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An unornamented, thickened area in the central portion of a valve in the genus Stauroneis. Some references consider fascia and stauros as equivalent terms, although recent work (Cox 1999, 2001, 2012) has shown that the stauros has a distinct pattern of development that differs from that of other genera. During valve formation in Stauroneis, a transverse strip of silica develops from each side of the central nodule.
Cox, E.J. (1999). Craspedostauros gen. nov., a new diatom genus for some unusual marine raphid diatoms previously placed in Stauroneis Ehrenberg and Stauronella Mereschkowsky (Bacillariophyta) . European Journal of Phycology 34: 131–47.
Cox, E.J. (2001). What constitutes a stauros? A morphogenetic perspective . In Jahn, R., Witkowski, A. & Compe`re, P. [Eds.] Festschrift füe H. Lange-Bertalot. A.R.G. Gantner Verlag K.G, Ruggell, Liechtenstein, pp. 303–16.
Cox, E.J. (2012). Ontogeny, homology, and terminology - wall morphogenesis as an aid to character recognition and character state definition for pennate diatom systematics . J. Phycol. 48: 1–31. 10.1111/j.1529-8817.2011.01081.x | <urn:uuid:ca97cddd-b890-4504-bd70-cdb98315cbf3> | 3.0625 | 341 | Structured Data | Science & Tech. | 64.22378 |
The first identified compact galaxy group,
is featured in
this eye-catching image constructed with data drawn from
the extensive Hubble Legacy Archive.
About 300 million light-years away, only four of these five galaxies
in a cosmic dance
of repeated close encounters.
The odd man out is easy to spot, though.
The interacting galaxies,
NGC 7319, 7318A, 7318B, and 7317
have an overall yellowish cast.
They also tend to have distorted
loops and tails, grown under the
influence of disruptive gravitational tides.
But the predominantly bluish galaxy, NGC 7320,
is closer, just 40 million light-years distant,
and isn't part of the interacting group.
lies within the boundaries of the high flying
At the estimated distance of the quartet of interacting galaxies,
this field of view spans about 500,000 light-years.
However, moving just beyond this field, above and to the left,
astronomers can identify another galaxy,
NGC 7320C, that is also 300 million
Of course, including it would bring the
interacting quartet back up to quintet status. | <urn:uuid:4a7cf827-9ea9-42e7-b12e-164307a0fa9c> | 2.859375 | 249 | Knowledge Article | Science & Tech. | 50.076217 |
So, what happened to the mass?
So, we need a massive disk to build the KBOs, but then we cannot get rid of it.
- Dynamical excitation: Something excited the KB feeding most of mass inward.
- There have been three suggestions:
- ~Earth-mass objects scattered outward by Neptune.
(Morbidelli & Valsecchi; Petit et al.)
- Uranus and Neptune scattered outward by Saturn and Jupiter (Thommes et al.)
- Passing star (Ida et al; Kobayashi & Ida).
- Each of these removes mass by putting it on high eccentricity orbits.
- So, feeds the material to Neptune. Neptune migrates!!!!!!
- Neptune can't clear enough stuff to build the KBOs and remain near 30AU! (Gomes et al.)
- Collisional Grinding: In an excited KB collisions grind it down. (Stern & Colwell)
- Requires a strange size distribution and very weak objects.
- It is difficult to set up a system that is stable long enough.
- Collisional grinding would have driven the secular resonance through the disk feeding most of the mass to Neptune.
- Observed KBO binaries would not have survived (Petit). | <urn:uuid:e62b159c-b0ce-4645-a7cf-353bb0e8a796> | 2.875 | 268 | Q&A Forum | Science & Tech. | 57.580519 |
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role in evolution theory
In some modes of speciation the first stage is achieved in a short period of time. These modes are known by a variety of names, such as quantum, rapid, and saltational speciation, all suggesting the shortening of time involved. They are also known as sympatric speciation, alluding to the fact that quantum speciation often leads to speciation...
What made you want to look up "quantum speciation"? Please share what surprised you most... | <urn:uuid:21dc32bd-dd62-4956-bcbb-98475ab56224> | 3.140625 | 137 | Truncated | Science & Tech. | 50.69079 |
In July 2008, Chabot Space & Science Center's 36-inch telescope, Nellie, was officially designated Observatory G-58 by the International Astronomical Union's Minor Planet Center (MPC), and selected to contribute to its Near Earth Object (NEO) detection and tracking program.
In this program, observatories around the world contribute by searching for and tracking NEOs: asteroids, and comets, whose orbits can carry them close to Earth and which are large enough to cause catastrophic damage should they hit us.
How Do You Find a NEO?
The process for finding, tracking, and reporting NEO observations goes something like this. With a digital (CCD) camera attached to the telescope, a section of the sky is imaged three or four times in a half-hour period. The images are processed and compared, and any star-like dots that are found to move between one image and the next become suspect asteroids. (The word "asteroid," by the way, literally means "star-like” - so named because through most telescopes asteroids are too far away and too small to appear as anything more than points of light.)
The coordinates of any moving dots are calculated for all of the images they are in, and this information is sent to the MPC to be added to the data from other NEO hunting observatories. From the combined observations of all the observatories, a precision database of the orbits of near-Earth rocks is maintained, and with it NEOs that may pose a threat to the Earth may be identified.
How Did Nellie Join the Search?
In order to take part in the NEO program, Chabot observers Conrad Jung (on the Chabot staff) and Gerald McKeegan (of the Eastbay Astronomical Society) conducted a four-month program to develop and hone the necessary skills and data processing techniques, as well as to configure telescope equipment, to meet MPC qualifications.
To that end, they observed a set of known asteroids-some NEO’s and some "Main Belt" asteroids. (One of these Main Belt asteroids, "Carter 10683," was named for former Chabot board member and president of the Eastbay Astronomical Society, Carter Roberts, who, sadly, passed away in early 2008.)
The Hunt is On
Chabot’s asteroid hunters will begin their tenure of official asteroid observation by verifying the orbits of recently discovered NEOs and reporting the additional observations to the MPC, where it will be used to refine our knowledge of the NEOs' orbits. The next step in the program ultimately will be to hunt for currently undiscovered asteroids. | <urn:uuid:5f38c839-1ad6-4d8b-8532-579e49cd29be> | 3.671875 | 543 | Knowledge Article | Science & Tech. | 35.732786 |
Firestorm: Weather on a Neutron Star
by Steven Whitt
Imagine yourself in a sea of molten iron. A cloud of superhot gas spirals overhead. Moments later, that same cloud explodes with the fury of billions upon billions of hydrogen bombs. The explosion drives the molten sea into a frenzy, stirring up storm waves that will endure for 300 “days.”
What you've just witnessed, according to Dr. Jeremy Heyl of the Harvard-Smithsonian Center for Astrophysics, is some of the most extreme weather in the universe—weather that occurs at the surface of a neutron star.
A neutron star is the squashed remains of a star that has blown itself apart in a supernova explosion. What's left is a hot, smooth ball the size of a city, but with the mass of our sun. Neutron stars are so squashed (or dense, as a scientist would say) that a golf ball-size chunk would weigh as much as a mountain.
Like other stars, neutron stars spin. But like an ice skater pulling in her arms while twirling, a neutron star spins faster and faster as it squashes itself smaller and smaller. A neutron star can spin (or rotate) hundreds of times every second, making the neutron star “day” short indeed.
Now imagine another, more ordinary star (like our sun) in orbit with a neutron star. Scientists call this a double star, or binary, system. Like a great cosmic vacuum cleaner, the neutron star pulls gas from the surface of its neighbor. This stolen cloud of gas spirals toward the neutron star, and then explodes in a nuclear fusion reaction—like the reactions that power hydrogen bombs, yet inconceivably larger.
The waves made by the explosion take around 300 rotations of the neutron star (300 “days”) to spread across its surface. The way these waves spread is amazingly similar to the way large-scale weather systems—such as El Niño—spread on Earth. Like neutron star weather systems, El Niño takes about 300 Earth rotations (our “days”) to develop, grow, and disappear. “Whether on a neutron star rotating 300 times a second, or on Earth rotating once every day,” says Dr. Heyl, “these weather systems are governed by the same physics.”
Keep in mind that these neutron star weather patterns occur in a fraction of a second of Earth time. So if you don't like the weather on a neutron star, just hang around. In the blink of an eye, it'll change.
- El Niño:
- A disruption of the ocean-atmosphere system in the tropical Pacific having important consequences for weather around the globe, including increased rainfall across the southern tier of the United States.
- What is a binary system? What happens in a binary system?
[anno: A binary system is a neutron star in orbit with a regular star, like our sun. In a binary system, the neutron star pulls gas off of the other star. The gas powers explosions on the neutron star's surface.]
- Why do you think that the gas flows in a particular direction in a binary system?
[anno: Since a neutron star is much denser than a regular star, it probably has a greater gravitational pull than a regular star. Therefore, it pulls the gas of a regular star toward itself.]
- What would happen if scientists could harness the energy produced by a neutron star?
[anno: Answers may vary but could include that if the energy of a neutron star could be harnessed, we might not have anymore fuel concerns in the world. Students might also suggest that harnessing the energy of a neutron star might make space travel easier.] | <urn:uuid:f1366c71-51b8-4dec-be3a-eed1d1e8e5c1> | 4.125 | 775 | Truncated | Science & Tech. | 58.661048 |
Got a question about the Higgs boson, Cern or the Large Hadron Collider, but been too afraid to ask? As we report live from Geneva on scientists' latest efforts to find the 'God particle', two leading physics professors came online to take your questions.
Professor Stefan Soldner-Rembold, professor of particle physics at the School of Physics and Astronomy, University of Manchester, and Professor Andy Parker, professor of high energy physics at the University of Cambridge, were available to answer your questions about the Higgs boson. The Q&A has now ended.
Whether you're trying to get to grips with what Higgs boson is and need a lay-person's explanation, or whether you're interested in what this means for physics as a field, we hope the thread below will help.
To get us started we asked them to tell us:
What is the Higgs boson?
Most people imagine particles of matter to be like little billiard balls, which are stuck together in some way to make the solid objects which we see around us. We naturally expect the billiard balls to have some substance in their own right, making them, and everything which they form, massive. However, in modern quantum theories, matter is nothing like this. All the particles would, if left to themselves, have no mass at all, and fly around at the speed of light. There would be no atoms or people to study them.
The Higgs field is the proposed answer to this mismatch between our equations and what we see. The Higgs field fills all of space, and as the particles try to move through it, their interactions with it cause them to appear to have mass. This slows them down and allows them to bind together into the familiar forms of matter which we observe. This is a completely different picture of nature than the one we instinctively imagine – instead of matter having its own intrinsic properties, and moving about in empty space, many of the properties of matter are actually only due to its interactions with an invisible, all-pervasive field. The properties of "empty" space are crucial to the physicist's understanding of the world.
The Higgs boson itself is a vibration in the Higgs field, which can be created if enough energy is put into the field, like dropping a pebble into a pond. The LHC is the world's highest energy particle collider, and the collisions it makes create enough disturbance in the Higgs field to observe the Higgs boson, if it exists.
Why does it matter?
Professor Soldner-Rembold says:
Today's discovery teaches us something fundamental about the building blocks of the universe and how the fundamental particles that build the world around us acquire mass. The Higgs boson matters because it tell us about 'matter'. This is curiosity driven research and addresses basic questions about the evolution of the universe.
In addition, this curiosity driven research also leads to many important applications. It was exciting to see how today's seminar at Cern was broadcast via the world wide web to all continents, using the technology pioneered at Cern. Particle accelerators have many applications in material science and medicine.
The Higgs discovery pushes the boundary of modern physics and it will
take a while to understand what lies beyond the door we have opened today. No doubt there will be many more exciting discoveries coming out of Cern and the LHC in the next decade. | <urn:uuid:8ef17ef3-578d-41fa-8eb4-87f331209a97> | 2.734375 | 702 | Audio Transcript | Science & Tech. | 47.045779 |
It is probably safe to say that nobody has ever friended a cockroach on Facebook, but its will to survive isn’t dependant on social networking or welcome mats. The cockroach family (Blattidae) was prolific 350 million years ago and is found all over the world today. When we see a cockroach, it’s probably in someone’s home, but close to 4,000 species of cockroach don’t even want to live with humans.
Last week I mentioned the leaproach, a previously unknown species which to me is the most interesting one on this year’s list of newly-found life forms. It’s a South African cockroach, discovered by Mike Picker from the University of Capetown when he was looking for something else. It can leap 48 times its body length, while the other 4000 species of cockroaches don’t hop at all. The leaproach is a better jumper than the grasshopper, which jumps 20 body lengths, It has no wings to help with stability, though cockroaches are thought to have been the first flying animals. It does have specialized antenna sockets that make its shape more aerodynamic, and a joint that facilitates backwards motion at take-off. It also has bulging eyes that enable it to target its ‘landing strip".
The leaproach’s greatest assets are its enormous hind legs and a lump of resilin, an elastic protein, on its knees. The resilin works like an elastic band or a spring-loaded coil and stores the energy of the flexing leg muscles to give them a powerful boost for jumping. The leaproach’s rate of acceleration is 23 times greater than the earth’s gravity, which is 9.81 metres every second. The muscles of the leaproach’s femurs are one-fifth of its total body weight.
There is a name for the process of distantly related species, like grasshoppers and cockroaches, becoming similar over time when they share a habitat and have the same problems to solve. The term is convergent evolution. Both grasshoppers and cockroaches have to move through sedge grass and it is much easier to jump between stems ( or soar above them) than to scurry along the ground. However, it’s a mystery why other species of cockroach in the same environment haven’t also evolved as high jumpers. Like the leaproach, they have to find mates, forage for food and escape predators in grassy fields, but unlike the leaproach, they do it the hard way.
I wonder what wondrous creatures that we don’t know about yet will make it to next year’s Top 10. Entomologist, Quentin Wheeler at Arizona State University says that there are probably 10,000 unnamed, unclassified life-forms that we must study before we can understand the diversity and complexity of life on this planet. | <urn:uuid:bc2e491b-f0a6-401d-8d27-be4f12bba5f1> | 3.65625 | 611 | Nonfiction Writing | Science & Tech. | 52.847264 |
This section is different from the others. Most other sections of this document talks about a particular SQL command. This section does not talk about a standalone command but about "expressions" which are subcomponents of most other commands.
SQLite understands the following binary operators, in order from highest to lowest precedence:
|| * / % + - << >> & | < <= > >= = == != <> IS IS NOT IN LIKE GLOB MATCH REGEXP AND OR
Supported unary prefix operators are these:
- + ~ NOT
The COLLATE operator is a unary postfix operator that assigns a collating sequence to an expression. The COLLATE operator has a higher precedence (binds more tightly) than any prefix unary operator or any binary operator. The collating sequence set by the COLLATE operator overrides the collating sequence determined by the COLLATE clause in a table column definition. See the detailed discussion on collating sequences in the Datatype In SQLite3 document for additional information.
The unary operator + is a no-op. It can be applied to strings, numbers, blobs or NULL and it always returns a result with the same value as the operand.
Note that there are two variations of the equals and not equals operators. Equals can be either = or ==. The non-equals operator can be either != or <>. The || operator is "concatenate" - it joins together the two strings of its operands. The operator % outputs the value of its left operand modulo its right operand.
The result of any binary operator is either a numeric value or NULL, except for the || concatenation operator which always evaluates to either NULL or a text value.
The IS and IS NOT operators work like = and != except when one or both of the operands are NULL. In this case, if both operands are NULL, then the IS operator evaluates to 1 (true) and the IS NOT operator evaluates to 0 (false). If one operand is NULL and the other is not, then the IS operator evaluates to 0 (false) and the IS NOT operator is 1 (true). It is not possible for an IS or IS NOT expression to evaluate to NULL. Operators IS and IS NOT have the same precedence as =.
A literal value is a constant of some kind. Literal values may be integers, floating point numbers, strings, BLOBs, or NULLs.
The syntax for integer and floating point literals (collectively "numeric literals") is shown by the following diagram:
If a numeric literal has a decimal point or an exponentiation clause, then it is a floating point literal. Otherwise is it is an integer literal. The "E" character that begins the exponentiation clause of a floating point literal can be either upper or lower case. The "." character is always used as the decimal point even if the locale setting specifies "," for this role - the use of "," for the decimal point would result in syntactic ambiguity.
A string constant is formed by enclosing the string in single quotes ('). A single quote within the string can be encoded by putting two single quotes in a row - as in Pascal. C-style escapes using the backslash character are not supported because they are not standard SQL. BLOB literals are string literals containing hexadecimal data and preceded by a single "x" or "X" character. For example:
A literal value can also be the token "NULL".
A "variable" or "parameter" token specifies a placeholder in the expression for a value that is filled in at runtime using the sqlite3_bind() family of C/C++ interfaces. Parameters can take several forms:
?NNN A question mark followed by a number NNN holds a spot for the NNN-th parameter. NNN must be between 1 and SQLITE_MAX_VARIABLE_NUMBER. ? A question mark that is not followed by a number creates a parameter with a number one greater than the largest parameter number already assigned. If this means the parameter number is greater than SQLITE_MAX_VARIABLE_NUMBER, it is an error. :AAAA A colon followed by an identifier name holds a spot for a named parameter with the name :AAAA. Named parameters are also numbered. The number assigned is one greater than the largest parameter number already assigned. If this means the parameter would be assigned a number greater than SQLITE_MAX_VARIABLE_NUMBER, it is an error. To avoid confusion, it is best to avoid mixing named and numbered parameters. @AAAA An "at" sign works exactly like a colon, except that the name of the parameter created is @AAAA. $AAAA A dollar-sign followed by an identifier name also holds a spot for a named parameter with the name $AAAA. The identifier name in this case can include one or more occurrences of "::" and a suffix enclosed in "(...)" containing any text at all. This syntax is the form of a variable name in the Tcl programming language. The presence of this syntax results from the fact that SQLite is really a Tcl extension that has escaped into the wild.
Parameters that are not assigned values using sqlite3_bind() are treated as NULL.
The maximum parameter number is set at compile-time by the SQLITE_MAX_VARIABLE_NUMBER macro. An individual database connections D can reduce its maximum parameter number below the compile-time maximum using the sqlite3_limit(D, SQLITE_LIMIT_VARIABLE_NUMBER,...) interface.
The LIKE operator does a pattern matching comparison. The operand to the right of the LIKE operator contains the pattern and the left hand operand contains the string to match against the pattern. A percent symbol ("%") in the LIKE pattern matches any sequence of zero or more characters in the string. An underscore ("_") in the LIKE pattern matches any single character in the string. Any other character matches itself or its lower/upper case equivalent (i.e. case-insensitive matching). (A bug: SQLite only understands upper/lower case for ASCII characters by default. The LIKE operator is case sensitive by default for unicode characters that are beyond the ASCII range. For example, the expression 'a' LIKE 'A' is TRUE but 'æ' LIKE 'Æ' is FALSE.)
If the optional ESCAPE clause is present, then the expression following the ESCAPE keyword must evaluate to a string consisting of a single character. This character may be used in the LIKE pattern to include literal percent or underscore characters. The escape character followed by a percent symbol (%), underscore (_), or a second instance of the escape character itself matches a literal percent symbol, underscore, or a single escape character, respectively.
The LIKE operator can be made case sensitive using the case_sensitive_like pragma.
The GLOB operator is similar to LIKE but uses the Unix file globbing syntax for its wildcards. Also, GLOB is case sensitive, unlike LIKE. Both GLOB and LIKE may be preceded by the NOT keyword to invert the sense of the test. The infix GLOB operator is implemented by calling the function glob(Y,X) and can be modified by overriding that function.
The REGEXP operator is a special syntax for the regexp() user function. No regexp() user function is defined by default and so use of the REGEXP operator will normally result in an error message. If a application-defined SQL function named "regexp" is added at run-time, that function will be called in order to implement the REGEXP operator.
The MATCH operator is a special syntax for the match() application-defined function. The default match() function implementation raises an exception and is not really useful for anything. But extensions can override the match() function with more helpful logic.
The BETWEEN operator is logically equivalent to a pair of comparisons. "x BETWEEN y AND z" is equivalent to "x>=y AND x<=z" except that with BETWEEN, the x expression is only evaluated once. The precedence of the BETWEEN operator is the same as the precedence as operators == and != and LIKE and groups left to right.
A CASE expression serves a role similar to IF-THEN-ELSE in other programming languages.
The optional expression that occurs in between the CASE keyword and the first WHEN keyword is called the "base" expression. There are two basic forms of the CASE expression: those with a base expression and those without.
In a CASE without a base expression, each WHEN expression is evaluated and the result treated as a boolean, starting with the leftmost and continuing to the right. The result of the CASE expression is the evaluation of the THEN expression that corresponds to the first WHEN expression that evaluates to true. Or, if none of the WHEN expressions evaluate to true, the result of evaluating the ELSE expression, if any. If there is no ELSE expression and none of the WHEN expressions are true, then the overall result is NULL.
A NULL result is considered untrue when evaluating WHEN terms.
In a CASE with a base expression, the base expression is evaluated just once and the result is compared against the evaluation of each WHEN expression from left to right. The result of the CASE expression is the evaluation of the THEN expression that corresponds to the first WHEN expression for which the comparison is true. Or, if none of the WHEN expressions evaluate to a value equal to the base expression, the result of evaluating the ELSE expression, if any. If there is no ELSE expression and none of the WHEN expressions produce a result equal to the base expression, the overall result is NULL.
When comparing a base expression against a WHEN expression, the same collating sequence, affinity, and NULL-handling rules apply as if the base expression and WHEN expression are respectively the left- and right-hand operands of an = operator.If the base expression is NULL then the result of the CASE is always the result of evaluating the ELSE expression if it exists, or NULL if it does not.
Both forms of the CASE expression use lazy, or short-circuit, evaluation.
The only difference between the following two CASE expressions is that the x expression is evaluated exactly once in the first example but might be evaluated multiple times in the second:
The IN and NOT IN operators take a single scalar operand on the left and a vector operand on the right formed by an explicit list of zero or more scalars or by a single subquery. When the right operand of an IN or NOT IN operator is a subquery, the subquery must have a single result column. When the right operand is an empty set, the result of IN is false and the result of NOT IN is true, regardless of the left operand and even if the left operand is NULL. The result of an IN or NOT IN operator is determined by the following matrix:
|Left operand |
|Right operand |
|Right operand |
is an empty set
|Left operand found |
within right operand
|Result of |
|Result of |
NOT IN operator
|does not matter||no||yes||no||false||true|
|no||does not matter||no||yes||true||false|
|yes||does not matter||no||does not matter||NULL||NULL|
Note that SQLite allows the parenthesized list of scalar values on the right-hand side of an IN or NOT IN operator to be an empty list but most other SQL database database engines and the SQL92 standard require the list to contain at least one element.
The EXISTS operator always evaluates to one of the integer values 0 and 1. If executing the SELECT statement specified as the right-hand operand of the EXISTS operator would return one or more rows, then the EXISTS operator evaluates to 1. If executing the SELECT would return no rows at all, then the EXISTS operator evaluates to 0.
The number of columns in each row returned by the SELECT statement (if any) and the specific values returned have no effect on the results of the EXISTS operator. In particular, rows containing NULL values are not handled any differently from rows without NULL values.
A SELECT statement enclosed in parentheses may appear as a scalar quantity. A SELECT used as a scalar quantity must return a result set with a single column. The result of the expression is the value of the only column in the first row returned by the SELECT statement. If the SELECT yields more than one result row, all rows after the first are ignored. If the SELECT yields no rows, then the value of the expression is NULL. The LIMIT of a scalar subquery is always 1. Any other LIMIT value given in the SQL text is ignored.
All types of SELECT statement, including aggregate and compound SELECT queries (queries with keywords like UNION or EXCEPT) are allowed as scalar subqueries.
A column name can be any of the names defined in the CREATE TABLE statement or one of the following special identifiers: "ROWID", "OID", or "_ROWID_". These special identifiers all describe the unique integer key (the rowid) associated with every row of every table. The special identifiers only refer to the row key if the CREATE TABLE statement does not define a real column with the same name. The rowid can be used anywhere a regular column can be used.
A SELECT statement used as either a scalar subquery or as the right-hand operand of an IN, NOT IN or EXISTS expression may contain references to columns in the outer query. Such a subquery is known as a correlated subquery. A correlated subquery is reevaluated each time its result is required. An uncorrelated subquery is evaluated only once and the result reused as necessary.
A CAST expression is used to convert the value of <expr> to a different storage class in a similar way to the conversion that takes place when a column affinity is applied to a value. Application of a CAST expression is different to application of a column affinity, as with a CAST expression the storage class conversion is forced even if it is lossy and irrreversible.
If the value of <expr> is NULL, then the result of the CAST expression is also NULL. Otherwise, the storage class of the result value is determined by applying the rules for determining column affinity to the <type-name> specified as part of the CAST expression.
|Affinity of <type-name>||Conversion Processing|
|NONE||Casting a value to a <type-name> with no affinity causes the value to be converted into a BLOB. Casting to a BLOB consists of first casting the value to TEXT in the encoding of the database connection, then interpreting the resulting byte sequence as a BLOB instead of as TEXT.|
|TEXT||To cast a BLOB value to TEXT, the sequence of bytes that make up the BLOB is interpreted as text encoded using the database encoding.|
|REAL|| When casting a BLOB value to a REAL, the value is first converted to
When casting a TEXT value to REAL, the longest possible prefix of the value that can be interpreted as a real number is extracted from the TEXT value and the remainder ignored. Any leading spaces in the TEXT value are ignored when converging from TEXT to REAL. If there is no prefix that can be interpreted as a real number, the result of the conversion is 0.0.
|INTEGER|| When casting a BLOB value to INTEGER, the value is first converted to
When casting a TEXT value to INTEGER, the longest possible prefix of the value that can be interpreted as an integer number is extracted from the TEXT value and the remainder ignored. Any leading spaces in the TEXT value when converting from TEXT to INTEGER are ignored. If there is no prefix that can be interpreted as an integer number, the result of the conversion is 0.
A cast of a REAL value into an INTEGER will truncate the fractional part of the REAL. If a REAL is too large to be represented as an INTEGER then the result of the cast is the largest negative integer: -9223372036854775808.
|NUMERIC|| Casting a TEXT or BLOB value into NUMERIC first does a forced
conversion into REAL but then further converts the result into INTEGER if
and only if the conversion from REAL to INTEGER is lossless and reversible.
This is the only context in SQLite where the NUMERIC and INTEGER affinities
Casting a REAL or INTEGER value to NUMERIC is a no-op, even if a real value could be losslessly converted to an integer.
Note that the result from casting any non-BLOB value into a BLOB and the result from casting any BLOB value into a non-BLOB value may be different depending on whether the database encoding is UTF-8, UTF-16be, or UTF-16le.
The SQL language features several contexts where an expression is evaluated and the result converted to a boolean (true or false) value. These contexts are:
To convert the results of an SQL expression to a boolean value, SQLite first casts the result to a NUMERIC value in the same way as a CAST expression. A NULL or zero value (integer value 0 or real value 0.0) is considered to be false. All other values are considered true.
For example, the values NULL, 0.0, 0, 'english' and '0' are all considered to be false. Values 1, 1.0, 0.1, -0.1 and '1english' are considered to be true.
Both simple and aggregate functions are supported. (For presentation purposes, simple functions are further subdivided into core functions and date-time functions.) A simple function can be used in any expression. Simple functions return a result immediately based on their inputs. Aggregate functions may only be used in a SELECT statement. Aggregate functions compute their result across all rows of the result set. | <urn:uuid:c8f5bfce-2845-476a-84ac-7411a0dc4082> | 3.125 | 3,811 | Documentation | Software Dev. | 44.22742 |
1. The Living Machine
Plate tectonics, one of the most important discoveries of the 20th century, is explored at such
sites as the erupting Kilauea volcano and the bottom of the Atlantic Ocean in the submersible
2. The Blue Planet
Perhaps the last great unexplored frontier on earth, the oceans reveal major new revelations as
detected by scientists aboard the space shuttle and submerged to the depths of the "middle ocean"
to view rare life forms.
3. The Climate Puzzle
Scientists piece together an unfolding mystery — what caused the ice ages, how Venus's
greenhouse effect may have parallels on earth, and what Antarctica's eerie ice rivers demonstrate.
4. Tales From Other Worlds
Through little-seen footage shot in space and special effects, visit the great failed star of Jupiter,
probe the raging volcano of Io, and peer through acid rain clouds to see the surface of Venus for
the first time.
5. Gifts From the Earth
By examining the earth's mineral and energy sources, scientists analyze how the theory of plate
tectonics has revolutionized the search for earth's treasures that lie hidden in locations such as the
Red Sea and Antarctic ice cap.
6. The Solar Sea
Geologists investigate an 800-million-year-old rock record of sun activity in an ancient
Australian lake bed, and fabulous ground and satellite photography of the aurora borealis all
contribute to an understanding of earth's relationship to the yellow dwarf star we know as the
7. Fate of the Earth
New theories about the global consequences of a "nuclear winter" and an "ultra-violet spring" are
revealed in this final episode that explores the role of life in shaping earth and its future. | <urn:uuid:af6d8a51-521b-4ce1-9935-03977cd9d88e> | 3.21875 | 367 | Content Listing | Science & Tech. | 44.103487 |
Variable Manipulation and Output03/22/2001
This article will conclude our discussion of variables in PHP by presenting the numerous ways that atomic PHP variables can be manipulated and accessed within PHP scripts. We'll also look at the
echo command and use it to create our first PHP script that truly outputs dynamic content to the user.
Now that we have a better idea of the types of variables in PHP and are familiar with how to use them, we will begin discussing how these variables can interact and be manipulated. As with our introduction to the types of variables in PHP, we will begin with the mathematical operators.
Basic mathematics in PHP
To begin our introduction into variable manipulation, we will start with the basic mathematical abilities of PHP using standard integer variables. For the most part, the syntax and logic in this section is straightforward and will only be covered briefly to clarify any confusion that may exist. Consider the following:
<?php $number = 10; $foo = 2; $answer = $number + $foo; ?>
This is an example of a basic mathematical operation between two integers in PHP. As expected, the variable
$number is added to the variable
$foo with the sum of these two numbers (10 + 2 = 12) being stored in the variable
$answer. Now, what if we wanted to subtract
$answer by another number such as 5 (assume
$answer is 12)?
<? // Assume $answer exists and is equal to // $number + $foo (10 + 2 = 12) $answer = $answer - 5; ?>
In this example, we are taking our previous value
$answer, and subtracting it by the constant value 5 and then storing the resulting number back into the variable
$answer. For those who have no programming experience, this example can be quite confusing! How can you take a variable, subtract it by another number and store the answer to that variable into the same variable you just used in your subtraction? The answer is that PHP will always evaluate a statement before any assignments are made -- that is, PHP will use the old value of
$answer to do the mathematics before replacing it with the new value. Therefore, the value of answer should be 12 - 5 = 7, and it is!
