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Using genome sequencing and phylogenetics, researchers have shown that the industrial yeast Pichia kudriavzevii is genetically the same species as Candida krusei.
From infant skeletal remains going back hundreds of years, a team produced three Treponema pallidum genomes, representing both syphilis- and yaws-causing sub-species.
In PLOS this week: comparison of commercial bisulfite kits, new method to predict essential proteins, and more
Researchers have uncovered a trio of human-specific genes that seem to govern people's large brain size, Reuters reports.
Using bioinformatic and molecular cytogenetic approaches, researchers retraced ancestral "diapsid" reptile genome patterns from extant bird and reptile genomes.
Sequencing the genomes of a half a dozen chimp- or gorilla-infecting malaria parasites provided a clearer picture of Plasmodium falciparum evolution.
A phylogenetic analysis of green-blooded lizards find the trait likely arose more than once, Reuters reports.
An analysis of more than 1,000 Neisseria gonorrhoeae genomes provided insights into antibiotic resistance patterns and related genomic features.
With genome-wide association study data, researchers saw enrichment for schizophrenia-linked SNPs in human-specific differentially methylated regions.
Dramatic genetic diversity in Mycobacterium leprae isolates from medieval Europe could point to a long history or potential origins on the continent.
Sometimes genetic tests give inconclusive results and provide little reassurance to patients, the Associated Press reports.
Vox wonders whether gene-editing crops will be viewed similarly as genetically modified organisms of if people will give them a try.
In Science this week: research regulation and reporting requirement reform, and more.
With H3Africa, Charles Rotimi has been working to bolster the representation of African participants and African researchers in genomics, Newsweek reports. | <urn:uuid:4f06522c-4b52-4a78-9587-669f42982818> | 2.65625 | 402 | Content Listing | Science & Tech. | 6.093626 | 95,645,752 |
ALL >> Business >> View Article
Asteroid Clay Is A Better Space Radiation Shield Than Aluminium
Total Articles: 181
Space travel Two words that make most of us jump up with joy. Turns out Star Trek and Stargate fans might only have to wait a few decades before they can start thinking about traveling to distant ‘lands’. One of the biggest stumbling blocks to space travel is radiation poisoning, and protecting the human body in outer space for long periods of time seems to be impossible at this moment. Researchers, however, are trying to change that by researching new radiation shielding materials.
And as it turns out, those massive asteroids floating through space could end up being the very things that save the human body during space travel. Researchers now believe that the clay extracted from these asteroids could be used to shield astronauts from celestial radiation during deep space missions.
Cosmic radiation is one of the biggest risks associated with traveling into space for extended periods of time, and one of the biggest hindrances to outlandish projects such as a journey to Mars or settlements on the moon. Studies even suggested that without access to radiation shielding materials, explorers would get exposed to a lifetime’s dose of radiation on a single trip to Mars.
According to Daniel Britt from the University of Central Florida, aluminum shields are currently used to protect astronauts from radiation during short missions, but these shields would be too expensive for a longer journey. To spend more time on the moon or to really make a trip to Mars possible, we need to use materials found in space, says Britt.
Paul Van Susante from Michigan Technological University confirms Britt’s theory. “Eventually everything should be able to be produced off Earth if any serious size outpost, base or colony is to be considered.”
Experts believe that the asteroids commonly found in outer space could now be the answer to our search for radiation shielding materials. The clay found in these asteroids is rich in hydrogen, making it one of the most effective shielding materials available. Britt and his fellow researchers also discovered that this clay is about 10% more effective in stopping high-energy charged particles emitted by the sun and other cosmic bodies when compared to aluminum.
The technology to mine this clay under zero gravity situations still doesn’t exist, but researchers are optimistic that we should come up with solutions to such problems soon. One of the proposed solutions is to separate the clay using massive magnets.
We’ll simply have to wait for the right radiation shielding materials to come around, be rest assured that space travel is no longer a dream, but a distant reality.
About Author :
Steven J. Stanek usually writes articles and blogs related to industrial Mechanism and Products, In this article he writes about radiation shielding and radiation shielding materials. He has been vehemently writing articles for ecomass.com
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11. Professionally Expert Technician Of Air Condition
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13. How Does Advertising Use Your Imagination?
14. Export Compliance Needs – What People Should Do?
Author: Fred Danny
15. Hair Removal Products & Epilators Review
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The .Net Common Language Specifications
In an object-oriented environment such as C# and the .Net platform, everything is an object. Once an object is created it needs to be able to communicate or interact with other objects, and the object may need to be manipulated.
These other objects may have been created in a different language, for example, C++. Other languages such as C++ define data types differently (a good example is a string, which in C++ is a pointer to a null-terminated character array). If you were to pass a string to that external method you would need to convert your C# string object into a pointer to an array of characters which has been terminated with a null character.
This approach can get complicated, and sometimes many type conversions are required. This not only leads to messy code but also causes an unwanted performance overhead and a lapse in concentration by the programmer can lead to unwanted memory leaks and unstable applications.
Common Type System
The .Net platform overcomes this problem by implementing the Common Type System (CTS). The Common Type System means that every language in .Net uses the same data types (or objects). When you declare a string in C# you are creating an instance of a string class. When you define a string in Visual Basic, you create an instance of the same string class, thus when you pass parameters between languages there is no longer any requirement to convert data types.
In the .Net framework types are split into two different categories: value types and reference types.
A value type directly contains its data. A variable of type int contains a value (e.g. 12345) and only a value. Each variable of a value type has its own copy of the data. An operation on one variable does not affect another. Value types are stored in a memory location known as the stack.
Reference types contain a reference, or memory location, of their data. The data is stored as an object on the heap. Unlike value types, two or more reference types can point to the same memory location, thus an operation on one variable can affect another. Reference types are instantiated with the new keyword.
Base Class Library
Another feature of the Common Language Specifications is that of the Base Class Library. The Base Class Library provides a common set of classes that all .Net languages can utilise. These classes range from a standard Windows form class to classes for temperature, coordinates, data access, XML parsers and so on.
The Base Class Library is divided up into namespaces so that they are easily navigable. For example, the SqlConnection class is located in the
System.Data.SqlClient namespace. By using this namespace C#, VB, C++ J# and so on can all interact with the same SqlConnection class, all access the same properties and methods.
Last updated on: Friday 23rd June 2017
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UMass Boston scientists predict heat, sea level rise increase for city of Boston
More severe storms, higher coastal waters, and extreme heat waves are coming to Boston in the near future. Mayor Marty Walsh’s administration plans to prepare the city for climate change using scientific projections compiled by a team of scientists from across the region. This group, led by School for the Environment Associate Professor of Hydrology Ellen Douglas and Professor of Climate Adaptation Paul Kirshen brought together experts to focus on sea level rise, coastal storms, extreme precipitation and extreme temperature projections for the Boston region.
In a new report for Climate Ready Boston, the teams led by Douglas and Kirshen provided a scientific consensus that will be used to inform long term planning for the City of Boston. The study’s key findings include:
Sea level rise is an increasing problem:
- By 2050, sea level rise in Boston will likely be between 8 and 18 inches. The worst case scenario could mean 30 inches of sea level rise by 2050.
- By 2100, sea level rise will likely be between 2.5 and 7.4 feet. The worst case projection suggests that number could be as high as 10 feet.
Temperatures will be higher on average, with more heat waves:
- Between 1981 and 2010, the average summer temperature in Boston was 69 degrees. By 2050 the average could be 76 degrees, and by 2100 the average could be 84 degrees.
- Between 1971 and 2000 there were, on average, 11 days per year over 90 degrees. By 2030 there could be as many as 40 days per year over 90 degrees, and 90 days (three months) by 2070.
Extreme storms will become even more extreme:
- From 1958 to 2010 there was a nearly 70% increase in the amount of precipitation that fell on the days with the heaviest precipitation. That trend is expected to continue.
The findings in the report are summarized in a document on the Climate Ready Boston website.
Whether or not the worst case scenarios come true is dependent on greenhouse gas emissions. Higher emissions will create higher seas, climbing temperatures, and more extreme weather. But even with lowered emissions, some sea level rise and temperature increases are expected. The Walsh administration plans to use the information in this study to determine how city neighborhoods and citywide infrastructure systems can be prepared to withstand the impacts of climate change.
“It is important to understand that the emissions choices we make today have a huge impact on our climate later in the century,” said Douglas.
Climate Ready Boston is currently focusing on assessing vulnerabilities within the city based on this data. Professor Kirshen is part of that project team as well. The results of the vulnerability assessment will be released this fall. | <urn:uuid:d95415f9-33b0-496a-b9a2-a921596fb99f> | 3.140625 | 557 | News (Org.) | Science & Tech. | 46.854885 | 95,645,801 |
The term ‘green’ is nowadays widely used (and misused) in connection with many types of technologies. If a technology is ‘green’ it usually means that the technology requires less non-renewable energy sources than other alternatives. However, other parameters need to be considered as well, such as sustainability, recycling potential, treatment capacity and potential, conservation of ecosystems, etc. In this paper the energy requirements and nutrient recycling potential of constructed wetlands and wastewater aquaculture facilities are compared with that of conventional wastewater treatment technologies. The energy requirements of constructed wetlands are very low, but if significant reuse of nutrients is included (aquaculture), the energy requirements increase significantly and usually beyond the energy equivalent of the biomass produced. This is especially true in cold temperate climates where the aquaculture systems need to be housed in heated greenhouses and artificial light must be provided to secure operation throughout the year. In countries where fresh water itself is a limiting resource and where the economic capability may limit the use of artificial fertilisers, the reuse potential of wastewater may be more important. The potential for sustainable cropping of the plant biomass is excellent in tropical wetlands as the plants have a high productivity and a continuous growing season. In order to evaluate in more detail the ‘greenness’ of the different wastewater treatment technologies, the life-cycle approach might be applied. However, because constructed wetlands, besides the water quality improvement function, perform a multitude of other functions such as biodiversity, habitat, climatic, hydrological and public use functions, methodologies need to be developed to evaluate these functions and to weigh them in relation to the water quality issues.
Research Article|August 01 1999
Hans Brix; How ‘Green’ Are Aquaculture, Constructed Wetlands and Conventional Wastewater Treatment Systems?. Water Sci Technol 1 August 1999; 40 (3): 45–50. doi: https://doi.org/10.2166/wst.1999.0133
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The axiom of choice is the most esoteric math concept you are likely to encounter. You might think it has no relevance to computing, but you would be wrong.
A Programmers Guide To Theory
- What Is Computable?
- Finite State Machines
- What is a Turing Machine?
- Computational Complexity
- Non-computable numbers*
- The Transfinite
- Axiom Of Choice
- Lambda Calculus
- Grammar and Torture*
- Reverse Polish Notation - RPN
- Information Theory
- Kolmogorov Complexity*
- Introduction to Boolean Logic*
- Confronting The Unprovable - Gödel And All That*
- The Programmer's Guide to Chaos*
- The Programmer's Guide to Fractals*
*To be revised
Before we get started, I need to say that this isn't a rigorous mathematical exposition of the axiom of choice. What it is attempting to do is to give the idea of the "problem" to a non-mathematician, i.e. an average programmer. I also need to add that while there is nothing much about the axiom of choice that a practical programmer needs to know to actually get on with programming it, it does have connections with computer science and computability. The axiom of choice may not be a particularly practical sort of mathematical concern, but it is fascinating and it is controversial.
The axiom of choice was introduced by Ernst Zermelo in 1904 to prove what seems a very reasonable theorem. In set theory you often find that theorems that seem to state the obvious actually turn out to be very difficult to prove. In this case the idea that needed a proof was the "obvious" fact that every set can be well ordered. That is, there is an order relation that can be applied to the elements so that every subset has a least element under the order. This is Zermelo's well-ordering theorem. To prove that this is the case Zermelo had to invent the axiom of choice.
It now forms one of the axioms of Zermelo-Fraenkel set theory which is, roughly speaking, the theory that most would recognize as standard set theory. There are a lot of mathematical results that depend on the axiom of choice, but notice it is an axiom and not a deduction. That is, despite attempts to prove it from simpler axioms, no proof has ever been produced.
Mathematicians generally distinguish between Zermelo-Fraenkel set theory without the axiom of choice and a bigger theory where more things can be proved with the axiom of choice.
More cartoon fun at xkcd a webcomic of romance,sarcasm, math, and language
So exactly what is the axiom of choice - it turns out to be surprisingly simple and if you read the cartoon caption you will find that it tells you nearly everything you need to know:
"The axiom of choice allow you to select one element from each set in a collection"
- yes, it really is that simple.
A countable collection of sets is just an enumeration of sets Si for a range of values of i. The axiom of choice says that for each and every i you can pick an element from the set Si. It is so obvious that it hardly seems worth stating as an axiom - but it has a hidden depth.
Another way of formulating the axiom of choice is to say that for any collection of sets there exists a choice function f which selects one element from each set, i.e. f(Si) is an element of Si.
Notice that if you have a collection of sets that comes with a natural choice function then you don't need the axiom of choice. The fact you have an explicit choice function means that you have a mechanism for picking one element for each set. The axiom of choice is a sort of reassurance that even if you don't have an explicit choice function one exists - you just don't know what it is.
Another way to look at this is that the axiom of choice says that a collection of sets for which there is no choice function doesn't exist.
To Infinity And...
So where is this hidden depth that makes this obvious axiom so controversial?
The answer is, and nearly always is in these cases, infinity.
If you have a finite collection of sets then you can prove that there is a choice function by induction - and you don't need the axiom of choice as it is a theorem of standard set theory.
Things start to get a little strange when we work with infinite collections of sets. In this case, even if the collection is a countable infinity of sets, you cannot prove that there is a choice function for any arbitrary collection and hence you do need the axiom of choice. That is, to make set theory carry on working you have to assume that there is a choice function in all cases.
In the case where you have a non-countable infinity of sets then things are more obviously difficult. Some non-countable collections do have obvious choice functions and others don't.
This only way to see what the difficulties are is to look at some simple examples.
First consider the collection of all closed finite intervals of the reals i.e. intervals like the set of points x satisfying a ≤ x ≤ b or [a,b] in the usual notation. This is an infinite and uncountable collection of sets but there is an obvious choice function. All you have to is define F([a,b]) as the mid point of the interval. Given you have found a choice function there is no need to invoke the axiom of choice.
Now consider a collection of sets that sounds innocent enough - the collection of all subsets of the reals. It is clear that you can't use the mid-point of each subset as a choice function because not every subset would have a mid-point. You need to think of this collection of subsets as including sets that are arbitrary collections of points. Any rule that you invent for picking a point is bound to encounter sets that don't have a point with that property (note; this isn't a rigorous argument).
Now you can start to see the difficulty in supplying a choice function. No matter what algorithmic formulation you invent some sub-sets just wont have a point that satisfies the specification. You cannot for example use the smallest value in the sub-set to pick a point because open sets don't necessarily have a smallest value using the usual < relationship.
So now the real problem is made clear - this is a problem to do with computability and this is why it is relevant to computer science. If there is no choice function for the collection of all subsets of the reals then the axiom of choice fails and so do all of the theorems that are proven using it.
The axiom of choice simply asserts that there is such a function - it doesn't tell you how to find it.
At the moment it looks as if the weight of mathematical opinion is that we can't find a choice function for the totality of sub-sets of the reals even though the axiom of choice insists that one exists.
So this is a collection of sets where proof by intimidation (see the cartoon) simply wouldn't be practical.
Choice And Computability
If this sounds familiar from what you know of computer science then it should.
The axiom of choice is roughly speaking asserting that the choice function is computable or realizable or whatever you want to call it even if we don't know what it is.
In many cases where something is non-computable we can blame it on the fact that there aren't enough programs to go around. For example, there are only a countable number of programs but there are an uncountable number of real numbers - hence the majority of real numbers aren't computable.
In this case though the problem seems to be that the variability of the sub-sets is such that there isn't sufficient regularity for a program to specify one point in each subset. You might think that the solution is to allow computable functions that return an arbitrary point in the set but it could be that there are sets so complex that there is no formal rule that can pick such a point out. For example consider a set that is composed of just non-computable numbers - how can the choice function return one of them?
When you realize the connection between the axiom of choice and computability it seems less obvious that you can always exercise an arbitrary choice.
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A phreatomagmatic eruption ends when the water supply is exhausted, and not, as in most other eruptions when the magma stops rising. The development of an explosive surge is dependent on the magma coming into contact with water and forming a phreatomagmatic eruption. Water for a phreatomagmatic eruption could come from the harbors, rivers, streams, subsurface aquifers or from sediments at the surface. Several theories have been written as to the exact mechanism of its formation. The most common is the theory of explosive thermal contraction of particles under rapid cooling from contact with water. In many cases the water is supplied by the sea, for example Surtsey. In other cases the water may be present in a lake or Caldera-lake, for example Santorini where the phreatomagmatic component of the Minoan eruption was a result of both a lake and later the sea.
There have also been examples of interaction between magma and water in an aquifer, many of the cinder cones on Tenerife are believed to be phreatomagmatic because of these circumstances. The other competing theory is based on fuel-coolant reactions, which have been modeled for the nuclear industry. Under this theory the magma (in this case the fuel) fragments upon contact with a coolant (the sea, a lake or aquifer), the propagating stress waves and thermal contraction widening cracks and increasing the interaction surface area leading to explosively rapid cooling rates. The two mechanisms proposed are very similar and the reality is most likely a combination of both. | <urn:uuid:105d3bcd-b954-407e-944c-0333b28bfeb1> | 3.65625 | 326 | Knowledge Article | Science & Tech. | 28.817987 | 95,645,864 |
Is it possible to excite a photon? Or bring it to a higher electronvolt?
In the case of massive particles, what would it mean to "excite" one?
I mean in detail - not just to give it more energy.
Then try to see how that could relate to photons.
The words "excite", or "bring to higher level" suggests the existence of levels in the first place, that is, you need a quantized degree of freedom. One way to create this situation for photons is to place them inside a cavity where only certain fequencies/energy levels are allowed. In this case, photons can occupy higher or lower levels yes, and you can talk about excitation.
@Zargon: interesting ... so what happens to the photons at the cavity walls? Isn't there a chance of being absorbed by the wall? Or were you thinking of some other way to restrict the allowed frequencies?
Lets say you have a photon in some well-defined quantum state in such a cavity.
How would you excite it to the next state? Wouldn't you have to annihilate it and introduce a new photon?
if you add a magnetic field to the well would the photon get excited and move to a higher energy state ?
The simple answer is NO. A photon is created due to some event such as a particle interaction, etc., and immediately starts traveling at c with a well defined energy given by E=fh. That's about all you're gonna do with that particluar photon. If you want a photon with a higher energy, you're gonna have to create another photon somehow.
Now you may say, what about when a light ray hits a surface and refracts or changes direction, doesn't its energy change? Or what happens when it hits a prism? The answer to that is that the abovementioned effects are due to the incident photons of white light hitting an object which absorbs, destroys, and re-creates or re-radiates a new photon at a different (or perhaps the same) energy.
Well, you could introduce a blueshift by running towards the source of the light...that's about all I can think up.
That's an interesting question, we can constrain the paths and energies of protons and electrons,etc. in particle accelerators with magnetic fields, would the same be true for photons? My guess is no, but I'm willing to be pursuaded...
I mean, it seems as though gravity can alter the direction and energy of a photon, so maybe I was wrong with my earlier statements.
gravity alters spacetime the photon is still moving in a straight line with the same energy level just that straight line is spacetime curved.
Yeah but...if you shine a flashlight down a well the energy of the light increases the closer you get to the center of the Earth.
Yeah your right I forgot the energy gained from blueshift.
"..if you shine a flashlight down a well the energy of the light increases the closer you get to the center of the Earth....
yes! some details below....
just change the size of the cavity or the potential...
classical analogy: change the fixed points of a vibrating string and it has a different resonant frequency....
another way: drop a photon into a gravity well:
1: A hydrogen atom is lowered into a deep gravity well. Then a photon of visible light is dropped onto the atom, which becomes ionized, although visible light does not normally ionize hydrogen. That happened because the field that keeps the atom together weakened as the atom was lowered.
PeterDonis: No, it happened because the photon was blueshifted as it dropped into the gravity well. A visible light photon emitted locally, at the same altitude as the atom, won't ionize it, so the field of the atom is not "weakened" at all according to local measurements. The difference that lowering the atom gently means that it is at rest deeper inside the well, so it "sees" the blueshift of the photon. To see why that's important, consider an alternate experiment where you let both a hydrogen atom and a visible light photon free-fall into the gravity well, in such a way that they meet up somewhere much deeper into the well than where you released them (you time the release of the atom and the photon from your much higher altitude to ensure this). Will the photon ionize the atom? No, because the atom is not at rest in the field; it is falling inward at a high speed, so there is a large Doppler redshift when it absorbs the photon that cancels the gravitational blueshift.
That just changes the normal modes - it does not change the energy-level of the photons already in it.
I guess I could be wrong - see post #4 for questions arising from the concept, and posts #6&7 for clarification.
The magnetic field is photons. So this question is talking about photon-photon interactions, or, what we used to think of as a photon interacting with a free field.
iirc the Feynman Diagrams sum to zero.
If I have a charged particle confined to a potential well, then change the width of the well by some means, then changing the width does not automatically change the energy eigen-state of the particle does it? Wouldn't the situation be more like making the energy of the particle uncertain - (represented as a superposition of eigenstates of the new potential) requiring a measurement of some kind to establish it?
I think it does affect energy...for example:
I think you guys are making this too hard --- the best way to excite a photon is to show it a really sexy electron !
Wikipedia is not that great a reference - and that quote is does not actually contradict what I've been trying to say. You also have not shown how this model takes into account the other comments and questions I have referenced. Have you done the math?
The particle-in-a-box model can be solved analytically fersure - but it is not a good model of actual physical systems. It is especially problematic for light, since you have to figure out what the box is made out of that would confine a single photon without it annihilating at the walls. When it comes to energy eigenstate transitions, you still have to figure how that would come about. i.e. what would be the physical process that changes the width of such a strange box? Not everything describable in math is physically possible.
You can confine a photon gas in a box though.
This uses a model where photons are constantly being annihilated and created.
In this case, you can raise the mean and total energy of the system by changing the width of the container. But what is it that happens to individual photons?
You could be imagining a single photon bouncing between ideal, perfectly reflecting, walls . In which case, the photon is being annihilated at each wall, and then a new one is created. (Though there is some philosophical hair-splitting over this point.) It is possible to arrange for the photon thus created to be a higher frequency than the one annihilated. I would assert that this process does not well fit the concept of "exciting a photon": it kinda means that it is the same photon that has more energy like an excited electron-in-a-box is the same electron.
For a single particle in a box, when you make the box smaller, the energy eigenstates raise in value, and so does the expectation value of a measurement of energy of the system. The particle, however, is not in a single energy eigenstate until a measurement of energy has been made. You can figure out the odds by expanding the initial eigenstate wave-function in terms of eigenstates of the final potential.
So the process would involve two steps - making the box smaller, and then measuring the energy level. For a perfectly reflecting box of one photon (as discussed) how would you (or the system) conduct that measurement without annihilating the photon?
see this example for what happens when you change the width of a confining potential.
The author has the potential increasing in width, and finesses the system so there is an eigenstate in the final system with the same energy as the ground state of the initial system. As an exercise, do the problem the other way around - making the box smaller.
You realize that reflection, at the photon level, is described using creation and annihilation operators right? The law of reflection is only obeyed on average and all that?
(In fact D Simanek has a pmm puzzle using the idea of a photon bouncing between perfect reflectors.)
@phinds +1 that! I have been resisting the pun from the start :)
No, it are humans that are ill-informed, not nature nor the physics are bizzare.
The "quantum profile" of the hydrogen atom can also be solved analytically, which is seemingly a miracle since 70% (is that figure right?) of the universe is hydrogen. Of course, you get to helium and above, or maybe even deuterium, and you're forced to use the Runge-kutta matlab function and solve these problem numerically. In any case, doesn't anybody think its weird how electron orbitals manifest from the Shrodinger equation? It is bizzare, solving the radial and azimuthal equations yield these weird Legendre polynomials, and we infer the quantum numbers from co-efficients in the Euler exponents. I mean, who'd of thunk?
Even then - "particle in a box" is not a good model for the H atom.
74% yes. I don't know about "miracle" but it is certainly useful.
Helium is sort of doable - it's a common exercise for senior undergrads.
This allows for approximations for hydrogenic and helium-oid atoms ... varying success.
Anything else does, indeed, require a numerical method. Matlab is common for a first pass - but you end up learning to program in something like c++ since the inner workings of matlab are a secret. But this is for another thread. "Rung-Kutta" tends to imply a shooting method - there are faster methods .. also for another thread.
+1. I noticed that too - "common sense" is what tells you the World is flat.
To which I must add the best (not much competition) line ever in a numerical methods book ("Numerical Recipes" series), summing up the authors' recommendation for partial differential equations: "shoot first, then relax".
It is not that easy for photons. For photons, the particle in a box problem is realized by microcavities or micropillars. This way the box is realized by highly reflective mirrors like distributed Bragg reflectors, effectively placed half a target wavelength away from each other. However, the reflectivity of this kind of mirror cannot be broadband and you get some narrow wavelength range of good reflectivity around the target wavelength.
If you now change the resonance wavelength by changing the distance of the mirrors, the microcavity becomes a low-reflectivity cavity for the prior resonance wavelength and photons inside will simply escape. Experiments like that have been done with acoustic strain pulses and semiconductor microcavities.
I get the idea of your objection....I think your points better than mine....
I have simply taken such explanations as I posted at face value...never really questioned them....I just took the view such an explanation is a simple extension of quantum confinement...
I just skimmed Albert Messiah QUANTUM MECHANICS Chapter 3 regarding one dimensional quantized systems....[which I had in mind when I posted] to criticize my own post:
....there are no one dimensional systems,
....If the potential well is finite, there is a finite probability of the wave function NOT being reflected,
....If the potential well is infinite there is complete reflection and the energy levels are quantized....and we can't do infinite anything.
So what about the PeterDonis explanation I posted...??
As a related suggestion, how about collapsing space-time to 'rev up a photon'??
[If cosmological distance expansion redshifts radiation, seems like cosmological contraction should blue-shift??]
In another discussion:
Brian Cox claims changing the energy level of a particle changes the energy level of all its counterparts...So maybe all I have to do to excite all photons is to turn on a light bulb?
Issue: Brian Cox on TV claimed…..no two electrons anywhere in the universe can be in precisely the same energy levels…. claimed to be changing the state of all electrons in the universe by warming up a diamond….a consequence of the Pauli exclusion principle proven in 1967.
Synopsis [one view] :
Without knowledge of Pauli's Exclusion Principle one might expect electrons arbitrarily far away from one another to have identical energy levels. Pauli, however, shows that is simply impossible.
Likely too theoretical considering the OP question, but not so easily dismissed as I thought before the discussion.
That's hogwash Naty, didn't you read that long thread on PF where Cox actually got into the argument himself? I don't buy his argument for a second...that a hydrogen atom somewhere in the andromeda galaxy has its electron energy levels arranged differently than a hydrogen atom planted in my left cheek. This would require an impossibly absurd number of energy levels in the tiny space of a given hydrogen atom (on the order of 10^-12m).
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A canyon or gorge is a deep cleft between escarpments or cliffs resulting from weathering and ... The processes of weathering and erosion will form canyons when the river's headwaters and estuary are at .... the Yarlung Tsangpo River in Tibet, is regarded by some as the deepest canyon in the world at 5,500 m ( 18,000 ft).
These natural formations are created by rivers running deep within the Earth.
May 20, 2011 ... The largest canyon in the solar system isn't found on Earth. ... Weathering and erosion also contribute to the formation of canyons. In winter ...
A canyon is a deep and narrow valley consisting of steep sides created by weathering and erosion by rivers, wind, rain and tectonic activity.
Feb 26, 2013 ... The Grand Canyon is a rich, geologic landscape formed over millions of years by a combination of natural forces. ... Live Science · Planet Earth.
Jun 20, 2010 ... Some of the most spectacular canyons on Earth and Mars were probably formed in the geologic blink of an eye, suggests a new study that ...
Jan 26, 2014 ... The world famous Grand Canyon, which snakes through the ... through the deep incision, which records nearly two billion years of Earth history.
Oct 12, 2016 ... A new model of canyon-forming floods from UMass Amherst and CalTech researchers suggests that deep canyons can be formed in bedrock ...
Oct 12, 2016 ... Modeling Floods That Formed Canyons on Earth and Mars. UMass Amherst and CalTech study offers new model of megaflood-carved ... | <urn:uuid:292e47d7-9129-4e95-9082-0e5f03a6008f> | 3.859375 | 342 | Content Listing | Science & Tech. | 77.063918 | 95,645,905 |
Appendix from Dynamics and locomotion of flexible foils in a frictional environment
2018-01-04T12:13:04Z (GMT) by
Over the past few decades, oscillating flexible foils have been used to study the physics of organismal propulsion in different fluid environments. Here, we extend this work to a study of flexible foils in a frictional environment. When the foil is oscillated by heaving at one end but is not free to locomote, the dynamics change from periodic to non-periodic and chaotic as the heaving amplitude increases or the bending rigidity decreases. For friction coefficients lying in a certain range, the transition passes through a sequence of <i>N</i>-periodic and asymmetric states before reaching chaotic dynamics. Resonant peaks are damped and shifted by friction and large heaving amplitudes, leading to bistable states. When the foil is free to locomote, the horizontal motion smoothes the resonant behaviours. For moderate frictional coefficients, steady but slow locomotion is obtained. For large transverse friction and small tangential friction corresponding to wheeled snake robots, faster locomotion is obtained. Travelling wave motions arise spontaneously, and move with horizontal speeds that scale as transverse friction coefficient to the coefficient to and input power that scales as the transverse friction coefficient to the power 5/12. These scalings are consistent with a boundary layer form of the solutions near the foil's leading edge. | <urn:uuid:2f5d2695-19ea-4eda-a89a-4c797af54ba0> | 2.734375 | 301 | Academic Writing | Science & Tech. | 30.077211 | 95,645,914 |
ERN Item Type:
- Classroom Activities
Acids are substances that have a sour taste and strong smell. Lemon juice and vinegar are common acids. Acid rain is formed when pollution inthe air mixes with the rain and falls to the ground. In this activity, vinegar will represent acid rain, and an antacid tablet will represent a marble statue in a city park. Both the antacid tablet and marble are made of the same chemical: calcium carbonate. | <urn:uuid:d52edc55-a274-43a6-923b-fb45be47474c> | 3.28125 | 93 | Tutorial | Science & Tech. | 46.098 | 95,645,973 |
phototropism defined in 1951 yearphototropism - phototropism (HELIOTROPISM);
phototropism - Tropism in which stimulus is light. E.g. bending of stems of indoor plants towards a window. Brought about by increased elongation of cells in growth region at tip of stem on shaded side. Generally accepted that effect is due to greater concentration of auxin on that side than on side facing light but some recent evidence suggests as the explanation asymmetric distribution of some cofactor that influences auxin effect.
near phototropism in Knolik
definition of word "phototropism" was readed 787 times | <urn:uuid:083f098b-7494-4387-adb5-ade3a08e9d6b> | 3.171875 | 136 | Knowledge Article | Science & Tech. | 32.75 | 95,645,982 |
The effects of light and moisture on the early establishment of four canopy tree seedlings were studied from October 1999 to August 2000. The study was undertaken in a primary dry forest in the Hellshire Hills protected area, Jamaica with rainfall for the year totaling 650 mm most of which fell during the 6-month long rainy season. Seeds of Calyptranthes pallens, Eugenia sp., Hypelate trifolia and Metopium brownii were collected 1 month prior to the peak in the rainy season and planted in a nursery constructed within a cleared area of the forest according to a split-plot design which consisted of three blocks each containing three main treatment plots (no shading, partial shading and heavy shading) with each main plot being sub-divided into two subplots (regular watering and no watering). Seedling germination was prompt with shading having a more positive significant effect on seed germination than watering. Seedling mortality was high during the dry season particularly after the first month following a significant reduction in rainfall but seedling survival stabilised at the start of the wet season. Seedling survival was lower in un-shaded than shaded plots and in the shaded plots, survival was lower in partially shaded plots than in heavily shaded plots. Water supplement prolonged the survival of all individuals regardless of shading. Seedling size was positively affected by shading with seedlings within the partially shaded plots attaining the highest basal diameter while seedlings in the heavily shaded plots were the tallest. Water supplement also positively affected seedling size. High light levels during the wet period improved seedling growth but significantly increased seedling mortality during the dry season for all species. With respect to seedling response, M. brownii had the highest germination percentage and production but was most sensitive to drought. C. pallens had the highest survival and produced the smallest individuals. However, Eugenia sp. had the highest number of seedlings surviving at the end of the experimental period, and showed the lowest drought sensitivity. © 2003 Elsevier Science B.V. All rights reserved.
Mendeley saves you time finding and organizing research
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Science says: The lunar surface is much more awesome than you think it is.
Here are ten heavenly bodies, ranked according to their general awesomeness:
While this list might not be 100 percent scientifically accurate ... still, poor Moon. It lacks the intrigue of the sun, the mystery of Mars, even the lonely metaphor of the wandering satellite. While the moon once represented humanity's wildest technological aspirations, it's now taken a "been there, done that" quality. The last time a human set foot on the lunar surface was December. Of 1972.
A team of scientists thinks the moon deserves another shot. In a paper soon to be published in the journal Planetary and Space Science, Ian Crawford, of Birkbeck College in London, and his colleagues lay out a detailed case for amped-up lunar exploration.
First, they argue, the moon is actually a really good place to learn about the earth. "As the Earth's closest celestial neighbor the Moon retains a unique record of the inner Solar System environment under which life evolved on our planet," they write. The moon could house as many as 200 kilograms of ancient earth matter per lunar kilometer -- an odd but rich source of data about our planet. The moon's surface also likely contains a record of solar wind flux, solar luminosity, and galactic cosmic rays as they interacted throughout the history of the solar system -- which could offer clues not only into the environment of the solar system itself, but also into the past habitability of earth.
The moon might also be an ideal spot for making astronomical observations. While we've gotten really good at making those observations from earth, across the electromagnetic spectrum, there's one section that's been inaccessible to us: the ultra low-frequency radio waves. And the dark side of the moon offers the perfect, silent spot to make measurements -- specifically, the authors suggest, with a radio telescope that could be thousands of kilometers in diameter. "The low-frequency universe is the last uncharted part of the electromagnetic spectrum," they note, "and a lunar infrastructure would greatly benefit its exploration."
Most controversially, however, the team makes the specific argument for humans -- not just robots -- exploring the moon. For one thing, they say, it would give us valuable insight into the effects of low gravity on the human body. That line of argument, however, is less convincing. As Tech Review points out, "a similar argument is often made about humans on the International Space Station but this work has produced little, if any, benefit for the rest of us. (Indeed the presence of humans is what makes the International Space Station profoundly unsuitable for most micro gravity experiments and astronomical observations.)" For now, we can make a case for walking on the moon. It just might not be human feet taking the steps.
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Plant cells communicate via microscopic channels called plasmodesmata that are embedded in their cell walls. For the stem cells in the plants' growing tips, called "meristems," the plasmodesmata are lifelines, allowing nutrients and genetic instructions for growth to flow in.
Developmental and environmental cues trigger changes in the structure of the tiny channels, thereby altering the flow of traffic through them. The genes and molecular pathways of the plant cell that respond to these cues, and the mechanisms that control channel structure and cell-to-cell traffic are, however, mostly unknown.
To identify these genes, a team of researchers led by Professor David Jackson, Ph.D., at Cold Spring Harbor Laboratory (CSHL), devised a method to find mutant cells whose channels were blocked to traffic. The experiments have revealed a gene called GAT1 (pronounced gate-one), which instructs cells to produce an enzyme found only in meristems, the stem-cell rich tip of the plant where new growth takes place. The enzyme improves the flow of traffic through plasmodesmata by acting as an antioxidant, a type of molecule that relieves cellular stress.
"This discovery is one of the first examples of using genetics to understand how plant cells communicate through plasmodesmata," says Jackson, whose lab at CSHL is devoted to the study of plant genetics. "Our study suggests a mechanism through which plant cells can adjust trafficking in these channels through the various stages of development." The team's findings will be published in the Feb 17th issue of Proceedings of the National Academy of Sciences.
GAT1 keeps callose at bay
As plants develop, growth signals and environmental cues such as damage or stress trigger overproduction of a substance called callose. Although callose is a normal structural component of cell walls in plants, excess callose accumulates and forms obstructive clumps that plug the plasmodesmata and impede the flow of traffic through the channels.
Restricting flow can be beneficial in some instances, such as when damaged parts need to be closed off or virus-infected cells need to be quarantined. But flow blockage can be fatal too, especially when it happens in meristems.
"Meristems that are blocked and thereby starved of nutrients won't give rise to daughter cells and spawn new organs, thus stunting the plant's growth," explains Jackson. "What we've found now is probably the mechanism that normally prevents blockages from occurring in these stem cells."
Jackson's team has found that plants stave off callose accumulation and keep the channels open by turning on the GAT1 gene in their stem cells. Seeds in which this gene failed to work were observed by the CSHL team to give rise to seedlings that barely survived more than two weeks, despite forming intact roots and an intact phloem – the main transport artery that carries nutrients and other supplies to the meristems.
The mutants even had intact meristems that had developed the required numbers of transport channels. These channels, however, were functionally defective, as the pile-up of callose narrowed them, making the passage of nutrient molecules impossible. The CSHL scientists were able to reverse this defect by re-introducing a functional GAT1 gene into mutant plants. When the GAT1 gene was turned on, the production and accumulation of callose decreased.
GAT1 counters oxidative stress
One of the distress signals that spur cells to synthesize callose are oxygen free radicals – the same cell-damaging molecules that have gained notoriety as a major cause of cell death and aging. In mutant plant seeds that lack a functional GAT1 gene, stem cells brim with high levels of these free radicals and other toxic ions, collectively known as reactive oxygen species (ROS).
This ROS threat, according to Jackson's team, is normally counter-balanced by GAT1. The CSHL scientists found that this gene encodes an enzyme called thioredoxin-m3, which they found only in the meristems, as well as in the tissues dedicated to transport. There, it acts as an antioxidant – a molecule that slows or prevents the formation of ROS.
Thioredoxin-m3 is a member of a large family of small proteins that are ubiquitous in plant and animal cells, and are biochemical workhorses that meddle in multiple metabolic processes. They consequently have an impact on numerous cellular events, including stress responses, cell death, and gene expression.
In addition to protecting plants against oxidative damage, as the CSHL scientists have shown, thioredoxin-m3 and its cousins might have other specific functions in different stages of plant development in different tissues and under different physiological conditions. Knowing the diverse functions of these proteins may help in engineering plants that are drought- and heat-tolerant.
