text large_stringlengths 148 17k | id large_stringlengths 47 47 | score float64 2.69 5.31 | tokens int64 36 7.79k | format large_stringclasses 13 values | topic large_stringclasses 2 values | fr_ease float64 20 157 |
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Silly newbie question - Caret character (^)
ldo at geek-central.gen.new_zealand
Tue Nov 9 23:32:32 CET 2010
In message <mailman.778.1289325458.2218.python-list at python.org>, Terry Reedy
> I've been wondering why C programmers keep writing code susceptible to
> buffer overruns ;=).
I am continually disappointed with the ‘do as I say, not as I do” attitude
among people offering up sample code. I remember writing to one contributor
to a programming magazine many years ago, about his admonition not to simply
copy-and-paste sample code, to point out that he had done exactly that
(complete with bug).
The main sticking point seems to be error checking; for some reason, writers
of sample code seem to believe the code is “clearer” if you leave this out,
when in fact all real-world applications of the illustrated techniques would
include the error checks. So what do they end up illustrating? Nothing
relevant to the real world.
Is this why so many real-world programs fail to check for errors in
important places, and segfault or behave unpredictably instead of gracefully
reporting a problem?
More information about the Python-list | <urn:uuid:809b4dfe-a415-4e37-9763-634d235e06fd> | 2.796875 | 283 | Comment Section | Software Dev. | 56.518148 |
Supports a value type that can be assigned null like a reference type. This class cannot be inherited.
Assembly: mscorlib (in mscorlib.dll)
Thetype exposes the following members.
A type is said to be nullable if it can be assigned a value or can be assigned null, which means the type has no value whatsoever. Consequently, a nullable type can express a value, or that no value exists. For example, a reference type such as String is nullable, whereas a value type such as Int32 is not. A value type cannot be nullable because it has enough capacity to express only the values appropriate for that type; it does not have the additional capacity required to express a value of null.
The class provides complementary support for the Nullable<T> structure. The class supports obtaining the underlying type of a nullable type, and comparison and equality operations on pairs of nullable types whose underlying value type does not support generic comparison and equality operations.
Use nullable types to represent things that exist or do not exist depending on the circumstance. For example, an optional attribute of an HTML tag might exist in one tag but not another, or a nullable column of a database table might exist in one row of the table but not another.
You can represent the attribute or column as a field in a class and you can define the field as a value type. The field can contain all the valid values for the attribute or column, but cannot accommodate an additional value that means the attribute or column does not exist. In this case, define the field to be a nullable type instead of a value type.
Boxing and Unboxing
When a nullable type is boxed, the common language runtime automatically boxes the underlying value of the Nullable<T> object, not the Nullable<T> object itself. That is, if the HasValue property is true, the contents of the Value property is boxed. If the HasValue property is false, null is boxed. When the underlying value of a nullable type is unboxed, the common language runtime creates a new Nullable<T> structure initialized to the underlying value.
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers. | <urn:uuid:ac3b5071-6238-45c0-a9bc-5448176fa124> | 3.015625 | 473 | Documentation | Software Dev. | 38.401903 |
Whales are incredibly diverse marine mammals, ranging from small pygmy whales to the blue whale, the largest animal in the world.
There are two categories of whales, baleen whales and toothed whales. Baleen whales have a broom-like structure in their mouths that allows them to filter feed on small organisms while toothed whales use teeth to capture prey.
Whales are magnificent creatures, with some species able to migrate thousands of miles and dive to the depths of the oceans. But today, a variety of harmful human activities threatens their continued existence.
Whales and Commercial Fishing
Commercial fisheries use a variety of technologies to capture their targeted fish, including pots, trawls and gill nets. Unfortunately, these technologies often catch non-targeted species, such as sea turtles and whales.
For example, the critically endangered North Atlantic right whale can become entangled in lobster pots or gillnets fishing along the Atlantic coast of the U.S. Oceana works to decrease bycatch defending the U.S. legislation that protects marine mammals and pushing the National Marine Fisheries Service to reduce marine mammal bycatch.
Whales and Sonar
Sonar (SOund NAvigation and Ranging) is a technology that uses sound waves to gather information underwater and can aid in navigation, communication, and detection of objects. Used by the Navy, commercial fisheries, scientists and many others, sonar is a powerful tool for a variety of applications.
However, the sound emitted by active sonar can interfere with the behavior of toothed whales, which use echolocation or biosonar to communicate and to find prey. It can also cause these whales to become disoriented, rise to the surface too rapidly, and die as a result.
Despite their intelligence and importance in the marine ecosystem, whales have been hunted for their meat for hundreds of years. This practice caused whale populations around the world to crash, and most countries outlawed commercial whaling due to its undeniable impact on whale populations. Sadly, a handful of countries continue to hunt whales. | <urn:uuid:92b62cbd-d7b5-4abb-a7da-8b7de54fe8c5> | 3.734375 | 422 | Knowledge Article | Science & Tech. | 30.429968 |
If you take an aluminum rod and tap one end with a hammer, the disturbance travels along the rod at the speed of sound in aluminum, which is about 5000 m/s. This speed is what determines the frequency of the ringing that you hear. The speed is many orders of magnitude less than c. If it were higher than c for some other substance (one that was very stiff and had a very low density), then it would be possible to use the vibrations to transmit information faster than the speed of light, which is forbidden by relativity; it leads to paradoxes, since there would be frames of reference in which the signal was received earlier than it was transmitted. This tells us that relativity imposes limits on the properties of materials. It isn't surprising that such limits exist, since the properties of materials are determined by the electrical interactions between atoms, and those interactions propagate at no more than c.
A similar example from general relativity is that we can't use a rope to retrieve an object from inside the event horizon of a black hole. If the rope were to be strong enough to support even its own weight, then the speed of sound in the rope would be greater than c, which is impossible.
Although relativity doesn't allow the existence of perfect rigidity as a passive property of a substance, it still allows us to define a notion of rigidity called Born rigidity (Born 1909). In a Born-rigid object, an observer at rest relative to a certain part of the object sees that part of the object as always maintaining a constant distance between neighboring parts. Born rigidity can't be a passive property of a material; to achieve Born rigidity, one has to carry out a pre-planned program of applying forces to different parts of the object as a function of time.
The Herglotz-Noether theorem says that Born rigidity is incompatible with the kinds of free rotations and translations that we expect nonrelativistically to be able to apply to a rigid body. It is not possible for a Born-rigid body to change its angular velocity, and if such a body is rotating, its center of mass can't be accelerated.
Historically, this kind of thing was studied intensively ca. 1910 both because of the desire to resolve paradoxes such as the Ehrenfest paradox and because people were trying to make a theory of electrons as extended objects, in order to avoid the infinite energy inherent in the field of a point charge.
Max Born. Die Theorie des starren Elektrons in der Kinematik des Relativitätsprinzips. (The theory of the rigid electron in relativistic kinematics) Annalen der Physik (Leipzig), Annalen der Physik 30, 1; also referred to as 335 (11), 1-56 (vierte folge, band 30), 1909. | <urn:uuid:7cb381f2-dcfc-4e50-9d0d-a842c88a9a9f> | 3.703125 | 591 | Q&A Forum | Science & Tech. | 39.824292 |
Sadly, global warming has become politicized. Putting all the data together is not easy. However, there are ways of approaching the matter objectively. In the end, the conclusions each of us draw will depend on our different perceptions of risks and who w
On a clear night, some regions of the sky, such as the Milky Way, have higher densities of stars than others.
The Royal Society of London's first major publication was in 1665. It didn't anticipate this work would be a harbinger for a great leap in understanding of life. Within 15 years this august scientific society would find it necessary to abandon its ideas a
Comparing the general organization of the bodies of living and extinct organisms shows evidence of both lineal relationships and improvisation. Likewise, the DNA of organisms tells the same story.
Living things are wondrous for many reasons, but two stand out. First, all living organisms are related to one another. Comparative anatomy, embryology, DNA, the fossil record, the structure of molecules from which life is built and the metabolic processe
Monte Carlo is recognized as a Mecca for high stakes gambling. In the realm of computer software, the term "Monte Carlo" refers to a method of doing simulations of complex phenomena where odds play an essential role.
Most scientific endeavors require the application of some kind of mathematics. Foremost, it is important for modeling a wide variety of phenomena. And, where observations are quantifiable (measurable), it is used to characterize data.
A school science project designed to illustrate the solar system might include an assemblage of Styrofoam balls held together by wires. This is, quite literally, a model of the actual solar system in an easily visualized representation.Scientists develop
Upgrades performed on the Hubble telescope last year are now yielding images of objects that are 13 billion light years away. But how do astronomers know how far away those objects are?
It is awesome to imagine the principal elements making up our bodies, carbon, oxygen, nitrogen and a few others, have their origins in the incredibly hot cores of stars.The bulk of the physical universe is composed of basic elements. Ninety-two elements a
The universe would seem incomprehensible if knowledge of matter and physical laws was contradictory on vary large and small scales. Hypotheses on the workings of the universe must demonstrate consistency across all scales of size.Understanding the smalles
It is unfortunate the news media and the general public are so vulnerable to sensational claims made by charlatans and undisciplined purveyors of unproven medical practices. I was recently reminded of this by a CBS 60 Minutes program.The story was recou
We hear about the importance of reducing our carbon footprint. This primarily refers to limiting our generation of carbon dioxide gas by burning fossil fuels. Carbon dioxide is the principle "greenhouse gas" contributing to global warming.The story of how
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Science Fair Project Encyclopedia
- anxn + an−1xn−1 + иии + a1x + a0 = 0
where n is a positive integer called the degree of the polynomial, every coefficient ai is an element of F, and an is nonzero. If the field F is the field Q of rational numbers and K is an algebraically closed field then the algebraic numbers relative to Q are simply called algebraic numbers. The algebraically closed field in which these numbers lie can be the complex numbers C, but sometimes other fields are used. Any such algebraic closure is unique up to field isomorphism, but may differ in topological properties. Considered purely as a field it is unique, and it is either this abstract field devoid of topology or the closure of the rationals in the complex numbers which is most often called the field of algebraic numbers.
All rationals are algebraic. A real number which is not rational may or may not be algebraic; for example irrational numbers such as 21/2 (the square root of 2) and 31/3/2 (the cube root of 3 divided by 2) are also algebraic because they are the solutions of x2 − 2 = 0 and 8x3 − 3 = 0, respectively. But most real numbers are not algebraic; examples of this are π and e. If a complex number is not an algebraic number then it is called a transcendental number. So, for instance i, the imaginary unit, is an algebraic number since it satisfies x2 + 1 = 0; however ii is transcendental by the Gelfond-Schneider theorem; this number is e-π/2, which shows that eπ is also transcendental.
If an algebraic number satisfies such an equation as given above with a polynomial of degree n and not such an equation with a lower degree, then the number is said to be an algebraic number of degree n.
The field of algebraic numbers
The sum, difference, product and quotient of two algebraic numbers is again algebraic, and the algebraic numbers therefore form a field, called the algebraic closure of the field of algebraic numbers. It can be shown that if we allow the coefficients ai to be any algebraic numbers then every solution of the equation will again be an algebraic number. This can be rephrased by saying that the field of algebraic numbers is algebraically closed. In fact, it is the smallest algebraically closed field containing the rationals, and is therefore called the algebraic closure of the rationals.
Numbers defined by radicals
All numbers which can be written using a finite number of additions, subtractions, multiplications, divisions, and nth roots (where n is a positive integer) are algebraic. The converse, however, is not true: there are algebraic numbers which cannot be written in this manner. All of these numbers are solutions to polynomials of degree ≥ 5. This is a result of Galois theory. An example of such a number would be the unique real root of x5 − x − 1 = 0
An algebraic number which satisfies a polynomial equation of degree n with leading coefficient an = 1 (that is, a monic polynomial) and all other other coefficients ai belonging to the set Z of integers, is called an algebraic integer. Examples of algebraic integers are 3√2 + 5 and 6i - 2.
The sum, difference and product of algebraic integers are again algebraic integers, which means that the algebraic integers form a ring. The name algebraic integer comes from the fact that the only rational numbers which are algebraic integers are the integers, and because the algebraic integers in any number field are in many ways analogous to the integers. If K is a number field, its ring of integers is the subring of algebraic integers in K, and is frequently denoted as OK.
Special classes of algebraic number
- Gaussian integer
- Eisenstein integer
- Quadratic irrational
- Fundamental unit
- Root of unity
- Gaussian period
- Pisot-Vijayaraghavan number
- Salem number
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:be64c03e-2c22-4cd8-818f-a30f936e253c> | 3.734375 | 911 | Knowledge Article | Science & Tech. | 41.624635 |
Giant walking stick insect (Megaphasma dentricus)
Megaphasma dentricus is the largest walking stick species in North America. The insect measures about 75mm and 150 mm. The insect takes the appearance of a twig or small branch. The insect is found in red to brown color and in some cases they appear in shades of green color. This insect mainly found in forests and grasslands in the Midwest area. The female walking stick insect lay eggs in a hidden place on the ground in dead or dying leaves and foliage. The eggs will hatch in the spring and the siblings are found to be edible green color. The walking stick insect is found active during the late hours of the day so their movement is not noticeable to any predator. There are about 2500 species in the world. The walking stick insect emits a chemical spray from a gland that could cause temporary blindness and substantial pain. This insect has the capacity to reproduce parthenogenetically (females can clone themselves).
Walking stick insect resembles as a symbol of relationship between the insect and plant. | <urn:uuid:f009cb19-45b4-44a2-a372-b6df7150c5e1> | 3.1875 | 217 | Knowledge Article | Science & Tech. | 56.1738 |
Problem 4: Thompson Seedless Grapes
The Thompson seedless grape is triploid, with three copies of each chromosome. Which phase of the cell cycle would you expect triploid cells to be unable to complete.
The Biology Project
Department of Biochemistry and Molecular Biophysics
University of Arizona
Revised: August 2004
Contact the Development Team | <urn:uuid:15352d2f-f328-4f9e-9017-cea78f5ddc45> | 2.796875 | 75 | Tutorial | Science & Tech. | 22.633462 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
December 24, 1998
Explanation: Looking down from atop a Delta II rocket blasting skyward, solid fuel boosters fall away (left) and the Earth's limb slides into view. These pictures from the launch of the Mars Climate Orbiter were taken as it climbed away from Cape Canaveral Air Station Space Launch Complex 17 on December 11. This spacecraft won't arrive at Mars in time for Christmas though, as its cruise to the red planet will require about 9 1/2 Earth months to complete. Once it does get there it will use aerobraking to help establish a polar science mapping orbit for studying the martian atmosphere. The orbiter is also scheduled to act as a communications relay for the soon to be launched Mars Polar Lander.
