reasoning that led up to it.
Fortunately, David Speyer's comment solves the mystery; $G(t)$ falls out of doing the integration in Cartesian coordinates over a triangular region. Just for kicks, here's how I imagine an exercise based on this method would look like (this time for a multi-variable calculus class):
Exercise 2. (The Gaussian integral in Cartesian coordinates.) Let $A(t) = \iint\limits_{\triangle_t} e^{-(x^2+y^2)} \, dx \, dy$ where $\triangle_t$ is the triangle with vertices $(0, 0)$, $(t, 0)$, and $(t, t)$.
1. Use the substitution $y = sx$ to reduce $A(t)$ to a one-dimensional integral.
2. Use part a to calculate $A(\infty) = \lim_{t \to \infty} A(t)$.
3. Use part b to calculate $\int_{-\infty}^{\infty} e^{-x^2} \, dx\text{.}$
4. Let $F(t) = \int_0^t e^{-x^2} \, dx \qquad\text{ and }\qquad G(t) = \int_0^1 \frac{e^{-t^2 (1+x^2)}}{1+x^2} \, dx \text{.}$ Use part a to relate $F(t)$ to $G(t)$.
5. Use part d to derive a proof of part c using only single-variable calculus.
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Dear Uncle Colin,
Why is dividing by a half the same as doubling?
- How Arithmetic Leverages Fractions
Hi, HALF, and thanks for your message!
I’m going to give a couple of reasons: first, the algebra of it, then the logic.
## Algebra
Let’s set this up as $\frac{x}{\br{\frac{1}{2}}} = y$ - you’re asking why $y=2x$.
The ugly thing here is the fraction on the bottom, so let’s multiply both sides by that:
$x = \frac{1}{2}y$
Now double both sides:
$2x = y$, as required. Magic!
## Logic
When you divide by a half, you’re asking “how many halves go evenly into this number?”
You know that 1 is made of two halves, 2 is made of four halves, and so on - your number $x$ is made up of $2x$ halves.
In general, if you ask how many $\frac{a}{b}$s go into $x$, you can reason that 1 is made up of $\frac{b}{a}$ of them, so $x$ is made up of $x$ lots of $\frac{b}{a}$.
Hope that helps!
- Uncle Colin
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## Converting a function with single parameter to a function with multiple parameters
I have been solving some algorithm questions recently and a pattern I have observed in some problems is as follows:
Given a string or a list, do an aggregation operation on each of its elements. Here in each of these elements we apply some recurrence to solve it.
An example of one such problem is below.
Problem: Given n integers return the total number of binary search trees that can be formed using the n integers
To solve this problem, I define a recurrence relation as follows:
f(n) = 1 // if n = 0 f(n) = ∑ f(i) * f(n-i-1) where 0 <= i <= n-1
This works and I get the correct answer however I want to modify the function a bit.
Instead of expressing the function in terms of f(n) I want to express it in terms of f(n, i) so I can remove the summation. However I am unable to do it correctly.
Code
My code to solve the problem by defining the recurrence in terms of f(n) is as follows: (I am aware it can be optimized by DP but that is not what I am trying to do here)
public int f(int n) { if(n == 0) return 1; int result = 0; for(int i = 0; i< n; i++) result += f(i) * f(n-i-1); return result; }
I want to remove that for loop and instead express the function in terms of f(n,i) instead of f(n).
Question
1. How to convert the recurrence shown above from f(n) to f(n,i) and remove the summation?
• Here ‘n’ is the size of the list of element and ‘i’ is the ith element in the list that we choose to be the root of the tree.
## Applying the Parameter Theorem to show that a function is not computable
Show that $$g: \mathbb{N} \to \mathbb{N}$$ such that $$g(x)=\begin{cases} 1 & \text{if halt}(2833,x) \ 0 & \text{otherwise} \end{cases}$$ is not computable.
We know that
$$g(x)=\begin{cases} 1 & \text{if }\Phi_x(2833)\downarrow \ 0 & \text{if }\Phi_x(2833)\uparrow \end{cases}$$
How can I use the parameter theorem to reduce $$g$$ to $$\text{halt}(x,x)$$? I’m very confused.
## Is there any official documentation on the AdSense data-adtest=”on” parameter to test locally?
On many places over the internet you can find people suggesting the data-adtest="on" parameter to test ads on your local environment.
<ins className="adsbygoogle" style={{display:"inline-block", width:"360px", height:"180px"}} data-ad-client="XXXXX" data-ad-slot="XXXXX" data-adtest="on" // <----------------------------- > </ins>
I could make it work with trial and error. Some sites even suggest that the proper name is data-ad-test.
I there is, I still haven’t found.
## Demonstrating reflected XSS with GET Parameter and URL encoding
A client is developing a website which is vulnerable to reflected XSS through a GET parameter:
https://example.com/vulnerable-url?")||true)alert("XSS");</script>
I would like to demonstrate this vulnerability by providing a link like the above but the text contains characters (such as the ") which are URL encoded by a browser, resulting in an invalid, unexecuted script.
I’ve also found that using a form within HTML to perform a GET request also results in URL encoding of the payload string.
I can however use the BurpSuite proxy to make the request without URL encoding, resulting in the script execution.
I would like to demonstrate script using only a browser available in the client environment. Any ideas on how this could be achieved?
## what is this extra function call in the function parameter in c++?
I have new to c++ projects. What is the use of writing function calls after the function parameter?
I have attached the screenshot of the issue.
What are these function calls after the end of the parameter of the function solver_t? Such as ckt(c), simckt(s) and similarly all other function definitions.
## Does replica config parameter affect primary/master RDS Postgres?
I want to add hot_standby_feedback = on to a RDS readonly replica.
The problem is that the replica currently has a parameter group already attached, which is inherited from the master. My question is: does adding hot_standby_feedback = on to the master parameter group affect the master instance negatively so that I’d better attach a new parameter group to the replica?
## How to deindex an URL with specific parameter?
While I was doing an audit of my website SEO, I found a warning for a page that is most of the time blank.
Basically, this page serves for storing articles for visitors who would like to read their favorite selections later.
This is what the link looks like: https://example.com/?read-it-later
The problem with this is that the URL is the same as the homepage and as you can see it has next to it the parameter “read-it-later”.
So I want to be very careful on how to prevent this URL from being indexed by google without compromising the indexing of the homepage.
Do you have any suggestions on the best approach through .htaccess or WordPress?
## How can HTTP Parameter Pollution be exploited?
In HTTP Parameter Pollution, I know theory how it work; you inject multiple HTTP parameters with the same name to trigger bugs in the server, but I can’t understand how one can exploit this.
When I send some request using this technique and for example I know that the server is using last occurrence of parameter, how this technique can be useful, because no matter what, server this uses last occurrence, so it doesn’t matter what were other occurrences right? Or when server does concatenate parameters with same name, some server script will get concatenated result.
## Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘wpss_social_addtoany_js’
I have made an update of the plugins and themes and now it throws me this warning.