Discovering the role of thioredozin-m3 in cell-cell traffic within meristems has already provided one such pay-off. Jackson's group found that increasing the expression of GAT1 in plants caused them to take longer to produce flowers and enter senescence – the period of old age. "People are generally interested in controlling senescence for commercial purposes such as growing plants that last longer or flowers that stay fresh longer," explains Jackson. "Our results suggest that manipulating GAT1 expression in plants can be one way of achieving this," he says.
Hema Bashyam | EurekAlert!
Further reports about: > CSHL > GAT1 > biochemical workhorses that > callose > cell death > cell walls > cell-to-cell traffic > cellular stress > environmental cues > free radicals > genetic instructions > meristems > microscopic channels > molecular pathways > nutrients > plant cell > plasmodesmata > stem cells > stress trigger overproduction > virus-infected cells
Barium ruthenate: A high-yield, easy-to-handle perovskite catalyst for the oxidation of sulfides
16.07.2018 | Tokyo Institute of Technology
The secret sulfate code that lets the bad Tau in
16.07.2018 | American Society for Biochemistry and Molecular Biology
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
16.07.2018 | Physics and Astronomy
16.07.2018 | Life Sciences
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Описание книги The Art of Unit Testing: With Examples in .Net:
Unit testing, done right, can mean the difference between a failed project and a successful one, between a maintainable code base and a code base that no one dares touch, and between getting home at 2 AM or getting home in time for dinner, even before a release deadline.
The Art of Unit Testing builds on top of what's already been written about this important topic. It guides you step by step from simple tests to tests that are maintainable, readable, and trustworthy. It covers advanced subjects like mocks, stubs, and frameworks such as Typemock Isolator and Rhino Mocks. And you'll learn about advanced test patterns and organization, working with legacy code and even untestable code. The book discusses tools you need when testing databases and other technologies. It's written for .NET developers but others will also benefit from this book.
Table of Contents:
The basics of unit testing
A first unit test
Using stubs to break dependencies
Interaction testing using mock objects
Isolation (mock object) frameworks
Test hierarchies and organization
The pillars of good tests
Integrating unit testing into the organization
Working with legacy code
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In 2009, the DOE had funded the creation of 46 EFRCs to lay the scientific groundwork necessary to meet the global need for abundant, clean and economical energy.
Only about half of the 46 centers were funded in the second round, although 10 new ones were added for a total of 32 awards. Those 32 projects were selected from more than 200 proposals.
Capturing the sun’s energy output
The centers selected for the second round of funding will help lay the scientific groundwork for fundamental advances in solar energy, electrical energy storage, carbon capture and sequestration, materials and chemistry by design, biosciences and extreme environments.
PARC’s goals are to understand the basic scientific principles that govern solar energy collection by photosynthetic organisms and to use this knowledge to fabricate more efficient biohybrid and bio-inspired systems to drive chemical processes or generate photocurrent.
Natural photosynthetic systems consist of two parts: antennas that collect solar photons and reaction centers that transform the easily dissipated light energy into the more durable form of charge separation that can then be used to do work.
The scientists are broadening their goals for PARC 2. PARC 1’s goal was to increase the efficiency of light harvesting antennas. In PARC 2, the scientists will continue their work on the antennas but will also start looking at energy delivery at the reaction center interface and reaction center design.
“It’s really gratifying to see the high level of support that DOE has provided for solar-related research,” said Jonathan Lindsey, a PARC principal investigator from North Carolina State University.
“Young students coming into my laboratory are very excited and motivated by the chance to make a real contribution to something that they see as being a very important part of their lives and their own children’s lives,” said Christopher Moser, a PARC principal investigator from the University of Pennsylvania.
Washington University is the host and administrative center for PARC, whose partners include investigators from the Los Alamos National Laboratory, North Carolina State University, Northwestern University, Oak Ridge National Laboratory, Sandia National Laboratories, University of California-Riverside, University of Glasgow, University of New Mexico, University of Pennsylvania, University of Sheffield in England, Princeton University, University of Illinois at Urbana-Champaign and Penn State.
Source: Washington University
ST Staff Writers
This post was prepared by Solar Thermal Magazine staff. | <urn:uuid:d41f6aef-bcac-42e0-a6e3-6658d08763c3> | 3.109375 | 499 | News (Org.) | Science & Tech. | 12.240713 | 95,646,020 |
Nagoya University-led team of physicists use a synchrotron radiation X-ray source to probe a so-called 'structure-less' transition and develop a new understanding of molecular conductors
We normally associate conduction of electricity with metals. However, some of the high measured conductivities are found in certain organic molecular crystals. Metallic, semiconducting and even superconducting properties can be achieved in these materials, which have interested scientists for decades.
Electron density distribution of the frontier orbital of a TMTTF molecule. Electrons of the constituent atoms of the molecule can be considered as either core electrons, which have no interactions with the surroundings, or electrons of frontier orbitals, which determine many physical properties of the molecule. We succeeded in visualizing the frontier molecular orbital distribution of a TMTTF by precise structural analysis using a core differential Fourier synthesis (CDFS) method.
Credit: Shunsuke Kitou
Changing temperature or pressure causes phase transitions in the crystal structure of molecular conductors and their related conduction properties. Scientists can usually determine the crystal structure using X-ray diffraction. However, structural change accompanying phase transition in a particular organic crystal (TMTTF)2PF6 has defied examination for almost 40 years.
Now, a research team at Nagoya University has finally explained the mysterious structural changes of this phase transition and its related electronic behavior.
"Researchers have questioned that the TMTTF (tetramethyltetrathiafulvalene) salt shows a charge disproportionation transition at 67 Kelvin but no relevant changes in its crystal structure. This transition is a long-standing mystery known as a 'structure-less transition'," explains lead author Shunsuke Kitou.
TMTTF is an organic donor that is also found in some organic superconductors. Just above the temperature that liquid nitrogen freezes, this organic crystal behaves as an insulator. But as the temperature is lowered it goes through electronic and magnetic changes.
Until now these structural changes were too small to measure directly. Using the X-ray source at SPring8, in Hyogo Japan, the team could precisely determine the crystal structure at each stage. The structure-less transition involves the formation of a two-dimensional Wigner crystal, based on a change in the distribution pattern of electrons in the structure.
"We have precisely characterized the subtle structural changes across this transition and finally provided a complete physical explanation for the apparent unchanging structure of this organic conductor," says group leader Hiroshi Sawa. "Accurate crystallographic data is still lacking for many organic conductors and we hope our findings will inspire other groups to look more closely at these systems. A better understanding of their complex behavior could pave the way to a range of new functional electronic materials."
The article, "Successive Dimensional Transition in (TMTTF)2PF6 Revealed by Synchrotron X-ray Diffraction," was published in Physical Review Letters. https:/
Koomi Sung | EurekAlert!
In borophene, boundaries are no barrier
17.07.2018 | Rice University
Research finds new molecular structures in boron-based nanoclusters
13.07.2018 | Brown University
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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Make sure you have a solid versioning policy in place. You can apply a version stamp using the AssemblyVersion attribute at compile time, for example:
It’s usually best to apply the same version number to all the assemblies in an application during the build process.
2. Give Assemblies Strong Names
An assembly is the smallest unit of versioning, security, deployment, version control and reusability of code in .NET. Each assembly contains:
- Assembly Identity information (name, version, etc.)
- Manifest and metadata information
- MSIL code
- Type and security information
An assembly with a strong name can be uniquely identified by a combination of its assembly version, culture information, and a digital signature.
You can create a strong name for your assembly using the strong name utility (sn.exe) provided by the .NET framework. The utility requires you to provide the name of a strong name key file as a parameter. The resulting file is called a “strong-named” file. You can use the sn.exe tool from the command line to create a strong-named key file as follows:
sn --k MyCompany.snk
When you execute the preceding command, you’ll see the output shown in Figure 1.
|Figure 1. Creating a Strong-Named Key File: Running the <i>sn.exe</i> file from the command line as shown creates a strong-named key file.|
When you create a project in Visual Studio, you’ll see a default file called AssemblyInfo.cs that you can use to specify the related attributes. Here is how you can specify the strong name information in the AssemblyInfo.cs file.
[assembly: AssemblyCulture("")] [assembly: AssemblyVersion("22.214.171.124")] [assembly: AssemblyKeyFile("MyCompany.snk")]
3. Obfuscate Your Assemblies
It’s good practice to obfuscate your assemblies before you deploy them; obfuscation makes assemblies more difficult to decompile, and impedes reverse-engineering efforts, thus protecting your source code to some degree from potential threats. In addition, obfuscation reduces the size of your assemblies; thereby boosting the application’s performance. You can learn more about obfuscation here.
4. Deploy Shared Assemblies to the GAC
You should deploy assemblies used by multiple applications to the Global Assembly Cache (commonly known as the GAC), which allows them to be shared by all applications that use the assembly. Deploying an assembly to the GAC improves its load performance compared to assemblies not located in the GAC. Strong-named assemblies load faster from the GAC because they’re verified at install time rather than at runtime—the .NET framework skips verification at runtime for GAC-loaded assemblies. The runtime always checks strong-named assemblies to verify their integrity. .NET refuses to load assemblies that are not trusted or that may have been tampered with. Note that you must provide a strong name for assemblies you want to install in the GAC.
You place an assembly into the GAC using the GACUtil tool. The following command places MyProject.dll into the GAC, thus making it globally accessible.
GacUtil /i MyProject.dll
To uninstall the assembly from the GAC, you would use:
GacUtil /u MyProject.dll
Note that you can even make your strong-named assembly globally accessible without placing it in the GAC. For this, you need to deploy your assembly using the XCOPY command. | <urn:uuid:8707145c-9781-4d68-a218-dcd10c9f87bf> | 2.578125 | 754 | Tutorial | Software Dev. | 45.088475 | 95,646,029 |
‘One of the largest human experiments in history’ was conducted on unsuspecting residents of San Francisco.
By Strange Sounds
This is a crazy story; one that seems like it must be a conspiracy theory. But the core of this incredible tale is documented and true.
One fact many may not know about San Francisco’s fog is that in 1950, the US military conducted a test to see whether it could be used to help spread a biological weapon in a “simulated germ-warfare attack.”
And this was just the start of many such tests around the country that would go on in secret for years.
The test – one of the largest human experiments in history – was a success. But it was also one of the largest offenses of the Nuremberg Code since its inception, as it stipulates that “voluntary, informed consent” is required for research participants, and that experiments that might lead to death or disabling injury are unacceptable.
The unsuspecting residents of San Francisco certainly could not consent to the military’s germ-warfare test, and there’s good evidence that it could have caused the death of at least one resident of the city, Edward Nevin, and hospitalized 10 others.
A successful biological warfare attack
It all began in late September 1950, when over a few days, a Navy vessel used giant hoses to spray a fog of two kinds of bacteria, Serratia marcescens and Bacillus globigii — both believed at the time to be harmless — out into the fog, where they disappeared and spread over the city.
It was noted that a successful BW [biological warfare]attack on this area can be launched from the sea, and that effective dosages can be produced over relatively large areas.
Successful indeed, according to Leonard Cole, the director of the Terror Medicine and Security Program at Rutgers New Jersey Medical School. His book, “Clouds of Secrecy: The Army’s Germ Warfare Tests Over Populated Areas documents the military’s secret bioweapon tests over populated areas:
Nearly all of San Francisco received 500 particle minutes per liter. In other words, nearly every one of the 800,000 people in San Francisco exposed to the cloud at normal breathing rate (10 liters per minute) inhaled 5,000 or more particles per minute during the several hours that they remained airborne.
This was among the first but far from the last of these sorts of tests.
Tests included the large-scale releases of bacteria in the New York City subway system, on the Pennsylvania Turnpike, and in National Airport just outside Washington, DC. Over the next 20 years, the military would conduct 239 “germ-warfare” tests over populated areas, according to news reports from the 1970s.
In a 1994 congressional testimony, Cole said that none of this had been revealed to the public until a 1976 newspaper story revealed the story of a few of the first experiments — though at least a Senate subcommittee had heard testimony about experiments in New York City in 1975, according to a 1995 Newsday report.
A mysterious death
When Edward Nevin III, the grandson of the Edward Nevin who died in 1950, read about one of those early tests in San Francisco, he connected the story to his grandfather’s death from a mysterious bacterial infection. He began to try to convince the government to reveal more data about these experiments. In 1977, they released a report detailing more of that activity.
In 1950, the first Edward Nevin had been recovering from a prostate surgery when he suddenly fell ill with a severe urinary-tract infection containing Serratia marcescens, the theoretically harmless bacterium that’s known for turning bread red in color. The bacteria had reportedly never been found in the hospital before and was rare in the Bay Area (and in California in general). The bacteria spread to Nevin’s heart and he died a few weeks later.
Another 10 patients showed up in the hospital over the next few months, all with pneumonia symptoms and the odd presence of Serratia marcescens. They all recovered.
Nevin’s grandson tried to sue the government for wrongful death, but the court held that the government was immune to a lawsuit for negligence and that they were justified in conducting tests without subjects’ knowledge. The Army stated that infections must have occurred inside the hospital and the US Attorney argued that they had to conduct tests in a populated area to see how a biological agent would affect that area.
In 2005, the FDA stated that “Serratia marcescens bacteria … can cause serious, life-threatening illness in patients with compromised immune systems.” The bacteria has shown up in a few other Bay Area health crises since the 1950s, leading to some speculation that the original spraying could have established a new microbial population in the area.
As shown in the below video, it was also the same in the UK:
While Nevin lost his lawsuit, he said afterward, as quoted by Cole, “At least we are all aware of what can happen, even in this country … I just hope the story won’t be forgotten.”
This article (Biological Warfare: ‘One of the largest human experiments in history’ was conducted on unsuspecting residents of San Francisco) was originally published on Strange Sounds and syndicated by The Event Chronicle. | <urn:uuid:508174ad-7ddf-4254-b1cb-2702577e5010> | 2.84375 | 1,115 | News Article | Science & Tech. | 36.157052 | 95,646,065 |
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dimple is a library to aid in the creation of standard business visualisations based on d3.js.
You must include d3.js in any pages in which you wish to use dimple.
The dimple api is tested against Firefox, Chrome, Safari and IE9. It's browser support is largely inherited from d3 so using it on IE8 and earlier will be difficult/impossible.
If you only intend to make use of dimple in your web page just include the following script references:
<script src="http://d3js.org/d3.v3.min.js"></script> <script src="http://dimplejs.org/dist/dimple.v2.0.0.min.js"></script>
You can then access the API from the dimple namespace.
The dimple api uses a handful of fundamental objects for chart creation. This is a deviation from the functional chaining pattern of d3, however it should be familiar to those of you coming from many other commercial charting applications.
dimple.chart - The chart object is fundamental to all dimple visualisations. It constructs and combines the other objects.
dimple.axis - A chart object can contain any number of axis objects. An x axis determines horizontal positioning, a y axis determines vertical positioning, other axis types are also possible. There must be at least an x axis and a y axis for the chart to render, however they may be hidden.
dimple.series - A chart object can contain any number of series objects. A series links axes together with data and renders a graphic.
dimple.storyboard - A chart object can have a single storyboard which animates the chart over another dimension.
CSS and dimple
To fit with its ethos of simplicity dimple has its own style rules which are dynamically added to elements, meaning you can get a nice looking chart with no CSS at all. However, we realise that CSS support is one of the most awesome things about d3 so if you want to use it on a dimple chart, just set the noFormats property of the chart object to
true. This will prevent dimple from adding any style elements to the DOM. The dimple drawing algorithm also decorates everything with a number of extra classes based on the data, allowing you to pick out individual series or data points for formatting.
Scope of Properties and Methods
To allow you to tinker with the inner workings, dimple exposes all its methods and properties. However it is highly recommended that you stick to the stuff that's supposed to be public, therefore any properties or methods which do not form part of the official public API will be prefixed with an underscore (_). These will not be documented here or necessarily supported in future releases so using them is very much an extreme sport.
Some functions with very contained usage have a double underscore prefix (__) these should definitely not be used widely.
To demonstrate the brevity and simplicity of dimple once the data has been loaded and the svg created (see full examples for this bit - it's not difficult), the code behind a stacked bar chart of Brand Volumes over Regions looks like this:
var chart = new dimple.chart(svg, data); chart.addCategoryAxis("x", "Region"); chart.addMeasureAxis("y", "Volume"); chart.addSeries("Brand", dimple.plot.bar); chart.draw();
To see this and some other examples in action please check the examples page.
If you want to contribute to the dimple code-base we recommend that you begin by [forking this repository] (/PMSI-AlignAlytics/dimple/fork "Fork Me").
Next you will need to install node.js, if you are not already using it. This is used for grunt (explained below) as well as running a web server for tests and hosting the examples in development.
The final tool required is grunt which we use to combine the source js files into a single distribution file. Grunt is installed from the node.js shell using the command:
npm install -g grunt-cli
Having installed grunt CLI, navigate to the root of the dimple repository in the node.js shell and install dependencies (defined in package.json) with the folowing command:
This should install all prerequisites for development. Dimple uses continuous testing through grunt karma. When developing dimple run:
This puts karma in continuous test mode. It will run in the background and immediately raise an exception if you save a source file which breaks a unit test.
To view an example and examine the affect of your changes you can launch a node.js web server by running the following from the command prompt:
This will initialise a node.js webserver on port 3000. You can therefore access your pages under
http://localhost:3000/ for example
http://localhost:3000/examples/bars_horizontal.html. For any problems with this process, or any more advanced operations, please consult the websites of the relevant products.
Installing the examples
If you do not wish to develop dimple but do want to play with the examples on your local machine, you must serve them over a web server. There are many options available for doing this and if you have a preferred approach, please use it, otherwise I recommend node.js as a quick and free solution.
Begin by installing node.js from here.
Next, download the dimple example code (and other files) from here. You will need to extract the contents of the zip file into a folder of your choice. In this example I'll assume it is
Now launch your operating system's command line and navigate to your new folder. For example if you are using Windows - launch cmd.exe and type:
Next you need to install all the application dependencies, which is as simple as typing the following in the command prompt:
This should automatically install everything you need (Thanks node.js!). Then run the following:
Which will launch a node express web server on port 3000, whose configuration is in the app.js file. This won't actually do anything visible, the cursor will go to the next line and happily blink there forever.
Now you can browse the examples in your favourite browser. So for the horizontal bars example use the following URL:
This will serve the example file from your hard drive located at:
All of the examples on the dimple site will be located in this folder and can be accessed similarly. | <urn:uuid:3be17b5b-b7df-476f-ab4e-ed782ab22db0> | 2.8125 | 1,404 | Documentation | Software Dev. | 56.832513 | 95,646,066 |
2. Polar Covalent Bonds: Acids and Bases. Based on McMurry’s Organic Chemistry , 7 th edition. Why this chapter?. Description of basic ways chemists account for chemical reactivity. Establish foundation for understanding specific reactions discussed in subsequent chapters.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Based on McMurry’s Organic Chemistry, 7th edition
• Atomic sulfur has 6 valence electrons.
Dimethyl suloxide sulfur has only 5.
• It has lost an electron and has positive charge.
• Oxygen atom in DMSO has gained electron and has (-) charge.
• Occur between polar molecules as a result of electrostatic interactions
• Forces can be attractive of repulsive depending on orientation of the
• Occur between all neighboring molecules and arise because the electron distribution within molecules that are constantly changing
• Most important noncovalent interaction in biological molecules
• Forces are result of attractive interaction between a hydrogen bonded to an electronegative O or N atom and an unshared electron pair on another O or N atom | <urn:uuid:dbc35cf6-6960-445f-895c-d51470bf5d41> | 3.578125 | 281 | Truncated | Science & Tech. | 25.869038 | 95,646,073 |
There is a common question of “why is geothermal energy considered a renewable resource?”. Well, talking about renewable resources, usually geothermal energy is not as popular as solar energy or wind energy. However, certainly this geothermal energy is in there whenever we talk about renewable resources. This is the indication that geothermal energy is indeed considered as renewable resources.
The real question is: why? Why is geothermal energy considered as renewable resources? Below is the answer for you.
1. Why is Geothermal Energy Renewable?
The term renewable means something that can be renewed or will never ever run out. Geothermal energy has its source in the center of the earth. Geothermal energy is using the thermal heat of the earth. The heat of the earth is kept to generate power.
So, is geothermal energy renewable or nonrenewable?
Because the source of energy is the earth itself, it is obvious that geothermal energy is renewable. The earth will never go away or extinct. If someday it does, we all extinct as well.
This is the basic reason why geothermal energy is considered to be one of the renewable resources along with solar power or wind power. Geothermal energy can also be used to create geothermal electricity, heating system, cooling system, and help the transportation system.
2. Geothermal Energy and Its Benefits for the People
Geothermal, that originates from the Greek words “geo” which means earth and “thermos” which means heat, is basically the heat of the earth. There are many things that we can do with the heat of the earth including creating geothermal energy. Geothermal energy that is used is coming from the core of the earth, approximately 4,000 miles down the earth. The temperature can reach 9,000 Fahrenheit. That is why it can be used as a great source of energy.
The benefits of using geothermal energy for the people is because it is more earth-friendly and it reduces the energy loads from the regular electricity. In other words, it is more affordable and more powerful. People can use it for years and even forever without worrying the energy to run out.
Now that we know why is geothermal energy considered as renewable resources, we can definitely use it as a new energy source. It will help us do greater thing to keep the sustainability of the earth itself. Geothermal energy will always be there now, tomorrow, and even forever. It will never run out forever.You can download all 0 of Why is Geothermal Energy Considered as Renewable Resources? image to your device by right clicking image and then save image as. Do not forget to click share if you love with this photo. | <urn:uuid:806d9290-cfed-49d0-97c8-f6d03c5f2e92> | 3.28125 | 557 | Knowledge Article | Science & Tech. | 46.267008 | 95,646,119 |
Smart, Self-Healing Hydrogels
A smart, self-healing hydrogel developed at UC San Diego is made of linked chains of polymer molecules that are similar to the soft tissues of the body. "Dangling side chain" molecules add the capability of self-repair when the body of the hydrogel is cut or damaged.
(Smart, self-healing hydrogels)
"Self-healing is one of the most fundamental properties of living tissues that allows them to sustain repeated damage," says Varghese. "Being bioengineers, one question that repeatedly appeared before us was if one could mimic self-healing in synthetic, tissue-like materials such as hydrogels. The benefits of creating such an aqueous self-healing material would be far-reaching in medicine and engineering."
To design the side chain molecules of the hydrogel that would enable rapid self-healing, Varghese and her collaborators performed computer simulations of the hydrogel network. The simulations revealed that the ability of the hydrogel to self-heal depended critically on the length of the side chain molecules, or fingers, and that hydrogels having an optimal length of side chain molecules exhibited the strongest self-healing. When two cylindrical pieces of gels featuring these optimized fingers were placed together in an acidic solution, they stuck together instantly. Varghese's lab further found that by simply adjusting the solution's pH levels up or down, the pieces weld (low pH) and separate (high pH) very easily. The process was successfully repeated numerous times without any reduction in the weld strength.
Self-healing materials have a long history in science fiction; in his 1951 story Asteroid of Fear, sf great Raymond Z. Gallun, we encounter a unique plastic that can repair itself:
But the wide roof was all the way up, now—intact. It made a great, squarish bubble, the skin of which [a 'transparent, wire-strengthened plastic '] was specially treated to stop the hard and dangerous part of the ultra-violet rays of the sun, and also the lethal portion of the cosmic rays. It even had an inter-skin layer of gum that could seal the punctures that grain-of-sand-sized meteors might make.
(Read more about self-healing plastic)
Scroll down for more stories in the same category. (Story submitted 5/13/2012)
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is devoted to the creative science inventions and ideas of sf authors. Look for
the Invention Category that interests
you, the Glossary, the Invention
Timeline, or see what's New.
Ontario Starts Guaranteed Minimum Income
'Earned by just being born.'
Is There Life In Outer Space? Will We Recognize It?
'The antennae of the Life Detector atop the OP swept back and forth...'
Space Traumapod For Surgery In Spacecraft
' It was a ... coffin, form-fitted to Nessus himself...'
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'The hypercard is an avatar of sorts.'
A Space Ship On My Back
''Darn clever, these suits,' he murmured.'
Biomind AI Doctor Mops Floor With Human Doctors
'My aim was just not to lose by too much.' - Human Physician participant.
Fuli Bad Dog Robot Is 'Auspicious Raccoon Dog' Bot
Bad dog, Fuli. Bad dog.
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'A worker replaced by a nubot... had to be compensated.'
You'll Regrow That Limb, One Day
'... forcing the energy transfer which allowed him to regrow his lost fingers.'
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'The car surged and lifted, clearing its top by a negligible margin.'
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Science fiction authors are serious about sleep, too.
Real-Life Macau or Ghost In The Shell
Art imitates life imitates art.
Has Climate Change Already Been Solved By Aliens?
'I had explained," said Nessus, "that our civilisation was dying in its own waste heat.'
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Just what we need! Lots of spare parts.
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More SF in the News Stories
More Beyond Technovelgy science news stories | <urn:uuid:2d8e8ff1-376e-432e-99f2-3c63632b96ce> | 3.078125 | 1,244 | Content Listing | Science & Tech. | 57.462571 | 95,646,130 |
Earth might be our Solar System’s last habitable planet after all
By Mike Wehner
Earth is a fantastic place to be right now, but that won’t always be the case. If humanity doesn’t manage to completely destroy the planet for ourselves before our sun begins to grow noticeably warmer, its intense heat will make our world uninhabitable on its own. Scientists have long theorized that when the sun grows hot enough to cause serious problems for Earth, some of the icy moons in our Solar System might warm up enough to support life. Unfortunately, new research is casting some serious doubt on that idea, and suggests that finding a new place to live after Earth might force us to venture much farther.
The new research effort, led by Jun Yang of Peking University, was published in Nature Geoscience. Utilized computer models to simulate how a star like our own sun would affect icy planets as it warms. Rather than melting the surface of Jupiter’s moon Europa or Saturn’s Enceladus into oceans which could support the development of life, the simulations point to a much different result.
The data shows that the amount of energy that a world such as Europa would need in order to begin the melting process would be so great that, once the melting began, the moon would likely already be at the tipping point of “too hot.” Essentially, the heat required to break it out of its “snowball” state would also create a devastating greenhouse effect and water loss, skipping a habitable window entirely.
“Europa and Enceladus will have no habitable period,” Yang and his colleagues predict. “They will transit to a moist or runaway greenhouse state when the Sun becomes a red giant in six to seven billion years, at which time the stellar flux at the location of Europa will reach the snowball-melting threshold.”
Read more here:: BGR Social | <urn:uuid:c3579ad7-a052-40e3-bd7b-efc5c650cabb> | 3.609375 | 401 | Truncated | Science & Tech. | 40.695828 | 95,646,135 |
The aurorae on Mars were discovered in 2004 using the SPICAM ultraviolet and infrared atmospheric spectrometer on board Mars Express. They are a powerful tool with which scientists can investigate the composition and structure of the Red Planet’s atmosphere.
Now Francois Leblanc, from the Service d’Aéronomie, IPSL/CNRS, France and colleagues have announced the results of coordinated observation campaigns using SPICAM, the MARSIS sub-surface sounding radar altimeter’s radar, and the energetic neutral atoms analyser, ASPERA’s electron spectrometer on Mars Express.
They have observed nine new auroral emission events, which have allowed them to make the first crude map of auroral activity on Mars. They see that the aurorae seem to be located near regions where the martian magnetic field is the strongest. MARSIS had previously observed higher-than-expected electrons in similar regions. This suggests, although it does not prove, that the magnetic fields help to create the aurorae.
On Earth, aurorae are more commonly known as the northern and southern lights. They are confined to the polar regions and shine brightly at visible as well as ultraviolet wavelengths. The existence of similar aurorae is well known on the giant planets of the Solar System. They occur wherever a planet’s magnetic field channels electrically charged particles into the atmosphere.
In all of these planets, the magnetic fields are large-scale structures generated deep in the interior of the planet. Mars lacks such a large-scale internal mechanism. Instead, it just generates small pockets of magnetism where areas of rocks in the crust of Mars are themselves magnetic. This results in many magnetic pole-type regions all over Mars.
The aurorae are caused by charged particles, in this case most probably electrons, colliding with molecules in the atmosphere. The electrons almost certainly come from the Sun, which constantly blows out electrically charged particles into space. Known as the solar wind, this constant stream of particles provides the source of electrons to generate the aurorae, as suggested by MARSIS and ASPERA.
But how the electrons are accelerated to sufficiently high energies to spark aurorae on Mars remains a mystery. “It may be that magnetic fields on Mars connect with the solar wind, providing a road for the electrons to travel along,” says Leblanc.
Any future astronauts expecting a spectacular light show, similar to aurorae on Earth, may be in for a disappointment. “We’re not sure whether the aurorae will be bright enough to be observed at visible wavelengths,” says Leblanc.
This is because the molecules responsible for the visible light show on Earth – molecular and atomic oxygen and molecular nitrogen – are not abundant enough in the martian atmosphere. SPICAM is designed to work at ultraviolet wavelengths and cannot see whether visible light is being emitted as well.
Nevertheless, there is plenty of work for the scientists to do. “There's now a large domain of physics that we have to explore in order to understand the aurorae on Mars. Thanks to Mars Express we have a lot of very good measurements to work with,” says Leblanc.
Agustin Chicarro | alfa
What happens when we heat the atomic lattice of a magnet all of a sudden?
17.07.2018 | Forschungsverbund Berlin
Subaru Telescope helps pinpoint origin of ultra-high energy neutrino
16.07.2018 | National Institutes of Natural Sciences
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
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"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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A View from Emerging Technology from the arXiv
The Puzzle of Particle Jets and Blast Waves
Nobody knows why particles form into jets when caught in a blast wave, but a new video casts some light on the conundrum.
One of the best ways to understand fluid motion is to record a video of the action. That has created some friendly rivalry between fluid dynamicists who compete to produce the best films of their work.
Each year, the fluid dynamics division of the American Physical Society hosts a Gallery of Fluid Motion at its annual meeting and invites researchers to submit their best reels. These guys store their videos on the arXiv, making them fair game for this blog.
It’s that time of year again, so I’m keeping my eye out for the best videos submitted to this year’s Gallery of Fluid Motion.
Today’s pick describes an interesting puzzle that emerges from the way substances packed around explosives behave when a detonation occurs. David Frost at McGill University in Canada and a few buddies, packed millions of tiny glass spheres just a120 micrometres across around 28g ball of C4 and videoed the shape they formed as the detonation occurred using a 10,000 fps camera.
It turns out, the glass spheres form into fairly evenly-spaced jets as they are caught up in the blast wave (see picture above, video links below). Apparently, these jets are a common feature of the explosive dispersal of particles. For example, when the C4 is surrounded by water, even more jets form but these dissipate more quickly.
But curiously, Frost and co say that the highest number of jets occur when the C4 is surrounded by a mixture of water and glass beads. This, they say, is entirely unexpected.
Certain factors are known to influence ‘particle jetting’, as this phenomenon is called; things like particle size as well as the size and geometry of the charge.
But here’s the thing: nobody really knows why the jets form at all.
An interesting mystery described in a cool video, perhaps something for a computer modeller with some spare time to take on.
Couldn't make it to EmTech Next to meet experts in AI, Robotics and the Economy?Go behind the scenes and check out our video | <urn:uuid:c30f4b63-9e5c-4d15-96c1-db28902ab338> | 2.828125 | 479 | News Article | Science & Tech. | 49.875058 | 95,646,138 |
The Atlantic meridional overturning circulation (AMOC) is a system of ocean currents that has an essential role in Earth’s climate, redistributing heat and influencing the carbon cycle1, 2. The AMOC has been shown to be weakening in recent years1; this decline may reflect decadal-scale variability in convection in the Labrador Sea, but short observational datasets preclude a longer-term perspective on the modern state and variability of Labrador Sea convection and the AMOC1, 3,4,5. Here we provide several lines of palaeo-oceanographic evidence that Labrador Sea deep convection and the AMOC have been anomalously weak over the past 150 years or so (since the end of the Little Ice Age, LIA, approximately ad 1850) compared with the preceding 1,500 years. Our palaeoclimate reconstructions indicate that the transition occurred either as a predominantly abrupt shift towards the end of the LIA, or as a more gradual, continued decline over the past 150 years; this ambiguity probably arises from non-AMOC influences on the various proxies or from the different sensitivities of these proxies to individual components of the AMOC. We suggest that enhanced freshwater fluxes from the Arctic and Nordic seas towards the end of the LIA—sourced from melting glaciers and thickened sea ice that developed earlier in the LIA—weakened Labrador Sea convection and the AMOC. The lack of a subsequent recovery may have resulted from hysteresis or from twentieth-century melting of the Greenland Ice Sheet6. Our results suggest that recent decadal variability in Labrador Sea convection and the AMOC has occurred during an atypical, weak background state. Future work should aim to constrain the roles of internal climate variability and early anthropogenic forcing in the AMOC weakening described here.
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We thank E. Roosen for help with core sampling; H. Abrams, S. O’Keefe, K. Pietro, L. Owen and F. Pallottino for assistance in processing sediment samples; K. Green for faunal counts in core 10MC; M. Andrews at the UK Met Office for providing the GC2 model data; and S. Rahmstorf for useful suggestions. This work made use of the high-performance computing facilities of ARCHER, which was provided by the University of Edinburgh. Funding was provided from: National Science Foundation (NSF) grant OCE-1304291 to D.W.O., D.J.R.T. and L.D.K.; National Environment Research Council (NERC) Project DYNAMOC grant NE/M005127/1 to P.O. and J.I.R.; the NERC’s Long-Term Science, Multi-Centre (LTSM) North Atlantic Climate System Integrated Study (ACSIS) (to J.I.R.); and the Leverhulme Trust and the ATLAS project (to D.J.R.T.). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement 678760 (ATLAS). This paper reflects only the authors’ views and the European Union cannot be held responsible for any use that may be made of the information contained herein.Reviewer information
Nature thanks P. Bakker, S. Rahmstorf, M. Srokosz and the other anonymous reviewer(s) for their contribution to the peer review of this work.
Extended data figures and tables
a, 14C and 210Pb dating. The 14C ages (with 1σ ranges; grey, rejected dates) from planktic foraminifera yield a modern core-top age and indicate an average sedimentation rate over the past 1,000 years of 320 cm kyr−1 (dashed line). The presence throughout the core of abundant lithogenic grains in the >150-μm fraction—along with the coarse sortable-silt mean grain size values—suggests that some reworking of foraminifera has probably occurred, resulting in average 14C ages that may be slightly (around 50 years) older than their final depositional age, consistent with the fact that the 210Pb dates do not splice smoothly into the 14C ages (the 14C ages appear slightly too old). The final age model was therefore based on the 210Pb ages for the past century, and was then simply extrapolated back in time using the linear sedimentation rate of 320 cm kyr−1. Given that none of our findings depend on close age control in the older section of this core (that is, before ad 1880), this uncertainty (with converted 14C ages being about 50 years older than the extrapolated linear age model) does not affect our conclusions. b, Left, the age model for the top 80 cm of core 56JPC is based on 210Pb dating of bulk sediment, using the constant initial concentration (CIC) method (rejecting the date at 47 cm, which probably indicates a burrow). A simple two-segment linear fit to the 210Pb dates is adopted (rather than point-to-point interpolation or a spline) because sedimentological evidence—an abrupt increase in the percentage of coarse fraction at 23 cm depth, not observed elsewhere in the core—is indicative of a step change in the sedimentation rate. Horizontal dashed lines denote the depths of the segments at which the sedimentation rate is inferred to change. Centre, further support for the age model of 56JPC over the past century comes from the down-core abundance profile of spheroidal carbonaceous particles (SCPs, derived from high-temperature fossil fuel combustion, counted as described39), which ramped up from the mid to late 1800s and peaked in the 1950s to 1970s (40 cm to 25 cm) before declining over recent decades, consistent with the 210Pb-based age model. Right, the occurrence of 137Cs in the top 40 cm or so of the core is also consistent with the 210Pb-based age of around 1950 at 40 cm. The age uncertainty (1σ) for the past 60 years of the core is estimated at ±2–3 years. We note that the sediment core top is at 3 cm depth in the core-liner. Source data
a, 14C-based age model, derived from linear interpolation of 14C-dated planktic foraminifera (with 1σ ranges) in sediment core KNR-178-48JPC (used for the DWBCLSW sortable-silt reconstruction), yielding a modern core-top age and an average sedimentation rate of around 50 cm kyr−1. We note that the core top is at 3 cm depth in the core-liner. The inset shows the SCP profile for 48JPC on the basis of the 14C age model, confirming the modern age of the top sediments, with SCPs showing the expected profile—increasing in concentration from the late 1800s onwards, peaking at around 1950 to 1970, and declining afterwards. b, Updated age model for core KNR-158-10MC (after ref. 47; used in Extended Data Fig. 5 examining regional near-surface temperature trends in the Northwest Atlantic during the industrial era), using new 210Pb dating (CIC method) for the top 7 cm and rejecting the anomalously old 14C age at 4 cm depth; the inset shows 210Pb age constraints in the top 8 cm. A single detectable occurrence of 137Cs at 2–2.5 cm (equivalent to 1957 on the 210Pb-based age model) can be linked to the bomb peak at 1963, supporting the age model. Also, SCPs were found in the top 5 cm of this core, confirming the industrial-era age for the top 5 cm; however, the low concentrations of SCPs prevent meaningful interpretation of the down-core trends and are not shown. c, Age model for core OCE-326-MC29B (used for Tsub reconstruction of the Northwest Atlantic shelf): 14C ages of planktic foraminifera (with 1σ ranges), from ref. 48. Support for this age model is provided by the SCP concentrations (inset; this study), which show the expected down-core profile39 when plotted using the 14C ages. 210Pb dating48 also suggests a sedimentation rate of around 120 cm kyr−1 for the uppermost sediments, consistent with the 14C ages and SCP profile. Source data
Locations are shown in Fig. 2b. a–c, Temperature proxy records48,49,50 used for the Northwest Atlantic stack (Emerald Basin, Laurentian Fan and Gulf of St Lawrence), where model studies11, 12 indicate that AMOC weakening results in warming of surface and subsurface waters. d–g, Records used to reconstruct Northeast Atlantic SPG subsurface temperatures: d, Gardar drift51; e, combined South Iceland data (Bjorn drift)52, 53; f, Feni drift54; g, Eastern North Atlantic Central Water (ENACW), largely composed of waters formed in the eastern SPG55, 56. h, The high-resolution alkenone sea-surface temperature (SST) record from the North Iceland shelf57 was not included because it is not located within the open North Atlantic SPG (although it does also show, like the other Northeast Atlantic records, that the lowest temperature of the past 1,600 years occurred during the most recent century). Also shown for reference is the Rahmstorf central SPG SST reconstruction (based largely on terrestrial proxies)6.