The situation presented above -- where a variable is used in a mathematical statement and the result of the statement is stored back into the variable used originally -- is very common. Usually, the mathematical tasks performed in an application are very simple and, to make such tasks easier, the following statements are all allowed in PHP:
<?php // Add 1 to the value of $answer $answer++; // Subtract 1 from the value of $answer $answer--; // Add 5 to the value of $answer $answer += 5; ?>
PHP also allows the use of parentheses within mathematical statements. An example:
<?php // Performing Multiple Operations with Parentheses $answer = (5*(4+2))/2 // Answer = ((4 + 2) * 5)/2 = 30 // = 30/2 = 15 ?>
As mentioned in my previous article, floating-point numbers may not always store and return the values as expected. For example, a floating-point statement that evaluates to the value 7.99999999 may be perceived as the value 7 on some systems when converted to an integer rather than the expected value of 8. For more information regarding the particulars of this on your specific system consult the PHP manual. Beyond the special consideration that must be taken when dealing with floating-point numbers, they conform to all of the same mathematical syntax as their integer counterparts.
When dealing with strings, it is often necessary to manipulate them in a number of ways. PHP provides a small army of string manipulation functions that provide tools for nearly every circumstance. (A list of these functions can be found online at the PHP web site.) Although the majority of string manipulation is done through function calls, there is a syntax that is worth discussion. When dealing with strings, it is sometimes useful if not necessary to take two strings and combine them head-to-tail into a single string. To do this, we use the period operator (".") to combine strings just as we used a math operator (such as addition). Example:
<?php // Assign $foo a string value $foo = "Hello, my name is: "; // Assign $name another String Value $name = "John"; // Attach $name to the end of $foo and store in // the variable $message $message = $foo . $name; ?>
Also note that the period operator can be used in a syntax similar to the one illustrated in the integer examples:
<?php // Assign $bar a value $bar = "Hello,"; // Add on to $bar $bar .= " my "; $bar .= " name "; $bar .= " is "; $bar .= " John "; ?>
As expected, the resulting value of
$bar will be "Hello, my name is John".
Pages: 1, 2 | <urn:uuid:a91b7762-e325-484a-a4d5-fd4ccd8551f8> | 3.921875 | 1,053 | Truncated | Software Dev. | 53.634071 |
On March 23 MESSENGER reached the one-billion mile mark, placing the spacecraft about one-fifth of the way toward its destination to orbit Mercury. On that same day, in the early morning hours (UTC), the spacecraft's distance from the Sun was about the same as the Earth's distance to the Sun. "One billion miles and the team and spacecraft are doing well," says Mission Operations Manager Mark Holdridge of the Johns Hopkins Applied Physics Laboratory (APL), where the spacecraft is operated and where it was designed and built.
The MESSENGER spacecraft performed its final "flop" maneuver for the mission on March 8, pointing the back side of the spacecraft to the Sun until June 2006. This rotation about the X-axis is performed whenever the solar distance increases beyond approximately 0.95 astronomical units (AU), nearly the distance between the Earth and the Sun. At this distance, the solar arrays do not generate enough power to operate all spacecraft components simultaneously, including instruments and heaters. The "flop" is performed to heat the back side of the spacecraft with the Sun. A "flip" maneuver reverses the effect of the "flop" maneuver by pointing the sunshade toward the Sun. This solar heating reduces the need for multiple onboard heaters, providing the necessary power until the spacecraft is closer to the Sun again. Previous flip, flop, and flip maneuvers were performed on March 8, 2005, June 14, 2005, and September 7, 2005. The spacecraft is scheduled to flip back toward the Sun on June 21.
Even though the MESSENGER spacecraft is years away from entering its final destination of orbiting Mercury, the mission Science Team is already very busy collecting scientific data and sharing it with the larger scientific community. Those plans and results are now available on the team's new Web site: http://messenger.jhuapl.edu/soc/index.html.
For a complete look at MESSENGER's journey through the inner solar system, visit the Mission Design section of the Web site at http://messenger.jhuapl.edu/the_mission/mission_design.html.
To see where MESSENGER is now, visit http://messenger.jhuapl.edu/whereis/index.php.
More: NASA -Status Report on MESSENGER | <urn:uuid:7e2b5864-569b-4a52-9a95-6084c4c991ef> | 3.5 | 482 | Knowledge Article | Science & Tech. | 52.506378 |
As Grist puts it, contrary to popular belief, the U.S. is making progress on climate change. Overall, the country’s carbon emissions fell 1.7 percent last year—in part because of the explosive growth of natural gas and the Great Recession. Looking at energy-related carbon emissions in the last five years, the U.S. has experienced a roughly 6 percent drop. In fact, total greenhouse gas emissions are not expected to reach 2010 levels again until 2030, according to the U.S. Energy Information Administration.
That doesn’t mean everyone is concerned about its progress. Generation X—individuals ranging from 32 to 52—may not be the stereotypical slackers they are often portrayed to be, but most are not extremely worried about climate change, according to a new poll. Only about 20 percent said they were highly concerned, while 42 percent were moderately concerned about climate change. The remaining 37 percent showed less concern or none at all. That said, when looking at the population as a whole, there is a “substantial” increase in the number of Americans concerned with the issue, according to a study comparing various opinion polls.
One technology intended to artificially cool the planet and combat climate change, may actually make climate conditions worse. Four separate climate models used by a group of scientists to test the concept of geoengineering—where an increase in the world’s atmospheric carbon dioxide levels was balanced by a “dimming” of the sun—showed undesirable climate effects, including a reduction in global rainfall. One map suggests many of these projects are already under way across the world—with one new field test proposed by Harvard researchers that would combine sulfate particles with water vapor to form aerosols to reflect the sun’s rays. “The time has come to differentiate: some geoengineering techniques are more dangerous than others,” said Victor Smetacek of the Alfred Wegener Institute for Polar and Marine Research in Germany. His team recently came out with a study that looks at dumping iron into the sea to bury carbon dioxide for centuries, potentially reducing the impact of climate change.
Temperatures, Drought Threaten Resources
Drought conditions, now gripping much of the country, have led the U.S. Department of Agriculture to declare natural disasters in more than 1,000 counties in 26 states. Labeled the sixth most severe drought in the United States since record keeping began in 1895, the heat and lack of rain is taking a heavy toll on crops—especially in key corn growing states in the Midwest—raising food and fuel prices. A map by the National Climatic Data Center illustrating the subtraction of precipitation and potential evapotranspiration in June attempts to show why. Even if there had been normal precipitation amounts, it would not have been enough to meet potential evapotranspiration demand in most areas, says Climate Central’s Andrew Freedman.
An iceberg twice the size of Manhattan broke off a Greenland glacier this week. In addition, the Arctic lost in June about 1.1 million square miles of ice, a record. That’s nearly equivalent to the area of Alaska, Florida, Texas and California combined. The rapid retreat of snow and ice has sparked interest in the Arctic’s undiscovered oil and gas reserves. Shell already has plans to begin exploratory drilling in the area as early as this summer if permits arrive as projected. Proponents say if Shell finds oil, thousands of jobs could be created, while others voice concern over the possibility of spills and marine pollution. Regardless, the pace of widespread drilling in the region remains uncertain.
Countries Reconsider Nuclear
Following Japan’s Fukushima nuclear disaster a year ago, Germany opted to shut down all of its nuclear plants by 2022. The plan was to expand its current renewable energy portfolio—which makes up about 20 percent of the energy mix—to 35 percent by 2020 and 80 percent in 2050. Those targets may be less likely and could be readjusted if jobs are threatened. “The timeframe and the goals of the energy revolution are intact,” said Economy Minister Philipp Rösler. “But we will have to make adjustments if jobs and our competitiveness should become endangered.”
Meanwhile, Japan, which ordered all nuclear power plants shut down for inspection after Fukushima, will restart a second reactor to handle energy demand. The decision has prompted protests as Japan considers three energy options as it moves forward—reduce nuclear power to zero as soon as it can, decrease it to 15 percent by 2030 or aim for a 20-25 percent share by 2030.
The Climate Post offers a rundown of the week in climate and energy news. It is produced each Thursday by Duke University’s Nicholas Institute for Environmental Policy Solutions. | <urn:uuid:965d121f-1fc1-4012-878a-7e5ac290ad1e> | 3.328125 | 977 | Content Listing | Science & Tech. | 41.95883 |
Department Sustainability, Environment, Water, Population and Communities - November 2010
The Snowy River is naturally fast flowing, with its headwaters running from Mount Kosciuszko, Australia's highest peak.
However, regulation of the river has reduced flows to less than one per cent of the original volume.
The dwindling flows have left sediment to build up over the riverbed and smother habitat for aquatic plants and animals.
The Australian, New South Wales and Victorian governments are working to restore the river's mighty flows and the aquatic habitats they support.
Snowy River environmental watering facts:
- In 2002 the Australian, New South Wales and Victorian Government signed an historic agreement that set a target of returning 21 per cent of the Snowy River's natural flow by 2012.
- Since 2002, 251 billion litres have been released as environmental flow from storages along the Snowy River.
- In the 2010/11 water year, 71 billion litres of environmental water will be released to the Snowy River.
- Over 10 days in November 2010, almost 17 billion litres of water was released from Jindabyne Dam - the largest controlled environmental water release to the Snowy River since the dam's construction in 1967. This will be followed up in April 2011 with a further water release of almost seven billion litres.
- The November 2010 release simulates the Snowy River's naturally high spring flow events, caused by snowmelt running off the mountains at the river's headwaters. The intense spring flows dislodge sediment build up from the river bed.
- The Australian, New South Wales and Victorian governments have also committed to repaying the Mowamba Borrowing Account. The Mowamba Borrowing Account represents water that was borrowed from other users of the Snowy Scheme to provide for environmental flows to the Snowy River between 2002 and 2006.
- The repayment of the Mowamba Borrowing Account, along with increased seasonal water allocations, will result in a significant increase in the amount of water available to the Snowy River into the future.
A spectacular surge of river water is set free of its dam enclosure ... it's the largest release the thirsty stretch of the Snowy River below has seen for more than 40 years.
With the regulation of the river, flows dwindled, leaving sediment to build up over the riverbed and smother habitat for aquatic plants and animals.
The Australian, New South Wales and Victorian governments are working to restore the Snowy River's mighty flows and the aquatic habitats they support downstream.
The recent release of almost 17 billion litres of water over 10 days will dislodge sediment from the river bed and flush out algal growths left to thrive in stagnant pools.
The release will be followed by a further release of almost seven billion litres in April 2011.
Thanks to an agreement between the three governments, water cascading from Jindabyne Dam wall will be a feature of the Snowy River for years to come. | <urn:uuid:e6030bed-1da2-4218-a0b9-d0fb0cd45efa> | 3.96875 | 608 | Knowledge Article | Science & Tech. | 41.524523 |
Brief SummaryRead full entry
North American Ecology (US and Canada)Poanes hobomok is a year-round resident across most of the eastern United States and southeastern Canada, with separate populations in Colorado and New Mexico (Scott 1986). Habitats are wooded areas. Host plants are grasses especially from two genera: Panicum, Poa. Eggs are laid on or near the host plant singly. There is one flight each year with the approximate flight time mostly June 1-early July in the northern part of the range and late Apr.-May 31 in the southern part of their range (Scott 1986). | <urn:uuid:8689fdfd-c82b-44df-ae54-5b04635091a4> | 2.890625 | 126 | Knowledge Article | Science & Tech. | 49.544422 |
It's hard to imagine an organism much simpler than the hydra. It doesn't have brains, hearts, or eyes - it's basically just tentacles with a mouth attached. And yet these simple creatures pull of biological feats no other animal can.
Hydra are one of a few species - flatworms are another recently discussed example - that can regenerate their body parts, seemingly indefinitely. They also possess a surprisingly complex weapon system known as cnidocytes, which enable their tentacles to shoot powerful neurotoxins into their enemies. What's interesting is that these attacks seem to be connected to light levels, and yet hydra don't just lack eyes - they don't even have a visual system at all. And yet they hunt on a clear night-day cycle and have been observed moving in response to sudden changes in light.
To get around the minor impediment of not having any eyes, the hydra have developed a unique way to see the world. Back in 2010, genomic researchers discovered hydra contained the genetic material needed to build opsins, which are photosensitive proteins found in all animals that possess sight. Usually, of course, these opsins are connected to the eyes, but in the case of hydra, these proteins are found clustered on the creature's tentacles and around the mouth.
These proteins then form part of a surprisingly complex system that connects it to neurons and, in turn, to the cnidocytes. This means the hydra, without any brain, eyes, or any sort of central system to coordinate its actions, is able to respond to light by activating its natural weapons system.
A team led by UC Santa Barbara researcher David Plachetzki made the find, and he thinks the proteins don't just help keep the hydra on the correct night-day cycle. He suspects it's also precise enough to respond to sudden shadows and other quick light changes, allowing the hydra to detect and strike any prey that wanders into its field of non-vision. In a statement, Plachetzki explains just how complicated this system is:
"Not only did we find opsin in the sensory neurons that connect to cnidocytes in the hydra, but we also found other components of phototransduction in these cells. These included cyclic nucleotide gated ion channels (CNG) required to transfer the signal and a hydra version of arrestin, which wipes the phototransduction slate clean for a second signal. We were also able to demonstrate that cnidocyte firing itself is affected by the light environment and that these effects are reversed when components of the phototransduction cascade are turned off."
For more, check out Scientific American for a more comprehensive overview on the remarkable abilities of hydra. | <urn:uuid:98467857-f679-4c7e-abb1-34894dc4f5a8> | 3.21875 | 552 | Truncated | Science & Tech. | 38.129752 |
Thank you in advance. please if possible, explain for me, so i can solve other problems by myself
So, taking the first of your questions:
"How many bit strings of length 10 have exactly three 0s?"
is equivalent to asking: in how many ways can I make a set of 3 positions out of 10? (the positions being the positions in the bit string where the 0s occur - the other 7 positions then have 1s).
Can you answer that question?
Hint: Combinations; Binomium of Newton. | <urn:uuid:12c4d715-0279-436b-8a79-065cf83cd8a5> | 3.234375 | 113 | Q&A Forum | Science & Tech. | 73.020539 |
First, you must break up the south-of-east force into its components. You can do this using trig.
From here you add the x-componet of the south-of-east force to the eastern force to get a force in the x direction of 1.1204. Because F=ma, the acceleration in a given direction is F/m. So, the acceleration in the x and y directions are as follows:
You then plug this into your postion functions (a/2)t^2 + vt + x to determine position:
x-position: .4482(3)^2 + .11(3) = 4.3638
y-position: .06389(3)^2 = .575
From here, you use the pythagorean theorem to determine magnitude of displacement:
Sqrt[4.3638^2 + .575^2] = 4.4015 meters
You can then use any number of various trig operations to find the angle:
theta = 7.506 degrees south of east
I'm sorry I couldn't give you any vector diagrams. Hopefully you can figure it out. (Double check the math as well). | <urn:uuid:64e7e1c8-9fbe-4829-b40c-4b6fa351de4c> | 3.09375 | 253 | Q&A Forum | Science & Tech. | 90.55084 |
|A Front Row Seat to the Universe|
magine seeing stars and planets as if they were just outside your living room window. From this window seat to the universe, you could see the birth and death of stars and galaxies as they appeared billions of years ago. The Hubble Space Telescope is your window seat to the universe. Hubble has provided us with front row seats to fragments of a comet slamming into Jupiter and stars being born in huge craggy towers of cold dark gas.
Deployed April 25, 1990 from the space shuttle Discovery, Hubble is one of the largest and most complex satellites ever built. Hubbles deployment culminated more than 20 years of research by NASA and other scientists. The telescope is named for American astronomer Edwin P. Hubble, who first discovered that countless island cities of stars and galaxies dwell far beyond our Milky Way.
But NASA didnt launch the telescope into space to get closer to the stars. Hubble barely skims the Earths atmosphere, orbiting just 380 miles above our planet. The nearest star, our sun, is 258,000 times farther away.
Hubble is in space because it can see the universe more clearly than we can from Earth. Looking at the heavens through a ground-based telescope is like trying to identify someone at poolside from the bottom of a swimming pool. Our vision is blurred. Thats because we live at the bottom of the Earths atmosphere, an ocean of air that smears and scatters starlight. Thats why stars twinkle.
Scientists have known for several years that our atmosphere obscures and distorts light. The scientists who pioneered rocketry decades ago concluded that the best view of the universe is from above the Earths atmosphere.
With Hubble, astronomers are getting a clearer picture of the universe. The telescopes stunning photos are showing the world about the wonders of space. Many of the worlds foremost astronomers are using Hubble to probe the horizons of space and time. Designed to last 15 years, Hubble is providing intriguing new clues to monster black holes, the birth of galaxies, and planetary systems around stars.
To provide astronomers with the latest Hubble data, the Earth-circling observatory must be maintained by hundreds of scientists, engineers, and computer programmers at the Space Telescope Science Institute in Baltimore, MD and the Goddard Space Flight Center in Greenbelt, MD.
Previous Topic | Index | Next Topic | <urn:uuid:dab3651d-cdec-49df-ab33-86333f12f564> | 3.28125 | 480 | Knowledge Article | Science & Tech. | 49.169826 |
A large, cicular plain.
A planetary surface that has been modified little since its formation typically featuring large numbers of impact craters (compare to young).
A theory, now widely accepted, that the Sun is surrounded by a distant cloud of comet-stuff, now called the Oort Cloud, bits of which are occasionally hurled into the solar system as comets.
A superior planet is said to be "in opposition" when it is directly on the opposite side of the Earth from the Sun. This is generally the closest it comes to the Earth and the time at which it is most easily visible. (e.g. when Mars, Earth and the Sun are located along a straight line, Mars is in opposition as seen from Earth.) Nice diagram.
An increase in brightness as an observer approaches the line between the sun and a target. The strength of the surge is an indicator of small-scale surface texture.
The path followed by an object in space as it goes around another object.
The time required for an object to make a complete revolution along its orbit.
A relationship in which the orbital period of one body is related to that of another by a simple integer fraction.
Complex chemical compounds that contain carbon.
Shaped like an egg.
A colorless and odorless gas that is needed by people and animals to live. | <urn:uuid:b4b7f349-e3b9-4ee2-b05d-a773e91bdd03> | 3.53125 | 277 | Structured Data | Science & Tech. | 53.706269 |
From the F# specification.
Reference manual page.
F# Power Pack. (Source code file q.fs in the math section as of this posting.)
Basically, user-defined numeric literals allow a programmer to define a new numeric type based on suffix of a literal -- similar to built-in numeric literals. (For example, instances of the built-in numeric literal type uint32 can be written as: “42u.”)
User-defined numeric literals allow the definition of new types by replacing the suffix (“u” in the uint32 example), with any of the characters Q, R, Z, I, N, or G. For example, you could write something that looks like this:
let x = 425Q
The programmer supplies a module that determines how the literals are interpreted. The name of the module must be “NumericLiteral,” followed by the suffix it controls (e.g. “NumericLiteralG”). This module must define several functions that determine how numbers of various lengths are handled. You can read about the details in the sources above, but there are five main functions:
FromZero – Called when a zero is encountered (e.g. 0Q).
FromOne – Called when a one is encountered.
FromInt32 – Numbers from 2 to Int32.MaxValue.
FromInt64 – Numbers from Int32.MaxValue+1 to Int64.MaxValue.
FromString – Even bigger numbers.
The “smallest” function that can process a number is the one that is called, and a function must exist for the proper range. For instance, if you write “42Q,” a FromInt32 function must exist, and it is the one called.
Here is a more complete example. It allows for numeric literals which translate binary representations into uint32. This is not particularly useful, since F# already defines the 0b* binary literal form, but it will do as a sample. (And as always, the code and information here are presented "as-is" and without warranty or implied fitness of any kind; use at your own risk.)
/// Numeric literal module for 32-bit unsigned
/// binary numbers.
module NumericLiteralZ =
let inline FromZero() = 0u
let inline FromOne() = 1u
let inline FromString (s:string) =
let rec f (acc:uint32) i (s:string) =
match i>=s.Length with
| true -> acc
| _ ->
match s.[i] with
| '0' -> f (acc*2u) (i+1) s
| '1' -> f (acc*2u+1u) (i+1)s
| _ -> failwith "Non-binary digit."
f 0u 0 s
let inline FromInt32 (n:int) =
let inline FromInt64 (n:int64) =
let n0 = 0Z
let n4 = 0000100Z
let n5 = 101Z
let nMax = 11111111111111111111111111111111Z
// For reference purposes, here is the
// existing binary syntax; use it in the
// real world instead of my class above.
let n37 = 0b100101u
printfn "Your breakpoint here."
But I think this is the sort of thing that must be used with some caution. With only six suffixes available (Q, R, Z, I, N, and G), the potential for collision is high. Also, since this is an uncommon language feature, it is likely to confuse many users who encounter it for the first time. | <urn:uuid:a93dfcf6-ba7c-4535-b0e7-ee5cf38fe61a> | 3.3125 | 797 | Documentation | Software Dev. | 63.092822 |
not only brings national attention
to the Department of Forestry's
work in developing
sound stewardship practices,
but it also focuses attention
on the important
small animals play
in the life of
the planet's forests.
Timber companies will ultimately use
the study's findings to better manage
harvesting procedures in order to safeguard
the endangered bats.
Graduate student Dan Cox assists Mike Lacki as he investigates a bat in Robinson Forest.
. . . . . . . . . . . . . . .
Has a Story
In 1992, Michael Baker '93, '96 hadn't yet decided what he wanted to do with his life. He was working at UPS to make ends meet while he took his time getting through undergraduate school, dabbling with different majors, trying to find his way. But a field trip to the Daniel Boone National Forest was about to change all that.
It was a late Friday night in early fall. Mike Lacki's class had just finished stringing mist nets to capture bats. Baker, waiting in the dark surrounded by much younger classmates, was thinking, "What am I doing here? I should be seeing some loud band in downtown Lexington."
Not long after, he had his answer. Watching Lacki handle a bat and point out the various parts, Baker was suddenly fascinated and thought, "There's a job. That's a cool job!"
Much later, during the hike out of the forest, Lacki suddenly came up behind him, clapped a hand on his student's shoulder and asked, "So what's your story, Baker?"
"I hadn't thought that I had a story at that point," Baker remembered years later.
That deep woods conversation was the start of a long, professional relationship between professor and student. Baker left UPS and took a job as a student worker in the department while he worked on his bachelor's and master's degrees in forestry.
Today, Michael Baker, with a doctorate in wildlife and fisheries science from Louisiana State University, is back at UK as a post-doctoral scholar. He is working with Lacki to study the importance of tree roosts for the ecology of bats in the Pacific Northwest.
Big Brown Bat
Turning Bat Notions
by Carol L. Spence
The woods ring with the sound of birds settling in for the night. A moist, humus-y smell rises from the forest floor. As the horizon cools, night creatures begin to stir—owls, moths, bats. And Mike Lacki.
Just as moths attract bats, bats have drawn the University of Kentucky forestry professor to nocturnal forests from Kentucky to the Pacific Northwest. To Lacki, the night isn’t filled with the fearsome animals, shadows, and strange sounds that so many people dread. Lacki, like his bats, has found his niche in the forest’s night.
“Being in the woods at night is awesome,” said Lacki, a professor of wildlife ecology and management. “All the encounters that you run into with wildlife that never happen in the daytime—you just turn the corner and boom, there’s something right there.”
For nearly three decades, Lacki has focused his research on an animal that makes most people shiver and shriek. But for him that was part of the allure. As a master's degree candidate in zoology at The Ohio State University, Lacki agreed to work on a bat study that no one else wanted.
"Why would nobody want to do that? I don't understand that," he said, shaking his head. He quickly found that familiarity breeds fascination and respect. As he saw it, others were missing out on the opportunity to learn about an enthralling and misunderstood creature.
"It's different everywhere in the world, how people view bats. Some cultures view them positively; some do not. And of course, the media and TV and movie industries certainly created an image of bats that the majority of people probably don’t view as positive. So from that standpoint, I feel like it's far more important from a conservation point of view to perhaps help out a group of animals like that."
Lacki belies the notion that a scientist needs to maintain a cold detached approach to his subject. He is fervent in his respect and affection for bats. "After you work with them for a number of years you begin to realize a couple of things," he said. "For their size they are tremendously smart. I mean, the ability to echolocate alone is mind-boggling when you think about it," he said, referring to the sonar-like ability used by bats to forage for food and navigate.
While echolocation may be bats' most familiar ability, their other communication skills are still being discovered.
"It's becoming more and more apparent that we are just barely scratching the surface in terms of how much communication actually takes place," said Lacki. "They may be able to transfer information to each other about where to go to feed. And the whole mother-pup interaction is very extensive. I mean all you have to do is be able to sit outside the entrance of a cave that has a maternity site and listen, and you'll be amazed at what you hear. It's a whole range of audible calls."
Lacki is particularly enthusiastic about Rafinesque's big-eared bats, an isolated colony of which lives in UK's Robinson Forest. In every state in which they appear, they are considered either endangered, threatened, or, as they are in Kentucky, of special concern. "The colony of Rafs kind of makes the forest special for me, because it's just neat that we've got something like that here," he said.
Rafinesque's Big-Eared Bat
Lacki has been tracking the Robinson Forest colony of Rafinesque's big-eared bats since it was discovered in 1996. Because of his long-term relationship with the animals, he's gained a familiarity with them and a high regard for their intelligence.
"I know that some of those individual bats know who I am because they've seen me so many times. To me, that's kind of neat," he said. "So you gain kind of camaraderie. Maybe it's not really camaraderie, but a connection to something that you've worked with for so long. Many of them have seen you come and go many times, and they know that you're OK and that you're not going to try to do anything to them. Whereas other people who enter"—and here he snaps his fingers—"they’re going to jump and leave."
Lacki, who earned his doctorate in zoology from North Carolina State University, came to UK in 1989 and "walked right into a study on the endangered Virginia big-eared bat in the Daniel Boone (National Forest)." He remembers it as a "time when everyone was just beginning to try to track bats and to study bats as they forage across landscapes." Since then, he's made his name as a renowned field researcher, with projects that stretch across the United States. He is in the sixth and final year of a roost density study in the Pacific Northwest. Timber companies will ultimately use the study's findings to manage harvesting procedures in order to safeguard bats.
Currently, Lacki is involved with two projects in Kentucky and surrounding states. One seeks to understand the effects of fire on maternal colonies of bats. The other study, covering seven forest locations across four states, is designed to evaluate the implications for bats under different timber cutting practices.
Lacki's research not only brings national attention to the Department of Forestry's work in developing sound stewardship practices, but it also focuses attention on the important ecological role small animals play in the life of the planet's forests. As part of the food chain, bats help control destructive insect populations, serve as a food source for other predators, and fertilize the soil with their fecal matter (guano), making the whole area richer for vegetation—vegetation that is vital in cleansing the atmosphere.
To Mike Lacki, protecting "the little guys," as he calls bats, is every bit as important as protecting the larger, more "respected" animals such as wolves and bears.
"They probably play as potentially critical a role as any animal on the planet," he said. "Just from that standpoint alone, they're worth studying." | <urn:uuid:fe6f843d-5300-4829-8674-60f2d6ef89a2> | 2.890625 | 1,754 | Knowledge Article | Science & Tech. | 56.092368 |
1 min 58 sec
How do we know when a tornado is forming? Scientist Harold Brooks explains how Doppler radars are used to track storm formation.
ACTIVITY DESCRIPTION AND TEACHING MATERIALS
Watch >> How Do We Know: Tracking Tornadoes
TEACHING NOTES / CONTEXT FOR USE
This short educational video teaches about the formation and prediction of tornadoes and the future of severe weather due to climate change.
Assessment is at the discretion of the educator and how this video is applied and the expectations after viewing it.
REFERENCES AND RESOURCES
Harold Brooks - Dr. Harold Brooks is a research meteorologist and Head of the Mesoscale Applications Group at the National Severe Storms Laboratory (NSSL) in Norman, Oklahoma. | <urn:uuid:c32ebf65-a331-4978-b404-927eed4b2b1e> | 3.390625 | 166 | Truncated | Science & Tech. | 37.644737 |
Looking for Cramster? Cramster is now Chegg Homework Help. Learn More
Three point charges are arranged as shown in the figure below. (Take q1 = 5.64 nC, q2 = 5.30 nC, and q3 = -2.97 nC.)
Find the direction of the electric force on the particle at the origin. (counterclockwise from the +x-axis)
Anonymous answered6 minutes later
You need a Homework Help subscription to view this answer! | <urn:uuid:1ff9ab84-1139-43e3-8a08-b35e92b82f90> | 2.6875 | 108 | Q&A Forum | Science & Tech. | 79.730817 |
A device used to prevent stray light.
The class of subatomic particles in which protons and neutrons are included. The baryons form the atomic nucleus, along with another class of particles – the mesons. We, and everything we can see around us, are made of baryonic matter.
The Big Bang theory is the most accepted theory so far to describe the origin and evolution of the Universe. According to it, all the matter and energy in the Universe was originally contained in a very small 'point' – technically called a 'singularity' – at an almost infinite temperature and density. About 10 to 20 billion years ago this tiny Universe started to expand, and has not stopped expanding since. This theory was first drafted by Russian physicist George Gamow in the late forties, although only when the cosmic microwave background was discovered in 1964 did the astronomical community start to take it seriously. As of today, apart from the cosmic microwave background, two other pillars support the Big Bang theory: the current expansion of the Universe and the measured abundance of light elements.
See Critical density
One billion equals one million million (UK/Europe), and 1000 million (US).
Pair of stars bound together by mutual gravitation and orbiting their common centre of mass.
An object with so much mass concentrated in it, and therefore such a strong gravitational pull that nothing, not even light can escape from it. One way in which black holes are believed to form is when massive stars collapse at the end of their lives.
Type of active galaxy named after an object in the constellation of Lacerta, the BL Lacertae object. They form a subset of the quasar population. The emission of blazars is highly variable. The activity may be caused by jets of gas being expelled from the central region of the active galaxy, i.e. the supermassive black hole in the active galactic nucleus.
When a distant object moves toward the observer the lines in its spectrum shift to shorter (bluer) wavelengths. This is because of the apparent compression of the wave of light. As a result of this compression the wavelength shortens and thus shifts towards the blue side of the electromagnetic spectrum. The blueshift of an astronomical object is an indication of the speed at which this object is approaching the observer.
A kind of detector mainly used to measure infrared radiation. A bolometer works by heating up as it absorbs the radiation that reaches it. The increase in temperature is measured by an internal electrical resistance, and is a measure of the amount of radiation absorbed.
The German word 'Bremsstrahlung' means 'braking radiation'. A fast, charged particle, for example an electron, is slowed down when it passes through matter. The energy lost by the particle is emitted as electromagnetic radiation, or Bremsstrahlung.
A kind of 'failed' star: a small and opaque object whose mass is not sufficient to start, in its core, the nuclear reaction to transform hydrogen into helium. A brown dwarf cannot therefore produce enough energy to shine as a star. A brown dwarf's mass is not more than 0.08 solar masses. | <urn:uuid:882a6db7-7648-42cc-858c-025413430564> | 3.734375 | 642 | Knowledge Article | Science & Tech. | 44.43127 |
To set a variable from the makefile, write a line starting with the variable name followed by ‘=’ or ‘:=’. Whatever follows the ‘=’ or ‘:=’ on the line becomes the value. For example,
objects = main.o foo.o bar.o utils.o
defines a variable named
objects. Whitespace around the variable
name and immediately after the ‘=’ is ignored.
Variables defined with ‘=’ are recursively expanded variables. Variables defined with ‘:=’ are simply expanded variables; these definitions can contain variable references which will be expanded before the definition is made. See The Two Flavors of Variables.
The variable name may contain function and variable references, which are expanded when the line is read to find the actual variable name to use.