Warning: call_user_func_array() expects parameter 1 to be a valid callback, function ‘wpss_social_addtoany_js’ not found or invalid function name in /home/html/wp-includes/class-wp-hook.php on line 286
## IDX10630: The ‘[PII is hidden]’ for signing cannot be smaller than ‘[PII is hidden]’ bits. KeySize: ‘[PII is hidden]’. Parameter name: key.KeySize
I just created a SharePoint Add-in in Visual Studio for SharePoint 2016. When I run the add-in, which is nothing but anything that visual studio has generated, I am getting the following error:
IDX10630: The '[PII is hidden]' for signing cannot be smaller than '[PII is hidden]' bits. KeySize: '[PII is hidden]'. Parameter name: key.KeySize Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.ArgumentOutOfRangeException: IDX10630: The '[PII is hidden]' for signing cannot be smaller than '[PII is hidden]' bits. KeySize: '[PII is hidden]'. Parameter name: key.KeySize Source Error: Line 816: ); Line 817: Line 818: string actorTokenString = new JwtSecurityTokenHandler().WriteToken(actorToken); Line 819: Line 820: if (appOnly)
I am using asp.net mvc. Any idea what could be wrong? Thank you.
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# Recent questions tagged cl37072
Questions from:
### Find the equations of the hyperbola satisfying the given conditions: Vertices: $(0,\pm 3)$, Foci: $(0,\pm 5)$
To see more, click for the full list of questions or popular tags.
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Tag Info
Is this a 18-electron aromatic system? No, because as the OP says in the question, the rings are not in a single plane. Is this compound considered aromatic? Yes, because it has three aromatic rings, as the OP stated. They all have 6 delocalized electrons, so they conform to the $4n + 2$ rule. "What if" all carbon atoms were in a plane? The C14 and ...
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# Maximum number of digits in numbers between 0 to $n^2-1$ of base n
The number of digits in numbers between 0 and $n^2-1$ of base n is obtained by
$\log_n(n^2) = 2\log_nn = 2$
But why log is being used? I mean how doing log gives correct answer always?
• $\log_{10}(10^2) = 2$ but $100$ has 3 digits. Add 1. – jkabrg Jun 24 '15 at 18:17
• $n^2$ in base $n$ is always $100$. The number of digits is then constant: $3$. Maybe you're looking for the number of digits in $n^2$ for base $b$? – hexaflexagonal Jun 24 '15 at 18:19
• The number of digits in the square of a number n of base The number of digits in the square of a number $n$ of base $n$ is $3$ regardless of the value of $n$. Why make things any more complicated than that??? – barak manos Jun 24 '15 at 18:19
• $n^2$ is the smallest 3-digit number in base $n$. – jkabrg Jun 25 '15 at 8:10
In base $n$, $n$ is represented as $10_n$. So $$10_n^2 = 100_n$$ That's 3 digits.
Now $1+\log_n(n^2) = 3$. Done.
• I'm not going to downvote this, but you should keep an eye on it and delete it if the original question is edited. I think it's possible that OP mistyped. – hexaflexagonal Jun 24 '15 at 18:22
About the number of digits of a number $n^2$ in base $b$:
Let $n$ have the representation $$n = (d_{m-1} \cdots d_1 d_0)_b = \sum_{k=0}^{m-1} d_k b^k$$ with $m$ digits from $\{ 0, \ldots, b-1 \}$. Then we have $$n < b^m \Rightarrow n^2 < b^{2m}$$ This means $n^2$ has at most $2m-1$ digits.
To derive $m$ for a given $n$ we use some logarithm: $$n < b^m \Rightarrow \\ \log n < \log b^m = m \log b \Rightarrow \frac{\log n}{\log b} < m$$ The smallest $m$ should be $$m = \left\lfloor \frac{\log n}{\log b} \right\rfloor + 1$$ The special case $b = n$ gives $m = 2$ and that $n^2$ has at most $3$ digits.
As pointed out by fellow users $n^2 = (100)_n$ has exactly $3$ digits, which means that your formula, which gives $2$ digits, is not correct.
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# singlespacing in table with no indent
I'm trying to make a table that is as wide as the textwidth singlespaced with etoolbox's \AtBeginEnvironment but that somehow gets rid of the \noindent that I issued before.
\documentclass{report}
\usepackage{array,setspace,booktabs,tabularx,etoolbox}
\AtBeginEnvironment{tabularx}{\singlespacing\renewcommand{\arraystretch}{1.3}}
\usepackage{lipsum}
\begin{document}
\lipsum[1-2]
\noindent
\begin{tabularx}{\linewidth}{ @{} p{3em} X @{} }
\toprule
Table & Example \\
Table & Example \\
\bottomrule
\end{tabularx}
Any idea how to fix that?
• Your issuing of \singlespacing the \arraystretch redefinition comes too late anyway. – Werner Dec 4 '16 at 19:27
• @Werner Hmm, it does do it though, I mean the spacing. Only the indent. When I don't use etoolbox it's fine but where would I issue the singlespacing then? – jan Dec 4 '16 at 19:32
• Is the rest of your document not \singlespacing? – Werner Dec 4 '16 at 19:41
• @Werner Yeah, the rest is doublespaced, sorry, I didn't put that in the MWE (it's in the class) – jan Dec 4 '16 at 19:42
• Even if you use \noindent\singlespacing the indent appears. You can put \singlespacing\noindent to again force a \noindent. – Werner Dec 4 '16 at 19:44
\singlespacing ignores the use of \noindent. If you want to insert content as part of tabularx, redefine it as part of a new environment:
\documentclass{article}
\usepackage{setspace,tabularx,lipsum}
\let\oldtabularx\tabularx
\let\endoldtabularx\endtabularx
\renewenvironment{tabularx}[2]
{\singlespacing
\noindent
\oldtabularx{#1}{#2}}% https://tex.stackexchange.com/a/42331/5764
{\endoldtabularx}
\begin{document}
\doublespacing
\lipsum[1]
\begin{tabularx}{\linewidth}{ @{} p{3em} X @{} }
\hline
Table & Example \\
Table & Example \\
\hline
\end{tabularx}
\end{document}
`
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# Foolproof, and Other Mathematical Meditations
###### Brian Hayes
Publisher:
MIT Press
Publication Date:
2017
Number of Pages:
234
Format:
Hardcover
Price:
24.95
ISBN:
9780262036863
Category:
General
BLL Rating:
The Basic Library List Committee suggests that undergraduate mathematics libraries consider this book for acquisition.
[Reviewed by
Mark Hunacek
, on
11/11/2017
]
There is, of course, no shortage of books that attempt to explain interesting mathematical ideas to laypeople, but over the years I have found that they tend to be of variable quality. Some are so watered-down that they really only convey a false sense of understanding, others are so technical that they can’t really be understood by the intended audience, and others are, on occasion, just plain wrong. It takes some skill to write a popular book that is accurate, accessible and genuinely informative. Brian Hayes has that skill, and Foolproof is one of those books.
Though I have never read any other books by Hayes, the name was nonetheless somewhat familiar to me, and I soon realized why: over the years I have reviewed four books in the Best Writing on Mathematics annual anthology series, and three of those four books (2012, 2014 and 2016) contain articles by him. (In fact, the articles in the 2012 and 2014 issues appear as chapters here, as does an entry by Hayes in the 2010 anthology, which I have not seen.) It is not surprising that Hayes’ work shows up in Best Writing compilations, as he definitely has a way with words, as we can see even without venturing beyond the Preface:
I am not a mathematician — not a native citizen of the Republic of Numbers. But I have been living there, an expatriate litterateur, for most of my adult years. I have struggled to learn the language, immersed myself in the culture and customs, and become an enthusiastic amateur practitioner. My life has been greatly enriched by the experience.
This text consists of 13 essays, each of which appeared (in some form, anyway; they have been updated and in some cases expanded for this volume) in American Scientist magazine.
Considerations of space make it impracticable to describe in detail each of the chapters that comprise this book, but I can describe a few of them.