Extended Data Fig. 4 Different binning and averaging approaches and the residual temperature signal.
a, b, Stacked, normalized proxy temperature data (Tsub) from the Northwest Atlantic shelf/slope (a) and Northeast Atlantic SPG (b). c, The derived Tsub AMOC proxy, calculated as the numerical difference between the stacks shown in a and b. d, The residual temperature variability in stacks a and b that is not described by the (anti-phased dipole) Tsub AMOC proxy shown in c—that is, the in-phase temperature variability common to both stacks, calculated as the numerical sum of the two stacks (if divided by two, this would be the numerical mean). This represents the inferred non-AMOC-related temperature variability common to both regions, and broadly resembles Northern Hemisphere temperature reconstructions, most notably colder residual temperatures during the LIA, around 1350 to 1850. For a–d, black solid lines and squares represent preferred binning (50 years for 1800–2000; 100 years for 400–1800); green line and symbols, as for preferred binning, but with stacks produced by first binning the proxy data at each site and then averaging these binned site values, as opposed to binning all the proxy data together in one step (the former ensures equal weighting for each site, the latter biases the final result to the higher-resolution records); black dashed lines and symbols, 100-year bins offset by 50 years from the preferred bins; grey lines and symbols, 50-year bins (not shown for c and d); blue lines and symbols; 30-year bins for 1790–2000. Error bars for a–d are ±2 s.e. e–g, As for a–c, except using a Monte Carlo approach and published uncertainties for age assignment and temperature reconstructions; light and dark grey shading represent ±1σ and ±2σ, respectively. h, Jackknife version of c, with each line representing the Tsub AMOC proxy but leaving out one of the individual proxy records each time. Source data
a, Modelled SST difference between a weak (negative) and strong (positive) AMOC58. This pattern is model-dependent, with the study cited here58 chosen because of its good agreement with observations of Gulf Stream variability. The locations of cores used for panel b are shown by black stars. b, Percentage abundances of the polar species N. pachyderma (sinistral) in marine sediment cores from the Northwest Atlantic, as an indicator of near-surface (around 75 m) temperatures. A 15% increase indicates around 1 °C of cooling (we note the reversed y axes). The opposing trends over the past 200 years are consistent with the SST pattern modelled for a weakening of the AMOC, as shown in panel a. Data and age models for the cores are: OCE326-MC2948 using the original 14C dating and as shown in Extended Data Fig. 2; OCE326-MC13 and OCE326-MC2549 using the original 14C age ties at the top and bottom of the core and scaling the intervening sedimentation rate to the percentage of CaCO3 content49, 59, 60; KNR158-MC10, this study, using the age model in Extended Data Fig. 2. Source data
a, Top, Tsub AMOC fingerprint11 obtained using empirical orthogonal function (EOF) analysis of the EN4 dataset (light green, the leading mode (EOF1) of Tsub variability from 1993–2003, as defined by Zhang11, applied to the EN4 data; dark green, the second mode of Tsub variability (EOF2) of the North Atlantic for 1900–2015, equivalent to the EOF1 defined for 1993–2003). No substantial twentieth-century AMOC decline is seen in this observation-based reconstruction. Bottom, instrument-based reanalysis of the ‘cold blob’ central SPG region (red; 3-year (thin line) and 11-year (thick line) smoothing; 47° N to 57° N, 30° W to 45° W) used in the Rahmstorf SST AMOC proxy6. The data are from the HadISST project. The reconstructed central SPG SST bears some resemblance to the Tsub AMOC fingerprint record, which is not unexpected given that the central SPG forms a substantial spatial component of the Tsub fingerprint. No clear decrease is shown in the central SPG SST, and the equivalent Rahmstorf AMOC proxy6 (blue; central SPG minus the Northern Hemisphere (NH) temperature) declines during the twentieth century because of the subtraction of the NH warming trend. b, Reconstructed (predominantly terrestrial-based) AMOC proxy (orange; the temperature difference between the central SPG and the NH) and the central SPG SST reconstruction6 (blue). There is a two-step decline in the AMOC proxy, at 1850–1900 and 1950–2000—the former being mainly the result of a strong cooling of the SPG (which probably weakened northward heat transport, paralleling the weakening shown by our DWBC proxy), and the latter being due mainly to subtraction of the strong NH warming trend, rather than a persistent SPG cooling. Source data
a, b, Climatological surface current direction (in arrows) and speed (shaded, m s−1) obtained from the control simulation with HadGEM3-GC2 and the satellite product OSCAR.
a, Correlation (colour bar) of the vertically averaged ocean density (at 1,000–2,500 m) with the DLSD index (as defined in ref. 4; green box, 1,000–2,500 m average) in a 340-year present-day control run of the HiGEM model (see ref. 36). b, Climatology of the modelled meridional ocean velocity (in m s−1) averaged between 30° N and 35° N, illustrating the modelled position of the DWBC. The y axis shows the water depth in metres. c, Cross-correlations between the modelled average DWBC flow speed in the pink box in panel b and indices of DLSD and AMOC at 45° N (the dashed line omits the Ekman component). We note that the box over which the DWBC flow index in panel c is averaged has changed with respect to Fig. 1, in order to take into account of the fact that the return flow is deeper in the HiGEM model than in HadGEM3-GC2.
The model-based DLSD parameter—proposed in ref. 4 and using the EN4 reanalysis dataset—incorporates a larger area and greater depth range than do instrumental-data-only studies, such as ref. 5, which examines past variability in Labrador Sea convection and focuses on the central Labrador Sea and on depths less than 2,000 m, where most observational data are available. The comparison here of DLSD (purple line, three-year mean) from the EN4 dataset with instrumental data on density changes in the central Labrador Sea at 1,500–1,900 m depth (grey line, annual averages; black line, three-year mean) illustrates that the two parameters show very similar variability. Both are dominated by the density changes caused by deep convection in the Labrador Sea, which can reach down to around 2,000 m. Estimates of uncertainty are discussed in ref. 61. Source data
A direct influence of the changing position of the Gulf Stream on the grain size of our core sites can be ruled out by comparing instrumental records of the Gulf Stream position (red, GSI58) with the down-core sortable-silt (SS) mean grain size data in 56JPC (blue; thicker line is three-point smoothed). There is no clear correlation between these two proxies (bottom). However, there is a coupling between our SS data (which represent inferred DWBCLSW flow speed) and density changes in the deep Labrador Sea (grey, annual; black, three-point smoothed; top panel). The 2σ SS error bar (n = 30) is for the three-point mean. | <urn:uuid:742b9822-d09b-440b-aff0-b9526e8fa8a5> | 2.71875 | 3,809 | Truncated | Science & Tech. | 52.542159 | 95,646,155 |
After completion of its final-design review last year, it is full steam ahead for the construction of the MOONS instrument - the next generation multi-object spectrograph for the VLT. This remarkable instrument will combine for the first time: the 8 m collecting power of the VLT, 1000 optical fibres with individual robotic positioners and both medium- and high-resolution spectral coverage acreoss the wavelength range 0.65μm - 1.8 μm. Such a facility will allow a veritable host of Galactic, Extragalactic and Cosmological questions to be addressed. In this paper we will report on the current status of the instrument, details of the early testing of key components and the major milestones towards its delivery to the telescope.
Additive manufacturing (AM), more commonly known as 3D printing, is a commercially established technology for rapid prototyping and fabrication of bespoke intricate parts. To date, research quality mirror prototypes are being trialled using additive manufacturing, where a high quality reflective surface is created in a post-processing step. One advantage of additive manufacturing for mirror fabrication is the ease to lightweight the structure: the design is no longer confined by traditional machining (mill, drill and lathe) and optimised/innovative structures can be used. The end applications of lightweight AM mirrors are broad; the motivation behind this research is low mass mirrors for space-based astronomical or Earth Observation imaging. An example of a potential application could be within nano-satellites, where volume and mass limits are critical. The research presented in this paper highlights the early stage experimental development in AM mirrors and the future innovative designs which could be applied using AM.
The surface roughness on a diamond-turned AM aluminium (AlSi10Mg) mirror is presented which demonstrates the ability to achieve an average roughness of ~3.6nm root mean square (RMS) measured over a 3 x 3 grid. A Fourier transform of the roughness data is shown which deconvolves the roughness into contributions from the diamond-turning tooling and the AM build layers. In addition, two nickel phosphorus (NiP) coated AlSi10Mg AM mirrors are compared in terms of surface form error; one mirror has a generic sandwich lightweight design at 44% the mass of a solid equivalent, prior to coating and the second mirror was lightweighted further using the finite element analysis tool topology optimisation. The surface form error indicates an improvement in peak-to-valley (PV) from 323nm to 204nm and in RMS from 83nm to 31nm for the generic and optimised lightweighting respectively while demonstrating a weight reduction between the samples of 18%. The paper concludes with a discussion of the breadth of AM design that could be applied to mirror lightweighting in the future, in particular, topology optimisation, tessellating polyhedrons and Voronoi cells are presented.
This paper investigates the potential role of small satellites, specifically those often referred to as CubeSats, in the future of infrared astronomy. Whilst CubeSats are seen as excellent (and inexpensive) ways to demonstrate and improve the readiness of critical (space) technologies of the future they also potentially have a role in solving key astrophysical problems. The pros and cons of such small platforms are considered and evaluated with emphasis on the technological limitations and how these might be improved. Three case studies are presented for applications in the IR region. One of the main challenges of operating in the IR is that the detector invariably needs to be cooled. This is a significant undertaking requiring additional platform volume and power and is one of the major areas of discussion in this paper. Whilst the small aperture on a CubeSat inevitably has limitations both in terms of sensitivity and angular resolution when compared to large ground-based and space-borne telescopes, the prospect of having distributed arrays of tens (perhaps hundreds) of IR-optimised CubeSats in the future offers enormous potential. Finally, we summarise the key technology developments needed to realise the case study missions in the form of a roadmap.
Future X-ray astronomy missions require light-weight thin shells to provide large collecting areas within the weight limits of launch vehicles, whilst still delivering angular resolutions close to that of Chandra (0.5 arc seconds). Additive manufacturing (AM), also known as 3D printing, is a well-established technology with the ability to construct or ‘print’ intricate support structures, which can be both integral and light-weight, and is therefore a candidate technique for producing shells for space-based X-ray telescopes. The work described here is a feasibility study into this technology for precision X-ray optics for astronomy and has been sponsored by the UK Space Agency’s National Space Technology Programme. The goal of the project is to use a series of test samples to trial different materials and processes with the aim of developing a viable path for the production of an X-ray reflecting prototype for astronomical applications. The initial design of an AM prototype X-ray shell is presented with ray-trace modelling and analysis of the X-ray performance. The polishing process may cause print-through from the light-weight support structure on to the reflecting surface. Investigations in to the effect of the print-through on the X-ray performance of the shell are also presented.
Additive manufacturing, more commonly known as 3D printing, has become a commercially established technology for rapid prototyping and the fabrication of bespoke intricate parts. Optical components, such as mirrors and lenses, are now being fabricated via additive manufacturing, where the printed substrate is polished in a post-processing step. One application of additively manufactured optics could be within the astronomical X-ray community, where there is a growing need to demonstrate thin, lightweight, high precision optics for a beyond Chandra style mission. This paper will follow a proof-of-concept investigation, sponsored by the UK Space Agency’s National Space Technology Programme, into the feasibility of applying additive manufacturing in the production of thin, lightweight, precision X-ray optics for astronomy. One of the benefits of additive manufacturing is the ability to construct intricate lightweighting, which can be optimised to minimise weight while ensuring rigidity. This concept of optimised lightweighting will be applied to a series of polished additively manufactured test samples and experimental data from these samples, including an assessment of the optical quality and the magnitude of any print-through, will be presented. In addition, the finite element analysis optimisations of the lightweighting development will be discussed.
The Multi-Object Optical and Near-infrared Spectrograph (MOONS) will cover the Very Large Telescope's (VLT) field of view with 1000 fibres. The fibres will be mounted on fibre positioning units (FPU) implemented as two-DOF robot arms to ensure a homogeneous coverage of the 500 square arcmin field of view. To accurately and fast determine the position of the 1000 fibres a metrology system has been designed. This paper presents the hardware and software design and performance of the metrology system. The metrology system is based on the analysis of images taken by a circular array of 12 cameras located close to the VLTs derotator ring around the Nasmyth focus. The system includes 24 individually adjustable lamps. The fibre positions are measured through dedicated metrology targets mounted on top of the FPUs and fiducial markers connected to the FPU support plate which are imaged at the same time. A flexible pipeline based on VLT standards is used to process the images. The position accuracy was determined to ~5 μm in the central region of the images. Including the outer regions the overall positioning accuracy is ~25 μm. The MOONS metrology system is fully set up with a working prototype. The results in parts of the images are already excellent. By using upcoming hardware and improving the calibration it is expected to fulfil the accuracy requirement over the complete field of view for all metrology cameras. | <urn:uuid:9ac763d3-e301-4d5c-9581-cdae30685016> | 2.546875 | 1,623 | Content Listing | Science & Tech. | 23.009995 | 95,646,158 |
Losing green up the stack
By Steven Powell, email@example.com, 803-777-1923
Fume hoods are an essential feature of many laboratories. They provide an enclosed workspace, typically the size of a large desktop, for mixing chemicals that give off noxious vapors, which are whisked out of the building by the ventilation system.
They’re also massive energy hogs.
“Each hood costs about as much as a house does a year to power,” says chemistry graduate student Andrew Pingitore.
That’s because whatever volume of air that the hood vents out of the building must be equalized by the same amount of fresh air brought into the building. The fresh air must be conditioned to the building’s temperature, and according to a study by Harvard’s Office for Sustainability, the costs for operating a typical hood in one academic research building on their campus was more than $3,000.
What’s more, whoever is using the hood has a lot of control over how much its tally might come to. Most fume hoods have a sash that you can raise or lower as needed to work therein, and when it’s up, the hood is fully open and draws maximum airflow through it. The Harvard study showed that a “Shut the Sash” initiative to encourage lab workers to make it a habit to keep the sash down unless necessary cut the electricity bill per hood from $3,000 to $1,800.
The potential for that kind of savings is what a graduate student organization of polymer and materials scientists, the American Chemical Society Poly/PMSE chapter at USC, had in mind when they kicked off an energy conservation initiative for the Department of Chemistry and Biochemistry on August 29.
The outgoing president, Mitra Ganewatta, convinced the Fisher and VWR reps at the university to sponsor the effort, so the club was able to purchase signs for the department’s labs aimed not just at keeping sashes down, but also saving water and turning off the lights when they’re not in use.
The sponsorship also allowed the team to buy prizes for a departmental conservation competition.
“We’re doing surprise inspections to decide who we think are the most energy-efficient research groups,” says Julia Pribyl, the club’s incoming president.
Given that there are 146 hoods in the Graduate Research Sciences Center alone, with potential yearly savings of $1,200 per hood, the students’ green efforts could make the department itself the biggest winner.
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Most vertebrate olfactory receptor neurons share a common G-protein-coupled pathway for transducing the binding of odorant into depolarization. The depolarization involves 2 currents: an influx of cations (including Ca2+) through cyclic nucleotide-gated channels and a secondary efflux of Cl- through Ca2+-gated Cl- channels. The relation between stimulus strength and receptor current shows positive cooperativity that is attributed to the channel properties. This cooperativity amplifies the responses to sufficiently strong stimuli but reduces sensitivity and dynamic range. The odor response is transient, and prolonged or repeated stimulation causes adaptation and desensitization. At least 10 mechanisms may contribute to termination of the response; several of these result from an increase in intraciliary Ca2+. It is not known to what extent regulation of ionic concentrations in the cilium depends on the dendrite and soma. Although many of the major mechanisms have been identified, odor transduction is not well understood at a quantitative level.
Mendeley saves you time finding and organizing research
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Physics Question #92
Tim Seeburger, a 16 year old male from the Internet asks on November 23, 1999,
How does an analog ammeter works and how could I make one?
viewed 27904 times
An ammeter measures the electrical current in a circuit. It is measured in amperes (amps). The principle of operation of an analog current meter is based on Lorentz Force. Any current carrying conductor produces a magnetic field around it proportional to the amount of current being carried. When you place a current carrying conductor in an externally applied magnetic field (say for example using a permanent magnet) there is an interaction between the field of lines from the P-Magnet and the magnetic field produced by the current carrying conductor. This results in a relative mechanical force between the magnet and the current carrying conductor. If you fix the magnet (mechanically) then the current carrying conductor deflects due to the force. If you fix the current carrying conductor then the magnet moves (or deflects) due to the force. The former case is called a moving coil ammeter and the latter case is called as moving iron (or moving magnet) ammeter. This mechanism was studied and perfected by the French scientist D'Arsonval and he brought out a meter mechanism which is still being used by all analog meters. It is called D'Arsonval movement. Check out this interactive Lorentz Force illustration by Walter Fendt. Here's a YouTube video that shows a simple way to construct an ammeter with a surplus magnet from an old computer hard drive and a small coil of wire.
Add to or comment on this answer using the form below.
Note: All submissions are moderated prior to posting.
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Measurement and Detection of X-Rays
In any application or study of X-rays some method of detection of the X-ray beam will be required. It may be sufficient to detect the existence of a beam or to record its position relative to the incident beam or to some other reference. In such cases qualitative methods are acceptable. On the other hand it may be necessary to know the intensity of the beam either relative to the intensity of other beams or in absolute measure, or again it may be necessary to know the total energy received in the form of X-rays by some object. In such cases, of course, quantitative methods are required.
KeywordsZinc Sulphide Proportional Counter Metallic Silver Silver Halide Straight Line Portion
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- 1.Laughlin, Beattie, Henderson & Harvey. Amr. J. Roentgenol. Radium Therapy NucL Med., 70, 294 (1953).Google Scholar
- 2.Thomas, Electronics—Section 15, The Nuclear Handbook (ed.Frisch), Newnes (1958).Google Scholar
- 3.Yarwood, Electricity, Magnetism and Atomic Physics, Vol. II, Atomic Physics, I, University Tutorial Press (1958).Google Scholar
- 4.Glasser, Quimby, Taylor, Morgan & Weatherwax, Physical Foundations of Radiology, Pitman, 150–153 (1962).Google Scholar
- 5.Birks, Scintillation Counters, Pergamon Press (1953).Google Scholar | <urn:uuid:3b9279ec-e553-41c6-b2cb-18721836e2a8> | 2.71875 | 329 | Truncated | Science & Tech. | 50.801795 | 95,646,180 |
Soils and Global Change — An Overview
There have been a number of meetings and publications on soils and global change in the last few years (Anderson, 1992; Scharpenseel et al., 1990; Bouwman, 1990; Arnold et al., 1990). In continuing further with this work, we ought to bear in mind that the study of soil has been changing rapidly over the last decade or so. Soil science used to be seen almost entirely as a support for agriculture and forestry, and the justification for its study was the increase in productivity which it could bring. Recently this focus has widened enormously. Soil science is now a major component of any environmental science course. Soil biota are an important part of world biodiversity, and soil has a critical part to play in several essential elemental cycles. Soil pollution is as important as, and often far more persistent than, atmospheric and aquatic pollution (Eijsackers and Hamer, 1993). When we consider the impact of global change on soils, we do so from a far broader viewpoint than we would have done only a couple of decades ago. However, despite this massive interest in newer fields, we must not forget the agricultural imperative. The main economic purpose for which soil is used is still agriculture, and amid the potential catastrophes of global change, famine must surely rank as one of the most serious.
KeywordsSoil Organic Matter Global Change Wind Erosion Global Circulation Model Arable Agriculture
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Daniel Bernoulli wrote Euler on 18 December 1734 that he was studying the small (transversal) vibrations of a rod with one end fixed in a wall.1 On 4 May 1735, he wrote that he had found the equation for its shape, namely â d4 y/ dz4 = y, but that its solutions known to him, namely sine and exponential functions, were inappropriate.2 Euler responded that he also had found the equation but only the series form of the solution.3 In October of 1735, Euler presented the St. Petersburg Academy with a paper in which he derived the equation, dealt with the boundary conditions and gave the fundamental solution in series form.4 This paper is of further significance, however, because in it Euler presented a lucid overview of vibration theory as he understood it at the time. He gave the first explicit discussion of the pendulum condition which, in turn, he looked on as a static equilibrium condition. This reduced dynamical (vibration) problems to static problems which were understood with more sophistication. The paper appeared in 1740.
KeywordsFundamental Solution Series Form Force Density Flexible Body Harmonic Force
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Elliptic boundary problems
To solve a boundary problem means to find a solution of a given differential equation in an open set (or manifold with boundary) Ω which on the boundary of Ω satisfies som other given differential equations, called the boundary conditions. In the previous chapters we have only discussed the Cauchy boundary problem. Very little is known yet concerning boundary problems for general partial differential operators. We shall therefore restrict ourselves to studying elliptic differential operators and elliptic boundary conditions, that is, boundary conditions which ensure smoothness of the solutions also at the boundary. By repeating some arguments used in section 4.1 we are led to a formal definition of elliptic boundary problems in section 10.1. In close analogy with section 3.1 we then give in sections 10.2 and 10.3 an existence theory for elliptic boundary problems with constant coefficients in a half space in R n . A local existence theory for elliptic boundary problems with variable coefficients is then developed in section 10.4 by means of the perturbation argument used in Chapter VII. The passage from local to global results is made in section 10.5, where we also give a number of examples. A brief discussions of elliptic boundary problems for systems is given in section 10.6.
KeywordsDifferential Operator Fundamental Solution Boundary Problem Variable Coefficient Null Space
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Researchers at the University of Rochester have made an optics breakthrough that allows them to encode an entire image's worth of data into a photon, slow the image down for storage, and then retrieve the image intact.
While the initial test image consists of only a few hundred pixels, a tremendous amount of information can be stored with the new technique.
The image, a "UR" for the University of Rochester, was made using a single pulse of light and the team can fit as many as a hundred of these pulses at once into a tiny, four-inch cell. Squeezing that much information into so small a space and retrieving it intact opens the door to optical buffering—storing information as light.
"It sort of sounds impossible, but instead of storing just ones and zeros, we're storing an entire image," says John Howell, associate professor of physics and leader of the team that created the device, which is revealed in today's online issue of the journal Physical Review Letters. "It's analogous to the difference between snapping a picture with a single pixel and doing it with a camera—this is like a 6-megapixel camera."
"You can have a tremendous amount of information in a pulse of light, but normally if you try to buffer it, you can lose much of that information," says Ryan Camacho, Howell's graduate student and lead author on the article. "We're showing it's possible to pull out an enormous amount of information with an extremely high signal-to-noise ratio even with very low light levels."
Optical buffering is a particularly hot field right now because engineers are trying to speed up computer processing and network speeds using light, but their systems bog down when they have to convert light signals to electronic signals to store information, even for a short while.
Howell's group used a completely new approach that preserves all the properties of the pulse. The buffered pulse is essentially a perfect original; there is almost no distortion, no additional diffraction, and the phase and amplitude of the original signal are all preserved. Howell is even working to demonstrate that quantum entanglement remains unscathed.
To produce the UR image, Howell simply shone a beam of light through a stencil with the U and R etched out. Anyone who has made shadow puppets knows how this works, but Howell turned down the light so much that a single photon was all that passed through the stencil.
Quantum mechanics dictates some strange things at that scale, so that bit of light could be thought of as both a particle and a wave. As a wave, it passed through all parts of the stencil at once, carrying the "shadow" of the UR with it. The pulse of light then entered a four-inch cell of cesium gas at a warm 100 degrees Celsius, where it was slowed and compressed, allowing many pulses to fit inside the small tube at the same time.
"The parallel amount of information John has sent all at once in an image is enormous in comparison to what anyone else has done before," says Alan Willner, professor of electrical engineering at the University of Southern California and president of the IEEE Lasers and Optical Society. "To do that and be able to maintain the integrity of the signal—it's a wonderful achievement."
Howell has so far been able to delay light pulses 100 nanoseconds and compress them to 1 percent of their original length. He is now working toward delaying dozens of pulses for as long as several milliseconds, and as many as 10,000 pulses for up to a nanosecond.
"Now I want to see if we can delay something almost permanently, even at the single photon level," says Howell. "If we can do that, we're looking at storing incredible amounts of information in just a few photons."
Source: University of Rochester
Explore further: New development in 3-D super-resolution imaging gives insight on Alzheimer's disease | <urn:uuid:b9dcc88a-6170-4e2b-bce5-ca5cc4e94ee9> | 3.59375 | 802 | News Article | Science & Tech. | 37.62487 | 95,646,247 |
SACRAMENTO, Calif. and WASHINGTON, D.C. (February 20, 2018) – The Solar Energy Industries Association (SEIA) commended legislation filed in the California Legislature on Friday that would make it easier for businesses, schools, nonprofits and municipalities to access solar energy.
The Global Wind Energy Council released its annual market statistics last week in Brussels. The 2017 market remained above 50 GW, with Europe, India and the offshore sector having record years. Chinese installations were down slightly—‘only’ 19.5 GW—but the rest of the world made up for most of that. Total installat…
The primary obstacle that is preventing the large scale implementation of solar powered energy generation is the inefficiency of current solar technology. Currently, photovoltaic (PV) panels only have the ability to convert around 24% of the sunlight that hits them into electricity. At this rate, solar energy still holds many challenges for widespread implementation, but steady progress has been made in reducing manufacturing cost and increasing photovoltaic efficiency. Both Sandia National Laboratories and the National Renewable Energy Laboratory (NREL), have heavily funded solar research programs. The NREL solar program has a budget of around $75 million and develops research projects in the areas of photovoltaic (PV) technology, solar thermal energy, and solar radiation. The budget for Sandia’s solar division is unknown, however it accounts for a significant percentage of the laboratory’s $2.4 billion budget. Several academic programs have focused on solar research in recent years. The Solar Energy Research Center (SERC) at University of North Carolina (UNC) has the sole purpose of developing cost effective solar technology. In 2008, researchers at Massachusetts Institute of Technology (MIT) developed a method to store solar energy by using it to produce hydrogen fuel from water. Such research is targeted at addressing the obstacle that solar development faces of storing energy for use during nighttime hours when the sun is not shining. In February 2012, North Carolina-based Semprius Inc., a solar development company backed by German corporation Siemens, announced that they had developed the world’s most efficient solar panel. The company claims that the prototype converts 33.9% of the sunlight that hits it to electricity, more than double the previous high-end conversion rate. Major projects on artificial photosynthesis or solar fuels are also under way in many developed nations.
Energy consumption Energy storage World energy consumption Energy security Energy conservation Efficient energy use Transport Agriculture Renewable energy Sustainable energy Energy policy Energy development Worldwide energy supply South America USA Mexico Canada Europe Asia Africa Australia
In rigid thin-film modules, the cell and the module solar power manufactured in the same production line. The cell is created on a glass substrate or superstrate, and the electrical connections are created in situ, a so-called “monolithic integration”. The substrate or superstrate is laminated with an encapsulant to a front or back sheet, usually another sheet of glass. The main cell technologies in this category are CdTe, or a-Si, or a-Si+uc-Si tandem, or CIGS (or variant). Amorphous silicon has a sunlight conversion rate of 6–12%
NEW PRODUCT! The largest of our monocrystalline solar panels (200W total) in an easy-to-carry briefcase form makes for the ultimate on-the-go setup. Whether you’re boondocking, camping, or needing panels for your backup, the Boulder 200 Solar Panel Briefcase is ideal for any off-grid scenario.
A solar cell, or photovoltaic cell (PV), is a device that converts light into electric current using the photovoltaic effect. The first solar cell was constructed by Charles Fritts in the 1880s. The German industrialist Ernst Werner von Siemens was among those who recognized the importance of this discovery. In 1931, the German engineer Bruno Lange developed a photo cell using silver selenide in place of copper oxide, although the prototype selenium cells converted less than 1% of incident light into electricity. Following the work of Russell Ohl in the 1940s, researchers Gerald Pearson, Calvin Fuller and Daryl Chapin created the silicon solar cell in 1954. These early solar cells cost 286 USD/watt and reached efficiencies of 4.5–6%.
May 16, 2017 — A 54 percent majority of US adults believe that ‘government regulations are necessary to encourage businesses and consumers to rely more on renewable energy sources,’ while 38 percent … read more
Photovoltaics (PV) uses solar cells assembled into solar panels to convert sunlight into electricity. It’s a fast-growing technology doubling its worldwide installed capacity every couple of years. PV systems range from small, residential and commercial rooftop or building integrated installations, to large utility-scale photovoltaic power station. The predominant PV technology is crystalline silicon, while thin-film solar cell technology accounts for about 10 percent of global photovoltaic deployment. In recent years, PV technology has improved its electricity generating efficiency, reduced the installation cost per watt as well as its energy payback time, and has reached grid parity in at least 30 different markets by 2014. Financial institutions are predicting a second solar “gold rush” in the near future.
Utilities have repeatedly said yes. State regulators have agreed until now, approving almost all proposals for new power plants. But this month, citing the growing electricity surplus, regulators announced plans to put on hold the earlier approvals of four of the eight plants to determine if they really are needed.
The sun has a unique role in sustainable energy production, in that it is the undisputed champion of energy; the resource base presented by terrestrial insolation far exceeds that of all other renewable energy sources combined. The solar energy resource additionally far exceeds what can possibly be envisioned as a level of human consumption necessary to support even the most technologically advanced society. However, to be a material contribution to primary energy supply, solar energy must be captured, converted, and stored to overcome the diurnal cycle and the intermittency of the terrestrial solar resource. Arguably the most attractive method for this energy conversion and storage is in the form of chemical bonds, by production of cheap solar fuels. Significant advances in basic science, however, are needed for this technology to attain its full potential. Chemistry will assume a special role in this endeavor, because new materials must be created for solar capture and conversion, and because new catalysts are needed for the desired chemical bond conversions. Here we present a blueprint for a reaction chemistry, when interfaced to a charge-separation structure, that permits artificial photosynthesis to be envisioned. The progress of scientists in chemistry, biology, engineering, materials science, and physics in addressing the basic science challenges involved with realizing this artificial photosynthesis will be critical to enable humans to use the sun sustainably as their primary energy source.
Using data from Electric Power Annual 2014 the expected changes in generating capabilities for different fuel sources is shown in the chart-2015-2019 Electric Power Annual Capacity Projections. Looking only at the renewable fuel sources, a total of 206.2 Gigawatts of renewable would be available by 2019. This is up 36 Gigawatts (+21.1%) from 2014. Using this generating capability and the capacity factors from 2014 data will result in a total of 627.7 terawatt-hours (TWh) of renewable electric energy in 2019. This would be up 89.4 TWh (+16.7%) from 2014.
Jump up ^ Timmer, John (25 September 2013). “Cost of renewable energy’s variability is dwarfed by the savings: Wear and tear on equipment costs millions, but fuel savings are worth billions”. Ars Technica. Condé Nast. Retrieved 26 September 2013. | <urn:uuid:16d747bb-a2b3-4f1e-b83e-56bcb486c50b> | 2.640625 | 1,612 | Content Listing | Science & Tech. | 29.976402 | 95,646,266 |
Human interaction and stimulation enhance chimpanzees’ cognitive abilities, according to new research from the Chimpanzee Cognition Center at The Ohio State University. The study (1) is the first to demonstrate that raising chimpanzees in a human cultural environment enhances their cognitive abilities, as measured by their ability to understand how tools work.
The scientists compared three groups of chimpanzees: one with a history of long-term stable, social interaction with humans (‘enculturated’); a group raised in a sanctuary setting, with only caretaker contact with humans (‘semi-enculturated’); and another group raised under more austere captive conditions (laboratory chimpanzees). The experiments looked at how the chimpanzees used rakes in order to retrieve a fruit yoghurt reward. The overall study examined not only whether the chimpanzees understood the properties of the tool, but also whether they understood the reasons why the tool worked.
The researchers gave the animals access to small rakes with either a rigid wooden head or a flimsy fabric head. Both enculturated and semi-enculturated chimpanzees correctly chose the rigid rake which enabled them to obtain the reward, indicating that both of these groups understood the physical properties of the two different rakes.
The researchers then presented the same two groups with two identical ‘hybrid’ rakes. Each rake head had a rigid side made of wood (functional) and another side made of flimsy cloth (non-functional). The reward was placed in front of the rigid side of one rake, and in front of the flimsy side of the second rake. The animals who picked the rake with the food reward on the rigid side demonstrated that they understood the causal principles behind the functionality of the rake.
The enculturated chimpanzees successfully selected the functional rake, while the sanctuary chimpanzees chose randomly between the two hybrid tools. The captive laboratory chimpanzees failed both tests, as demonstrated in previously published work (2).
According to Dr. Sarah Boysen, who led the study, “We think our findings mean that the conditions under which chimpanzees are raised, housed, and maintained have long-term effects on their cognitive development, and offer direct comparisons with early experience, issues of attachment, and preschool education for human infants and children,”
The authors conclude that the differences in performance between the three groups are directly attributable to the significant effect of level of enculturation. They add that “enculturated chimpanzees may be better at learning within a highly social, interactive context because they have heightened attention to the actions of others.”
1. Furlong EE, Boose KJ, Boysen ST (2007). Raking it in: the impact of enculturation on chimpanzee tool use. Animal Cognition DOI 10.1007/s10071-007-0091-6
2. Povinelli DJ (2000). Folk physics for apes: the chimpanzee’s theory of how the world works. Oxford University Press, New York.
Source: Animal Cognition | <urn:uuid:eb6d14ad-788c-4a90-bace-693a4d5a3fe7> | 3.640625 | 618 | News Article | Science & Tech. | 31.139253 | 95,646,275 |
Giant pterosaurs 'were capable of flying 10,000 miles non-stop
to other continents'
Giant pterosaurs may have been capable of flying up to 10,000 miles non-stop, scientists believe.
The huge flying creatures, some of which had a wingspan of more than 30 feet, used updrafts of warm air and wind currents to fly over long distances, according to new research.
Michael Habib, a paleontologist at Chatham University in Pittsburgh, US, said: ‘They probably only flapped for a few minutes at a time ... and then their muscles had to recover. In between, they're going to use unpowered flight and glide.
A pterosaur model is hoisted in the air above a cliff in Kansas. New research suggests that the pterosaur was capable of flying huge distances
The effort required to get airborne would use large amounts of energy meaning that each pterosaur would burn around 72 kilogrammes of fat reserves on each trip.
Pterosaurs dominated the skies between the Jurassic and Cretaceous Periods more than 65 million years ago. They were four-limbed animals with membranous wings that stretched between their front and back legs.
The biggest type of pterosaur weight around 400 pounds and is the biggest animal to have ever flown. They were successful residents of the Earth for 150 million years.
The new research raises the startling possibility that pterosaurs could have criss-crossed the globe and visited different continents.
The research team modeled the pterosaurs based on what is now known about their body mass, fat and wing shapes.
With pterosaurs able to fly to the U.S. and back, the research raises the possibility that they could have criss-crossed the globe, visiting other continents
They also looked at new ways that the pterosaur flew, disregarding previous models which had based its action on that of the albatross – the largest living bird.
Previous studies have suggested that the pterosaur may even have been flightless because it was too big to get off the ground. Instead, Habib’s team say that the large pterosaurs may have launched themselves into the air using all four limbs.
The thicker, more humid atmosphere on Earth during the Cretaceous period when the pterosaurs were alive may also have made it easier to fly, the researchers say,
Habib also told National Geographic that ‘unsteady dynamics’ – the means by which birds move in the air – would also have allowed pterosaurs to become airborne despite their vast weight.
'If [giant pterosaurs] could fly very far, that might change how scientists think about their distribution,' Habib said.
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into the atmosphere than all of mankind to date, let alone 10,000 times more, is one of the most pervasive as well as one of the most demonstrably false climatological claims out there.
It stems, ultimately, from a geologist named Ian Plimer, infamous for writing a widely discredited book titled Heaven and Earth, which attempted to argue that humans have had an insignificant effect on global climate. From a fact-checking standpoint, there are no interpretations of Plimer’s second sentence that can produce a factual assertion.
One volcanic cough can do this in a day.” This brief statement — a mere 28 words — yields a remarkably dense buffet of spurious claims and outright falsehoods. All other interpretations fall well short of reality. The question is not about how much other stuff is in the atmosphere.The eruption was preceded by a two-month series of earthquakes and steam-venting episodes, caused by an injection of magma at shallow depth below the volcano that created a large bulge and a fracture system on the mountain's north slope. PDT (UTC−7) on Sunday, May 18, 1980, caused the entire weakened north face to slide away, creating the largest landslide ever recorded.This allowed the partly molten, high-pressure gas- and steam-rich rock in the volcano to suddenly explode northwards toward Spirit Lake in a hot mix of lava and pulverized older rock, overtaking the avalanching face. At the same time, snow, ice and several entire glaciers on the volcano melted, forming a series of large lahars (volcanic mudslides) that reached as far as the Columbia River, nearly 50 miles (80 km) to the southwest.In places, the vertical separation is actually very small; the new layer lying just above the stumps of the older layer.Close examination of the strata reveals typical evidence of sorting of layers, which tend to show reverse grading with the coarser material on top.During that same period, 282 Pg C were released by combustion of fossil fuels, and 5.5 additional Pg C were released to the atmosphere from cement manufacture. | <urn:uuid:9a8a8852-a972-43dd-ac41-eb784ebc7a25> | 3.421875 | 435 | Knowledge Article | Science & Tech. | 42.043897 | 95,646,290 |
The University of Pennsylvania is part of a collaboration of physicists and computer scientists from the United States, Canada, the United Kingdom, Israel, Argentina and Japan investigating a radical new idea about the fundamental nature of reality.
Through the collaboration, called " It from Qubit ," researchers hope to find out if a subtle property of quantum information, measured by "quantum bits" or "qubits," is giving rise to the structure of space and gravity.
Vijay Balasubramanian , a professor of physics in the School of Arts & Science s at Penn, is a principal investigator in the collaboration.
"Over the last half-dozen years," Balasubramanian said, "there has been a motley crew of people from all over the world who have been pursuing an idea that the nature of space is determined by an underlying quantum mechanical reality that shared quantum information leads to connections in physical space and that gravity can emerge from the dynamics of information."
The name of the collaboration is an allusion to an essay by physicist John Archibald Wheeler who coined the term "black hole." In an essay written in 1989, Wheeler asked the question, "How come existence?" and proposed that "...every physical quantity, every it, derives its ultimate significance from bits, binary yes-or-no indications, a conclusion which we epitomize in the phrase, it from bit."
It from Qubit, which is funded by the Simons Foundation , is striving towards what has been the Holy Grail of modern physics for decades: a theory of quantum gravity.
In the early part of the 20th century, Albert Einstein revolutionized the field of physics with his theory of general relativity. Gravity, Einstein explained, was not simply a force as had previously been thought but actually resulted from a warping of space and time.
Around the same time, there was another revolution in physics. Physicists realized that at the shortest distances, the fundamental nature of reality is quantum mechanical, which means that it is full of laws that allow strange, counterintuitive behaviors, such as a particle existing in multiple places at the same time or randomly fluctuating between locations.