There is no limit on the length of the value of a variable except the
amount of swapping space on the computer. When a variable definition is
long, it is a good idea to break it into several lines by inserting
backslash-newline at convenient places in the definition. This will not
affect the functioning of
make, but it will make the makefile easier
Most variable names are considered to have the empty string as a value if you have never set them. Several variables have built-in initial values that are not empty, but you can set them in the usual ways (see Variables Used by Implicit Rules). Several special variables are set automatically to a new value for each rule; these are called the automatic variables (see Automatic Variables).
If you'd like a variable to be set to a value only if it's not already
set, then you can use the shorthand operator ‘?=’ instead of
‘=’. These two settings of the variable ‘FOO’ are identical
FOO ?= bar
ifeq ($(origin FOO), undefined) FOO = bar endif | <urn:uuid:f67a4211-90ad-4a8a-a899-2b6461865b2b> | 3.921875 | 425 | Tutorial | Software Dev. | 41.06874 |
A Data file consists of a list of positive random integers. The numbers are separated by space. Design pseudo code to perform the following tasks:
(a) Print all the numbers with 10 numbers in a line.
(b) Calculate the total value of the even numbers in the file.
(for example: totalValue=2+12+20+36+…and so on)
(c) Print the largest and smallest even numbers in the file.
Write a java program to implement your design in Q1
A Data file consists of a list of positive random integers. The numbers are separated
A famous homework question.
I have a simple rule on these : show me what you have done and I will help, but I will not do your homework for you
Post your ideas, code and attempts and people will gladly assist you. | <urn:uuid:db625999-6969-45a6-b012-ed682f2f629a> | 3.9375 | 175 | Q&A Forum | Software Dev. | 60.191765 |
Carbon dioxide may be bad for the climate, but it's good for the roses. Perhaps it's time we rehabilitated this gaseous villain
IT'S LIKE standing at the edge of a giant patchwork quilt. Stretching into the distance are broad bands of bright yellow alternated with patches of delicate white, all beneath a vast glass roof. This greenhouse full of flowers is just one of hundreds that dot the Dutch coast, where row after row of chrysanthemums, orchids and roses are fed carbon dioxide-enriched air, helping them to grow up to 30 per cent faster than normal.
While plenty of commercial greenhouses top up their air with extra CO2, what is unusual about this one is where its CO2 comes from. Until a few years ago, the greenhouse's operators used to burn natural gas for the sole purpose of generating CO2. Today it is piped from a nearby oil refinery. Each ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:3d2310ff-6bb1-4d4b-8973-7eec44593e32> | 3.171875 | 222 | Truncated | Science & Tech. | 58.606631 |
|Feb26-12, 11:20 AM||#1|
Gravitational field from earth/ center of mass
When calculating the gravitational field from the earth, why can we make the assumption that all of the mass of the earth is 'averaged' at the the geometrical center???
If we imagine the earth as a bunch of pieces, and then calculate the sum of forces from each of these pieces, would it not be different from imagining the earth as a single piece at the center with all of its mass?
What I mean is that a 'piece' of earth on the other side of the earth is pulling one me with a much much weaker force than a piece of earth that is right under my feet. The transition from the strength of the gravity from the earth that is close to me to the earth that is farther away is not linear, so why can we average the distances?
|Feb26-12, 11:51 AM||#2|
The story is that Newton invented calculus to answer that very question.
He created the idea of the 'integral' to sum the forces of every piece of the earth to find the net effect---and he found that the situation is identical to the entire mass of the earth collapse to a point at its center.
The calculation is, in effect, 'averaging' in a non-linear way (you take into account the inverse-square law---which is why the answer is what it is). But I think a better way to think about how it works is by symmetry. While the piece of earth directly below you pulls you more strongly, there are far more pieces of earth on the opposite side. And the amount more stuff on the other side, increases exactly so as to compensate for the inverse square decrease of the force.
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Add this to the murderous microbe highlight reel--a single strain of bacteria could have worsened the Great Dying event 250 million years ago, producing prodigious methane and choking out most other life on Earth. During the Permian-Triassic extinction event, 96 percent of everything in the oceans and 70 percent of everything on land died out. And much of the blame could lie at the feet of one type of marine bacteria, a new study claims.
The era around 250-252 million years ago is marked by a huge and rapid die-off of most of the ocean’s life, and scientists have several hypotheses explaining why. Some have argued it was a major meteorite impact, like the one that killed the dinosaurs; others posit that gigantic volcano eruptions were to blame; others argue for mass ocean poisoning; and still others blame huge methane releases.
Researchers at MIT say it may be a combination of all these things, hinging on the ability of bacteria to break down nickel and produce methane. They presented their theory at the American Geophysical Union’s recent meeting.Volcanic activity at the Siberian Traps in northern Russia produced vast amounts of nickel, right around the same time as the Permian die-off. These eruptions--one of the largest volcanic events ever--also threw massive quantities of ash and dust into the atmosphere, and as such they have been fingered as a global-cooling culprit that dramatically altered the atmosphere. But Daniel Rothman and colleagues had another theory for the Siberian Traps’ influence.
Somehow this nickel-rich material made its way into the oceans, where it was gobbled up by bacteria called methanosarcina, they argue. Rothman and his team determined that these bacteria evolved the ability to break down nickel about 251 million years ago. The new nickel glut caused a huge bacterial population spike, which produced mountains of methane and also depleted the oceans’ oxygen.
Scientists have already theorized that bacteria and algae hoarded most of the remaining resources after everything else died, which made recovery even more difficult. But pinpointing what caused the Great Dying remains elusive.
This new theory is speculative, to say the least, and it doesn’t explain how nickel from Siberia got into the world’s oceans. But it offers an intriguing possibility. As we learned after the Deepwater Horizon spill, ocean-dwelling microbes are quite capable of both consuming and producing hydrocarbons.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more. | <urn:uuid:09edf088-0459-4f84-9506-7de58f9c54a6> | 3.5 | 553 | Truncated | Science & Tech. | 36.714851 |
The Hubble Telescope is named after the American astronomer Edwin P. Hubble.
Hubble is the first general-purpose orbiting observatory . Launched on 24th April, 1990,
Aboard the Space Shuttle Discovery The HST makes observations in the visible, infrared, and ultraviolet regions of the electromagnetic spectrum (see Electromagnetic Radiation). The primary mirror of the HST has a diameter of 94.5 in (2.4 m), and the optics of the telescope are designed so that when making a visible-light observation, the telescope can theoretically resolve astronomical objects that are an angular distance of 0.05 arcsecond apart. For comparison, traditional large ground-based telescopes under very nice sky conditions have an image resolution of about 0.5 arcsecond.
After the HST was placed in orbit, scientists discovered that its primary mirror had a systematic aberration, the result of a manufacturing error. A service mission to repair the problem was carried out in December 1993, using the Space Shuttle Endeavour. A device called the Corrective Optics Space Telescope Axial Replacement (COSTAR) was inserted in place of one of the original instruments, the High-Speed Photometer. The original Wide-Field Planetary Camera, which had a different optical path from the other four instruments, was replaced with the Wide-Field Planetary Camera 2 (WFPC 2), which has a built-in correction for the aberration in the primary mirror. This servicing mission gave HST the ability to conduct the research for which it was intended, including measuring the rate at which the universe is expanding (a figure known as the Hubble constant) from which the age of the universe can be calculated.
A second servicing mission took place in February 1997, when astronauts installed the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) and the Space Telescope Imaging Spectrograph (STIS). NICMOS was used to observe regions of space where stars are born and to study extremely distant objects whose light has been red shifted into the infrared, while STIS took spectra of objects including gas swirling around black holes at the centres of galaxies. NICMOS worked for two years before running out of the nitrogen-ice coolant needed to keep it at sub-zero temperatures. A third servicing mission, in December 1999, replaced HST's ageing gyroscopes and computer. On the fourth servicing mission, in March 2002, astronauts replaced HST's solar panels with smaller yet more efficient ones, providing 20 per cent more electricity so that all HST's instruments can operate at the same time. They also installed the Advanced Camera for Surveys (ACS), which covers twice the area of sky as the WFPC 2 with five times the sensitivity. Among its tasks will be to monitor weather on planets in our own solar system, to search for planets around other stars (see Extrasolar Planets), and to survey the distribution of galaxies in the distant universe. The ACS replaced the Faint Object Camera, the last of HST's original instruments. During this same mission, the astronauts also installed a new radiator for NICMOS, restoring its infrared observational capability.
Among the many achievements of its first decade of operation, the HST provided the best views of the planet Jupiter when fragments of Comet Shoemaker-Levy 9 bombarded it in July 1994. The HST's images of the effects produced by the collisions provided scientists with important data for a spectral analysis of the chemical makeup of Jupiter's atmosphere. In December 1995 the HST took one of its most important images, a composite of exposures made over 10 days and known as the Hubble Deep Field. By pointing the telescope at an area of sky devoid of bright objects for up to 40 minutes at a time, the astronomers were able to detect galaxies fainter (down to magnitude 30) and more distant (up to 12 billion light years away) than any seen before. In October 1998 the telescope was used to take a 36-hour infrared exposure of a small portion of the Deep Field, revealing even fainter, cooler, and more distant galaxies. The HST has also provided evidence for the presence of supermassive black holes at the centres of many galaxies.
A 5th and final HST servicing mission was scheduled for 2006, but this was cancelled in January 2004. The mission would have involved astronauts fitting an entirely new instrument, the Cosmic Origins Spectrograph, which would have taken spectra of hot gas such as in the centres of quasars, plus an improved Wide Field Camera. This final refurbishment would have given HST greater discovery capabilities than ever before. It is now hoped that HST will continue in operation until 2010, when it will be superseded by a much larger telescope, the James Webb Space Telescope. | <urn:uuid:c6920792-e088-4d41-8c59-0ead8aa9a0c8> | 3.90625 | 968 | Knowledge Article | Science & Tech. | 35.329113 |
Survival in Extremophile conditions- Balloon Launches
Working at NASA Ames, we had the good fortune of meeting Jack Cackler, who was trying to prototype small balloon launches to the stratosphere. Located at 10 to 50 kilometers above the ground, the stratosphere has conditions that are out of this world: a temperature range of -56 to -3°C (it actually increases as you ascend), and atmosphere 0.001 percent of that of earth’s sea level. To take advantage of this rare opportunity, we prepared two dried samples of S. pasteurii to be sent up in the balloon, to test the ability of the bacteria to withstand the extremes in temperature, depressurization and radiation bombardment. Note that the microbes we flew were not genetically altered, and all practice was done under proper FAA notification.
Thorough Protocols for the preparation can be found here
Our first balloon went up to 80,000 ft (24 kilometers), from which the curvature of the earth was visible.
Unfortunately, our S. pasteurii cargo, as well as other biological samples, cargo, did not survive the first flight. The biocemented brick that accompanied the samples up suffered some mechanical damage, and a qualitative change in brittleness. It is suggested that the this structural change was influenced by the temperature change, and corresponding thermal contraction/expansion. Further experimentation will have to be done to isolate the cause of the structural change and investigate its implications for space applications.
Our second balloon went up to 110,000 ft (33.5 kilometers), where the atmospheric pressure was slightly below that of Mars.
During our second flight (accompanied by the BBC ), we prepared the S. pasteurii inside Whirlpak bags. Surprisingly enough, upon retrieval, the the samples inside the Whirlpak bags exhibited urease activity! The ones outside the bags did not, though mysteriously enough both samples grew back on Bang media plates in seemingly equal quantities. Further experimentation must be done to ascertain the exact nature of the survival.
Our original grand plan was to have one final balloon flight, after our transformation of S. pasteurii with Newcastle 2009’s sporulation regulation gene, to see if induced sporulation could have increase the percentage of survivors. Unfortunately, difficulties in transforming S. pasteurii put this this plan on hold. | <urn:uuid:9b8d0945-da95-4cf7-b14e-1ff2ae16cb97> | 3.1875 | 478 | Knowledge Article | Science & Tech. | 37.190645 |
Density (symbol: ρ - Greek: rho) (ISO 31: volumic mass) is a measure of mass per unit of volume. The higher an object's density, the higher its mass per volume. The average density of an object equals its total mass divided by its total volume. A denser object (such as iron) will have less volume than an equal mass of some less dense substance (such as water).
where ρ equals density, m equals total mass, and V equals volume.
Formerly mass and volume were linked by defining the gram to be the mass of one cubic centimeter of water at 4°C which meant that water had density 1 kg/litre. However, using one cubic centimeter of water as a standard for one gram is problematic due to the possibility of mass loss from evaporation as well as changes in density with temperature. For this reason alternative definitions of the meter and kilogram have been developed, which can be reproduced more reliably in a laboratory. Because of slight changes in the metre and kilogram due to these new definitions, the density of water at 4°C is not quite exactly 1, but 0.99995 kg/litre. A cubic meter of water thus weighs approximately one metric tonne.
Note the low density of aluminium compared to most other metals. For this reason, aircraft were made of aluminium in the past. Also note that air has a nonzero, albeit small, density. Aerogel is the world's lightest solid.
Density may denote how much of a certain substance, object or occurrence is present per unit area or volume.
Often used is population density, meaning how many people per square kilometre (or square mile) on average live in an area.
The density of discrete entities such as people is difficult to characterise as a continuous quantity.
Geographers and mathematicians have made a number of attempts to formalize the concept of population density. | <urn:uuid:69f017a8-9537-4a53-b359-ffafd6a2548d> | 4 | 402 | Knowledge Article | Science & Tech. | 42.4622 |
What is the Earth's Average Temperature?
Topic: Planetary energy balance: the temperature of the planet vs. the temperature of the earth's surface
Course type: Introductory, non-majors' college level
This activity teaches Climate Literacy Essential Principle 2: Climate is regulated by complex interactions among components of the Earth system
This activity teaches: Concept C - Greenhouse Effect. The amount of solar energy absorbed or radiated by Earth is modulated by the atmosphere and depends on its composition. Greenhouse gases— such as water vapor, carbon dioxide, and methane— occur naturally in small amounts and absorb and release heat energy more efficiently than abundant atmospheric gases like nitrogen and oxygen. Small increases in carbon dioxide concentration have a large effect on the climate system.
GoalsStudents should be able to do the following:
- Estimate the average temperature of the earth as a whole (atmosphere and surface combined), by applying several basic physical principles to satellite observations of solar energy.
- Compare this temperature to the global average temperature of the earth's surface.
DescriptionThis short, pedagogically flexible activity (Microsoft Word 2007 (.docx) 516kB Jun15 11) guides students to answer six questions about the radiative energy budget of the earth as a whole. The activity gives students practice applying basic physical principles to observations and raises a question that can motivate investigation of the greenhouse effect.
(a) the concept of a balanced (energy) budget;By applying these principles, students can determine the temperature that the earth must have to create the observed, nearly balanced planetary energy budget.
(b) a basic law of radiation ("the warmer an object is, the more radiation it emits"); and
(c) satellite observations of radiation.
Students then contrast this planetary temperature with the global, long-term average temperature of the earth's surface, which raises the question of why the surface is so much warmer than the planet as a whole. Investigation of the greenhouse effect in subsequent activities can resolve the apparent discrepancy.
The activity can be implemented pedagogically in any of a variety of ways, such as in-class, small-group collaborative problem solving; out-of-class individual homework; pre-class, online assignment, etc. Most of the questions can be implemented at least partly as multiple choice questions if desired, for use with clickers in class, for example.
Activity: What is the Earth's Average Temperature? (Microsoft Word 2007 (.docx) 516kB Jun15 11)
Blackbody Radiative Emission vs. Temperature (Excel file) (Excel 2007 (.xlsx) 57kB Jun15 11)
The answers to the six questions posed in the activity are straightforward. Students can turn in their responses in written form (paper-based or online, in class or as homework). Alternatively, most of the questions can be posed as multiple choice questions for use with online quizzes or clickers in class. As a very basic follow-up, students should be able to describe the fundamental property of an object that changes when an object absorbs more radiant energy than it emits. [i.e. the temperature...and it must increase].
Connections to other Activities
This activity is one of a suite of five activities designed to address the concepts that address how the greenhouse effect influences global temperature (Principle 2, Concept C) which can be used individually or combined as desired.
This activity can be used as a warm-up for a variety of investigations of the greenhouse effect and global warming. One example is The Greenhouse Effect: Why is the Earth's Surface So Much Warmer than the Earth as Seen from Space?, a complementary activity in which students apply the same physical concepts used here to analyze energy budgets for the atmosphere and for the earth's surface. The intent is to help students understand better how the greenhouse effect works and how enhancing the greenhouse effect leads to global warming.
Earth's Global Energy Budget ( 1.1MB Jun15 11), Kevin Trenberth, John Fasullo, and Jeffrey Kiehl, March 2009, Bulletin of the American Meteorological Society (PDF file)
More on this topic from CLEAN
How to teach with this principle from the CLEAN site
See CLEAN reviewed activities for teaching about Greenhouse Effect | <urn:uuid:861c78e0-5cc7-4253-b55e-b0c044bb1cf6> | 3.390625 | 878 | Tutorial | Science & Tech. | 30.506817 |
NSIDC: April 6, 2009
Arctic sea ice younger, thinner as melt season begins
Arctic sea ice extent has begun its seasonal decline towards the September minimum. Ice extent through the winter was similar to that of recent years, but lower than the 1979-2000 average. More importantly, the melt season has begun with a substantial amount of thin first-year ice, which is vulnerable to summer melt.
Overview of conditions
Sea ice extent averaged over the month of March 2009 was 15.16 million km² (5.85 million miles²). This was 730,000 km² (282,000 miles²) above the record low of 2006, but 590,000 km² (228,000 miles²) below the 1979-2000 average.
Figure 2. The graph above shows daily sea ice extent. The solid blue line indicates 2008-2009; the dashed green line shows 2006-2007 (the record-low summer minimum occurred in 2007); and the solid gray line indicates average extent from 1979 to 2000. Sea Ice Index data. —Credit: National Snow and Ice Data Center High-resolution image
Conditions in context
At the end of last summer's melt season, extensive areas of open water froze up quickly, once air temperatures cooled in the fall. By February 28, ice extent had reached its annual maximum. Although the maximum ice extent occurred slightly earlier than usual, ice extent remained close to the maximum level through much of March.
March 2009 compared to past Marches
Including March 2009, the past 6 years have all had ice extent substantially lower than normal. The linear trend indicates that for the month of March, ice extent is declining by 2.7% per decade, an average of 43,000 km² (16,000 miles²) of ice per year.
Arctic winter warmer than average
Overall, it was a fairly warm winter in the Arctic. Air temperatures over the Arctic Ocean were an average of 1-2 °C (1.8-3.6 °F) above normal, with notable regional variations. The Barents Sea region was over 4 °C (7.2 °F) warmer than average this winter. This warmth probably stemmed from unusually low sea ice extent in the region throughout much of the winter, which allowed the ocean to pump heat into the atmosphere. The Bering Sea, in contrast, experienced a cool winter, with temperatures 1-2 °C (1.8-3.6 °F) below average. The cooler conditions were consistent with the above-average sea ice extent in the Bering Sea through much of the winter.
Sea ice young and thin as melt season begins
How vulnerable is the ice cover as we go into the summer melt season? To answer this question, scientists also need information about ice thickness. Indications of winter ice thickness, commonly derived from ice age estimates, reveal that the ice is thinner than average, suggesting that it is more susceptible to melting away during the coming summer.
As the melt season begins, the Arctic Ocean is covered mostly by first-year ice, which formed this winter, and second-year ice, which formed during the winter of 2007-2008. First-year ice in particular is thinner and more prone to melting away than thicker, older, multi-year ice. This year, ice older than two years accounted for less than 10% of the ice cover at the end of February. From 1981 through 2000, such older ice made up an average of 30% of the total sea ice cover at this time of the year.
While ice older than 2 years reached record lows, the fraction of second-year sea ice increased compared to last winter. Some of this second-year ice will survive the summer melt season to replenish the Arctic's store of older ice; however, in recent years less young ice has made it through the summer. To restore the amount of older ice to pre-2000 levels, large amounts of this young ice would need to endure through summer for several years in a row.
But conditions may not always favor the survival of second-year and older ice. Each winter, winds and ocean currents move some sea ice out of the Arctic ocean. This winter, some second-year ice survived the 2008 melt season only to be pushed out of the Arctic by strong winter winds. Based on sea ice age data from Jim Maslanik and Chuck Fowler at the University of Colorado, since the end of September 2008, 390,000 km² (150,000 miles²) of second-year ice and 190,000 km² (73,000 miles²) of older (more than 2 years old) ice moved out of the Arctic. View animation (1.1 MB).
Maslanik J. A., C. Fowler, J. Stroeve, S. Drobot, J. Zwally, D. Yi, & W. Emery. 2007. A younger, thinner Arctic ice cover: Increased potential for rapid, extensive sea-ice loss. Geophysical Research Letters, 34, L24501; doi:10.1029/2007GL032043.
Fowler, C., W. J. Emery, & J. Maslanik. 2004. Satellite-derived evolution of Arctic sea ice age: October 1978 to March 2003. IEEE Geosci. Remote Sensing Letters, 1(2), 71–74; doi:10.1109/LGRS.2004.824741.
Link to NSIDC page: http://nsidc.org/arcticseaicenews/index.html | <urn:uuid:f84040b1-6046-4f2d-9519-6cef3c2487c7> | 2.84375 | 1,146 | Knowledge Article | Science & Tech. | 69.740915 |
Wednesday, September 8, 2010
Photos by Jaap de Roode and Lisa Sharling.
By Carol Clark
Emory biologists are studying whether monarch butterflies can cure themselves and their offspring of disease by using medicinal plants. The National Science Foundation recently awarded Jaap de Roode a $500,000 grant to further his research, which focuses on the behavior of monarchs infected with a protozoan parasite.
“We have shown that some species of milkweed, the larva’s food plants, can reduce parasite infection in the monarchs,” says de Roode, (in photo, at left) assistant professor of biology. “And we have also found that infected female butterflies prefer to lay their egg on plants that will make their offspring less sick, suggesting that monarchs have evolved the ability to medicate their offspring.”
Few studies have been done on self-medication by animals, but some scientists have theorized that the practice may be more widespread than we realize. “We believe that our experiments provide the best evidence to date that animals use medication,” de Roode says.
Take a video tour of the monarch butterfly lab.
“The results are also exciting because the behavior is trans-generational,” says Thierry Lefevre, a post-doctoral fellow in de Roode’s lab. “While the mother is expressing the behavior, only her offspring benefit.”
Monarch butterflies are known for their spectacular migration from the United States to Mexico each year, and for the striking pattern of orange, black and white on their wings. That bright coloration is a warning sign to birds and other predators that the butterfly may be poisonous.
Monarch caterpillars feed on any of dozens of species of milkweed plants, including some species that contain high levels of cardenolides. These chemicals do not harm the caterpillars, but make them toxic to predators even after they emerge as adults from their chrysalises.
Previous research has focused on whether the butterflies choose more toxic species of milkweed to ward off predators. De Roode wondered if the choice could be related to the parasite Ophryocystis elektroscirrha. The parasites invade the gut of the caterpillars and then persist when they become adult monarchs. An infected female passes on the parasites when she lays her eggs. If the adult butterfly leaves the pupal stage with a severe parasitic infection, it begins oozing fluids from its body and dies (see photo, at right). Even if the butterflies survive, they do not fly as well or live as long as uninfected ones.
Experiments in de Roode’s lab have shown that a female infected with the parasites prefers to lay her eggs on a toxic species of milkweed, rather than a non-toxic species. Uninfected female monarchs, however, showed no preference.
The Emory scientists will use the NSF grant to see if the lab results can be replicated in nature, across different populations of monarchs in various regions of the world. De Roode’s collaborator, chemical ecologist Mark Hunter of the University of Michigan, received $150,000 from the NSF to identify the chemicals that account for the medicinal properties of the milkweed plants.
The monarch butterfly's medicine kit
Test your wings in a lab
Farming ants reveal evolution secrets
Tiny aphids hold big surprises in genome | <urn:uuid:330e6fcc-4712-4b82-98a8-1906783ed239> | 3.5625 | 722 | Personal Blog | Science & Tech. | 36.122037 |
I can't really figure out what I need to plug in. Here is the problem ...
At 0 degrees Celsius, the heat loss H (in kilocalories per square meter per hour) from a person's body can be modeled by
Where v is the wind speed (in meters per second)
a.) Find and interpret it's meaning in this situation
b.) Find the rates of change of H when v=2 and v=5
Thanks in advance. Word problems tend to confuse me | <urn:uuid:605ebc0a-82e0-4b42-9155-1b6676f93897> | 2.90625 | 102 | Q&A Forum | Science & Tech. | 89.814458 |
Serpentine Seamounts in the Mariana Forearc: Shallow Material Releases from Downgoing Plates
This activity was selected for the On the Cutting Edge Reviewed Teaching Collection
This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are
- Scientific Accuracy
- Alignment of Learning Goals, Activities, and Assessments
- Pedagogic Effectiveness
- Robustness (usability and dependability of all components)
- Completeness of the ActivitySheet web page
For more information about the peer review process itself, please see http://serc.carleton.edu/NAGTWorkshops/review.html.
This activity has gone through a workshop review process.
This resource was reviewed as part of the May 2009 MARGINS Mini-Lesson Workshop. Each activity received verbal feedback from two participants who had reviewed the activity and activity sheet using these guidelines. Authors revised the activities and activity sheets in response to these comments during the workshop.
This page first made public: Oct 16, 2008
This is a resource of published images and diagrams, and GeoMapApp/Google Earth captures of geophysical survey results for use in describing the unique phenomenon of active serpentinite mud volcanism observed in the shallow forearc region of the Mariana subduction system. Students should be familiar with the concept of subduction and one of its primary petrologic implications - that materials (specifically sediments, ocean crust, and H2O-rich fluids) long residing at the Earth's surface are transported down deep sea trenches, with the release of bound fluids (and fluid-soluble chemical species from the downgoing plate) occurring progressively with increasing depth. These materials are intended to be used as aids in lecture or discussions of this phenomenon in the context of instruction on the process of subduction.t
This resource is intended to be used in a lecture/demonstration setting, as setup materials for more involved exercises examining material fluxes through subduction systems and/or the physical and tectonic implications of the development of mantle serpentinites.
Context for Use
Description and Teaching Materials
Linked PDF file of Mariana forearc seamount pictures and data (Acrobat (PDF) 122.9MB May28 09)
Instructor's notes (Microsoft Word 33kB May28 09)
Teaching Notes and Tips
References and Resources
Oakley, A.J.; Taylor, B.; Fryer, P.; Moore, G.F.; Goodliffe, A M; Morgan, J.K., 2007, Emplacement, growth, and gravitational deformation of serpentinite seamounts on the Mariana forearc. Geophysical Journal International, vol. 170, no. 2, pp.615-634.
Fryer, Patricia B; Salisbury, Matthew H. (2006) Leg 195 synthesis; Site 1200; serpentinite seamounts of the Izu-Bonin/Mariana convergent plate margin, ODP Leg 125 and 195 drilling results. Proceedings of the Ocean Drilling Program, Scientific Results (CD ROM), vol. 195, 30 pp.
Savov, I.P., Ryan, J.G., D'Antonio, M. and P. Fryer, 2007, Petrology and geochemistry of serpentinized peridotites from Mariana Forearc, South Chamorro Seamount, ODP Leg 195: Implications for the elemental recycling across and along the Mariana arc-basin system. Journal of Geophysical Research, v. 112, doi:10.1029/2006JB004749 | <urn:uuid:9b90787d-00ce-418c-8329-773489f0fb56> | 2.765625 | 754 | Knowledge Article | Science & Tech. | 40.3384 |
In chemistry and manufacturing, electrolysis is a method of using a direct electric current (DC) to drive an otherwise non-spontaneous chemical reaction. Electrolysis is commercially highly important as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell.
- 1785 – Martinus van Marum's electrostatic generator was used to reduce tin, zinc, and antimony from their salts using electrolysis.
- 1800 – William Nicholson and Johann Ritter decomposed water into hydrogen and oxygen.
- 1807 – Potassium, sodium, barium, calcium and magnesium were discovered by Sir Humphry Davy using electrolysis.
- 1875 – Paul Émile Lecoq de Boisbaudran discovered gallium using electrolysis.
- 1886 – Fluorine was discovered by Henri Moissan using electrolysis.
- 1886 – Hall-Héroult process developed for making aluminium
- 1890 – Castner-Kellner process developed for making sodium hydroxide
Electrolysis is the passage of a direct electric current through an ionic substance that is either molten or dissolved in a suitable solvent, resulting in chemical reactions at the electrodes and separation of materials.
The main components required to achieve electrolysis are :
- An electrolyte : a substance containing free ions which are the carriers of electric current in the electrolyte. If the ions are not mobile, as in a solid salt then electrolysis cannot occur.
- A direct current (DC) supply : provides the energy necessary to create or discharge the ions in the electrolyte. Electric current is carried by electrons in the external circuit.
- Two electrodes : an electrical conductor which provides the physical interface between the electrical circuit providing the energy and the electrolyte
Electrodes of metal, graphite and semiconductor material are widely used. Choice of suitable electrode depends on chemical reactivity between the electrode and electrolyte and the cost of manufacture.
Process of electrolysis
The key process of electrolysis is the interchange of atoms and ions by the removal or addition of electrons from the external circuit. The desired products of electrolysis are often in a different physical state from the electrolyte and can be removed by some physical processes. For example, in the electrolysis of brine to produce hydrogen and chlorine, the products are gaseous. These gaseous products bubble from the electrolyte and are collected.
- 2 NaCl + 2 H2O → 2 NaOH + H2 + Cl2
A liquid containing mobile ions (electrolyte) is produced by:
- Solvation or reaction of an ionic compound with a solvent (such as water) to produce mobile ions
- An ionic compound is melted (fused) by heating
An electrical potential is applied across a pair of electrodes immersed in the electrolyte.
Each electrode attracts ions that are of the opposite charge. Positively charged ions (cations) move towards the electron-providing (negative) cathode, whereas negatively charged ions (anions) move towards the positive anode.
At the electrodes, electrons are absorbed or released by the atoms and ions. Those atoms that gain or lose electrons to become charged ions pass into the electrolyte. Those ions that gain or lose electrons to become uncharged atoms separate from the electrolyte. The formation of uncharged atoms from ions is called discharging.
The energy required to cause the ions to migrate to the electrodes, and the energy to cause the change in ionic state, is provided by the external source of electrical potential.
Oxidation and reduction at the electrodes
Oxidation of ions or neutral molecules occurs at the anode, and the reduction of ions or neutral molecules occurs at the cathode. For example, it is possible to oxidize ferrous ions to ferric ions at the anode:
aq → Fe3+
aq + e–
6 + e– → Fe(CN)4-
Neutral molecules can also react at either electrode. For example: p-Benzoquinone can be reduced to hydroquinone at the cathode:
In the last example, H+ ions (hydrogen ions) also take part in the reaction, and are provided by an acid in the solution, or the solvent itself (water, methanol etc.). Electrolysis reactions involving H+ ions are fairly common in acidic solutions. In alkaline water solutions, reactions involving OH- (hydroxide ions) are common.