Authors & editors:
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U. | <urn:uuid:a78ee87a-bd43-47e2-8eb8-413862381293> | 3.3125 | 219 | Knowledge Article | Science & Tech. | 52.832141 |
2011 | 2010 | 2009 | 2008 | 2007 | 2006 | 2005 | 2004 | 2003 | 2002 | 2001
A study released on May 11, 2007 provides some of the first solid evidence that warming-induced changes in ocean circulation at the end of the last Ice Age caused vast quantities of ancient carbon dioxide to belch from the deep sea into the atmosphere. Scientists believe the carbon dioxide (CO2) releases helped propel the world into further warming.
As cities around the world confront the urgent challenge of climate change, there is growing recognition that effective mitigation and adaptation policies must rely on sound scientific research and data. In an effort to facilitate and build the connections between science and policy, experts from academic and research institutions around the world have formed the Urban Climate Change Research Network, which will be officially launched at an international symposium held on May 10-11 at Columbia University.
Global Research Technologies, LLC (GRT), a technology research and development company, and Klaus Lackner from Columbia University have achieved the successful demonstration of a bold new technology to capture carbon from the air. The "air extraction" prototype has successfully demonstrated that indeed carbon dioxide (CO2) can be captured from the atmosphere. This is GRT's first step toward a commercially viable air capture device.
The Earth Institute at Columbia University is pleased to announce the 2007-2008 Marie Tharp Fellows -- four women who are making noteworthy contributions to the study of the natural world.
The findings of a new study, appearing in Science, show that there is a broad consensus amongst climate models that the Southwest will dry significantly in the 21st Century and that the transition to a more arid climate may already be underway. If these models are correct, the levels of aridity of the recent multiyear drought, or the Dust Bowl and 1950s droughts, will, within the coming years to decades, become the new climatology of the American Southwest.
The first global study to identify populations at greatest risk from rising sea levels and more intense cyclones as a result of climate change will be published in the peer-reviewed journal Environment and Urbanization. The study was conducted by scientists at the Center for International Earth Science Information Network and the International Institute for Environment and Development.
On February 20, 2007, Jeffrey D. Sachs, Director of the Earth Institute at Columbia University, and former U.S. Vice President Al Gore spoke to a packed house in Columbia's Low Library Rotunda to address the next steps needed to mitigate the global climate crisis.
As a significant step toward tackling climate change, an unprecedented group of companies and organizations from around the world have endorsed a bold post-Kyoto framework for affecting change at the levels of policy and industry, particularly in regard to creating sustainable energy systems necessary for achieving economic growth.
In Africa, millions are affected by climate variability and its role in agriculture, disease and economic development, yet climate information often fails to reach them. The partners behind a new publication would like to change this.
Although Latin America has generally low infant mortality rates (which is a widely-used measure of poverty), this map shows the incidences are unevenly distributed throughout the region, exposing the relationship between patterns of human well-being and broader geographic constraints.
A former energy and policy journalist from Cameroon talks about the impacts of climate on development and poverty alleviation, and how the M.A. program in Climate and Society at Columbia University became the best academic experience in his life
According to an article in the Guardian (UK), the Conservatives in the United Kingdom's government will unveil plans to spend $1bn a year on malaria treatment until the disease is eradicated worldwide. George Osborne, the UK's shadow chancellor, delivered the pledge at the end of his three-day visit to Uganda with Jeffrey D. Sachs, director of the Earth Institute and leading development economist. | <urn:uuid:62e9e7b6-1dff-423a-9f09-517002cdb152> | 3.734375 | 778 | Content Listing | Science & Tech. | 24.216351 |
July 15, 2004: Astronomers have directly measured the mass of a single star the first time such a feat has been accomplished for any solitary star other than our own Sun. The measurement has been done on a small red star located some 1,800 light-years from Earth. Knowing the masses of stars is important in understanding stellar evolution.See the rest:
Astronomers scan for microlensing events to look for evidence of dark matter in the outer fringes, or halo, of our galaxy. Believed to make up a significant chunk of our universe, dark matter may be partly made up of celestial objects that are too faint to see because they are very cool. These objects, referred to as "Massive Compact Halo Objects," or MACHOs, may be lurking in the halos of galaxies. They may include black holes, compact stars, and failed stars called brown dwarfs. If some dark matter were in the form of MACHOs, then its presence could be detected by the gravitational influence MACHOs would have on light from distant stars. If a MACHO object passes in front of a star in a nearby galaxy, such as the Large Magellanic Cloud, then the gravitational field of the MACHO will act like a lens, causing the brightness of the background star to increase as the MACHO passes by.
Astronomers also have discovered that gravitational microlensing events can yield other important information about a star, including whether the "lensed" star has planets circling it. Microlensing also provides information on background stars that are normally too dim and too far away to be seen with telescopes.
Until now, the only way astronomers have successfully measured the mass of a star is by studying its gravitational effect on another star. Both stars are bound together by gravity in a binary-star system.
With the gravitational microlensing technique, astronomers determine the mass of a star by measuring its effect on beams of light passing by the star. Microlensing events, however, occur in about one in 10 million stars. So, determining the mass of a star with this method is difficult because astronomers must use a powerful computer to scan millions of stars to find a microlensing event. Astronomers also must be able to image both stars in order to calculate the distance to them, or they must look for subtle changes due to the motion of the Earth around the Sun during the microlensing event. The distances are needed to determine the mass of the foreground star. | <urn:uuid:ce2eec42-90e2-4710-b457-41aa4a4f103e> | 3.890625 | 507 | Knowledge Article | Science & Tech. | 41.428184 |
A retrovirus called HERV-H, which inserted itself into the human genome millions of years ago, may play an important role in pluripotent stem cells, according to a new study published in the journal Retrovirology by scientists at UMass Medical School. Pluripotent stem cells are capable of generating all tissue types, including blood cells, brain cells and heart cells.
The discovery, which may help explain how these cells maintain a state of pluripotency and are able to differentiate into many types of cells, could have profound implications for therapies that would use pluripotent stem cells to treat a range of human diseases.
"What we've observed is that a group of endogenous retroviruses called HERV-H is extremely busy in human embryonic stem cells," said Jeremy Luban, MD, the David L. Freelander Memorial Professor in HIV/AIDS Research, professor of molecular medicine and lead author of the study. "In fact, HERV-H is one of the most abundantly expressed genes in pluripotent stem cells and it isn't found in any other cell types."
In the study, Dr. Luban and colleagues describe how RNA from the HERV-H sequence makes up as much as 2 percent of the total RNA found in pluripotent stem cells. The HERV-H sequence is controlled by the same factors that are used to reprogram skin cells into induced pluripotent stem (iPS) cells, a discovery that garnered the 2012 Nobel Prize in Physiology or Medicine. "In other words, HERV-H is a new marker for pluripotency in humans that has the potential to aid in the development of iPS cells and transform current stem cell technology," said Luban.
When a retrovirus infects a cell, it inserts its own genes into the chromosomal DNA of the host cell. As a result, the host cell treats the viral genome as part of its own DNA sequence and begins making the proteins required to assemble new copies of the virus. And because the retrovirus is now part of the host cell's genome, when the cell divides, the virus is inherited by all daughter cells.
In rare cases, it's believed that retroviruses can infect human sperm or egg cells. If this happens, and if the resulting embryo survives, the retrovirus can become a permanent part of the human genome, and be passed down from generation to generation. Scientists estimate that as much as 8 percent of the human genome may be comprised of extinct retroviruses left over from infections that occurred millions of years ago. Yet these sequences of fossilized retrovirus were thought to have no discernible functional value.
"The human genome is filled with retrovirus DNA thought to be no more than fossilized junk," said Luban. "Increasingly, there are indications that these sequences might not be junk. They might play a role in gene expression after all."
An expert in HIV and other retroviruses, Luban and his colleagues were seeking to understand if there was a rationale behind where, in the expansive human genome, retroviruses inserted themselves. Knowing where along the chromosomal DNA retroviruses might attack could potentially lead to the development of drugs that protect against infection; better gene therapy treatments; or novel biomarkers that would predict where a retrovirus would insert itself in the genome, said Luban.
Turning these same techniques on the retrovirus sequences already in the human genome, they discovered a sequence, HERV-H, that appeared to be active. "The sequences weren't making proteins because they had been so disrupted over millions of years, but they were making these long, noncoding RNAs," said Luban.
Specifically, the HERV-H sequence was making abundant amounts of RNA in human embryonic stem cells—and only stem cells. In total, there are more than 1,000 HERV-H retrovirus genomes scattered throughout the human genome. The Luban lab also found high levels of HERV-H RNA in some iPS cells. Other iPS cells, perhaps those lines that were not sufficiently reprogrammed to pluripotency, had lower levels of the HERV-H RNA, another indication that HERV-H may be an important marker for pluripotency.
Interestingly, the HERV-H genes that were expressed in human pluripotent stem cells are only found in the human and chimpanzee genomes, indicating that HERV-H infected a relatively recent ancestor to humans, said Luban.
"Once upon a time HERV-H was an invader to our genome and perhaps caused diseases like AIDS or cancer," said Luban. "Now it seems that a kind of détente has been reached. Not only that, but this ancient invader may one day be exploited by clinicians to cure people of a wide range of diseases using stem cell therapies."
Luban and colleagues will next try to determine the specific mechanisms by which HERV-H contributes to pluripotency.
About the University of Massachusetts Medical School
The University of Massachusetts Medical School has built a reputation as a world-class research institution, consistently producing noteworthy advances in clinical and basic research. The Medical School attracts more than $250 million in research funding annually, 80 percent of which comes from federal funding sources. The work of UMMS researcher Craig Mello, PhD, an investigator of the prestigious Howard Hughes Medical Institute (HHMI), and his colleague Andrew Fire, PhD, then of the Carnegie Institution of Washington, toward the discovery of RNA interference was awarded the 2006 Nobel Prize in Physiology or Medicine and has spawned a new and promising field of research, the global impact of which may prove astounding. UMMS is the academic partner of UMass Memorial Health Care, the largest health care provider in Central Massachusetts. For more information, visit www.umassmed.edu.
Jim Fessenden | Source: EurekAlert!
Further information: www.umassmed.edu
Further Reports about: blood cell > brain cell > cell type > chromosomal DNA > DNA > embryonic stem > embryonic stem cell > human embryonic stem cell > human genome > iPS cells > Medical Wellness > Memorial > Nobel Prize > pluripotent stem > pluripotent stem cells > Retrovirus > RNA > skin cell > stem cells
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Version: 2008-11-27 (fedora - 04/07/09)
Section: 2 (Appels système)
NAMEgethostname, sethostname - get/set hostname
int gethostname(char *name, size_t len);
int sethostname(const char *name, size_t len);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
gethostname(): _BSD_SOURCE || _XOPEN_SOURCE >= 500
sethostname(): _BSD_SOURCE || (_XOPEN_SOURCE && _XOPEN_SOURCE < 500)
DESCRIPTIONThese system calls are used to access or to change the hostname of the current processor.
sethostname() sets the hostname to the value given in the character array name. The len argument specifies the number of bytes in name. (Thus, name does not require a terminating null byte.)
gethostname() returns the null-terminated hostname in the character array name, which has a length of len bytes. If the null-terminated hostname is too large to fit, then the name is truncated, and no error is returned (but see NOTES below). POSIX.1-2001 says that if such truncation occurs, then it is unspecified whether the returned buffer includes a terminating null byte.
RETURN VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
- name is an invalid address.
- len is negative or, for sethostname(), len is larger than the maximum allowed size.
- (glibc gethostname()) len is smaller than the actual size. (Before version 2.1, glibc uses EINVAL for this case.)
- For sethostname(), the caller did not have the CAP_SYS_ADMIN capability.
CONFORMING TOSVr4, 4.4BSD (these interfaces first appeared in 4.2BSD). POSIX.1-2001 specifies gethostname() but not sethostname().
NOTESSUSv2 guarantees that "Host names are limited to 255 bytes". POSIX.1-2001 guarantees that "Host names (not including the terminating null byte) are limited to HOST_NAME_MAX bytes". On Linux, HOST_NAME_MAX is defined with the value 64, which has been the limit since Linux 1.0 (earlier kernels imposed a limit of 8 bytes).
Glibc NotesThe GNU C library does not employ the gethostname() system call; instead, it implements gethostname() as a library function that calls uname(2) and copies up to len bytes from the returned nodename field into name. Having performed the copy, the function then checks if the length of the nodename was greater than or equal to len, and if it is, then the function returns -1 with errno set to ENAMETOOLONG; in this case, no null-terminator is included in the returned name.
Versions of glibc before 2.2 handle the case where the length of the nodename was greater than or equal to len differently: nothing is copied into name and the function returns -1 with errno set to ENAMETOOLONG.
SEE ALSOgetdomainname(2), setdomainname(2), uname(2)
COLOPHONThis page is part of release 3.19 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.
-+- Angelo, sur fr.rec.photo -+- | <urn:uuid:423327e3-db58-43f3-b27f-276c4be81940> | 2.828125 | 793 | Documentation | Software Dev. | 50.220057 |
Name: gonzo sulivan
Date: 1993 - 1999
What I want to know is, when a meteorite hits the moon, I notice that
the crater is still there but what happens to the meteorite? The same thing in
Arizona, where there is a big crater, what happened to that meteorite?
The meteorite breaks up into little pieces; some of it may
also vaporize. Many pieces of the one responsible for the
Arizona crater have been found.
Click here to return to the Astronomy Archives
Update: June 2012 | <urn:uuid:489364ca-3a65-41b1-9274-78c1c676d7ab> | 3.0625 | 115 | Audio Transcript | Science & Tech. | 43.934485 |
Phone Book Friction
I am attempting to do a Grade 12 physics project and chose
the topic of Phone book Friction as shown in an episode of
MythBusters. The situation is that the pages of 2 phone books are
interwoven and produces an almost inseparable book. The MythBusters
crew found that 8000 lbs of force was necessary to pull the books
apart. I am trying to find an answer as to why the phone books are
inseparable, focusing of course on friction. Could someone give me
an answer as to why this is? Preferably with some calculations to
back up the explanation.
I will give you the basis of an equation; you can work on the
calculation from it. But you will see that the force to separate
telephone books interlaced as you describe will be considerable.
A good empirical model for friction is that its magnitude is given by
Where (mu) is a dimensionless coefficient that is a property of the
surfaces in contact, and N is the "normal" force pushing them
together. In the case of your telephone books, the relevant
quantities would be a mu for phone book paper against phone book
paper, and the normal force would probably be best modeled as the
weight of phone book above the page. So each page would have a
different N, depending on what fraction of the phone books are on top of it.