One of the strangest phenomena in quantum mechanics is something called entanglement. On a macroscopic scale it can be thought of as an entanglement in terms of correlation, the tendency of things to happen together. For example, as Balasubramanian explained, the colder it is outside, the more likely a person is to wear a jacket. In other words, temperature and wearing a jacket are correlated.
When two systems are entangled in quantum mechanics, it means that they are correlated in a very special way so that if there is manipulation or measurement of one of the systems, it can have the property of measuring the other system at the same time. This is not just a theoretical idea, scientists are actually working on harnessing this phenomenon in order to share quantum bits of information, or qubits, in a practical way between separated receivers.
During the last few years, Balasubramanian said, physicists have proposed "a beautiful new idea that large amounts of quantum entanglement can lead to physical connections between different locations in space and that gravity can arise from the warping of this entanglement by flows of energy."
This idea originally started with the realization that one can sometimes consider a physical theory in a certain number of dimensions - say, in three dimensions - and show that it is exactly equivalent to the description of a universe with more dimensions.
"There can be physical situations where some of the dimensions of space are fictions," Balasubramanian said. "They’re emergent; they’re not ’really there.’ That raises the question of what it means for a dimension of space to be really there."
In these so-called dualities between lower dimensional and higher dimensional theories, he said, it appears that the extra dimensions of space and gravity emerge from the effects of quantum entanglement.
Examples that theoretical physicists have solved suggest a dramatic general idea: Reality itself may be constructed from qubits, and what is actually there is simply the information about things, so that thinking about continuous space and its organization is merely a way of conceptualizing the information relationships between quantum events.
"A really sharp question along these lines is the so-called black hole information paradox that Stephen Hawking articulated," says Onkar Parrikar, a Penn postdoc also involved in the collaboration. "Hawking proposed that any information that enters a black hole is basically destroyed forever, something that violates the rules of quantum mechanics. For many years now people have been trying to figure out whether information can be recovered from inside black holes. We now think that the resolution of this paradox may lie in the quantum entanglement of the interior and exterior of black holes and the way in which this entanglement effectively connects the inside and the outside."
Balasubramanian agrees that understanding this problem will lead to a fuller understanding of where the universe came from and to the fundamental nature of reality.
"Great civilizations seek to understand the place of human beings in the universe and to organize thinking about who we are, where we are and what the universe is like," he said. "Questions about quantum gravity are really questions about the nature of the universe, and all humans since the beginning of sentience have cared about this kind of thing. These are the great questions of existence."
According to Parrikar, one the most exciting aspects of this collaboration "is the sheer number of people who are talking to each other."
In addition to Penn, there are researchers from University College London , the Hebrew University of Jerusalem , the Perimeter Institute , the University of British Columbia , McGill University , the Yukawa Insitute , the Instituto Balseiro , the University of California, Santa Barbara , the University of Texas at Austin , Princeton University , Stanford University , the Massachusetts Institute of Technology and the California Institute of Technology. The larger the number of people working together, Parrikar said, the larger the pool of ideas.
Also, the It from Qubit project is a collaboration of people from two different scientific communities: computer science and physics.
"It’s a really amazing confluence of intellectual directions," Balasubramanian said. "There are people who want to think about the nature of space and time and the origin of the universe and people who want to think about the nature of information. It’s a really interesting and beautiful idea that being ’it’ comes out of information ’qubit.’ And it’s astonishing to see this idea incarnated as a physical, mathematical theory that may have a concrete realization in the world." | <urn:uuid:bb4ddd22-0b06-4eb9-9bc4-037ee90dae6d> | 3.21875 | 1,381 | News (Org.) | Science & Tech. | 22.091382 | 95,646,328 |
In a paper posted on the arXiv pre-print server on Wednesday, physicist Stephen Hawking dashed the dreams of science fiction aficionados by declaring that black holes don’t exist.
Stephen Hawking claims that two of the properties most often identified with black holes — the singularity and the event horizon — don’t exist, at least not in the way that was previously thought. Therefore, black holes themselves can’t exist. At the moment, he hasn’t offered up a new name for the objects that look and act like the objects previously referred to as “black holes.”
In “Information preservation and weather forecasting for black holes,” Hawking argues that there is no event horizon, nor is there a singularity siphoning in all matter, light and information and destroying it. He claims that information about this material — which is communicated through “Hawking radiation” — would not be destroyed, merely reconfigured to such an extent that it would be impossible to reconstruct what the objects that fell into the hole originally were.
Physicist Don Page told Nature that it “would be worse than trying to reconstruct a book that you burned from its ashes,” which is why Hawking compared it to weather forecasting, which is possible in theory, but rarely accurate in practice.
The consequences of Hawking’s theory would be that information, however scrambled, could escape a black hole — and given that, according to Hawking, “there is no escape from a black hole in classical [quantum] theory,” that means that black holes as we know them cannot exist.
Hawking’s paper is an attempt to respond to what has been called “the firewall paradox,” an attempt to reconcile the relativistic physics of Einstein with quantum mechanics.
According to the theory of relativity, an astronaut passing through the event horizon of a black hole should observe the laws of physics behaving as they do in the rest of the universe, slowly feeling her feet being pulled more strongly than her head as she begins to undergo what physicists call “spaghettification.”
But a team led by theoretical physicist Joseph Polchinski demonstrated that according to the laws of quantum mechanics, an astronaut unlucky to dive into a black hole would slam into a highly energetic region of space they dubbed a “firewall,” which would instantly cause her to explode from the subatomic level up.
Hawking’s solution is that the laws of both general relativity and quantum mechanics still abide, but that the conception of the “event horizon” is mistaken: it simply doesn’t exist in a manner that would cause the astronaut to combust: “[t]he absence of event horizons means that there are no black holes — in the sense of regimes from which light can’t escape to infinity,” he writes.
In its place, he posits there is an “apparent horizon,” an area in which space-time fluctuates too wildly for a sharp boundary to exist, alleviating the need for either an event horizon or a firewall.
If this is true, however, it means that there is also no singularity at the core of the black hole. Gravity would pull matter and light into the black hole — and the more material it collected, the stronger that pull would be — but it would never truly be destroyed.
It would merely be incomprehensible, leaking out of the black hole via Hawking radiation, but as inadequate a means of understanding larger cosmic processes as a shifting breeze in upstate New York would be to predicting the 2056 hurricane season.
[Image via AFP] | <urn:uuid:0a11efcf-d2d9-4d77-b39b-c4fdbee35770> | 2.59375 | 755 | Truncated | Science & Tech. | 27.746291 | 95,646,331 |
TeachMeFinance.com - explain Natural gas hydrates
Natural gas hydrates --
Solid, crystalline, wax-like substances composed of water, methane, and usually a small amount of other gases, with the gases being trapped in the interstices of a water-ice lattice. They form beneath permafrost and on the ocean floor under conditions of moderately high pressure and at temperatures near the freezing point of water.
About the author
Copyright © 2005 by Mark McCracken, All Rights Reserved. TeachMeFinance.com is an informational website, and should not be used as a substitute for professional medical, legal or financial advice. Information presented at TeachMeFinance.com is provided on an "AS-IS" basis. Please read the disclaimer for details. | <urn:uuid:4e9f5d1a-eda9-4e02-98c6-222f37d0f76d> | 2.5625 | 164 | Knowledge Article | Science & Tech. | 31.629164 | 95,646,338 |
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Aggressive: eager to fight.
Dewlap: (pronounced \"doo-lap\") brightly colored skin on a lizard's throat that can be puffed out and displayed to communicate with other lizards.
Morphs: animals that are the same species, but have different looking forms. Tree lizard morphs have different colored dewlaps.
Territory: an area defended and owned by an individual.
A group of children are busy playing in the park. They look up as a tough-looking boy approaches. "Hey, this is my playground!" he says with a nasty smirk. "You'd better get outta here now or you'll be sorry!" The other children flee in search of another place to play. Every playground has its bullies. Why do some people's instincts tell them to fight, and other people would rather just run away? Many animals behave the same way. Biologists at Arizona State University hope that by learning more about animal behavior, they will also be able to understand why people act the way they do. Michael Moore is a professor of biology and an expert on animal behavior. He and others in his laboratory think that hormones are part of the answer.
Moore and his partners study hormones and behavior in tree lizards. If you live in the Phoenix area, you have probably seen these lizards in your own back yard. Male tree lizards are handy for studying behavior because they come in multiple forms, or "morphs," that look and act different. One male morph has an orange dewlap with a blue spot in the center. These males are very aggressive and territorial, like the school yard bully. The other male morph has a solid orange dewlap with no blue spot. Like the other kids at the playground, orange males prefer to avoid arguments. They wander from place to place instead of trying to settle their own land.
The tree lizards' dewlaps are like flags that tell other lizards how they behave. An orange-blue dewlap might say "put up your dukes!" Orange dewlaps say "excuse me, I was just leaving." People can also use these visual signals to determine how aggressive a lizard is. This is very helpful for biologists who study tree lizard behavior.
One of Moore's discoveries is that the hormones testosterone and progesterone make the male tree lizard morphs different. When they are babies, orange-blue tree lizards have lots of testosterone and progesterone. Orange males have much less. Because their hormone levels are different, the two types of males develop differently. High levels of these hormones cause males to develop orange-blue dewlaps, and think like fighters. In fact, Moore can change a timid orange male into a feisty orange-blue male by increasing its testosterone or progesterone levels.
If hormones change the way a tree lizard's dewlap looks, do they also change its brain? Moore's research team is now doing experiments to find out whether orange-blue males' brains look different from those of orange males. They are particularly interested in the areas in the brain that control aggressive behavior. If these areas do look different, then maybe tree lizards can teach us something about how hormones affect the mysterious workings of the mind.
Additional photographs courtesy of Brad and Lynn Weinert. To see more of their work visit Brad and Lynn's Field Photos.
Danika Painter. (2009, September 16). Mighty Morphing Tree Lizards. ASU - Ask A Biologist. Retrieved July 18, 2018 from https://askabiologist.asu.edu/explore/tree-lizards
Danika Painter. "Mighty Morphing Tree Lizards". ASU - Ask A Biologist. 16 September, 2009. https://askabiologist.asu.edu/explore/tree-lizards
Danika Painter. "Mighty Morphing Tree Lizards". ASU - Ask A Biologist. 16 Sep 2009. ASU - Ask A Biologist, Web. 18 Jul 2018. https://askabiologist.asu.edu/explore/tree-lizards
Ornate Tree Lizard (Urosaurus ornatus) used with permission of Brad and Lynn Weinert. | <urn:uuid:770b1eb5-9c04-4c54-93e4-e5688204a539> | 3.125 | 896 | Knowledge Article | Science & Tech. | 54.392829 | 95,646,339 |
Data Model Concepts and Reactive Programming
Data Model Concepts and Reactive Programming
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The new Gartner Critical Capabilities report explains how APIs and microservices enable digital leaders to deliver better B2B, open banking and mobile projects.
Tables , Columns, and Keys
When building a business application or connecting to an existing SQL database, the core concept of tables and columns can be visualized as a spreadsheet of raw data. When designing a business application or extending an existing legacy model the first step is to identify the primary key(s) for each row. The ability to identify a unique row is critical for Espresso Logic to work correctly. WIthout an identified primary key updates and deletes would be difficult if not impossible to perform. The Primary Key is also used in foreign key declarations (e.g. relationships) to join parent to child. Espresso Logic will use these native relationships and user defined declarations to enforce referential integrity (RI) at the server across databases. The attributes are used for column derivations (formula, sums, counts, parent copy) and the entities hold the cross column validations.
If each table represents a spreadsheet page, then a workbook would be a collection of tables with ‘links’ that join or lookup related data. The relationship is defined as a foreign key from the child table to the parent table. Relationships can include one or more column attributes. The advantage of the predefined relationship is that it helps the SQL engine optimize joins and validate related data (RI). A relationship is often described by the roles it plays from parent to child. A common example is the state code field in an address collection. The parent table StateCodeTypes has a primary key stateCode and the Address table has a foreign key reference from the stateCode. Espresso Logic uses these relationships to validate data before writing back to disk. This means that you can add new tables and new user defined relationships for lookup and validation without having to change your existing schema. (See Espresso Logic Multi-database support page). The Resource editor and Live Browser both use these relationships to help build new nested documents and display parent/child data and foreign key data lookups.
Derivations (SUMS, COUNT, MIN, MAX)
When you see a spreadsheet with subtotals and totals – these are formula expressed on a column or row. In our example, we know we can add formula to each single record to create row totals. For column subtotals, we will introduce a new parent table to hold these aggregate values. The common example is the shopping cart where the order total is the parent and the cart details are the individual rows. Our parent may have columns to sum the order line total amount, the discounts applied, and any tax or shipping costs associated with the row. Counts can be applied to the parent (e.g. you have 3 items in your cart). If your existing database schema cannot be easily changed, simply add a new parent table to a new database and create a user defined relationship from the parent to the existing child. New entries into the child can automatically create the parent (manage parent rule) and create these aggregations. In fact, the concept of a multi-hierarchy rollup is very easy to achieve. Weeks can roll up to months, months to quarters, and quarters into years. Business logic can create the same analysis on your entire SQL database that you would consider using a spreadsheet. If a row derivation is needed, the model will need to be altered to add a new column.
One special rule is the parent copy – using a relationship to the parent table, a parent attribute value can be copied down into the selected child column. A common example is the shopping cart, we want to copy the current price of the product down to the cart line item so that the price can be used to calculate the line total (price * quantity). If the parent price changes in the future – it will not impact the child. If you need to propagate a change to all children, use an Event, described below.
Putting it together
In our shopping cart example, we have been asked to add a new pricing policy (Buy one Get one – BOGO) to our existing application. We are also told that the max limit per order is 4 and the max limit per customer is 10. Further, these rules only apply to selected products during a selected date range. To make it more difficult our DBA told us we cannot change the data model – only the logic. We will need to create new tables to hold the BOGO products, effective dates, and limits. We will also need a global customer bogo table to count lifetime limits. Our new tables will be joined to our existing shopping cart, product, and the new pricing rules will be applied to our existing formula.
Our Bogo_product table has effective dates, product ID, and bogo limits for orders and customers, and the discount price. It is up to the rule itself to determine if a product is used in the BOGO calculation and is within the effective date. The count on the CustomerBogo table is used to determine the lifetime limit. These tables can be added to the existing database or a new database. Now the formula to determine the line item price is invoked to lookup the price and then ask if this is a bogo product within the effective range.
var rows = logicContext.getRowsByQuery("bogo_product", "select * from bogo_product where id <> "+row.productID +' and effStartDT >= getDate() and effEndDate <= getDate()); for (var i = 0; i < rows.length; i++) log.debug('Found bogo_product:' + rows[i].name);
Validations are used to enforce lifetime customer and client line item purchase amounts. In Espresso Logic, rules are added and invoked based on a dependency tree of columns and entities. This means you do not need to invoke or ‘call’ rules, rules are invoked when state change occurs (e.g. insert or update). The image below is an example of the Logic Design Studio relationship editor used to join tables between new and existing databases.
Espresso Logic can connect to one or more of your existing SQL and NoSQL databases and create an instant REST API for tables, views, and stored procedures. Business Logic can be placed on top of existing entities and attributes or new tables can be added to new databases and joined into your legacy system to create new REST API endpoints that provide sophisticated business transaction logic. Data Model concepts like adding new tables or altering tables to add columns to support business rules is an integral part of the design lifecycle of reactive programming.
Published at DZone with permission of Val Huber , DZone MVB. See the original article here.
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By John Fernandes
Read or Download Comprehensive biotechnology PDF
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Extra info for Comprehensive biotechnology
After emptying and rinsing from the previous batch, mash at 13-17 wt% sugar is pumped to the fermenters. Once 20% full, the inoculum is added to allow growth during the remainder of the filling cycle, which can last 4-6 h. Fermentation temperature is regulated by circulating cooling water through submerged coils, circulating the mash through external heat exchanges, or simply spraying the vessel walls with cool water (adequate for small fermenters only). The feed is generally Ethanol 21 introduced at 25-30 °C, and the temperature allowed to gradually rise as heat is evolved.
In the Melle-Boinot process, yeast cells from the previous fermentation are recovered by centrifugation and up to 80% are recycled. The initial cell density of a batch is thus as high as 80 billion cells 1-1 and very rapid ('boiling') fermentation begins almost immediately. With the long growth phase eliminated, the overall fermentation cycle time is reduced by one-half to two-thirds, increasing volumetric productivity to typically 6 g 1-1 h-1. The Melle-Boinot process was generally developed for and is widely used in sulfite waste liquor fermentation, where the low sugar concentrations require maximum yield and cell recycle achieves much higher cell densities and reduced fermentation time.
The best known are undoubtedly cognac and armagnac. All prestigious products have been created empirically. the reputation of the great wine regions having advanced, and greatly thanks to chemical and biological studies". Therefore, one easily attributes the merits of wines to the quality of nature, and sometimes one questions the role of enology. RIBEREAU-GAYON and PEYNAUD supply a precise answer to this question of their "Traite d' CEnologie" (1960), "A good wine or a great wine may be obtained without the aid of modem enology. | <urn:uuid:121ad544-bdd5-4e1c-96c4-cda944d23033> | 2.546875 | 619 | Truncated | Science & Tech. | 30.974321 | 95,646,377 |
Species Detail - Pyrenean Glass Snail (Semilimax pyrenaicus) - Species information displayed is based on the dataset "All Ireland Non-Marine Molluscan Database".
Terrestrial Map - 10kmDistribution of the number of records recorded within each 10km grid square (ITM).
Marine Map - 50kmDistribution of the number of records recorded within each 50km grid square (WGS84).
Pyrenean Glass Snail
(A. Férussac, 1821)
1 January (recorded in 1976)
31 December (recorded in 1975)
Conchological Society of Great Britain and Ireland, All Ireland Non-Marine Molluscan Database, National Biodiversity Data Centre, Ireland, Pyrenean Glass Snail (Semilimax pyrenaicus), accessed 23 July 2018, <https://maps.biodiversityireland.ie/Dataset/1/Species/123958> | <urn:uuid:27a4f0d0-d8a1-4aae-823e-8d9f5b4ef69b> | 2.5625 | 207 | Structured Data | Science & Tech. | 26.185882 | 95,646,401 |
1. The C-O-C bond angle (degees) in the compound CH3-O-CH3 is closest to
2. Which of the following molecules would be expected to be MOST water soluble?
3. The relationship between CH3CH2OH and HOCH2CH3 is best described as
a. constitutional isomers
b. geometric isomers
c. unrelated compounds
d. same compound
4. The structure of urea is shown below. The carbon atom in urea is:
a. sp3 hybridized
b. sp2 hybridized
c. sp hybridized
d. sp3d hybridized
1. The functional group of ether is an oxygen atom bonded to two carbon atoms. In daily ethers, oxygen is sp3 hybridized with bond angles of approximately 109.5°. In dimethyl ether, the C-O-C bond angle is 110.3°. So the answer is B. closest to 109
2. Both b and C have good solubility in water but, ...
This Solution contains over 200 words to aid you in understanding the Solution to these questions. | <urn:uuid:f367ea4c-4dc9-4f50-a4d8-55719d4efc6b> | 3.078125 | 239 | Content Listing | Science & Tech. | 79.268077 | 95,646,413 |
CHICK OR TREAT
Scientists have found a way to save rare hen breeds by creating mutant chickens that can lay their eggs
Plan is to boost numbers of dying species such as Old English Pheasant Fowl, the Rumpless Game, Scots Dumpy and Dorking
EXPERTS have found a way to save rare hen breeds by creating mutant chickens that can lay their eggs.
They aim to boost numbers of dying species such as Old English Pheasant Fowl, the Rumpless Game, Scots Dumpy and Dorking.
Scientists from the University of Edinburgh’s Roslin Institute – the same institution that gave the world Dolly the sheep – knocked out fertility genes to create an egg containing a sterile chick.
But when stem cells from rare breeds were implanted into that egg it created GM surrogates, which can go on to produce eggs and chicks from the threatened species.
The team are also freezing early stem cells for dozens of chicken types to create a “frozen aviary” – the bird equivalent of a seed bank.
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So far, the team have collected more than 500 samples from 25 different breeds. Held in a freezer at minus 150C, the cells will remain viable for decades.
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Explaining the mysterious dynamics of glassy materials
Colorful church windows, beads on a necklace and many of our favorite plastics share something in common -- they all belong to a state of matter known as glasses. School children learn the difference between liquids and gases, but centuries of scholarship have failed to produce consensus about how to categorize glass.
Now, combining theory and numerical simulations, researchers have resolved an enduring question in the theory of glasses by showing that their energy landscapes are far rougher than previously believed. The findings appear April 24 in the journal Nature Communications.
"There have been beautiful mathematical models, but with sometimes tenuous connection to real, structural glasses. Now we have a model that's much closer to real glasses," said Patrick Charbonneau, one of the co-authors and assistant professor of chemistry and physics at Duke University.
The new model, which shows that molecules in glassy materials settle into a fractal hierarchy of states, unites mathematics, theory and several formerly disparate properties of glasses.
One thing that sets glasses apart from other phase transitions is a lack of order among their constituent molecules. Their cooled particles become increasingly sluggish until, caged in by their neighbors, the molecules cease to move -- but in no predictable arrangement. One way for researchers to visualize this is with an energy landscape, a map of all the possible configurations of the molecules in a system.
Charbonneau said a simple energy landscape of glasses can be imagined as a series of ponds or wells. When the water is high (the temperature is warmer), the particles within float around as they please, crossing from pond to pond without problem. But as you begin to lower the water level (by lowering the temperature or increasing the density), the particles become trapped in one of the small ponds. Eventually, as the pond empties, the molecules become jammed into disordered and rigid configurations.
"Jamming is what happens when you take sand and squeeze it," Charbonneau said. "First it's easy to squeeze, and then after a while it gets very hard, and eventually it becomes impossible."
Like the patterns of a lakebed revealed by drought, researchers have long wondered exactly what "shape" lies at the bottom of glass energy landscapes, where molecules jam. Previous theories have predicted the bottom of the basins might be smooth or a bit rough.
"At the bottom of these lakes or wells, what you find is variation in which particles have a force contact or bond," Charbonneau said. "So even though you start from a single configuration, as you go to the bottom or compress them, you get different realizations of which pairs of particles are actually in contact."
Charbonneau and his co-authors based in Paris and Rome showed, using computer simulations and numeric computations, that the glass molecules jam based on a fractal regime of wells within wells.
The new description makes sense of several behaviors seen in glasses, like the property known as avalanching, which describes a random rearrangement of molecules that leads to crystallization.
"There are a lot of properties of glasses that are not understood, and this finding has the potential to bring together a wide range of those problems into one coherent picture," said Charbonneau.
Understanding the structure of glasses is more than an intellectual exercise -- materials scientists stand to advance from the knowledge, which could lead to better control of the aging of glasses.
Co-authors on the paper included Jorge Kurchan and Pierfrancesco Urbani of Paris, and Giorgio Parisi and Francesco Zamponi of Rome.
This work was supported by the European Research Council (grants NPRGGLASS and #247328) and the Alfred P. Sloan Foundation.
Citation: "Fractal free energy landscapes in structural glasses," Patrick Charbonneau, Jorge Kurchan, Giorgio Parisi, et al. Nature Communications, April 24, 2014. DOI: 10.1038/ncomms4725.
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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It's a make-out session on a cosmic scale: Two incredibly hot stars, spinning in a tight orbit around one another, appear to be "kissing." The stellar pair are so close together that their surfaces overlap, creating a bridge between them.
The smooching stars are two of the hottest and most massive overlapping double stars ever identified, according to new research. Catching two stars in this phase of life is "extremely rare," the European Southern Observatory (ESO) said in a statement, because the stars don't remain in this state for long. Check out this video from Space.com describing how the stars might meet their demise.
Known collectively as VFTS 352, the enormous stars provide a rare look at the mixing of material from two different stellar sources, said Leonardo Almeida, at the University of São Paulo, Brazil, and lead author of a study that identified the unusual pair. "As such, it's a fascinating and important discovery," he said in a statement.
When two double stars orbit one another close enough that they share their components, they are known as "overcontact binaries," according to the statement from the ESO. Only a handful of this unusual class of stars has been identified, primarily because they inhabit this step of evolution for a brief span of time in their overall lifetimes.
Of these, VFTS 352 is the earliest-type, hottest and most massive overcontact binary known, with a combined mass of about 57 times that of the sun and surface temperatures above 40,000 degrees Celsius (72,000 degrees Fahrenheit), according to the new research paper. The kissing stars were spotted using the European Space Observatory's Very Large Telescope (VLT).
Located about 160,000 light-years away from Earth, in the Tarantula Nebula, the two stars in VFTS 352 orbit each other in just over one Earth day. The stellar cores are only about 7.5 million miles (12 million kilometers) apart, so close that their surfaces overlap, forming a bridge between the two.
Unlike their cousins, "vampire binaries," which have one smaller star sucking material from its larger neighbor, VFTS 352 contains two stars of almost identical size. Instead of one star stealing material from the other, the pair may share as much as 30% of their components.
It remains uncertain what will happen to the unlikely pair, but their future will definitely be cataclysmic. In one scenario, the two stars may merge to create a single, rapidly rotating, highly magnetic, gigantic star. This merger, the researchers say, would produce an incredible cosmic fireworks show.
"If it keeps spinning rapidly, it might end its life in one of the most energetic explosions in the universe, known as a long-duration gamma-ray burst," Hugues Sana, of the University of Leuven in Belgium, said in the same statement. Sana was the lead scientist of the VLT FLAMES Tarantula Survey, which identified the exotic pair in the process of studying over 900 stars in the Large Magellanic Cloud, a dwarf galaxy located just outside the Milky Way (earning it the title of "satellite galaxy").
In a second scenario, the two stars would "both remain compact, and the VFTS 352 system may avoid merging," said the team's lead theoretical astrophysicist Selma de Mink, of the University of Amsterdam. "This would lead the objects down a new evolutionary path that is completely different from classic stellar evolution predictions."
In this case, said de Mink, the stars would end their lives in supernova explosions, producing a pair of closely orbiting black holes. If scientists can catch this event as it is happening, it provide an observational breakthrough for stellar astrophysics, because it would likely produce gravitational waves. These ripples in space-time are generated by extreme variations of strong gravitational fields, and are predicted by Einstein's theory of gravity, but have never been directly observed.
The research was published online in the Astrophysical Journal.
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Octopus, squid and cuttlefish are famous for engaging in complex behavior, from unlocking and escaping from an aquarium tank to instantaneous skin camouflage to hide from predators. A new study suggests their evolutionary path to neural sophistication includes a novel mechanism: Prolific RNA editing at the expense of evolution in their genomic DNA.
The study, led by Joshua J.C. Rosenthal of the UChicago-affiliated Marine Biological Laboratory and Eli Eisenberg and Noa Liscovitch-Brauer of Tel Aviv University is published this week in Cell. The research builds upon the scientists’ prior discovery that squid display an extraordinarily high rate of editing in coding regions of their RNA—particularly in nervous system cells—which has the effect of diversifying the proteins that the cells can produce. (More than 60 percent of RNA transcripts in the squid brain are recoded by editing, while in humans or fruit flies, only a fraction of 1 percent of their RNAs have a recoding event.)
In the present study, the scientists found similarly high levels of RNA editing in three other “smart” cephalopod species (two octopus and one cuttlefish) and identified tens of thousands of evolutionarily conserved RNA recoding sites in this class of cephalopods, called coleoid. Editing is especially enriched in the coleoid nervous system, they found, affecting proteins that are the key players in neural excitability and neuronal morphology.
In contrast, RNA editing in the more primitive cephalopod Nautilus and in the mollusk Aplysia occurs at orders of magnitude lower levels than in the coleoids, they found. “This shows that high levels of RNA editing is not generally a molluscan thing; it’s an invention of the coleoid cephalopods,” Rosenthal said. In mammals, very few RNA editing sites are conserved; they are not thought to be under natural selection. “There is something fundamentally different going on in these cephalopods where many of the editing events are highly conserved and show clear signs of selection,” Rosenthal said.
The scientists also discovered a striking trade-off between high levels of RNA recoding and genomic evolution in these cephalopods. The most common form of RNA editing is carried out by ADAR enzymes, which require large structures flanking the editing sites. These structures, which can span hundreds of nucleotides, are conserved in the coleoid genome along with the editing sites themselves. The genetic mutation rate in these flanking regions is severely depressed, the team reported.
“The conclusion here is that in order to maintain this flexibility to edit RNA, the coleoids have had to give up the ability to evolve in the surrounding regions—a lot,” Rosenthal said. “Mutation is usually thought of as the currency of natural selection, and these animals are suppressing that to maintain recoding flexibility at the RNA level.”
Rosenthal and colleagues at the MBL are currently developing genetically tractable cephalopod model systems to explore the mechanisms and functional consequences of their prolific RNA editing. “When do they turn it on, and under what environmental influences? It could be something as simple as temperature changes or as complicated as experience, a form of memory,” he said. | <urn:uuid:e64afae2-7f28-4ea0-a1ea-aae8bb5e2e57> | 2.84375 | 691 | News Article | Science & Tech. | 25.510905 | 95,646,470 |
A Korean research team has developed semi-transparent perovskite solar cells that could be great candidates for solar windows.
Scientists are exploring ways to develop transparent or semi-transparent solar cells as a substitute for glass walls in modern buildings with the aim of harnessing solar energy. But this has proven challenging, because transparency in solar cells reduces their efficiency in absorbing the sunlight they need to generate electricity.
Typical solar cells today are made of crystalline silicon, which is difficult to make translucent. By contrast, semi-transparent solar cells use, for example, organic or dye-sensitized materials. But compared to crystalline silicon-based cells, their power-conversion efficiencies are relatively low. Perovskites are hybrid organic-inorganic photovoltaic materials, which are cheap to produce and easy to manufacture. They have recently received much attention, as the efficiency of perovskite solar cells has rapidly increased to the level of silicon technologies in the past few years.
Using perovskites, a Korean research team, led by Professor Seunghyup Yoo of the Korea Advanced Institute of Science and Technology and Professor Nam-Gyu Park of Sungkyunkwan University, has developed a semi-transparent solar cell that is highly efficient and functions very effectively as a thermal mirror.
One key to achieving efficient semitransparent solar cells is to develop a transparent electrode for the cell’s uppermost layer that is compatible with the photoactive material. The Korean team developed a ‘top transparent electrode’ (TTE) that works well with perovskite solar cells. The TTE is based on a multilayer stack consisting of a metal film sandwiched between a high refractive index layer and an interfacial buffer layer. This TTE, placed as a solar cell’s top-most layer, can be prepared without damaging ingredients used in the development f perovskite solar cells. Unlike conventional transparent electrodes that only transmit visible light, the team’s TTE plays the dual role of allowing visible light to pass through while at the same time reflecting infrared rays.
The semi-transparent solar cells made with the TTEs exhibited an average power conversion efficiency as high as 13.3%, reflecting 85.5% of incoming infrared light. Currently available crystalline silicon solar cells have up to 25% efficiency but are opaque.
The team believes that if the semi-transparent perovskite solar cells are scaled up for practical applications, they can be used in solar windows for buildings and automobiles, which not only generate electrical energy but also allow smart heat management in indoor environments, thereby utilizing solar energy more efficiently and effectively.
Learn more: Harnessing energy from glass walls
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Planting a Solution to Soil Erosion
If you think soil erosion amounts to a bit of soil being blown or washed away here and there, think again! Soil erosion costs billions of dollars each year. Can the use of plants help reduce soil erosion? This second grade student designed a project to put the idea to the test. With inexpensive baking trays and seeds, K-12 students can make model hillsides and explore!
Over time, erosion can destabilize a hillside. As a result, erosion may put a house perched on top of a coastal cliff, for example, at risk. Similarly, over a really long period of time, erosion can contribute to geographic formations like the Grand Canyon. While long-term damage from erosion can be dramatic, year to year, soil erosion causes billions of dollars of damage around the world as waterways are polluted by runoff and as portions of farmlands are washed or blown away.
With their network of roots and their propensity to soak up water, plants may play an integral role in preventing soil erosion. Strategic use of plants specifically planted to form a barrier against erosion may trap soil that might otherwise be washed or blown away or may absorb some of the water that would otherwise carry soil. Can the answer to a global problem in the agriculture industry be as simple as planting seeds?
After studying erosion in her 2nd grade class, Riya, a student in New York, decided to put plants to the test and see how effective they may be at stopping soil erosion.
Making a Model at Home
Riya's mother says she and her daughter frequently do science experiments together to extend the hands-on STEM learning available in her elementary school classroom. Last year, Riya and her mother experimented with combining fruit and a vegetarian alternative to gelatin. This year, Riya chose to explore soil erosion for her science fair project.
Using a Science Buddies project on erosion as a launching point, Riya designed her own experiment on plants and erosion to see, firsthand, whether or not plants can help stop or limit erosion, specifically from water. In preparation for her project, Riya planted and grew Fenugreek seeds from her kitchen. After the seeds sprouted, she used disposable aluminum baking trays to create model hillsides with and without plants and then tested to see what happened when water flowed down each hillside.
Students can make their own model hillsides to test the effectiveness of plants in helping soak up water and preventing soil from washing away using the Can Plants Stop Soil Erosion? environmental engineering and plant sciences project.
For another K-12 science project related to erosion, see Riprap: It's Not Hip Hop But Erosion Stop.
A Career in Plant Sciences
Finding ways to use plants to help save money is called economic botany. To learn more about careers related to plants and economic botany, see the following career profiles:
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Metagenomic technologies of detecting genetic resources of microorganisms
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Although metagenomics is a relatively new scientific trend, it has managed to become popular in many countries, including Russia, over its 20-year history. This division of molecular genetics studies ecosystem- extracted nucleic acids (DNA and RNA), which contain full information about the microbial community of a habitat. Owing to metagenomic methods, soil microbiology has undertaken to study not only known cultivated types of microorganisms but also noncultivated forms, the biological properties of which can be suggested exclusively from the genetic information coded in their DNA. It turns out that such “phantom” types constitute the overwhelming majority within soil microbial communities; to all appearances, they actively participate in ensuring soil fertility, and, hence, in the opinion of the authors of this paper, study of them is topical for both basic research and agricultural practice. The development of metagenomic technologies will help understand biological phenomena determined by close plant–microbe interactions, such as increasing the productivity of agricultural crops and protecting them against phytopathogens. However, the introduction of new methods has always presented difficulties; in metagenomics, they are associated with the acquisition, storage, and bioinformational analysis of a huge array of genetic information.
Keywordssoil metagenome plant–microbe systems agriculture high-throughput sequencing
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- 1.V. Torsvik, J. Goksøyr, and F. L. Daae, “High diversity in DNA of soil bacteria,” Appl. Environ. Microbiol. 3 (56), 782–787 (1990).Google Scholar
- 3.L. Yang, M. A. Poles, G. S. Fisch, et al., “HIV-induced immunosuppression is associated with colonization of the proximal gut by environmental bacteria,” AIDS 30 (1), 19–29 (2016).Google Scholar
- 7.M. Carabotti, A. Scirocco, M. Antoniett, et al., “The gut–brain axis: Interactions between enteric microbiota, central and enteric nervous systems,” Annals Gastroenterol. 28, 203–209 (2015).Google Scholar
- 10.I. A. Tikhonovich and N. A. Provorov, Symbioses of Plants and Microorganisms: Molecular Genetics of Future Agrosystems (Izd. SPbGU, St. Petersburg, 2009) [in Russian].Google Scholar
- 16.V. I. Safronova, G. Piluzza, S. Bullitta, and A. A. Belimov, “Use of legume–microbe symbioses for phytoremediation of heavy metal polluted soils: Advantages and potential problems (review),” in Handbook for Phytoremediation, Ed. by I. A. Golubev (NOVA Science, New York, 2011), p. 443–469.Google Scholar | <urn:uuid:3a645896-8879-43f7-bf0c-e1c2866b4614> | 2.890625 | 643 | Truncated | Science & Tech. | 35.272371 | 95,646,540 |
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Java Tutorial - 05 - Using Array Length Instance Variable
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Max Planck scientists show how persistent pollutants will accumulate in the Arctic in the future.
Many organic pollutants that originate from industrial and technical processes, are persistent and are not degraded in the environment. This poses a hazard for the environment and life even in remote regions of the world. These pollutants include the insecticide dichlorodiphenyltrichloroethane and the polychlorinated biphenyls - better known by their abbreviations, DDT or PCB.
These molecules are semi-volatile. This means that at room temperature they are mainly gaseous, however, under low temperatures they condense, and later on may re-evaporate. Therefore, the way these pollutants spread in the environment largely depends on meteorological factors such as wind, temperature and precipitation. These substances mainly arrive in the Arctic via air currents. There they remain particularly persistent.
Scientists from the Max Planck Institute for Chemistry and the Universities of Hamburg and Cambridge have now investigated which impact climate changes. have on the circulation of these substances in the Arctic. There, climate changes particularly rapidly. The research group headed by Gerhard Lammel from the Institute in Mainz chose three persistent substances that globally had been produced in large quantities: DDT, PCB 153 and PCB 28.
In the 1970s, DDT was the most widely used insecticide, however, it was later banned in most countries in the world due to its hormone-like effect on many biota. PCBs were frequently used as plasticizers in plastics and as insulation material, for example in transformers. As they are carcinogenic, they were banned in the 1980s. All three molecules are easily soluble in fat and therefore accumulate in human and animal tissue.
The researchers simulated the Arctic flow conditions with the aid of a coupled atmosphere-ocean-model. Based on the distribution of emissions since the start of industrial production around 1950, and the assumption of future expected residual emissions as well as the future climate, the model calculated which pollutants will flow over the Arctic Circle at the end of this century.
The findings surprised the researchers: Measurements have shown that since the peak pollutant emissions in the last century, less and less DDT and PCP molecules are arriving in the Arctic. However, the forecasts predict that this trend will reverse for DDT around the year 2075 and more DDT will arrive in the Arctic.
This effect will be amplified by climate change. PCBs on the other hand, will not see an increased northward flow across the Arctic Circle, however, the decline rate will level off. Substances do behave differently, because their involvement in processes of cycling in the environment, across, ice, soils, water and air, differs.
The model runs provided another important result. Scientists can now explain why the concentration of persistent pollutants in the atmosphere above Svalbard correlates with the so-called Arctic Oscillation, whereas this is not the case above Greenland. The Arctic Oscillation is a regular oscillation of the atmosphere above the Arctic that creates differences in atmospheric pressure.
It occurs as a result of large temperature differences between the polar region and the temperate mid-latitudes. Pollutant flows from Europe, which correlate positively with the Arctic Oscillation, maintain the concentrations above Svalbard. The pollutant concentrations above Greenland, however, are determined by flows in the Canadian Archipelago, where air currents are in a reverse relation with this oscillation.