The first chapter is actually more historical than mathematical; in it, Hayes delves deeply into the famous story about how Gauss, given a busywork assignment by a teacher to add a large number of consecutive numbers, added them almost instantly with no calculation. As I learned this story many years ago, the numbers were the first 100 positive integers, and Gauss added them by rewriting the sum S = (1 + … + 100) as (100 + ….+ 1), adding the two together to get (100)(101), and then dividing by 2. This is not the way Hayes first learned the story, however; he has Gauss doing the sum in a different way. That inconsistency is at the heart of this article: Hayes carefully examines the historical evidence and concludes that the story may have grown in the telling, and that there is no uniformity on what numbers Gauss was asked to add or just how he did it. He also considers the issue of who, before Gauss, knew how to do this.
The fifth chapter is on the mathematics behind the game of Sudoku. This is the subject of an entire book (Taking Sudoku Seriously by Rosenhouse and Taalman), but here Hayes provides a nice survey of some of the basic questions discussed in that book: How many completed Sudoku puzzles are there? How many “essentially different” puzzles are there? What is the minimum number of clues that are necessary to ensure that a puzzle always has a unique solution? (One quibble: the Rosenhouse and Taalman book doesn’t appear in the bibliography for this article. It definitely should.)
There is, of course, a great deal more. Other articles, for example, discuss the history of space-filling curves, interesting stuff that can happen in n-dimensional space, random walks, and the decimal expansion of $\pi$. (This last article is another one that should interest historians. It discusses William Shanks, who, over a long period of time in the last half of the 19th century, computed $\pi$ to 707 decimal places — but made a mistake at around decimal place 527 that affected all the remaining digits. By diligent computer work, Hayes attempts to discover just what this mistake could have been.)
The book ends with a chapter-by-chapter bibliography. I was amused to see that the author was aware of certain aspects of his sources, such as the fact that Bell’s Men of Mathematics could not be uncriticially relied on as a source of factual information: “Bell has a reputation as a highly inventive writer (a trait not always considered considered a virtue in a biographer or historian).”
This compilation is a treasure trove of high-quality mathematical exposition. I saw nothing in it that a reader would later have to “unlearn” as being false, and although the chapters were sufficiently demanding that they would not insult the intelligence of a reader, they were accessible enough so that a layperson would likely get something out of them. For a sense of what the chapters are like, there is an online reprint of an article in American Scientist that became chapter 13 of the book now under review. (I plan on making this link available to the students in my courses this semester on geometry and the history of mathematics.) All of the chapters in this book, in fact, originally appeared in preliminary form in American Scientist, and finding PDF versions of these original articles online is not hard; in fact, the author generously provides them on his blog, “bit player”.
But don’t let the availability of these articles deter you from buying the book itself — the chapters in the book are generally improved and expanded versions of the original articles, and it is worth the relatively small price of the book to have them available in one convenient source. This is a book that will convey to any reader the elegance and beauty of mathematics. Undergraduate students should certainly be made aware of its existence, and faculty members, who already know that mathematics is elegant and beautiful, can use this book as fodder for course material or lectures to a math club. All told, this is a useful and enjoyable book, and is highly recommended.
Mark Hunacek (mhunacek@iastate.edu) teaches mathematics at Iowa State University.
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# Interface with touch screen using arduino
Basically I am trying to stimulate a touch screen with an arduino board. I know this has been asked several times and Ive spent a long time looking at solutions, namely some kind of foil stuck to a touch screen being pulled to phones ground, or USB shield, or arduino earth, or a fruit or your body etc. I have tried all of this and more, using a transistor, MOSFET, optocoupler, and even a relay. All while holding the phone, or on the table or on top of a foil sheet or a grounded foil sheet etc... I have had varying success with all of them but nothing reliable and repeatable long term.
The relay has been the most successful, connecting foil via the armeture switch to the phones ground. If I set the arduino to pulse the relay closed for 100ms every 2000ms in this case, Interestingly I find a consistent result: when I place the foil a touch occurs and isn't released, the foil and wire are enough to do it. After between 30 seconds to a minute, the touch is released and touch events start pulsing with the arduinos input via the relay, and after 30 seconds to a minute or so longer, the screen stops responding all together, even to finger touches on the back of the foil - where this produced a touch event beforehand.
So I figure the screen is adapting to the environment. Just as it would need to if you were using your phone standing on a flag pole vs leaning against the steel wall of a truck. For some reason it decides the foil is environmental noise and 'numbs' that area of the screen to it.
So my question is, is there a way to reset the capacitive field image between each touch, or is there a different method to achieve touch events using the arduino?
EDIT Attached is a basic schematic of the circuit. Pin 2 is switching from LOW to HIGH for 100ms, then to LOW, for 2 seconds, and the relay clicks closed accordingly. The wire labeled 'Wire A' has been tried a variety of ways. To iPhone Gnd like it is, to Arduino Gnd, to my fingers, to a piece of foil laid under the iPhone. Additionally I have tried all these combinations with a 1000k resistor in series, and capacitors varying from 100pf to 100nf, separately and together with the resistor.
The underlying problem is the piece of foil stuck to the screen. The iPhone sensor seems to be able to determine its proximity is not changing, even if its electrical characteristics are.
• Can you put up some pictures and a schematic? Apr 4, 2015 at 22:24
• Sure I will be home in a few hours and will draw something up Apr 5, 2015 at 15:46
I've actually made some progress with this method I have found the problem to be the parasitic, or static capacitance of whatever I stick to the screen. It is enough to bring the base level reference at that sensor up too high to consider anything else a touch.
If I stick the foil with a 5 inch strand of hair-width wire, and pinch the end of the wire, it will work for about 30 seconds then stop working. If I leave it for 10 minutes it still won't work, nor will touching the foil itself. If I clip the strand of wire to maybe 3 inches, and pinch the end, it will start working after 30 seconds. Leaving it again for 10 minutes, it still works.
So really the question is, if I have a piece of foil on the screen with a 2 inch strand of wire, how do I electrically connect something to that for a moment, without adding any parasitic capacitance to it in the mean time. A transistor by itself was ok, pinching the wire would still get a touch but as soon as I solder something to the emitter of the transistor the foil would stop working after 30 seconds. A relay also has too much metal inside the terminal, causing the same problem after 30 seconds. I am pretty sure I have the problem pinned down, as with both of these situations, if I clip what I have soldered off, after 30 seconds or so the foil begins working again if I pinch the little strand.
EDIT So the problem was a thick tempered glass screen protector I had on the phone. I removed that and the amount of material able to be connected to the foil increased substantially. It works perfectly with a relay for hours. I tried with a transistor it works for a while but eventually becomes 'numb' to it so I guess the minuscule current across the 'off' transistor is enough to cause the foils capacitance to increase.
Perhaps older phones measured pixel-to-ground capacitance, but I'd be surprised if new ones still do. It is just so much more sensitive to interference. Also, sensing mutual capacitance permits a row-column scanning sensor approach, where one conductive layer is divided into rows and another layer into columns, and the mutual capacitance of all $N$ columns is measured while stepping through rows $1...M$. In this way, it makes populating a $M\times N$ mutual capacitance array $\mathbf{C_M}$ quite easy.
In case you're wondering how this could be done, consider having all $M$ rows and $N$ columns discharged to $0\rm{V}$. Take row $i$ and charge it from $0\rm{V}$ to $5\rm{V}$. All $N$ columns will see an increase in voltage due to whatever small capacitance couples them to row $i$. Some columns, however, will see a greater voltage than others, because they have greater mutual capacitance to row $i$ due to a nearby finger. This process is repeated for all $M$ rows to populate $\mathbf{C_M}$, thus resolving the finger's position in two dimensions. I've glossed over some details, but that's the basic gist.