That force (mu)N in particular is probably not very large. However,
there are many pages in a phone book, and each one has two
sides. So the force required to separate the phone books would not
be the frictional drag on one side of a page, but the SUM of the
drag forces on BOTH sides of ALL the pages of a book!
I believe you will see that for even small values of mu and N, the
friction force to overcome is quite large when a book has hundreds of pages!
Richard E. Barrans Jr., Ph.D., M.Ed.
Department of Physics and Astronomy
University of Wyoming
Click here to return to the Physics Archives
Update: June 2012 | <urn:uuid:809e1522-55f3-4967-959a-c620b184d412> | 2.875 | 453 | Q&A Forum | Science & Tech. | 58.367934 |
The number n is amicable if it belongs to an amicable pair. Two numbers n and m are called an amicable pair if the sum of all positive divisors of n is equal to the sum of all positive divisors of m and both are equal to n + m.
It all started with perfect numbers which are amicable with themselves. Those numbers adopted social virtues and qualities; for the parts of each of them have the power to generate the other. See also sociable numbers. | <urn:uuid:84474bc6-0d64-48bd-81a8-2884ff5f3011> | 2.953125 | 102 | Knowledge Article | Science & Tech. | 58.201176 |
If you took high school chemistry, you probably did a simple experiment in which you dipped pH test paper into beakers bearing various liquids and watched the strip change colors. If it was acidic, the paper turned toward the red end of the color spectrum; if it was basic, it darkened toward the violet end.
If you took more advanced chemistry, you might have learned that bases are substances that can donate electron pairs, and that acids are substances that can accept them. The point is that the two types of chemicals are polar opposites. Until now, according to researchers at the University of California-Riverside, who have successfully made acidic compounds act like bases. | <urn:uuid:f5828354-881b-45cd-abbb-fa34c8a5860d> | 3.578125 | 134 | Knowledge Article | Science & Tech. | 38.566522 |
This Example shows you how to Change the Content of a node in a DOM document. JAXP (Java API for XML Processing) is an interface which provides parsing of xml documents. Here the Document BuilderFactory is used to create new DOM parsers. These are some of the methods used in code given below for adding attribute:-
Element root = doc.getDocumentElement():-direct access to the root of the DOM document.
NodeList childnodelist = root.getChildNodes():-created a childnodelist and get the collection of child nodes of this node.
Xml code for the program generated is:-
Output of the program:-
Old e-mail id: firstname.lastname@example.org
New e-mail id: @Rose.com
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | <urn:uuid:8a5ec29b-2b3c-46f1-bd30-6f1a1de2e052> | 2.71875 | 202 | Documentation | Software Dev. | 51.674719 |
Dung beetles are a relatively modern group of beetles and their fossils only extend back to 40 million years ago. They belong to the family Scarabaeidae and are also known as scarabs. They are scavengers, which feed on dung and other decaying organic matter, and play an invaluable role in keeping the veld clean.
The ancient Egyptians revered them as a symbol of renewed life. Khepri was a scarab god of the sun and the important symbolism came from the scarab's rolling his ball of dung then taking it down into the soil from where new life later emerged. Hence Kepri rolled the sun across the sky and buried it each evening, was born anew in the morning and rolled the sun across the sky again. Egyptian priests seem to have thought that the scarabs ball of dung was equivalent to his egg, they believed all sacarbs were male therefore, because he did not need a female for reproduction. They reasoned that if both the sun and a scarab beetle could be reborn in a special container in the ground then why couldn't people. It is now believed by some modern scholars that the Egyptian mummy in its tomb/pyramid was a representation of the pupa of S. sacer in the remains of its ball of dung in the earth. Scarab amulets became immensely popular and remained that way for centuries and are the most common archeological relics from the N. African region.
They are small to large, usually stout-bodied, and are easily recognized by the 3 to 7 segmented fan-like antennal club. Their legs are powerful, particularly the front legs, which are armed with teeth on the outer edge. In some species the legs are adapted to rolling balls of dung to a suitable soft spot, and for digging holes in which the dung is buried. The buried dung serves as a source of food for adult beetles, and also for the larvae when they hatch from eggs laid on the dung-balls.
Each brood ball contains a single egg and is coated in a clay shell. The parent beetles abandon the chamber soon after the eggs have hatched.
The larvae, also called white grubs, are greyish-white to bluish-white in colour, C-shaped, and also feed on decaying organic matter, such as tree stumps, and the roots of plants.
In 1973 a guy called Jo Anderson recorded the action as it happened at a small 1.5 Kg pile of Elephant dung on the African savannah. In two hours that small pile of dung attracted 16 000 dung beetles of various shapes and sizes, who between them had eaten and or buried that dung completely in just those two hours. Typhaeus typhoeus the Minotaur Beetle (A UK species) can dig burrows up to one metre deep
All dung beetles are scarabs, but not all scarabs are dung beeties. For instance, the protea beetle (Trichostetha fascicularis) gathers nectar from various species of proteas.
Dung beetles serve a number of very important ecological functions. The digging activity of tunnelling beetles results in the aeration of soil as well as the transfer of nutrients to the soil by releasing the nutrients in the dung. Also, dung beetles break down dung and prevent flies from breeding in it.
Since cattle and other members of their family (the Bovidae) are not indigenous to Australia. where marsupial herbivores such as kangaroos occur instead, there are very few insects other than flies that feed on their dung. Over the years. flies have reached epidemic proportions in the grazing areas of Australia, and the accumulation of unburied cow-pats has made pastures repellent to domestic stock. In order to control the flies and to destroy the pats, at least four species of South African dung beetles have been introduced into Australia. Unfortunately, the experiment has been only partly successful and the problem is still being investigated.
: The photos from our trip! Overhere! Feel free to use any of these additional letters to correct the spelling of words found in the above post: a-e-t-n-d-i-o-s-m-l-u-y-h-c | <urn:uuid:666ff77f-3e0f-4798-a141-0b498933badf> | 4.0625 | 881 | Knowledge Article | Science & Tech. | 55.580432 |
How CO2 warming is driving climate
What the science says...
In August 2010, Nature published a commentary by Penner et al. which mainly focused on the uncertainty regarding the effect short-lived pollutants (such as aerosols and black carbon) have on the climate. As is often the case, many in the blogosphere misinterpreted and misunderstood the statements and conclusions in the commentary. Not surprisingly, the biggest misinterpretation related to the contribution of anthropogenic greenhouse gases to global warming. Below is the most misunderstood quote, with emphasis on the key word.
"Of the short-lived species, methane, tropospheric ozone and black carbon are key contributors to global warming, augmenting the radiative forcing of carbon dioxide by 65%. Others — such as sulphate, nitrate and organic aerosols — cause a negative radiative forcing, offsetting a fraction of the warming owing to carbon dioxide."
Numerous blogs have (mis)interpreted this statement to mean that carbon dioxide is only causing 35% as much global warming as previously believed. A more accurate reading of the quote is that certain short-lived pollutants cause warming in addition to carbon dioxide - quantitatively, approximately 65% as much warming as CO2. And certain other short-lived species cause a cooling effect which offsets some of this warming.
This is not a new conclusion. The IPCC puts the radiative forcing from CO2 at 1.66 W/m2, compared to the forcing from other greenhouse gases, black carbon, and tropospheric ozone at approximately 1.4 W/m2. Similarly, the negative forcing from aerosols is approximately -1.2 W/m2.
Figure 1: Radiative forcing estimates from the IPCC FAR
Thus if anything, the 65% figure is an underestimate of the contributions of short-lived pollutants to global warming, but this contribution does not change the 1.66 W/m2 radiative forcing from CO2 or the amount of global warming it has caused.
Much ado has also been made about another quote from the commentary:
"Warming over the past 100 years is consistent with high climate sensitivity to atmospheric carbon dioxide combined with a large cooling effect from short-lived aerosol pollutants, but it could equally be attributed to a low climate sensitivity coupled with a small effect from aerosols. These two possibilities lead to very different projections for future climate change."
This statement gets to the main point of the commentary - that there remains significant uncertainty regarding the effect of these short-lived pollutants on the global climate. However, estimates of the planetary climate sensitivity to increasing atmospheric CO2 and other radiative forcings are not solely based on the change in the mean global temperature over the past 100 years. In fact, the climate sensitivity parameter has been estimated through many different methods, including:
- climate models
- recent responses to large volcanic eruptions
- recent responses to solar cycles
- paleoclimate data
- data from the last Glacial Maximum
- and yes, data from the instrumental period
Figure 2: Distributions and ranges for climate sensitivity from different lines of evidence. The circle indicates the most likely value. The thin colored bars indicate very likely value (more than 90% probability). The thicker colored bars indicate likely values (more than 66% probability). Dashed lines indicate no robust constraint on an upper bound. The IPCC likely range (2 to 4.5°C) and most likely value (3°C) are indicated by the vertical grey bar and black line, respectively (Knutti and Hegerl 2008)
Interestingly, Penner et al. find that whether the climate sensitivity parameter is on the low or high end, reducing anthropogenic emissions of the short-lived warming pollutants would achieve a significant reduction in global warming over the next 50-100 years. In the red lines in the Figure 3, they employ a climate model with a sensitivity of 5°C for 2xCO2, slightly outside the IPCC likely range. The blue line is a climate model with a sensitivity of 2°C for 2xCO2, on the lower end of the IPCC range. Note that even with the lower climate sensitivity, the model shows the planet warming 3°C by 2100 in this emissions scenario (see the figure caption for further details).
Figure 3: Global mean temperature measurements (black) and projections based on an IPCC scenario with high emissions (A2) for a climate sensitivity parameter of 5°C (upper red) and 2°C (upper blue). Linearly decreasing the total anthropogenic radiative forcing owing to methane, tropospheric ozone and black carbon — starting in 2010 and achieving pre-industrial levels by 2050 — results in significant near-term climate mitigation (lower blue and red curves) (Penner 2010)
Unfortunately, reducing the short-lived cooling pollutants such as aerosols would cause a warming effect of similar magnitude, and so CO2 remains the primary pollutant of concern. Coincidentally, a group of scientists from NASA GISS just published a paper in Science entitled Atmospheric CO2: Principle Control Knob Governing Earth's Temperature.
Last updated on 17 October 2010 by dana1981. | <urn:uuid:2ad0418c-3d6b-45e8-83be-9727c9e850ab> | 3.53125 | 1,051 | Personal Blog | Science & Tech. | 31.720894 |
Can there be life on the Sun? Again, the speed at which chemical reactions take place is important to the existence of life. At the temperatures near the Sun, 5000 degrees and more, molecules vaporize and fly apart. That is one reason why the Sun is mostly made of atomic Hydrogen, the simplest gas, and there is no solid surface. Molecules, made of two or more atoms, have difficulty staying together long enough to form solid matter.
This is page 18 of 20 | <urn:uuid:d014f318-68e9-48e9-885b-c52dd9ab382d> | 3.203125 | 99 | Truncated | Science & Tech. | 51.364313 |
Conopeum reticulum is an encrusting bryozoan, abundant in the lower intertidal zone and extending down to the shallow subtidal waters of Britain and Ireland. The species is also commonly found in estuarine and brackish environments. C. reticulum forms white patches, which resemble a thin sheet of gauze on stones and other hard-substrata.
Conopeum reticulum has been reported from the coasts of the southern North Sea, including those of the UK, Belgium and the Netherlands. It is thought to occur on most British coasts, but its distribution is imprecisely known.
Colonies grow through asexual budding of new zooids at the periphery.
Species of Conopeum are easily confused with those of the related genus Membranipora. Membranipora species may be distinguished by the presence of a twinned ancestrula (the founding zooid), compared to the single ancestrula of Conopeum species. However, the ancestrula region is frequently missing from colonies, making this character insufficient to distinguish species. Conopeum reticulum has thicker calcification than Membranipora species, and a more apparent gymnocyst and cryptocyst than C. seurati. C. reticulum may also be distinguished from other littoral and sublittoral species in the same family by the presence of paired triangular chambers (kenozooids) at the end of each zooid.
Conopeum and Membranipora species also differ in their ecology. M. membranacea is the only species of its genus to occur in British waters, where it forms extensive colonies, normally on Laminaria. Membranipora tuberculata, which colonises Sargassum, and Membranipora tenuis, a tropical species, are, on rare occasions, washed up on south-western shores of the UK. Both of the British species of Conopeum colonise hard substrata or estuarine plants, but would not be expected to occur on marine algae.
Conopeum reticulum forms white encrusting gauze-like sheets, which often cover an extensive area. Zooids are irregularly oval in shape, and vary in size. The lateral walls of the zooids are heavily calcified, forming a raised rim around the zooid edge. The frontal surface is largely membranous. A narrow, granular section of calcification on the frontal surface (the gymnocyst and cryptocyst) is present, and is thicker than Conopeum seurati. The non-calcified section of the frontal surface (the frontal membrane) and the underlying space (opesia) are elliptical or oval in shape. Occasionally, a number of spines are present around the frontal area.
The operculum, a hinged flap which closes the orifice, is very characteristic in Conopeum species. It has a folded membranous edge and appears as a thick crescent-shaped structure when closed. It is lightly chitnizied and lacks the thin marginal sclerite typical of Membranipora species. In C. reticulum the operculum appears as a broad semicircle, which is light brown, when it is closed.
A pair of specialised triangular zooids (kenozooids), much smaller than other zooids and containing either no polypide or a minute polypide, is present on the distal edge (furthest from the colony origin) of feeding zooids. These kenozooids may vary from the triangular shape in parts of the colony and often become enlarged, apparently increasing in size to fill space along the colony edge which is caused by irregularities in the substratum.
The size of zooids varies greatly, but is frequently between 0.4-0.6 by 0.2-0.3 mm
Conoepeum reticulum may colonise the inner surface of Ostrea valves, in
association with Electra monostachys, Conopeum seurati, or
The distribution of Conopeum reticulum is imprecisely known. It has been recorded from British coasts throughout the country, but is likely to be more common in Wales and south England. It is also known from Irish, Belgian and Danish shores. It is thought not to extend into the Mediterranean
Conopeum reticulum is often found in abundance in the lower intertidal zone, and extends down to shallow subtidal waters. The species can inhabit both marine and freshwater environments, unlike the other British species of Conopeum, C. seurati, which is restricted to brackish water. C. reticulum is able to colonise many different hard substrates and is not usually associated with algal substrates.
The founding zooid (ancestrula) develops into a young colony, and later into an adult colony through asexual budding. Sexually produced embryos develop into larvae which are released into the plankton. Larvae settle after liberation and metamorphose into a single ancestrula.
Like all bryozoans, C. reticulum is a suspension feeder. It feeds on small phytoplankton using ciliated tentacles of the lophophore.