In future studies, researchers will investigate other substances’ large-scale distribution, including endosulfan. Endosulfan is an insecticide which replaced DDT in the 1970s, although it is slowly degrading and problematic for the environment, too. It´s use was only restricted in 2013. (SB)
Mega Octaviani, Irene Stemmler, Gerhard Lammel, and Hans F. Graf, Atmospheric Transport of Persistent Organic Pollutants to and from the Arctic under Present-Day and Future Climate, Environmental Science and Technology, DOI: 10.1021/es505636g, 2015
Prof. Dr. Gerhard Lammel
Max Planck Institute for Chemistry
Telephone: +49 (0) 6131-3054055
Dr. Susanne Benner | Max-Planck-Institut für Chemie
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Rhacophorus arboreus is a relatively large treefrog with adult males smaller (42-60mm) than females (59-82mm). These frogs have large heads. They have well developed webbing on their hands but only moderate webbing on their toes. Digits terminate in truncated discs. Dorsally, these frogs are bright green with or without black or brown spots with black edges. Ventrally, they are white or cream with pale brown spots. The iris is orange to brownish red.
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Japan
The Forest Green Treefrog can be found in Honshu, Japan, and the small island of Sado off northeastern Honshu. They can be found from sea level to mountainous regions at altitudes over 2,000 m. Outside of the breeding season, they can be found in trees and leaf litter. During breeding season, they can be found in ponds and rice fields. During winter, they hibernate under moss or shallow soil.
Life History, Abundance, Activity, and Special Behaviors
The diet consists of insects. The male's mating call consist of a series of two to six clicking sounds. After mating the female deposits eggs in a foam nest on vegetation near standing water. The female excretes an albumin-based fluid from her cloaca, which she beats with her hind legs to form the foam nest. She then lays 300-800 eggs into the nest, which the male subsequently fertilizes. The foam nest hardens, protecting the eggs from desiccation and predation. After the eggs hatch the foam softens, and the hatched larvae go into the standing water to begin their life cycle.
Trends and Threats
This species is protected and rare in its range.
Relation to Humans
The ponds where the frogs gather to breed have become tourist attractions.
Wilkinson, J. (2003). ''Kinugasa flying frog, Rhacophorus arboreus.'' Grzimek's Animal Life Encyclopedia, Volume 6, Amphibians. 2nd edition. M. Hutchins, W. E. Duellman, and N. Schlager, eds., Gale Group, Farmington Hills, Michigan.
Written by Peera Chantasirivisal (Kris818 AT berkeley.edu), URAP , UC Berkeley
First submitted 2005-10-13
Edited by Kellie Whittaker (2008-01-03)
Species Account Citation: AmphibiaWeb 2008 Rhacophorus arboreus: Kinugasa Flying Frog <http://amphibiaweb.org/species/4496> University of California, Berkeley, CA, USA. Accessed Jul 18, 2018.
Feedback or comments about this page.
Citation: AmphibiaWeb. 2018. <http://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 18 Jul 2018.
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Researchers have for the first time used a gene editing technique to successfully cure a genetic condition in a mouse model.
Researchers have developed a gentle, contact-free method that uses sound waves to separate circulating tumour cells from blood samples quickly and efficiently enough for clinical use.
New research could allow us greater control over what happens to genetically modified organisms once they’re in the wild.
CRISPR gene drives have been tested in laboratory mice for the first time, offering a way in which multiple genes in mice can be altered to model complex multigenic human diseases. Could this step eventually lead to the eradication of pest species or is the technology still too controversial?
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Researchers have come up with a tool that offers a means of control over engineered cells, and it comes from a seemingly unlikely source — the hepatitis C genome.
Researchers at Caltech have developed an artificial neural network made out of DNA that can solve a classic machine learning problem: Correctly identifying handwritten numbers.
Chinese investors have poured more money into the US biotech market in the first six months of 2018 than they did in the entirety of last year.
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Dendritic cells monitor foreign substances in the body and communicate whether they present a danger to the rest of the immune system. Emory immunologists have developed a sensitive method to detect and follow dendritic cells by marking them with a change in their DNA, and have discovered that they are more numerous and longer lived than other scientists had previously observed. Their research uses a gene gun, which shoots DNA into the skin using microscopic gold pellets, and could lead to a faster and simpler way to vaccinate against emerging diseases like West Nile virus, SARS, or hepatitis C.
The research was published online August 10, and will appear in the journal Nature Immunology in September. Lead authors are Sanjay Garg PhD, postdoctoral fellow, and Joshy Jacob, PhD assistant professor of microbiology and immunology at Emory University School of Medicine and the Yerkes National Primate Research Center. Both are members of the Emory Vaccine Center.
Dendritic cells, the security cameras of the immune system, derive their name from their finger-like projections. They continually capture external proteins, digest the proteins into fragments, and display those fragments on their surfaces. T cells, the police who watch the cameras, have the ability to examine the fragments on the dendritic cells surfaces and sound the alarm to the rest of the immune system if they determine that those fragments are dangerous. Although other kinds of cells also have the ability to present fragments of foreign proteins to the immune system, dendritic cells are the most proficient, and immunologists call them "professional" antigen-presenting cells.
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Ecology and Conservation of Estuarine Ecosystems: Lake St. Lucia as a Global Model (BOK)
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St Lucia is the world's oldest protected estuary and Africa's largest estuarine system. It is also the centerpiece of South Africa's first UNESCO World Heritage Site, the iSimangaliso Wetland Park, and has been a Ramsar Wetland of International Importance since 1986. Knowledge of its biodiversity, geological origins, hydrology, hydrodynamics and the long history of management is unique in the world. However, the impact of global change has culminated in unprecedented challenges for the conservation and management of the St Lucia system, leading to the recent initiation of a project in support of its rehabilitation and long-term sustainability. This timely volume provides a unique source of information on the functioning and management of the estuary for researchers, students and environmental managers. The insights and experiences described build on over 60 years of study and management at the site and will serve as a valuable model for similar estuaries around the world.
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|Leverandør||Bertram Trading Ltd||Andre medvirkende||Derek D. Stretch, Renzo Perissinotto, Ricky H. Taylor|
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Study Finds ‘Microbial Clock’ may Help Determine Time of Death
News Oct 21, 2013
The clock is essentially the lock-step succession of bacterial changes that occur postmortem as bodies move through the decay process. And while the researchers used mice for the new study, previous studies on the human microbiome – the estimated 100 trillion or so microbes that live on and in each of us – indicate there is good reason to believe similar microbial clocks are ticking away on human corpses, said Jessica Metcalf, a CU-Boulder postdoctoral researcher and first author on the study.
“While establishing time of death is a crucial piece of information for investigators in cases that involve bodies, existing techniques are not always reliable,” said Metcalf of CU-Boulder’s BioFrontiers Institute. “Our results provide a detailed understanding of the bacterial changes that occur as mouse corpses decompose, and we believe this method has the potential to be a complementary forensic tool for estimating time of death.”
Currently, investigators use tools ranging from the timing of last text messages and corpse temperatures to insect infestations on bodies and “grave soil” analyses, with varying results, she said. And the more days that elapse following a person’s demise, the more difficult it becomes to determine the time of death with any significant accuracy.
Using high-technology gene sequencing techniques on both bacteria and microbial eukaryotic organisms like fungi, nematodes and amoeba postmortem, the researchers were able to pinpoint time of mouse death after a 48-day period to within roughly four days. The results were even more accurate following an analysis at 34 days, correctly estimating the time of death within about three days, said Metcalf.
A paper on the subject was published Sept. 23 in the new online science and biomedical journal, eLIFE, a joint initiative of the Howard Hughes Medical Institute, the Max Planck Society and the Wellcome Trust Fund. The study was funded by the National Institute of Justice.
The researchers tracked microbial changes on the heads, torsos, body cavities and associated grave soil of 40 mice at eight different time points over the 48-day study. The stages after death include the “fresh” stage before decomposition, followed by “active decay” that includes bloating and subsequent body cavity rupture, followed by “advanced decay,” said Chaminade University forensic scientist David Carter, a co-author on the study.
“At each time point that we sampled, we saw similar microbiome patterns on the individual mice and similar biochemical changes in the grave soil,” said Laura Parfrey, a former CU-Boulder postdoctoral fellow and now a faculty member at the University of British Columbia who is a microbial and eukaryotic expert. “And although there were dramatic changes in the abundance and distribution of bacteria over the course of the study, we saw a surprising amount of consistency between individual mice microbes between the time points -- something we were hoping for.”
As part of the project, the researchers also charted “blooms” of a common soil-dwelling nematode well known for consuming bacterial biomass that occurred at roughly the same time on individual mice during the decay period. “The nematodes seem to be responding to increases in bacterial biomass during the early decomposition process, an interesting finding from a community ecology standpoint,” said Metcalf.
“This work shows that your microbiome is not just important while you’re alive,” said CU-Boulder Associate Professor Rob Knight, the corresponding study author who runs the lab where the experiments took place. “It might also be important after you're dead.”
The research team is working closely with assistant professors Sibyl Bucheli and Aaron Linne of Sam Houston State University in Huntsville, Texas, home of the Southeast Texas Applied Forensic Science Facility, an outdoor human decomposition facility known popularly as a “body farm.” The researchers are testing bacterial signatures of human cadavers over time to learn more about the process of human decomposition and how it is influenced by weather, seasons, animal scavenging and insect infestations.
The new study is one of more than a dozen papers authored or co-authored by CU-Boulder researchers published in the past several years on human microbiomes. One of the studies, led by Professor Noah Fierer, a co-author on the new study, brought to light another potential forensic tool -- microbial signatures left on computer keys and computer mice, an idea enthralling enough it was featured on a “CSI: Crime Scene Investigation” television episode.
“This study establishes that a body’s collection of microbial genomes provides a store of information about its history,” said Knight, also an associate professor of chemistry and biochemistry and a Howard Hughes Medical Institute Early Career Scientist. “Future studies will let us understand how much of this information, both about events before death -- like diet, lifestyle and travel -- and after death can be recovered.”
In addition to Metcalf, Fierer, Knight, Carter and Parfrey, other study authors included Antonio Gonzalez, Gail Ackerman, Greg Humphrey, Mathew Gebert, Will Van Treuren, Donna Berg Lyons and Kyle Keepers from CU-Boulder, former BioFrontiers doctoral student Dan Knights from the University of Minnesota, and Yan Go and James Bullard from Pacific Biosciences in Menlo Park, Calif. Keepers participated in the study as an undergraduate while Gonzalez, now a postdoctoral researcher, was a graduate student during the study.
“There is no single forensic tool that is useful in all scenarios, as all have some degree of uncertainty,” said Metcalf. “But given our results and our experience with microbiomes, there is reason to believe we can get past some of this uncertainty and look toward this technique as a complementary method to better estimate time of death in humans.”
Gene sequencing equipment for the study included machines from Illumina of San Diego and Pacific Biosciences of Menlo Park, Calif. The Illumina data were generated at CU-Boulder in the BioFrontiers Next Generation Sequencing Facility.
You Thought Your Bread was Stale!News
At an archaeological site in northeastern Jordan, researchers have discovered the charred remains of a flatbread baked by hunter-gatherers 14,400 years ago. It is the oldest direct evidence of bread found to date, predating the advent of agriculture by at least 4,000 years.READ MORE | <urn:uuid:001488c7-8edb-4933-a72f-70b0c2226bc5> | 3.109375 | 1,380 | News Article | Science & Tech. | 18.877346 | 95,646,616 |
- Open Access
Long-term trends in geomagnetic daily variation
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences. 2007
Received: 11 September 2006
Accepted: 19 February 2007
Published: 8 June 2007
Long-term changes in the magnetic environment of the Earth are of interest to those studying space weather and climate change, particularly in the upper atmosphere. In this paper we examine long-term changes in daily variation as derived from hourly mean values from 14 geomagnetic observatories around the world. Their time series date back to the beginning of the 20th century. We find that there are similar features in all the records, with peaks in the amplitudes of the daily variation occurring in the 1950s and 1980s, and a small upward trend of 1.3 nT/century corresponding to an increase of over 10%. The extrema coincide with those seen in solar irradiance proxy data, in particular the F10.7 flux density dataset which starts in 1947. | <urn:uuid:58ad7a51-3a6e-4edf-bd80-dfe09476b008> | 2.703125 | 244 | Academic Writing | Science & Tech. | 37.320673 | 95,646,629 |
+44 1803 865913
By: Butterfly Conservation
36 pages, colour photos
This report reveals that the moth population of Britain is in serious decline, causing concern for the future of many species of birds, bats and several small mammals that feed on them.
Since 1968, the Rothamsted network of light traps has been recording numbers of larger moths caught every night from hundreds of locations across Britain. This provides one of the longest-running and geographically extensive data sets on insect populations anywhere in the world. Analysis of this data set, carried out by Rothamsted Research and Butterfly Conservation, has generated national population trends for hundreds of common moths for the first time.
The total number of moths recorded in Rothamsted trap samples has declined by a third since 1968. Population trends were generated for 337 moth species. Two thirds (226 species) show a decreasing population trend over the 35 year study. Such widespread declines are likely to be having detrimental knock-on effects on other organisms.
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Particulate matter sinking to the deep-sea floor at 2000 M in the Tongue of the Ocean, Bahamas, with a description of a new sedimentation trap
MetadataShow full item record
LocationTongue of the Ocean
A sedimentation trap for use just above the deep-sea floor was free-fallen to a depth of 2050 m in the Tongue of the Ocean canyon on January 3, 1974. On March 6, it was successfully recovered with the assistance of D.S.R.V. Alvin. The trap has a base 1 m square and a height of 30 cm. At the trap bottom are filters to retain falling particles. Two spring-powered sliding doors, each 1 m x 0.5 m, are used to close off the lower 2 cm of the trap during ascent to prevent disturbance of the particles collected on the filters. Total carbon on the filters as determined by high temperature combustion averaged 2301 mgC/m2 or an average on a daily basis of 36.5 mgC/m2. Similar filter aliquots were treated with cold phosphoric acid to eliminate the inorganic fraction. The resulting carbon values (X =: 5.7 mgC/m2/day) suggest 14% of the total carbon reaching the sea floor at 2000 m in this area is organic in origin. Fecal material is one readily identifiable component of the material contributing to the organic fraction. Counts of fecal pellets resulted in an estimate of an average of ~650 pellets/m2/day. Average pellet length was 241 μm and diameter was 109 μm. In laboratory experiments the pellets sank at rates varying from 50 m/day to 941 m/day (X at 5°C =159 m/day). Comparison of the sedimentation trap estimates of organic carbon input to the sea floor in this area with benthic energy requirements indicates that rapidly sinking small particulate matter could supply approximately 14% of the metabolic requirements of the benthos.
Originally published in Journal of Marine Research 34 (1976): 341-354
Suggested CitationTechnical Report: Wiebe, Peter H., Boyd, Steven H., Winget, Clifford L., "Particulate matter sinking to the deep-sea floor at 2000 M in the Tongue of the Ocean, Bahamas, with a description of a new sedimentation trap", 1976-09, DOI:10.1575/1912/1792, https://hdl.handle.net/1912/1792
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Fatty acids and fatty acid esters of particulate matter collected in sediment traps in the Peru upwelling area R/V Knorr Cruise 73, February/March 1978 Wakeham, Stuart G.; Livramento, Joaquim B.; Farrington, John W. (Woods Hole Oceanographic Institution, 1983-09)Particulate matter samples were collected using free-drifting sediment traps in the Peru upwelling area in 1978 to assess the vertical flux and organic composition of lipids associated with particles sinking out of ...
Widespread influence of resuspended sediments on oceanic particulate organic carbon : insights from radiocarbon and aluminum contents in sinking particles Hwang, Jeomshik; Druffel, Ellen R. M.; Eglinton, Timothy I. (American Geophysical Union, 2010-11-20)Particulate organic carbon (POC) in the ocean often exhibits more depleted radiocarbon contents (lower Δ 14C values) than expected if its sole source were POC recently synthesized by primary production and export from the ...
Remote acoustic sensing of the particulate phase of industrial chemical wastes and sewage sludge : report on the seasonal variability of the dispersion of the particulate phase as observed from three cruises, July 1977, January-February 1978, and April 1978 Orr, Marshall H.; Baxter, Lincoln; Hess, Frederick R. (Woods Hole Oceanographic Institution, 1980-01)The seasonal variability of the dispersion of the particulate phase of industrial chemical waste has been studied with acoustic backscattering techniques at Deep Water Dumpsite 106 (DWD 106). The vertical dispersion of ... | <urn:uuid:d499ee38-6b9b-4d93-aed5-314b0ec1f206> | 3.109375 | 869 | Academic Writing | Science & Tech. | 53.063821 | 95,646,670 |
Water-soluble and crosslinked water-insoluble polymers having suitable functional groups are capable to retain metal ion pollutants through ion exchange or complexation, allowing their remove from contaminated water streams. The polymeric sorbents can be obtained by polymerization of monomers containing the functional groups or by post-functionalization, also, with the aim to enhance their performance, the sorbents can be loaded with inorganic (nano)particles or coupled with membrane processes. This paper is an overview of the versatile polymer materials containing different functional groups at the main or side chain to remove hazardous inorganic species. These materials include water-insoluble, nanocomposite and water-soluble polymers. Water-insoluble polymers and nanocomposites are used in adsorption and ion exchange processes, whereas water-soluble polymers are employed with ultrafiltration membranes in the liquid-phase polymer-based retention technique.
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General Relativity Notes
by Edmund Bertschinger
Publisher: MIT 1999
Number of pages: 156
Working with GR, particularly with the Einstein field equations, requires some understanding of differential geometry. In this text we will develop the essential mathematics needed to describe physics in curved spacetime. These notes assume familiarity with special relativity.
Download or read it online for free here:
(multiple PDF files)
by Hermann Weyl - Methuen & Co.
A classic of physics -- the first systematic presentation of Einstein's theory of relativity. Long one of the standard texts in the field, this excellent introduction probes deeply into Einstein's general relativity, gravitational waves and energy.
by V. L. Kalashnikov - arXiv
The author presents the pedagogical introduction to relativistic astrophysics and cosmology, which is based on computational and graphical resources of Maple 6. The knowledge of basics of general relativity and differential geometry is supposed.
by Gerard 't Hooft - Utrecht University
Contents: The Metric of Space and Time; Curved coordinates; A short introduction to General Relativity; Gravity; The Schwarzschild Solution; The Chandrasekhar Limit; Gravitational Collapse; The Reissner-Nordstrom Solution; Horizons; and more.
by Bernard F Schutz, Franco Ricci - arXiv
Notes of lectures for graduate students, covering the theory of linearized gravitational waves, their sources, and the prospects at the time for detecting gravitational waves. The lectures remain of interest for pedagogical reasons. | <urn:uuid:4aea3ab3-a984-4275-be4c-b03e0e165972> | 3.234375 | 320 | Content Listing | Science & Tech. | 15.843531 | 95,646,724 |
Even with 'mixed fibers' chromatin does not change its 3-D structure
"Interphase" refers to the period in the cell cycle in which chromosomes spend most of their time. During this phase, in between mitoses, chromosomes live "dissolved'' in the nucleus where they carry out the processes required for the duplication of genetic material.
Our current knowledge regarding the behaviour of chromosomes during interphase is unfortunately quite limited; for example, we would need to know more about the three-dimensional structure of the chromatin filament - the long molecule that makes up the chromosomes and that consists of DNA and other proteins - and how it changes in time and space. The shape of the chromosome is in fact important for its function as it allows or prevents access to portions of genetic code for the duplication processes.
In addition to experimental observation, another important method of study is computer simulation, based on theoretical models of chromatin. A new study has extended work done previously, which used a simpler model of chromatin consisting up of a single fibre.
In the new study, the filament could be made up of two types of fibre, one thicker and one thinner, in varying proportions. Experimental studies have indeed demonstrated the existence of two main types of chromatin, with thicknesses of 10 or 30 nm.
In the study, the scientists made molecular dynamics simulations for model chromosomes in various conditions: they added increasingly large amounts of 10 nm fibre to the homopolymer chromatin, consisting of the stiffer 30 nm fibre only.
The model used in the new study, while a simplification of the real molecule, makes the simulation more realistic. The aim of the study was to evaluate whether small-scale modifications in the chromatin fibre lead to large-scale changes in the behavior of the chromosome.
"Even after the introduction of the more flexible second fibre, the chromosome remains spatially stable" explains Ana-Maria Florescu, first author of the study and SISSA research scientist. "More in detail", adds Angelo Rosa, SISSA research fellow who coordinated the work, "we found that reorganization occurs only on spatial scales below 0.1 Mbp (million base pairs) and on time scales shorter than a few seconds".
One significant implication of this study concerns the techniques used for the experimental observation of the fibres: those most commonly used today have inadequate resolution to be able to observe this type of reorganization, so we aim to develop new methodologies (like the FISH technique based on oligonucleotides) able to visualize even genome distances smaller than 0.1 Mbp.
Federica Sgorbissa | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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1. A fisherman catches two striped bass. The smaller of the two has a measured length of 93.46 cm(two decimal places, four significant figures), and the larger fish has a measured length of 135.3cm (one decimal place, four significant figures). What is the total length of fish caught for the day?
2. How many significant figures are there in (a) 78.9 + 0.2, (b) 3.788 X 10^9, (c) 2.46 X 10^-6, (d) 0.003^2.
3. The radius of a circle is measured to be (10.5 + 0.2) m. Calculate (a) the area and (b) the circumference of the circle, and give the uncertainty in each value.
4. Carry out the following arithmetic operations: (a) the sum of the measured of the values 756, 37.2, 0.83, and 2.5; (b) the product 0.003^2 X 356.3; (c) the product 5.620 X Pie
5. A fathom is a unit of length, usually reserved for measuring the depth of water. A fathom is approximately 6 ft in length. Take the distance from Earth to the Moon to be 250 000 miles, and use the given approximation to find the distance to fathoms.
6. Suppose your hair grows at the rate of 1/32 inch per day. Find the rate at which it grows in nanometers per second. Because the distance between atoms in a molecule is on the order of 0.1 nm.
7. A house is 50.0 ft long and 26 ft wide and has 8.0-ft-high ceilings. What is the volume of the interior of the house in cubic meters and in cubic meters and in cubic centimeters?© BrainMass Inc. brainmass.com July 23, 2018, 1:51 pm ad1c9bdddf
This solution is comprised of detailed explanation and step-by-step calculation of the given problems and provides students with a clear perspective of the underlying concepts. | <urn:uuid:0f2f081b-93cf-450e-a2d6-8b6df7796f72> | 3.734375 | 442 | Tutorial | Science & Tech. | 93.999445 | 95,646,744 |
After days of anticipation a fresh breeze rises through a sunny field, creating a flurry of dancing white fluff. A busy cacophony of tiny parachutes rise and there is a wave of new excitement as young dandelion seeds finally break free from their parents and launch into the unknown. Finally, they’re on their way, with a journey ahead of them that’s potentially miles long. With a bit of luck they’ll produce their own intrepid seeds in a few months, and in doing so defy a grumpy gardener who should have pulled the weed’s roots out properly.
Wind dispersal may be one of the first methods of seed dispersal we think of, but there are many other ways in which plants disperse their propagules. These are structures with the capacity to give rise to a new plant, for example a seed, a spore, or a part of the vegetative body capable of independent growth if detached from the parent (Biology Online, 2015). Types of propagule dispersal can be split into two main categories: autochory, where the plant itself carries out the dispersal of its propagules, and allochory, where the plant exploits different means of propagule transport such as animal vectors.
Self-dispersal mechanisms include:
- barochory – transport via gravity
- blastochory – dispersal via runners
- herpochory – transport via active creeping
- ballochory – self seeding
(Schulze et al., 2005)
Barochory is a very simple seed dispersal mechanism, whereby plants, such as apple trees, simply distribute seeds by allowing them to drop to the ground. The fruits containing the seeds are often large, heavy and relatively round so they can then roll away. Seeds may later succumb to another form of dispersal, perhaps via water when it rolls into a river or sea, or an animal if it’s eaten whole and excreted somewhere else.
Plants such as grasses can perform vegetative reproduction – a process by which new organisms grow directly from plant stems called runners, rather than developing from seeds or spores. This is a type of asexual reproduction, which results in individuals with the same genetic code. Runners that lie underground are called rhizomes and those that shoot along the ground are called stolons. This method of reproductive enables plants to produce large quantities of offspring quickly and easily.
Herpochory is a curious dispersal mechanism which involves seeds effectively crawling along the ground. This has probably made some farmers somewhat surprised to find their oat seeds have escaped from their husks and crept along the ground after being left for some time. This movement is achieved by hairs or bristles that twist in different ways as they react to the surrounding level of humidity – in other words they are hygroscopic. The tails of oat seeds untwist when they’re damp and twist again when they’re dry.
On a warm summers day in the country you may here the friendly crackling of a gorse bush (Ulex europaeus). Their seeds suddenly ‘pop’ out of their seedpods which have dried and twisted in the sun and consequently split open. These seeds can be fired a few metres away from the parent, demonstrating a prime example of ballochory.
Allochory (dispersal via a vector) includes:
- anemochory – transport via wind
- hydrochory – transport in water
- zoochory – dispersal via animals
- hemerochory – dispersal by man
(Schulze et al., 2005)
Anemochory is well demonstrated by the many species of tumbleweeds – the above ground structure of a plant which detaches is dry weather and rolls over ground in windy conditions, thereby spreading its seeds or spores. The infamous Salsola tragus is the tumbleweed that’s closely associated with classic Wild West films, yet it’s not native to North America, in fact it’s from Russia. Because of its efficient reproductive strategy it can now be found in nearly all American states.
The coconut, which is a type of fruit called a drupe, not a nut, is a classic sea voyager. It’s hard, woody shell protects the delicate embryo inside from salty water which can damage cells via osmosis. It’s able to float so well because it has a large volume and plenty of air inside thanks to the cavity just under the outer coat. This air-filled cavity is filled with light, stringy fibres called coir. Coconuts can float hundreds and sometimes thousands of kilometres between tropical islands.
Most dog owners will probably have experienced the woes of brushing burrs out of dog fur. These are seeds which have the ideal adaptation of hooks or teeth that latch onto animals and effectively hitch a ride. But have you heard of seed dispersal by ants? This specialist form of zoochory is called myrmecochory. Attached to these types of seeds are external appendages (called elaiosomes) which are rich in nutrients and are therefore a scrumptious meal for ants. Seeds are carried back to ants’ nests for consumption of this nutrient-rich treat, but the seeds are left undamaged – they end up with a favourable place to germinate and escape above-ground seed predation.
Being animals ourselves, one could argue that hemerochory is a type of zoochory. With the great distances we travel nowadays, hemerochory plays a huge role in the wide dispersal of some plants, even hitching rides to different countries on our shoes, cars and potentially skin. A result of this large-scale dispersal can unfortunately be the introduction of foreign plants which can become invasive in new environments and damage native species’ populations. And we of course spread millions of seeds each year through agriculture.
In conclusion, there’s an incredible diversity of dispersal methods out there used to distribute plant offspring far and wide, from crawling oats to exploding gorse. These help the next generation of plants to survive and prosper. In general, the further away offspring can get from its parent plant the less likely it will suffer from density-dependant seedling predators and pathogens, and potentially the less competition it has with its parent. The need for plants to disperse their offspring has resulted in truly innovative and fascinating dispersal solutions, demonstrating the creativeness of nature.
Baldwin, Cradock and Joy, (1833), The Westminster Review, p.440
Biology Online, (2015), Propagule, [online], available at: http://www.biology-online.org/dictionary/Propagule Accessed 24 January 2015
Encyclopeadia Britannica, (2015), Seed and fruit: self-dispersal, [online], available at: http://www.britannica.com/EBchecked/topic/532368/seed-and-fruit/75925/Self-dispersal Accessed 21 January 2015
Janick, J., Paull, R., (2008), Encyclopedia of fruits and nuts, CABI, p.107-108
Schulze, S., Beck, E., Müller-Hohenstein, K., (2005), Plant Ecology, Springer Science and Business Media, p. 542-543
Photos sourced from Wikimedia Commons (http://commons.wikimedia.org/wiki/Category:Images):
- Taken April 2012 by Sage Ross: A cloud of dandelion seeds against a dark background, produce by shaking a handful of dandelion clocks above the field of view in my back yard
- Taken February 2005 by Macleay Grass Man: Chloris gayana stolon, Austral Eden, New South Wales, Australia
- Taken December 2013 by EriKolaborator: Nicelyous
- Taken October 2007 by Huw Williams: Burrs in Warren County, Indiana.
2,788 total views, 1 views today | <urn:uuid:004ee56b-58ed-4885-bc13-518ce6324fc0> | 4.125 | 1,672 | Knowledge Article | Science & Tech. | 43.224274 | 95,646,774 |
Turning-point filtering is a method to focus acoustic energy from a vertical line array receiver into an oceanographically meaningful image. The turning-point filter is a simple modification of the linear beamformer which compensates for the sound-speed variation in the water column. Focused peaks in the image (phase-speed, group- speed space) can be regarded as accurate samples of the underlying dispersion curve whenever the WKBJ approximation is valid. Applying this method to real data, still fails to produce a useful observable because of small-scale variations in the ocean. The ocean acoustic waveguide has limited space, time, and frequency coherences which limit the image sharpness. Accounting for this by incoherently combining the limited coherent subspaces generates easily measured observables as demonstrated.
Matthew A. Dzieciuch,
"Ocean acoustic tomography using turning-point filters", Proc. SPIE 4123, Image Reconstruction from Incomplete Data, (16 November 2000); doi: 10.1117/12.409259; https://doi.org/10.1117/12.409259 | <urn:uuid:3738c923-13c3-4609-bd68-b1207584c325> | 2.828125 | 227 | Academic Writing | Science & Tech. | 35.61514 | 95,646,789 |
Proteins in gel
Biochips carrying thousands of DNA fragments are widely used for examining genetic material. Experts would also like to have biochips on which proteins are anchored. This requires a gel layer which can now be produced industrially.
Several thousand test fields are tightly packed together on the tiny surface of a biochip. They permit the rapid analysis of substances, e.g. for diagnosing allergens in the blood. These biochips are already in widespread use for DNA testing. When it comes to proteins, such chips are difficult to produce. This is because the proteins have a defined three-dimensional structure by which they can interact specifically with other molecules and control biological processes. If they bind to a surface, such as on a biochip, the structure can be destroyed and the protein cannot perform its function.
Research scientists at the Fraunhofer Institute for Applied Polymer Research IAP in Potsdam-Golm have solved this problem. "We have developed a gel - a network of organic molecules - that we can apply to the surface of the biochip," says Dr. Andreas Holländer, group manager at the IAP. "This gel layer is only about 100 to 500 nano-meters thick and consists mainly of water. We thus make the protein believe that it is in a solution, even though it is chemically connected to the network. It feels as if it is in its natural environment and continues to function even though it is on a biochip." Other research groups are working on similar hydrogels. The key feature of the new production technique is that it can be applied in industry, and the gel layers can be manufactured cheaply on a large scale. Usually there are two ways of producing such networks. In the first, complete polymers are chemically bound to the surface. In the second, the polymer molecules are constructed unit by unit on the surface. "Our technique is a mixture of the two known methods. We use larger molecular building blocks to build up the network on the surface," explains Falko Pippig, who is doing his doctorate on this subject at the IAP.
As the hydrogel layers are very thin, substances added from the outside very quickly reach the protein which is in and on this layer. For example, physicians can put blood or urine on the chip and diagnose illnesses. The research scientists have already developed the process fundamentals. Protein biochips could therefore become everyday items of equipment in medical laboratories - the possible applications far exceed those of DNA chips.
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Researchers compared the ecological consequences of variation within species and among species, and found similar effects in many cases
Concerns about biodiversity tend to focus on the loss of species from ecosystems, but a new study suggests that the loss of variation within species can also have important ecological consequences.
Many species play important roles in nature and provide services important to people. For example, many fish species are harvested for food, and many insect species pollinate wild and cultivated plants. The loss of these species may mean the loss of ecosystem services, a major motivation for preventing species extinctions. The new study, published December 4 in Nature Ecology & Evolution, found that the ecological effects of within-species variation may be far reaching and often rival those of species themselves.
"It's not just the loss of whole species that we should be concerned about. We also need to pay more attention to the ecological consequences of variation within species," said lead author Simone Des Roches, a postdoctoral researcher at UC Santa Cruz.
Variation within species affects how organisms interact with each other and their surrounding environment. For example, the size of a fish's mouth, known as its gape, determines the size of prey it can eat. And the variety of noxious chemicals a plant produces controls which insects chew its leaves. Much of the time, traits like fish gape and leaf chemistry are adaptive. They help organisms live in a changing world. However, much less is known about how variation within species affects broader ecosystems.
Variation within species can influence ecosystems through both direct and indirect ecological effects. Direct ecological effects can occur when trait differences affect the abundance or types of prey or resources an organism consumes, such as when the gape size of fish influences the kinds of plankton prey that survive in lakes or when leaf chemistry determines the grazing insects that inhabit a field. However, those prey or grazers often have diverse other interactions and roles in ecosystems that can be further altered. Ecological effects caused by such chains of interactions are known as "indirect effects."
The study by Des Roches and her collaborators examined all available studies that compared the ecological effects of variation within species to the effects of species presence (removing the species or replacing it with another). They included 25 studies measuring a total of 144 different ecological responses from various types of plants, animals, and fungi. Their results show that variation within species, such as the effects of large- and small-gaped fish populations on zooplankton, are often similar to--and can sometimes be stronger than--species effects.
On average, species tend to have larger effects on ecosystems. Yet over a third of studies examined showed that swapping different variants of the same species had similar ecological effects as removing that species entirely or replacing it with a completely different species.
"Traditionally, ecologists have focused on the ecological importance of biodiversity among species. This paper broadly establishes within-species biodiversity as critical for ecology," said coauthor Eric Palkovacs, associate professor of ecology and evolutionary biology at UC Santa Cruz.
Nearly half of all the studies documented at least one ecological response that was more strongly affected by variation within species than by its presence. In a surprising result, within-species variation was shown to have the largest impacts on organisms that the focal species wasn't directly consuming or evading. In other words, trait variation within species appears most important for indirect effects.
The study suggests that protecting trait variation within species is not only important for the future of evolution, but also potentially critical for the functioning of current and future ecosystems, according to Palkovacs. "This is a sobering thought given that human activity is causing within-species variation to be lost at a far greater rate than the extinction of entire species," he said.
In addition to Des Roches and Palkovacs, the coauthors of the paper include David Post at Yale University; Nash Turley at the University of Central Florida; Joseph Bailey and Jennifer Schweitzer at the University of Tennessee; Andrew Hendry at McGill University; and Michael Kinnison at the University of Maine. This work was funded by the Quebec Centre for Biodiversity, the UC Institute for the Study of Ecological and Evolutionary Climate Impacts, the David and Lucile Packard Foundation, and the National Science Foundation.
Tim Stephens | EurekAlert!
Scientists uncover the role of a protein in production & survival of myelin-forming cells
19.07.2018 | Advanced Science Research Center, GC/CUNY
NYSCF researchers develop novel bioengineering technique for personalized bone grafts
18.07.2018 | New York Stem Cell Foundation
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
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Forest Soils of the South
The impacts of acidic deposition depend strongly on the specific chemistry of each soil and the nutrient cycles within each ecosystem. To provide perspective on the general characteristics, patterns, and diversity of forest soils in the South, the general geomorphology of the region and the major features of the most important and extensive soil groups are described herein.
KeywordsForest Soil Coastal Plain Basic Cation Base Saturation Soil Survey Staff
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An Intro to Encryption in Python 3
An Intro to Encryption in Python 3
Learn how to encrypt and decrypt strings using the PyCrypto and cryptography libraries.
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Python 3 doesn’t have very much in its standard library that deals with encryption. Instead, you get hashing libraries. We’ll take a brief look at those in the chapter, but the primary focus will be on the following 3rd party packages: PyCrypto and cryptography. We will learn how to encrypt and decrypt strings with both of these libraries.
If you need secure hashes or message digest algorithms, then Python’s standard library has you covered in the hashlib module. It includes the FIPS secure hash algorithms SHA1, SHA224, SHA256, SHA384, and SHA512 as well as RSA’s MD5 algorithm. Python also supports the adler32 and crc32 hash functions, but those are in the zlib module.
One of the most popular uses of hashes is storing the hash of a password instead of the password itself. Of course, the hash has to be a good one or it can be decrypted. Another popular use case for hashes is to hash a file and then send the file and its hash separately. Then the person receiving the file can run a hash on the file to see if it matches the hash that was sent. If it does, then that means no one has changed the file in transit.
Let’s try creating an md5 hash:
>>> import hashlib >>> md5 = hashlib.md5() >>> md5.update('Python rocks!') Traceback (most recent call last): File "<pyshell#5>", line 1, in <module> md5.update('Python rocks!') TypeError: Unicode-objects must be encoded before hashing >>> md5.update(b'Python rocks!') >>> md5.digest() b'\x14\x82\xec\x1b#d\xf6N}\x16*+[\x16\xf4w'
Let’s take a moment to break this down a bit. First off, we import hashlib and then we create an instance of an md5 HASH object. Next, we add some text to the hash object and we get a traceback. It turns out that to use the md5 hash, you have to pass it a byte string instead of a regular string. So we try that and then call it’s digest method to get our hash. If you prefer the hex digest, we can do that too:
>>> md5.hexdigest() '1482ec1b2364f64e7d162a2b5b16f477'
There’s actually a shortcut method of creating a hash, so we’ll look at that next when we create our sha512 hash:
>>> sha = hashlib.sha1(b'Hello Python').hexdigest() >>> sha '422fbfbc67fe17c86642c5eaaa48f8b670cbed1b'
As you can see, we can create our hash instance and call its digest method at the same time. Then we print out the hash to see what it is. I chose to use the sha1 hash as it has a nice short hash that will fit the page better. But it’s also less secure, so feel free to try one of the others.
Python has pretty limited support for key derivation built into the standard library. In fact, the only method that hashlib provides is the pbkdf2_hmac method, which is the PKCS#5 password-based key derivation function 2. It uses HMAC as its psuedorandom function. You might use something like this for hashing your password as it supports a salt and iterations. For example, if you were to use SHA-256 you would need a salt of at least 16 bytes and a minimum of 100,000 iterations.
As a quick aside, a salt is just random data that you use as additional input into your hash to make it harder to “unhash” your password. Basically it protects your password from dictionary attacks and pre-computed rainbow tables.
Let’s look at a simple example:
>>> import binascii >>> dk = hashlib.pbkdf2_hmac(hash_name='sha256', password=b'bad_password34', salt=b'bad_salt', iterations=100000) >>> binascii.hexlify(dk) b'6e97bad21f6200f9087036a71e7ca9fa01a59e1d697f7e0284cd7f9b897d7c02'
Here we create a SHA256 hash on a password using a lousy salt but with 100,000 iterations. Of course, SHA is not actually recommended for creating keys of passwords. Instead you should use something like scrypt instead. Another good option would be the 3rd party package, bcrypt. It is designed specifically with password hashing in mind.