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# Math Help - Prove that the square root of a non-square number is irrational
1. ## Prove that the square root of a non-square number is irrational
Prove: If integer N>1 is not a perfect square, then sqrt(N) is irrational.
2. ## Irrational numbers
Hello o&apartyrock
Originally Posted by o&apartyrock
Prove: If integer N>1 is not a perfect square, then sqrt(N) is irrational.
Assume that $\sqrt{N}$ is rational; in other words
$\exists\, p, q \in\mathbb{N},\, \sqrt{N} = \frac{p}{q}$
and assume further that $hcf(p,q)=1$; in other words, that the fraction $\frac{p}{q}$ is in its lowest terms.
Then $N = \frac{p^2}{q^2}$
$\Rightarrow p^2 = Nq^2 \Rightarrow p^2$ has a factor $N$, since $hcf(p,q) = 1$
$\Rightarrow p$ has a factor $N$ (For if not, then $N$ is the product of the squares of one or more of the prime factors of $p$, and is therefore a perfect square. Contradiction.)
$\Rightarrow p = Nr, r\in\mathbb{N}$
$\Rightarrow p^2 = N^2r^2 = Nq^2$
$\Rightarrow q^2 = Nr^2$
$\Rightarrow q$ has a factor $N$
$\Rightarrow hcf(p,q) \ge N > 1$
Therefore $\sqrt{N}$ cannot be expressed in the form $\frac{p}{q}$, and is therefore irrational.
3. ## Why is this line true?
has a factor (For if not, then is the product of the squares of one or more of the prime factors of , and is therefore a perfect square. Contradiction.)
$\Rightarrow p^2 = Nq^2 \Rightarrow p^2$ has a factor $N$, since $hcf(p,q) = 1$
$\Rightarrow p$ has a factor $N$ (For if not, then $N$ is the product of the squares of one or more of the prime factors of $p$, and is therefore a perfect square. Contradiction.)
Almost, but not quite. For example, $6^2$ has a factor $12$ but $6$ does not have a factor $12.$ You should take into account not only that $N$ is not a perfect square but also that $\frac{p^2}N=q^2$ is a perfect square (in this case $\frac{6^2}{12}=3$ is not a perfect square).
This is how I would write out the proof. Let $N=p_1^{n_1}p_2^{n_2}\cdots p_k^{n_k}$ where the $p_i$ are distinct primes. Then at least one of the $n_i$ must be odd since $N$ is not a perfect square, say $n_1$ is odd.
If $\sqrt N=\frac ab$ where $a,b\in\mathbb Z,$ $b\ne0$ and $\gcd(a,b)=1,$ then
$Nb^2\ =\ a^2$
$\Rightarrow\ N\mid a^2$
$\Rightarrow\ p_1\mid a^2$ (since $p_1\mid N)$
$\Rightarrow\ p_1\mid a$ (since $p_1$ is prime)
$\Rightarrow\ p_1$ divides $a^2$ an even number of times
This is a contradiction because $p_1$ divides $N$ an odd number of times and $p_1\nmid b^2$ and so $p_1$ divides $Nb^2$ an odd number of times.
5. Hmm... now you have me slightly more confused! The proof you have provided, proscientia is quite elegant.
I still think Grandad's proof is valid though. Of course "if N divides $p^2$ then N divides p" is not generally true as your counter example of N=12 and p=6 shows. But we are given some extra constraints here, namely $p^2 = Nq^2$ and $gcd(p,q)=1$.
But GrandDad's proof appears in Mathematical Analyis 2nd ed by Apostol Theorem theorem 1.10. So it must be correct. and my question still remains:
Given $p^2 = Nq^2$ and $gcd(p,q)=1, \Rightarrow N|q^2$, but how does this imply $N|q$?
6. Originally Posted by aukie
But we are given some extra constraints here, namely $p^2 = Nq^2$ and $gcd(p,q)=1$.
Thanks for the reminder! I had completely forgotten about $p$ and $q$ having to be coprime.
Originally Posted by aukie
Given $p^2 = Nq^2$ and $gcd(p,q)=1, \Rightarrow N|q^2$, but how does this imply $N|q$?
I’m afraid I’m totally confused about that as well.
7. Originally Posted by aukie
Hmm... now you have me slightly more confused! The proof you have provided, proscientia is quite elegant.
I still think Grandad's proof is valid though. Of course "if N divides $p^2$ then N divides p" is not generally true as your counter example of N=12 and p=6 shows. But we are given some extra constraints here, namely $p^2 = Nq^2$ and $gcd(p,q)=1$.
But GrandDad's proof appears in Mathematical Analyis 2nd ed by Apostol Theorem theorem 1.10. So it must be correct. and my question still remains:
Given $p^2 = Nq^2$ and $gcd(p,q)=1, \Rightarrow N|q^2$, but how does this imply $N|q$?
Apostol's argument's correct because he's assuming something that hasn't been assumed here, namely: N has no square factors or, as said in number theory, N is square-free, and this is all the difference; otherwise his argument would be wrong, or at least lacking, since he doesn't remind $p^2=Nq^2$ at the moment of argumenting that $N \mid p^2 \Longrightarrow N \mid p$, but he needs not to: if N doesn't divides p then some prime factor of N doesn't divide p (this can be also said in the case 12 divides 6^2 but 12 doesn't divide 6, since 12 has prime factors 2,2,3 and 6 only 2,3...but 12 is not square free), but this factor appears in $p^2=Nq^2$ and this can't be since it appears at the first power in N...!.
Now, $p^2=Nq^2\,\,\,but\,\,\,N \nmid p \Longrightarrow \exists prime\,\,\,r\,\,\,s.t.\,\,r \mid N \wedge r \nmid p$
But this prime factor appears on the right hand in $p^2=Nq^2$ and thus it must appear in the left hand: $r \mid p^2 \Longrightarrow r \mid p$ and we get our contradiction.
Tonio
8. I'm so confused ... you assume that sqrt(N) is a reduced fraction, and so N = p^2/q^2 ... but since (p,q)=1, that implies that N is a rational number, and so we have a contradiction since N is supposed to be an integer greater than 1 ... cuz after that, we are treating N as if it's a rational number, and in that case, we can't really use prime decomposition on it, nor can we use the definition of divisibility ....
Could we do this also:
N is an integer greater than 1 and is not a perfect square.
Assume that sqrt(N) is a rational number say p/q with (p,q)=1 (reduced fraction).
=> N = p^2/q^2 => q^2|p^2 (since N is an integer) => q^2 = 1 (since (p,q)=1) => N = p^2. Contradiction since N is not a perfect square ... so sqrt(N) is not a rational. Since N is positive, sqrt(N) is a real number and since it is not a rational, it must be irrational.
9. Originally Posted by Bingk
I'm so confused ... you assume that sqrt(N) is a reduced fraction, and so N = p^2/q^2 ... but since (p,q)=1, that implies that N is a rational number, and so we have a contradiction since N is supposed to be an integer greater than 1
$\color{red}\mbox{And who said q cannot be} \pm 1?$
tonio
... cuz after that, we are treating N as if it's a rational number, and in that case, we can't really use prime decomposition on it, nor can we use the definition of divisibility ....
Could we do this also:
N is an integer greater than 1 and is not a perfect square.