Each fertile zooid successively sheds a large number of eggs which are yellowish – white and measure 0.1 by 0.08 mm. The eggs and spermatozoa are produced from July to September. The larvae of C. reticulum are planktonic cyphonautes which feed and grow to 0.25 by 0.19 mm. The larvae are triangular in shape and laterally compressed and are common in coastal and estuarine plankton from throughout the summer, settling in the late summer and early autumn. | <urn:uuid:d29e4e24-c967-40b7-a83a-da618b80d552> | 3.34375 | 1,211 | Knowledge Article | Science & Tech. | 35.534603 |
SUMMARY: The European Space Agency's Mars Express has relayed images from the NASA Mars rovers for the first time, demonstrating how the robots at Mars can work with each other to keep the data flowing back to Earth. Mars Express flew over the Opportunity rover on August 4, and received 15 images which were stored in the rover's memory. The data was transferred to the ESA's operations centre in Germany, and then passed along to NASA's JPL in Pasadena. This communication was possible because the rovers and Mars Express use the same communication protocols.
What do you think about this story? Post your comments below. | <urn:uuid:99c39eae-efef-46c9-b4a5-b846716be9a3> | 3.484375 | 126 | Comment Section | Science & Tech. | 50.241705 |
Pierre Auger Observatory
|Pierre Auger Observatory|
Province of Mendoza, Argentina
|Altitude||1330 m–1620 m, average ~1400 m|
|Wavelength||330–380 nm UV (Fluorescence detector), 1017–1021 eV cosmic rays (Surface detector)|
|Built||2004–2008 (and taking data during construction)|
|Telescope style||Hybrid (Surface + Fluorescence detectors)|
The Pierre Auger Observatory is an international cosmic ray observatory designed to detect ultra-high-energy cosmic rays: sub-atomic particles traveling at the speed of light and each with energies beyond 1018 eV. In Earth atmosphere, such particle interacts with air nuclei and produces various other particles. These effect particles (called an "air shower") can be detected and measured. But since these high energy particles have an estimated arrival rate of just 1 per km2 per century, the Auger Observatory has created a detection area of 3,000 km2 (1,200 sq mi) — the size of Rhode Island, or Luxembourg — in order to record a large number of these events. It is located in the western Mendoza Province, Argentina, near the Andes.
The observatory was named after the French physicist Pierre Victor Auger. The project was proposed by Jim Cronin and Alan Watson in 1992. Today, more than 500 physicists from nearly 100 institutions around the world are collaborating to maintain and upgrade the site in Argentina and collect and analyse the measured data. The 15 participating countries shared the $50 million construction budget, each providing a small portion of the total cost.
From outer space, ultra-high-energy cosmic rays reach Earth. These consist of single sub-atomic particles (protons or atomic nuclei), each with an energy with energies beyond 1018 eV (about the energy of a tennis ball traveling at 80 km/h). When such a single particle reaches Earth atmosphere, it has its energy is dissipated by creating billions of other particles: electrons, photons and muons, all near the speed of light. These particles spread longitudinal (perpendicular to the single particle incoming route), creating a forward moving plane of particles, with higher intensities near the axis. Such an incident is called a "air shower". Passing through the atmosphere, this plane of particles creates UV light, invisible to the human eye, called the fuorescing effect, more or less in the pattern of straight lightning traces. These traces can be photographed at high speed by specialised telescopes, called Fluorescence Detectors, overlooking an area with at a slight elevation. Then, when the particles reach the Earth surface, they can be detected when they arrive in a water tank, where they cause Cherenkov effect: visible blue light. A sensitive fotoelectric tube, can catch these impacts. Such a station is called a called water Cherenkov Detector or 'tank'. The Augen Observatory has both type of detectors covering the same area, which allows for very precise measurements.
When a air shower hits multiple Cherenkov Detectors on the ground, the direction of the ray can be calculated using basic geometrics. The longitudinal axis point can be determined from the densities in each affected ground station. Depending on the time difference of impact places, the angle of the axis can be determined. Only when the axis would be vertical, all groiund detectors register at the the very same moment in time, and any tilting of the axis will cause a time difference between earlierst and latest touchdown.
Cosmic rays were discovered in 1912 by Victor Hess. He measured a difference in ionisation at different heights (using the Eiffel tower and a Hess-manned hot air balloon), an indication of the atmospheric thinning (so spreading) of a single ray. Influence of the Sun was ruled out by measuring during an eclipse. Many scientists researched the phenomenon, sometimes independently, and in 1937 Pierre Auger could conclude in detail that it was a single ray that interacted with air nuclei, causing an electron and photon air shower. At the same time, the third particle muon was discovered (behaving like an very heavy electron).
In 1967 University of Leeds had developed the water Cherkov detector (basins of stainless steel, 1.2 m deep) and created a 12 km2 detection area Haverah Park using 200 such 'tanks'. They were arranged in groups of four in a triangular Y-shape, each triangle with different dimensions. The observatory worked for 20 years, and produced the main design parameters for the ground detection system at Auger Obeservatory. It was Alan Watson who in the later years lead the research team and subsequently co-initiated Auger Observatory Collaboration.
Meanwhile, from the Volcano Ranch (New Mexico, 1959–1978), the Fly's Eye (Dugway, Utah) and its successor the High Resolution Fly's Eye Cosmic Ray Detector called "HiRes" or "Fly's Eye" (University of Utah), the technique of the Fluorescence Detector was developed. These are optical telescopes, adjusted to picture UV light rays when looking over a surface area. It uses faceted observation (hence the fly's eye reference), to produce pixeled pictures at high speed. In 1992, James Cronin lead the research and co-initiated the Auger Observation Collaboration.
Designing and building
In 1995 at the Fermilab, Chicago, the basic design was made for the ambitious Auger observatory. For half a year, many scientists produced the main requirements, and a cost estimation, for the projected Auger. While the area had to be reduced from 5000 km2 to 3000 km2.
When construction began, a full scale prototype was set up first: the Engineering Array. this array consisted of the first 40 ground detectors and a single fluorescence detector. All were fully equipped. The engineering array operated for 6 months in 2001 as a prototype; it was later integrated into the main setup. It was used to make more detailed design choices (like which type of PMT to use, and tank water quality requirements) and to calibrate.
In 2003, it became the largest ultra-high energy cosmic ray detector in the world. It is located on the vast plain of Pampa Amarilla, near the town of Malargüe in Mendoza Province, Argentina. The basic set-up consists of 1600 water Cherenkov Detectors or 'tanks', (similar to the Haverah Park experiment) distributed over 3,000 square kilometres (1,200 sq mi), along with 24 atmospheric Fluorescence Detector telescopes (FD; similar to the High Resolution Fly's Eye) overseeing the surface array.
The Pierre Auger Observatory is unique in that it is the first experiment that combines both ground detectors and fluorescence detectors at the same site thus allowing cross-calibration and reduction of systematic effects that may be peculiar to each technique. The Cherenkov detectors use three large photomultiplier tubes to detect the Cherenkov radiation produced by high-energy particles passing through water in the tank. The time of arrival of high-energy particles from the same shower at several tanks is used to calculate the direction of travel of the original particle. The fluorescence detectors are used to track the particle air shower's glow on cloudless moonless nights, as it descends through the atmosphere.
To support the atmospheric measurements (FD measurements), supporting stations are added to the site:
- Central Laser Facility station (CLF)
- eXtreme Laser Facility (XLF)
- The four fluorescence detector stations also operate: Lidar, infrare cloud detection (IR camera), a weather station, aerosol phase function monitors (APF; 2 out of four), optical telescopes HAM (one) and FRAM (one)
- Balloon launch station (BLS): until December 2010, wihtin hours after a notable shower a meteorologic balloon was launched to record atmospheric data up to 23 km heigth.
|Ground station array||1600 ground stations
(centerpoint of area)
|Los Leones||6 fluorescence detectors|
|Morados||6 fluorescence detectors|
|Loma Amarilla||6 fluorescence detectors|
|Coihueco||6 fluorescence detectors|
|Observatory campus||central office|
Work is ongoing on upgrades to the observatory, including:
- three additional fluorescence detecting telescopes, capable of covering higher altitudes (HEAT — High Elevation Auger Telescopes)
- two higher-density nested arrays of surface detectors combined with underground muon counters (AMIGA — Auger Muons and Infill for the Ground Array)
- a prototype radiotelescope array (AERA — Auger Engineering Radio Array) for detecting radioemission from the shower cascade, in the frequency range 30-80 MHz
- R&D on detecting microwave emission from shower electrons (frequencies around 4 GHz)
The observatory has been taking production-grade data since 2005 and was officially completed in 2008.
In November 2007, the Auger Project team announced some preliminary results. These showed that the directions of origin of the 27 highest-energy events were strongly correlated with the locations of active galactic nuclei (AGNs). The results support the theory that at the centre of each AGN is a large black hole exerting a magnetic field strong enough to accelerate a bare proton to energies of 1020 eV and higher.
The Pierre Auger Collaboration has made available (for outreach purposes) 1 out of 100 of the ground array "showers" incidents that do not exceed 50 EeV. Higher energy incidents require more physical analysis and are not published this way. The data can be explored at the Public Event Display web site.
In November 2007, it was announced that the observatory had found a correlation between the 27 highest energy events and nearby active galactic nuclei (AGN). This would suggest that these events are triggered by protons that were emitted by objects correlated with the AGN distribution of matter. Acceleration by the large magnetic fields associated with the massive central black holes that form the AGNs is one possibility.
In popular culture
Argentina issued 100,000 postage stamps honouring the observatory on 14 July 2007. The stamp shows a surface detector tank in the foreground, a building of fluorescence detectors in the background, and the expression "1020 eV" in large lettering.
- The Pierre Auger Collaboration: collaborators by institution
- The Auger Collaboration (1995-9-31). "The Pierre Auger Project Design Report". Fermi National Accelerator Laboratory. Retrieved 2013-6-13.
- Abraham, J. et al. (2004). "Properties and performance of the prototype instrument for the Pierre Auger Observatory". Elsevier. doi:10.1016/j.nima.2003.12.012. Retrieved 2013-06-13.
- Ouedec, Karim L. (2011). "Atmospheric Monitoring at the Pierre Auger Observatory – Status and Update". Retrieved 2013-06-12.
- Riesselmann, Kurt (October/November 2007). "On the trail of cosmic bullets". Symmetry 4 (8-9): 16–23.
- Science Magazine; 9 November 2007; The Pierre Auger Collaboration et al., pp. 938 - 943
- Analía Giménez (21 July 2007). "El laboratorio de rayos viaja al mundo en una estampilla". Diario UNO de MENDOZA. Retrieved 2011-06-16. (Spanish)
- "Observatorio Pierre Auger". Foro de Filatelia Argentina. 29 July 2007. Retrieved 2011-06-16. (Spanish)
- November 2007 AGN Press Release
- Correlation of the Highest-Energy Cosmic Rays with Nearby Extragalactic Objects: Science 2007 (subscription required). Arxiv preprint (free but not official).
- Let It Rain Symmetry February 2005
- Official website
- Public Event Display
- Southern site website (Spanish and English)
- COSMUS – visuals for the PAO: includes movies, animated 3d models of cosmic ray showers over the Malargüe site, and stereo photographs.
- ASPERA European astroparticle physics network
- Astroparticle.org – European astroparticle physics portal
- Detecting Cosmic Rays: The Auger Observatory and Frontier Science – Interview with Angela Olinto (video) | <urn:uuid:5fb3da38-8c20-4b68-bde5-8495c65b014c> | 3.4375 | 2,615 | Knowledge Article | Science & Tech. | 36.845111 |
Monckton has updated his silly graph, and now the Cuffey and Clow graph (correctly cited this time around!), has been adapted from the original which represented temperatures in Greenland, to represent Antarctic temperatures. How exactly did he accomplish this impressive feat? The same way he took the original and made it representative of global temperatures. He just changed the labels of the axis. This, ladies and gentlemen, is how SCIENCE is done!
Though I can’t help but wonder if this isn’t just another manifestation of Antarctic warming derangement syndrome.
Perhaps the most ironic aspect of all of these silly graphs form Monckton is that he is able to say with a straight face:
I will be showing some quite startling examples of the deliberate bending, falsification, and in some cases fabrication of scientific data, every single time to create a crisis out of nothing.
I imagine a mirror will be somehow involved. | <urn:uuid:c7a6afa9-6dd8-4373-b366-556a36f68703> | 2.703125 | 192 | Personal Blog | Science & Tech. | 38.395794 |
The break Statement
The break statement terminates the execution of the nearest enclosing loop or conditional statement in which it appears. Control passes to the statement that follows the terminated statement, if any.
In a switch statement, break causes the program to execute the next statement after the switch. Without a break statement, every statement from the matched case label to the end of the switch, including the default, is executed.
In loops, break terminates execution of the nearest enclosing do, for, or while statement. Control passes to the statement that follows the terminated statement, if any.
Within nested statements, the break statement terminates only the do, for, switch, or while statement that immediately encloses it. You can use a return or goto statement to transfer control from within more deeply nested structures. | <urn:uuid:0fb2c9ab-fe71-46b6-8dbb-af16c37016ce> | 3.5625 | 164 | Documentation | Software Dev. | 34.75461 |
This problem is about investigating whether it is possible to start at one vertex of a platonic solid and visit every other vertex once only returning to the vertex you started at.
Can you cross each of the seven bridges that join the north and south of the river to the two islands, once and once only, without retracing your steps?
A Hamiltonian circuit is a continuous path in a graph that passes through each of the vertices exactly once and returns to the start.
How many Hamiltonian circuits can you find in these graphs?
Did you know that ancient traditional mazes often tell a story?
One such story is ancient Celtic tale The Raid of Fraech's Cattle.
The story tells how the hero Conall Cernach helps to rescue
Fraech's magic cows which have been stolen by some warriors. The
valuable cows are being kept with other treasures inside a mountain
fortress, guarded by a mighty serpent. A helpful milk maid lets
Conall into the fortress at night. It appears that the hero and the
serpent may have met before because, instead of attacking Conall,
the snake darts into his waist belt. After releasing the cows and
taking some treasure, Conall lets the snake out of his belt without
harming it and leaves the fortress.
Remembering this story helps to draw the basic maze pattern: The
fortress of the mighty serpent of Val Camonica. To draw it, you
will need a pencil and an eraser.
First draw the stick figure for Conall, wearing his horned hat.
Then draw a spiral, starting over his head, through his middle,
around twice, stopping just before his legs, and close off the
spiral. This is the long serpent passing through his waist belt.
(Don't draw the coils of the snake too close together).
Now erase a the bottom piece of the snake that crosses the
figure, and erase the legs. (Conall slips the snake out of his belt
and leaves the fortress).