The PyCrypto package is probably the most well known 3rd party cryptography package for Python. Sadly PyCrypto’s development stopping in 2012. Others have continued to release the latest version of PyCryto so you can still get it for Python 3.5 if you don’t mind using a 3rd party’s binary. For example, I found some binary Python 3.5 wheels for PyCrypto on Github (https://github.com/sfbahr/PyCrypto-Wheels).
Fortunately, there is a fork of the project called PyCrytodome that is a drop-in replacement for PyCrypto. To install it for Linux, you can use the following pip command:
pip install pycryptodome
Windows is a bit different:
pip install pycryptodomex
If you run into issues, it’s probably because you don’t have the right dependencies installed or you need a compiler for Windows. Check out the PyCryptodome website for additional installation help or to contact support.
Also worth noting is that PyCryptodome has many enhancements over the last version of PyCrypto. It is well worth your time to visit their home page and see what new features exist.
Encrypting a String
Once you’re done checking their website out, we can move on to some examples. For our first trick, we’ll use DES to encrypt a string:
>>> from Crypto.Cipher import DES >>> key = 'abcdefgh' >>> def pad(text): while len(text) % 8 != 0: text += ' ' return text >>> des = DES.new(key, DES.MODE_ECB) >>> text = 'Python rocks!' >>> padded_text = pad(text) >>> encrypted_text = des.encrypt(text) Traceback (most recent call last): File "<pyshell#35>", line 1, in <module> encrypted_text = des.encrypt(text) File "C:\Programs\Python\Python35-32\lib\site-packages\Crypto\Cipher\blockalgo.py", line 244, in encrypt return self._cipher.encrypt(plaintext) ValueError: Input strings must be a multiple of 8 in length >>> encrypted_text = des.encrypt(padded_text) >>> encrypted_text b'>\xfc\x1f\x16x\x87\xb2\x93\x0e\xfcH\x02\xd59VQ'
This code is a little confusing, so let’s spend some time breaking it down. First off, it should be noted that the key size for DES encryption is 8 bytes, which is why we set our key variable to a size letter string. The string that we will be encrypting must be a multiple of 8 in length, so we create a function called pad that can pad any string out with spaces until it’s a multiple of 8. Next we create an instance of DES and some text that we want to encrypt. We also create a padded version of the text. Just for fun, we attempt to encrypt the original unpadded variant of the string which raises a ValueError. Here we learn that we need that padded string after all, so we pass that one in instead. As you can see, we now have an encrypted string!
Of course, the example wouldn’t be complete if we didn’t know how to decrypt our string:
>>> des.decrypt(encrypted_text) b'Python rocks! '
Fortunately, that is very easy to accomplish as all we need to do is call the **decrypt** method on our des object to get our decrypted byte string back. Our next task is to learn how to encrypt and decrypt a file with PyCrypto using RSA. But first we need to create some RSA keys!
Create an RSA Key
If you want to encrypt your data with RSA, then you’ll need to either have access to a public / private RSA key pair or you will need to generate your own. For this example, we will just generate our own. Since it’s fairly easy to do, we will do it in Python’s interpreter:
>>> from Crypto.PublicKey import RSA >>> code = 'nooneknows' >>> key = RSA.generate(2048) >>> encrypted_key = key.exportKey(passphrase=code, pkcs=8, protection="scryptAndAES128-CBC") >>> with open('/path_to_private_key/my_private_rsa_key.bin', 'wb') as f: f.write(encrypted_key) >>> with open('/path_to_public_key/my_rsa_public.pem', 'wb') as f: f.write(key.publickey().exportKey())
First, we import RSA from Crypto.PublicKey. Then we create a silly passcode. Next we generate an RSA key of 2048 bits. Now we get to the good stuff. To generate a private key, we need to call our RSA key instance’s exportKey method and give it our passcode, which PKCS standard to use and which encryption scheme to use to protect our private key. Then we write the file out to disk.
Next, we create our public key via our RSA key instance’s publickey method. We used a shortcut in this piece of code by just chaining the call to exportKey with the publickey method call to write it to disk as well.
Encrypting a File
Now that we have both a private and a public key, we can encrypt some data and write it to a file. Here’s a pretty standard example:
from Crypto.PublicKey import RSA from Crypto.Random import get_random_bytes from Crypto.Cipher import AES, PKCS1_OAEP with open('/path/to/encrypted_data.bin', 'wb') as out_file: recipient_key = RSA.import_key( open('/path_to_public_key/my_rsa_public.pem').read()) session_key = get_random_bytes(16) cipher_rsa = PKCS1_OAEP.new(recipient_key) out_file.write(cipher_rsa.encrypt(session_key)) cipher_aes = AES.new(session_key, AES.MODE_EAX) data = b'blah blah blah Python blah blah' ciphertext, tag = cipher_aes.encrypt_and_digest(data) out_file.write(cipher_aes.nonce) out_file.write(tag) out_file.write(ciphertext)
The first three lines cover our imports from PyCryptodome. Next we open up a file to write to. Then we import our public key into a variable and create a 16-byte session key. For this example we are going to be using a hybrid encryption method, so we use PKCS#1 OAEP, which is Optimal asymmetric encryption padding. This allows us to write a data of an arbitrary length to the file. Then we create our AES cipher, create some data and encrypt the data. This will return the encrypted text and the MAC. Finally we write out the nonce, MAC (or tag) and the encrypted text.
As an aside, a nonce is an arbitrary number that is only used for crytographic communication. They are usually random or pseudorandom numbers. For AES, it must be at least 16 bytes in length. Feel free to try opening the encrypted file in your favorite text editor. You should just see gibberish.
Now let’s learn how to decrypt our data:
from Crypto.PublicKey import RSA from Crypto.Cipher import AES, PKCS1_OAEP code = 'nooneknows' with open('/path/to/encrypted_data.bin', 'rb') as fobj: private_key = RSA.import_key( open('/path_to_private_key/my_rsa_key.pem').read(), passphrase=code) enc_session_key, nonce, tag, ciphertext = [ fobj.read(x) for x in (private_key.size_in_bytes(), 16, 16, -1) ] cipher_rsa = PKCS1_OAEP.new(private_key) session_key = cipher_rsa.decrypt(enc_session_key) cipher_aes = AES.new(session_key, AES.MODE_EAX, nonce) data = cipher_aes.decrypt_and_verify(ciphertext, tag) print(data)
If you followed the previous example, this code should be pretty easy to parse. In this case, we are opening our encrypted file for reading in binary mode. Then we import our private key. Note that when you import the private key, you must give it your passcode. Otherwise you will get an error. Next we read in our file. You will note that we read in the private key first, then the next 16 bytes for the nonce, which is followed by the next 16 bytes which is the tag and finally the rest of the file, which is our data.
Then we need to decrypt our session key, recreate our AES key and decrypt the data.
You can use PyCryptodome to do much, much more. However we need to move on and see what else we can use for our cryptographic needs in Python.
The Cryptography Package
The cryptography package aims to be “cryptography for humans” much like the requests library is “HTTP for Humans”. The idea is that you will be able to create simple cryptographic recipes that are safe and easy-to-use. If you need to, you can drop down to low=level cryptographic primitives, which require you to know what you’re doing or you might end up creating something that’s not very secure.
If you are using Python 3.5, you can install it with pip, like so:
pip install cryptography
You will see that cryptography installs a few dependencies along with itself. Assuming that they all completed successfully, we can try encrypting some text. Let’s give the Fernet symmetric encryption algorithm. The Fernet algorithm guarantees that any message you encrypt with it cannot be manipulated or read without the key you define. Fernet also support key rotation via MultiFernet. Let’s take a look at a simple example:
>>> from cryptography.fernet import Fernet >>> cipher_key = Fernet.generate_key() >>> cipher_key b'APM1JDVgT8WDGOWBgQv6EIhvxl4vDYvUnVdg-Vjdt0o=' >>> cipher = Fernet(cipher_key) >>> text = b'My super secret message' >>> encrypted_text = cipher.encrypt(text) >>> encrypted_text (b'gAAAAABXOnV86aeUGADA6mTe9xEL92y_m0_TlC9vcqaF6NzHqRKkjEqh4d21PInEP3C9HuiUkS9f' b'6bdHsSlRiCNWbSkPuRd_62zfEv3eaZjJvLAm3omnya8=') >>> decrypted_text = cipher.decrypt(encrypted_text) >>> decrypted_text b'My super secret message'
First off we need to import Fernet. Next we generate a key. We print out the key to see what it looks like. As you can see, it’s a random byte string. If you want, you can try running the generate_key method a few times. The result will always be different. Next we create our Fernet cipher instance using our key.
Now we have a cipher we can use to encrypt and decrypt our message. The next step is to create a message worth encrypting and then encrypt it using the encrypt method. I went ahead and printed our the encrypted text so you can see that you can no longer read the text. To decrypt our super secret message, we just call decrypt on our cipher and pass it the encrypted text. The result is we get a plain text byte string of our message.
This chapter barely scratched the surface of what you can do with PyCryptodome and the cryptography packages. However it does give you a decent overview of what can be done with Python in regards to encrypting and decrypting strings and files. Be sure to read the documentation and start experimenting to see what else you can do!
Published at DZone with permission of Mike Driscoll , DZone MVB. See the original article here.
Opinions expressed by DZone contributors are their own. | <urn:uuid:04e2ec4e-76bc-4c83-aa71-3f0b681020ec> | 3.375 | 3,908 | Tutorial | Software Dev. | 64.092304 | 95,646,841 |
Through a recent study, the researchers in our Department of Psychology were surprised to find that the ‘mental number line’ for congenitally blind people ran in the opposite direction to sighted people, with larger numbers to the left and smaller numbers to the right.
Whereas a sighted person would count 1, 2, 3, 4, 5, the researchers have found that someone blind from birth mentally visualises their number line from right to left, effectively 5, 4, 3, 2, 1.
Senior Lecturer from the Department, Dr Michael Proulx explained: “Our unexpected results relate to the fact that people who were born visually impaired like to map the position of objects in relation to themselves.
“It is likely that this style of spatial representation extends to numbers too, and the right-handed participants mapped the number line from their dominant right hand.”
The study used a novel ‘random number generation’ procedure where volunteers were asked to say numbers while turning their head to the left or the right. This task is linked to how the brain visualises a mental number line.
As part of the study, an international team from Bath, Sabanci University (Turkey) and Taisho University (Japan) compared responses of congenitally blind people, with the adventitiously blind - those who were born with vision - and sighted, but blindfolded, volunteers.
Previous studies have shown that people in Western cultures, where writing runs from left to right, possess a similar mental number line, with small numbers on the left and larger numbers on the right. But in cultures where writing flows from right to left, for example Arabic, people’s mental number lines runs in a similar direction. This is the first time scientists have uncovered that blind individuals in a Western culture also had a right to left number line.
Dr Proulx added: “Remembering and representing numbers is an important skill, and the foundation of mental maths. Visually impaired people are just as good, if not better, at mathematics than sighted people - Georgian Maths Professor and Royal Society Fellow, Nicholas Saunderson as one famous example.
“What makes this work exciting is that Saunderson may have been able to advance mathematics with an entirely different mental representation of numbers than that of sighted contemporaries like Isaac Newton.”
The results of the new study ‘Sensory deprivation: visual experience alters the mental number line’ are published in the journal Behavioural Brain Research. To access the paper see: http://www.sciencedirect.com/science/article/pii/S0166432813007602 .
- To find out more about Dr Proulx’s innovative work helping blind people to ‘see’ the world through hearing watch see our research feature http://www.bath.ac.uk/research/features/how-blind-people-see-the-world | <urn:uuid:925aeb6d-b64e-4ff9-ad12-a6acdb4f9280> | 3.421875 | 611 | News (Org.) | Science & Tech. | 41.177182 | 95,646,844 |
Bands of strong thunderstorms that make up tropical storm Nock-ten were visible in an infrared image captured on July 28 by the Atmospheric Infrared Sounder (AIRS) instrument that flies on NASA's Aqua satellite. The colder the cloud tops, the higher the thunderstorms and the stronger they are, and cloud top temperatures over a large area of Nock-ten were colder than -63 Fahrenheit (-52 Celsius) and the cloud tops likely extended into the tropopause. High, strong thunderstorms like those also can generate heavy rainfall, up to 2 inches (50 mm) per hour. Those in Nock-ten's path can expect heavy rainfall, local flooding, gusty winds and rough surf along coastal areas.
NASA's Aqua satellite passed over the eastern side of Tropical Storm Nock-ten and the AIRS instrument captured this infrared image of the storm's cold cloud tops (purple) and strong thunderstorms on July 28 at 0517 UTC (1:47 a.m. EDT). Hainan Island, China is located to the west and can be seen on the left side of the image. Credit: NASA/JPL, Ed Olsen
AIRS imagery has shown that the convection within Nock-ten has intensified as it moves through the warm waters of the South China Sea. It is expected to strengthen a little more with the warm sea surface temperatures feeding it, and wind shear remaining light.
On July 28, at 1500 UTC (11 a.m. EDT) Tropical Storm Nock-ten was already raining on Hainan Island and headed toward another landfall in Vietnam. Its center was still 464 nautical miles east-southeast of Hanoi, Vietnam near 18.2 North and 113.0 East. Nock-ten's sustained winds are near 55 knots (63 mph/101 kmh) and it is moving in a westerly direction at 12 knots (14 mph/22 kmh).
The Joint Typhoon Warning center forecasters expect that the center of Nock-ten will make landfall over Hainan Island, China before July 29 at 1500 UTC (11 a.m. EDT) and weaken a little as it moves over land. However, once it re-emerges over water in the Gulf of Tonkin, it may strengthen a little before making final landfall in Vietnam.
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They have masses of 13 and 14 respectively and are referred to as "carbon-13" and "carbon-14." If two atoms have equal numbers of protons but differing numbers of neutrons, one is said to be an "isotope" of the other.
Carbon-13 and carbon-14 are thus isotopes of carbon-12.
Carbon has an atomic number of 6, an atomic weight of 12.011, and has three isotopes: carbon-12, carbon-13, and carbon-14.
(The numbers 12, 13 and 14 refer to the total number of protons plus neutrons in the atom's nucleus.
ICR creationists claim that this discredits C-14 dating. Answer: It does discredit the C-14 dating of freshwater mussels, but that's about all.
But carbon-14 is slightly radioactive: it will spontaneously decay into nitrogen-14 by emitting an anti-neutrino and an electron, with a half-life of 5730 years.Radiocarbon dating—also known as carbon-14 dating—is a technique used by archaeologists and historians to determine the age of organic material.It can theoretically be used to date anything that was alive any time during the last 60,000 years or so, including charcoal from ancient fires, wood used in construction or tools, cloth, bones, seeds, and leather. Along with hydrogen, nitrogen, oxygen, phosphorus, and sulfur, carbon is a building block of biochemical molecules ranging from fats, proteins, and carbohydrates to active substances such as hormones.All carbon atoms have a nucleus containing six protons.Radiocarbon dating (usually referred to simply as carbon-14 dating) is a radiometric dating method. | <urn:uuid:12f7d5f3-d671-4170-8dcb-50f7b6f5f951> | 3.984375 | 357 | Knowledge Article | Science & Tech. | 53.071121 | 95,646,868 |
July 1979. BYTE Magazine of that month had an article by Peter Grogono entitled "MOUSE: A Language for Microcomputers."
MOUSE is a stack based language like Forth but very terse (!) almost a byte code. It is lightweight; it can be implmented in under 200 lines of C. And can be quite powerful; in under 2000 lines of C.
When the mouse interpreter encounters a number, it pushes that number on the stack. In early versions of Mouse, the number must be an integer. In Mouse 2002, all variables are floating point, and the underscore operator _ changes the sign of the number on the top of the stack. This makes it easier to enter negative numbers. For example, -4 may be entered as 4_ instead of 0 4 -. If it is necessary to do integer division, this can be done using / &INT.
There are 26 predefined variables in mouse (A - Z). When the interpreter encounters a variable, it pushes its corresponding number (0-25) on the stack. Mouse-2002 includes global variables: Within a macro, lowercase variables a-z are local to the macro; uppercase variables A-Z are global. Within the main program, A-Z and a-z are the same.
You can replace the number of a variable on top of the stack with the variables value by using the period (.) operator.
To print the number on top of the stack use the bang (!) operator. This also has the effect of removing the number from the stack
To write a MOUSE program you must create a text file that contains a series of MOUSE commands. You can then run the program by using the command MI filename. Hello World in mouse is:
"HELLO, WORLD.!" $$
Later versions added comments to the MOUSE language. Anything on a line following a single quote (in Mouse 2002 the ~) is ignored as a comment. This makes MOUSE code much more readable and maintainable..
Operators are executed in order recieved, so Mouse is RPN, like Forth. To add 3 and 5 then print the result, you say:
3 5 + ! $
Two stacks are used in Mouse, a calculation stack and an environment stack. The environment stack supports local variables during macro calls. Macros are defined at the end of the program and contained between a $ and an @. For example:
$B 1% 2% + @
Defines a macro that adds two values. The 1% and 2% are replaced with the parameters passed to the macro. If we call the B macro (earlier in the file) with:
then 1% is replaced with 3 and 2% is replaced with the value of the variable B. Note that this is NOT the macro B, but the variable B. And it is not the variable, but it's value. As another example:
calls the Z macro, passing it the value of c, one of the 26 variables in the current environment.
$Z ~ ANSI clear screen (w/ specified foreground color) macro 27 !' "T" 7 48 + !' 1% 48 + !' @
The 1% references the parameter (in this case C) passed by the call to the macro.
Loops allow a program to execute a segment of code repeatedly until a specified ending condition is met. In most programming languages, this is done with a "for" loop, a "while" loop, a "repeat" loop, or some equivalent of these. In Mouse, loops are performed with the ( (parentheses) and ^ (caret) operators. A simple infinite loop has the form
( S )
where S is a statement or series of statements. The carat ( ^ ) operator is used to break out of a loop. If the boolean value on the top of the stack is false (0), the ^ operator will break out of the loop and continue execution following the right parenthesis. The carat operator may be used to construct a "while" loop. The Mouse statement
( B ^ S )
is equivalent to: while B do S , where B is a boolean value (0 or 1), and S is a series of statements. Similarly, a "repeat" loop may be constructed in the form
( S B ^ )
This is equivalent to: repeat S until (not B) .
Conditional statements are program statements that are executed only when a specified condition is true. In most programming languages, this is done with an "if" statement; in Mouse, the bracket operator ( [ ) is used. In Mouse, the expression
B [ S ]
is equivalent to: if B then S , where B is a boolean value (0 or 1), and S is a series of statements. When Mouse sees a [ operator, it executes the code between the [ and the matching ] only if the prior value is greater than zero. If it is less than or equal to zero, the code between [ and ] is skipped. The [ operator drops the stack in either case.
Mouse 2002 includes an "else" operator ( | ) for use with conditional statements. The syntax B [ S | T ] will execute statements S if boolean value B is true (1), or statements T if B is false (0).
Here are some commonly found statements in Mouse.
X: ~ store into variable X X. ~ recall variable X X. Y: ~ assign X to Y N. 1 + N: ~ increment N by 1 P. Q. P: Q: ~ swap values of P and Q ? A: ~ input a number and store in A P. ! ~ print variable P
Here is the standard program to calculate Prime numbers in mouse:
"PRIME NUMBERS!" "1 " N 3 = ( #P,N.; ' call P(N) N . 10001 - ^ ' if N >= __ break N N . 1 + = ' N++ ) "!" $P F 1 = ' F = 1 N 1 = ' N = 1 (flag 1=no divisor found) X %A = ' X = first argument ( ' F = F + 1 F F. 1 + = ' break loop when F > A/2 F. 2 X. / - 1 + ^ ' if A / F * F >= 0 F. X. / F. * X. - 1 - [ ' set N = 0 and break out of loop N 0 = 0 ^ ] ) ' if N > 0 then print X N . [ X. ! " " ] ' return @ ' end of program $$
Lunar Lander in Mouse:
"!" " ___ !" " /...\ !" " /.=.=.\ !" " |_____| !" " _/ | \_ !" " !" "Lunar Lander!" "!" F 1000 = 'Fuel A 100 = 'Altitude R 100 = 'Range I 0 = 'Horizontal Velocity J 0 = 'Vertical Velocity G 3 0 - = 'Gravity ( "!" "### Alt=" A.! " Range=" R.! " Fuel=" F.! " HV=" I.! " VV=" J.! " Grav=" G.! " ###!" F. 'if there is fuel left [ "Horizontal Thrust? " H ? = "Vertical Thrust? " V ? = ] F. 0 - 'if out of fuel [ "Out of fuel.!" 'then no thrust H 0 = V 0 = ] I I. H. + = 'Horizontal Accel J J. G. + V. + = 'Vertical Accel A A. J. + = 'Adjust Altitude R R. I. + = 'Adjust Range 'take abs val of h and v H. 0 - 'if h < 0 [ H H. 0 - = 'then h = - h ] V. 0 - 'if v < 0 [ V V. 0 - = 'then v = -v ] F H. V. F. - - = 'fuel = fuel - v - h A. 0 - 'if altitude < 0 [ "!!### You landed with!" "a horizontal velocity of " I.! "!" "a vertical velocity of " J.! "!" R.! " meters from the landing pad.!" 0 ^ ] ) $$
MOUSE Language Reference
|$$||end of program
In later versions, a single $ was used.
|"||print up to next "|
|!||print CR/LF inside "'s|
|?||read number from stdin and push|
|!||pop number from stack and print it
In some versions !' prints the value on the top of the stack as an ASCII character.
|n||push the integer n onto stack|
|A-Z||push address of variable on stack|
|.||replace address on stack with value|
|=||pop value, pop address, write value at address
In later versions this was changed to :
|+||pop a, pop b, push a + b|
|-||pop a, pop b, push a - b|
|*||pop a, pop b, push a * b|
|/||pop a, pop b, push a / b|
|[||pop c, if c<=0 then skip to ] on same level|
|)||loop back to previous ( at same level|
|^||pop c, if c!=0 then break out of ( ) loop|
|#M;||substitute M with any single letter to call macro M with no arguments|
|#M,args;||substitute M with any single letter and args with one to 26 comma-separated arguments to call a macro with one or more arguments.|
|@||terminates a macro definition (return)|
|%A||push the value of parameter A (substitute any single letter for A)
In some versions 1% pushes the first parameter (substitute any number for 1)
|$A||the beginning of macro A (substitute any single letter for A)|
Mouse Interpreter in 186 lines of C
Mouse "Debugger" (Single Step Interpreter) in C
Mouse "Compiler" in C (translates Mouse to C)
Mouse 2002 Interpreter in 1961 lines of C
Mouse : A Language for Microcomputers
by Peter Grogono
Published by Petrocelli Books
Publication date: February 1983
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Tropical Depression Peipah has been very stubborn and has moved over the southern and central Philippines bringing clouds, showers and gusty winds.
NASA-NOAA's Suomi NPP satellite captured an image that showed Peipah's clouds covering the Visayas and Mindanao regions of the country.
The VIIRS instrument aboard NASA-NOAA's Suomi NPP satellite captured a visible look at the remnant clouds associated with former Tropical Depression Peipah on April 14 at 4:24 UTC/12:24 a.m. EDT.
The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument collects visible and infrared imagery and global observations of land, atmosphere, cryosphere and oceans.
Peipah is a broad area of low pressure and its remnant clouds covered the central region of the Philippines called the Visayas region, and Mindanao, the southern region. Microwave satellite imagery confirmed that the low-level part of the storm is still poorly defined and convection (rising air that builds thunderstorms that make up a tropical cyclone) has not improved.
On April 14 at 0900 UTC/5 a.m. EDT, Peipah's remnants were centered near 9.7 north latitude and 130.8 east longitude, about 360 nautical miles/414 miles/666.7 km northwest of Zamboanga, Philippines. Maximum sustained winds were estimated as high as 20 knots/23.0 mph/37.2 kph.
According to the Joint Typhoon Warning Center, Peipah's remnants have a medium chance for regenerating in the next couple of days as it moves slowly in a westerly direction.
Rob Gutro | Eurek Alert!
New research calculates capacity of North American forests to sequester carbon
16.07.2018 | University of California - Santa Cruz
Scientists discover Earth's youngest banded iron formation in western China
12.07.2018 | University of Alberta
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
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This means that:
- If a number is 4 more than a multiple of 5, i.e. it is in the sequence
- 4, 9, 14, 19, 24, 29, . . .
- then the number of its partitions is a multiple of 5.
- If a number is 5 more than a multiple of 7, i.e. it is in the sequence
- 5, 12, 19, 26, 33, 40, . . .
- then the number of its partitions is a multiple of 7.
- If a number is 6 more than a multiple of 11, i.e. it is in the sequence
- 6, 17, 28, 39, 50, 61, . . .
- then the number of its partitions is a multiple of 11.
then stated that "It appears there are no equally simple properties for any moduli involving primes other than these".
After Ramanujan died in 1920, G. H. Hardy extracted proofs of all three congruences from an unpublished manuscript of Ramanujan on p(n) (Ramanujan, 1921). The proof in this manuscript employs Eisenstein series.
In 1944, Freeman Dyson defined the rank function and conjectured the existence of a crank function for partitions that would provide a combinatorial proof of Ramanujan's congruences modulo 11. Forty years later, George Andrews and Frank Garvan successfully found such a function, and proved the celebrated result that the crank simultaneously "explains" the three Ramanujan congruences modulo 5, 7 and 11.
Extending the results of A. Atkin, Ken Ono in 2000 proved that there are such Ramanujan congruences modulo every integer coprime to 6. For example, his results give
Later Ken Ono conjectured that the elusive crank also satisfies exactly the same types of general congruences. This was proved by his Ph.D. student Karl Mahlburg in his 2005 paper Partition Congruences and the Andrews–Garvan–Dyson Crank, linked below. This paper won the first Proceedings of the National Academy of Sciences Paper of the Year prize.
It is seen to have dimension 0 only in the cases where ℓ = 5, 7 or 11 and since the partition function can be written as a linear combination of these functions this can be considered a formalization and proof of Ramanujan's observation.
In 2001, R.L. Weaver gave an effective algorithm for finding congruences of the partition function, and tabulated 76,065 congruences. This was extended in 2012 by F. Johansson to 22,474,608,014 congruences, one large example being
- Tau-function, for which there are other so-called Ramanujan congruences
- Rank of a partition
- Crank of a partition
- Ramanujan, S. (1921). "Congruence properties of partitions". Mathematische Zeitschrift. 9: 147–153. doi:10.1007/bf01378341.
- "Cozzarelli Prize". National Academy of Sciences. June 2014. Retrieved 2014-08-06.
- Folsom, Amanda; Kent, Zachary A.; Ono, Ken (2012). "ℓ-Adic properties of the partition function". Advances in Mathematics. 229 (3): 1586. doi:10.1016/j.aim.2011.11.013.
- Bruinier, J. H.; Ono, K. "Algebraic Formulas for the Coefficients of Half-Integral Weight Harmonic Weak Maas Forms" (PDF). arXiv: . Bibcode:2011arXiv1104.1182H.
- Weaver, Rhiannon L. (2001). "New congruences for the partition function". The Ramanujan Journal. 5: 53. doi:10.1023/A:1011493128408.
- Johansson, Fredrik (2012). "Efficient implementation of the Hardy–Ramanujan–Rademacher formula". LMS Journal of Computation and Mathematics. 15: 341. doi:10.1112/S1461157012001088.
- Ono, Ken (2000). "Distribution of the partition function modulo m". Annals of Mathematics. Second Series. 151 (1): 293–307. arXiv: . doi:10.2307/121118. JSTOR 121118. Zbl 0984.11050.
- Ono, Ken (2004). The web of modularity: arithmetic of the coefficients of modular forms and q-series. CBMS Regional Conference Series in Mathematics. 102. Providence, RI: American Mathematical Society. ISBN 0-8218-3368-5. Zbl 1119.11026.
- Ramanujan, S. (1919). "Some properties of p(n), the number of partitions of n". Proceedings of the Cambridge Philosophical Society. 19: 207–210. JFM 47.0885.01. | <urn:uuid:c1e69f9f-55f9-471d-ab59-9dfa21fa875d> | 3.171875 | 1,074 | Knowledge Article | Science & Tech. | 76.373343 | 95,646,907 |
Populations of dolphins in the Eastern Pacific were expected to increase in abundance after successful regulations and agreements were enacted to reduce dolphin deaths as a result of fishing “bycatch,” cases in which animals are caught unintentionally along with intended targets.
But the new study, published in the October issue of Marine Ecology Progress Series, reveals that negative impacts from fishing activities remain. Instead of reducing numbers through direct mortalities, the study by Katie Cramer of Scripps Institution of Oceanography and Wayne Perryman and Tim Gerrodette of the National Oceanic and Atmospheric Administration’s (NOAA’s) Southwest Fisheries Science Center shows that fishing activities have disrupted the reproductive output of the northeastern pantropical spotted dolphin. The researchers note that reproductive output of the eastern spinner dolphin also declined, but a direct link to fishing effort was inconclusive.
“The results of this study clearly show that depleted dolphin populations have failed to recover in part due to a decline in reproductive output, and that fishing has had an effect on reproduction,” said Cramer, a graduate student researcher in the Scripps Center for Marine Biodiversity and Conservation. “This shows that the fisheries indeed are still having an impact.”
The new conclusions are based on broad surveys conducted by NOAA Fisheries Service between 1987 and 2003 designed to assess the size and health of dolphin populations in the eastern Pacific Ocean. The surveys included military reconnaissance camera images of more than 20,000 animals.
Cramer, who participated in helicopter surveys between 1998 and 2003, and her colleagues used the image database to analyze entire dolphin schools, focusing in particular on mother-calf pairs.
The scientists compared the data with the number of fishing events in which a dolphin school is chased by speedboats and encircled in a large “purse-seine” net in order to capture the large yellowfin tuna that often swim with dolphin schools. While such fishing led to high dolphin mortalities after purse-seine fishing was launched in the eastern tropical Pacific in the 1950s, bycatch deaths declined by the end of the 1990s due to new fishing techniques that ensured that dolphins are eventually released from the nets alive.
Yet despite mortality reductions, dolphin populations have not recovered at a rate expected since bycatch was reduced.
Using the aerial photographic database, Cramer and her colleagues found a strong link between the amount of fishing and reproductive output in a given year for the dolphin population most heavily targeted by the fishery, the northeastern pantropical spotted dolphin. Both the proportion of adult animals in the photographs with a calf, and the length at which calves disassociated from their mothers (a measure of the length at which the calves stop nursing), declined with increasing fishing effort.
Together, the results showed that fishing had a negative impact on calf survival rates and/or birth rates. This could be caused when fishing operations separate mothers from their suckling calves, interfere with the conception or gestation of calves or a combination of the two.
“The link between fishing activity and … reproductive output indicates that the fishery has population-level effects beyond reported direct kill,” the authors write in their report.
What remains unknown is the exact mechanism leading to reduced reproductive output. This question is currently being investigated by researchers at NOAA Fisheries’ Southwest Fisheries Science Center in La Jolla.
Note to broadcast and cable producers: UC San Diego provides an on-campus satellite uplink facility for live or pre-recorded television interviews. Please phone or e-mail the media contact listed above to arrange an interview.
Scripps Institution of Oceanography: scripps.ucsd.edu
Scripps Institution of Oceanography, at UC San Diego, is one of the oldest, largest and most important centers for global science research and education in the world. The National Research Council has ranked Scripps first in faculty quality among oceanography programs nationwide. Now in its second century of discovery, the scientific scope of the institution has grown to include biological, physical, chemical, geological, geophysical and atmospheric studies of the earth as a system. Hundreds of research programs covering a wide range of scientific areas are under way today in 65 countries. The institution has a staff of about 1,300, and annual expenditures of approximately $155 million from federal, state and private sources. Scripps operates one of the largest U.S. academic fleets with four oceanographic research ships and one research platform for worldwide exploration.
Upcycling of PET Bottles: New Ideas for Resource Cycles in Germany
25.06.2018 | Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF
Dry landscapes can increase disease transmission
20.06.2018 | Forschungsverbund Berlin e.V.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
19.07.2018 | Earth Sciences
19.07.2018 | Power and Electrical Engineering
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Higher Mathematics for Engineers and Physicists
by Ivan S. Sokolnikoff
Publisher: McGraw Hill 1941
Number of pages: 537
A book on mathematics beyond the calculus, written from the point of view of the student of applied science. The chief purpose of the book is to help to bridge the gap which separates many engineers from mathematics by giving them a bird's-eye view of those mathematical topics which are indispensable in the study of the physical sciences.
Home page url
Download or read it online for free here:
by Florentin Smarandache, at al. - arXiv
Throughout this book, the authors discuss some open problems in various branches of science, including mathematics, theoretical physics, astrophysics, geophysics, etc. Some parts of these problems may be found useful for scholarly stimulation.
by Joseph William Mellor - Longmans, Green
Long a standard textbook for graduate use in both Britain and America, this 1902 classic of modern mathematics remains a lucid, if advanced introduction to higher mathematics as used in advanced chemistry and physics courses.
by Leslie Copley - De Gruyter Open
A text on advanced mathematical methods with numerous applications. The book begins with a thorough introduction to complex analysis, which is then used to understand the properties of ordinary differential equations and their solutions.
by David Lippman - Lulu.com
A survey of math for liberal arts majors. Introduces contemporary mathematics topics: voting theory, weighted voting, fair division, graph theory, scheduling, growth models, finance math, statistics, and historical counting systems. | <urn:uuid:62b3e962-1153-4667-bfcc-3a6dda8ec4d0> | 2.703125 | 326 | Content Listing | Science & Tech. | 30.172077 | 95,646,950 |
Introductory Chemistry Online
by Paul R. Young
Publisher: Wikibooks 2011
Number of pages: 444
Introductory Chemistry Online is an open-source introductory chemistry textbook/workbook that is designed cover a college-level one-semester course. The text is designed to be simple, uncluttered and very much to the point.
Home page url
Download or read it online for free here:
by J.B. Dence, H.B. Gray, G.S. Hammond - W. A. Benjamin, Inc.
Chemical dynamics is the systematic study of reactions and reactivity. Its early introduction forms a solid foundation for later study. The book is intended for students who have had introductory stoichiometry, energetics, and structure.
by Gary Wiggins - Wikibooks
Main topics: How and Where to Start (Publications, Guides, Computer Searching, Current Awareness, Reviews); How and Where to Search: General; How and Where to Search: Specialized; Communicating in Chemistry; Miscellaneous; Supplemental Resources.
by Albert Martini - Project Gutenberg
The 2000 year history of the atom and chemistry, from the Classic Greek Era to the present, described in 800 pages. This history discusses the lives of about 180 chemists and physicists, representing the most important scientific accomplishments.
by J. Grotendorst, N. Attig, S. Bluegel, D. Marx - Julich Supercomputing Centre
Coarse graining of molecular systems and solids, quantum/classical hybrid methods, embedding and multiple time step techniques, creating reactive potentials, multiscale magnetism, adaptive resolution ideas or hydrodynamic interactions are discussed. | <urn:uuid:6471fcdb-ce79-4b13-a77c-e0684887d445> | 2.65625 | 351 | Content Listing | Science & Tech. | 34.548344 | 95,646,999 |
Prof. Dr. Sabine Zachgo, Director of the Botanical Garden of the Osnabrück University and Head of the Network commented: “This project will contribute to the requirements of the German National Biological Strategy and promote the implementation of the preservation of genetic diversity of wild species and the protection of regional adaptation”.
The Botanical Gardens in Germany will form a national network for the protection of endangered wild plant species. Foto: Osnabrueck University
The project is being supported by the Federal Agency for Nature Conservation (BfN) with funds provided through the German Ministry for the Environment, Conservation and Nuclear Safety (BMU) to the sum of 2.4 million Euros for a period of five years. In co-operation with various organisations, i.e. nature conservation groups as well as foundations, the aim is to ensure the protection of 15 endangered species for which Germany has taken a special responsibility. These species include mountain arnica (Arnica montana), dune gentian (Gentianella uliginosa) and a native orchid, the western marsh orchid (Dactylorhiza majalis).
During the first phase of the project seed material from the 15 species will be collected nationwide from their wild habitats and stored in gene banks. Subsequently, the Botanical Gardens will propagate this material for use in a final third phase, which involves a close collaboration with conservation organisations to use this material to strengthen endangered populations in their natural habitat.
This project was initiated by the Botanical Garden of the Osnabrück University which co-ordinates since 2009 the “Genbank für Wildpflanzen für Ernährung und Landwirtschaft” [Gene Bank for Wild Plants for Nutrition and Agriculture]. Within this network four of the five network partners already work successfully together.
“The special character and innovation of this network lies in the combination of different protection measures for native wild plants. Each of the partner contributes by bringing into the network their own special and complementary expertise thereby generating synergistic effects”, comments Zachgo. The Botanical Garden of Osnabrück will, for example, develop a Geo-Web-Mapping tool. This will allow involving also community service volunteers, who will be able to mark locations of plants deserving protection and notify the network of these online.
This project falls within the period of the International Decade for Biodiversity, 2011 – 2020, which was called into being by the UN to realise the biodiversity strategy objective. Through a strategy of widely broadcasting information and inclusion of the public the “WIPs-Project” aims to strengthen the awareness of the importance to maintain the native biodiversity and to increase the willingness of the broad public to take part in its protection.
In addition to the presentation of this project at, amongst others, the national horticultural show in Brandenburg in 2015 and at the IGA 2017 in Berlin, the Botanical gardens involved in this project will exhibit the selected species in their own establishments and inform the visitors of the special characteristics and specific requirements of these 15 endangered species.For more information:
Dr. Utz Lederbogen | idw
World’s Largest Study on Allergic Rhinitis Reveals new Risk Genes
17.07.2018 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt
Plant mothers talk to their embryos via the hormone auxin
17.07.2018 | Institute of Science and Technology Austria
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
Free-electron lasers (FELs) generate extremely short and intense X-ray flashes. Researchers can use these flashes to resolve structures with diameters on the...
13.07.2018 | Event News
12.07.2018 | Event News
03.07.2018 | Event News
17.07.2018 | Information Technology
17.07.2018 | Materials Sciences
17.07.2018 | Power and Electrical Engineering | <urn:uuid:99299d1d-d7a6-44ca-960b-89230a2fe7da> | 3.09375 | 1,324 | Content Listing | Science & Tech. | 33.599897 | 95,647,006 |
[13-DEC-13] We place a 1.27-mm thick (0.343 g/cm2) Al absorber in front of our continuous source. The absorber eliminates almost all x-rays below 14 keV. Our x-rays are generated with a 50-keV anode voltage, so their maximum possible energy is 50 keV. For these x-rays, energy deposition per unit mass density in silicon is 7.3 times greater than in air. Furthermore, x-rays in this range are almost certain to penetrate the window of our image sensor.