The substances oxidised or reduced can also be the solvent (usually water) or the electrodes. It is possible to have electrolysis involving gases. (Such as when using a Gas diffusion electrode)
Energy changes during electrolysis
The amount of electrical energy that must be added equals the change in Gibbs free energy of the reaction plus the losses in the system. The losses can (in theory) be arbitrarily close to zero, so the maximum thermodynamic efficiency equals the enthalpy change divided by the free energy change of the reaction. In most cases, the electric input is larger than the enthalpy change of the reaction, so some energy is released in the form of heat. In some cases, for instance, in the electrolysis of steam into hydrogen and oxygen at high temperature, the opposite is true. Heat is absorbed from the surroundings, and the heating value of the produced hydrogen is higher than the electric input.
The following techniques are related to electrolysis:
- Electrochemical cells, including the hydrogen fuel cell, utilise differences in Standard electrode potential in order to generate an electrical potential from which useful power can be extracted. Although related via the interaction of ions and electrodes, electrolysis and the operation of electrochemical cells are quite distinct. A chemical cell should not be thought of as performing "electrolysis in reverse".
Faraday's laws of electrolysis
First law of electrolysis
In 1832, Michael Faraday reported that the quantity of elements separated by passing an electric current through a molten or dissolved salt is proportional to the quantity of electric charge passed through the circuit. This became the basis of the first law of electrolysis:
Second law of electrolysis
Faraday discovered that when the same amount of electricity is passed through different electrolytes connected in series, the mass of substance liberated/deposited at the electrodes is directly proportional to their equivalent weights.
- Production of aluminium, lithium, sodium, potassium, magnesium, calcium
- Coulometric techniques can be used to determine the amount of matter transformed during electrolysis by measuring the amount of electricity required to perform the electrolysis
- Production of chlorine and sodium hydroxide
- Production of sodium chlorate and potassium chlorate
- Production of perfluorinated organic compounds such as trifluoroacetic acid
- Production of electrolytic copper as a cathode, from refined copper of lower purity as an anode.
Electrolysis has many other uses:
- Electrometallurgy is the process of reduction of metals from metallic compounds to obtain the pure form of metal using electrolysis. For example, sodium hydroxide in its molten form is separated by electrolysis into sodium and oxygen, both of which have important chemical uses. (Water is produced at the same time.)
- Anodization is an electrolytic process that makes the surface of metals resistant to corrosion. For example, ships are saved from being corroded by oxygen in the water by this process. The process is also used to decorate surfaces.
- A battery works by the reverse process to electrolysis.
- Production of oxygen for spacecraft and nuclear submarines.
- Electroplating is used in layering metals to fortify them. Electroplating is used in many industries for functional or decorative purposes, as in vehicle bodies and nickel coins.
- Production of hydrogen for fuel, using a cheap source of electrical energy.
- Electrolytic Etching of metal surfaces like tools or knives with a permanent mark or logo.
Electrolysis is also used in the cleaning and preservation of old artifacts. Because the process separates the non-metallic particles from the metallic ones, it is very useful for cleaning old coins and even larger objects.
Competing half-reactions in solution electrolysis
Using a cell containing inert platinum electrodes, electrolysis of aqueous solutions of some salts leads to reduction of the cations (e.g., metal deposition with, e.g., zinc salts) and oxidation of the anions (e.g. evolution of bromine with bromides). However, with salts of some metals (e.g. sodium) hydrogen is evolved at the cathode, and for salts containing some anions (e.g. sulfate SO42−) oxygen is evolved at the anode. In both cases this is due to water being reduced to form hydrogen or oxidised to form oxygen. In principle the voltage required to electrolyze a salt solution can be derived from the standard electrode potential for the reactions at the anode and cathode. The standard electrode potential is directly related to the Gibbs free energy, ΔG, for the reactions at each electrode and refers to an electrode with no current flowing. An extract from the table of standard electrode potentials is shown below.
|Na+ + e− Na(s)||−2.71|||
|Zn2+ + 2e− Zn(s)||−0.7618|||
|2H+ + 2e− H2(g)||≡ 0|
|Br2(aq) + 2e− 2Br−||+1.0873|||
|O2(g) + 4H+ + 4e− 2H2O||+1.23|||
|Cl2(g) + 2e− 2Cl−||+1.36|||
8 + 2e− 2SO2−
In terms of electrolysis, this table should be interpreted as follows
- oxidised species (often a cation) nearer the top of the table are more difficult to reduce than oxidised species further down. For example it is more difficult to reduce sodium ion to sodium metal than it is to reduce zinc ion to zinc metal.
- reduced species (often an anion) near the bottom of the table are more difficult to oxidise than reduced species higher up. For example it is more difficult to oxidise sulfate anions than it is to oxidise bromide anions.
- the electrode potential for the reduction producing hydrogen is −0.41 V
- the electrode potential for the oxidation producing oxygen is +0.82 V.
Comparable figures calculated in a similar way, for 1M zinc bromide, ZnBr2, are −0.76 V for the reduction to Zn metal and +1.10 V for the oxidation producing bromine. The conclusion from these figures is that hydrogen should be produced at the cathode and oxygen at the anode from the electrolysis of water which is at variance with the experimental observation that zinc metal is deposited and bromine is produced. The explanation is that these calculated potentials only indicate the thermodynamically preferred reaction. In practice many other factors have to be taken into account such as the kinetics of some of the reaction steps involved. These factors together mean that a higher potential is required for the reduction and oxidation of water than predicted, and these are termed overpotentials. Experimentally it is known that overpotentials depend on the design of the cell and the nature of the electrodes.
For the electrolysis of a neutral (pH 7) sodium chloride solution, the reduction of sodium ion is thermodynamically very difficult and water is reduced evolving hydrogen leaving hydroxide ions in solution. At the anode the oxidation of chlorine is observed rather than the oxidation of water since the overpotential for the oxidation of chloride to chlorine is lower than the overpotential for the oxidation of water to oxygen. The hydroxide ions and dissolved chlorine gas react further to form hypochlorous acid. The aqueous solutions resulting from this process is called electrolyzed water and is used as a disinfectant and cleaning agent.
Electrolysis of water
One important use of electrolysis of water is to produce hydrogen.
- 2 H2O(l) → 2 H2(g) + O2(g); E0 = -1.229 V
Hydrogen can be used as a fuel for powering internal combustion engines by combustion or electric motors via hydrogen fuel cells (see Hydrogen vehicle). This has been suggested as one approach to shift economies of the world from the current state of almost complete dependence upon hydrocarbons for energy (See hydrogen economy.)
The energy efficiency of water electrolysis varies widely. The efficiency of an electrolyser is a measure of the enthalpy contained in the hydrogen (to under go combustion with oxygen, or some other later reaction), compared with the input electrical energy. Heat/enthalpy values for hydrogen are well published in science and engineering texts, as 144 MJ/kg. Note that fuel cells (not electrolysers) cannot utilise this full amount of heat/enthalpy, which has led to some confusion when calculating efficiency values for both types of technology. In the reaction, some energy is lost as heat, a useless byproduct. Some reports quote efficiencies between 50% and 70% for alkaline electrolysers; however, much higher practical efficiencies are available with the use of PEM and catalytic technology, such as 95% efficiency. In the US there is still an occasional erroneous tendency to use the 'Lower Heating Value' for efficiencies. This value (becoming obsolete) does not represent the total amount of energy within the hydrogen, hence the efficiency appears lower than when using the more accurately defined values. The theoretical maximum considers the total amount of energy required for the formation of the hydrogen and oxygen from water. Note that (in more broader contexts of energy efficiency), these values refer only to the efficiency of converting electrical energy into hydrogen's chemical energy; the energy lost in generating the electricity is not included.
NREL estimated that 1 kg of hydrogen (roughly equivalent to 3 kg, or 4 L, of petroleum in energy terms) could be produced by wind powered electrolysis for between $5.55 in the near term and $2.27 in the long term.
About 4% of hydrogen gas produced worldwide is created by electrolysis, and normally used onsite. Hydrogen is used for the creation of ammonia for fertilizer via the Haber process, and converting heavy petroleum sources to lighter fractions via hydrocracking.
A specialized application of electrolysis involves the growth of conductive crystals on one of the electrodes from oxidized or reduced species that are generated in situ. The technique has been used to obtain single crystals of low-dimensional electrical conductors, such as charge-transfer salts.
Scientific pioneers of electrolysis include:
Pioneers of batteries:
|Wikimedia Commons has media related to: Electrolysis|
- The Supplement (1803 edition) to Encyclopedia Britannica 3rd edition (1797), volume 1, page 225, "Mister Van Marum, by means of his great electrical machine, decomposed the calces of tin, zinc, and antimony, and resolved them into their respective metals and oxygen" and gives as a reference Journal de Physiques, 1785.
- Sir William Crookes (1875). The Chemical news and journal of industrial science; with which is incorporated the "Chemical gazette.": A journal of practical chemistry in all its applications to pharmacy, arts and manufactures. Chemical news office. pp. 294–. Retrieved 27 February 2011.
- R. J. D. Tilley (2004). Understanding solids: the science of materials. John Wiley and Sons. pp. 281–. ISBN 978-0-470-85276-7. Retrieved 22 October 2011.
- Peter Atkins (1997). Physical Chemistry, 6th edition (W.H. Freeman and Company, New York).
- Vanýsek, Petr (2007). “Electrochemical Series”, in Handbook of Chemistry and Physics: 88th Edition (Chemical Rubber Company).
- A.E. Vogel, 1951, A textbook of Quantitative Inorganic Analysis, Longmans, Green and Co
- Carmo, M; Fritz D, Mergel J, Stolten D (2013). "A comprehensive review on PEM water electrolysis". Journal of Hydrogen Energy. doi:10.1016/j.ijhydene.2013.01.151.
- Werner Zittel; Reinhold Wurster (1996-07-08). "Chapter 3: Production of Hydrogen. Part 4: Production from electricity by means of electrolysis". HyWeb: Knowledge – Hydrogen in the Energy Sector. Ludwig-Bölkow-Systemtechnik GmbH.
- J. Levene; B. Kroposki, and G. Sverdrup (March 2006). "Wind Energy and Production of Hydrogen and Electricity – Opportunities for Renewable Hydrogen – Preprint" (PDF). National Renewable Energy Laboratory. Retrieved 2008-10-20.
- K. Bechgaard, K. Carneiro, F. B. Rasmusen, H. Olsen, G. Rindorf, C. S. Jacobsen, H. Pedersen, J. E. Scott (1981). "Superconductivity in an organic solid. Synthesis, structure, and conductivity of bis(tetramethyltetraselenafulvalenium) perchlorate, (TMTSF)2ClO4". Journal of the American Chemical Society 103 (9): 2440. doi:10.1021/ja00399a065.
- Williams, Jack M. Highly Conducting and Superconducting Synthetic Metals. Inorganic Syntheses [Online] 2007. 26, 386–394. doi:10.1002/9780470132579.ch70. | <urn:uuid:2d36866e-5914-4c54-b0e3-09bbbe1aef8a> | 3.6875 | 3,740 | Knowledge Article | Science & Tech. | 34.173056 |
Examples of Convergent Series
Today I want to give two examples of convergent series that turn out to be extremely useful for comparisons.
First we have the geometric series whose terms are the sequence for some constant ratio . The sequence of partial sums is
If we can multiply this sum by to find
Then as goes to infinity, this sequence either blows up (for ) or converges to (for ). In the border case we can also see that the sequence of partial sums fails to converge. Thus the geometric series converges if and only if , and we have a nice simple formula telling us the sum.
The other one I want to hit is the so-called -series, whose terms are starting at . Here we use the integral test to see that
so the sum and integral either converge or diverge together. If the integral gives , which converges for and diverges for .
If we get , which diverges. In this case, though, we have a special name for the limit of the difference . We call it “Euler’s constant”, and denote it by . That is, we can write
where is an error term whose magnitude is bounded by .
In general we have no good value for the sums of these series, even where they converge. It takes a bit of doing to find , as Euler did in 1735 (solving the “Basel Problem” that had stood for almost a century), and now we have values for other even natural number values of . The sum is known as Apéry’s constant, after Roger Apéry who showed that it was irrational in 1979. Yes, we didn’t even know whether it was a rational number or not until 30 years ago. We have basically nothing about odd integer values of .
If we say instead of , and let take complex values (no, I haven’t talked about complex numbers yet, but some of you know what they are) we get Riemann’s function , which is connected to some of the deepest outstanding questions in mathematics today. | <urn:uuid:aa068680-1dfe-4517-85d0-e67267d71f93> | 2.84375 | 431 | Personal Blog | Science & Tech. | 58.274542 |
Hubbert's Peak Mathematics
by Luís de Sousa
M. King Hubbert's early work was founded on somewhat
complex differential equations. That earned him some criticism; the method
was as impenetrable as a monolith, which only those with profound mathematical
knowledge could understand.
Based on population work from the 1960s decade, Hubbert presented in
his 1982 article "Techniques of Prediction as Applied to the
Production of Oil and Gas" an alternative method, much more
accessible. Such method is clearly described in Professor Kenneth Deffeyes'
book "Beyond Oil". What follows is an adaptation from
this book using data available on-line.
In order to determine the Hubbert's Peak one needs two sets of data,
annual production, called P, and the cumulative production, known
as Q. Let's start by applying this method to the lower 48 states
of USA which, as we know, passed their peak in 1971. Annual production
figures for these states are available in the
Energy Information Administration (EIA - Energy Information Administration)
web site. We can't find cumulative production here, but we can use
the value published in
ASPO's newsletter no. 23 that, for 2001, indicates a cumulative production
of 169 gigabarrels.
With the help of a calc sheet we can determine for each year the value
of P/Q. Next we can draw the graph of P/Q versus Q,
getting something like this:
For the first years there is some disorder, but from 1958 onwards the
dots take a negative trend towards the xx axis. Let us fit a
straight line to this set of dots from 1958 on, using this formula:
Y = mX + a
In this case Y is P/Q and X is Q,
a is the value P/Q gets when Q is zero and
m is the line's inclination. The line fitted to this dots has
a value of 0.061 for a and -3x10E-4 for m. With this
straight line we can find the value of Q for which P/Q
is zero, in this case 198.395, usually called Qt. This value
is the maximum cumulative production that will ever be achieved, knowing
that the peak occurs exactly amidst this total; we can easily put it in
1973, with 99.198 gigabarrels produced.
Hubbert's theory is simply the assumption that the relation between
P/Q and Q follows a straight line, all the rest is pure
mathematics. Let's resolve the line's equation in order to P
and see what appends:
P/Q = mQ + a
P/Q = -aQ/Qt + a
P/Q = a(1 - Q/Qt)
P = a(1 - Q/Qt)Q
The bit inside the parenthesis (1 - Q/Qt) is the fraction
of the total oil left to produce, meaning that the capacity we have to
produce oil at a given moment in time is linearly dependent on the amount
of oil still available to produce. The lowermost equation is a logistic
curve that stands a bell shape.
In order to get this curve we must use again our calc sheet. First of
all let's get the expression for 1/P:
1/P = 1/[a(1 - Q/Qt)Q]
With 1/P we now have years per gigabarrel instead of gigabarrel
per year. We go back to the calc sheet, and create a new column for Q
which we fill with 1 gigabarrels increment, starting in 1 and ending in
Qt. In another column we compute the value of 1/P and
in another P, using the expressions achieved before. Finally
we have to adjust Time in here, easy to do it knowing that by the end
of 2001 169 gigabarrels had been produced. We add another column and in
the line that Q stands 169 we insert 2002, for the other cells
of this new column we just add or subtract successively the values in
1/P. The result will be similar to this table:
All we need to do now is to draw the graph with Time in the xx
axis and P in the yy axis; we can add the original data
It's not bad, is it?
For the whole world we can use the data available in the
BP Statistical Review, that has production figures from 1965 to present.
Once more for the cumulative values we must recur to the
ASPO's newsletters, that for 2004 show a cumulative production of
1040 gigabarrels. The data we used for the US only yielded conventional
oil, the BP data also include oil sands, heavy oils and Liquefied Natural
Gas (LNG). Here's the P/Q versus Q graph:
Again we find the chaotic start, but after 1983 the dots align is a smooth
downward trend. Fitting a straight line as before we get this:
For this line the equation is P/Q = -2.36x10E-5 Q +
0.051, resulting in a value of 2164.86 for Qt. And the magic
is done; let's compute 1/P to get our beloved P versus
All of this to get the conclusion that applying Hubbert's method to
the data available until 2004 we have a production peak in 2006 Summer
Knowing how the Hubbert method works we can now understand the reasons
behind the different dates pointed to the Oil Peak . The differences are
mainly related with the data used:
- Considering only conventional oil we'll get the peak in 2004, as
indicated in the ASPO newsletters.
- Using all the production, but excluding tar sands and LNG, we get
the peak by the end of 2005. This is the data used by professor Deffeyes
in his book.
- As we saw before, using all the liquids we get the peak in the mid
of 2006. In older models this can turn out to be 2007, also small differences
in a or m can shift the peak some months.
- Studies that put the peak beyond 2010 do not use this method; usually
they consider the declining rates of existing fields and the projected
production of developing fields. These studies are often called bottom-up
- Last but not least, it is worth mentioning the model published by
ASPO, for all liquids, driven by Dr. Colin Campbell and the Uppsala
Hydrocarbon Depletion Study Group, lead by Professor Kjell Aleklett.
Presently the peak year is indicated to be 2010. This apparently results
from the combination of Hubbert's method with a bottom-up analysis,
considering a major development in deep-water exploration.
Of all these models, Professor Deffeyes' might be the most meaningful.
There's a lot of a difference between conventional oil and the rest, the
easiness with which is extracted from the soil. Global production can
continue to increase for some more years, but recurring to resources much
more difficult to explore, and much more expensive. Cheap oil might be
already a thing of the past.
In his book, Professor Deffeyes took the chance to create a symbolic
date to the Oil Peak , Thanksgiving 2005. It's the right time to thank
for a century and a half of cheap oil that Nature gave us. And it's also
the right time to once and for all face this challenge, undoubtedly the
greatest faced by Mankind.
For examples of the use of these techniques in a school or college situation, visit this US college page.
Luís de Sousa has a Portuguese
website on peak oil at | <urn:uuid:a8b8c121-1db2-4b5b-bc42-7da476e1d7bb> | 3.9375 | 1,658 | Nonfiction Writing | Science & Tech. | 64.268434 |
Science Fair Project Encyclopedia
Types of triangles
Triangles can be classified according to the relative lengths of their sides:
- In an equilateral triangle all sides are of equal length. An equilateral triangle is also equiangular, i.e. all its internal angles are equal—namely, 60°.
- In an isosceles triangle two sides are of equal length. An isosceles triangle also has two equal internal angles.
- In a scalene triangle all sides have different lengths. The internal angles in a scalene triangle are all different.
Triangles can also be classified according to the size of their largest internal angle, described below using degrees of arc.
- A right triangle (or right-angled triangle) has one 90° internal angle (a right angle). The side opposite to the right angle is the hypotenuse; it is the longest side in the right triangle. The other two sides are the legs of the triangle.
- An obtuse triangle has one internal angle larger than 90° (an obtuse angle).
- An acute triangle has internal angles that are all smaller than 90° (three acute angles).
Two triangles are said to be similar if and only if the angles of one are equal to the corresponding angles of the other. In this case, the lengths of their corresponding sides are proportional. This occurs for example when two triangles share an angle and the sides opposite to that angle are parallel.
In the remainder we will consider a triangle with vertices A, B and C, angles α, β and γ and sides a, b and c. The side a is opposite to the vertex A and angle α and analogously for the other sides.
|A triangle with vertices, sides and angles labelled|
In Euclidean geometry, the sum of the angles α + β + γ is equal to two right angles (180° or π radians). This allows determination of the third angle of any triangle as soon as two angles are known.
|The Pythagorean theorem|
A central theorem is the Pythagorean theorem stating that in any right triangle, the area of the square on the hypotenuse is equal to the sum of the areas of the squares on the other two sides. If vertex C is the right angle, we can write this as
- c2 = a2 + b2
This means that knowing the lengths of two sides of a right triangle is enough to calculate the length of the third—something unique to right triangles. The Pythagorean theorem can be generalized to the law of cosines:
- c2 = a2 + b2 - 2abcosγ
which is valid for all triangles, even if γ is not a right angle. The law of cosines can be used to compute the side lengths and angles of a triangle as soon as all three sides or two sides and an enclosed angle are known.
The law of sines states
where d is the diameter of the circumcircle (the smallest circle that completely contains the triangle within itself). The law of sines can be used to compute the side lengths for a triangle as soon as two angles and one side are known. If two sides and an unenclosed angle is known, the law of sines may also be used; however, in this case there may be zero, one or two solutions.
Points, lines and circles associated with a triangle
A perpendicular bisector of a triangle is a straight line passing through the midpoint of a side and being perpendicular to it, i.e. forming a right angle with it. The three perpendicular bisectors meet in a single point, the triangle's circumcenter; this point is the center of the circumcircle, the circle passing through all three vertices. The diameter of this circle can be found from the law of sines stated above.
Thales' theorem states that if the circumcenter is located on one side of the triangle, then the opposite angle is a right one. More is true: if the circumcenter is located inside the triangle, then the triangle is acute; if the circumcenter is located outside the triangle, then the triangle is obtuse.
An altitude of a triangle is a straight line through a vertex and perpendicular to (i.e. forming a right angle with) the opposite side. This opposite side is called the base of the altitude, and the point where the altitude intersects the base (or its extension) is called the foot of the altitude. The length of the altitude is the distance between the base and the vertex. The three altitudes intersect in a single point, called the orthocenter of the triangle. The orthocenter lies inside the triangle if and only if the triangle is not obtuse. The three vertices together with the orthocenter are said to form an orthocentric system.
An angle bisector of a triangle is a straight line through a vertex which cuts the corresponding angle in half. The three angle bisectors intersect in a single point, the center of the triangle's incircle. The incircle is the circle which lies inside the triangle and touches all three sides. There are three other important circles, the excircles; they lie outside the triangle and touch one side as well as the extensions of the other two. The centers of the in- and excircles form an orthocentric system.
A median of a triangle is a straight line through a vertex and the midpoint of the opposite side, and divides the triangle into two equal areas. The three medians intersect in a single point, the triangle's centroid. This is also the triangle's center of gravity: if the triangle were made out of wood, say, you could balance it on its centroid, or on any line through the centroid. The centroid cuts every median in the ratio 2:1, i.e. the distance between a vertex and the centroid is twice as large as the distance between the centroid and the midpoint of the opposite side.
The midpoints of the three sides and the feet of the three altitudes all lie on a single circle, the triangle's nine point circle. The remaining three points for which it is named are the midpoints of the portion of altitude between the vertices and the orthocenter. The radius of the nine point circle is half that of the circumcircle. It touches the incircle (at the Feuerbach point) and the three excircles.
The centroid (yellow), orthocenter (blue), circumcenter (green) and center of the nine point circle (red point) all lie on a single line, known as Euler's line (red line). The center of the nine point circle lies at the midpoint between the orthocenter and the circumcenter, and the distance between the centroid and the circumcenter is half that between the centroid and the orthocenter.
The center of the incircle is not in general located on Euler's line.
Computing the area of a triangle
Calculating the area of a triangle is an elementary problem encountered often in many different situations. Various approaches exist, depending on what is known about the triangle. What follows is a selection of frequently used formulae for the area of a triangle.
The area S of a triangle is S = ½bh, where b is the length of any side of the triangle (the base) and h (the altitude) is the perpendicular distance between the base and the vertex not on the base. This can be shown with the following geometric construction.
The triangle is first transformed into a parallelogram
To find the area of a given triangle (green), first make an exact copy of the triangle (blue), rotate it 180°, and join it to the given triangle along one side to obtain a parallelogram. Cut off a part and join it at the other side of the parallelogram to form a rectangle. Because the area of the rectangle is bh, the area of the given triangle must be ½bh.
The area of the parallelogram is the magnitude
The area of a parallelogram can also be calculated by the use of vectors. If AB and AC are vectors pointing from A to B and from A to C, respectively, the area of parallelogram ABDC is |AB × AC|, the magnitude of the cross product of vectors AB and AC. |AB × AC| is also equal to |h × AC|, where h represents the altitude h as a vector.
The area of triangle ABC is half of this, or S = ½|AB × AC|.
Applying trigonometry to
The altitude of a triangle can be found through an application of trigonometry. Using the labelling as in the image on the right, the altitude is h = a sin γ. Substituting this in the formula S = ½bh derived above, the area of the triangle can be expressed as S = ½ab sin γ.
It is of course no coincidence that the area of a parallelogram is ab sin γ.
If vertex A is located at the origin (0, 0) of a Cartesian coordinate system and the coordinates of the other two vertices are given by B = (x1, y1) and C = (x2, y2), then the area S can be computed as 1/2 times the absolute value of the determinant
or S = ½ |x1y2 − x2y1|.
Using Heron's formula
Yet another way to compute S is Heron's formula:
where s = ½ (a + b + c) is the semiperimeter, or one half of the triangle's perimeter.
Using the side lengths and a numerically stable formula
The brackets in the above formula are required in order to prevent numerical instability in the evaluation.
If any four of a triangle's elements (vertices, and/or elements of its sides) are plane to each other, the triangle is called plane. Geometers also study non-planar triangles, for instance spherical in spherical geometry and hyperbolic triangles in hyperbolic geometry.
- Synthetic geometry
- Pedoe's inequality
- Triangle inequality
- Spherical triangle
- Pythagorean theorem
- Pons Asinorum
- Malfatti circles
- Desargues' theorem
- Triangle Calculator - solves for remaining sides and angles when given three sides or angles, supports degrees and radians.
- Napoleon's theorem A triangle with three equilateral triangles. A purely geometric proof. It uses the Fermat point to prove Napoleon's theorem without transformations by Antonio Gutierrez from "Geometry Step by Step from the Land of the Incas"
- William Kahan: Miscalculating Area and Angles of a Needle-like Triangle.
- Clark Kimberling: Encyclopedia of triangle centers. Lists some 1600 interesting points associated with any triangle.
- Christian Obrecht: Eukleides. Software package for creating illustrations of facts about triangles and other theorems in Euclidean geometry.
- Triangle constructions, remarkable points and lines, and metric relations in a triangle. From Interactive Mathematics Miscellany and Puzzles.
- Printable Worksheet on Types of Triangles
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:8f32418c-1ae0-4bef-89b8-d0ae1306c0bf> | 4.4375 | 2,372 | Knowledge Article | Science & Tech. | 50.990021 |
An important service provided by invertebrates is waste recycling - making minerals and organic material available again to plants and other animals. In the soil earthworms and other invertebrates play crucial roles in the decomposition of organic matter. Their activities improve the drainage, aeration and composition of the soil, thus enabling plant growth. The decomposition of dead plants and animals including dung and fallen wood relies upon invertebrates.
|Hibernating earthworm © Roger Key|
Basis of ecosystems
Most marine habitats are dominated by invertebrates. In some cases, such as Flameshell reefs (Limaria hians) and Northern sea fan (Swiftia pallida) and sponge communities, the entire habitat is based on invertebrates. Birds and fish rely on these invertebrates for food and the abundance and diversity of marine plankton is a useful indicator of healthy marine ecosystems.
Many plants rely on insects to pollinate their flowers and so complete their reproductive cycle. Well-known pollinators include bumblebees, honeybees, butterflies and hoverflies, less well known ones include moths, thrips, beetles and solitary bees.
|Hive bee © Alan Stubbs|
Invertebrates form the basis of numerous food chains. Many birds feed on invertebrates, whether as food for their chicks or as part of their adult diet. Migrant birds such as swallows, swifts and martins travel long distances to feed on insects in the British Isles. The chicks of Blue tits eat an estimated 35 billion caterpillars and other small invertebrates every year. A number of uplands birds, such as Golden plovers and Greenshanks time their breeding to coincide with the emergence of craneflies, which form the majority of the diet of their chicks. Baleen whales such as the Minke whale and many seabirds feed extensively on Krill (Euphausia superba) and other marine crustaceans. The diet of Puffins primarily consists of Sand eels, which in turn feed upon planktonic species of crustacean and other invertebrates. Mammals such as bats, badgers, voles and shrews also feed on invertebrates. It is estimated that a single Pipistrelle bat will consume over 3,000 small insects every night. In freshwater ecosystems the diet of game fish such as the Atlantic salmon and Brown/Sea trout is comprised entirely of aquatic invertebrates. Birds such as the Dipper and Grey Wagtail also depend upon aquatic invertebrates in our rivers and streams.
There is a long history of invertebrates being used as indicators of the health of our environment. In determining the quality of our rivers and lochs, the Scottish Environment Protection Agency routinely use assessments of the number and variety of aquatic invertebrates alongside chemical analyses. Invertebrates are also used to test the toxicity of chemicals such as pesticides.
Assessing habitat quality
Since 1979 the UK butterfly monitoring scheme has been recording trends in butterfly species. The information gathered plays an important role in assessing habitat diversity, habitat fragmentation and the impacts of climate and other environmental change. Through the Rothamsted light-trap network, which started in 1965, we know that about two-thirds of moth species are declining, and about 20% of all species are declining sharply.
|Chequered skipper © Martin Warren|
The Scottish Agricultural Science Agency monitors aphid populations as part of the Rothamsted suction trap network which has been in operation since 1965. The information from this network is used to study the factors affecting the dynamics of aphid populations and to guide aphid control decisions.
In agricultural systems, simple measures such as conserving headlands and making ‘beetle banks’ encourage predatory invertebrates such as beetles and hoverflies, which not only help to control pests but also provide additional food for birds and mammals.
In addition, pests can be individually targeted with specific invertebrate enemies like native ladybirds and parasitoid wasps. Increasingly these are available commercially and they may offer an environmentally friendly option to chemical control. | <urn:uuid:f474be67-3b56-46a4-940e-1862406aebcc> | 3.859375 | 844 | Knowledge Article | Science & Tech. | 24.522548 |
This graphic shows an exotic object in our galaxy called SGR 0418+5729 (SGR 0418 for short). As described in our press release, SGR 0418 is a magnetar, a type of neutron star that has a relatively slow spin rate and generates occasional large blasts of X-rays.
The only plausible source for the energy emitted in these outbursts is the magnetic energy stored in the star. Most magnetars have extremely high magnetic fields on their surface that are ten to a thousand times stronger than for the average neutron star. New data shows that SGR 0418 doesn't fit that pattern. It has a surface magnetic field similar to that of mainstream neutron stars.
What are digital stories and how do you tell them? At a recent exhibit at Brown University, that topic was examined in a few different ways. One of the stories shown was a large screen version of images and text selected out of the "From Earth to the Universe" (FETTU) collection. FETTU is a Chandra-led project of astronomical image exhibits that began in the International Year of Astronomy in 2009 but has remained as a legacy project of public science. The location types of the FETTU exhibits have ranged from cafes to malls to metros.
Exhibiting FETTU with Brown University's large visualization wall in the Rockefeller library offered a special opportunity to display ultra-large astronomy data sets on a huge screen that lets the viewer not only see details in the images that are hard to see on small screens but also helps the viewer feel somewhat immersed in the image. The science images included Chandra’s composite with Hubble and Spitzer of the galactic center, a recent Solar Dynamics Observatory image of our Sun (shown here), an image of Mount Sharp, Mars from the Curiosity mission, and 5 other objects.
This composite image of a galaxy illustrates how the intense gravity of a supermassive black hole can be tapped to generate immense power. The image contains X-ray data from NASA's Chandra X-ray Observatory (blue), optical light obtained with the Hubble Space Telescope (gold) and radio waves from the NSF's Very Large Array (pink).