Just two inside walls to draw now. First, start at the beginning
of the snake. Go down then up and over the top of the hat. Start a
new line at the very top of the hat. Go down then, up over the line
you just drew. Carefully erase the horns from the hat and the
fortress is complete.
This is a traditional Camonica Valley Maze. This and other mazes
can be found in the book Celtic Design: Maze Patterns by Aidan
For more about mazes why not look at the "
More on Mazes " article. | <urn:uuid:dc3c056c-567d-484d-b57a-93046d08ac78> | 3.328125 | 544 | Tutorial | Science & Tech. | 64.51633 |
is at your service! well some more time..The frog is an amphibian in the order Anura (meaning "tail-less", from Greek an-, without + oura, tail), formerly referred to as Salientia (Latin saltare, to jump). The name frog derives from Old English frogga, (compare Old Norse frauki, German Frosch, older Dutch spelling kikvorsch), cognate with Sanskrit plava (frog), probably deriving from Proto-Indo-European praw = "to jump". Most frogs are characterized by long hind legs, a short body, webbed digits(fingers or toes), protruding eyes and the absence of a tail. Most frogs have a semi-aquatic lifestyle, but move easily on land by jumping or climbing. They typically lay their eggs in puddles, ponds or lakes, and their larvae, called tadpoles, have gills and develop in water. Adult frogs follow a carnivorous diet, mostly of arthropods, annelids and gastropods. Frogs are most noticeable by their call, which can be widely heard during the night or day, mainly in their mating season.
The distribution of frogs ranges from tropic to subarctic regions, but most species are found in tropical rainforests. Consisting of more than 5,000 species described. | <urn:uuid:cf36202a-b771-44a9-ad90-379ba9a73e12> | 3.4375 | 281 | Knowledge Article | Science & Tech. | 50.083333 |
by Vagn Lundsgaard Hansen, chair of EMS--committee on WMY 2000
Raising Public Awareness of Mathematics (RPAMaths) is probably the most important goal originally set for the World Mathematical Year 2000. And there are good reasons for that.
The role of mathematics in society is subtle and not generally recognized in the needs of people in everyday life and most often it remains totally hidden in scientific and technological advancements. The old saying ``The one who lives hidden lives best" is not true in present day society. If a subject becomes invisible, it may soon be forgotten and eventually it may even disappear.
Mathematics has a prominent place in school curricula all over the world and probably nobody can imagine such a fate for our subject. But if we do not constantly care about the image of mathematics, we will see continuing pressures to lower the amount of mathematics at primary schools, secondary schools and at the university level. Mathematics is exciting to many people but at the same time is considered difficult and somewhat inaccessible by more. Since mathematics is a fundamental cornerstone in several diverse areas of society, it is important for civilization as a whole that mathematicians do their utmost to help explaining and clarifying the role of mathematics.
In the back of their minds most people find that mathematics is important, but they may have forgotten why. We have to find ways of informing them. Displaying posters with mathematical messages at public places, making videos, producing booklets, arranging exhibitions and activities related to mathematics, in particular to the contents of the posters, can prove to be very effective in such an endeavour.
Indeed we hope so. On March 3--5, 2000 the European Mathematical Society organized a meeting in Paris between the partners in a contract with the European Commission under the program Raising Public Awareness of Science and Technology, where such things were on the agenda. There are two other partners in the contract, a team in Paris under direction of professor Mireille Chaleyat-Maurel and a team in Bangor, UK, under direction of professor Ronnie Brown. The main impact of the coordinated campaign resulting from the contract should be obtained during the European Science and Technology Week, November 6--12, 2000, but much of the material prepared for the campaign will undoubtedly be useful in many other contexts for years to come.
In the spring of 1999, the European Mathematical Society arranged a competition to encourage the idea of creating posters with a mathematical theme that would catch the eye and be representative of mathematics and its uses. The posters submitted for the competition are now included in a web-gallery: http://www.mat.dtu.dk/ems-gallery .
Several of the posters from the competition have already been used, or will be used, in various contexts. At the moment, I know of such uses of ideas in the posters from the competition in Canada, Germany, France, UK, Italy, Portugal, Spain and Denmark.
The posters from the EMS-competition and several other posters were presented and discussed intensely during the meeting. By the end of the meeting a brainstorm was conducted to bring forward even more ideas.
The Paris team is responsible for the final selection and production of the posters to be used during the European Science and Technology Week. I am confident that the team shall produce some graphically attractive and mathematically interesting posters to the general public. Electronic files of the posters will be made available for use in appropriate contexts.
The production of CD-roms and Video clips was presented by Ronnie Brown from the Bangor team, which is responsible for this part of the contract on RPAMaths. He was assisted by Mike Yates, who is the owner of the company SUMit Software, which will be doing the detailed work on the CD-roms. The progress can be followed on the web site for the project: http://www.bangor.ac.uk/ma/CPM/rpamath . Feedback is encouraged to improve the final result.
The experiences of the Bangor team gained in connection with their 1989 Exhibition `Mathematics and Knots' and the subsequent web site building on sculptures and on knots in 1996-7 (links from the above rpamath site) are most valuable and makes me confident that the part of the RPAMaths project on CD-rom and Video clips will be successful. Also these products will be made available for appropriate uses.
To explain the contents of the posters, CD-roms and Video clips, small booklets will be produced and made available at relevant places.
The EMS-committee of the WMY 2000 is also interested in collecting knowledge of articles about mathematics appearing in major national newspapers in different countries; hopefully such articles can be translated into several languages and be of use in other countries. Material can be sent to me on the address mentioned below.
The RPAMaths project as a whole relies on considerable efforts of individuals in several European countries taking time out of their usual positions to work for this project. The contract with the European Commission is very much appreaciated as a means to get all this working, but clearly it covers only a modest part of the campaign compared to the collected efforts made by individual members of the mathematical community. We are greatly indepted to everybody working on making the World Mathematical Year 2000 a successful year.
Professor Vagn Lundsgaard Hansen Department of Mathematics Technical University of Denmark Building 303 Dk-2800 Kongens Lyngby Denmark V.L.Hansen@mat.dtu.dk
Ronnie Brown and Mike Yates attended from Bangor. We both found the meeting very stimulating in meeting people, and in seeing the current achievements and future plans of our partners.
Mike's company SUMit Software is subcontractor to the project at Bangor, and will be doing the detailed work on the CDRoms, for which there has been considerable discussion on planning. Mike is an Honorary Professor at Bangor, and also Professor Emeritus at Manchester University, where he was Professor of Mathematical Logic till 1980. He now has ten years experience in educational software, part of it working with a strong multimedia company in Liverpool.
Mike has already redeveloped the web site for the project (http://www.bangor.ac.uk/ma/CPM/rpamath). Contributions to this, and comments, are welcomed, especially those which show the broad nature of the collaborations on this project. The web site is important for showing what is being done. Suggestions, comments, files, links,... should be sent to firstname.lastname@example.org.
Ronnie Brown gave a computer presentation explaining the methodological principles underlying the construction of the 1989 Exhibition `Mathematics and Knots' by the Bangor team R. Brown, N.D. Gilbert, T. Porter. These principles were in two parts: (i) structure, and (ii) content.
(i)Structure: The exhibition was designed to be reproducible, transportable, not requiring management and supervision. We were fortunate to have excellent graphic design advice over the design period of four years to attain these ends.
(ii)Content: This we feel was the most original part. The title should really be `Mathematics through Knots', since the aim was to explain some basic methods of mathematics to the general public. Thus part of the intention was to show mathematics as valuable in itself, and to show how the pursuit of these methods and aims led to applications which could not be seen from the start.
We also came to realise that the exhibition format is one of the hardest. It is not enough to show things, or ideas; there has to be an overlying philosophy, an intention on the impression that is to be conveyed to the viewer, and each aspect of the exhibition has to fit with that intention. Each board has to tell a story in itself, as far as possible by graphical means, and yet each board has to be related to the others.
It should now be clear why the development and realisation of this structure took four years!
The methods which were displayed through knots were: representation; classification; invariants; breaking a complicated object or procedure into simple parts; laws; analogy; applications.
Part of the overall aims were: advanced mathematics from an elementary viewpoint; making mathematics concrete.
Putting the exhibition on the web in 1997 allowed the description of these aims, and much other material, to be incorporated into various levels of the hypertext, keeping the original boards at the top level. Thus the web format turns out to be a wonderful and flexible tool.
An unforeseen consequence of making the exhibition was the collaboration with the sculptor John Robinson, and the web sites of his sculptures and the knot exhibition are expected to form a core of the CDROm(s) in preparation for the RPAMath project.
Acknowledgements: The main support for the original exhibition came from COPUS (Committee for the Public Understanding of Science), and for the web presentation from the Philip Trust and the London Mathematical Society.
Back to WMY2000 summary
Back to Newsletter 9 summary | <urn:uuid:a45a55d3-ac3a-4db8-ae03-b2983baa16df> | 2.875 | 1,863 | Audio Transcript | Science & Tech. | 41.58322 |
Population and Agriculture
Math ExtensionPrint this Page
- Subject(s): Mathematics
- Region / Country: Asia & Pacific Islands / People's Republic of China
- Grade Level(s): 3–5, 6–8
- Related Publication: Slide show | A Taste of Tongren
Students will use information from Peace Corps Volunteer Amy Throndsen's slide show about her experience in China, as a springboard for investigating numerical relationships between population and agriculture.
Begin by viewing Amy Throndsen's slide show, A Taste of Tongren, and discussing the central concepts using the accompanying lesson plan, What Can Food Tell Us About a Place? The slide show mentions that China is home to 20% of the world's population, but has only 10% of the world's arable land. Students will use this information as a springboard for investigating numerical relationships between population and agriculture.
- collect, represent, and analyze real-world data
- perform operations to produce figures for comparison
- apply the concept of ratios to human populations and natural resources
- Find the current population of China, the total land area of China, and the percentage of China's land that is arable. Useful links:
- Calculate the number of square kilometers of arable land per person in China.
- Use the same process to calculate the amount of arable land per person in the U.S. and in several other countries of your choice. Create a graph to represent this comparative information.
- How might these figures change with increased population growth and urbanization?
- How do we (or how should we) make up for global resource inequities?
Framework and Standards
- Population and land use changes have the potential to affect global food production and supply.
- Data can help us recognize trends and discrepancies in the real world.
- What can data tell us about real-world situations?
- How should we adapt to inequitable distribution of resources?
Common Core State Standards for Mathematics
- Operations and Algebraic Thinking
- Use the four operations with whole numbers to solve problems.
- Numbers and Operations in Base Ten
- Perform operations with multi-digit whole numbers.
- Ratios and Proportional Relationships
- Understand ratio concepts and use ratio reasoning to solve problems.
- Analyze proportional relationships and use them to solve real-world and mathematical problems. | <urn:uuid:6c65c9a3-4eb8-45c3-8044-9716f357c5a6> | 4.1875 | 489 | Tutorial | Science & Tech. | 30.714881 |
An electrically neutral model airplane is flying in a horizontal circle on a 3.0-m guideline, which is nearly parallel to the ground. The line breaks when the kinetic energy of hte plane is 50.0 J. Reconsider the same situation, except that now there is a point charge of +q on the plane and a point charge of -q at the other end of hte guideline. In this case, the line breaks when the kinetic energy of the plane is 51.8 J. Find the magnitude of the charges. | <urn:uuid:7861358b-f20b-4ead-be28-1d498215df57> | 3.03125 | 110 | Q&A Forum | Science & Tech. | 74.432232 |
Immutable means you cannot change the contents of an object. For String, this means that once a String object has been created, it remains the same for as long as the String object exists. If you need a mutable "string" look at StringBuffer in Java 1.4 and StringBuilder in Java 5 and above.
The reason why String is immutable is mostly memory management I think, but I don't know the exact reason.
Originally posted by Rob Prime: The reason why String is immutable is mostly memory management I think, but I don't know the exact reason.
I can't speak for the engineers that made the decision, but I've heard justification to say that it has more to do with security. Not to mention, Joshua Bloch, a very prominent (ex) Sun engineer who worked on the java class libraries wrote a book called effective java that stated that all classes should be immutable unless there is a good reason for them to be mutable.
Joined: Jul 17, 2006
I can't find anything in the white papers that says why specifically, but consider the following case:
The white papers do specifically say that they followed c++'s example by allowing a string literal, and implicitly creating a new object of type String to represent that literal. i.e. the "quoted string" concept is extended into java.
Now, the java language spec says that two identical string literals are actually the same object -- that is, they have the same identity, the == operation will return true. This is accomplished via the String.intern method. The jvm maintains a pool of Strings. The intern method will insert the string to that pool if it is missing, and if it isn't, it will return the copy of that string that is currently in the pool.
A consequence of this is, if strings were mutable, then changing it from one reference would effect all other references. Consider the following example, which uses pretend methods for modifying a String:
If strings were mutable, the variable hello no longer contained the word "hello". This is a serious problem. Hence, for this reason, Strings must be immutable.
Joined: Jul 17, 2006
The API for string suggests another good reason for strings to be immutable. Since they are immutable, they can be shared (this is basically exactly what I was talking about with the jvm string pool, but has a different consequence).
So, we say that as String is "thread-safe". That means that we can use it on more than one thread without worrying about what is happening to it on another thread.
For example, let us consider a c-style string, for a minute. In c, we know that we need to have \0 at the end of every string, so that we know where the end of the string is.
So lets say we have the string "Hello". On one thread, we decide to append " World" to it. So we start by writing the space (code 32) in index 5, and 'W' in index 6, etc.
Now lets say that after we've put the W in position 6, but before we put the o in position 7, a DIFFERENT thread decides to read the string. But now, the string has no \0 ANYWHERE. So it has no end.
We say that the string is in an inconsistent state, and this is very important in multithreaded programming.
Now, lets say that we cannot modify a string after its been created. Then it can NEVER be in an inconsistent state, so we know that it is thread safe.
This is a very good reason for a String to be immutable.
Yup - memory management may be part of it, but I think the biggest reason is the fact that in C++ a common error was for people to modify a string and forget that other parts of the program still had a reference to that same string, and expected to see it in its original form. I wouldn't say that strings [i]must[/i be immutable, but it's a good way to eliminate a large class of errors. Furthermore, multi-threaded applications have become more and more prominent (even if the users don't manage the threads themselves, e.g. in a servlet container) and sharing data between threads is much simpler if the data is immutable. | <urn:uuid:b9f8bba4-e0e9-4b86-8009-f570654ab1e1> | 3.34375 | 901 | Comment Section | Software Dev. | 63.872518 |
NSW National Parks and Wildlife Service, 2002
1. Current Conservation Status
The Lord Howe Woodhen (Gallirallus sylvestris, Sclater 1869) is listed on Schedule 1 (Part 1) of the Threatened Species Conservation Act 1995 (TSC Act) as an Endangered Species. It is listed as Vulnerable on Schedule 1 (Part 2) of the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The species is classified as Endangered by the IUCN (Baillie and Groombridge 1996).