Assume that sqrt(N) is a rational number say p/q with (p,q)=1 (reduced fraction).
=> N = p^2/q^2 => q^2|p^2 (since N is an integer) => q^2 = 1 (since (p,q)=1) => N = p^2. Contradiction since N is not a perfect square ... so sqrt(N) is not a rational. Since N is positive, sqrt(N) is a real number and since it is not a rational, it must be irrational.
.
10. ## Putting right my error!
Hello everyone -
Since I wrote this line, six months ago,
$\Rightarrow p^2 = Nq^2 \Rightarrow p^2$ has a factor $N$, since $hcf(p,q) = 1$
$\Rightarrow p$ has a factor $N$ (For if not, then $N$ is the product of the squares of one or more of the prime factors of $p$, and is therefore a perfect square. Contradiction.)
I (like many others) have been puzzling over what I meant by it!
I was wrong: the conclusion " $p$ has a factor $N$" is not valid, and I apologise for the confusion this may have caused. I was attempting to modify the well known proof that $\sqrt2$ is irrational, and I was guilty of over-simplification.
What I should have said is that $p^2=Nq^2$ implies that there is a prime factor, $n$ say, of $N$,
for which the quotient $\frac{p^2}{N}$ is a multiple of $n$. (For if not, then $N$ is the product of even powers of one or more of the prime factors of $p$, and is therefore a perfect square. Contradiction.)
The proof then follows similar lines to my original 'proof', using $n$ rather than $N$:
$q^2=\frac{p^2}{N}=rn$, for some integer $r$
$\Rightarrow q^2$ has a prime factor $n$
$\Rightarrow q$ has a prime factor $n$
But $n|N$ and $N|p \Rightarrow n|p\Rightarrow \gcd(p,q)\ge n$, and this contradicts the initial hypothesis that $\gcd(p,q)=1$.
Further comment
I can fully understand where the problems arise as far as the part played by $q$ is concerned, and the confusion caused by the fact that $q$ is co-prime with $p$. The fact is, of course, that $\gcd(p,q)=1$ tends to bring with it a whole lot of contradictions - that's the
whole nature of the problem!
So at the risk of adding further confusion, may I attempt to amplify my argument, and so atone in some measure for my original error?
The statement $p^2 = Nq^2$ is clear enough, and it obviously means that $N$ is a factor of $p^2$. So forget for the time being that $q^2$ is the other factor of $p^2$, and concentrate on $N$. We'll use the fact that $p$ and $q$ are co-prime all in good time.
Since $N$ is not a perfect square, it therefore has, among its prime factors, at least one with an odd power. It is this prime number that I am calling $n$ (and which proscientia called $p_1$).
The fact that $p^2$, with its array of even-powered prime factors, has $N$ as a factor with its odd-powered prime factor $n$ means that when we simplify (by cancelling) the fraction $\frac{p^2}{N}$ there will inevitably be at least one $n$ left uncancelled in the numerator. That's where I get my statement from that $\frac{p^2}{N}$ is a multiple of $n$.
It's only at the end that we need to invoke the condition that $\gcd(p,q)=1$. It's when we try to do so too early that the confusion arises.
I hope that helps to clear things up.
11. No one said that q cannot be $\pm 1$ ... my problem is that someone should have said that q^2 MUST be 1 ...
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# What is Event Horizon of a Black Hole? [closed]
The boundary of a black hole is said to be surrounded by event horizon - the point of no return! What is its significance in terms of general relativity?
• The question "What is its significance in terms of general relativity?" is both too broad and out of scope for this site (belongs on Physics.SE). Could you clarify exactly what information you are looking for? – called2voyage Feb 25 '14 at 17:28
• What I mean to say is, how are the characteristics of event horizon related to Space-Time? – Spacetrekker Feb 26 '14 at 13:45
It is exactly the point of no return for light. In other words, it is the point (actually more like a sphere) in which the escape velocity from the Black Hole gravity reaches $c$.
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# The work function and mutual forces between particles
#### dRic2
Gold Member
Problem Statement
Let us assume that the work function of an assembly of free particles, subject to mutual forces between these particles, depends only on the relative coordinates
$$\xi_{ik} = x_i - x_k$$
$$\eta_{ik} = y_i - y_k$$
$$\zeta_{ik} = z_i - z_k$$
of any given particle $P_i$ and $P_k$:
$$U = U(\xi_{ik}, \eta_{ik}, \zeta_{ik})$$
Let the coordinate $x_i$ be varied by $\delta x_i$, thus obtaining the x-component of the force acting at $P_i$. Show that the quantity:
$$X_{ik} = \frac {\partial U}{\partial \xi_{ik}}$$
can be interpreted as the x-component of the force on $P_i$ due to $P_k$.
Relevant Equations
.
I tried to apply the chain rule
$$X_{ik} = \frac {\partial U}{\partial \xi_{ik}} = \frac {\partial U}{\partial x_{i}} \frac {\partial x_i}{\partial \xi_{ik}} = \frac {\partial U}{\partial x_{i}}$$
and I got the force x-component of the force acting on $P_i$ I guess.
but I do not know what to conclude from this...
Related Advanced Physics Homework News on Phys.org
#### Fred Wright
For definiteness consider a gas of electrons subject (obviously) to Coulomb potential. For N electrons you can show that:$$U_E=\frac {1}{8\pi \epsilon_0}\sum_{i=1}^{N} q_i \sum_{j=1}^{ ,N(i\neq j )}\frac{q_j}{\sqrt{\xi_{ij}^2 + \eta_{ij}^2+ \zeta_{ij}^2 }}$$
Will differentiation w.r.t xi yield units of force? I leave it to you to prove the above equation.
#### dRic2
Gold Member
Thanks for the reply, but I solved it by considering the frame of reference moving with, for example, the particle $P_k$. It this manner $\delta \xi_{ij} = \delta x_i$ (because $\delta x_j = 0$) and so it is obvious that the only work done after the displacement $\delta x_i$ comes from the force on $P_i$ due to $P_k$ (because all the other displacements vanish and thus do not contribute).
"The work function and mutual forces between particles"
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# How to prove a two variable set is convex
$X=\{(x,y)\in R^2\ :\ 3\le 2x+3y\le 8\}$
i tried to solve it as:
Let set $X$ is convex for $x_2,y_2\in X$ such that $\alpha x_1+(1-\alpha)x_2$,$\alpha y_1+(1-\alpha)y_2\in X$
Now, $3\le 2x+3y\le 8$ $2{\alpha x_1+(1-\alpha)x_2}+{3{\alpha y_1+(1-\alpha)y_2}}$ implies ${2\alpha x_1+2x_2-2\alpha x_2}+{3\alpha y_1+3y_2-3\alpha y_2}$; ${2\alpha(x_1-x_2)+2x_2}+{3\alpha(y_1-y_2)+3y_2}$
when $\alpha =0$, $2x_2+3y_2$ and when $\alpha=1$ $2x_1+3y_1$
## bumped to the homepage by Community♦2 days ago
This question has answers that may be good or bad; the system has marked it active so that they can be reviewed.
• Welcome to MathSE! You are more likely to get a good answer to your question if you follow a few guidelines. In particular, make your question clear. Just what are you asking? – Rory Daulton Mar 26 '16 at 22:03
• Generally it is easy to apply the definition of convexity directly to sets that are defined by linear inequalities. Since your set $X$ is defined by a pair of inequalities, $3\le 2x+3y$ and $2x+3y \le 8$, this should be a particularly straightforward approach. – hardmath Mar 26 '16 at 22:26
$X$ is a convex because it is the intersection of 2 half-planes
$$\{(x,y)|2x+3y\leq8\} \ \ \text{and} \ \ \{(x,y)|2x+3y\geq3\}$$
The reason is that a half-plane is the pre-image by a continuous function of a convex set (Convex Sets Pre-image); for example, in the first case, the pre-image of $(-\infty,8]$ by the continuous function $(x,y)\rightarrow2x+3y$.