Recently, the Fermi team announced that the spacecraft dodged a very large bullet in the form of a defunct Soviet spy satellite: http://www.nasa.gov/mission_pages/GLAST/news/bullet-dodge.html. The close encounter with Cosmos 1805 was reminder that even though space is very large, there are some real threats to our invaluable telescopes that are in orbit.
Scientists have used Chandra to make a detailed study of an enormous cloud of hot gas enveloping two large, colliding galaxies. This unusually large reservoir of gas contains as much mass as 10 billion Suns, spans about 300,000 light years, and radiates at a temperature of more than 7 million degrees.
The Small Magellanic Cloud (SMC) is one of the Milky Way's closest galactic neighbors. Even though it is a small, or so-called dwarf galaxy, the SMC is so bright that it is visible to the unaided eye from the Southern Hemisphere and near the equator. Many navigators, including Ferdinand Magellan who lends his name to the SMC, used it to help find their way across the oceans.
An interdisciplinary and international group from Chandra, the Smithsonian Astrophysical Observatory, and experts in the field of aesthetics from the University of Otago, New Zealand, formed the Aesthetics and Astronomy group - known as the A&A project -- back in 2008 to explore how astronomy images are perceived.
Amanda Berry, an MFA graduate student at Kendall College of Art and Design in Michigan, is researching "space" as a visual knowledge field. She asked some great questions to the Aesthetics & Astronomy project, which Jeffrey Smith kindly answered. We thought you might enjoy the read:
Note: An earlier version of this article appeared on this blog by Peter Edmonds.
The collapse of a massive star in a supernova explosion is an epic event. In less than a second a neutron star (or in some cases a black hole) is formed and the implosion is reversed, releasing prodigious amounts of light that can outshine billions of Suns. That is a spectacular way to be born. Here, I'll explain that the properties of neutron stars are no less spectacular, even though they are not as famous as their collapsed cousins, black holes.
Because of the incredible pressures involved in core collapse, the density of neutron stars is astounding: all of humanity could be squashed down to a sugar cube-sized piece of neutron star. The escape velocity from their surface is over half the speed of light but an approaching rocket ship would be stretched, then crushed and assimilated into the surface of the star in a moment. Resistance would be futile.
Paul Green is an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. His scientific research includes the study of quasars and carbon stars. He pursues these topics while working in Chandra's Director's Office, helping to ensure that the science of the telescope gets done smoothly. When he's not doing all of these things, Paul is also known to play a mean bass guitar.
Please note this is a moderated blog. No pornography, spam, profanity or discriminatory remarks are allowed. No personal attacks are allowed. Users should stay on topic to keep it relevant for the readers.
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Climate Change Reducing Ocean's Carbon Dioxide Uptake, New Analysis Shows
ScienceDaily (July 11, 2011) — How deep is the ocean's capacity to buffer against climate change?
As one of the planet's largest single carbon absorbers, the ocean takes up roughly one-third of all human carbon emissions, reducing atmospheric carbon dioxide and its associated global changes.
But whether the ocean can continue mopping up human-produced carbon at the same rate is still up in the air. Previous studies on the topic have yielded conflicting results, says University of Wisconsin-Madison assistant professor Galen McKinley.
In a new analysis published online July 10 in Nature Geoscience, McKinley and her colleagues identify a likely source of many of those inconsistencies and provide some of the first observational evidence that climate change is negatively impacting the ocean carbon sink.
"The ocean is taking up less carbon because of the warming caused by the carbon in the atmosphere," says McKinley, an assistant professor of atmospheric and oceanic sciences and a member of the Center for Climatic Research in the Nelson Institute for Environmental Studies.
The analysis differs from previous studies in its scope across both time and space. One of the biggest challenges in asking how climate is affecting the ocean is simply a lack of data, McKinley says, with available information clustered along shipping lanes and other areas where scientists can take advantage of existing boat traffic. With a dearth of other sampling sites, many studies have simply extrapolated trends from limited areas to broader swaths of the ocean.
McKinley and colleagues at UW-Madison, the Lamont-Doherty Earth Observatory at Columbia University, and the Universite Pierre et Marie Curie in Paris expanded their analysis by combining existing data from a range of years (1981-2009), methodologies, and locations spanning most of the North Atlantic into a single time series for each of three large regions called gyres, defined by distinct physical and biological characteristics.
They found a high degree of natural variability that often masked longer-term patterns of change and could explain why previous conclusions have disagreed. They discovered that apparent trends in ocean carbon uptake are highly dependent on exactly when and where you look -- on the 10- to 15-year time scale, even overlapping time intervals sometimes suggested opposite effects.
Article continues: http://www.sciencedaily.com/releases/2011/07/110710132816.htm | <urn:uuid:579fe3d7-10c3-43ff-b125-a99dc6d3fd46> | 3.359375 | 491 | Truncated | Science & Tech. | 21.615527 |
dielectric (dĪˌĭlĕkˈtrĭk) [key], material that does not conduct electricity readily, i.e., an insulator (see insulation). A good dielectric should also have other properties: It must resist breakdown under high voltages; it should not itself draw appreciable power from the circuit; it must have reasonable physical stability; and none of its characteristics should vary much over a fairly wide temperature range. One important application of dielectrics is as the material separating the plates of a capacitor. A capacitor with plates of a given area will vary in its ability to store electric charge depending on the material separating the plates. On the basis of this variation each insulating material can be assigned a dielectric constant. Generally, the dielectric constant of air is defined as 1 and other dielectric constants are determined with reference to it. Other properties of interest in a dielectric are dielectric strength, a measure of the maximum voltage it can sustain without significant conduction, and the degree to which it is free from power losses.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
More on dielectric from Fact Monster:
See more Encyclopedia articles on: Electrical Engineering | <urn:uuid:859c3845-d708-4d1b-8e94-4a3020684952> | 3.921875 | 267 | Knowledge Article | Science & Tech. | 24.612019 |
The Chesapeake Bay and its tidal tributaries are home to dozens of species of algae. Along with certain bacteria, they release oxygen and, as primary producers, form the foundation of the Bay’s food web.
Soaking up sunlight and taking in nutrients from the water, algae comprise the broadest base of Chesapeake Bay’s food web. Non-vascular, and lacking traditional leaf-stem-root systems, these plants range from microscopic phytoplankton to highly visible green algae such as Ulva (sea lettuce).
As food for grazing plankton, fish, and their predators, algae are the force behind all life in the Bay. Without them there’d be no blue crabs, no striped bass, no seabirds. In turn, algae need sunlight, carbon dioxide, and nutrients such as nitrogen and phosphorus to carry out their life’s work: producing oxygen and glucose through photosynthesis.
In early spring, increases in sunlight and nutrients fuel blooms of phytoplankton — including photosynthesizing dinoflagellates and diatoms. These single-celled organisms are often classified as algae since many — though not all — contain chloroplasts, the chlorophyll-containing cell organelle that spurs photosynthesis in all plants.
Dinoflagellates have whip-like flagella that allow them to move through the water and hunt prey — about half of all dinoflagellates must feed on other organisms for nourishment (and are therefore called heterotrophic).
Conversely, almost all diatoms are capable of making their own food through photosynthesis (and are therefore called autotrophic). Unlike dinoflagellates, they float in the water with no means of propulsion. Encased by a silica wall that resembles glass, they take on beautiful and varied shapes visible only under a microscope.
Scientists study the relative abundance of dinoflagellates, diatoms, and other algae in the Chesapeake to glean insight into the overall health and productivity of the Bay.
When algae bloom in over-abundance due to excess nutrients, they can throw the Bay out of balance, robbing bottom waters of life-sustaining oxygen. Some algae can even be toxic leading to both environmental and human health issues. | <urn:uuid:c60232ba-00e9-4390-9cd4-383ed9d6edfc> | 4.15625 | 485 | Knowledge Article | Science & Tech. | 31.098449 |
Barbary macaques, Macaca sylvanus, are large Old World monkeys found in mountainous regions of Algeria and Morocco and on Gibraltar.
The population of Barbary macaques is declining and they are becoming a threatened species. Numbers are falling because the Barbary macaques are losing their habitat to human activity such as logging and overgrazing.
Barbary macaques are the only living macaque found outside Asia and the only African primate found north of the Sahara (other than humans).
Learn about the appearance of Barbary macaques and the evolutionary history of the species, which dates back to Africa around 7 million years ago.
Discover where in the world Barbary macaques can be found and learn about the type of habitat they live in.
Get information regarding the size and life expectancy of Barbary macaques.
Barbary macaques live in groups averaging 27 individuals and they have a diverse range of facial and visual expressions to help communicate with each other. Find out more about the behaviour of Macaca sylvanus.
Discover why Macaca sylvanus is now a threatened species.
Get reference material for Macaca sylvanus.
Barbary macaques are the only living macaque found outside Asia.
Morphological evidence suggests an early divergence of Macaca sylvanus from other extant macaques.
The Rock of Gibraltar - a large and long-established semi-wild colony of Barbary macaques is present on Gibraltar.
Barbary macaques can live for up to 30 years.
Data on the reproductive parameters of a semi free-ranging population of Barbary macaques revealed a strongly seasonal distribution of births, with birth taking place between mid-March and the beginning of August.
Barbary macaques have a diverse range facial and visual expressions for communicating.
Barbary Macaques are a threatened species. | <urn:uuid:b6455220-8704-4bce-b45d-64c543dbf346> | 3.9375 | 384 | Knowledge Article | Science & Tech. | 22.333333 |
It's a theoretical concept. I haven't seen an actual MAV example that demonstrates this but I'm woefully lacking in following MAV development
so take my comment with a grain of salt.
Conceptually a fixed wing MAV will have a harder time maneuvering in confined indoors spaces because of the airspeed or wing span & surface area needed for very low speed flight. Contrast to that of a small bird or insect that easily maneuvers in confined spaces at very low forward airspeeds and even hovers. So the idea is that a MAV based on the same principles flight principles of birds or insects would be more agile in that respect vs. a conventional wing.
Here are a couple of papers on the topic:
Flapping flight is quite complicated to describe. But consider the following difference to expound a bit more on the concept above.
Fixed wing aircraft get their primary lift generation as function of forward airspeed and amount of wing span & surface area. (Yes angle of attack is a part of it but the amount of aoa needed is a function of the airspeed.) For MAV flying in confined spaces very slow speeds are needed to avoid running into obstacles. The only way to do that with a fixed wing MAV to reduce it's flyable forward airspeed is to increase the size of the wing. As you can see this is a self defeating proposition - we have to make a larger MAV to fly in smaller spaces. Hmmm.
Flapping wings get their lift not from forward airspeed of the aircraft but from flapping motion of the wing. Because of this there is less reliance on forward airspeed to generate lift and the amount of lift (and thrust) generated can be controlled by how fast the wings beat. This conceptually solves the issue for a fixed wing MAV trying to fly at very slow airspeeds or even hover. | <urn:uuid:534b552f-8b0f-45e2-940f-10a987b5744a> | 2.75 | 382 | Comment Section | Science & Tech. | 57.475019 |
Applying physics to put out a fire, as opposed to chemistry, is an idea DARPA has been eyeing for a while, and it might lead to military devices that can better snuff out fires in enclosed places. Now they have demonstrated a new device in action.
In the video, two speakers are placed on either side of a fuel source. The sound increases air velocity, which disrupts the flame. It also causes higher fuel vaporization, which increases the flame's area while dropping its temperature. That thinning causes a problem in the combustion process.
It looks like an interesting project, but even DARPA admits they aren't sure how they'll use it. To make it worthwhile, it would have to operate on a much larger scale. They're hoping instead that the project will inspire other ideas in the field, so soak in the video in case it's the last you see of the technique.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more. | <urn:uuid:b825374a-36d7-43b9-b330-694d2a00dd1a> | 3.109375 | 238 | Truncated | Science & Tech. | 54.712455 |
Site for the Platte River Program in Nebraska an area that is a critical staging area for migratory waterbirds of the Central Flyway. Includes links to color-infrared aerial photos, 1938 historic aerial photos, and Cottonwood Ranch research site.
The Raptor Information System (RIS) collection and bibliographic database have been transferred to The Peregrine Fund. The RIS records are being subsumed into the bibliography posted on the website of the Global Raptor Information Network (GRIN).
One of the greatest challenges for conserving grassland, prairie scrub, and shrub-steppe ecosystems is maintaining prairie dog populations across the landscape. Of the four species of prairie dogs found in the United States, the Utah prairie dog (Cynomys
Webpage on research on sea otters (Euhydra lutris) in the nearshore environment of the eastern Pacific Ocean with information on status of otters on the coast of Alaska, Washington, and California and link to fact sheet in PDF format.
Report prepared for the U.S. Fish and Wildlife Service with descriptions of exotic aquatic species introduced in the southeast United States with information on populations, geographic distribution, and origins.
Report on the population of northern pintails between 1979 and the 1990s in Sacramento Valley, California, including methods of study including radio telemetry, causes of mortality, morphometrics, survival rates, and management implications.
Report on the captive breeding program at Patuxent Wildlife Research Center to help save endangered whooping cranes. Site links to natural history information on whooping cranes, why they are endangered, cool facts on cranes, and a photo gallery.
Review of current research on stock assessment of the Pacific walrus in the Chukchi and Bering Seas and interactions between walruses and their environment with links to walrus taxonomy, distribution, behavior, and relation to man
Shooting them doesn't work, they just breed more. And they trample on the native plants. These animals were brought to the islands during the last 150 years, and we're trying to develop ways of managing their impact on the native life. | <urn:uuid:ecd93e3b-4eba-462c-8f25-4742c35a39c2> | 2.921875 | 443 | Content Listing | Science & Tech. | 28.527968 |
Tiny soot particles given off in the smoke from fires can be lofted high into the atmosphere. These soot, or "black carbon", particles influence Earth's climate. They absorb incoming sunlight high in the atmosphere, heating the atmosphere while also cooling Earth's surface beneath because of the decrease in solar energy that reaches the planet's surface. The soot particles can also serve as cloud condensation nuclei - the "seeds" around which water droplets in clouds condense - and in so doing further influence climate by fostering the formation of clouds that would not otherwise develop. Such soot comes from both natural sources, such as wildfires, and from human-generated sources, such as coal-fired power plants or internal combustion engines in cars and trucks. In this case, the smoke is from oil well fires in Kuwait in the wake of the 1991 war in the Persian Gulf.
Image courtesy of the University Corporation for Atmospheric Research. | <urn:uuid:66261374-9acf-4a96-8ac4-135ada4bc63f> | 3.921875 | 189 | Knowledge Article | Science & Tech. | 39.961154 |
In 1960, the Pasadena, California-based Jet Propulsion Laboratory (JPL), a spaceflight engineering laboratory managed by California Institute of Technology on contract to NASA, commenced study of Voyager, a robotic spacecraft program for exploring Mars and Venus in the late 1960s and 1970s. NASA Headquarters formally approved Voyager in 1964. Cuts in NASA’s space science budget, debate over how Voyager should be managed and launched, and new Mars atmosphere data from the Mariner IV flyby (July 1965) delayed NASA’s push for formal Voyager start-up until January 1967, when President Lyndon Johnson’s Fiscal Year (FY) 1968 NASA budget called for $71.5 million for the new program.
In January 1967, NASA’s Office of Space Science and Applications published a 26-page brochure as part of its efforts to move Voyager from planning to development. It constituted an introduction (and sales pitch) aimed at members of Congress and other individuals who would need to support Voyager if it would become part of NASA’s approved program for the 1970s.
In the brochure’s foreword, Homer Newell, NASA Associate Administrator for Space Science and Applications, explained that Voyager’s chosen launch vehicle was the “awe-inspiring” Saturn V. One three-stage Saturn V rocket would launch two 12-ton Voyager spacecraft toward Mars. For comparison, Mariner IV, launched on an Atlas-Agena D rocket in November 1964, had had a mass of only 574 pounds. Newell wrote that
Successes already achieved in the 1960s with unmanned spacecraft of limited weight and power. . .foretell the great work of exploration that lies ahead. . .With Voyager, the U.S. capability for planetary exploration will grow by several orders of magnitude. . .Voyager could well be the means by which man first learns of extraterrestrial life. Continue Reading “The First Voyager (1967)” » | <urn:uuid:06107655-822a-4807-8dc4-dfaaa044f3a6> | 3.4375 | 405 | Truncated | Science & Tech. | 49.779989 |
Updating Magic Universe
Debris traces the solar magnetic field
What started as a bonanza for comet spotters becomes a new tool for exploring levels in the Sun’s atmosphere that have been hard to see up to now. The SOHO spacecraft (Solar and Heliospheric Observatory) has identified more than 1400 small “sungrazing” comets that fly close to the Sun and evaporate. In July last year, the comet observers using SOHO’s Large Angle and Spectrometric Coronagraph (LASCO) team alerted colleagues operating the newer SDO (Solar Dynamics Observatory) to a larger-than-usual sungrazer heading for its doom.
As he reports in the current issue of Science magazine, Karel Schrijver from the Lockheed Martin Advanced Technology Center in California tracked Comet 2011 N3 SOHO by extreme ultraviolet light with his Atmospheric Imaging Assembly on SDO, which observes highly ionized atoms. What he learned about the comet and about the Sun I’ll tell below as a concise update for Magic Universe. Meanwhile the word is that SDO also observed Comet Lovejoy last month, when it survived a close encounter with the Sun, passing behind it and reappearing on the other side.
Here are a few relevant paragraphs from my story about Comets and Asteroids in Magic Universe.
The big comet count came from another instrument on SOHO, called LASCO, developed under US leadership. Masking the direct rays of the Sun, it kept a constant watch on a huge volume of space around it, looking out primarily for solar eruptions. But it also saw comets when they crossed the Earth-Sun line, or flew very close to the Sun.
A charming feature of the SOHO comet watch was that amateur astronomers all around the world could discover new comets, not by shivering all night in their gardens but by checking the latest images from LASCO. These were freely available on the Internet. And there were hundreds to be found, most of them small ‘sungrazing’ comets, all coming from the same direction. They perished in encounters with the solar atmosphere, but they were related to larger objects on similar orbits that did survive, including the Great September Comet (1882) and Comet Ikeya-Seki (1965).
‘SOHO is seeing fragments from the gradual break-up of a great comet, perhaps the one that the Greek astronomer Ephorus saw in 372 BC,’ explained Brian Marsden of the Center for Astrophysics in Cambridge, Massachusetts. ‘Ephorus reported that the comet split in two. This fits with my calculation that two comets on similar orbits revisited the Sun around AD 1100. They split again and again, producing the sungrazer family, all still coming from the same direction.’
The progenitor of the sungrazers must have been enormous, perhaps 100 kilometres in diameter or a thousand times more massive than Halley’s Comet. Not an object you’d want the Earth to tangle with. Yet its most numerous offspring, the SOHO-LASCO comets, are estimated to be typically only about 10 metres in diameter.
Update January 2012
In July 2011 a larger than usual sungrazer spotted by SOHO was tracked across the face of the Sun by a newer spacecraft, the Solar Dynamics Observatory, SDO. Named as Comet 2011 N3 SOHO, it evaporated to the point of invisibility after 20 minutes, but not before the event had transformed the game from comet-spotting fun to highly productive cometary and solar physics.
Led by Karel Schrijver from the Lockheed Martin Advanced Technology Center in California, the SDO team was able to gauge the size of the comet. Initially it was up to 50 metres wide. This opened the way to investigating the sungrazers in much more detail. It should become possible to learn more about the composition of these comets, according to how they boil and rupture in the intense heat.
As for solar physics, the miniature tail of the dying comet lit up magnetic field lines at altitudes high in the solar atmosphere that otherwise are almost impossible to detect. Seeing the lines traced by sungrazers at different heights above the Sun will make it possible to trace more accurately the links between the magnetism near the visible surface and the vast field that reaches out into space and influences the Earth.
Karel Schrijver et al., Science 20 January 2012, vol. 335, pp. 324-328 DOI: 10.1126/science.1211688
NB: Movies are available at http://www.sciencemag.org/content/335/6066/324/suppl/ | <urn:uuid:ea220d77-1a19-4de4-9a75-93257874dd1b> | 2.984375 | 984 | Personal Blog | Science & Tech. | 43.629591 |
Ammonite identification is, by all accounts, a tricky beast. Donovan et al. (1980) admitted that "Students tell us in their essays that one of the desirable attributes of a zonal fossil is that it should be easily recognizable. Most ammonites are not". Ammonites as a whole are readily distinguished from other shelled cephalopods by the ridiculously complex sutures separating chambers. However, lineages of ammonites in different periods and times often converged with each other in their morphology and successful identification often requires, in addition to simple morphology, consideration of such matters as geographical provenance and the nature of forms found in contiguous strata. And quite frankly, I'll be buggered if I've got the intellect to distinguish most of them.
That carping aside, the Arctocephalitinae were a subfamily of ammonites restricted to the region of the modern Arctic Ocean during the middle part of the Jurassic. Arctocephalitines are represented by an extensive fossil record found in localities such as Greenland, northern Canada and Siberia which have allowed a reasonable degree of success in tracing their lineages. The Arctocephalitinae are the basal radiation of the family Cardioceratidae, arising from early Sphaeroceratidae during the latter half of the Bajocian epoch; the subfamily Cadoceratinae was derived from within the Arctocephalitinae during the succeeding Bathonian and would itself give rise in turn to the Cardioceratinae (Donovan et al., 1980; ammonite researchers have so far been unimpressed by arguments for strict monophyly as a guiding principle in classification). The cadoceratines would outdo their arctocephalitine forebears by spreading beyond the Boreal region.
During the period of the earliest two genera of Arctocephalitinae, Cranocephalites and its descendant Arctocephalites, the subfamily had the Arctic to itself; no other ammonite families had reached the largely isolated ocean (Navarro et al., 2005). The arctocephalitines were largely laterally compressed with deep angular whorls (discocones). Things changed with the arrival of another family, the similarly discoconic Kosmoceratidae, in the Arctic Basin around the time of the origin of the third main arctocephalitine genus, Arcticoceras. The arrival of the kosmoceratids seems to have provided a competitive impetus to arctocephalitine evolution: the overall disparity in the family decreased and they were pushed out of the discocone niche. Instead, the succeeding cadoceratines were initially cadicones with broad shallow whorls though some cadoceratines returned to a discocone form after leaving the Arctic Basin.
Donovan, D. T., J. H. Callomon & M. K. Howarth. 1980. Classification of the Jurassic Ammonitina. In: House, M. R., & J. R. Senior (eds) The Ammonoidea pp. 101-155. Academic Press: London & New York.
Mitta, V. V. 2005. Late Bathonian Cardioceratidae (Ammonoidea) from the middle reaches of the Volga River. Paleontological Journal 39 (Suppl. 5): S629-S644.
Navarro, N., P. Naige & D. Marchand. 2005. Faunal invasions as a source of morphological constraints and innovations? The diversification of the early Cardioceratidae (Ammonoidea; Middle Jurassic). Paleobiology 31 (1): 98-116.
Poulton, T. P. 1987. Zonation and correlation of Middle Boreal Bathonian to Lower Callovian (Jurassic) ammonites, Salmon Cache Canyon, Porcupine River, northern Yukon. Geological Survey of Canada Bulletin 358: 1-155.
Rawson, P. F. 1982. New Arctocephalitinae (Ammonoidea) from the Middle Jurassic of Kong Karls Land, Svalbard. Geological Magazine 119: 95-100. | <urn:uuid:c61384b2-34f4-47e1-a6d2-2dfeac05741e> | 3.78125 | 893 | Academic Writing | Science & Tech. | 26.325593 |
First, we need to establish some terminology.
a chunk of text that a user enters on the command-line, and that the
shell passes to execl() or execv(). In
Python, arguments are elements of
sys.argv is the name of the program
being executed; in the context of parsing arguments, it's not very
important.) Unix shells also use the term ``word''.
It is occasionally desirable to use an argument list other than
sys.argv[1:], so you should read ``argument'' as ``an element of
sys.argv[1:], or of some other list provided as a substitute for
an argument used to supply extra information to guide or customize
the execution of a program. There are many different syntaxes for
options; the traditional Unix syntax is - followed by a
single letter, e.g. -x or -F. Also,
traditional Unix syntax allows multiple options to be merged into a
single argument, e.g. -x -F is equivalent to
-xF. The GNU project introduced --
followed by a series of hyphen-separated words,
e.g. --file or --dry-run. These are
the only two option syntaxes provided by optparse.
Some other option syntaxes that the world has seen include:
- a hyphen followed by a few letters, e.g. -pf (this is
not the same as multiple options merged into a single
- a hyphen followed by a whole word, e.g. -file (this is
technically equivalent to the previous syntax, but they aren't
usually seen in the same program.)
- a plus sign followed by a single letter, or a few letters,
or a word, e.g. +f, +rgb.
- a slash followed by a letter, or a few letters, or a word, e.g.
optparse does not support these option syntaxes, and it never
will. (If you really want to use one of those option syntaxes, you'll
have to subclass OptionParser and override all the difficult
bits. But please don't! optparse does things the traditional
Unix/GNU way deliberately; the first three are non-standard anywhere,
and the last one makes sense only if you're exclusively targeting
MS-DOS/Windows and/or VMS.)
- option argument
an argument that follows an option, is closely associated with that
option, and is consumed from the argument list when the option is.
Often, option arguments may also be included in the same argument as
the option, e.g. :
may be equivalent to:
(optparse supports this syntax.)
Some options never take an argument. Some options always take an
argument. Lots of people want an ``optional option arguments'' feature,
meaning that some options will take an argument if they see it, and
won't if they don't. This is somewhat controversial, because it makes
parsing ambiguous: if -a and -b are both
options, and -a takes an optional argument, how do we
interpret -ab? optparse does not support optional
- positional argument
something leftover in the argument list after options have been
parsed, i.e., after options and their arguments have been parsed and
removed from the argument list.
- required option
an option that must be supplied on the command-line. The phrase
``required option'' is an oxymoron; the presence of ``required options''
in a program is usually a sign of careless user interface design.
optparse doesn't prevent you from implementing required
options, but doesn't give you much help with it either. See ``Extending
Examples'' (section 6.20.5) for two ways to
implement required options with optparse.
For example, consider this hypothetical command-line:
prog -v --report /tmp/report.txt foo bar
-v and --report are both options. Assuming
the --report option takes one argument,
/tmp/report.txt is an option argument.
are positional arguments.
See About this document... for information on suggesting changes. | <urn:uuid:a03d71d6-1070-4e53-a9c8-b676e99c35bb> | 3.515625 | 895 | Documentation | Software Dev. | 57.350161 |
Today's mad science involves the creation of modified cells. Cells stronger than their original material.
It's a Gothic thing, say the scientists:
Researcher Bryan Kaehr, a Sandia scientist, provided what could be the first ever scientific distinction made between a “mummy” and “zombie” cell.
“King Tut was mummified,” said Kaehr, “to approximately resemble his living self, but the process took place without mineralization [a process of fossilization]. Our zombie cells bridge chemistry and biology to create forms that not only near-perfectly resemble their past selves, but can do future work.”
How does this really work? By
placing free-floating mammal cells into a petri dish and coating them with a silicic acid solution. For reasons that the study says are still “partially unclear,” the silicic acid enters and embalms every organelle in the cells.
The result is super-strong. Better than the original. Waiting to be used in world domination a story.
(thanks to Jesse Walker) | <urn:uuid:21adf34d-3306-4e12-8370-db64be9e2131> | 3.125 | 236 | Personal Blog | Science & Tech. | 50.099485 |
A significant population of Florida’s manatees (Trichechus manatus latirostris) occurs in southwest Florida, including extensive protected areas within the Ten Thousand Islands (TTI) and Everglades National Park (ENP). In this wilderness area, manatees are frequently seen using offshore seagrass beds, estuarine bays, tidal creeks, and rivers. Upstream from these relatively undisturbed ecosystems, humans have greatly modified the natural hydrologic patterns through extensive systems of canals, ditches, weirs, roads, and culverts. Historically, water moved across this landscape gradually as sheetflow, but human structures now rapidly drain the landscape, resulting in large pulses of freshwater discharged into the estuaries during the wet season, followed by little or no discharge during the dry season. Several restoration projects are planned or are underway within ENP and TTI to restore freshwater flow to historic levels, and these alterations may have effects on manatees using freshwater, estuarine, and near-offshore areas downstream from these projects.
A major goal of this study is to obtain baseline data on manatee distribution, relative abundance, habitat use, and movement patterns within the study area (fig. 1) prior to restoration. By collecting data before and after the restoration, we can evaluate how manatees respond to altered water management regimes, perhaps mediated by changes in availability of freshwater for drinking and seagrasses for foraging. These data also are being used to parameterize an individual-based population model that simulates the movement patterns of manatees under different hydrologic conditions.
|Figure 1. Study area showing strip transects (black lines) and manatee satellite fixes (17,753 yellow dots) from Argos PTT tags (26 animals) from June 2000 to December 2003.|
Two primary field methods are being used to monitor manatees in the study: aerial surveys and satellite telemetry. Monthly manatee distribution surveys are flown year round following the same inland and offshore flight path (fig. 2). Strip-transect aerial surveys involve summer flights along parallel flight paths that are roughly perpendicular to the coast line (fig. 2). The strip transect approach has been successfully used to estimate manatee densities in the Banana River, Florida (Miller and others, 1998). Satellite telemetry has been used extensively along the east coast of Florida to document seasonal movement patterns, migratory behavior, and site fidelity (Deutsch and others, 2003). In combination, aerial surveys and satellite telemetry provide complementary data on coarse-scale population trends versus detailed movement patterns.
|Figure 2. Strip transects (green lines) and distributional flight survey (yellow lines).|
Thirty distribution surveys were flown from August 1999 to February 2002. Six strip transect surveys were flown in summer 2000, eight in 2001, and eight in 2002. The parallel transects are 3.4 to 8.4 km in length, 1 km apart, with a survey strip width of approximately 250 m. Two observers in the cockpit independently record each sighting according to location, manatee activity, and group size. The independent data are used in abundance analysis to directly estimate and correct for manatees that may be missed by the observer.
We used two types of satellite systems to acquire geographic locations from tagged manatees (fig. 3). Most tagged manatees were fitted with Argos transmitters, providing approximately four location fixes per 24-hour period. We also used GPS tags that provided much more accurate locations than the Argos data (approx. 30 m versus 150 m) every 15-30 minutes, but the battery life was much shorter (8 weeks versus 6 months). In combination, the Argos data provided region-wide, long-term coverage suitable for revealing general patterns of habitat use, while the GPS data showed fine details of travel pathways and time spent in specific areas. Most manatees were captured and radio-tagged during the winter months at Port of the Islands, Faka Union canal, Collier County.
|Figure. 3. Captured manatee being released with radio transmitter.|
The aerial survey data show that the Ten Thousand Islands region is an important area for manatees. In the wet season manatees were dispersed across the area in small groups. The majority of sightings were of manatees in offshore bays feeding on seagrass. Fewer, but consistent numbers were sighted inland in canals, rivers, and creeks with a higher percentage inland in dry season than in wet. These patterns were comparable over the years of data.