The Lord Howe Woodhen is endemic to Lord Howe Island, a part of NSW located about 700 km north-east of Sydney in the south-west Pacific Ocean. Originally described as 'common' in the early 1800s, the number of Woodhen had declined to 37 by the late 1970s, restricted to the high plateau of Mount Gower in the southern mountains of the island (Miller and Kingston 1980). This decline heightened concern for the species' future and prompted the implementation of a rehabilitation program. This program included the elimination of feral Pigs (Sus scrofa) from Lord Howe Island and a very productive captive breeding and release program for the Woodhen. As a result of this program, one of the most successful ever implemented for any bird species, the wild population increased between 1980 and 1985 by over 100 to 140 individuals in at least three geographically discrete populations. In April 2002 monitoring survey, 127 individuals were counted, not including the Little Slope site which was not surveyed due to weather conditions (see Section 3.2). | <urn:uuid:a6be8908-fd85-412c-988f-3af1f07d5676> | 3 | 324 | Knowledge Article | Science & Tech. | 44.770718 |
Contact: Susan Hendrix
NASA/Goddard Space Flight Center
Caption: The bottom two black spots on the sun, known as sunspots, appeared quickly over the course of Feb. 19-20, 2013. These two sunspots are part of the same system and are over six Earths across. This image combines images from two instruments on NASA's Solar Dynamics Observatory (SDO): the Helioseismic and Magnetic Imager, which takes pictures in visible light that show sunspots and the Advanced Imaging Assembly, which took an image in the 304 Angstrom wavelength showing the lower atmosphere of the sun, which is colorized in red.
Credit: NASA/SDO/AIA/HMI/Goddard Space Flight Center
Usage Restrictions: None
Related news release: NASA's SDO observes fast-growing sun spot | <urn:uuid:c3257d30-2a16-4c30-82d3-9bd3de7519c7> | 3.609375 | 177 | Truncated | Science & Tech. | 33.721762 |
Hey everyone. I'm still new to python, and programming in general... I'm writing this bit of code that will ask for the user to input a 16 digit card number, and in return scramble the data in some manner... The scrambling isn't the part that is giving me trouble.
I'm using the list feature in python to create an empty list, then have the user input their credit card number, with each digit being a different element in the list. But I can't seem to make that happen. Whenever I then output the numbers, they appear as one long number in the list. I wanted so that each number is shifted individually Here's what I have so far.
#Credit Card Hash
Card_Number = list #Setting up the Card_Number variable as an empty list
i = (input( "Welcome. Please enter your 16 digit credit card number here: ")) #Sets the input from the user as i
Card_Number.append(i) # Adds the input from the user to the empty list of Card_Number
if i < 16 :
print ("Sorry, not enough digits provided. Please enter 16 digits")
else i >16:
print ("Sorry, too many digits provided. Please enter 16 digits.")
else i == 16:
print ("Thank you. Please hold...")
Now this is where I have trouble. How do I get the input to the list to be multiple items instead of just one 16 digit item on the list. For example, if they enter 1234567891234567 I want it to be entered into the list as [1,2,3,4,5,6,7,8,9,1,2,3,4,5,6,7] but when I run this, it becomes just . Any help is appreciated
If you see anything else wrong with the if statements let me know, I had some trouble with them as well. Sometimes the code never gets past the first if statement. Even if I enter a number that's over 16 digits. it still gives me the first if.
Remember what the dor-mouse said; Feed your head. | <urn:uuid:7c2f8f4c-8489-4476-8493-02f30997fb14> | 3.03125 | 446 | Comment Section | Software Dev. | 81.421327 |
P-Element mutagenesis in Drosophila
There has been a long history of innovation and development of tools for gene discovery and genetic analysis in Drosophila melanogaster. This includes methods to induce mutations and to screen for those mutations that disrupt specific processes, methods to map mutations genetically and physically, and methods to clone and characterize genes at the molecular level.Modern genetics also requires techniques to do the reverse — to disrupt the functions of specific genes, the sequences of which are already known. This is the process referred to as reverse genetics.
Discovery of genes based on mutant phenotype is called as Forward genetics, now a days geneticists making use use of the reverse way ,where gene discovery starts with DNA sequence. Reverse genetics techniques are two types one is mostly like forward genetics screens using chemical mutagenesis or P element and other method is directed towards altering the function of gene of interest.targeted gene replacement and RNAi silencing falls into this category.
Today we will take a look at P-element mutagenesis ,as it happens to be most popular among tools of reverse genetics.Chemical mutagenesis is not the popular choice largely because of the lack of efficient and high-throughput methods for detecting mutations.P element mutagenesis a powerful tool to knock down a gene of interest.For gene disruption P element is modified in several ways to suit the experiment.Normal P element 2,907 bp includes a 31-bp inverted repeat at both ends and transposase gene ( required for mobilisation of P element,the transposon) has four exons.
P element needs only few bases including the inverted repeats to do its normal function.Making use of this property and the fact that laboratory strains of Drosophila are devoid of P elements, additionally these insertions are completely stable.Transposition can be induced at will by expressing transposase (by crossing to a fly harboring transposase source)This feature has allowed P-elements to become widely used in mutagenesis, gene tagging and transformation.
There are many P elements are available in stock centers which are mapped,only thing one need to do is order the stock of P element sitting near to your gene of interest ( as P-elements hops in local regions) and provide transposase source for hoping into the gene so that it disrupts its coding region or one can order P elements already sitting in the gene and carry out imprecise excisions.
Imprecise excisions are very easy way of creating mutation in the gene.A marker gene, usually the white (w+) eye-colour genes, is included so that integration and excision can be followed phenotypically.When a fly has this p element the eye colour of fly looks red and when it has excised out of genome eye of fly becomes white.These are the flies of interest and possibly the mutation for the gene.Once the p element has taken the gene region along with it,its difficult for the p element to insert in genome again as it alters the inverted repeat sequence.One can replace one p element by another p element ( Lacz p element to Gal4 containing P element) with this technique.
Thomas Hummel and Christian Klämbt
Drosophila , 97-117, DOI 10.1007/978-1-59745-583-1
Conversion of lacZ Enhancer Trap Lines to GAL4 Lines Using Targeted Transposition in Drosophila melanogaster
Katharine J. Seppa and Vanessa J. Auld
Genetics, Vol. 151, 1093-1101, March 1999
A simple and efficient method to identify replacements of P-lacZ by P-Gal4 lines allows obtaining Gal4 insertions in the bithorax complex of Drosophila.
de Navas L, Foronda D, Suzanne M, Sánchez-Herrero E.
Mech Dev. 2006 Nov;123(11):860-7. (549) | <urn:uuid:ed0d3cb7-e3c1-4865-a5c4-2d686e84fa6c> | 3.515625 | 835 | Truncated | Science & Tech. | 36.518631 |
More than one function may be defined with the same SQL name, so long as the arguments they take are different. In other words, function names can be overloaded. When a query is executed, the server will determine which function to call from the data types and the number of the provided arguments. Overloading can also be used to simulate functions with a variable number of arguments, up to a finite maximum number.
A function may also have the same name as an attribute. (Recall that attribute(table) is equivalent to table.attribute.) In the case that there is an ambiguity between a function on a complex type and an attribute of the complex type, the attribute will always be used.
When creating a family of overloaded functions, one should be careful not to create ambiguities. For instance, given the functions
CREATE FUNCTION test(int, real) RETURNS ... CREATE FUNCTION test(smallint, double precision) RETURNS ...
it is not immediately clear which function would be called with some trivial input like test(1, 1.5). The currently implemented resolution rules are described in Chapter 10, but it is unwise to design a system that subtly relies on this behavior.
When overloading C-language functions, there is an additional constraint: The C name of each function in the family of overloaded functions must be different from the C names of all other functions, either internal or dynamically loaded. If this rule is violated, the behavior is not portable. You might get a run-time linker error, or one of the functions will get called (usually the internal one). The alternative form of the AS clause for the SQL CREATE FUNCTION command decouples the SQL function name from the function name in the C source code. E.g.,
CREATE FUNCTION test(int) RETURNS int AS 'filename', 'test_1arg' LANGUAGE C; CREATE FUNCTION test(int, int) RETURNS int AS 'filename', 'test_2arg' LANGUAGE C;
The names of the C functions here reflect one of many possible conventions. | <urn:uuid:a32dab8c-4b75-4f51-a592-0e111ee4074f> | 3.296875 | 445 | Documentation | Software Dev. | 49.617 |
by Staff Writers
Adelaide, Australia (UPI) Oct 10, 2012
Australian researchers say they've extended Einstein's theory of special relativity to work beyond the speed of light, but caution it only works in the math.
"Our paper doesn't try and explain how this could be achieved, just how equations of motion might operate in such regimes," Jim Hill of the University of Adelaide's School of Mathematical Sciences said.
Einstein's Theory of Special Relativity, published in 1905, explains how motion and speed is always relative to the observer's frame of reference, with an absolute limit being the speed of light.
The study, published in the Proceedings of the Royal Society A, includes mathematical formulas that extend special relativity to a situation where the relative velocity can be infinite, and can be used to describe motion at speeds faster than light.
"About this time last year experiments at CERN, the European center for particle physics in Switzerland, suggested perhaps neutrinos could be accelerated just a very small amount faster than the speed of light; at this point we started to think about how to deal with the issues from both a mathematical and physical perspective," Hill said.
"Questions have since been raised over the experimental results but we were already well on our way to successfully formulating a theory of special relativity, applicable to relative velocities in excess of the speed of light."
However, Hill said, "there is no substantial evidence to suggest that this is presently feasible with any existing transportation mechanisms."
Stellar Chemistry, The Universe And All Within It
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First light: NIST researchers develop new way to generate superluminal pulses
Washington DC (SPX) May 08, 2012
Researchers at the National Institute of Standards and Technology (NIST) have developed a novel way of producing light pulses that are "superluminal"-in some sense they travel faster than the speed of light. The technique, called four-wave mixing, reshapes parts of light pulses and advances them ahead of where they would have been had they been left to travel unaltered through a vacuum. ... read more
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2012 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement| | <urn:uuid:b7402fc1-f2fe-4250-ba83-0b09e13767dd> | 3.546875 | 569 | Truncated | Science & Tech. | 30.620289 |
By popular demand, a few features commonly found in functional programming languages and Lisp have been added to Python. With the lambda keyword, small anonymous functions can be created. Here's a function that returns the sum of its two arguments: `lambda a, b: a+b'. Lambda forms can be used wherever function objects are required. They are syntactically restricted to a single expression. Semantically, they are just syntactic sugar for a normal function definition. Like nested function definitions, lambda forms cannot reference variables from the containing scope, but this can be overcome through the judicious use of default argument values, e.g.
def make_incrementor(n): return lambda x, incr=n: x+incr | <urn:uuid:30bb236d-e2f7-4118-a01d-fa80c58a71dc> | 3.421875 | 151 | Documentation | Software Dev. | 43.512284 |
Every drop counts. As does every effort. Learn how you can contribute to water conservation, aquatic ecosystem restoration, and improved access to drinking water and sanitation around the globe.
More About Freshwater
Learn how to cut gallons from your household use, diet, energy, transportation, and consumer choices.
The average American lifestyle demands 1,800 gallons a day to support, with 70 percent of that going to support our diets—more than twice the global average for daily use.
Where does water sit around the globe? How is it used to produce everyday goods? Test your knowledge about freshwater.
As founder of the Global Water Policy Project, Sandra is recognized as one of the world's most respected authorities on freshwater issues.
Help Save the Colorado River
You can help restore freshwater ecosystems by pledging to cut your water footprint. For every pledge, Change the Course will restore 1,000 gallons back to the Colorado River.
Change the Course Infographic
Check out this infographic and learn how you can conserve water and save the Colorado River, as well as other freshwater ecosystems.
Sandra is a leading authority on international freshwater issues and is spearheading our global freshwater efforts.
He's paddled the Colorado River from its headwaters to the delta, in an effort to bring awareness to this mighty river at risk.
For more than 15 years, Osvel Hinojosa Huerta has been resurrecting Mexico's Colorado River Delta wetlands.
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The Florida manatee is thriving in Kings Bay, and so is tourism. Therein lies the problem.
Inside the Amazon's rush on mahogany, a threatened tree.
The fracking frenzy in North Dakota has boosted the U.S. fuel supply—but at what cost? | <urn:uuid:d88c0f5e-7c89-4404-8583-543089dd6ca3> | 3 | 361 | Content Listing | Science & Tech. | 43.218386 |
Helios 1 was a joint German- American deep space mission to study the main solar processes and solar-terrestrial relationships. Specifically, the spacecraft's instruments were designed to investigate ... phenomena such as solar wind, magnetic and electric fields, cosmic rays, and cosmic dust in regions between Earth's orbit and approximately 0.3 AU from the Sun.
It was the largest bilateral project to date for NASA, with Germany paying about $180 million of the total $260-million cost. Germany provided the spacecraft and NASA the launch vehicles.
After a successful launch, Helios 1 passed within 47 million kilometers of the Sun at a speed of 238,000 kilometers per hour on 15 March 1975, the closest any humanmade object had been to our nearest star. During its mission, the spacecraft spun once every second to evenly distribute the heat coming from the Sun, 90 percent of which was reflected by optical surface mirrors. Its data indicated the presence of fifteen times more micrometeorites close to the Sun than there are near Earth.
Information provided by http://solarsystem.nasa.gov/missions/profile.cfm?Sort=Target&Target... | <urn:uuid:88b747a0-488c-4e8e-89e8-2c03b0a38879> | 3.8125 | 235 | Knowledge Article | Science & Tech. | 53.072473 |
Unpacks from a binary string into an array according to the given
unpack() works slightly different from Perl as the unpacked data is stored in an associative array. To accomplish this you have to name the different format codes and separate them by a slash /.
See pack() for an explanation of the format codes.
The packed data.
Note that PHP internally stores integral values as signed. If you unpack a large unsigned long and it is of the same size as PHP internally stored values the result will be a negative number even though unsigned unpacking was specified. | <urn:uuid:b1955f43-a1a6-4ab5-8028-81e65dda6d7f> | 2.765625 | 117 | Documentation | Software Dev. | 46.091361 |
Go to Tom Ray's home page. Go to the Tierra home page.
Immune hosts now dominate memory, while parasites and susceptible hosts decline in frequency. The parasites will soon be driven to extinction. Medium resolution (35956 bytes). Higher resolution (91814 bytes).