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• We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.
• Neutrinos in the cosmic ray flux with energies near 1 EeV and above are detectable with the Surface Detector array of the Pierre Auger Observatory. We report here on searches through Auger data from 1 January 2004 until 20 June 2013. No neutrino candidates were found, yielding a limit to the diffuse flux of ultra-high energy neutrinos that challenges the Waxman-Bahcall bound predictions. Neutrino identification is attempted using the broad time-structure of the signals expected in the SD stations, and is efficiently done for neutrinos of all flavors interacting in the atmosphere at large zenith angles, as well as for "Earth-skimming" neutrino interactions in the case of tau neutrinos. In this paper the searches for downward-going neutrinos in the zenith angle bins $60^\circ-75^\circ$ and $75^\circ-90^\circ$ as well as for upward-going neutrinos, are combined to give a single limit. The $90\%$ C.L. single-flavor limit to the diffuse flux of ultra-high energy neutrinos with an $E^{-2}$ spectrum in the energy range $1.0 \times 10^{17}$ eV - $2.5 \times 10^{19}$ eV is $E_\nu^2 dN_\nu/dE_\nu < 6.4 \times 10^{-9}~ {\rm GeV~ cm^{-2}~ s^{-1}~ sr^{-1}}$.
• A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.
The Japanese Experiment Module (JEM) Extreme Universe Space Observatory (EUSO) will be launched and attached to the Japanese module of the International Space Station (ISS). Its aim is to observe UV photon tracks produced by ultra-high energy cosmic rays developing in the atmosphere and producing extensive air showers. The key element of the instrument is a very wide-field, very fast, large-lense telescope that can detect extreme energy particles with energy above $10^{19}$ eV. The Atmospheric Monitoring System (AMS), comprising, among others, the Infrared Camera (IRCAM), which is the Spanish contribution, plays a fundamental role in the understanding of the atmospheric conditions in the Field of View (FoV) of the telescope. It is used to detect the temperature of clouds and to obtain the cloud coverage and cloud top altitude during the observation period of the JEM-EUSO main instrument. SENER is responsible for the preliminary design of the Front End Electronics (FEE) of the Infrared Camera, based on an uncooled microbolometer, and the manufacturing and verification of the prototype model. This paper describes the flight design drivers and key factors to achieve the target features, namely, detector biasing with electrical noise better than $100 \mu$V from $1$ Hz to $10$ MHz, temperature control of the microbolometer, from $10^{\circ}$C to $40^{\circ}$C with stability better than $10$ mK over $4.8$ hours, low noise high bandwidth amplifier adaptation of the microbolometer output to differential input before analog to digital conversion, housekeeping generation, microbolometer control, and image accumulation for noise reduction.
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This vignette is based on data collected for the 538 story entitled “Projecting The Top 50 Players In The 2015 NBA Draft Class” by Neil Paine and Zach Bradshaw available here.
First, we load the required packages to reproduce analysis.
library(fivethirtyeight)
library(ggplot2)
library(dplyr)
library(ggthemes)
library(knitr)
# Turn off scientific notation
options(scipen = 99)
# Group the projected statistical plus-minus by year
The nba_draft_2015 data frame features National Basketball Association players and prospects. Each player has a draft_year that corresponds to the year the player was drafted into the NBA, if at all. We are interested in analyzing the average projected_spm for each draft year. Here, projected_spm corresponds to FiveThirtyEight’s model of projected statistical plus-minus over year 2-5 of the player’s NBA career. Plus-minus is defined by BasketballReference.com as “box score-based metric for evaluating basketball players’ quality and contribution to the team.” It is measured on a per 100 possessions basis to factor out playing time and adjusted so that the score is relative to the average NBA player. Further from BasketballReference, “0.0 is league average, +5 means the player is 5 points better than an average player over 100 possessions (which is about All-NBA level), -2 is replacement level, and -5 is really bad.”
nba_yearly <- nba_draft_2015 %>%
group_by(draft_year) %>%
summarise(mean_proj_spm = mean(projected_spm))
## summarise() ungrouping output (override with .groups argument)
nba_yearly
## # A tibble: 15 x 2
## draft_year mean_proj_spm
## <int> <dbl>
## 1 2001 -0.743
## 2 2002 -0.854
## 3 2003 -1.00
## 4 2004 -0.962
## 5 2005 -0.792
## 6 2006 -0.886
## 7 2007 -0.845
## 8 2008 -0.831
## 9 2009 -0.878
## 10 2010 -0.841
## 11 2011 -0.754
## 12 2012 -0.729
## 13 2013 -0.773
## 14 2014 -0.703
## 15 2015 -0.616
# Graph it!
Now that we have calculated the mean projected plus-minus for each draft year, let’s plot it to better understand which draft class was projected to have the most impact on team success.
ggplot(nba_yearly, aes(x = draft_year, y = mean_proj_spm, fill = mean_proj_spm)) +
geom_col() +
theme_fivethirtyeight() +
labs(title = "Which NBA draft class was best?",
subtitle = "As measured by the mean player/prospect's projected plus-minus",
caption = "Data from FiveThirtyEight") +
theme(legend.position = "none",
plot.title = element_text(face = "bold", size = 20),
plot.subtitle = element_text(size = 12),
plot.caption = element_text(hjust = 0, size = 10))
The overall trend here is that NBA draft classes, on average, have shown an increase in mean projected plus-minus since 2003. Based on this analysis, 2015 is the best draft class since it has the highest mean projected plus-minus of any year. Another way to think of this is that 2015 was the most balanced based on this metric. This plot also shows that the draft classes have tended to be projected as having more impact on team success over time.
# So what about 2003 and 2004?
So who were the players in that 2003 NBA draft class? What about in 2004 that has the second largest (in magnitude) average projected plus-minus. Let’s explore the top three projected_spm for 2003 and 2004:
nba_draft_2015 %>%
filter(draft_year %in% c(2003, 2004)) %>%
group_by(draft_year) %>%
top_n(projected_spm, n = 3) %>%
select(player, position, draft_year, projected_spm)
## # A tibble: 6 x 4
## # Groups: draft_year [2]
## player position draft_year projected_spm
## <chr> <chr> <int> <dbl>
## 1 Andre Iguodala SG 2004 0.724
## 2 Luol Deng SF 2004 0.402
## 3 Emeka Okafor PF 2004 0.383
## 4 Dwyane Wade SG 2003 0.739
## 5 Chris Kaman C 2003 0.407
## 6 Carmelo Anthony SF 2003 0.364
If you are familiar with NBA basketball, these names will stick out to you. Dwayne Wade and Carmelo Anthony are perennial all-stars and Andre Iguodala was the 2015 NBA Finals MVP. (Note that LeBron James is not in this data.)
The surprising thing here is that these great players were not able to counter-balance the players with low projected_spm. Remember that the mean was used here so even if the great players were outliers (in the positive direction) they weren’t able to pull the mean in their direction. Also note that not all of the players listed in this data set ended up playing in the NBA or, if they did, potentially only played a small amount of time.