The patterns identified from the aerial survey data were substantiated by the telemetry data, with even greater detail and insight into the activity patterns of the manatees. Satellite-based Argos transmitters were used to remotely track movements of 26 manatees between June 2000 and December 2003, yielding 17,753 high quality fixes for 6,793 tag-days (fig. 1). A large number of fixes occurred in inland sites, often many kilometers upstream in canals, rivers, and creeks. During the dry season (March – May) manatees spend nearly 25 percent of their time upstream in inland sites, whereas during the wet season (July – September) they spend much more time offshore foraging on seagrass beds.
GPS tags, placed opportunistically on 15 manatees through August 2004, show a pattern similar to the Argos data. The GPS data show detailed pathways as manatees move between offshore and inland areas (fig. 4). GIS analyses of these movement patterns show that manatees make frequent, regular movements between offshore and inland zones (fig. 5, bottom graph). Tagged manatees typically spent less than a day at inland sites, but often remained on offshore seagrass beds for several days. All tagged manatees showed a similar pattern of alternating between the two zones at regular intervals ranging from 2-8 days throughout the year. While transitioning from one zone to another, their rate of travel increased substantially, often spiking upwards to 2 or 3 kilometers per hour (fig. 5, top graph). Upon arriving at an inland or offshore zone, travel rates decreased greatly. These directed movements were not only frequent, and rapid, but often involved traveling many tens of kilometers, requiring a significant expenditure of energy. Such costly movements suggest the importance to manatees of both offshore seagrass and inland sites.
|Figure 4. GPS track for a single animal (Anna) April 24 to August 1, 2003 showing typical inshore-offshore movements.|
|Figure 5. GIS Analysis of GPS data for one individual (Surfer) during August 2000, showing speed of movement (top) and regular movement between offshore feeding areas (seagrass) and inland freshwater sites (bottom).|
For 6 individuals that were tracked for at least one full wet and dry season, we compared their use of freshwater access points. During the dry season, most manatees (13 of 15 animal-seasons) visited the Faka Union Canal freshwater site, which is the most reliable source of freshwater in the study area. During the wet season, most manatees (8 of 12 animal-seasons) shifted their home range and never visited the Faka Union site. Water monitoring stations in the study area show that during the wet season freshwater is readily available at many localities; during the dry season these same stations show saline or hypersaline conditions.
Evidence for the importance of freshwater to manatees has been provided recently by physiological studies (Ortiz and others, 1999). This study provides some of the first evidence from manatee movement patterns showing the importance of freshwater sites to manatees. Because restoration activities are expected to change the timing and quantity of freshwater inflow to rivers and canals in the study area, we expect manatee movement patterns to change in response to the changing availability of freshwater. The abundance and distribution of manatees likely will track the increased availability of freshwater associated with restoration.
To further address this issue, we are developing an individual-based population model that simulates manatee behavioral responses to changes in hydrologic restoration. We are also exploring the application of a new statistical approach to better estimate abundance and changes in distribution by directly estimating and accounting for manatees unseen below the surface during an aerial survey. As restoration begins, first on the smaller scale Southern Golden Gate Estates project centered around the Faka Union Canal, then on the larger Comprehensive Everglades Restoration Project (CERP), we expect to continue using aerial surveys and telemetry to monitor the response of manatees to restoration.
This study supports the following tasks for the U.S. Department of the Interior (Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida, May 2004): Southern Golden Gate Estates Hydrologic Restoration project, by modeling predicted changes in hydrology and ecology in the Ten Thousand Islands NWR, and providing baseline data and monitoring of effects on a federally listed species, the West Indian manatee, within the Ten Thousand Islands NWR. The study also supports the Landscape-Scale Modeling effort by providing an individual-based demographic model of a threatened species, the West Indian manatee, and by providing landscape-scale monitoring and assessment for the CERP Monitoring and Assessment Plan.
Deutsch, C.J., Reid, J.P., Bonde, R.K., Easton, D.E., Kochman, H.I., and O’Shea, T.J., 2003, Seasonal movements, migratory behavior, and site fidelity of West Indian manatees along the Atlantic Coast of the United States: The Wildlife Society, Wildlife Monographs No. 151, 77 p.
Miller, K.E., Ackerman, B.B., Lefebvre, L.W., and Clifton, K.B., 1998, An evaluation of strip-transect aerial survey methods for monitoring manatee populations in Florida: Wildlife Society Bulletin 26(3):561-570.
Ortiz, R.M., Worthy, G.A.J., and Byers, F.M., 1999, Estimation of water turnover rates of captive West Indian Manatees (Trichechus manatus) held in fresh and salt water: Journal of Experimental Biology 202:33-38.
Additional information is available on the South Florida Information Access (SOFIA) website: http://sofia.usgs.gov/projects/manatees
For more information
Jim Reid or Brad Stith
U.S. Geological Survey
412 NE 16th Ave., Room 250
Gainesville, FL 32601
Phone: (352) 372-2571
Fax: (352) 374-8080
U.S. Fish and Wildlife Service
Ten Thousand Islands National Wildlife Refuge
3860 Tollgate Blvd., Room 360
Naples, FL 34114
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Using Data to Identify Hot Spots and Predict Bleaching Events
Part C: Degree Heating Weeks
Heat stress on corals will accumulate if the SST stays above the bleaching threshold for an extended period of time. So, in addition to measuring how far above the bleaching threshold the SST is, scientists also measure how long the SST stays above the threshold. These measurements are know as degree heating weeks (DHWs). DHWs tell us how much thermal stress has built up in a given area over the last 12 weeks.
- Go to NOAA's Coral Reef Watch home page. Click on the Degree Heating Weeks icon in the left-hand navigation bar to access the most up-to-date DHW data. The Coral Reef Watch DHW maps highlight those areas around the world where corals have been under thermal stress for extended periods of time.
- Find the cell in the table with the most current data. Click on the Global link for that date to open up a global map of current DHW data.
- Examine the map to familiarize yourself with how the data are reported.
- black areas have not accumulated thermal stress over the previous 12 weeks (the temperature did not crossed the local bleaching threshold)
- colored regions indicate thermal stress to corals in those areas
- the units for DHW are "degree C-weeks", which combine the intensity and duration of thermal stress into one single number
- when the thermal stress reaches 4 degree C-weeks, you can expect to see significant coral bleaching, especially in more sensitive species
- when thermal stress is 8 degree C-weeks or higher, you would likely see widespread bleaching and mortality from the thermal stress
Answer the following question about the DHW map.
- Using the dotted line grid as a way of dividing the map into smaller regions, how many regions were experiencing thermal stress?
Stop and Think
1: Did you identify any areas where you would expect to see significant or widespread bleaching? Explain.
- Use your browser's back button to return to the main DHW map page. Scroll down to the bottom of the page and click on the DHW Animations link.
- Watch the animation at least once all the way through, noting which months appear to have more or less accumulated thermal stress than is seen in the most current data.
Answer the following question about accumulated thermal stress over the last 6 months.
- How do the current levels of accumulated thermal stress compare to those over the last 6 months?
- Do certain regions appear to experience prolonged thermal stress more often than others? (i.e., Do certain regions appear more at risk than others?) | <urn:uuid:3d660ebc-778b-489d-9f4a-41f47f3270cb> | 3.53125 | 551 | Tutorial | Science & Tech. | 56.85226 |
Are you an astronaut? Did you pack extra Twinkies for your trip to the International Space Station? If so, NASA might be on to you, my friend.
Kidding aside, it’s critical to keep an accurate tab on the weight of those in space. This is due to the simple fact that muscles have a lovely habit of atrophying when not in use. And in space, where resistance is lower (but not quite futile), the muscles attached to the bones and ligaments of our glorious astronauts tend to shrivel.
Of course this is combated with exercise and the like, but that isn’t a perfect fit. That in mind, the ground crew keeps numbers on what their suspended charges weigh. The problem is that scales, as we know them here, don’t work in null-gravity. Tools have been built to measure weight, but they are imperfect.
Enter The Kinect
As it shakes down, the Kinect might be a useful replacement for the current system. The work of Carmelo Velardo, the man with a Kinect plan, is described thusly by New Scientist:
Along with colleagues at the Italian Institute of Technology’s Center for Human Space Robotics in Torino, he used the Kinect’s depth-sensing ability to create a 3D model of an astronaut. Then the team ran their calculation using a statistical model that links weight to body measurements based on a database of 28,000 people. Velardo’s estimates are 97 per cent accurate, corresponding to an average error of just 2.7 kilograms, which is comparable to the current method used on board the ISS.
If that doesn’t make your inner-nerd melt with excitement, you need to dig up your soldering iron; it has been too long.
However, actually getting things into space is fantastically expensive, and so the chance of the Kinect making it to space in the short term is slim, but this sort of thing is exactly what people don’t understand when they complain that something is either ‘pure science,’ or ‘just a toy;’ oftentimes the line between the two is vague, if it exists at all.
For more NASA, be sure and check out its new weather satellite system. | <urn:uuid:2ca2591d-24a3-4a3e-9f80-f3366c4c462a> | 3.015625 | 470 | Personal Blog | Science & Tech. | 55.641381 |
June 14, 2013
Why, if Mars is so fascinating, does NASA now have a fixation on the Moon?December 12, 2006, Tuesday
Astronomers have discovered that billions of years before a mysterious antigravity overcame cosmic gravity and sent the galaxies scooting apart, it was already present in space, affecting the evolution of the cosmos.November 17, 2006, Friday
To the Editor: Re ''Hubble, NASA's Comeback Kid, Survives to See a New Dawn http://www.nytimes.com/2006/11/07/science/space/07hubb.html Read the Article. '' (Nov. 7): Dennis Overbye strikes an optimistic note concerning NASA's decision to extend the life of the Hubble Space Telescope. Another view of this is that fixing the Hubble, for all the good work it has done in the past, represents sticking with the status quo and resistance to technological change.November 14, 2006, Tuesday
If all goes well, the Hubble Space Telescope will continue to send back cosmic postcards long after the space shuttles that launched and nurtured it have been retired.November 07, 2006, Tuesday
In order to repair the Hubble Space Telescope, it is necessary to overcome intense barriers — both physical and political.November 05, 2006, Sunday
The mission to repair and upgrade the Hubble Space Telescope, canceled after the loss of the shuttle Columbia, is back on the schedule for a May 2008 launch.November 01, 2006, Wednesday
A Hubble mission may be marginally more risky than a flight to the space station, but that risk is surely worth taking for the scientific payoff.November 01, 2006, Wednesday
Vaccinating wolves, organic versus regular wheat, the Hubble Space Telescope, and more.October 17, 2006, Tuesday
Among a batch of new planets, found by the Hubble telescope on a small patch of sky in Sagittarius, are as many as five that orbit their home stars in less than a day.October 05, 2006, Thursday
Subtle effects of global warming, silk stockings for spiders, springtime on Uranus and more.October 03, 2006, Tuesday
SEARCH 419 ARTICLES ABOUT HUBBLE SPACE TELESCOPE:
Astronomers unveiled new pictures and observations from the Hubble Space Telescope, the first images released since an astronaut crew refurbished the telescope in May.
On May 11, the space shuttle Atlantis and seven astronauts set off on an 11-day voyage to repair and refurbish the Hubble Space Telescope one last time.
The shuttle completed an 11-day mission to repair the Hubble Space Telescope.
A look at the new instruments and repairs planned for the Hubble Space Telescope.
A selection of images taken by the Hubble Space Telescope, which made its 100,000th orbit of the Earth on Aug. 11.
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A wire coil of 25 turns has a cross-sectional area of 14 cm2. The
coil is placed in a uniform field of a large magnet with B = 0.32
T. The coil is suddenly rotated 90 o from an orientation parallel
to the field to one perpendicular to the field. The time to flip
the coil is 0.61 s.
What is the magnitude of the average emf produced?
What will be the average current produced if the circuit of the
coil is closed and the resistance is 60 ohm? | <urn:uuid:9242e8e9-0652-4f12-9bd3-a162bb0d83af> | 3.09375 | 113 | Q&A Forum | Science & Tech. | 81.869595 |
Bunce, J.A. 2012. Responses of cotton and wheat photosynthesis and growth to cyclic variation in carbon dioxide concentration. Photosynthetica 50: 395-400.
The author - a research scientist at the Crop Systems and Global Change Laboratory of the U.S. Department of Agriculture - notes that large rapid fluctuations in CO2 concentration often occur in free-air CO2-enrichment or FACE studies, citing Hendrey et al. (1999), Okada et al. (2001) and Bunce (2011), further noting that "the importance of these rapid fluctuations in CO2 concentration to plant function remains uncertain." However, he also notes that "Holtum and Winter (2003) measured PN [net photosynthesis] and found significantly lower mean rates when the CO2 concentration varied with a period of 40 seconds compared to rates measured at a constant mean CO2 concentration." And, therefore, he proceeded to further explore the subject in greater detail, testing to see "whether the long-term growth and PN of cotton and wheat plants were affected by 1-minute cycles of CO2 concentration."
What was done
As Bunce describes it, he "used open-top chambers to expose cotton and wheat plants to either a constant elevated CO2 concentration of 180 ppm above that of outside ambient air, or to the same mean CO2 concentration, but with the CO2 enrichment cycling between about 30 and 330 ppm above the concentration of outside ambient air, with a period of one minute." These procedures were followed for three short-term (27-day) periods of cotton over two summers, plus one winter wheat crop that was grown from sowing to maturity.
What was learned
The USDA researcher reports that "total shoot biomass of the vegetative cotton plants in the fluctuating CO2 concentration [FACE] treatment averaged 30% less than in the constantly elevated CO2 concentration treatment at 27 days after planting," while "wheat grain yields were 12% less in the fluctuating CO2 concentration treatment compared with the constant elevated CO2 concentration treatment."
What it means
The meaning of Bunce's findings is pure and simple. As he straightforwardly puts it: "the results suggest that treatments with fluctuating elevated CO2 concentrations [such as are characteristic of all FACE experiments] could underestimate plant growth at projected future atmospheric CO2 concentrations." Thus, earth's plant life could well be far better off in a high-CO2 world of the future than even we have long contended it will be.
Bunce, J.A. 2011. Performance characteristics of an area distributed free air carbon dioxide enrichment (FACE) system. Agricultural and Forest Meteorology 151: 1152-1157.
Hendrey, G.R., Ellsworth, D.S., Lewin, K.F. and nagy, J. 1999. A free-air enrichment system for exposing tall forest vegetation to elevated atmospheric CO2. Global Change Biology 5: 293-309.
Holtum, J.A.M. and Winter, K. 2003. Photosynthetic CO2 uptake in seedlings of two tropical tree species exposed to oscillating elevated concentrations of CO2. Planta 218: 152-158.
Okada, M., Lieffering, H., Nakamura, H., Yoshimoto, M., Kim, H.Y. and Kobayashi, K. 2001. Free-air CO2 enrichment (FACE) using pure CO2 injection: system description. New Phytologist 150: 251-260.Reviewed 9 January 2013 | <urn:uuid:cbaa7c60-54f4-4a2c-a3f7-806f584d01ed> | 2.859375 | 730 | Knowledge Article | Science & Tech. | 56.58516 |
Chemistry Sponsored by
Proteins consist of amino acids that conform to the following structure: R-CH(NH2)COOH
Amino acids contain an amino group, -NH2, and a carboxyl group, -COOH. Amino acids link to each when the carboxyl group of one molecule reacts with the amino group of another molecule, creating a peptide bond and releasing a molecule of water. Amino acids are the basic building blocks of enzymes, hormones, proteins and body tissues. | <urn:uuid:21cd095c-16ef-48b4-84ff-dcb093a0f956> | 3.484375 | 110 | Knowledge Article | Science & Tech. | 33.176712 |
Contact: Evan Lerner
University of Pennsylvania
Caption: This is an illustration of a silicon atomic force microscope tip sliding over the surface of a diamond punch. While in contact, silicon atoms from the tip bond with the carbon atoms of the diamond and are left behind as the tip slides on. Penn researchers conducted the wear experiment in a transmission electron microscope to observe this "atomic attrition" in action. A TEM image of the tip is inset.
Credit: Felice Macera
Usage Restrictions: With credit
Related news release: Penn research show mechanism behind wear at the atomic scale | <urn:uuid:ab66e022-f37d-45eb-be73-df1adacd4913> | 3 | 120 | Truncated | Science & Tech. | 25.231559 |
A nanoscale grapevine with hydrogen grapes could someday provide your car's preferred vintage of fuel. Rice Univ. researchers have determined that a lattice of calcium-decorated carbyne has the potential to store hydrogen at levels that easily exceed Department of Energy (DOE) goals for use as a "green" alternative fuel for vehicles.
It doesn’t look like a leaf, but the photosynthesis imitator being developed by teams at MIT would do much the same thing. Right now, it consists of a glass container full of water, with a catalyst-equipped solar cell inside on a divider between two sections. When exposed to the sun, the electrified catalysts produce two streams of bubbles — hydrogen on one side, oxygen on the other. When recombined these two elements create electricity; MIT is still working on the hydrogen side.
Aldrich Materials Science, a strategic technology initiative of Sigma-Aldrich Corp., today announced it has signed an agreement to collaborate on the scale-up and commercialization of next-generation boron hydride hydrogen-storage materials with Ilika, a UK-based advanced cleantech materials discovery company.
Many kinds of algae and cyanobacteria are capable of using energy from sunlight to split water molecules and release hydrogen, which holds promise as a clean and carbon-free fuel for the future. One reason this approach hasn’t yet been harnessed for fuel production is that under ordinary circumstances, hydrogen production takes a back seat to the production of compounds that the organisms use to support their own growth. However, a team of researchers have found a way to use bioengineered proteins to flip this preference, allowing more hydrogen to be produced.
An international team of scientists, led by a team at Monash Univ., has found the key to the hydrogen economy could come from a very simple mineral, commonly seen as a black stain on rocks.
A report commissioned by the U.S. Department of Energy has concluded that a Univ. of Colorado Boulder method of producing hydrogen fuel from sunlight is the only approach among eight competing technologies that is projected to meet future cost targets set by the federal agency.
A new hydrogen research initiative based in Japan will leverage Department of Energy (DOE)-funded hydrogen research at Sandia National Laboratories' California site and will likely become the first research effort to be rolled into a broader laboratory research umbrella aimed at increasing the laboratories’ hydrogen partnerships domestically and abroad.
Researchers in Denmark and at Stanford’s National Accelerator Lab have created a device to harvest the energy from part of the solar spectrum and have it to power the conversion of single hydrogen ions into hydrogen gas. They were able to do so without the use of expensive platinum catalysts, instead finding a way to use molybdenum sulfide in conjunction with a chemical solar cell.
Purdue Univ. researchers have collaborated with scientists at General Atomics to create safe and efficient pellets to power hydrogen fuel cells that can run an array of portable electronic devices.
Researchers have revealed a new single-stage method for recharging the hydrogen storage compound ammonia borane. The breakthrough makes hydrogen a more attractive fuel for vehicles and other transportation modes.
The production of inexpensive hydrogen for automotive or jet fuel may be possible by mimicking photosynthesis, according to a Penn State materials chemist, but a number of problems need to be solved first.
How does a Michigan State Univ. scientist fuel his enthusiasm for chemistry after 60 years? By discovering a new energy source, of course. SiGNa Chemistry Inc. unveiled its new hydrogen cartridges, which provide energy to fuel cells designed to recharge cell phones, laptops, and GPS units. The green power source is geared toward outdoor enthusiasts as well as residents of the Third World, where electricity in homes is considered a luxury.
Coating a lattice of tiny wires called Nanonets with iron oxide creates an economical and efficient platform for the process of water splitting, an emerging clean fuel science that harvests hydrogen from water, Boston College researchers report.
For nearly a century, nobody knew how the little molecule that’s in the middle of many of today’s hydrogen storage and release concepts was organized. Through a combination of nuclear magnetic resonance and neutron diffraction techniques, researchers at two DOE laboratories have deciphered the deceptively simple crystal structure.
Researchers at the Department of Energy's Oak Ridge National Laboratory have developed a biohybrid photoconversion system—based on the interaction of photosynthetic plant proteins with synthetic polymers—that can convert visible light into hydrogen fuel.
A little disorder goes a long way, especially when it comes to harnessing the sun’s energy. Scientists from the Lawrence Berkeley National Laboratory jumbled the atomic structure of the surface layer of titanium dioxide nanocrystals, creating a catalyst that is both long lasting and more efficient than most materials in using the sun’s energy to extract hydrogen from water.
Engine experts and biofuels researchers at Sandia National Laboratories are working on a project that aims to modify an endophytic fungus so that it will produce fuel-type hydrocarbons for transportation purposes.
Researchers from the Cardiff Univ. School of Chemistry are opening up a new way of using hydrocarbon feedstocks to make a range of valuable products. | <urn:uuid:1c22dfcd-ed08-4e20-8cb9-dfd81fa1556d> | 3.375 | 1,080 | Content Listing | Science & Tech. | 24.481757 |
Partial ice-out on Lower Saint Regis Lake , March 22, 2012.
Record-high March temperatures have driven the ice from Lower Saint Regis Lake earlier than usual. Only about half of it remains today (March 25), all rotten and waiting for a final push by the wind to disintegrate completely. Several climatic factors have conspired in this, including La Niña, the Arctic Oscillation, and snow-free ground that the sun is warming faster than it would if it the land were covered with reflective whiteness. But the heat wave and early ice-out also fit a larger pattern of change in the North Country.
According to records kept by faculty and staff at Paul Smith's College, this ice-out came earlier than at any time in the last 4 decades (see the dot in the far lower right corner of the chart below). But it wasn't completely out of the blue, either. It fits into a decadal-scale trend of earlier ice-outs, as well.
For most of the last century, the largest changes in North Country ice cover have been in the later and later timing of freeze-up dates. Nowadays the main basin of Lake Champlain often fails to ice over at all in winter. A trend toward earlier ice-out dates on local lakes has been weaker, partly because variable snow cover and wind action complicate the picture in spring, but also because our spring temperatures haven't warmed as consistently as autumn temperatures have during the last century or so. (link to report on climate change in the Champlain Basin)
Until recently, that is. For the last 2 decades, spring temperatures in the North Country have risen more consistently, and in 2010 the ice-out trend on Lower Saint Regis Lake became statistically significant. This year's super-early melt-off strengthens the trend even more.
So yes, our mid-March heat wave was unusual and it was not all due to greenhouse warming alone. But I think it would be a mistake to leave global change out of the picture altogether. This spring is not just a meaningless random anomaly. As you can see for yourself on the chart above, it's where we've been headed for quite some time.
Spring 2012 may not be a new normal - yet. But with heat-trapping fossil fuel emissions continuing to accumulate in the atmosphere, it seems like a reasonable bet that future springs will begin to resemble this one more and more as the world continues to warm. | <urn:uuid:959fea4a-b8f8-4af5-8d82-401997865877> | 3.28125 | 503 | Personal Blog | Science & Tech. | 52.431151 |
Gouldian finches naturally wear different colored caps and usually choose mates with their same cap color. Covering a male’s right eye changes his courtship behavior.
Credit: Sarah R. Pryke/Macquarie Univ.
Even if science can’t make life longer, perhaps a pill can make a long life better
The gene patenting decision from a plaintiff’s point of view
With everyday materials, two research teams conceal ordinary objects
In mating display, male birds match moves to songs
Coverage of the 2013 American Association for the Advancement of Science meeting
The Year in Science 2012
Three-part series on the scientific struggle to explain the conscious self
Tables of contents, columns and FAQs on SN Prime for iPad | <urn:uuid:3466330b-0707-4594-9533-519c2bf58d0c> | 3.140625 | 157 | Content Listing | Science & Tech. | 37.087415 |
Specifies the font set.
Specifies the number of bytes in the string argument.
Specifies the number of characters in the string argument.
Returns the overall ink v.
Returns the overall logical v.
Specifies the character string.
If the overall_ink_return argument is non-NULL, it is set to the bounding box of the string's character ink. The overall_ink_return for a nondescending, horizontally drawn Latin character is conventionally entirely above the baseline; that is, overall_ink_return.height <= -overall_ink_return.y. The overall_ink_return for a nonkerned character is entirely at, and to the right of, the origin; that is, overall_ink_return.x >= 0. A character consisting of a single pixel at the origin would set overall_ink_return fields y = 0, x = 0, width = 1, and height = 1.
If the overall_logical_return argument is non-NULL, it is set to the bounding box that provides minimum spacing to other graphical features for the string. Other graphical features, for example, a border surrounding the text, should not intersect this rectangle.
When the XFontSet has missing charsets, metrics for each unavailable character are taken from the default string returned by XCreateFontSet so that the metrics represent the text as it will actually be drawn. The behavior for an invalid codepoint is undefined.
The function Xutf8TextExtents is an XFree86 extension introduced in XFree86 4.0.2. Its presence is indicated by the macro X_HAVE_UTF8_STRING.
Table of Contents | <urn:uuid:e893ceca-cd6a-484e-aecd-60bb8e334314> | 2.703125 | 354 | Documentation | Software Dev. | 44.305472 |
Continuous research and development of alternative energy could soon lead to a new era in human history in which two renewable sources - solar and wind - will become Earth's dominant contributor of energy, a Nobel laureate said here today at a special symposium at the American Chemical Society's 240th National Meeting...
- Global investment in renewable energy powers to record $257 billionMon, 11 Jun 2012, 20:32:18 EDT
- Americans using less energy, more renewablesTue, 24 Aug 2010, 8:43:01 EDT
- Electricity collected from the air could become the newest alternative energy sourceWed, 22 Sep 2010, 12:43:24 EDT
- Discovery opens door to efficiently storing and reusing renewable energySun, 31 Mar 2013, 9:31:37 EDT
- Shifting the world to 100 percent clean, renewable energy as early as 2030 -- here are the numbersMon, 19 Oct 2009, 12:29:19 EDT | <urn:uuid:b7d7b968-8b89-4c60-ac3c-c80fb285e290> | 2.921875 | 190 | Content Listing | Science & Tech. | 24.146596 |
(Editor’s note: there’s been a lot to talk around here regarding the recent earthquake in Chile. Here’s another take on the science of large-scale natural events.)
by Katie Bowell, Curator of Cultural Interpretation
Although none of us will have noticed a difference, scientists at NASA have calculated that the 8.8 magnitude earthquake that struck Chile on February 27 was so powerful that it may have shortened the length of a day and shifted the Earth’s axis.
The earthquake, the seventh largest in recorded history, shifted enough rock on our planet – around 400 kilometers of the Earth’s crust – to redistribute Earth’s mass and speed up its rotation. A faster rotation equals a shorter day. The resulting change is slight, as our days have hypothetically shortened by only 1.26 microseconds (1 microsecond = one millionth of a second), but the change is permanent.
NASA also calculates that the earthquake moved the Earth’s figure axis by around eight centimetres (3 inches). The Earth’s figure axis is not the same as the north-south axis, but rather is the axis around which the Earth’s mass is balanced (the two axes are about 10 meters, or 33 feet, apart from each other).
If the earthquake in Chile, an 8.8 on the Richter scale, was strong enough to shorten days and shift the Earth’s axis, why didn’t the 7.1 magnitude earthquake in Haiti in January do something similar? Well, it helps to know a little about how the Richter scale works. The Richter scale measures earthquakes on a base-10 logarithmic scale, which means that each whole number you go up on the scale, the amplitude of the ground motion recorded on a seismograph goes up by a factor of 10. So, while Chile’s 8.8 magnitude earthquake was only 1.7 steps above Haiti’s 7.1 magnitude earthquake on the Richter scale, it was almost 20 times stronger. | <urn:uuid:fccd0aad-4a38-4091-94ed-523ef4b1cd64> | 4.375 | 426 | Personal Blog | Science & Tech. | 59.742416 |
Click on the picture to get details about Gambas architecture...
A drawing is better than a long speech. And I'm fond of this kind
of diagram that make people think that program design is completly
clean and careful thought ;-).
The Development Environment
hides this machinery behind a pretty graphical interface.
A project is a set of files stored in one
A project can contain source files (forms, classes, modules)
or any data files of any types:
- The project configuration is stored in a file named ".project".
- The source files are stored in a sub-directory named ".src".
- Data files are stored in the project directory or in visible sub-directories.
is a program named gba3
It transforms your project, the compiled files included, in one sole
is a program named gbc3
It transforms your project's forms, classes and modules files into binary
compiled files that can be understood and executed by the interpreter.
A Gambas executable file is an uncompressed archive of your project, the compiled files included.
The archive file is marked as a script with the #!/usr/bin/gbx3
magic header, so that Linux executes it by calling the interpreter transparently.
A compiled file is a binary representation of
a class, that contains every information useful to the interpreter :
functions transformed to byte code, constants, variables definitions,
debugging information, etc.
Using mmap System Call
If your project was compiled as an executable, i.e. as an archive,
the interpreter maps the file into memory instead of loading it. It is worth doing !
is a program named gbx3
It executes the byte code of the compiled file generated
by the compiler.
The Class Loader
loads compiled forms, classes and modules into the interpreter.
The Execution Unit
is the heart of the interpreter.
It dispatches and executes each byte-code instruction
generated by the compiler.
is a command-line tool embedded in the interpreter.
It allows the development environment to debug a Gambas program by running it step by step,
watching the stack contents, evaluating any expression in the current running context...
are the interpreter
functions associated to the corresponding Gambas
functions like Sin
, etc. or
operators like +
The Component Interface
is a set of
routines and services used by the components to communicate with the
The interpreter's internals are hidden that way.
The Component Loader
is the part of the
interpreter that loads components shared libraries, gives them access to the
, and that publishes their interface to the other
The Native Classes
are classes that can be used without loading
They are integrated in the interpreter, and can be looked
upon as a part of the Gambas language.
Components are shared libraries that are loaded at run time by the interpreter.
They can contain new classes and hook routines such as event loop management, shell arguments
analyze, etc. They can publish a set of routines as an interface to other components also.
Components can be written in Gambas too. The archiver generates them as Gambas executables
from Gambas projects marked as "component projects". | <urn:uuid:f49d1735-a238-4705-86e1-ce24b29a21b2> | 3.34375 | 683 | Documentation | Software Dev. | 39.693079 |
Assembly: Microsoft.Xna.Framework (in microsoft.xna.framework.dll)
A texel represents the smallest unit of a texture that can be read from or written to by the GPU. A texel is composed of 1 to 4 components. Specifically, a texel may be any one of the available texture formats represented in the SurfaceFormat enumeration.
A cube texture is a collection of six textures, one for each face of the cube. All faces must be present in the cube texture. Also, a cube map surface must be the same pixel size in all three dimensions (x, y, and z). Figure 1 shows a fully populated texture cube.
Figure 1. TextureCube Resource Architecture | <urn:uuid:44d69438-c7d5-451c-90e3-3ae2f7d331e2> | 2.859375 | 147 | Documentation | Software Dev. | 49.285027 |
Science has shown us that a number of organisms use the stars for navigation: songbirds, harbor seals and, of course, humans. But a new study by a team of Swedish and South African researchers published today in the journal Cell Biology indicates that a rather unexpected creature can be added to this list—the lowly dung beetle.
The beetles are known for creating small balls made of animal feces (i.e. dung) and rolling them in straight lines over long distances. They do this because the dung is their main food source—and other beetles often try to steal the dung once it’s been rolled into a ball. The surest way of retaining the valuable dung once it’s been packed into a ball is to move it away from the original dung pile as quickly as possible.