Feel free to reproduce or publish these images, make photo credits to: Anti-Gravity Workshop
The Ancestral Program - consists of three ``genes'' (green solid objects).
The CPU (green sphere) is executing code in the first gene, which causes
the program to measure itself.
Medium resolution (11169 bytes).
Higher resolution (30463 bytes).
A Parasite (blue, two piece object) uses its CPU (blue sphere) to execute
the code in the third gene of a neighboring host organism (green) to
replicate itself, producing daughter parasite (two-piece wire frame object).
Medium resolution (18826 bytes).
Higher resolution (47741 bytes).
A Hyper-parasite (red, three piece object) steals the CPU from a parasite (blue sphere). Using the stolen CPU, and its own CPU (red sphere) it is able to produce two daughters (wire frame objects on left and right) simultaneously. Medium resolution (22537 bytes). Higher resolution (57578 bytes).
These are two images from the VRML Visualization of Network Tierra. This visualization represents the Tierra network environment though the ``eyes'' of the digital organisms themselves. Digital organisms are able to perceive conditions on the net by using the TPing sensory mechanism (sort of like echo location in bats). These images visualize the data provided by TPing.
Wide view of Network Tierra visualization. This is a view of a medium sized Tierra network, with about one hundred participating machines. The machines are located at ATR in Japan, The University of Delaware, The Santa Fe Institute, The Free University of Brusells, and the Swiss Federal Institute in Lausanne. Each machine is visualized as a set of spheres (one orange, one blue, and a few yellow-green), as described above. The network is represented from the perspective of one digital organism, located on a specific machine (in Santa Fe). The spheres representing the hundred machines are arranged onto the surface of a cone, with the point-of-view machine at the tip of the cone (a little below and left of center). The remaining machines are arranged in spirals on the surface of the cone, but with their distance from the tip proportional to the time that it takes the TPing message to cross the net and return. This network transit time is the most meaningful measure of distance on the network, and it is provided with the TPing data. | <urn:uuid:f84b44c3-4f89-4f43-8ac7-28a842cb9447> | 2.765625 | 562 | Content Listing | Science & Tech. | 40.03 |
JAVA & J2EE
A platform-independent, object- oriented programming language used to develop from software applications to web applications.
The Java 2 Platform, Enterprise Edition (J2EE) defines the standard for developing multitier enterprise applications. The J2EE platform takes advantage of many features of the Java 2 Platform, Standard Edition (J2SE), such as "Write Once, Run Anywhere" portability.
Duration of the Course: 72 Hours
Java has a lot of potential to develop and grow especially in Mobile phone applications are very wide scope area where Java is being used for its portability and independence. For existing areas like desktop applications and enterprise applications there are chances for java to gain better role. Java is gaining more popularity in developing embedded applications.
The .NET Framework is a software framework that runs primarily on Microsoft Windows. It includes a large library and provides language interoperability (each language can use code written in other languages) across several programming languages.
Duration of the Course: 72 hours
Survey results confirm that .NET applications are pervasive in large enterprises and their acceptance and dependability is continuing to increase. As .NET emerges as an enterprise tool, more companies are starting to shift towards an even application environment, trying to integrate .NET into previous development platforms. More companies are starting to create a mixed architectural application offering by having both a Java developing platform and a .NET one brings more advantages than simple Java.
PHP and MySQL
PHP is a general-purpose open source server-side scripting language originally designed for Web development to produce dynamic Web pages. It is one of the first developed server-side scripting languages to be embedded into an HTML source document, rather than calling an external file to process data.
MySQL – It is RDBMS that runs as a server providing multi-user access to number of databases.
Duration of the course: 36 hours
More companies are shifting on Linux based servers for monetary (Linux is free) and security reasons. Linux based servers primarily are based on PHP. This creates an ample demand for PHP professionals. Just as an example one can find more and more Indian Govt. sites switching on to PHP (from ASP) as it is more secure. Web development companies prefer PHP as it’s free and comes bundled with a host of amazing features!
Search engine optimization (SEO) is the process of improving the visibility of a website or a web page in search engines via the "natural", "algorithmic", search results.More frequently a site appears in the search results list, the more visitors it will receive from the search engine's users.
Duration of the Course: 30 Hours
Scope of SEO:
SEO is the force behind a company’s online success. Internet marketing is now a billion dollar industry and everyone is slowly but surely accepting this.
Even top companies in India and the world are now keeping huge budgets for Internet marketing. The demand of website design, development and SEO is increasing day by day as the number of websites increases in India.
Oracle – Its is an ORDBMS, that is used to implement data relationships, text mining, schemas with well designed infrastructure and systems, protecting the data all ways.
Duration of the Course: 150 Hours
Any RDBMS has the tremendous scope anywhere in the world since no business can run without data so where there is data there will be database.
It is a good time to be a Database Administrator, both now and in the future. In a CNNarticle it is listed that Database Administrator (DBA) as one of the Top Ten Promising jobs with solid job growth outlook over the next several years.
MOBILE APPLICATION DEVELOPMENT
iOS and android Application development :
Mobile application development is the process by which application software is developed for small low-power handheld devices such as personal digital assistants, enterprise digital assistants or mobile phones.
Duration of course:90 hours
As of December 2011,324 million smartphones were sold through 3 quarters of 2011 and 6.8 million Android and iOS devices were activated.US smartphone users approaching 100 million.
And there is a huge demand for mobile applications especially in these two platforms. The scope of mobile application development is now not only restricted to one category or one trend. It covers vast range of booming sectors like business, Games, News, Weather, Education, and Money or the finance sector.
With the increasing competition and the demand in mobile application development field, companies are rushing forward to offer complete end-to-end solutions. Thus, mobile application development has become a mandatory tool for the organization focusing on a mounted rise in upward direction.
Software testing is an investigation conducted to provide stakeholders with information about the quality of the product or service under test.Software testing can also provide an objective, independent view of the software to allow the business to appreciate and understand the risks of software implementation.
Duration of course: 75 hours
Testing has become showstopper for several application/product implementations andbusiness has realized the importance of structured testing of applications before release.
There is dearth of skills in test automation areas – scripting skills in the tools languages like VB, Java and other scripting languages like Perl, Shell, Python .
Always there is demand for good performance testers who can analyze the performance test results, identify the bottlenecks and suggest tuning techniques. | <urn:uuid:c5ddca73-eead-4d32-abf2-3b8f609253a9> | 2.796875 | 1,098 | Content Listing | Software Dev. | 27.249278 |
A carat is a unit of weight for diamonds and other gemstones. One carat equals 200 milligrams (0.200 grams). There are 453 grams in a pound (1,000 grams to a kilogram). Therefore, if your fiancee weighs 170 pounds, you have a 385,050-carat fiancee!
A karat, when used with gold, is a unit of purity-- 24-karat gold is pure gold, but usually you mix gold with a metal like copper or silver to make jewelry (because pure gold is too soft). Each karat indicates 1/24th of the whole. So if a piece of jewelry is made of metal that is 18 parts gold and 6 parts copper, that is 18-karat gold.
Where did such a funny unit of purity come from? It turns out that a German gold coin called a mark was common about a thousand years ago. It weighed 24 carats (4.8 grams). The purity of the gold in the coin was expressed in the number of carats of gold present in this 24-carat coin.
Here are some interesting links: | <urn:uuid:2092ce51-9b77-40fc-b26f-3267c3b85316> | 3.125 | 233 | Knowledge Article | Science & Tech. | 79.041154 |
Freezing is the process when a liquid turns into a solid. Freezing occurs when heat is lost from an object, which causes the molecules to slow down and form tighter bonds. basically in short terms freezing is when, lets say, water turns into ice. Freezing is the opposite of melting, and two steps away from evaporation. Freezing occurs at below 0 degrees Celsius. | <urn:uuid:41d08e82-545a-420c-9330-33788746e20c> | 3.4375 | 78 | Knowledge Article | Science & Tech. | 63.788857 |
and Marsden counted the deflections of alpha particles
off gold foil at different angles. Use the simulation
below to see their results!
diagrams show the overhead and side views of their apparatus.
Use the blue rotate buttons to rotate the microscope
to different angles, and the graph will count how many
particles are seen at this angle. The scale on the graph
can be changed using the slide bar.
more time looking at each angle to improve the accuracy
on the graph. Geiger and Marsden spent weeks counting
many thousands of particles. | <urn:uuid:17e1efb4-933a-402f-a8f5-8cc302d7f76c> | 3.296875 | 117 | Tutorial | Science & Tech. | 53.721087 |
The first and foremost advantage of
any logging API over plain System.out.println
resides in its ability to disable
certain log statements while allowing
others to print unhindered. This capability
assumes that the logging space, that
is, the space of all possible logging
statements, is categorized according
to some developer-chosen criteria.
This observation had previously led
to choose category as the central
concept of the package. However, since
log4j version 1.2, Logger class has
replaced the Category class. For those
familiar with earlier versions of
log4j, the Logger class can be considered
as a mere alias to the Category class.
Loggers are named entities. Logger
names are case-sensitive and they
follow the hierarchical naming rule.
A logger is said to be an ancestor of another logger if its name followed
by a dot is a prefix of the descendant logger name. A logger is said to be
a parent of a child logger if there are no ancestors between
itself and the descendant logger.
For example, the logger named "com.parent"
is a parent of the logger named "com.parent.child".
Similarly, "ancestor" is
a parent of "ancestor.parent"
and an ancestor of " ancestor.parent.child".
The root logger resides at the top
of the logger hierarchy. It is exceptional
in two ways:
1. it always exists,
2. it cannot be retrieved by name.
Invoking the class static Logger.getRootLogger
method retrieves it. All other loggers
are instantiated and retrieved with
the class static Logger.getLogger
method. This method takes the name
of the desired logger as a parameter.
Some of the basic methods in the Logger
class are listed below.
The logger is the core component of
the logging process. In log4j, there
are 5 normal levels Levels of logger
available (not including custom Levels),
the following is borrowed from the
log4j API (http://jakarta.apache.org/log4j/docs/api/index.html):
Level DEBUG - The DEBUG Level
designates fine-grained informational
events that are most useful to debug
static Level INFO - The INFO level designates informational
messages that highlight the progress
of the application at coarse-grained
static Level WARN - The WARN level designates potentially
static Level ERROR -
The ERROR level designates error events
that might still allow the application
to continue running.
static Level FATAL - The FATAL level designates very
severe error events that will presumably
lead the application to abort.
In addition, there are two special
levels of logging available: (descriptions
borrowed from the log4j API http://jakarta.apache.org/log4j/docs/api/index.html):
static Level ALL -The ALL Level has the lowest possible
rank and is intended to turn on all
static Level OFF - The OFF Level has the highest possible
rank and is intended to turn off logging.
There are a number of ways to create
a logger, one can retrieve the root
Logger logger = Logger.getRootLogger();
One can create a new logger:
logger = Logger.getLogger("MyLogger");
More usually, one instantiates a static
logger globally, based on the name
of the class:
static Logger logger = Logger.getLogger(test.class);
All these create a logger called "logger",
one can set the level with:
You can use any of 7 levels; Level.DEBUG,
Level.INFO, Level.WARN, Level.ERROR,
Level.FATAL, Level.ALL and Level.OFF. | <urn:uuid:9631f9d7-56f9-416f-acc6-b8e046b97505> | 2.828125 | 830 | Documentation | Software Dev. | 46.611391 |
A spherical balloon is made from a material whose mass is 3.86 kg. The thickness of the material is negligible compared to the 2.16-m radius of the balloon. The balloon is filled with helium (He) at a temperature of 286 K and just floats in air, neither rising nor falling. The density of the surrounding air is 1.19 kg/m3. Find the absolute pressure of the helium gas. | <urn:uuid:1d1c8d5b-6076-42ce-9ca4-64f778c5c1ad> | 3.84375 | 86 | Q&A Forum | Science & Tech. | 83.725 |
The Wind in the Willows
When the atmospheric pressure varies between the horizontal points, the wind blows. As the English poet Christina Rossetti once wrote, "Who has seen the wind, neither I nor you." But that hasn't stopped us from measuring it. A wind vane is almost as old as the beginning of time. A simple pennant or flag will point in the direction from which the wind is coming. On airport runways, a cone-shaped bag opened at each end extends horizontally and points in the direction of the wind. This simple wind vane is called a windsock. Pilots can tell the wind direction as they land.
A pressure plate anemometer is the oldest type of anemometer. It measures wind speed by a single swinging metal plate rather than the cups of a modern anemometer.
An anemometer measures wind speed, while a weather vane or wind vane measures wind direction.
By the way and very importantly, the wind direction is never the direction the wind is going, but rather, the direction from which the wind is coming. A northeast wind is coming from the northeast. A south, or southerly, wind blows from the south.
What about wind speed? Again, back in the seventeenth century, English physicist Robert Hooke came up with a device consisting of a plate that moved proportionally to the wind speed. The plate swung out farther in a stronger wind. That became known as a pressure plate anemometer.
In more recent times, rotating cups mounted on a shaft have been used for measuring wind speeds (see the figure at the end). This cup anemometer records the wind speed as the cups spin. Those rotating cups might turn some gears or generate an electrical current. The greater current indicates higher wind speeds.
Some anemometers, called aerovanes, look like airplane propellers. The device swings into the wind, and then the propeller blades rotate with the increasing wind speed.
Something that easily beats an old rusty anemometer is the traditional Beaufort scale, which relates wind speeds to the motion of objects such as trees or water. Anemometers become inaccurate because of their constant exposure.
Excerpted from The Complete Idiot's Guide to Weather © 2002 by Mel Goldstein, Ph.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc. | <urn:uuid:f6d1459f-82dd-468d-8545-ece5f8e41449> | 3.625 | 505 | Knowledge Article | Science & Tech. | 54.994226 |
A format specifier starts with the character ‘%’ and ends with
a format-control letter—it tells the
how to output one item. The format-control letter specifies what kind
of value to print. The rest of the format specifier is made up of
optional modifiers that control how to print the value, such as
the field width. Here is a list of the format-control letters:
NOTE: The POSIX standard says the first character of a string is printed. In locales with multibyte characters, gawk attempts to convert the leading bytes of the string into a valid wide character and then to print the multibyte encoding of that character. Similarly, when printing a numeric value, gawk allows the value to be within the numeric range of values that can be held in a wide character.
Other awk versions generally restrict themselves to printing the first byte of a string or to numeric values within the range of a single byte (0–255).
printf "%4.3e\n", 1950
prints ‘1.950e+03’, with a total of four significant figures, three of
which follow the decimal point.
(The ‘4.3’ represents two modifiers,
discussed in the next subsection.)