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Technical Article
# Transimpedance Amplifier Stability
May 29, 2019 by Dr. Sergio Franco
## Learn about how to stabilize transimpedance amplifiers or TIAs with useful examples.
Learn about transimpedance amplifier stability with practical methods and useful examples.
This article covers transimpedance amplifiers and how to stabilize them.
If you'd like to learn more, please check out our article on how to analyze stability in transimpedance amplifiers.
### What Is a Transimpedance Amplifier?
We begin by defining what a transimpedance amplifier is. For context, let's take a look at an example circuit.
##### Figure 1. (a) Basic I-V converter, or transimpedance amplifier (TIA). (b) Practical implementation, showing the stray capacitance Cn associated with the op-amp’s inverting input pin.
The circuit of Figure 1(a) accepts an input current Ii and converts it to an output voltage Vo. Aptly called I-V converter, it finds a variety of applications, two prominent ones being as photodiode preamplifier and as a buffer for current-output digital-to-analog converters (DACs). To find the relationship between Vo and Ii, we use Ohm’s law to write Vo – Vn = RIi, and the op-amp law to write Vo = a(0 – Vn) = –aVn, where a is the op-amp’s open-loop gain. Eliminating Vn and solving for the ratio Vo/Ii, we get the closed-loop gain
#### $$A=\frac{V_{O}}{I_{i}}=\frac{R}{1+\frac{1}{a}}$$
##### Equation 1
In the ideal op-amp limit a→∞, we have A → Aideal = R. Since A has the dimensions of volts/amperes, or ohms, which are the dimensions of impedance, A is aptly called the transimpedance gain, and the circuit is also known as a transimpedance amplifier (TIA).
A real-life TIA, depicted in Figure1(b) includes also a stray capacitance Cn, consisting of the parasitic capacitances (discussed in a previous article on input capacitance in op-ampsplus the parasitic capacitance of the circuit providing Ii (typically, a photodiode or a current-output DAC). Depending on the application, Cn is typically on the order of 10 pF to 100 pF or higher. Regardless, it is a common tenet that Cn tends to destabilize the TIA, so it is the task of the designer to take suitable measures to stabilize the circuit.
### Destabilization in Stray Capacitance: Rate of Closure
Let us investigate the destabilizing tendency of Cn using the rate-of-closure (ROC). To this end, we set the input source to zero, break the loop as in Figure 2(a), apply a test voltage Vt and calculate the feedback factor β(jƒ) as
#### $$β(jf)=\frac{V_{n}}{V_{t}}=\frac{\frac{1}{j2πfC_{n}}}{\frac{1}{j2πfC_{n}}+R}=\frac{1}{1+j2πfRC}$$
##### Equation 2
This is readily put in the form
where
#### $$f_{p}=\frac{1}{2πRC_{n}}$$
##### Equation 4
Physically, Cn and R establish a pole frequency within the feedback loop. Consequently, a signal traveling around the loop will have to contend with two poles, one due to the op-amp and the other due to Cn, with the risk of a phase shift approaching 180° and thus jeopardizing circuit stability. We can better visualize this in Figure 2(b), which shows the plots of the open-loop gain |a| and the reciprocal of the feedback factor |1/β(jƒ)|, where
#### $$\frac{1}{β(jf)}=1+\frac{jf}{f_{p}}$$
##### Equation 5
The pole frequency ƒp of β(jƒ) is a zero frequency of 1/β(jƒ), indicating that the |1/β(jƒ)| curve starts to rise at ƒp. If ƒp is low enough compared with the crossover frequency ƒx, the ROC will approach 40 dB/dec, indicating a phase-margin approaching zero.
A common cure for combating the phase lag due to Cn is to introduce phase lead by means of a feedback capacitance Cƒ across R, as depicted in Figure 3(a).
##### Figure 3. (a) Combating the phase lag due to Cn by means of the phase-lead introduced by Cƒ. (b) Imposing ƒz = ƒp for a phase margin ɸm ≈ 45°.
Equation (2) still holds, provided we replace R with Z(jƒ) = R||[1/(j2πƒCƒ)]. This gives, after some algebraic manipulation,
where
#### $$f_{p}=\frac{1}{2πR(C_{n}+C_{f})}$$ $$f_{z}=\frac{1}{2πRC_{f}}$$
##### Equation 7
Note that Cƒ creates a zero frequency ƒz for β(jƒ), while also lowering the existing pole frequency ƒp somewhat (recall that a pole/zero for β becomes a zero/pole for 1/β).
An easy-to-visualize technique specifies Cƒ so as to position ƒz right at ƒx, as in Figure 3(b). This reduces the ROC from about 40 dB/dec to about 30 dB/dec, thus ensuring a phase margin of about 45°. To find the required Cƒ, we note from Figure 3(b) that ƒz equals the geometric mean of ƒp and ft, that is, ƒz = p׃t)1/2. Using the expressions of Equation (7) and simplifying gives
#### $$C_{f}=\sqrt{\frac{C_{n}+C_{f}}{2πRf_{t}}}$$
##### Equation 8
This transcendental equation is readily solved by iterations, as shown next.
### A Photodiode Preamplifier Example
The circuit of Figure 4 typifies a photodiode preamplifier, such as those used in light detection and ranging (LiDAR).
##### Figure 4. Photodiode preamplifier with compensation for a phase margin ɸm ≈ 45°.
Incident light causes the photodiode to draw a small current (up to a few microamperes), which the op-amp then converts to a useable voltage. The op-amp is assumed to have a constant gain-bandwidth product of 10 MHz, and the total stray input capacitance (sum of the diode’s junction capacitance and the stray capacitances of the op-amp, circuit components, and circuit traces) is assumed to be 50 nF. The value of Cƒ is found via Equation (8). Start out assuming Cƒ = 0 and get
$$C_{f}=[\frac{(50+0)×10^{-12}}{(2π10^{6}×10^{7})}]^{1/2}=0.892pF$$
Iterate as Cƒ = [(50 + 0.892)×10–12/(2π106×107)]1/2 = 0.900 pF. Another iteration gives again 0.900 pF, so we stop at this value.
Next, let us verify our findings via PSpice. Using the circuit of Figure 5(a) we obtain the plots of Figure 5(b).
##### Figure 5. (a) PSpice circuit to plot |a| and |1/β| for the TIA of Figure 4. (b) The |1/β| curves for the uncompensated (Cƒ = 0) and the compensated (Cƒ = 0.9 pF) cases.
For the uncompensated case we measure ƒx = 178.4 kHz, and the phase angles ph[a(jƒx)] ≈ –90° and ph[1/β(jƒx)] ≈ 89.0°, so the phase margin is
#### $$ɸ_{m}=180º+ph[a(jf_{x})]-ph[\frac{1}{β(jf_{x})}]≈180-90-89=1º$$
##### Equation 9
indicating an almost oscillatory circuit.
For the compensated case we measure ƒx = 224.8 kHz, and the phase angles ph[a(jƒx)] ≈ –90° and ph[1/β(jƒx)] ≈ 37.4°, so the phase margin is now ɸm = 180 – 90 – 37.4 = 52.6°, a bit better than the desired ɸm = 45°. The above findings are confirmed by the closed-loop transient responses of Figure 6. Without compensation, the circuit gives a slow-decaying oscillation, whereas compensation tames the oscillation dramatically (what a 0.9 pF capacitor can do!).
##### Figure 6. (a) PSpice circuit to plot the step response of the TIA of Figure 4. (b) The |1/β| curves for the uncompensated (Cƒ = 0) and compensated (Cƒ = 0.9 pF) cases.