Researchers, though, have long been mystified by the tiny beetles’ ability to roll the dung balls in straight lines at night. “Even on clear, moonless nights, many dung beetles still manage to orientate along straight paths,” said lead author Marie Dacke of Lund University in Sweden. “This led us to suspect that the beetles exploit the starry sky for orientation—a feat that had, to our knowledge, never before been demonstrated in an insect.” - Continue reading atSmithsonian.com. | <urn:uuid:527a1e55-5a18-4a41-8ebd-b326f118885e> | 4 | 280 | Truncated | Science & Tech. | 55.927421 |
The CO2/Temperature correlation over the 20th Century
Posted on 18 June 2009 by John Cook
Previously, we looked at the correlation between CO2 and temperature over the past 40 years. However, as I'm always saying, you need to look at the broader view, not just a single piece of the puzzle. The 40 year period was chosen to demonstrate that even during a period of long term warming, internal variability causes periods of short term cooling. What if we look at a longer time series? Over the past century, are there any periods of long term cooling and if so, what is the significance?
Figure 1 compares CO2 to global temperatures over the past century. The first thing to clarify is that the relationship between CO2 and global temperature is not linear. As more CO2 is added, the warming effect has a diminishing return. Hence, the relationship between CO2 and temperature is logarithmic, not linear. A more appropriate comparison with CO2 is radiative forcing.
Radiative forcing is loosely described as the change in net energy flux at the top of the Earth's atmosphere. Eg - the change in how much energy the planet is accumulating or losing. The relationship between global temperature anomaly and radiative forcing is linear. Figure 2 compares greenhouse gas forcing (which is predominantly due to CO2 but includes smaller contributions from CH4, N2O and CFC) to global temperature anomaly.
In truth, Figure 1 and Figure 2 both paint a similar picture. While CO2 is rising from 1940 to 1970, global temperatures show a cooling trend. This is a 30 year period, longer than can be explained by internal variability from ENSO and solar cycles. If CO2 causes warming, why isn't global temperature rising over this period?
The broader picture in this scenario is to recognise that CO2 is not the only factor that influences climate. There are a number of forcings which affect the net energy flux into our climate. Stratospheric aerosols (eg - from volcanic eruptions) reflect sunlight back into space, causing net cooling. When solar activity increases, the net energy flux increases. Figure 3 shows a composite of the various radiative forcings that affect climate.
Figure 2: Separate global climate forcings relative to their 1880 values (image courtesy NASA GISS).
When all the forcings are combined, the net forcing shows good correlation to global temperature. There is still internal variability superimposed on the temperature record due to short term cycles like ENSO. The main discrepancy is a decade centered around 1940. This is thought to be due to a warming bias introduced by US ships measuring engine intake temperature.
So we see that climate isn't controlled by a single factor - there are a number of influences that can change the planet's radiative balance. However, for the last 35 years, the dominant forcing has been CO2. | <urn:uuid:5760d445-753d-4e13-bb9c-075774e05e0e> | 2.921875 | 585 | Personal Blog | Science & Tech. | 42.580588 |
What drives the motion of a Spinning Top?
There are many forms and shapes of spinning tops, and they are put into motion
in an interesting variety of ways. Some are spun by snap-twisting a center
stem with your fingers and releasing, while the top remains on the ground.
Others are held by a support at the top while a cord wound around the top is
pulled to spin it. The spinning top many of us know is launched from about
waist level to the floor by snapping your wrist as you release it, while
maintaining a grip on the cord wound around its body. However they are spun,
each type behaves in a similar fashion.
The physics of rotation.
The body of a top has at least one axis about which it will spin steadily
and smoothly. This rotation axis is a symmetry axis of the top, known as a
principal axis. For example, the red hoop in the figure below has
two unique symmetry axes indicated, for rotations of the type specified by the
For each unique symmetry axis, the object has a moment of inertia value
that determines how it will spin when a torque is applied. The way this
all works through is described by
Newton's Laws of Rotation
While this can get pretty complicated in detail, there are some circumstances
where the object will spin in a very simple manner. The object's spin about
the rotation axis gives it an angular momentum, which will remain constant
until some outside torque works on it.
The ideal top.
Suppose a top is so perfectly fashioned that its principal rotation axis (spin
axis) goes through its center of mass. (The center of mass, also known as the
center of gravity, is the balance point of the object.) If we spin this top
carefully, so that it remains perfectly upright while spinning (and gravity can't
exert a torque on it about its point), it will spin at a steady angular velocity
almost indefinitely. Sliding friction between its tip and the floor does slow it
gradually. But if the point is very sharp, sliding friction there exerts very
little torque on the top about its rotational axis. Because it's unable to exert a
torque on the ground, the top can't exchange angular momentum with the earth. It
spins on until it slowly gets rid of its angular momentum through sliding
friction and air resistance.
A more realistic top.
In general, the world is not this accomodating. A slight mismatch between the
spin axis and the center of mass will guarantee that gravity exerts a
torque on the top about its tip. The rapidly spinning top will
in a direction determined by the torque exerted by its weight. The precession
angular velocity is inversely proportional to the spin angular velocity, so that
the precession is faster and more pronounced as the top slows down.
Viewed another way, the torque applied by the top's weight does not change much
for small changes in tip angle, so the increment of angular momentum change also
stays the same. But, it increases as a fraction of the total angular momentum
when the top slows down, producing a larger fractional change in the spin
direction for no change in the applied torque -- effectively giving a bigger bang
for the buck.
Either way, we get the commonly observed behavior of a spinning top. When it is
first launched and spinning its fastest, the top is most nearly vertical and
stable in its spin. As it begins to slow down, its precession becomes more
pronounced and its tilt angle off of vertical increases.
With a relatively light top, this precession is most of the behavior we tend to
notice. As an example,
here is a film clip showing the smooth, stable precession of a gyroscope
. (Size: 2.35 MB)
However, it is not the only thing going on. Precession was caused by the
gravitational torque acting on the slightly tipped, or just slightly misshapen,
top - producing an "orbiting" of the top's spin angular momentum
around the vertical direction. In reality, the precession angular velocity
corresponds to another angular momentum - a precession angular momentum (which
is typically much smaller than its spin angular momentum). Now, if this
precession angular momentum is exactly vertical and the top is ideally balanced,
there is no effect of the torque from the top's weight on it. But, that kind of
perfection is hard to come by. Anything that causes the precession angular
momentum to be a bit off vertical will lead to a kind of "precession of the
This secondary effect, called nutation, is usually not significant unless
something happens to disturb the motion of the top. To see what it looks like,
film clip of a gyroscope that has been deliberately nudged
. (Size: 2.56 MB)
Again, the story need not end there. Each new type of precession carries along
with it a new, related angular momentum, and these angular momenta can in turn be
made to precess by an applied torque. It is just that the effect becomes
observably less noticeable and significant with every new stage of this process.
So, we usually end the story with nutation. Thus, The End!
© 2003-2012 - 4physics.com® | <urn:uuid:dbafc271-e28d-4933-847e-892f72c71d61> | 4 | 1,135 | Tutorial | Science & Tech. | 52.290986 |
Video - Microbial Bebop - Bloom
This musical composition was created from data of microbes (bacteria, algae and other microorganisms) sampled in the English Channel. Argonne National Laboratory biologist Peter Larsen created the songs as a unique way to present and comprehend large datasets.
This composition highlights seasonal patterns in marine physical parameters at the L4 Station. The chords are generated from seasonal changes in photosynthetically active radiation. The melody of each measure is comprised of eight notes, each mapped to a physical environmental parameter, in the following order: temperature, soluble reactive phosphate, nitrate, nitrite, saline, silicate and chlorophyll A concentrations.
More information at http://www.anl.gov/articles/songs-key-sea
Photo of cyanobacteria colonies is courtesy Specious Reasons (http://www.flickr.com/photos/28594931@N03/4726914132/) at Flickr via Creative Commons. | <urn:uuid:06a359b5-46f5-465f-ab53-dce61ca33ef7> | 2.8125 | 198 | Truncated | Science & Tech. | 23.046897 |
Large Molecules Problem Set
Problem 12: Sequence of a longer polypeptide
Tutorial to help answer the question
A polypeptide 10 amino acids long is split into various smaller fragments, and the amino acid sequences of some of the fragments are determined. The identified fragments include: ala-gly-ser-gln, lys-trp-arg-pro, gln-his-lys, asp-ala-gly. What is the primary sequence of the polypeptide?
Amino acids of a polypeptide
As with the previous question, a key piece of information is that the length of the unknown polypeptide is 10 amino acids. What are the 10 amino acids that make up the unknown? This is determined by examining the sequences of the three fragments. Note that there are 10 different amino acids present in the three fragments. They are, in alphabetical order:
ala, arg, asp, gly, gln, his, lys, pro, ser, trp
| Since no amino acids are duplicated in this example, any
amino acid found in two fragments identify an overlap. The four
fragments overlapped as follows:
The original peptide must have the sequence of:
The Biology Project
Department of Biochemistry and Molecular Biophysics
The University of Arizona
Revised: October 2004
Contact the Development
All contents copyright © 1996-2003.
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Submitted by lorio on Fri, 2009-09-11 07:00
Using state-of-the-art electron microscopy techniques, a team led by researchers from Caltech has for the first time visualized and described the precise arrangement of chemoreceptors—the receptors that sense and respond to chemical stimuli—in bacteria. In addition, they have found that this specific architecture is the same throughout a wide variety of bacterial species, which means that this is a stable, universal structure that has been conserved over evolutionary time.
Submitted by lorio on Tue, 2009-08-18 07:00
A team of scientists from Caltech have pinpointed two groups of neurons in fruit fly brains that have the ability to sense and manipulate the fly's fat stores in much the same way as do neurons in the mammalian brain. The existence of this sort of control over fat deposition and metabolic rates makes the flies a potentially useful model for the study of human obesity, the researchers note.
Submitted by ksvitil on Tue, 2009-08-11 07:00
Researchers at the California Institute of Technology (Caltech) and their colleagues in 30 laboratories worldwide have released a new set of standards for graphically representing biological information—the biology equivalent of the circuit diagram in electronics. This visual language should make it easier to exchange complex information, so that biological models are depicted more accurately, consistently, and in a more readily understandable way.
Submitted by lorio on Mon, 2009-07-20 07:00
Most evolutionary changes happen in tiny increments. But when it comes to traits like the number of wings on an insect, or limbs on a primate, there is no middle ground. How are these sorts of large evolutionary leaps made? According to a team led by scientists at Caltech, such changes may at least sometimes be the result of random fluctuations, or noise (nongenetic variations), working alongside a phenomenon known as partial penetrance.
Submitted by ksvitil on Thu, 2009-06-11 18:00
The twirling seeds of maple trees spin like miniature helicopters as they fall to the ground. Because the seeds descend slowly as they swirl, they're carried aloft by the wind and dispersed over great distances. Just how the seeds manage to fall so slowly, however, has mystified scientists. In research published in the June 12 Science, researchers from Wageningen University in the Netherlands and Caltech describe the aerodynamic secret of the enchanting swirling seeds.
Submitted by lorio on Fri, 2009-05-29 07:00
Theta oscillations are a type of brain rhythm that orchestrates neuronal activity in the hippocampus, a brain area critical for the formation of new memories. For several decades these oscillations were believed to be "in sync" across the hippocampus, timing the firing of neurons like a sort of central pacemaker. A new study conducted by researchers at Caltech shows that, instead, theta oscillations sweep along the length of the hippocampus as traveling waves.
Submitted by lorio on Tue, 2009-05-19 07:00
You can tell without looking whether you've been stuck by a pin or burnt by a match. But how? In research that overturns conventional wisdom, a team of scientists from Caltech and UCSF, have shown that this sensory discrimination begins in the skin at the very earliest stages of neuronal information processing, with different populations of sensory neurons--called nociceptors--responding to different kinds of painful stimuli.
Submitted by lorio on Wed, 2009-04-22 07:00
Some 25 years after the AIDS epidemic spawned a worldwide search for an effective vaccine against the human immunodeficiency virus (HIV), progress in the field seems to have effectively become stalled. The reason? According to new findings from a team of researchers from Caltech, it's at least partly due to the fact that our body's natural HIV antibodies simply don't have a long enough reach to effectively neutralize the viruses they are meant to target.
Submitted by ksvitil on Wed, 2009-04-08 07:00
The construction of complex man-made objects--a car, for example, or even a pizza--almost invariably entails what are known as "top-down" processes, in which the structure and order of the thing being built is imposed from the outside (say, by an automobile assembly line, or the hands of the pizza maker).
Submitted by lorio on Tue, 2009-04-07 07:00
Scientists at the California Institute of Technology (Caltech) have trained computers to automatically analyze aggression and courtship in fruit flies, opening the way for researchers to perform large-scale, high-throughput screens for genes that control these innate behaviors. | <urn:uuid:e72f5edc-f85e-41fd-8361-041f560e1235> | 3.03125 | 985 | Content Listing | Science & Tech. | 33.077069 |
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Magnetic Fields - Help!
A rectangular current loop is loacted near a long, straight
wirethat carries a current of Iw = 15 A (see
the drawing). The curent in the loop isIL = 20
A. Determinethe magnitude of the net magnetic force that acts on
Anonymous answered4 hours later
You need a Homework Help subscription to view this answer! | <urn:uuid:02d2d34e-b94d-4d8b-9947-53af7d44ae43> | 2.859375 | 100 | Q&A Forum | Science & Tech. | 61.656057 |
Microevolution is evolution on a small scale within a single population. That means narrowing our focus to one branch of the tree of life.
If you could zoom in on one branch of the tree of life
scale the insects, for example you
would see another phylogeny relating all the different insect lineages.
If you continue to zoom in, selecting the branch representing beetles,
you would see another phylogeny relating different beetle species. You
could continue zooming in
until you saw the relationships between beetle populations. Click on
the button below to see this in action!
But how do you know when you've gotten to the population level?
For animals, it's fairly easy to decide what a population is. It is a group of organisms that interbreed with each other that is, they all share a gene pool. So for our species of beetle, that might be a group of individuals that all live on a particular mountaintop and are potential mates for one another.
The potential to interbreed in nature defines the boundaries of a population.
Biologists who study evolution at this level define evolution as a change in gene frequency within a population. | <urn:uuid:0afcd476-24a6-46aa-92a2-11f2b690b599> | 3.765625 | 240 | Knowledge Article | Science & Tech. | 45.020814 |
Published on April 7th, 2011 by: admin in: C2010/X1Analysis of Elenin alignments and strong earthquakes in the years 2010 and 2011. There seems to be a coincidence between lineups and tectonic movement. I’ve collected some data to show an eventual connection between the two phenomena.
Leonid Elenin discovers Comet C/2010 X1Some information about this comet: According to Wikipedia Comet C/2010 X1 (Elenin) is a long-period comet discovered by the Russian astronomer Leonid Elenin on December 10, 2010 at the International Scientific Optical Network’s robotic observatory near Mayhill, New Mexico, U.S.A.
Controversial information on the web concerning EleninOn youtube one can find tons of videos concerning Elenin or C/2010 X1, many refer to this comet with the name “Nibiru” or call it a brown dwarf. Brown dwarfs are sun-like stars with a mass to low to maintain hydrogen fusion. That is why a brown star is not very bright and hard to detect by the telescopes.
A table reflecting data of 10 strongest earth quakes in history
Location Date Magnitude 1. Chile 22/05/1960 9.5 2. Prince William Sound, Alaska 28/03/1964 9.2 3. Andreanof Islands, Aleutian
09/03/1957 9.1 4. Japan 11/03/2011 9.0 5. Kamchatka 04/11/1952 9.0 6. Off western coast of Sumatra,
26/12/2004 9.0 7. Off the coast of Ecuador 31/12/1906 8.8 8. Offshore Maule, Chile 27/02/2010 8.8 9. Rat Islands, Aleutian Islands 04/02/1965 8.7 10. Northern Sumatra, Indonesia 28/03/2005 8.7
Earthquake Northern Sumatra, Indonesia 28-03-05Ok, this earthquake has happened long ago, but I did want to have a look at it anyways. An alignment had occurred on 14-02-05, more than one month before the earthquake, I sincerely couldn’t relate the two events to each other. Nevertheless here is the alignment data:Elenin – Earth – Sun date 14-02-05
Earth dist. 18.267au (distances from Elenin)
Sun dist. 19.255au
Offshore Maule, Chile 27/02/2010On February 27th 2010 an 8.8 earthquake occurred in Chile. Here is the image taken by me from the JPL Small-Body Database Browser for the corresponding date:elenin aligned on chile earthquake 2010
Elenin – Earth – Sun, date: February, 27th 2010
Earth distance 6.042au
Sun distance 7.032auOk, on this image we can see an alignment of Elenin, Earth and our Sun. I’ve googled this issue and some Astronomers say that this could be pure coincidence and doesn’t mean that the two events are related. I do kind of agree with their statement.
But this isn’t all. Let’s keep on investigating…
Japan 11/03/2011We are all still shocked about the horrible earthquake and tsunami that happened in Japan on March, 11th 2011. So many people died and so many more may die due to the nuclear power plant accident that the tsunami caused.
The Japan earthquake was a 9.0 on the richter magnitude scale.
Here is the small object database image I was able to take for this date:
Elenin – Earth – Sun, date: march, 11 2011
Earth distance 2.155au
Sun distance 3.145auI’ve googled hours and hours to get more reliable data on this shocking event (the earthquake) and an eventual relationship with the evident perfect alignment we can observe on the above image. But data on the world wide web is so controversial (especially the videos on youtube) that I don’t want to use it. Only very few sites and pages reflect what I believe to be reliable data.http://ralfengel.com/c2010x1/c2010x1-elenin-lineups-and-earthquakes-analyzed
Some astronomers say that the repetition of an alignment of Elenin, Earth and the Sun and a very strong earthquake at that very time is something more than unusual but not impossible. Just that probabilities for it to happen twice is of a very tiny probability. But it did happen!!Investigate yourself, check out the information and make up your own mind about this.Now, let’s keep on investigating Elenin alignments…
Japan 07-04-2011Today a 7.4 earthquake hit the north east coast of Japan. Here is the small body database image of the Elenin position:
The red line was added by me to make it easier to make out the alignment of Elenin, Earth and Venus.Alignment Data:
Elenin – Earth – Venus date: april, 07th 2011
Earth distance: 1.893au
Sun distance: 2.797auI really do not know if this alignment has got something to do with this new strong quake in Japan. But I believe that it is possible.Now, let’s move into future…
Alignment on 26-09-2011Alignment Data:
Mercury – Sun – Elenin – Earth, date: march, 26th 2011
Earth distance 0.396au
Sun distance 0.607auIf there is a relationship between the Elenin alignments and earthquakes on earth then on this date we’ll probably see some major movement because the distances are much less then on all the other events. I do hope I’m wrong.Now here the last one I checked out…
Alignment on 23-11-11Alignment Data:
Elenin – Earth – Sun, date: October, 23d 2011
Earth distance 0.596au
Sun distance 1.582auOk, Elenin is moving away again but still is very close to our planet.Elenin (C2010/X1) will be closest to earth on 18-11-11 with a distance of 0.233au (35 million kilometers).
The moon is 384,403 kilometers away from us. That is a huge difference. Still, with all the above data reviewed and analyzed over and over again I do start to believe that Elenin may not be a comet after all. It could eventually be something much bigger, well, it would have to be if the relationship between alignments and earthquakes show to be proven true.I still do not know much more and surely do not know if Elenin is this “Nibiru” or “Planet X” you can read about on the internet, but I will not discard this possibility after having seen all the data above.Related posts - pay particular attention to # 3 and # 5...
- Responses to “C2010/X1 Elenin lineups and earthquakes analyzed”
- David Perry Says:
April 28th, 2011 at 2:33 amI can’t say I would find it anything more than coincidence if this is anything less than a brown dwarf. The gravitational pull required to move our tectonic plates at the rate of which your describing when this comet is still so far away seems quite astounding. Perhaps though its also super magnet. I think my concern would be more in the what 14 days after it crosses our path what will we find still lingering in our way..
- John Ruga Says:
June 12th, 2011 at 8:00 amInteresting bit of research you’ve done. I thought you might be able to check a few more Sumatran dates for earthquakes with Elenin alignments so I went to Wikipedia and they have a list of earthquakes going back to the late 1700′s. Here’s the link :http://en.wikipedia.org/wiki/List_of_earthquakes_in_IndonesiaAlso, Elenin can be small but possibly super dense. I recently heard of a star name Sirius C. Apparently it is smaller than Earth and 8 times as dense as our own Sun. Let’s hope Elenin isn’t a fragment from a dwarf star like that.
- circlevilleman Says:
June 22nd, 2011 at 8:36 amCheck the alignment that will happen on Sept. 26-27 2011(a free program called stellarium can be used for this). This Elenin alignment is in conjunction with another alignment of Virgo that will have 3 planets in it plus the Moon and the Sun. Virgo will have Mercury at her shoulders, the Sun at her shoulders, Venus in her womb, Saturn in her womb, and the Moon under her feet. Comet Elenin will align on this date at a position that looks real close to causing a solar eclipse with in Virgo. The Virgo alignment has never occurred in the past and never will happen again after Sept. 27 2011. Mercury is an important planet as it rules Virgo and Jews consider it a symbol of the soul ruler of the Jewish race. Mercury is the wandering shepherd or the wandering Jew. The bright morning star is the planet Venus. Revelation 22:16 “I, Jesus, have sent my angel to give you this testimony for the churches. I am the Root and the Offspring of David, and the bright Morning Star.” Virgo has 12 stars that make her up; there are 12 tribes of the Jews and the churches are referred to in Revelations as the brides of Jesus. Virgo is the constellation of Harvest. The Jewish Holiday of Rash Hosanna is about creation and the Jewish new year will begin on Sept. 26-29 2011.The opening prayer starts with this line, Blessed are you, Lord, our God, sovereign of the universe. This Virgo alignment is also in Revelations 12-1. A great and wondrous sign appeared in heaven: a woman clothed with the sun, with the moon under her feet and a crown of twelve stars on her head. 2 She was pregnant and cried out in pain as she was about to give birth. This Virgo alignment will happen over the United States in the day time so how will we be able to see such a wondrous sign? Only if Elenin moves in front of the Sun and blocks out the light a solar total or partial eclipse. Revelations 8-12: The fourth angel sounded his trumpet, and a third of the sun was struck, a third of the moon, and a third of the stars, so that a third of them turned dark. A third of the day was without light, and also a third of the night. Right after Sept. 27 2011 we will literally follow Elenin’s previous path and be in its tail. Who knows what this tail will contain. Revelations 8-8: The second angel sounded his trumpet, and something like a huge mountain, all ablaze, was thrown into the sea. A third of the sea turned into blood, a third of the living creatures in the sea died, and a third of the ships were destroyed. The third angel sounded his trumpet, and a great star, blazing like a torch, fell from the sky on a third of the rivers and on the springs of water— the name of the star is Wormwood. A third of the waters turned bitter, and many people died from the waters that had become bitter. Some Christians are feeling like this Elenin is wormwood and the rapture will occur before the destruction starts. The Virgo alignment suggested a rapture is fast approaching. No man may know the day but perhaps God is giving us a heads up! Elenin cannot be a comet. This star has many names from many cultures but the one I call it is wormwood. One last note there is actually 2 more comets on approach besides Elenin (that’s a total of 3). Comet P 2006 T1 Levy due to closest on January 11 2012 and Comet Honda due to be closest on August 15 of 2011.
- Circlevilleman Says:
June 22nd, 2011 at 4:48 pmThe proper Virgo alignment date is Sept 29 2011. I have also discovered Israel has a dead line due with in that same time frame to give up land so that Palestine may be declared a state. The United Nations will apply more pressure and demands in late Sept. 2011
- Tom Says:
June 30th, 2011 at 11:53 amElenin is a very dangerous comet because it is a long period comet whose tail will engulf the Earth. Comets are not balls of ice and dust like Nasa states. Comets are electric space capacitors. Comets are electromagnetically connected to the sun and planets by EM ropes. Extreme EM can cause earthquakes. The reason Elenin is causing quakes when others do not is because it has been a long time since Elenin was near the sun to discharge its capacitance.Comets pick up electrons as they fly through space. The longer in space without discharging, the more electricity is stored in the comet. When the comet approaches the sun, it begins to glow because the electric circuit is energized by the sun’s proton wind. The sun provides the positive and the stored electrons provide the negative. The comet nucleus behaves similar to the filament on a light bulb when positive and negative wires are attached. The bulb glows.Comets do the same thing when the comet discharges its capacitance. The infrared signature for comet Elenin suggest the charge Elenin is carrying is so large that when the comet dumps its capacitance, the resulting photon flare up will engulf the Earth as the Earth passes through the tail. When Elenin was 14 AUs away on June 14, 2007, Nasa photographed the comet when they took the infrared image for google sky. The infrared image indicates Elenin’s infrared electrical signature is 17 million miles across with xray jets extending over 100 million miles from Elenin. When Elenin flares when it dumps its energy, the photon blast will be so great that it will instantly turn everything on the earth’s surface to light energy.The reasons other comets are not a threat is that most comets do not pass between the earth and the sun putting the earth in the tail. Also, comets with periods of a a hundred years or so are able to dump their charge more frequently which keeps the IR signature low. Elenin is different. There is no other object is space that has an electric signature like Elenin.Quod erat demonstrandum – It is proven.This is the rapture. See you all on the other side. | <urn:uuid:0f35dd45-d879-4606-817b-5f95acbed7c1> | 2.78125 | 3,102 | Comment Section | Science & Tech. | 67.164527 |
Meteorites that fell to Earth during a meteor shower in July of 2011 have been confirmed to be from Mars.
It doesn’t sound possible, does it? Well the statement that the meteorites came from Mars is a little misleading. The rocks were probably just launched off the surface of the planet when it was impacted by an asteroid an unknown number of years ago. So it wasn’t a recent event by any means.
Still, the meteorites falling to Earth in 2011 make it the fifth time in history that people have observed something coming to Earth originally from Mars. About 24,000 meteorites have fallen to Earth, and only 34 have been confirmed to be from Mars. They’re so valuable that they’re sold at ten times the price of gold. In the past, they’ve landed on Earth in 1815, 1865, 1911, and 1962. | <urn:uuid:ef792a41-1673-423d-bc3a-22f95eda6ab2> | 3.234375 | 183 | Knowledge Article | Science & Tech. | 70.67497 |
|Mar25-05, 06:03 AM||#1|
Vapor Density: 1.3
For a solution It says; VAPOR DENSITY: 1.3
Is VAPOR DENSITY the same as Density of that solution? And what is the unit of 1.3?
Hope for inputs.
|Mar26-05, 02:45 AM||#2|
Vapor density of 1.3 means, in my opinion, that this solution has 1.3 times more of that molecule in the gas phase than the solution in the equilibrium.
|Mar28-05, 10:36 PM||#3|
Vapor density refers to the density of a vapor, in units such as g/m^3 or kg/m^3. Since you don't indicate any units, I think it means something different here. I found this URL:
According to that convention, your solution would produce a vapor with a density 1.3 times that of air. What IS the solution? Do you know?
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In many species of squid, sperm is transferred in complex spermatophores that function like harpoons. Exactly how the spermatophores are delivered is a matter of debate: Some biologists think they're contained inside the penis, but others aren't so sure. Squid are notoriously difficult to study in their deep marine habitats.
At least for hooked squid, some of the mystery is known. Males are literally covered in the spermatophores (above) which lodge in female skin, slowly working their way in (below) before releasing their payload. | <urn:uuid:02be5b2c-fcbb-4372-bbe4-5a01a8c2c620> | 2.96875 | 114 | Knowledge Article | Science & Tech. | 31.981651 |
Next: Results and discussion
The model operates on a square cell of pixels, typically of edge length equal to 500 pixels, where each pixel is assigned to a single phase, such as pore space or cement. The scale of the model is then approximately one micrometer per pixel length. It should be noted at this point, by way of definition, that cement particles are mixed with water to produce cement paste. Initially, a user- specified number of cement particles are randomly placed in the cell such that no two particles overlap, which simulates the mixing process . This is the well-known "random parking" algorithm . Periodic boundary conditions are used to eliminate any artificial edge effects at the cell walls. In practice, this means that any part of a cement particle that would extend beyond the cell boundary is wrapped around to the other side. The particles may be identical or of different sizes, and are modelled in the work described in this paper as being circular in shape. This was done as a matter of convenience--there are no restrictions on cement particle shape in the model. Any shape that can be represented by pixels can be used. We do not believe that there is any significant effect of cement particle shape on the general conclusions of this paper. For the current application, an aggregate particle, modelled as a 100 x 100 pixel square, is first placed in the center of the cell. Since the largest cement particle used was 21 pixels in diameter, the relative size of the aggregate particle requires it to be thought of as a sand grain. During the placement of the cement, the cement particles are not allowed to overlap the aggregate. Fig. 1a illustrates an initial configuration of monosize cement particles (red) placed around a square aggregate particle (white). The black region is water-filled pore space. A preparation variable commonly used in the cement- based materials literature is the water:cement ratio, defined as the ratio of the weight of water to weight of cement in the original water and cement mixture. A value of 0.47 was used in all the simulations described in this paper.
Figure 1a: Showing original cement particle placement around
aggregate for 21 pixel diameter circular cement particles. The
red circles are the cement particles, the white square is the
aggregate particle, and the black is water-filled pore space.
Figure 1a: Showing original cement particle placement around aggregate for 21 pixel diameter circular cement particles. The red circles are the cement particles, the white square is the aggregate particle, and the black is water-filled pore space.
The model is iterated by cycles, where each cycle consists of three steps: dissolution, diffusion, and reaction.
In the dissolution step, any cement pixels in contact with a water-filled pore space pixel are given a probability to dissolve, so that some fraction of these identified pixels dissolve, and some must wait for the next cycle. This is reasonable, since dissolution is a random process at the molecular level. The pixels which dissolve "step off" into the pore space and become random walkers (diffusers). The number that dissolve are counted, and the correct number of extra diffusing pixels are added at random locations within the pore system to account for calcium hydroxide (CH) formation and the volume expansion which occurs when amorphous calcium silicate hydrate (C-S-H) forms. Other ways of adding the extra material, that would correlate more closely to the actual areas where pixels have dissolved, could be thought of, but this is the simplest and easiest method, and should not introduce any problems for the random cement particle-water system. Standard cement chemistry notation (C=CaO, S=SiO2, and H=H2O) is used to denote the hydration reaction products of tricalcium silicate (C3S), the major component of portland cement. In this paper, the cement particles are taken to be pure C3S. More precisely, if n pixels dissolve from off the cement surfaces, 0.7n extra diffusing C-S-H pixels and 0.61n CH diffusing pixels are added to the system . In this way, the correct stoichiometry and hydration product volumes are achieved.