We place a TC255 and an ICX424 image sensor at range 55 cm from the source point. We place a 2.5 mm diameter tungsten ball over the window of the ICX424. We place the readout electronics behind a lead brick. At the plane of the image sensors, the Radcal Dosimeter, with its 60 cc ionizing chamber, measures 1.7 R/min, which is 6.6 Gy/hr in Si. We will apply power to the image sensors only when we acquire images, which takes a fraction of a second. At all other times, the sensor heads will be asleep, and no power will be applied to the sensors.
We start our experiment at 6:15 pm on 12-DEC-13. After 22 hours we have accumulated 140 Gy. The TC255 image sensor appears to be unaffected by the dose, but the ICX424 shows clear signs of damage.
The small, bright spots in the image are x-ray hits. Every image we take has a different collection of such spots. Outside the shadow of the tungsten ball, the accumulated radiation dose has turned the image gray. The following graph shows how the average and slope of intensity vary as we accumulate a dose of 450 Gy.
There are four measurements that deviate from the trend. In previous work, we determined that these measurements correspond to white images. These white images occur at random during irradiation, but not when we stop the irradiation. In this case, there are four white images out of four hundred taken during the irradiation.
During our experiment, we use single-pixel readout of the ICX424. After exposing the image area for 100 ms (0-140 Gy) or 50 ms (140-450 Gy), we transfer all the image pixels into the sensor's transfer array. This transfer takes place in one step. The pixels in the top row are read out first. They spend less than 1 ms in the transfer array. The pixels in the bottom row spend 200 ms in the transfer array. The slope of intensity tells us how fast the pixels are filling with charge while they are in the transfer array.
After 450 Gy we stop the irradiation and obtain the following image from the irradiated sensor with a DSL821 lens, a modified HBCAM Head (A3025), and quadruple-pixel readout. We decreased the gain of the A3025's amplifier so the saturation level of the quadruple pixel readout dropped to 191 counts from >255 counts. We take hundreds of images with the lens, and see no intermittent problems with data acquisition. Nor do we see any degradation in the sharpness of the images.
We connect a temperature sensor to the image sensor glass and cool down the sensor to −25°C. We allow it to warm up in the dark with a hot aluminum plate to take its temperature above ambient. We take 100 ms exposures in the dark and obtain the following plots of average and slope of intensity in the right side of the image with quadruple-pixel readout.
The average and slope of intensity increase exponentially with temperature. When we vary the exposure time for dark images, the average intensity increases linearly with exposure time. We conclude that ionizing radiation damages the ICX424 in such a way as to increase its dark current. After 450 Gy, we can still use the sensor to take images at 20°C with exposure times up to 100 ms.
[16-DEC-13] We place another ICX424 in our continuous x-ray beam, as in our previous experiment. Every hour we capture an image from the ICX424 with quadruple-pixel readout and an image from the TC255 with single-pixel readout. This is the same TC255 that received 450 Gy in our previous experiment. Both sensors are receiving 6.6 Gy/hr.
[18-DEC-13] Our ICX424 has received 300 Gy. We take the following image with quadruple-pixel readout. We intensify with our "strong intensification" to show the radiation hits and the slope of intensity.
The graph below shows how slope and average of intensity for the ICX424Q images increases with dose so far. We take one measurement per hour.
[19-DEC-13] We stop the ICX424 irradiation at 5:00 pm today at a total dose of 475 Gy. We enter the x-ray room and turn on the continuous source again, and obtain 1.6 R/min, which is slightly less than the 1.7 R/min we have assumed in our plots. We will leave our plots as they are. We allow the sensor to take video images through a lens. We obtain this image at 20°C with 10-ms exposure time.
[18-MAR-14] We place our TC255 Dosimeter at position 70 cm on our x-ray table, which is 55 cm from the continuous x-ray source. At the same location we place three C460EZ500 LEDs mounted to LED Heads (A2079B) and connected to a Fourteen-Way Switch (A2078A) with six-way flex cables. With these circuits, we can flash the LEDs from the LWDAQ. We set up a Camera Head (A2056) to view the LEDs as they flash. Each LED appears as a spot of light in the camera image. With the BCAM Instrument, we obtain the total intensity of each spot. This total intensity will be a measure of the power emitted by the LED during our irradiation. Our Acquisifier script is RTT_2. We cover the TC255 image sensor window with two coats of black nail polish so that dim light in the x-ray room won't disturb the detection of x-rays. We place our Radcal Dosimeter at the same position, 55 cm from the continuous source. We take data for a few minutes to confirm the stability of our intensity and dosimeter measurements with no light and no x-rays. We ramp up the continuous x-ray source and obtain a steady 1.64 R/min = 6.3 Gy/hr in Si.
One hour into the experiment, we had to go in and adjust the fan, which upset the brightness measurements, because we moved the LEDs slightly and the camera too. When we get to 450 Gy and we still see no drop in LED intensity, we check the x-ray dose rate with the TC255 dosimeter as follows. We turn off the x-ray source. We take an image with the TC255. Its average intensity is 59. We turn on the x-ray source. We take another 50-ms exposure and apply a threshold of 62 to determine the charge density of the hundreds of bright x-ray hits. The charge density is 0.665 counts/pixel. We refer to this graph of charge density versus dose in Roentgen, which has slope 523 counts/px/R. The TC255 image indicates a dose rate of 1.5 R/min, which is consistent with the Radcal's 1.64 R/min. Our x-ray source is still running.
[25-MAR-14] Our three blue EZ500 LEDs have received 1000 Gy. We see no change in their brightness when supplied with current through an 86-Ω resistor from 15 V. We stich on each LED in turn and measure it forward current with the LWDAQ power supply monitors. They draw 142 mA, 142 mA, and 143 mA. We remove the LEDs from our test stand and install an un-exposed LED. It draws 143 mA. During our 1000 Gy radiation of a bare die LED, we see no change in its optical power output or forward voltage drop.
We restore our three blue LEDs, although not necessarily in the same locations. We move the Fourteen-Way Injector (A2078A) circuit to the same 70-cm location on our tape measure, perpendicular to the x-ray beam, so that all its circuits, and the TC255 dosimeter, and the LEDs receive 1.64 R/min = 6.3 Gy/hr. We use Acquisifier script RTT_3 to measure the charge density due to x-rays in the TC255 image sensor and the quiescent current of the LWDAQ circuits drawn from the +5 V power supply. The A2078 uses an LC4064ZC and an SN65LVDS180D transceiver, both of which may suffer from increased quiescent current as a result of ionizing radiation damage. The LC4064ZC is an EEPROM-based non-volatile programmable logic chip. We make sure our new script sorts the three LED images in order of increasing x rather than brightness. We turn on the x-ray source and start running. The charge density in our TC255 dosimeter is 0.67 counts/px, which implies a dose rate of around 1.5 R/min, but we will stick with the Radcal's measurement of 1.64 R/min. We will trust the TC255 dosimeter to monitor changes in dose rate, but not the absolute dose rate.
We run for a couple of hours, accumulating roughly 12 Gy in Si. The x-ray head is at 47.5°C. We stop the experiment, entere the x-ray room and re-arrange the apparatus so the fan is blowing more effectively on the x-ray head. The photograph below shows our setup. We re-start the experiment. We keep in mind that our LEDs have already endured 1000 Gy and our A2078A has endured 12 Gy.
The fan blows into the opening in our lead brick x-ray source enclosure. We like to keep the temperature of the x-ray head below 40°C. If the temperature exceeds 50°C our data acquisition script will shut down the x-ray source.
When we turn on the x-ray source, the +5V quiescent current increases by 7.7 mA. This current is drawn by the connection between the LWDAQ and the x-ray controller, and is not the result of any increase in current caused by the absorption of x-rays in the electronics. The excess current plotted above is with respect to the first moments the x-ray source is turned on.
[04-APR-14] Yesterday, our 25-MAR-14 irradiation was stopped by a power cut. Today we enter the x-ray room and place our Radcal dosimeter on the table just in front of our A2078A circuit board. The disk of our Radcal Dosimeter's 60-cc ionizing chamber covers the A2078A logic chip. We turn on the x-ray source. The dose rate is 1.70 R/min, or 6.5 Gy/hr in Si.
We start a new irradiation. We leave the TC255, A2078A, and three EZ500s in place. We add a Laboratory Camera (A2075B) with a fresh ICX424 mounted on the board with no lens. We cover the ICX424 window with two coats of black nail polish. Apparatus shown below.
We use the RTT_4 Acquisifier script to obtain the charge density and average intensity of the TC255 and the ICX424, the brightness of the LEDs, and the total inactive state current consumption of the LWDAQ devices. In the graph below we show the average intensity of the ICX424 image with a 50-ms exposure and single-pixel readout, and the excess +5V quiescent current.
The excess quiescent current starts at 3.1 mA following our earlier irradiation of the A2078A. Now our excess quiescent current arises from damage to the A2078A and the A2075B. The A2078A flashes the LEDS all the way through the experiment, and the EZ500 average intensity remains constant to ±5%. The A2075B reads out the ICX424 all the way through the experiment. The two spikes in average intensity also occurred in earlier experiments, when the A2075B was shielded behind lead.
Meanwhile, the ICX424 shows the same rate of dark current increase as in our previous irradiations. We decrease the gain of the A2075 output amplifier by changing R31 and R32 to 330 Ω. We obtain the following image with continuous 3 frame/s quadruple-pixel readout. The ICX424 draws 7 mA from 15 V during exposure and readout, which take roughly 50 ms. The average power dissipation at 3 frames per second is 16 mW. The thermal resistance of a typical DIP package is of order 100 °C/W, so we expect our ICX424 silicon to heat up by roughly 2°C. A °C rise will increase the dark current by no more than 20%. We obtain the following image with a 1-ms exposure at 3 frames/s in our laboratory at 19°C ambient temperature.
This is the third ICX424 we have irradiated with our continuous x-ray source. All show the same increase in dark current with dose.
[22-APR-14] Starting on 15-APR-14, we run our first experiment with Brandeis University's gamma-ray Irradiation Chamber. The cesium source produces 660 keV gammas rays as well as beta particles. But the beta particles are immediately absorbed by the source's shielding, so that only the 660-keV gamma rays reach our electronics. Our objective is to determine whether our measurement of the dose delivered by x-rays to silicon is correct. With 660-keV gammas, we do not have to correct for the absorption coefficient of silicon, on account of the absorption coefficients of air and silicon being the same 0.030 g/cm2 at 660 keV. When we irradiate with x-rays, we multiply the dose in air by 7.3 to obtain the dose in silicon, to account for the higher absorption coefficient of silicon compared to air.
We install the irradiation chamber's ×10 absorbers. We intend to install our electronics within the chamber at Position 3, which we measure to be 18 cm from the source. According to the Brandeis University documentation from 1986, and accounting for the half-life of Cs-137, the dose rate at Postion 3 should be 8.2 R/min, or 4.3 Gy/hr. When we place our battery-powered Radcal Dosimeter into the chamber, with the ionizing chamber at Position 3, we measure 5.7 R/min or 3.0 Gy/hr in air or silicon at Position 3. In our analysis, we will use the dose we measured with our Radcal Dosimeter because this is the same dosimeter, calibrated in September 2013, with which we calibrated our x-ray doses.
We mount two ICX424 Minimal Heads (A2076E) to the front side of a piece of cardboard and connected by 50-mm flex cables to a Blue HBCAM Head (A3025B) on the back side. Each A2076E provides one ICX424 image sensor. We paint the sensor windows with three coats of black nail polish to block ambient light. We fasten the cardboard to an aluminum block and place it inside the irradiation chamber so that the sensors are at the range of Position 3 and centered upon the height of the chamber. The A3025B is 1.5 cm farther from the radiation source. We close the chamber and raise the source into position. We set up our data acquisition system outside the chamber.
With the door closed and the source raised, we obtain the following image of gamma rays with one of the image sensors. The exposure time is 50-ms.
We take one image from each sensor each hour, record charge density and average intensity, and save both images to disk. We calculate the dose rate at We obtain the following graph of charge density and average intensity in the two image sensors versus measured ionizing dose.
The average intensity increases linearly from 0-400 Gy. The slope is 0.42 cnt/Gy for No1 and 0.50 cnt/Gy for No2 (average 0.46 cnt/Gy). We compare this to 0.54, 0.44, and 0.59 cnt/Gy for x-ray irradiations A, B, and C of the ICX424 respectively (average 0.52 cnt/Gy).
After seven days in the irradiation chamber, we have delivered 500 Gy to the image sensors and readout electronics. We remove the electronics and take them back to our laboratory. We connect undamaged image sensors to the A3025B. Whether we select CCD1 or CCD2, we obtain distorted images from CCD2. The DG419DY analog switch, U11, is not functioning. We replace U11 and the circuit functions perfectly. Quiescent current from +5 V is 3.8 mA. We clean the nail polish off the ICX424s and read them out with the repaired A3025B and obtain from each an image image like the one shown below, for 1 ms exposure time and 20°C ambient temperature.
We see a jump up in the average intensity of No1 at about 315 Gy in the graph above. We suspect that this coincides with the failure of the analog switch. We were no longer observing the average intensity of No1, but some combination of No1 and No2. We note that the A2075B circuit we irradiated with 475 Gy, and which still takes good images, is a single-sensor circuit and does not have an analog switch.
[17-SEP-14] On 05-AUG-14, we took 4 of HBCAM, 8 of Luxeon Z Royal Blue, and 4 of C460EZ500 to UMass Lowell for irradiation with fast neutrons. We present our result in Neutron Irradiation of nSW Components. The ICX424 image sensors in the HBCAMs experienced an increase in dark current, just as we observed when we irradiated the TC255P image sensor with fast neutrons. The remaining components showed no sign of damage.
The fast neutrons are generated at Lowell in the following way. A 4-MeV proton beam strikes a lithium-7 target, generating neutrons as described in Kegel et al.. A small fraction of protons combines with lithium-7 to produce a short-lived beryllium-8, which then decays into a neutron plus a beryllium-7 ion. After the experiment, UMass Lowell measured the activity of the target, from which they deduced that a total of 2.75×1014 neutrons were produced. We want to take this total activity and calculate the dose our image sensors, LEDs, lasers, and electronics received at various ranges from the targe.
The reaction results in the creation of 0.00177 amu of mass, or 1.64 MeV. Our calculation of the minimum proton energy to initiate the reaction, and the maximum forward neutron energy, are below.
The incoming protons lose energy as the pass through the lithium target. Thus the energy of the proton upon colliding with the lithium varies from 0-4 MeV in our experiment. The minimum proton energy required to produce a neutron is 1.88 MeV. The maximum possible neutron energy is 2.33 MeV. We obtain the angular distribution of neutrons emitted by the target using a Monte-Carlo simulation, Neutron_MC.tcl. The output is shown below, as counts versus angle before and after momentum correction and five hundred thousand iterations.
With the momentum correction, the flux in the 0° direction is 1.7 times higher than in the 90° direction, while the flux in the 90° direction is almost exactly the same as it is without momentum correction. In between these two directions, the flux varies linearly. The maximum neutron energy is 2.33 MeV. We could simulate the spectrum of the neutrons versus direction, but we are confident that the average neutron energy will be close to half of 2.33 MeV, or 1.16 MeV. Our calculation agrees well with the flux contours, thresholds, and neutron energies given in Kegel et al..
Our experiment produced a total of 2.75×1014 neutrons. If we assume average energy 1.16 MeV and use a straight line approximation to the green line in the graph above, we arrive at the following formula for dose in Tn, where 1 Tn = 1012 1-MeV eq. n/cm2.
Dose = (43.1 - 0.197θ) / r2,
Where θ is angle to the proton beam and r is range from the target in centimeters. Applying this formula, we get 1.9 Tn at angle 40° and range 4.3 cm, which is where our closest image sensor was located.
[15-OCT-14] The circuits we irradiated at Lowell have had eight weeks to anneal at room temperature. We measure ICX424 image sensor dark current at room temperature and the we measure the effect of temperature upon sensor dark current. We obtain lower bounds for the radiation tolerance of the LEDs, HBCAMs, and ICX424 in Neutron Irradiation of nSW Components. We expect the ICX424 to be able to tolerate up to 23 Tn at 20°C when we use the LWDAQ's quadruple-pixel readout, which is faster and allows less time for dark current to accumulate in the image transfer area. The remaining HBCAM electronics showed no sign of damage after 2 Tn, and the LEDs showed no drop in brightness after 1.0 Tn.
[20-NOV-14] We have a 2.5-m length of optical fiber (Fiber No1) marked "Draka Comtek Optical Cable Sep 2006 2F 62N3 C(ETL)US QFNR 100518184", which we purchased from CableLan under part number "S705T-02F-62N3 Zip cord, LSZH, 62.5/125 with rad hard fiber", with FC connectors on either end. We place Fiber No1 at range 26 cm from our continuous x-ray source (position 45 cm on our ruler), where our calibration tells us to expect a dose rate of 5.0 R/min of 14-50 keV x-rays. Assuming glass absorbs these photons like silicon, the dose rate will be 19 Gy/hr, so the total dose is around 3000 Gy. The jacket color is less bright and one ferrule is going brown on one side.
Before irradiation, we held a photodiode in front of the output D-type connector of one of our blue light injectors. We measured 92 μW. We plugged the cable in and measured 103 μW at the other end (note that the first measurement does not collect all the light available in the D-type connector). After 3000 Gy we connect the fiber to a D-type connector at which we measure 94 μW. At the far end we observe less than 1 μW, and what we see coming out is green, not blue.
We compare transmission through a 2.5-m un-irradiated length of the same fiber. We measure the light emerging from the far end of each fiber when plugged into the same 460-nm blue contact injector. The irradiated fiber gives us 0.0 μW and the un-irradiated gives us 90.6 μW. We switch to a 650-nm red focusing injector. The irradiated fiber gives us 1.4 mW and the un-irradiated fiber gives us 7.1 mW. If we assume the transmission of the un-irradiated fiber is 100%, then that of the irradiated fiber is 0% at 460 nm and 20% at 650 nm.
[21-NOV-14] We receive an informative e-mail from the manufacturer of the optical fiber. The graph below shows the darkening with ionizing dose as a function of wavelength.
We measure once again the transmission at 650 nm and 460 nm and find it to be unchanged from yesterday. We place our irradiated sample in an oven at 60°C at 10:00.
At 13:00 we place a 2.5-m fiber (Fiber No2) at range 26 cm (45 cm on our ruler) from our continuous source, where it will receive 19 Gy/hr. We use 50 cm of the fiber to reach a 460-nm blue contact injector behind a lead shield, and we hold the other end of the fiber so that we can view it with a camera behind the shield. We measure the intensity of the image we obtain from the fiber tip with a fixed 670-μs flash time. We record the image brightness every ten minutes.
[24-NOV-14] When we stop the irradiation of No2, it has received 1500 Gy. We measure 57% transmission at 650 nm and 4% at 460 nm. We place it in the oven at 40°C. We take our first irradiated fiber, No1, which received 3000 Gy and has been at 60°C for 72 hours, and measure 38% transmission at 650 nm (up from 25%) and 1% at 460 nm (up from 0%).
We have this S705T fiber installed in the ATLAS detector EES and BEE alignment systems, where they carry 650-nm and 460-nm light respectively. The maximum ionizing dose we expect in either system after ten years at luminosity 5×1034 1/cm2s and beam energy 14 TeV is 25 Gy. We can tolerate loss of optical power provided the exposure time remains <10 ms. The longest exposure time in EES is 100 μs (650 nm, 1 mW, ≤3 m) and in BEE is 1 ms (460 nm, 100 μW, ≤3 m). Thus we can tolerate 1% transmission of 650 nm in EES and 10% transmission of 460 nm in BEE. Our radiation tolerance is at least 3000 Gy in EES. Ignoring any benefit from room-temperature annealing, our tolerance in BEE is 200 Gy.
[01-DEC-14] After six days at 40°C we measure transmission in No2 and observe 7.3% at 460 nm and 72% at 650 nm. In No1, which has spent six days at 20°C we measure 1% at 460 nm and 35% at 650 nm.
[03-DEC-14] We place a 1-m length of CeramOptec WF100/110P37 at range 45 cm in front of our continuous x-ray source. This fiber has a 100-μm silica core, 110-μm silica cladding, and a 125-μm polyimide jacket. We supply red light with a Five-Way Focusing Injector (A3073A). We deliver the light through a separate S705T jumper cable that remains outside the radiation area, and extract the light with another S705T jumper cable. We shine the red light upon a diffuser, and take images from the other side of the dappled light pattern. By this means, we obtain a ±5% stable measurement of light intensity despite the fluctuations in the light pattern as the fibers vibrate in the presence of the cooling fan. We turn on the x-ray source at 11:30 am. The fiber receives 19 Gy/hr. We record light intensity every hour.
[17-DEC-14] We obtain the plot above. We stop the x-ray source, remove fiber No3 and put in its place our Radcal dosimeter. We turn on the source and measure 5.0 R/min, which is exactly what our calibration tells us for range 26 cm (ruler position 45 cm). We multiply by 3.84 to get 19.2 Gy/hr. We inject 1.6 mW of 650-nm light into No3. We get 1.0 mW out the other end, for 61% transmission.
We look at the devices returned from a second fast neutron irradiation at UMass Lowell, this time in their nuclear reactor, where the dose is more uniform and we can irradiate many parts at the same dose. We report in detail here. The radiation facility tells us our components received 2.2 Tn. Damage done to image sensors is within 20% of what we expect from our previous experiment.
[05-FEB-15] We deliver another set of image sensors, LEDs of various colors, and optical fibers to UMass Lowell for irradiation with fast neutrons in their reactor. We receive the parts back several weeks later. We report in detail here. According to UMass Lowell, the dose delivered was 14 Tn. The ICX424AL image area dark current four weeks after the experiment is 4.0 counts/ms/pixel, and transfer area dark current is 2.0 counts/ms/pixel, where the pixel dynamic range is roughly 200 counts. We reduce the amplifier gain by ×0.4 and find that we can obtain adequate full-resolution, single-pixel images. If dark current continues to increase in proportion to neutron dose, we estimate that our faster quadruple-pixel readout should permit image acquisition at up to 22 Tn with a 10-ms exposure and 40 Tn with a 2.5-ms exposure. The deep red Luxeon Z LED power output dropped by 75% for 14 Tn. The red dropped 80%. Despite this drop, we still expect the required flash time of the red fiber sources to be less than 2.5 ms in nSW locations that will receive the most radiation. Assuming damage continued at the same geometric rate, the deep red LEDs will still be effective after 33 Tn.
[06-MAR-15] We install our first Bar Head (A2082A) in our gamma ray irradiation chamber. We connect one image sensor to the board and place the board at Position 3, roughly 18 cm from the source, where the chamber's calibration says it will receive 4.3 Gy/hr with a ×10 absorber, but our own ionizing chamber measurement suggets it will receive 3.0 Gy/hr with a ×10 absorber. In this experiment, we have the ×5 absorber installed, so we expect 6.0 Gy/hr. The image sensor is roughly 19 cm from the source, where we expect it to receive 5.4 Gy/hr. We take one image from the sensor and one image from a non-existent sensor every half-hour. We want to see if the SW06 analog switch can continue operating during the ionizing dose.
[25-MAR-15] The same Bar Head received another seven days irradiation in the same location within our gamma ray irradiation chamber. The board has now received a total of 1.4 kGy, according to our own calibration. The ICX424AL has received 1.3 kGy. It no longer functions, giving us a gray image always. The A2082A has quiescent current 0.5 mA from +15V, 13 mA from +5 V, and 0.0 mA from −15 V. An un-damaged board has the same current consumption from ±15 V, and 3 mA from + 5V. We take this image with a fresh ICX424. We switch between A2082A sockets 1 and 2 and confirm that the analog switch is still working.
[09-APR-15] We describe in the Bar Head (A2082) Manual the effect of dropping low-level of the ICX424 vertical clock voltages from −7.7 V to −10.3 V. In two ICX424 image sensors that endured 500 Gy in our Cs-137 chamber last April, the lower clock levels dropped the dark current by a factor of 2.5. We are now able to take full-resolution, high-contrast images like this of ambient light with these irradiated sensors. With these new clock levels, we study the saturation level of pixels in a irradiated sensors, and find that the quadruple-pixel readout does not raise the effective pixel capacity for neutron-irradiated sensors.
[10-APR-15] We connect a new 50-kV power supply to our No2 continuous x-ray head. We run up the power and measure 5.5 R/min at position 44 cm. With the No1 head, we obtained 5.0 R/min at position 45 cm in DEC-14.
[23-APR-15] We connect four ICX424 image sensors to a Bar Head (A2082A), as well as two white LEDs and two RTDs. We use this Acquisifier script to acquire 50-ms dosimeter exposures from the four image sensors, temperature readings from the top and bottom reference resistors and the two RTDs, and to flash the LEDs so that their light is visible on two separate image sensors.
[30-APR-15] At 900 Gy we enter the cesium-137 room and capture single-pixel images with 0-ms exposure time and see gamma hits all the way from top to bottom. From 300 Gy to 400 Gy the RTD measurement goes wrong and stays wrong. We have not turned off power to the logic on the board, but the ±15 V power is turned off every time we send the board to sleep.
[04-MAY-15] We remove our A2082A with image sensors, LEDs, and RTDs from our cesium-137 chamber at 2:30 pm. They have been irradiated for 267 hours. The A2082A received 1.6 kGy. The IXC424, RTDs, and blue LEDs have received 1.4 kGy. The A3028A captures images from four image sensors. It flashes all LEDs. The thermometer readout is broken. When we select T1 with no RTD attached, K+ is at 380 mV. We observe failure of the temperature measurements at 330 Gy in our experiment. We remove R18 and R21 and K+ goes to 14.4 V. One of the NDS355AN mosfets Q9 or Q10 is stuck on even with 0-V gate bias. This is a symptom of charge build-up in the gate oxide during irradiation, and is inconsistent with our previous 1.4-kGy irradiation. It turns out that our latest firmware, not used in the previous irradiation, applies 3.5 V logic power to the gate of TB's transistor, Q9, even when the board is asleep, which increases the charge build-up on the gate during irradiation.
[06-MAY-15] We replace Q9 on No2 with an NDS355AN from No1 that endured 1.4 kGy with no bias on its gate. We get noisy temperature measurements. We realize that Q15 also has bias when the board is asleep, thanks to another error in the firmware. We replace Q15 with another mosfet from No1. Now we get accurate and precise temperature measurement.
We take the image from our ICX424 No3 that has received 1.4 kGy, at roughly 20°C. The bottom of the image is just saturating, and is therefore not useful for finding light spots. But the majority of the image shows adequate contrast for spot-finding.
We are able to obtain similar images from ICX424s No1, No2, and No4, which received the same dose. At 22°C, the lower 20% of the image is saturating, and at 20°C with 10-ms exposure we also see 20% loss of the image. But the light is bright in our laboratory, which contributes to the saturation. The ionizing radiation tolerance of our ICX424 with the new clock levels appears to be 1.4 kGy.
[22-JUN-15] We have two A2082A Bar Heads, No5 and No6, back from a 20-Tn fast neutron irradiation. Neither works. In No6, we decrease R1=10kΩ to R1=2.2kΩ so as to supply more base current to Q1, an NPN transistor ZXTN2031F that supplies the 1V8 current. We also note that the LM4050 voltage references are damaged. The 2V5 part now produces 2.8 V, the 4V1 part produces 4.7 V. These regulators are ionizing-radiation tolerant to 3 kGray, according to the manufacturer, but they are still vulnerable to neutrons. Nevertheless, the A2082A No6 is fully-functional after replacing R1 with 2.2 kΩ.
[30-JUN-15] The figure below shows how the threshold voltage of four NDS355AN N-channel mosfets drops with ionizing dose in our Cs-137 chamber. We obtained the plot with four copies of this circuit.
So long as the threshold remains above 0.1V, which is the maximum LO output voltage for our logic chip, our thermometer circuit will work. The minimum un-irradiated threshold voltage of the NDS355AN is 1.0 V, so we can tolerate a drop of 0.9 V, which occurs after 1 kGy. We use the NDS355AN in the thermometer readout of our Bar Head (A2082A). This readout can tolerate 1 kGy without any pre-construction measurements of the threshold voltage. But if we measure the threshold voltage of a random sampling of mosfets, and find them to be 1.6±0.5 V, as we have in the past, our tolerance is at least 2 kGy.
[15-JUL-15] We measure the current gain of ZXTN2031F and ZXTP2025F bipolar transistors at 500-mA collector current after 20 Tn followed by 30 days room-temperature anneal. We bake them at 150°C for 24 hours and measure again. We compare to un-irradiated transistors also. We obtain the results below.
Both transistors have gain greater than 100 after 20 Tn. Their gain recovers significantly during an anneal, which is characteristic of neutron damage.
[30-JUL-15] We build four copies of this circuit to measure the effect of ionizing radiation upon NDS356AP P-channel mosfets. We place the circuits in our Cs-137 chamber, where they receive 6 Gy/hr.
[30-NOV-15] We obtain the following graph of relative transmission through eight optical fibers irradiated by our continuous x-ray source. The four colored plots are for individual fibers. The black plot is the average of four fibers.
All but one of these fibers we received as samples from Brian Rische of Prismian Group, after communicating with CableLan about the darkening of the S705T-02F-62N3 fiber in blue light. As we received them, the fibers were identified as follows. A: "10" 62.5um RH Ge PCVD. B: "11" 50um SRH F PCVD .43 dB/km. C: "5" 50um RH Ge PCVD .44dB/km. D: S705T-02F-62N3. E: Average of four 80-um connectorized fibers.
[05-FEB-16] We irradiate samples of the ZVN3306F mosfet in an SOT-23 package. We mount the package on a SIP adaptor and plug the adaptor into a prototyping board. We apply bias voltages to the gates from −15 V to +15 V. We connect the sources and drains to 0 V. We place the mosfets in front of our continuous x-ray source. Every few days we take them out and measure their threshold voltages. And so we obtain the following plots of threshold voltage versus dose.
The effect of negative bias voltages appears to be similar in magnitude to those of positive bias voltages, so that it is the magnitude of the electric field in the gate oxide that affects the damage, not the direction.
When we put together the final threshold voltages at the end of our irradiation, we obtain the following relationship between threshold voltage and gate bias.
The ZVN3306F is a candidate for use in the radiation-tolerant, low-power analog switches we must include in our Fourteen-Way LWDAQ Multiplexer (A2085)
[07-MAR-16] We subject NDS355AN, UM6K31N, and UM6K34N mosfets to 1.3 kGy in Si with our continuous x-ray source. During the irradiation, each mosfet has its drain and source connected to 0 V and a bias voltage applied to its gate. Every few days we remove the mosfets from the experiment to measure and record their threshold voltages. The figure below shows the drop in threshold voltage for various mosfets and bias voltages. All mosfets took part in an earlier experiment, in which they received roughly 700 Gy. We present these results because they are relevant to our acceptance of our LWDAQ Multiplexer (A2085), which uses the UM6 mosfets for its analog switches.
The NDS355AN is a mosfet we have tested before. The 0.5-V drop in the NDS355AN at 0-V bias is consistent with the change that takes place from 0.7 kGy to 2.0 kGy in our JUN-15 results. The UM6K31N is a 2.5-V mosfet, while the UM6K34N is a 0.9-V mosfet. We see no change in the 0.9-V mosfet's threshold voltage. We plan to repeat this experiment so as to observe the magnitude of the effect in the 0.9-V mosfet.
[01-APR-16] We repeat irradiation of the UM6K34N, measuring its threshold voltage by taking it out of our continuous x-ray room every day or two.
Even with ±5-V gate bias the drop is only 15%, compared to 40% or so for the NDS355AN. During the same experiment, we irradiate a Fourteen-Way Multiplexer (A2085A) to 1.4 kGy, checking it every few hundred Gray to see if it's still working. At 1.4 kGy it captures images on all sockets with no visible degradation of performance. This multiplexer uses the UM6K31N.
[27-APR-16] We receive from UMass Lowell a Fourteen-Way Multiplexer (A2085) and Bar Head (A2082) that received 15 Tn of fast neutrons. We capture images through all multiplexer channels, and from the bar head. We measure power supply voltages on the board. They function normally.
[06-MAY-16] We remove four Black N-BCAM Heads (A2083A) and four Blue N-BCAM Heads (A2083B) from our continuous x-ray source, where they have received 702 Gy at 2 Gy/hr. All boards loop back, take sharp images, and turned on their lasers. Current consumption and laser power remain within the nominal ranges prior to irradiation.
[12-MAY-16] We irradiate a selection of shunt regulators with x-rays. During the experiment, they are biased with a current of a few milliamps. We remove them occasionally and measure their voltage drop.
The LM4050 regulators are the ones we use in our newer LWDAQ devices and multiplexers.
[13-MAY-16] We select 4 Black N-BCAM Heads (A2083A) and 4 Blue N-BCAM Heads (A2083B) at random from our recent batches of 440 of each board. We equip them with image sensors and N-BCAM Side Heads (A2074C/D). We arrange them in front of our x-ray source. Because these boards have components on both sides, we must account for absorption of x-rays in the printed circuit board. The image below we took from an ICX424AL after 700 Gy, where the PCB was between the source and the image sensor during irradiation. We see higher dark current in the regions where there was less shielding.
We place a four-layer, 62-mil thick, FR4 printed circuit board, with one ground plane and three signal layers, between our source and a TC255P dosimeter. The dose drops by a factor of four. We arrange two of each type of board with the top side facing the source, and two with the bottom side. We irradiate for one week, accumulating a total dose of 700 Gy in Si for the components on the sides facing the source, and 175 Gy for those facing away. We see no significant change in current consumption when awake or asleep from ±15 V and +5 V. We obtain sharp images from all image sensors. Dark current is consistent with earlier measurements. We see no significant change in laser power.
[16-JUN-16] We measure ionizing radiation tolerance of our original ATLAS camera circuits. The Inplane Sensor Head (A2036) and Proximity Camera Head (A2033A) are vulnerable to ionizing radiation because their DG411DY analog switches are always powered with ±15 V. Their circuits are identical, but their layouts are different. We take four of the A2036 and two of the A2033A and arrange them with half facing towards and away from our x-ray source. We deliver what we believe is 400 Gy in Si to the components facing the source and 100 Gy in Si to those facing away. Later, we find that our x-ray source is operating at 40% of full power, so the actual doses could be as low as 40 Gy and 160 Gy. The boards with the DG411DY facing away are fully functional, but those with the DG411DY facing the source are damaged. The DG411DY can survive at least 40 Gy with ±15 V power applied, but perhaps not 160 Gy. When we replace the three damaged DG411DYs, the boards function perfectly. There is no significant increase in their current consumption. The Inplane Sensor Head (A2047T) and Proximity Camera Head (A2047A) do not use an analog switch. We test two of these, one facing each way, to what we think is 400 Gy, but could be only 160 Gy. They are fully-functional afterwards, with no significant change in current consumption.
[29-JUN-16] We irradiate three N-BCAM BK7 glass lenses with x-rays until they have received 2100 Gy. We see no change in color from start to finish.
[09-SEP-16] We irradiate with x-rays five o-rings we plan to use to secure fiber-optic ferrules in place in the nSW.
In calculating the dose we deliver, we use the absorption spectrum for rubber rather than silicon, and combine the absorption spectrum with our x-ray spectrum. We note, however, that this spectrum we measured for our pulsed source, not our continuous source.
We have been irradiating the A2036 and A2047 in gamma-rays. We summarize our experiments here. The A2047 is the radiation-tolerant version of our ATLAS Proximity Camera Head and In-Plane Head. When powered up but asleep, these circuits fail at roughly 270 Gy, at which point their VHC logic chips are no longer responding to commands. We note that the ATLAS circuits are powered off almost all the time during ATLAS running.
The A2036 fails because one particular part is vulnerable to ionizing radiation: the DG411DY. In one mode of failure, which occurs when the boards are irradiated while they are asleep, the −15 V power switch fails to close when the board wakes up, which occurs because a DG411DY switch fails to open. With only +15 V connected to the op-amps, they draw a total of 250 mA from the +15 V power supply. During the tests, the circuits are either asleep or powered off. When asleep, they have ±15 V connected to the analog switch, but the switches are open. When powered off, the LWDAQ Driver has disconnected its power supplies from its devices, so there is no power connected to the analog switch. When asleep, the A2036 fails after 10 Gy of gamma-rays. We delivered the gamma-rays at two doses: 30 Gy/hr and 3 Gy/hr and obtained the same result. We repeated with circuits we burned in for several days before the irradiation, and obtained the same result. With the boards powered off, they fail after 180 Gy of gamma rays. In the above plot we see the waking current consumption drop as the analog switches fail. This 180 Gy is our best estimate of the radiation tolerance of the A2036 during ATLAS running.
We obtain this plot of the change in threshold voltage of the NDS355AN versus gamma and x-ray dose. The two plots do not agree. The gamma dose appears to be more damaging. We consider the discrepancy between gamma-ray and x-ray damage in this report. But we later discover that our x-ray source is running at 40% of full power. If we reduce the x-ray flux to 40%, the gamma and x-ray effects are in much better agreement: a 1.0-V drop for gammas at 700 Gy and a 0.8-V drop for x-rays at 700 Gy.
[04-NOV-16] We compose the following table summarizing our radiation tolerance measurements so far. We assume the circuits will be operated with their power off almost all the time, as is the case in ATLAS. We use gamma-ray results in preference to x-ray when they are inconsistent.
|A2041N||Nine-LED Array for nSW||1600||70||16||5|
|A2074C/D||Dual Laser Head for nSW||1600||70||14||5|
|A2080A||36-Way Contact Injector for nSW||1600||50||20||3|
|A2082A||Bar Head for nSW||1600||50||20||3|
|A2083A/B||N-BCAM Head for nSW||1600||70||20||5|
|A2084A||6-Way Patch Panel for nSW||1600||30||20||2|
|A2085A||14-Way Multiplexer for nSW||1400||50||15||3|
|ICX424AL||Image Sensor for nSW||1400||70||14||5|
|LXML-PR01||Royal Blue LED for nSW||1400||70||16||5|
|LXZ1-PA01||Deep Red LED for nSW||1400||50||16||3|
|S705T-02F-62N3||Optical Fiber for nSW||2500||70||16||5|
[14-DEC-16] We find that we are running our continuous x-ray source at only 40% of full power. At range 74 cm the dose rate is 1.1 Gy/hr when we expect 2.9 Gy/hr. We increase the voltage to the opto-isolators that drive the x-ray control voltages and obtain 2.9 Gy/hr. We suspect that the opto-isolators have been ageing. The most recent calibration of our x-ray flux was SEP-15.