The compensated response still exhibits some ringing, and the AC response (shown in Figure 8 below) exhibits some peaking. To eliminate peaking, ɸm must be raised to 65.5°, and to eliminate ringing it must be raised to 76.3°. (For this, I am referencing my book, Design with Operational Amplifiers and Analog Integrated Circuits, 4th Edition.)
Raising ɸm above 45° will result in the situation depicted in Figure 7.
##### Figure 7. – Linearized diagram showing the 1/β curve for ɸm > 45°.
Using the PSpice circuit of Figure 5(a), we find by trial-and-error that the required values of Cƒ are as follows:
For ɸm = 45.0° use Cƒ = 0.738 pF and get ƒx = 209 kHz
For ɸm = 60.5° use Cƒ = 1.098 pF and get ƒx = 248 kHz
For ɸm = 73.3° use Cƒ = 1.606 pF and get ƒx = 326 kHz
The corresponding closed-loop responses are shown in Figure 8.
##### Figure 8. – Closed-loop (a) AC responses and (b) transient responses of the circuit of Figure 4.
As usual, the price for an increased phase margin is a reduced AC bandwidth and a slower transient response.
### TIA Using a Current-Feedback Amplifier (CFA)
The stray inverting-input capacitance has a destabilizing effect also on TIAs based on current-feedback amplifiers (CFAs), as depicted in Figure 9.
##### Figure 9. (a) CFA-based TIA, and (b) compensation for a phase margin of about 45.0°.
This topic is covered in a previous article on dual CFAs and composite amplifiers, where it is shown that the required feedback capacitance for ɸm ≈ 45.0° is
### TIA Using a T-Network
As discussed in connection with Equation (1), the transconductance gain, in the limit a →∞, is Aideal = R. There are applications requiring much higher values of R than 1 MΩ, values that may prove physically impractical. A popular trick around this conundrum is to interpose a voltage divider R1-R2 between the op-amp output and the feedback resistance R, as depicted in Figure 10(a).
##### Figure 10. (a) TIA with a T-network. (b) The voltage divider reduces the effective transition frequency from ƒt to ƒt/(1 + R2/R1).
The voltage at the node common to the three resistances is still, ideally, RIi. The op-amp then magnifies this voltage according to the gain expression of the noninverting configuration, in this case, 1 + R2/(R||R1), so
#### $$A_{ideal}=(1+\frac{R_{2}}{R||R_{1}})R=mR$$
##### Equation 11
We are in effect witnessing a resistance multiplication by a factor of
#### $$m=1+\frac{R_{2}}{R_{1}}+\frac{R_{2}}{R}$$
##### Equation 12
With the component values shown, m = 1 + 9/1 + 9×103/106 ≈ 10, so we are achieving Aideal = 107 V/A with a physical resistance of only 106 Ω. As depicted in Figure 10(b), the voltage divider shifts the baseline from 0 dB to +20 dB. Comparison with Figure 3(b) reveals that we are now dealing with an effective transition frequency of ƒt/10, or 1 MHz. Equation (8) still holds, provided we use 1 MHz for ƒt, so Cƒ must be made 101/2 times as large. For ɸm ≈ 45° we calculate Cƒ = 0.900×101/2 = 2.85 pF.
The more refined value of Cƒ = 2.26 pF shown in Figure 11(a) is found by trial and error, as usual.
### Practical considerations
The above examples indicate rather small values of Cƒ, typically in the range of picofarads or even sub-picofarads. Such small values may prove physically impractical, so we start out with a more practical value, such as Cƒ = 10 pF, and then we force the op-amp to drive Cƒ via a voltage divider to scale Cƒ down to the (smaller) desired value. This is depicted in Figure 12 for the case ɸm = 45.0°.
##### Figure 12. (a) Simulating a TIA with the capacitance divider R1-R2. (b) Plots of |a| and |1/β| after R2 has been fine-tuned for ɸm = 45°.
As seen earlier, this requires an effective capacitance of 0.738 pF, so we need to impose
$$0.738=\frac{R_{1}}{R_{1}+R_{2}}10$$
Letting R1 = 1 kΩ, we need R2 = 12.6 kΩ. Starting out with this value, and then fine-tuning it by trial-and-error to achieve ɸm = 45.0°, we end up with the value 11.4 kΩ, as shown in Figure 12. Clearly, the voltage divider provides the additional advantage of capacitance tuning via resistance tuning.
Figure 12b reveals also a high-frequency rise of the |1/β| curve, but this is inconsequential if we manage to keep it sufficiently above ƒx. We achieve this by imposing R1||R2 << R.
I hope this article has helped you gain a better understanding of how to stabilize transimpedance amplifiers.
If you'd like more articles like these, please let us know what you'd like to learn in the comments below.
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Free Version
Difficult
Find a Segment of the Opposite Side Divided by Angle Bisector
GEOM-JNVMIN
$$\text {Given: }NE=12, NT=16, ET=28$$
$$\text {Find the value of ES.}$$
A
$7$
B
$12$
C
$16$
D
$21$
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# Text A text is used to style some inline text with a simple color
## Definition
#### Text
A text is always used inline and uses one color from the FUI color palette
To not interfere with all other colorable elements the text element is limited to be used in span tags only
This is red inline text and this is blue inline text and this is purple inline text
This is red inline text and this is blue inline text and this is purple inline text
## Variations
#### Size New in 2.7.2
Text can vary in the same sizes as icons
Starting with mini text
which turns into tiny text
changing to small text until it is
the default medium text
and could be large text
to turn into big text
then growing to huge text
to finally become massive text
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How do I find the complex conjugate of 12/(5i)?
Aug 12, 2015
The conjugate is $\frac{12 i}{5}$
Explanation:
To find a conjugate of a complex number we first have to convert it to a form $a + b i$. To do this here we can multiply both numerator and denominator by $i$
$z = \frac{12}{5 i} = \frac{12 i}{5 {i}^{2}} = \frac{12 i}{- 5} = - \frac{12 i}{5}$
Now to calculate the conjugate we just have to change sign of the imaginary part:
$\overline{z} = \frac{12 i}{5}$
Aug 13, 2015
In $a + b i$ form, this starts off as:
$0 + \frac{12}{5 i}$
Note that $\left[\frac{12}{5 i} = \frac{12}{5} \cdot \frac{1}{i}\right] \ne \left[\frac{12 i}{5} = \frac{12}{5} i\right]$)
$\frac{12}{5 i} \cdot \left(\frac{i}{i}\right) = \frac{12 i}{5 {i}^{2}} = \frac{12 i}{- 5}$
We currently have:
$a + b i = 0 + \frac{12 i}{- 5}$
The conjugate is $a - b i$, thus we get:
$a - b i = 0 - \frac{12 i}{- 5}$
$= \frac{12 i}{5} = \textcolor{b l u e}{\frac{12}{5} i}$
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## Thinking Mathematically (6th Edition)
$6840$ ways
A permutation from a group of items occurs when no item is used more than once and the order of arrangement makes a difference. The number of permutations possible if $r$ items are taken from $n$ items is ${}_{n}P_{r}=\displaystyle \frac{n!}{(n-r)!}$. ---------------- Order (of preference) is important, so we count permutations of r=3 movies taken from n=20. The formula ${}_{n}P_{r}=\displaystyle \frac{n!}{(n-r)!}$ applies. ${}_{20}P_{3}=\displaystyle \frac{20!}{17!}=20\times 19\times 18=$ $=6840$ ways
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