During the diffusion/reaction steps, the dissolved pixels execute random walks throughout the pore space. Periodic boundary conditions are again used, so that a pixel that diffuses out of the box comes back in on the other side. C-S-H pixels continue to move in this random fashion until they encounter a cement surface, at which point they react and stick to this surface. Once C-S-H product is present, diffusing C-S-H pixels can also react and stick to these surfaces as well. Following known cement hydration chemistry, CH product grows in the pore space in a manner different from the C-S-H material. For any given step taken by a diffusing CH pixel, there is a non-zero probability that it can nucleate at its present location. This probability p is a function of the number of CH diffusers put into solution in the given cycle, and is given by
|P = Po [ 1 - exp(-c/cm)]||(1)|
where p is the probability of nucleation, Po is the maximum probability of nucleation, c is the number of CH diffusing pixels remaining in solution at each time step, and cm is an arbitrary scale factor. Experimental results on the number of CH clusters indicate that the form of this function must be such that the nucleation probability goes to zero rapidly with decreasing concentration, but reaches a peak at saturation. The form of eq. (1) satisfies these requirements, although it is not unique in doing so. The parameters Po and cm can be adjusted to control the number of CH clusters that are nucleated. Besides the possibility of nucleation, if a CH species encounters a CH cluster, it will react onto this surface, increasing the size of this cluster. However, there is no Ostwald ripening mechanism in the model, where small CH clusters dissolve and the large clusters' sizes are increased. When the aggregate particle is present, its surface is assumed to be non-reactive, in the sense that neither C-S-H nor CH is allowed to react onto it. Reactive aggregates could, however, be easily handled in the model. When all diffusing pixels have reacted or nucleated, the cycle is complete, and the next cycle begins with a new dissolution step.
After a given number of cycles (typically about 200 are needed to achieve maximum hydration) are executed, the resulting microstructure is analyzed to determine the area fraction of each phase as a function of distance from the aggregate edge. The square shape of the aggregate particle was chosen for convenience in carrying out this analysis. Other parameters such as degree of hydration are easily determined from analysis of the final microstructure. Degree of hydration is defined as the
ratio of reacted cement volume to original cement volume, so that starts at zero when the cement particles are first mixed with water, and ends at a value of one when hydration is complete.
Fig. 1b shows the result of 200 hydration cycles on the initial configuration shown in Fig. 1a. The black is again water-filled pore space, red is unhydrated cement particles, the blue is CH, and the yellow is C-S-H. One advantage of implementation of the model on graphics computers that allow animation is that the user can directly view the microstructural development on the display screen as it is taking place. This ability is invaluable in understanding how the growth rules of the model influence the developing microstructure.
Figure 1b: Same as Fig. 1a but after completion of the hydration simulation. White represents the aggregate, red represents the remaining unhydrated cement, CH is blue, C-S-H is yellow, and the remaining water-filled pore space is black. | <urn:uuid:a2e56b94-8787-4979-b8ee-e242805f2828> | 3.421875 | 1,641 | Academic Writing | Science & Tech. | 40.292297 |
Einstein protocol is a standard used for precisely measuring the distance between two objects in space. The Einstein protocol of finding the distance between two points is sending light point a to point b and then immediately sending a signal, using light, from point b to point a. The calculations done with this data uses the formula D=c(t3–t1)/2.
|This physics-related article is a stub. You can help Wikipedia by expanding it.| | <urn:uuid:58e438ce-ccbd-434b-97aa-65e6dacf49b1> | 4 | 94 | Knowledge Article | Science & Tech. | 61.167526 |
Sea ice in the Arctic continues its record decline, thanks to unusually cloud-free conditions and above-average temperatures. For August 21, the National Snow and Ice Data Center estimated that fully one third of the Arctic ice cap was missing, compared to the average levels observed on that date from 1979-2000. Sea ice extent was 4.92 million square kilometers on August 21, and the 1979-2000 average for the date was about 7.3 million square kilometers. Arctic sea ice has fallen below the record low absolute minimum of 4.92 million square kilometers set in 2005 by about 8%, with another 3-5 weeks of the melting season still remaining. Reliable records of sea ice coverage go back to 1979.
Figure 1. Extent of the polar sea ice on August 21, compared to the average for the date from the 1979-2000 period (pink line). Image credit: National Snow and Ice Data Center.
With one third of the Arctic ice cap already gone, and another month of melting to go, we need to consider what effect this will have on weather, climate, and sea level rise. Well, we don't need to worry about sea level rise, since the polar sea ice is already in the ocean, and won't appreciably change sea level when it melts. However, the remarkable melting of the ice cap will likely lead to unusual weather patterns this fall and winter. The lack of sea ice will put much more heat and moisture into the polar atmosphere, affecting the path of the jet stream and the resultant storm tracks. Expect a much-delayed arrival of winter to the Northern Hemisphere again this year, which may lead to further accelerated melting of the ice cap in future years.
Last week, I remarked that the most recent images from the North Pole webcam show plenty of melt water and rainy conditions near the Pole. It turns out that was misleading, since the webcam is on a ship that was headed towards the pole, but had not reached it. There have been rainy conditions at the Pole this summer, and there is some open water there, but this is not uncommon in summer. Shifting ice frequently opens up leads (cracks) with open sea water at the Pole. It was one of these open leads that British swimmer Lewis Gordon Pugh swam in for 18 minutes this July to draw attention to global climate change.
Figure 2. Total rainfall from August 10-22 as estimated by NASA's TRMM satellite.
To get an idea of the magnitude of the flooding that has hit the Midwestern U.S. during the past ten days, take a look at the total amount of rain from August 10-22 (Figure 2). We can blame Tropical Storm Erin for the rain in Texas and Oklahoma (up to 11 inches), and for the nine flooding deaths that occurred in those states. However, the unbelievable rain amounts in excess of 20 inches in Minnesota and Wisconsin were primarily due to a frontal system--with the help of some copious moisture pumped northwards by the counter-clockwise circulation around Erin while it spun over Oklahoma.
There are no threat areas in the Atlantic to discuss. Two of our four reliable forecast models, the NOGAPS and ECMWF, are predicting that a tropical depression could form off the coast of Nicaragua on Sunday. The models forecast that this system would move inland over Nicaragua and Honduras by Monday.
I'll have an update on Saturday morning.
Bulldozer trying to clear sand and debris from Norman Manley Highway(Airport Road)
The flood is over, now the cleanup | <urn:uuid:74841e3e-1208-4052-b619-c66f0a748607> | 3.375 | 721 | Personal Blog | Science & Tech. | 54.80869 |
Pluto is the ninth planet from the sun, but not so long
ago, it was the eighth planet. About every 220 years, Pluto switches places
with Neptune, becoming the 8th planet. This happened from
February 7, 1979 through February 11, 1999 when Pluto took over Neptunes
orbit. The reason this happened was that Plutos orbit was stretched out
and tilted causing it to cross with Neptunes orbit. Cylde W. Tombaugh
made the discovery of the planet Pluto on February 18, 1930.
Cylde Tombaugh was able to make this discovery by taking
pictures of the solar system at different times (about one and two weeks
apart). The idea was that Clyde Tombaugh could compare the pictures and try
to notice any differences. The result of this experiment was the discovery
of Pluto. Pluto being so small made it difficult to find. It has one moon
(also known has a satellite) called Charon. In fact, Pluto is so small it
can fit inside the United States.
Occasionally Pluto will cross in front of a reasonably
bright star, making the planet more visible. The last bright star to cross
in front of Pluto occurred in June 1988 and provided the first direct
evidence of Pluto's atmosphere.
If you were to stand on the planet Pluto it would be hard
to see because it is so dark. The only light you might see is the sun, but
it would look more like a very small bright star. From Earth scientists say
that Pluto is a big floating snowball. | <urn:uuid:382c8c3b-c663-4516-82d7-b33363dad470> | 3.875 | 321 | Knowledge Article | Science & Tech. | 63.217059 |
Introduction to HTTP Handlers
An ASP.NET HTTP handler is the process (frequently referred to as the "endpoint") that runs in response to a request made to an ASP.NET Web application. The most common handler is an ASP.NET page handler that processes .aspx files. When users request an .aspx file, the request is processed by the page via the page handler.
The ASP.NET page handler is only one type of handler. ASP.NET comes with several other built-in handlers such as the Web service handler for .asmx files.
You can create custom HTTP handlers when you want special handling that you can identify using file name extensions in your application. For example, the following scenarios would be good uses of custom HTTP handlers:
RSS feeds To create an RSS feed for a site, you can create a handler that emits RSS-formatted XML. You can then bind the .rss extension (for example) in your application to the custom handler. When users send a request to your site that ends in .rss, ASP.NET will call your handler to process the request.
Image server If you want your Web application to serve images in a variety of sizes, you can write a custom handler to resize images and then send them back to the user as the handler's response.
HTTP handlers have access to the application context, including the requesting user's identity (if known), application state, and session information. When an HTTP handler is requested, ASP.NET calls themethod on the appropriate handler. The handler's ProcessRequest method creates a response, which is sent back to the requesting browser. As with any page request, the response goes through any HTTP modules that have subscribed to events that occur after the handler has run. For more information about the processing of Web server requests, see .
An HTTP handler can be either synchronous or asynchronous. A synchronous handler does not return until it finishes processing the HTTP request for which it is called. An asynchronous handler runs a process independently of sending a response to the user. Asynchronous handlers are useful when you need to start an application process that might be lengthy and the user does not need to wait until it finishes before getting a response from the server.
Built-in HTTP Handlers in ASP.NET
ASP.NET maps HTTP requests to HTTP handlers based on a file name extension. Each HTTP handler enables processing of individual HTTP URLs or groups of URL extensions within an application. ASP.NET includes several built-in HTTP handlers, as listed in the following table.
ASP.NET Page Handler (*.aspx)
The default HTTP handler for all ASP.NET pages.
Web service handler (*.asmx)
The default HTTP handler for Web service pages created using ASP.NET.
ASP.NET user control handler (*.ascx)
The default HTTP handler for all ASP.NET user control pages.
Trace handler (trace.axd)
A handler that displays current page trace information. For details, see.
Creating a Custom HTTP Handler
To create a custom HTTP handler, you create a class that implements theinterface to create a synchronous handler or the to create an asynchronous handler. Both handler interfaces require you to implement the property and the ProcessRequest method. The IsReusable property specifies whether the object (the object that actually calls the appropriate handler) can place your handlers in a pool and reuse them to increase performance, or whether it must create new instances every time the handler is needed. The ProcessRequest method is responsible for actually processing the individual HTTP requests.
Creating a File Name Extension
When you create a class file as your HTTP handler, you can have your handler respond to any file name extension that is not already mapped in IIS and in ASP.NET. For example, if you are creating an HTTP handler for generating an RSS feed, you can map your handler to the extension .rss. In order for ASP.NET to know which handler to use for your custom file name extension, the extension of the handler's class file must be mapped in IIS to ASP.NET, and in your application to your custom handler.
By default, ASP.NET maps the file name extension .ashx for custom HTTP handlers, in the same way that it maps the .aspx extension to the ASP.NET page handler. Therefore, if you create an HTTP handler class with the file name extension .ashx, the handler is automatically registered with IIS and ASP.NET.
If you want to create a custom file name extension for your handler, you must explicitly register the extension with IIS and ASP.NET. The advantage of not using the .ashx file name extension is that your handler is then reusable for different extension mappings. For example, in one application your custom handler might respond to requests that end in .rss, and in another application it might respond to requests that end in .feed. As another example, your handler might be mapped to both file name extensions in the same application, but might create different responses based on the extension.
Asynchronous HTTP Handlers
Asynchronous HTTP handlers allow you to start an external process, such as a method call to a remote server, and then continue the processing of the handler without waiting for the external process to finish. During the processing of an asynchronous HTTP handler, ASP.NET places the thread that would ordinarily be used for the external process back into the thread pool until the handler receives a callback from the external process. This can prevent thread blocking and greatly improve performance, because only a limited number of threads can be executed at once. If a number of users request synchronous HTTP handlers that rely on external processes, the operating system can quickly run out of threads because many threads are blocked and waiting for an external process.
When you create an asynchronous handler, in addition to implementing the IHttpAsyncHandler interface, you must implement theto initiate an asynchronous call for processing individual HTTP requests. You must also implement the method to run cleanup code when the process ends.
Custom IHttpHandlerFactory Classes
The IHttpHandlerFactory class receives requests and is responsible for forwarding a request to an appropriate HTTP handler. You can create a custom HTTP handler factory by creating a class that implements the IHttpHandlerFactory interface. Creating a custom handler factory can allow finer control over the processing of an HTTP request by creating different handlers based on run-time conditions. For example, with a custom HTTP handler factory, you can instantiate one HTTP handler for a file type if the HTTP request method is PUT, and another if the method is GET. | <urn:uuid:c7d6092e-31b3-4dcb-a419-11c0428df55a> | 2.8125 | 1,345 | Documentation | Software Dev. | 56.410261 |
The Flick of a Switch
Rora is a gene that produces a transcription factor -- a type of regulatory protein that binds to DNA and can turn gene expression on or off like the flicking of a switch.
Rora, once it is turned on, activates the transcription of a gene that encodes another transcription activator known as Bmal-1, which is one of the known circadian genes. Bmal-1 drives the transcription of a protein called cryptochrome, which subsequently inhibits the ability of Bmal-1 to activate cryptochrome's own transcription. This feedback loop is what keeps the body entrained to a 24-hour day.
Since Bmal-1 is so crucial to keeping the body's clock entrained, finding something like Rora, which alters Bmal-1's expression, is significant and suggests that Rora is also part of the mammalian clock. But the scientists wanted to go further and prove that Rora protein plays a role in the circadian rhythms inside a living creature.
They observed a mutant murine model that has a defective Rora gene. This murine model is called "staggerer" because its genetic defect causes a characteristic loss of coordination.
As it turns out, the staggerer model with a defective Rora gene also has a defect in its ability to regulate its circadian clock. The team of researchers showed that staggerers have aberrant circadian rhythyms and a shortened clock that is only 23.2 hours long. This situation is sort of like a grandfather clock that cannot keep good time and runs too fast because it has a faulty spring balance.
"What we are showing is that circadian clocks are composed of interlocking feedback loops," says Kay. The overlapping feedback, says Kay, is probably there for a number of reasons. It makes the clock more robust and resilient to change. It means that there is more than one cycle in which changes to clock genes can affect changes to other genes, and therefore the clock can be reset more easily.
Contact: Keith McKeown
Scripps Research Institute | <urn:uuid:ab3e25f2-2763-4c2a-90f5-71b1028f7d38> | 3.609375 | 423 | Knowledge Article | Science & Tech. | 46.883269 |
Strength of Yarn by Spinning
Date: Winter 2011-2012
Cotton yarn (thread) is created by spinning multiple cotton fibers. Why does this spinning make the yarn so strong?
The strength of cotton yarn is not a property of cotton per se. Rather it is a property of fibers being in parallel (side-by-side) rather than in series, one after another. If you have a number of fibers in parallel (say 100), if one fiber breaks the other 99 can take up the force. The entire assembly only reduces in strength by 1% (that is 99 out of 100). It takes a lot stronger assembly for fibers in series. One failure and the entire assembly fails. Added to this is the strength provided by the intertwining of the fibers, which provide some ability to stretch the intertwined fibers. That mechanism is lost with a single fiber. A similar mechanism operates with electrical circuits. An array of wires in parallel can carry a lot more current than a single large wire.
Mathematically, this is expressed by the formulas: Parallel = 1/R = SUM(1/ri) and Series R = SUM(ri).
So this behavior is not just a property of yarns, but is a property of configuration, that is, Parallel vs. Series.
Most individual fibers are already very strong as made by the plant,
stronger per unit cross-section than the final thread usually gets.
The question is how to combine them into larger strands so that:
a) the fibers are mostly stretched out in the direction of the strand, and
b) when one fiber ends and another begins, a third fiber bridges the gap and is somewhat attached to both.
Spinning is the mechanical process which has these effects.
I cannot really explain why it accomplishes them, perhaps you can think about it.
The "attached" in (b) starts as mere friction + bends + partial entanglement.
This can actually be enough, but the thread is a bit fuzzy with loose ends sticking out.
Later if "sizing" is added to the thread, it glues some of the fibers to each other as well,
at places where they cross and touch. It probably makes the strength more reliably high.
Yarn and other threads are spun from fibers of a certain size. Obviously, for wool, the size of the fiber depends on the length of the hair sheared from the sheep. The reason for spinning the fibers into yarn is to force the fibers to be in contact with each other. The more surface area the fibers expose to each other, the greater the “sticking” surface there is between each fiber. Spinning the fibers compresses them against one another and increases friction between them. The fibers, in this case, are more difficult to pull apart and the net result is the yarn is made stronger. You can demonstrate this with two jump ropes. Place them next to each other so that they are touching all along the edges. They will easily pull apart with no pressure between them. Tighten some clamps (like those used to clamp paper) so that the ropes are in tight contact with each other, and they will be more difficult to slide past each other. The surfaces of the ropes are rough, and when they touch, they have friction between them. Frictional forces tend to increase with pressure, and if you twist the ropes together, they will experience some compressive forces between them. This force all along the surface will increase friction and make them more difficult to pull apart. Note, however, if you have two strands of slippery spaghetti that coil together, they will slip apart. Here, friction is not as great as in the rough surface of a rope or a wool fiber. A knot in a rope uses friction in such a way that as you pull two ropes apart the knot will compress and increase its strength.
One problem you have with two ropes coiled together is that they will tend to unravel and lose their binding strength with each other. In a yarn, you wind multiple fibers distributed all throughout the length of the yarn. They wrap around each other and serve to prevent the ends from unraveling. In this way, you can have short strands of fiber woven into an assembly that is strong.
Actually, I don't think that spinning itself, makes the cotton fibers any
stronger. What it does, is to merge all the fibers into a single thread in
a way that allows each fiber to equally share the tension.
Click here to return to the Material Science Archives
Update: June 2012 | <urn:uuid:2b8a11f4-aefa-46ee-83fa-904d67de0db9> | 3.6875 | 934 | Academic Writing | Science & Tech. | 60.629521 |
Stupid Command Line Tricks
The Basics of
perl understands a bunch of command line switches. Some of them, like
-f, you will probably never use. Others, like
-d, you might use all the time. The
-M switch is somewhere in between. You might use it in the most trivial case, but it can probably do a lot more than you know it can.
The general use case is this:
The general effect is that "
use Carp::Always::Color;" is injected at the beginning of the program to be run, as if it had been in the source itself. It's great for things that affect the global execution environment, like Carp::Always, but it's got a bunch of other little uses.
If you want to write a one-liner that needs an import, for example, you can use the equals sign:
The string after the
= is passed to List::Util's
import routine. If it has commas, the string is split on commas and the result is passed in.
This is how local::lib's one-liner form works! local::lib has a tricky
import routine, and you pass it a path name by using
import is called with no arguments, because libraries given to the
-M switch are loaded with
use Module;. You can skip the imports by using
use Module ();.
Usually, if I want to know what version(s) of a module I have installed, I run which_pm, but when I don't have it – or more likely, when giving advice to someone on IRC, I can use
-M. If I think someone's seeing a bug because they've got an old version of Sub::Exporter, I can tell them to run:
Most of the time, we load libraries with
no is useful, too. (Instead of calling
import, it calls
no is used by libraries that are loaded to forbid undesirable behavior. indirect lets you ban indirect method invocation. circular::require lets you ban circular module loading.
In your source for Foo.pm, you might write:
...but circular::require affects the global behavior of
require. You probably don't want to always load it everywhere. You just want to use it sometimes when testing. You can't say
-Mcircular::require, because that would use
use instead of
no. To get
no, just throw in another dash:
The code above will be silent if Foo has no circular requirements, and emit a string of warnings of it has them.
So, for testing versions, I showed:
For importing, I showed:
What if we want to combine these? They're not really compatible. What if we want to pass something more complex than a list of strings? The bits after the equals sign aren't
evaled, so they can't be complex.
The secret lies in understanding how that version-testing code worked. The space after "String::Truncate" and everything following that is just tacked into the template
use MODULE REST ;
This means you can put almost anything there. Do you want to import a renamed version of
trunc, but only if you have a recent version?
Your program will be run with the following line of code prepended:
This is where it gets a little nutty:
perl doesn't care whether you give it more than one statement. You can put all kinds of stuff in
-M's argument. In fact, if the stuff you want to put in is important, but the module isn't, you can just use something meaningless like
use 5 just ensures that you're under Perl 5 or later, and then the code you actually wanted to inject is added.
-M is a powerful tool for all kinds of code injection when you don't want to actually start editing the code you're running. Even better, once you've finished working with it, you can just delete your shell history file, and nobody will know the kind of horrible things you did with it. | <urn:uuid:0e28d9cb-a3d0-470e-9ce5-754979c63bed> | 2.890625 | 847 | Documentation | Software Dev. | 64.458953 |
The propagation of a laser beam is well described by a wave model and diffraction. A laser beam is the output beam from an optical cavity and, for technically well designed lasers, the beam can be described by the Hermitian Gauss modes for the transverse electro-magnetic field with an amplitude distribution given by the function TEMnk.
The fundamental mode TEM00 describes a beam with Gaussian intensity distribution propagating along a well defined axis. The higher order modes describe more complex field distributions. All TEMnk modes are immune to diffraction in the sense that they retain their shape. A Gaussian beam for example remains a Gaussian beam. The modes TEMnk are orthogonal and we can describe arbitrary beam shapes using the Hermite Gauss modes as a basis.
We can detect the position of such a laser beam, for example by a split detector which shows an change in the intensity balance when the beam moves. This allows is very sensitive, and allows measurements well below the optical wavelength. After eliminating technical noise sources, such as vibrations or imperfections in the laser, we are then only limited by quantum noise. Even for the perfect laser we have noise in the position of the mode: a laser beam: it can never go in a perfectly straight line.
In our work we encode and transfer information in the spatial properties of the beam. The advantage is that simple physical parameters map directly on the specific modes: for example displacement corresponds to the real part of the TEM01, tilt corresponds to the imaginary part of the TEM01, waist size corresponds to the real part of TEM02, waist position to the imaginary part of TEM02. Using mirrors and lenses we can control direction and displacement and the wavefront curvature an in this way write information into few independent modes TEM01, TEM10, TEM02, TEM20, each with one pair of conjugate parameters. At the same time we can sense the effect of a sample, which changes the beam spatially, directly by measuring the modulation of the TEMnk modes.
We have shown that for every optical measurement and detector, we can find an optical mode which contains all the information and noise associated with this measurement. If we can match the mode that contains the information with the mode of detection we have found the best possible detection system, which allows detection with 100% efficiency. By using squeezed light in such a transmission system we can send information that contain quantum correlations. This is an alternative to the well established techniques for single photons.- system. Using the multimode system with several degrees of freedom we can transmit multimode quantum information.
The output of two squeezed laser beams, operating on the same mode, can be combined to a pairs of entangled modes. This is well established for Gaussian beam and has been used in many applications, such as dense coding and teleportation. We can now extend this to spatial systems where the entangled properties are for example position and tilt. | <urn:uuid:8afa94d7-efeb-486e-9951-998938bc02a6> | 3.296875 | 609 | Academic Writing | Science & Tech. | 36.710348 |
Cassini sheds light on cosmic particle accelerators 18 February 2013 During an unusually strong blast of solar wind arriving at Saturn, the Cassini spacecraft detected particle acceleration to ultra-high energies, similar to what takes place around supernova explosions. Read more
The Cassini-Huygens mission is a NASA/ESA/ASI mission to explore the Saturnian system. The ESA component consists largely of the Huygens probe, which entered the atmosphere of Saturn's largest moon, Titan, and descended under parachute down to the surface. The Cassini spacecraft is undertaking an extensive exploration of the Saturnian system with its rings and many satellites. Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the 'Cassini Equinox Mission', in September 2010. A second extended mission, called the 'Cassini Solstice Mission' will continue until September 2017; this will allow scientists to study the Saturnian system until the summer solstice is passed in May 2017. By the time this new extension is completed the Cassini mission will have covered (since it arrived in the system) one half of a Saturnian year.
Saturn's giant storm reveals the planet's churning atmosphere 25 October 2012 A giant storm whirling on Saturn for the past two years has given planetary scientists new clues about the planet's atmosphere. The study is based on infrared observations from the Cassini orbiter and ground-based telescopes. Read more
Cassini-Huygens Participating Scientists Announcement of Opportunity 2013 08 March 2013 The scientific community is invited to submit proposals for Participating Scientists (PS) to the Cassini-Huygens mission. This Announcement of Opportunity is published jointly by ESA, NASA, and ASI. This year proposals are being taken via a two-step process. Step-1 proposals are required. The deadline for submission of Step-1 proposals is 26 March 2013. Full proposals are due 3 May 2013. Read more
Cassini Scientist for a Day 2012 Competition - Results 04 March 2013 Students from across Europe have been selected as winners of the Cassini Scientist for a Day 2012 competition. Coordinated by ESA, national competitions were held in several European countries, with more than 1000 entries. An equivalent competition was run by NASA for schools in the US. Read more | <urn:uuid:0601e3f6-b0af-470f-a5ff-5cffde71003d> | 2.90625 | 475 | Content Listing | Science & Tech. | 35.213967 |
By Andrew Freedman (Climate Central)
Recently I reported on a study showing links between rapid Arctic climate change and shifts in the jet stream throughout the Northern Hemisphere. The study, led by Jennifer Francis of Rutgers University, suggests that there may be an Arctic connection to some extreme weather events, particularly ones that result from stuck, or "blocked," weather patterns.
The study shows that by changing the temperature balance between the Arctic and mid-latitudes, rapid Arctic warming is altering the course of the jet stream, which steers weather systems from west to east around the hemisphere. The Arctic has been warming about twice as fast as the rest of the Northern Hemisphere, due to a combination of human emissions of greenhouse gases and unique feedbacks built into the Arctic climate system.
The jet stream, the study states, is becoming “wavier,” with steeper troughs and higher ridges. As a result, weather systems are progressing more slowly, raising the chances for long-duration extreme events, like droughts, floods, and heat waves.
This video looks great on an IPad, just select and expand. Enjoy! | <urn:uuid:fc5c01a6-f137-452c-a6a9-3135f40cb07d> | 3.671875 | 232 | Truncated | Science & Tech. | 38.715179 |
Imagine a New York autumn with almost no red or orange -- just brown, brown, brown. Experts say that could be the scene 50 years from now if people don’t start paying more attention to what’s going on with the shrubs, bushes and saplings in the forest.
The groundhog predicted an early spring this year -- and he isn't the only one. Scientists now say that thanks to climate climate change, spring may arrive up to 17 days earlier in U.S. forests during the next century and that, could have an unexpected silver lining.
John Weeks discusses the first widespread freeze of the year, and the gorgeous day that proceeded it. He also explains the significance of microclimates and their undetected presence nearly everywhere we turn. | <urn:uuid:9cf1f1f6-e7c4-48f5-8439-00df3b7fb033> | 2.875 | 156 | Content Listing | Science & Tech. | 64.355938 |
The bright ringlets seen here are populated with microscopic icy particles and are among the brightest features in the rings at high phase angles.
The twisted core of the F ring, at left, is flanked by three fainter ringlets which are, in fact, part of a separate continuous structure that spirals around the planet. Right of center, in the Encke Gap, are three tortured-looking ringlets.
This view looks toward the unlit side of the rings from about 12 degrees above the ringplane.
The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 7, 2006 at a distance of approximately 1.9 million kilometers (1.2 million miles) from Saturn and at a Sun-Saturn-spacecraft, or phase, angle of 163 degrees. Image scale is about 11 kilometers (7 miles) per pixel.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington, D.C. The imaging team consists of scientists from the US, England, France, and Germany. The imaging operations center and team lead (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo. | <urn:uuid:4888f327-5e21-4496-adaf-e266451aa0c0> | 3.34375 | 290 | Knowledge Article | Science & Tech. | 47.866175 |
(Redirected from Protons)
A proton is made up of two up quarks and one down quark. According to the Standard Model of particle physics, quarks are fundamental particles, meaning that they cannot be split into smaller particles.
- ↑ Serway, Beichner: Physics for Scientists and Engineers, 5th edition
- ↑ Krane: Modern Physics, 2nd edition | <urn:uuid:8833227d-55b9-44c2-aeb4-c3588a6128bb> | 3.375 | 82 | Knowledge Article | Science & Tech. | 34.976029 |
Migration is the seasonal movement of animals from one habitat to another. Animals migrate between their wintering and breeding habitats. Some creatures that you would recognize that migrate are: whales, fish, butterflies, turtles, and of course birds. Some animals travel incredible distances on these annual journeys. The longest migration of any known animal is that of the Arctic Tern, which travels 15,000 miles from the North Pole to the South Pole and back again each year!
Migrating birds follow established migratory routes. Migration in North America is essentially north-south along four major routes known as "flyways:" Pacific, Central, Mississippi and Atlantic. Many birds migrate between North and South America and are referred to as Neo-tropical migrants (Neo = new + tropical). Most of these birds migrate 500 miles non-stop over the Gulf of Mexico. Other birds island hop down the eastern coast of the U.S. (see maps below). Upon arrival in southern wintering grounds, birds have been described as nothing more than "feathered skeletons" having depleted much of their fat and muscle reserves.Up to 12 million neotropical migrant birds have passed over Cape Cod in one night, embarking on a non-stop journey of 80 to 90 hours. Radar stations in Bermuda and Antigua pick up waves of approaching migrants.
Why do birds Migrate?
- Seasonal cycles of climate or insect abundance attract corresponding cycles of breeding, flocking, and migratory relocation.
- Migration benefits are species or population specific and include the need to escape inhospitable climates, probable starvation, social dominance, shortage of nest/roost sites, or competition for food.
- Another way to view the same ecological forces is that migrants aggressively exploit temporarily available opportunities.
- Traveling to different habitats enables birds to find plenty of food throughout the year. For example, in the winter, when food sources are limited in northern areas, waterfowl such as geese fly south to areas that have mild weather and abundant food.
How do birds navigate over such large tracts of land and ocean?
It has been demonstrated that birds rely on several different cues – visual landmarks, geomagnetic field, solar compass, skylight polarization pattern/stars, and olfaction - for their orientation and navigation across vast stretches of land. See below for research that demonstrated these phenomena.
Schlicte and Schmidt-Koenig (1971) fitted well-trained homing pigeons with frosted contact lenses that limited image formation beyond 3 meters. The blind birds flew over 170 km directly back to their lofts. Of course some crashed into the loft and some missed the loft altogether!
Emlen and Penny (1964) took Adelie Penguins from their coastal breeding rookeries to interior Antarctica and released them. On cloudy days the penguins wandered about randomly. -However, when the sun was shining they headed north-northeast towards the coast, compensating for the sun’s counterclockwise movement in the Southern Hemisphere by correcting their orientation 15 degrees per hour clockwise relative to the sun’s position…By the way the sun changes continuously by 15 degrees per hour.
Franz and Eleanore Sauer (1957) demonstrated the use of stars for navigation by birds. By caging Garden Warblers in a Planetarium, the Sauers showed birds oriented north in the "spring" and south in the "fall" under simulated night skies. When they turned off the stars the birds became disoriented. When they rotated the north-south axis of the planetarium 180o the warblers also reversed their compass headings.
Merkel and Wiltschko (1965) showed European Robins could orient in solid steel cages without celestial cues. They also demonstrated that the robins reversed their orientation when the magnetic field imposed on the cage was reversed.
Continuing the magnetism work Keeton (1971) demonstrated that free flying homing pigeons wearing bar magnets often did not orient properly on cloudy days vs. control pigeons wearing brass bars. Keeton concluded that the pigeons use the sun preferentially to the earth’s magnetic field on sunny days.
Finally, Walcott and Green (1974) fitted homing pigeons with electric caps that produced a magnetic field through the bird’s head. Under overcast skies, reversing the field’s direction by reversing the current in the cap caused free-flying pigeons to fly in the direction opposite their original course. | <urn:uuid:1931cc5a-df8e-4ed5-ab9c-f6a0ae36a1d3> | 4.125 | 919 | Knowledge Article | Science & Tech. | 42.030925 |