We irradiate four A2036 circuits in x-rays. They have power connected always, but are asleep except for once per hour when we wake them up and measure the difference between waking and sleeping current consumption. Two circuits have their top side, which is the side with the DG411DY, facing the source. Two circuits have the bottom side facing the source. We measure the dose rate at the location of the circuits with our Radcal ionizing chamber and get 1.1 Gy/hr. The two DG411s facing the source fail at 30 Gy and 33 Gy. The other two boards are still running at 180 Gy.
[19-DEC-16] We irradiate four A2036 circuits in x-rays, arranged as in the experiment above. They have power turned off always, except for a few seconds each hour, when we turn on power and measure the difference between waking and sleeping current consumption. The circuits are at range 74 cm from our continuous x-ray source. We measure dose rate 750 mR/min ≡ 2.9 Gy/hr. After 112 hours, all four circuits are still operational.
[22-DEC-16] We continue irradiating our four A2036 circuits. Two of them have failed, those with the DG411DY analog switch facing the x-ray source.
Failure of the DG411DY takes place after 340 Gy and 337 Gy for No1 and No4 respectively. In gamma rays, we saw failure after a dose of 180 Gy, assuming a dose rate of 3.0 Gy/hr, which is the dose rate in our cesium-137 source that we measured with our ionizing chamber. If we use the manufacturer's calibration of the cesium-137 source at our operating position, the dose rate is 4.3 Gy/hr, in which case the failure occurred at 260 Gy. Within the cesium-137 chamber, we locate our circuits at 18±1 cm, which gives us a ±10% uncertainty in the dose. The calibration of our x-ray source for silicon dose ignores absorption in the plastic package of the DG411DY. The absorption coefficient of carbon for 15-keV x-rays is 0.56 cm2/g, and the density of plastic is around 2 g/cm2, so 1 mm of plastic will absorb no more than 10% of 15-keV x-rays. Our x-rays are at least 15 keV, after passing through our aluminum absorber. We also use a scaling factor to convert ionizing dose in air to ionizing dose in silicon. This factor is 7.6, with uncertainty ±20%. Given all these sources of error in our measurement of absolute dose rate, 340 Gy in our x-ray test is consistent with 180 Gy in our gamma test.
[05-JAN-17] The A2036 No3 in our x-ray irradiation began to fail at around 1.1 kGy. The x-ray source shut down after 1.3 kGy. We re-started, but if turned off again within a few hours at 2.9 Gy/hr. We suspect that the failing No3 is shorting the ±15 V power supplies, and so turning off the x-ray source. Circuit No4 current consumption remains normal. Given that 75% of x-rays are absorbed by the circuit board, it appears that the analog switches on the far side of the circuit board fail at around 300 Gy, which is consistent with the failure of those on the front side at 340 Gy. Later, we run the x-ray source without the damage circuits connected to the LWDAQ and it is stable for a week.
[04-MAY-17] We place a prototype A2080A in our continuous x-ray source, bottom side facing the source at ruler position 100 cm where we measure dose rate 700 mR/min, which implies 2.7 Gy/hr in silicon. We leave power applied to the A2080A. Every hour we turn on each of its four installed Luxeon Z LEDs, deep-red LXZ1-PA01, green LXZ1-PM01, white LXZ2-5770, and deep-red LXZ1-PA01 to power level 7 of 0-10. We also turn on a non-existent LED. In each case we measure the increase in +15V current consumption.
[10-MAY-17] We remove our prototype A2080A after 400 Gy on the bottom side of the board. So far, the buck converter input currents have evolved as shown below.
We turn on each LED to power leval 7. We place a 1% neutral density filter over the LED and measure photocurrent with an SD445. For No1, deep-red, we get 1.1 mA, implying 275 mW output power. For No18, green, we get 0.15 mA implying 60 mW. For No23 we get 0.62 mA for white light. For No36 we get 1.13 mA implying 282 mW. Before irradiation, we obtained 310 mW from No36. We have a 9.0% drop in optical power output and a 9.5% drop in current consumption. When asleep, the board consumes 0.5 mA from +15V, 5.0 mA from +5V and 1.3 mA from −15V.
We turn the circuit board around, so that the top side with the LEDs faces the x-ray source at ruler position 80 cm. According to our measurements, the circuit board absorbs 75% of our x-ray dose. The top-side has already received 100 Gy. The source itself is at ruler 16 cm, so our new dose rate will be 4.0 Gy/hr.
[15-MAY-17] Our A2080A has received another 450 Gy of x-rays. The top-side total dose is 100 Gy from the first session and 450 Gy from the second session. The bottom side received 400 Gy in the first session and 510 Gy in the second. The following plot shows buck converter input current rising slightly, reversing the original drop of the first session.
We measure optical output at power level seven as described above. For No1 deep-red 310 mW, No18 green 79 mW, No23 white 0.63 mA photocurrent, No36 280 mW.
[07-SEP-17] We irradiate one Contact Injector A2080A with 14 Tn of fast neutrons in the reactor at UMass Lowell. We now have 35 LEDs and buck converters that have been subjected to the same 14 Tn. The power coupled into a 62-μm core NA=0.22 fiber is 35 μW before irradiation and 22 μW after. But leaving the LED running for 10 minutes the power increases to 28 mW. The next day and several days later, the recovery to 28 μW remains. We believe the self-heating of the LED annealed some of its neutron damage. When we remove an irradiated LED and replace it with a fresh one, we see no significant difference between the performance of an irradiated buck converter and an un-irradiated converter.
[24-JAN-18] We place our 2.4 μCi californium source, Cf-252, up against the window of a TC255P image sensor, cover with black cloth in a dark room, and take an image every two hours with a 100-ms exposure time. The sensor receives a dose rate of roughly 58 1-MeV eq. n/cm2/s, or 35 μTn/week. Pixels damaged by neutron collisions will show up in the images as bright points.
[23-MAR-18] Our TC255P has several bright pixels from neutron damage. We remove the Cf-252, but continue recording images from our TC255P image sensor to see how the dark current generated by the damaged pixels will evolve with time.
[18-MAY-18] We look through thirty thousand ATLAS dark-current images with the help of Inspect_Image.tcl and find roughly one thousand with optical images, or no sensor readout, or corrupted sensor readout. We enhance the BCAM instrument to allow us to select spots with a maximum number of pixels. We find and list bright pixels, dividing them up into files by image sensor name, with Bright_Pixels. We obtain the history of each bright pixel with Pixel_Histories.
[23-MAY-18] We select sixteen bright pixels in our neutron-irradiated TC255P. These are the pixels whose brightness is ten or more counts above the average intensity of the image for twenty-four consecutive hours at some time during the 2800-hour image record. With the help of the coordinates of these images, we use Neutron_Hit_Charge to get the net intensity (intensity above average) of these pixels in ever existing image.
We find the time at which each of these sixteen pixels was damaged, which we call their time of birth. We plot the sum of their intensities versus time since birth. It appears that we have roughly 50% reduction in dark current due to room-temperature annealing of neutron damage, which is consistent with our earlier tests of the TC255P.
The image sensor received 35 μTn/wk for nine weeks, or 310 μTn total. We expect the image sensor to exhibit roughly 0.28 count/ms/px/Tn at 20°C ignoring room-temperature annealing, or 87 μcount/ms/px. We see 160 count total damage charge from a 100-ms exposure of 84k pixels, so 19 μcount/ms/px.
[30-MAY-18] We turn on our continuous x-ray source. We place our Radcal dosimeter at ruler position range 100 cm from the source (the source is at ruler 16 cm and the dosimeter is at 116 cm). After some rotation of the x-ray tube we measure 460 mR/min = 1.7 Gy/hr at the center of the x-ray cone, which agrees well with our previous calibration, and 430 mR/min = 1.6 Gy/hr at either edge of the cone. At the center of the cone at range 50 cm (ruler 66 cm) we get 1.87 R/min = 7.1 Gy/hr. Our previous calibration at this range was 6.5 Gy/hr. We place a TC255P image sensor at range 50 cm (ruler 66 cm). With the Dosimeter Instrument, threshold "2 $", and 100-ms exposure of the sensor's masked storage area, we obtain charge density 1.0 counts/pixel at the center of the cone and 0.9 counts/pixel on either edge.
[31-MAY-18] We equip a Contact Injector (A2080A) with eight LuxeonZ LEDs of center wavelength 450 nm, 470 nm, 500 nm, 530 nm, 568 nm, 590 nm, 633 nm, and 655 nm. We have seven optical fibers 1.8 m long. Four we made out of our S705T-02F-62N3, named 1, 2, A, and B. Three we received from Fibernet. All have 2.5-mm zirconia ferrules on the ends, named 2821, 2065, and, 2835. We turn each of the LEDs on to full power in turn. We insert one end of each fiber into the injector in the order 1, A, 2821, 2065, 2835, B, 2. We hold the other end 1 mm from a SD445 photodiode and record the photodiode current with a DVM. We place A, 2821, 2065, 2835, and B at range 100 cm from our x-ray source. We turn on the source and leave it over-night. The fibers are receiving 1.7 Gy/hr.
[14-JUN-18] Our irradiation of fibers continues. The dose rate and temperature are well-behaved, and the x-ray AC power remains on, but the LWDAQ turns off the source at random ever few days.
After 230 Gy all five irradiated fibers have transmission 40% compared to start for 450 nm light, and 90% compared to strat for 650 nm light. | <urn:uuid:745dc02f-0312-4d78-8880-9286997ad7a5> | 2.6875 | 13,652 | Academic Writing | Science & Tech. | 76.180604 | 95,647,009 |
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The formation of galaxies is one of the greatest puzzles in astronomy, the solution is shrouded in the depths of space and time, but has profound implications for the universe we observe today. This book discusses the beginnings of the process from cosmological observations and calculations. It also considers the broad features of galaxies that we need to explain and what we know of their later history. The author compares the competing theories for galaxy formation and considers the progress expected from new generations of powerful telescopes both on earth and in space.
From a review of the first edition: "It is refreshing, in a market dominated by theorists, to come across a book on galaxy formation written from an observational perspective. The Road to Galaxy Formation should prove to be a handy primer on observations for graduate students, advanced undergraduates and theorists who feel too shy to visit a telescope." --Nature
"William Keel delicately balances observational evidence against today's relevant theoretical possibilities." --New Scientist
From the reviews of the second edition: "The work is clearly a labor of love. It immerses the reader in a thorough explanation of the latest data from modern ground- and space-based observatories. From Hubble's original galaxy classification system to the standard cosmological model, it is all here. This is a well-organized, well-placed, and thoroughly referenced 'golden review' of galactic formation and evolution--a must have for any serious student or scientist in the field. Summing Up: Essential. Upper-division undergraduate through professional collections." (T. D. Oswalt, CHOICE, Vol. 45 (8), 2008) "Keel explores in this book ! that the assembly of galaxies as we now see them has occurred continuously over the past 12 or 13 Gyr and can be studied in at least two ways: by looking far back, at large redshifts, and by winkling out the oldest stars surviving in the Milky Way and other nearby galaxies. ! Keel's style is conversational; indeed the book is delightfully written, and the annotations to the bibliographic items pithy and informative." (Virginia Trimble, The Observatory, Vol. 128 (1203), 2008)
1. A cosmological cartoon.- 2. Galaxies today.- 3. The fossil record in nearby galaxies.- 4. Measuring galaxies.- 5. Galaxy evolution.- 6. The intergalactic medium.- 7. The initial conditions before galaxy formation.- 8. Active galactic nuclei in the early Universe.- 9. Approaching the dark ages.- 10. The processes of galaxy formation.- 11. Forward to the past.
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Environmental data have inherent uncertainty which is often ignored in visualization. For example, meteorological stations measure wind with good accuracy, but winds are often averaged over minutes or hours. As another example, Doppler radars (wind profilers and ocean current radars) take thousands of samples and average the possibly spurious returns. Others, including time series data, have a wealth of uncertainty information that the traditional vector visualization methods such as using wind barbs and arrow glyphs simply ignore. We have developed new vector glyphs to visualize uncertain winds and ocean currents. Our approach is to include uncertainty in direction and magnitude, as well as the mean direction and length, in vector glyph plots. Our glyphs show the variation in uncertainty, and provide fair comparisons of data from instruments, models, and time averages of varying certainty. We use both qualitative and quantitative methods to compare our glyphs to traditional ones. Subjective comparison tests with experts (meteorologists and oceanographers) are provided, as well as objective tests (data ink manximization), where the information density of our new glyphs and traditional glyphs are compared. We have shown that visualizing data together with their uncertainty information enhances the understanding of the continuous range of data quality in environmental vector fields. | <urn:uuid:f1e5c9df-13a3-4b31-8ef0-af00db495a02> | 2.90625 | 252 | Academic Writing | Science & Tech. | 11.537824 | 95,647,032 |
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In mathematics and its applications, particularly to phase transitions in matter, a Stefan problem (also Stefan task) is a particular kind of boundary value problem for a partial differential equation (PDE), adapted to the case in which a phase boundary can move with time. The classical Stefan problem aims to describe the temperature distribution in a homogeneous medium undergoing a phase change, for example ice passing to water: this is accomplished by solving the heat equation imposing the initial temperature distribution on the whole medium, and a particular boundary condition, the Stefan condition, on the evolving boundary between its two phases. Note that this evolving boundary is an unknown (hyper-)surface: hence, Stefan problems are examples of free boundary problems.
The problem is named after Josef Stefan (Jožef Stefan), the Slovenian physicist who introduced the general class of such problems around 1890, in relation to problems of ice formation. This question had been considered earlier, in 1831, by Lamé and Clapeyron.
Premises to the mathematical description
From a mathematical point of view, the phases are merely regions in which the solutions of the underlying PDE are continuous and differentiable up to the order of the PDE. In physical problems such solutions represent properties of the medium for each phase. The moving boundaries (or interfaces) are infinitesimally thin surfaces that separate adjacent phases; therefore, the solutions of the underlying PDE and its derivatives may suffer discontinuities across interfaces.
The underlying PDE is not valid at phase change interfaces; therefore, an additional condition—the Stefan condition—is needed to obtain closure. The Stefan condition expresses the local velocity of a moving boundary, as a function of quantities evaluated at both sides of the phase boundary, and is usually derived from a physical constraint. In problems of heat transfer with phase change, for instance, the physical constraint is that of conservation of energy, and the local velocity of the interface depends on the heat flux discontinuity at the interface.
The one-dimensional one-phase Stefan problem
Consider a semi-infinite one-dimensional block of ice initially at melting temperature u ≡ 0 for x ∈ [0, +∞). Heat flux of f(t) is introduced at the left boundary of the domain causing the block to melt down leaving an interval [0, s(t)] occupied by water. The melted depth of the ice block, denoted by s(t), is an unknown function of time; the solution of the Stefan problem consists of finding u and s such that
Apart from the modelling of melting of solids, Stefan problems are also used as models for the asymptotic behaviour with respect to time of more complex problems: for example, Pego uses matched asymptotic expansions to prove that Cahn-Hilliard solutions for phase separation problems behave as solutions to a nonlinear Stefan problem at an intermediate time scale. Additionally, the solution of the Cahn–Hilliard equation for a binary mixture is reasonably comparable with the solution of a Stefan problem. In this comparison, the Stefan problem was solved using a front-tracking, moving-mesh method with homogeneous Neumann boundary conditions at the outer boundary. Also, Stefan problems can be applied to describe phase transformations.
- (Vuik 1993, p. 157).
- R. L. Pego. (1989). Front Migration in the Nonlinear Cahn-Hilliard Equation. Proc. R. Soc. Lond. A.,422:261–278.
- Vermolen, F. J.; Gharasoo, M. G.; Zitha, P. L. J.; Bruining, J. (2009). "Numerical Solutions of Some Diffuse Interface Problems: The Cahn–Hilliard Equation and the Model of Thomas and Windle". International Journal for Multiscale Computational Engineering. 7 (6): 523–543. doi:10.1615/IntJMultCompEng.v7.i6.40.
- Alvarenga HD, Van de Putter T, Van Steenberge N, Sietsma J, Terryn H (Apr 2009). "Influence of Carbide Morphology and Microstructure on the Kinetics of Superficial Decarburization of C-Mn Steels". Metal Mater Trans A. 46: 123. Bibcode:2015MMTA...46..123A. doi:10.1007/s11661-014-2600-y.
- (Kirsh 1996).
- Vuik, C. (1993), "Some historical notes about the Stefan problem", Nieuw Archief voor Wiskunde, 4e serie, 11 (2): 157–167, MR 1239620, Zbl 0801.35002. An interesting historical paper on the early days of the theory: a preprint version (in PDF format) is available here .
Scientific and general references
- Cannon, John Rozier (1984), The One-Dimensional Heat Equation, Encyclopedia of Mathematics and Its Applications, 23 (1st ed.), Reading–Menlo Park–London–Don Mills–Sydney–Tokyo/ Cambridge–New York City–New Rochelle–Melbourne–Sydney: Addison-Wesley Publishing Company/Cambridge University Press, pp. XXV+483, ISBN 978-0-521-30243-2, MR 0747979, Zbl 0567.35001. Contains an extensive bibliography, 460 items of which deal with the Stefan and other free boundary problems, updated to 1982.
- Kirsch, Andreas (1996), Introduction to the Mathematical Theory of Inverse Problems, Applied Mathematical Sciences series, 120, Berlin–Heidelberg–New York: Springer Verlag, pp. x+282, ISBN 0-387-94530-X, MR 1479408, Zbl 0865.35004
- Meirmanov, Anvarbek M. (1992), The Stefan Problem, De Gruyter Expositions in Mathematics, 3, Berlin – New York: Walter de Gruyter, pp. x+245, doi:10.1515/9783110846720, ISBN 3-11-011479-8, MR 1154310, Zbl 0751.35052. – via De Gruyter (subscription required) An important monograph from one of the leading contributors to the field, describing his proof of the existence of a classical solution to the multidimensional Stefan problem and surveying its historical development.
- Oleinik, O. A. (1960), "A method of solution of the general Stefan problem", Doklady Akademii Nauk SSSR (in Russian), 135: 1050–1057, MR 0125341, Zbl 0131.09202. The paper containing Olga Oleinik's proof of the existence and uniqueness of a generalized solution for the three-dimensional Stefan problem, based on previous researches of her pupil S.L. Kamenomostskaya.
- Kamenomostskaya, S. L. (1958), "On Stefan Problem", Nauchnye Doklady Vysshey Shkoly, Fiziko-Matematicheskie Nauki (in Russian), 1 (1): 60–62, Zbl 0143.13901. The earlier account of the research of the author on the Stefan problem.
- Kamenomostskaya, S. L. (1961), "On Stefan's problem", Matematicheskii Sbornik (in Russian), 53(95) (4): 489–514, MR 0141895, Zbl 0102.09301. In this paper the author proves the existence and uniqueness of a generalized solution for the three-dimensional Stefan problem, later improved by her master Olga Oleinik.
- Rubinstein, L. I. (1971), The Stefan Problem, Translations of Mathematical Monographs, 27, Providence, R.I.: American Mathematical Society, pp. viii+419, ISBN 0-8218-1577-6, MR 0351348, Zbl 0219.35043. A comprehensive reference, written by one of the leading contributors to the theory, updated up to 1962–1963 and containing a bibliography of 201 items.
- Tarzia, Domingo Alberto (July 2000), "A Bibliography on Moving-Free Boundary Problems for the Heat-Diffusion Equation. The Stefan and Related Problems", MAT, Series A: Conferencias, seminarios y trabajos de matemática., 2: 1–297, ISSN 1515-4904, MR 1802028, Zbl 0963.35207. The impressive personal bibliography of the author on moving and free boundary problems (M–FBP) for the heat-diffusion equation (H–DE), containing about 5900 references to works appeared on approximately 884 different kinds of publications. Its declared objective is trying to give a comprehensive account of the existing western mathematical–physical–engineering literature on this research field. Almost all the material on the subject, published after the historical and first paper of Lamé–Clapeyron (1831), has been collected. Sources include scientific journals, symposium or conference proceedings, technical reports and books.
- Vasil'ev, F. P. (2001) , "Stefan condition", in Hazewinkel, Michiel, Encyclopedia of Mathematics, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4
- Vasil'ev, F. P. (2001) , "Stefan problem", in Hazewinkel, Michiel, Encyclopedia of Mathematics, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4
- Vasil'ev, F. P. (2001) , "Stefan problem, inverse", in Hazewinkel, Michiel, Encyclopedia of Mathematics, Springer Science+Business Media B.V. / Kluwer Academic Publishers, ISBN 978-1-55608-010-4 | <urn:uuid:7a024cf4-2eac-4a00-8ac2-8f8d0fbaed68> | 3.5 | 2,158 | Knowledge Article | Science & Tech. | 54.347994 | 95,647,036 |
Renewable energy has been replacing traditional non-renewable energy owing to the limitation of the latter and environmental protection. Renewable energy is energy that can be circularly regenerated in nature. It mainly includes solar energy, wind energy, biomass energy, tidal energy and ocean thermal energy, just name a few.
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Lagoons represent nearly 13% of the shoreline globally and around 5% in Europe. Coastal lagoons are shallow water bodies separated from the ocean by a barrier (e.g., narrow spit), connected at least intermittently to the ocean by one or more restricted inlets, and usually geographically oriented parallel to the shore-line. Coastal lagoons are flexible and usually able to cope with environmental change, yet nowadays they are under threat. This is partly due to climate change impacts (for example, sea-level rise and hydro-meteorological extreme events) but also due to more direct human activities and pressures.
The book focuses on addressing these challenges through integrated management strategies seen in a land-sea and science-stakeholder-policy perspective. Pan-European management challenges are seen from the context of the perspectives of Policy, Environment and Modelling. Four case study lagoons in different geographical locations in Europe provide examples of some of the practical experiences and results around these challenges. Possible impacts on drainage basins and lagoons are introduced through integrated scenarios which were developed through a multi-science and land-lagoon science perspective combined with interactions and contributions from stakeholders and citizens.
Issues around climate change impacts on environmental conditions in both drainage basins and lagoons are also included.
The book derives from a collaborative EC-funded project entitled Integrated Water Resources and Coastal Zone Management in European Lagoons in the Context of Climate Change comprising nine partner institutes with a wide diversity in the scientific disciplines covered.
This title belongs to Water Research Series
ISBN: 9781780406299 (eBook)
ISBN: 9781780406282 (Print)
This eBook was made Open Access in May 2016
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A dinosaur tail with beautifully preserved feathers still attached to the bone has been found preserved in amber, and it's one of the coolest things we've ever seen.
It's not the first time feathers have been found trapped in amber, but it is the first time that researchers have been able to definitively link them to a dinosaur. The discovery will provide invaluable insight into how dinosaurs' feathers looked and evolved - something we've never been able to learn from fossils.
"It's a once in a lifetime find," one of the researchers, Ryan McKellar from the Royal Saskatchewan Museum in Canada, told CNN. "The finest details are visible and in three dimensions."
Amazingly, the piece of amber was found at a market in Myanmar last year, where it was being sold as a chunk of amber containing plant material.
Lead researcher Lida Xing, from the China University of Geoscience in Beijing, immediately recognised that there were feathers inside, and teamed up with McKellar to learn more about the unique specimen.
Using detailed microscopy and a CT scanner to observe the structure of the feathers and the bones they were attached to, the team predicts that the tail belonged to a young coelurosaur, a family of bird-like carnivorous dinosaurs that lived around 99 million years ago during the Cretaceous era.
As far as researchers are aware, these are the first non-avian dinosaur feathers found preserved in amber.
"The new material preserves a tail consisting of eight vertebrae from a juvenile; these are surrounded by feathers that are preserved in 3D and with microscopic detail," said McKellar in a press release.
"We can be sure of the source because the vertebrae are not fused into a rod or pygostyle as in modern birds and their closest relatives. Instead, the tail is long and flexible, with keels of feathers running down each side."
In other words, the feathers definitely belong to a dinosaur, not a prehistoric bird.
The team has now nicknamed the young coelurosaur 'Eva', and at the time of her unfortunate death she would have been around the size of a sparrow - but fully grown would have been a little smaller than an ostrich.
The family she belongs to is closely related to iconic meat-eaters such as T. rex and Velociraptor - but as the new discovery shows, Eva was most likely more cute and fluffy.
Analysis of the feathers suggest that the tail had a chestnut-brown upper surface and a pale or white underside.
Interestingly, the feathers are missing a well-developed central shaft, also known as a 'rachis'. This could help answer one of the long-standing questions in feather evolution - did feathers start out stiff and spiky with a central shaft, or were they originally fluffy and floppy?
It's an important question, seeing as researchers think that, without that central shaft, flight wouldn't have been possible.
The new discovery leans on the side of the fluffy parts of the feather coming first, but we'll need to find a lot more preserved feathers from the era and examine them before we can say for sure.
The team also studied the chemistry of the specimen where it was exposed at the surface of the amber, and showed that the soft tissue layer around the bones had traces of ferrous iron - the remains of haemoglobin from Eva's blood that was also trapped in the sample.
The hope now is that the team will find more of these remains trapped in amber - and maybe even one day a partial or complete dinosaur - to help compliment all the incredible things we've learnt about dinosaurs from the fossil record.
"It's a spectacular little glimpse," McKellar told NPR. "It gives us, basically, a pathway that gets us to modern feathers."
The research has been published in Current Biology.
Read the original article on ScienceAlert. Copyright 2016. Follow ScienceAlert on Twitter. | <urn:uuid:e968180f-8c8f-49dc-8d6f-187d84533d92> | 3.4375 | 809 | News Article | Science & Tech. | 45.590714 | 95,647,062 |
Dark matter holds the universe together right? Well, the theory of dark matter may be widely believed, but there isn't much of it in our part of the universe. The research team puts forward its findings. Believers question the accuracy of what they have found.
This isn't a question of how much is out there. The team found no dark matter at all. The dark matter theory holds that dark matter should be plentiful, everywhere. As much as 85 per cent of everything should be dark matter. The sun should be pulled around with dark matter. Unfortunately, scientists cannot find it.
Dark matter theory is based on the premise that stars trapped in a gravitational well light years away travel at a fixed speed. This, with the shape of the well allows a calculation to be made. Star counts give the amount of ordinary matter. subtracting this from the mass determined from the calculation gives the amount of dark matter.
The team found that the dark matter theory was questionable. The speed of the stars did not need dark matter to explain it. | <urn:uuid:4a71a256-9def-4648-bc5e-6d158df862e7> | 3.546875 | 211 | Personal Blog | Science & Tech. | 68.427711 | 95,647,078 |
Kostal Cone is made of fragmented and solidified lava called cinder and its summit contains a bowl-shaped crater. Kostal's cinders were ejected by lava fountain eruptions and accumulated around the volcano's vent in the shape of a cone when they fell back around its surroundings. Lava flows from Kostal's 400 BP eruption are basaltic in composition and forms a lava bed. This lava bed dams the southern end of McDougall Lake and is just one of the examples of volcanic activity that have occurred in the Wells Gray-Clearwater volcanic field since the last glacial period; others include the "Dragon's Tongue" lava flow from Dragon Cone just north of Kostal Cone.
There has been activity at this site as recently as 7,600 years ago, though more likely less than 1,000 years ago. Kostal Cone is too young for the commonly used potassium-argon dating technique (usable on specimens over 100,000 years old), and no charred organic material for radiocarbon dating has been found. However, the uneroded structure of the cone with the existence of trees on its flanks and summit have it an area for dendrochronology studies, which reveals the growth of tree-ring patterns. Tree-ring dating has revealed an age of 400 years for Kostal Cone, making it the youngest volcano in the Wells Gray-Clearwater volcanic field and one of the youngest volcanoes in Canada. | <urn:uuid:82d93dd1-24bc-4b0d-a71c-0bae416b5f31> | 3.875 | 303 | Knowledge Article | Science & Tech. | 40.313686 | 95,647,080 |
A study conducted by University of Utah genetics researchers shows that the steroid hormone ecdysone controls an important phase in the embryonic development of insects, providing an unexpected parallel with the role of the hormone in controlling metamorphosis. The studys findings also give scientists new insights into how steroids control maturation in higher organisms.
Carl S. Thummel, Ph.D., a Howard Hughes Medical Institute investigator and professor of human genetics at the University of Utah School of Medicine, said that although other studies have established a critical role for ecdysone in controlling insect metamorphosis, very little was known about roles for the hormone during embryonic development.
To find the answer, Thummel and Tatiana Kozlova, a Howard Hughes Medical Institute research associate, looked at the activation pattern of the receptor for ecdysone. They found that this receptor is highly activated in an extraembryonic tissue called amnioserosa, a tissue that does not itself form part of the embryo, but is nonetheless required for embryonic development. Thummel said the source of ecdysone in the early embryo, prior to the development of the insect endocrine organ, has always baffled scientists. "Our findings suggest that the earliest source of hormone is the amnioserosa," he said, "although other sources are likely to contribute at later times."
Cindy Fazzi | EurekAlert!
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
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Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
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18.07.2018 | Health and Medicine | <urn:uuid:db3937f2-e334-4e8a-b63f-3e6da7f60105> | 2.96875 | 916 | Content Listing | Science & Tech. | 34.479407 | 95,647,118 |
The hippocampus in the brain's temporal lobe is responsible for more than just long-term memory. Researchers have for the first time demonstrated that it is also involved in quick and successful conflict resolution. The team headed by Prof Dr Nikolai Axmacher from the Ruhr-Universität Bochum (RUB), together with colleagues from the University Hospital of Bonn as well as in Aachen and Birmingham, reported in the journal "Current Biology".
Decision conflicts occur often in everyday life
In situations of conflict, people have to decide fast what to do. The hippocampus seems to be involved in this process.
RUB, photo: Marquard
In their everyday life, people are constantly confronted with decision conflicts, especially if they need to suppress an action that would have made sense under normal circumstances. For example: when the pedestrian lights go green, a pedestrian would normally start walking. If, however, a car comes speeding along at the same time, the pedestrian should stay where he is.
In their experiment, researchers opted for a less threatening situation. Test participants heard the words "high" or "low” spoken in a high or low tone, and they had to state – regardless of the meaning of the word – at what pitch the speaker said them. If the pitch doesn't correspond with the meaning of the word, a conflict is generated: the participants would answer more slowly and make more mistakes.
Results confirmed with two measurement methods
The team demonstrated with two different measurement methods that the hippocampus is active in such conflicting situations; this applies particularly when a person solves the conflicts quickly and successfully. Nikolai Axmacher from the Institute of Cognitive Neuroscience and his colleagues analysed the brain activity in healthy participants with functional magnetic resonance imaging.
They gained the same results in epilepsy patients who had EEG electrodes implanted in the hippocampus for the purpose of surgery planning; this is how the researchers could measure the activity in that brain region directly.
Memory system could learn from resolved conflicts
Because the hippocampus is essential for memory, the researchers speculate about its role in conflict resolution: "Our data show first of all a completely new function of the Hippocampus – processing of activity conflicts," says Carina Oehrn from the Department of Epileptology at the University Hospital of Bonn. "However, in order to answer the question how that function interacts with memory processes, we will have to carry out additional tests."
"Perhaps the memory system becomes particularly active if a conflict has been successfully resolved," speculates Nikolai Axmacher. "Permanently unsolved conflicts can't be used for learning helpful lessons for the future. According to our model, the brain works like a filter. It responds strongly to resolved conflicts, but not to unsolved conflicts or standard situations. However, we have to verify this hypothesis in additional studies."
C.R. Oehrn, C. Baumann, J. Fell, H. Lee, H. Kessler, U. Habel, S. Hanslmayr, N. Axmacher (2015): Human hippocampal dynamics during response conflict, Current Biology, DOI: 10.1016/j.cub.2015.07.032
Prof Dr Nikolai Axmacher, Department of Neuropsychology, Institute of Cognitive Neuroscience, Faculty of Psychology at the Ruhr-Universität, 44780 Bochum, Germany, phone: +49/234/32-22674, email: email@example.com
Carina Oehrn, Department of Epileptology, University Hospital of Bonn, Sigmund-Freud-Straße 25, 53127 Bonn, Germany, Phone: +49/228 287-19345, Email: Carina.Oehrn@ukb.uni-bonn.de
Editor: Dr Julia Weiler
Jens Wylkop | Ruhr-Universität Bochum
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For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
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For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
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Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
Ultra-short, high-intensity X-ray flashes open the door to the foundations of chemical reactions. Free-electron lasers generate these kinds of pulses, but there is a catch: the pulses vary in duration and energy. An international research team has now presented a solution: Using a ring of 16 detectors and a circularly polarized laser beam, they can determine both factors with attosecond accuracy.
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But a group of researchers at the University of Wisconsin–Madison is examining alternative materials that can be modified to absorb oil and chemicals. If further developed, the technology may offer a cheaper and “greener” method to absorb oil and heavy metals from water and other surfaces.
Shaoqin “Sarah” Gong, a researcher at the Wisconsin Institute for Discovery's BIONATES research group and associate professor of biomedical engineering, along with graduate student Qifeng Zheng, and Zhiyong Cai, a project leader at the USDA Forest Products Laboratory in Madison, have recently created the patent-pending aerogel technology.
Aerogels, which are highly porous materials and the lightest solids in existence, are already used in a variety of applications, ranging from insulation and aerospace materials to thickening agents in paints. The aerogel prepared in Gong’s lab is made of cellulose nanofibrils (sustainable wood-based materials) and an environmentally friendly polymer. Furthermore, these cellulose-based aerogels are made using an environmentally friendly Photos: Bryce Richterfreeze-drying process without the use of organic solvents.
It’s the combination of this “greener” material and its high performance that got Gong’s attention.
“For this material, one unique property is that it has superior absorbing ability for organic solvents — up to nearly 100 times its own weight,” she says. “It also has strong absorbing ability for metal ions.”
Treating the cellulose-based aerogel with specific types of silane after it is made through the freeze-drying process is a key step that gives the aerogel its water-repelling and oil-absorbing properties.
“So if you had an oil spill, for example, the idea is you could throw this aerogel sheet in the water and it would start to absorb the oil very quickly and efficiently,” she says. “Once it’s fully saturated, you can take it out and squeeze out all the oil. Although its absorbing capacity reduces after each use, it can be reused for a couple of cycles.”
In addition, this cellulose-based aerogel exhibits excellent flexibility asdemonstrated by compression mechanical testing.
Though much work needs to be done before the aerogel can be mass-produced, Gong says she’s eager to share the technology’s potential benefits beyond the scientific community.
“We are living in a time where pollution is a serious problem — especially for human health and for animals in the ocean,” she says. “We are passionate to develop technology to make a positive societal impact.”
Gong and her colleagues have featured their findings in the Journal of Materials Chemistry A.
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Deposits in lakes and seas contain a wealth of information related to the environ-mental conditions prevalent during their genesis. Thus, they are an unfailing archive, particularly with regard to paleo-environmental conditions, for environmental and climate scientists. Now, the fine art is to interpret the derived data correctly.
For this purpose, geoscientists often use "witnesses" or proxies. Widely known witnesses from sediments are fossils, the remains of plants and animals. By comparisons with their well-studied living relatives, ideas about the conditions that predominated at the time of sediment deposition can be deduced. Minerals potentially offer further valuable insights but only if the environmental circumstances present at the time of their formation have been deciphered.
A team of researchers from Germany, Austria and Spain, under the co-ordination of geochemists from the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) has now succeeded in reproducing the formation of a BaMn-double carbonate originally found in sediments from the oxygen-deficient region of the Landsort Deep in the laboratory, and thus to elucidate the environmental conditions that gave birth to it. This carbonate, which has yet to be named, serves as a mineral witness for future research to hone in on very specific biogeochemical processes and environmental conditions.
„Sediments in which barium-manganese carbonate are found contain dissolved methane“says Michael E. Böttcher, the leading scientist. "We were able to demonstrate that the prerequisite for the genesis of this carbonate was the microbial decomposition of sulfate and the destruction of barium and manganese minerals stemming from the water column. Methane seems to be involved in these processes.” The consortium around Michael Böttcher used a broad range of methods resulting in a detailed characterization of the carbonate enable its unmistakable detection in other locations.
Thus, wherever this new mineral witness is found, additional important information on the environmental conditions at the time of the carbonate's deposition will be revealed, thanks to the fundamental work of the Warnemünde-based geochemists and their co-workers. The word is out - the search can begin.These results were published in:
The IOW is a member of the Leibniz Association, which currently includes 86 research insti-tutes and a scientific infrastructure for research. The Leibniz Institutes' fields range from the natural sciences, engineering and environmental sciences, business, social sciences and space sciences to the humanities. Federal and state governments together support the Institute. In total, the Leibniz Institute has 16 800 employees, of which approximately are 7,800 scientists, and of those 3300 young scientists. The total budget of the Institute is more than 1.4 billion Euros. Third-party funds amount to approximately € 330 million per year.
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A new manufacturing technique uses a process similar to newspaper printing to form smoother and more flexible metals for making ultrafast electronic devices.
The low-cost process, developed by Purdue University researchers, combines tools already used in industry for manufacturing metals on a large scale, but uses...
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
To rule out other origins with certainty, the team led by neutrino physicist Elisa Resconi from the Technical University of Munich and multi-wavelength...
For the first time a team of researchers have discovered two different phases of magnetic skyrmions in a single material. Physicists of the Technical Universities of Munich and Dresden and the University of Cologne can now better study and understand the properties of these magnetic structures, which are important for both basic research and applications.
Whirlpools are an everyday experience in a bath tub: When the water is drained a circular vortex is formed. Typically, such whirls are rather stable. Similar...
Physicists working with Roland Wester at the University of Innsbruck have investigated if and how chemical reactions can be influenced by targeted vibrational excitation of the reactants. They were able to demonstrate that excitation with a laser beam does not affect the efficiency of a chemical exchange reaction and that the excited molecular group acts only as a spectator in the reaction.
A frequently used reaction in organic chemistry is nucleophilic substitution. It plays, for example, an important role in in the synthesis of new chemical...
Optical spectroscopy allows investigating the energy structure and dynamic properties of complex quantum systems. Researchers from the University of Würzburg present two new approaches of coherent two-dimensional spectroscopy.
"Put an excitation into the system and observe how it evolves." According to physicist Professor Tobias Brixner, this is the credo of optical spectroscopy....
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20.07.2018 | Materials Sciences | <urn:uuid:69c85361-0148-425f-ab5e-b9468b6b4081> | 3.6875 | 1,174 | Content Listing | Science & Tech. | 32.477604 | 95,647,148 |
This function returns the end of line (EOL) text marker, also known as CRLF (carriage return line feed ~ #13 #10).
@EOL() : String
String split := @EOL();
String file := "c:\test\file_in_utf8.txt";
Integer cpUTF8 := 65001; //the utf8 codepage;
@FileReadTextLines(file, cpUTF8, textLines, split);
//Now the file was read - converting from utf8 - and
//the imported text was divided into lines using CRLF
//as the split factor. | <urn:uuid:c8248544-2f98-4051-a918-818c3f030bd6> | 3 | 139 | Documentation | Software Dev. | 60.925417 | 95,647,165 |