‘%E’ uses ‘E’ instead of ‘e’ in the output.
printf "%4.3f", 1950
prints ‘1950.000’, with a total of four significant figures, three of which follow the decimal point. (The ‘4.3’ represents two modifiers, discussed in the next subsection.)
On systems supporting IEEE 754 floating point format, values
infinity are formatted as
‘-inf’ or ‘-infinity’,
and positive infinity as
‘inf’ and ‘infinity’.
The special “not a number” value formats as ‘-nan’ or ‘nan’.
The ‘%F’ format is a POSIX extension to ISO C; not all systems
support it. On those that don't, gawk uses ‘%f’ instead.
NOTE: When using the integer format-control letters for values that are outside the range of the widest C integer type, gawk switches to the ‘%g’ format specifier. If --lint is provided on the command line (see Options), gawk warns about this. Other versions of awk may print invalid values or do something else entirely. (d.c.) | <urn:uuid:502df51f-7d14-4613-bfc9-fbd7792bd8b8> | 3.5625 | 548 | Documentation | Software Dev. | 65.500703 |
It is native to the coastline of western North America, where it is a common kelp of the intertidal zone. It is dark brown in color, shiny and bumpy in texture, and may reach over five meters long. It grows a branching stipe from a thick holdfast. It bears long, flat, straplike fronds lined with small blades each a few centimeters long.
If you think this observation is inaccurate, please add an ID, participate in the quality assessment above, or describe the inaccuracy in a comment. | <urn:uuid:48d13928-b59b-4d1b-bd3a-8d0f4df5fd46> | 2.75 | 110 | Knowledge Article | Science & Tech. | 48.704907 |
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NASA page all about radio waves and radio astronomy
NASA page about electromagnetic waves with descriptions of such waves and their uses.Covers radio waves, microwaves, infrared, visible light, ultraviolet (UV), x-rays and gamma rays.
Even today it seems like magic. You turn on your radio and, somehow, sound sent from a distant radio station fills the room. How does radio transmission work?
This a biography of radio astronomer Susan Jocelyn Bell Burnell, who discovered the first pulsar (stars that release regular bursts of radio waves) in 1967.
See the universe in range of wavelengths from gamma rays to radio waves.
Satellite radio is poised to change the way we listen to music. Find out how digital radio gets from Earth to satellite to you!. From HowStuffWorks.com.
A discussion on the possible health implications of using mobile telephones.
A site from the ThinkQuest competition about light giving brief descriptions of electromagnetic radiation from radio waves and microwaves to x rays and gamma rays.
A range of resources on the electromagnetic spectrum and the different types of electromagnectic wave, from radio waves to gamma rays.
This site shows how a radio is tuned using a variable capacitor connected to a simple antenna transformer circuit. Includes a description of reactance equalization.
Showing 1 - 10 of 146 | <urn:uuid:f5cf460b-50d1-442d-9813-c04b0699a324> | 3.171875 | 371 | Content Listing | Science & Tech. | 49.659072 |
Scientists predict rare ’hibernation’ of sunspots?
2011 06 15
By Kerry Sheridan | YahooNews.com
For years, scientists have been predicting the Sun would by around 2012 move into solar maximum, a period of intense flares and sunspot activity, but lately a curious calm has suggested quite the opposite.
According to three studies released in the United States on Tuesday, experts believe the familiar sunspot cycle may be shutting down and heading toward a pattern of inactivity unseen since the 17th century.
The signs include a missing jet stream, fading spots, and slower activity near the poles, said experts from the National Solar Observatory and Air Force Research Laboratory.
"This is highly unusual and unexpected," said Frank Hill, associate director of the NSO’s Solar Synoptic Network, as the findings of the three studies were presented at the annual meeting of the American Astronomical Society’s Solar Physics Division in Las Cruces, New Mexico.
"But the fact that three completely different views of the Sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation."
Solar activity tends to rise and fall every 11 years or so. The solar maximum and solar minimum each mark about half the interval of the magnetic pole reversal on the Sun, which happens every 22 years.
Hill said the current cycle, number 24, "may be the last normal one for some time and the next one, cycle 25, may not happen for some time.
"This is important because the solar cycle causes space weather which affects modern technology and may contribute to climate change," he told reporters.
What a quiet sun looks like: Very few active regions are visible in this 2009 satellite picture.
Image courtesy STEREO/NASA
Experts are now probing whether this period of inactivity could be a second Maunder Minimum, which was a 70-year period when hardly any sunspots were observed between 1645-1715, a period known as the "Little Ice Age."
"If we are right, this could be the last solar maximum we’ll see for a few decades. That would affect everything from space exploration to Earth’s climate," said Hill.
Solar flares and eruptions can send highly charged particles hurtling toward Earth and interfere with satellite communications, GPS systems and even airline controls.
Geomagnetic forces have been known to occasionally garble the world’s modern gadgetry, and warnings were issued as recently as last week when a moderate solar flare sent a coronal mass ejection in the Earth’s direction.
The temperature change associated with any reduction in sunspot activity would likely be minimal and may not be enough to offset the impact of greenhouse gases on global warming, according to scientists who have published recent papers on the topic.
"Recent solar 11-year cycles are associated empirically with changes in global surface temperature of 0.1 Celsius," said Judith Lean, a solar physicist with the US Naval Research Laboratory.
If the cycle were to stop or slow down, the small fluctuation in temperature would do the same, eliminating the slightly cooler effect of a solar minimum compared to the warmer solar maximum. The phenomenon was witnessed during the descending phase of the last solar cycle.
This "cancelled part of the greenhouse gas warming of the period 2000-2008, causing the net global surface temperature to remain approximately flat -- and leading to the big debate of why the Earth hadn’t (been) warming in the past decade," Lean, who was not involved in the three studies presented, said in an email to AFP.
A study in the March 2010 issue of Geophysical Research Letters explored what effect an extended solar minimum might have, and found no more than a 0.3 Celsius dip by 2100 compared to normal solar fluctuations.
"A new Maunder-type solar activity minimum cannot offset the global warming caused by human greenhouse gas emissions," wrote authors Georg Feulner and Stefan Rahmstorf, noting that forecasts by the Intergovernmental Panel on Climate Change have found a range of 3.7 Celsius to 4.5 Celsius rise by this century’s end compared to the latter half of the 20th century.
"Moreover, any offset of global warming due to a grand minimum of solar activity would be merely a temporary effect, since the distinct solar minima during the last millennium typically lasted for only several decades or a century at most."
Article from: news.yahoo.com
Ed Note: They’ve spent the last few years telling us that the sun was starting to heat up and become MORE active. Now they suggest the opposite.
And notice how they’re starting to relate the sun’s activity to climate change - years ago that would have been heresy, and not in line with the anthropogenic global warming message.
Not everyone’s got the memo, however:
The National Solar Observatory (NSO) says that, based on 13 years of observations, sunspots are weakening. There have been fewer during the present cycle - and, if the trend continues, there may be none at all in the next.
Meanwhile, NSO observations of the jet streams circling the sun, whose strength tends to correlate with solar activity, has shown that activity is near-non-existent. Were the next solar cycle to proceed as usual, they would have appeared two or three years ago.
Finally, the sun’s corona, or upper atmosphere, is also failing to show changes associated with the usual solar cycles. Normally, scientists would expect to see magnetic features in the corona moving north and south in a phenomenon known as the rush to the poles. This time, however, they’re moving at a crawl.
"This is highly unusual and unexpected," Frank Hill, associate director of the National Solar Observatory’s Solar Synoptic Network, told Space.com.
"But the fact that three completely different views of the sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation."
The Maunder Minimum coincided with what’s known as the Little Ice Age, a period of unusual cold. But the scientists say there doesn’t appear to be a link between solar activity and the earth’s climate, with the Little Ice Age having been triggered by volcanic eruptions.
It’s hard not to get the feeling that they really are just guessing...
- Massive Solar Flare Storm Warnings for the Next Few Years
- Global warming theory in chaos after report finds increased solar activity may COOL the Earth
- Solar Scientists Agree That the Sun’s Recent Behavior Is Odd, but the Explanation Remains Elusive
Also tune into RedIceRadio:
David Warner Mathisen - The Hydroplate Theory, Cataclysmic Global Flood & Precession of the Equinoxes
Walter Cruttenden - Ancient Cosmology: A Map of the Future
John Major Jenkins - The Myths and Fallacies of 2012
Robert Felix - The Coming Ice Age
Robert Felix - Magnetic Reversal and Evolutionary Leaps
Tim Ball - Climategate & The Anthropogenic Global Warming Fraud
Andrew Johnson - Chemtrails, Weather Modification & Climate Change
Peter Taylor - The Corporatization of the Environmental Movement
James Follett - The Church of Global Warming
Sun Headed Into Hibernation, Solar Studies Predict
Latest News from our Front Page
No Bank Deposits Will Be Spared from Confiscation
2013 05 18
As alert Zero Hedge readers are aware, this week the EURO Politburo is busy debating the dodgy subject of deposit "bail-ins."
The following article very succinctly explains this odious mode of fractal fractional reserve end-game chicanery.
The author encourages all of you to share it with others.
NO BANK DEPOSITS WILL BE SPARED FROM CONFISCATION
By Matthias Chang Esq, futurefastforward.com (with author’s permission)
I challenge ...
Military Says No Presidential Authorization Needed To Quell “Civil Disturbances”
2013 05 17
A recent Department of Defense instruction alters the US code applying to the military’s involvement in domestic law enforcement by allowing US troops to quell “civil disturbances” domestically without any Presidential authorization, greasing the skids for a de facto military coup in America along with the wholesale abolition of Posse Comitatus.
The instruction (embedded at the end of this article), which ...
Ancient Maya Pyramid Destroyed in Belize
2013 05 17
An archaeological group says it plans to take legal action.
Despite its small size, the Caribbean country of Belize is known for a few outstanding characteristics: a spectacular barrier reef, a teeming rain forest, and extensive Maya ruins.
It now has one fewer of those ruins.
A construction company in Belize has been scooping stone out of the major pyramid at the site ...
Ginger: A Warming Herb
2013 05 17
Ginger is an Asian herb that is particularly well known to us in the West. Over time, and with trial and error, its stimulating properties and piquant flavor have been integrated into both our herbal “materia medica” and cuisine.
Brewed as an herbal tea, ginger root is particularly helpful for those people who have underactive stomachs and difficulty producing adequate amounts ...
Australian man dead for 40 minutes revived with new CPR machine
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In an Australian first, doctors have used a new resuscitation technique to revive three patients who were clinically dead for up to an hour.
One of the lucky survivors was Colin Fiedler, 49, who was pronounced dead at The Alfred Hospital in Melbourne, Victoria, after suffering a heart attack, The Herald Sun reported.
Doctors brought Fieldler back to life using a U.S.-made ...
|More News » | | <urn:uuid:5cbf0a9f-5e58-4fa6-b5d6-2b6a4459ecbc> | 3 | 2,061 | Content Listing | Science & Tech. | 40.138515 |
NASA's Spitzer Space Telescope has at last found buckyballs in space, as illustrated by this artist's conception showing the carbon balls coming out from the type of object where they were discovered -- a dying star and the material it sheds, known as a planetary nebula.
Buckyballs are made up of 60 carbon atoms organized into spherical structures that resemble soccer balls. They also look like Buckminister Fuller's architectural domes, hence their official name of buckministerfullerenes. The molecules were first concocted in a lab nearly 25 years ago, and were theorized at that time to be floating around carbon-rich stars in space.
But it wasn't until now that Spitzer, using its sensitive infrared vision, was able to find convincing signs of buckyballs. The telescope found the molecules -- as well as their elongated, rugby-ball-like relatives, called C70 -- in the material around a dying star, or planetary nebula, called Tc 1. The star at the center of Tc 1 was once similar to our sun but as it aged, it sloughed off its outer layers, leaving only a dense white-dwarf star. Astronomers believe buckyballs were created in shed layers of carbon that blew off the star.
Tc 1 does not show up that well in images, so a picture of the NGC 2440 nebula, taken by NASA's Hubble Space Telescope, was used in this artist's conception. Hubble planetary nebula credit: NASA, ESA and K. Noll (STScI) | <urn:uuid:86cd9a72-0807-4f5b-ac3f-bbfa65da4756> | 3.484375 | 322 | Knowledge Article | Science & Tech. | 43.955685 |
Atmospheric Chemistry of Earth's Troposphere
When you think of chemistry, do you think about mixing colored liquids in test tubes and maybe making an explosion... or at least a nice puff of smoke? Did you know that a lot of chemistry happens in Earth's atmosphere? There are many different kinds of chemicals in the air. Those chemicals often combine with each other in chemical reactions, making new and different chemicals. This is called "atmospheric chemistry".
Most of the gas in our atmosphere is nitrogen. About 4/5ths of the air is nitrogen. What about the other 1/5th? Almost all of it is oxygen, the stuff in the air we need to breathe. There are also very small amounts of a bunch of other chemicals.
Have you heard of greenhouse gases? They are kinds of gases that trap the heat from sunlight in our atmosphere. Earth would be very cold if we didn't have any greenhouse gases. Carbon dioxide and methane are two very important greenhouse gases.
Some of the chemicals in the air come from pollution. When we burn coal in a factory or gasoline in our cars, we make air pollution. Coal and oil have sulfur in them. When they burn, they make chemicals called sulfur oxides. These can turn into sulfuric acid when they mix with water droplets in the air. These droplets of acid can fall to the ground as acid rain. Cars and trucks also give off chemicals called nitrogen oxides. Nitrogen oxides combine with other chemicals to make smog. They also help make nitric acid, which is another acid in acid rain.
Nature also does things to change the chemistry of the troposphere. Volcanoes, lightning, and wildfires all add chemicals to the air or change the ones that are already there. Energy from sunlight can make chemical reactions happen, changing one gas into another. Some chemicals move in cycles between the atmosphere, living creatures, and the oceans. The Carbon Cycle and the Nitrogen Cycles are two important cycles that change the chemistry of the atmosphere.
This table (below) describes some of the chemicals in the troposphere, and some of the chemical reactions that happen in the air:
|Chemical||Formula||Role in Tropospheric Chemistry|
Carbon dioxide is a kind of greenhouse gas. When we breathe, we take in oxygen and breathe out carbon dioxide. Plants and some kinds of microbes use carbon dioxide during photosynthesis to make food. Burning fuels also puts carbon dioxide into the atmosphere.
|Methane is a kind of greenhouse gas.|
|Most of the gas in Earth's atmosphere is nitrogen. About 4/5ths of the air is nitrogen. The nitrogen cycle explains how nitrogen moves around in the environment. When fuel burns hot, like it does in the engine of a car, nitrogen combines with oxygen to make nitrogen oxides.|
NO & NO2
|Nitrogen oxides are a kind of pollution. Burning fuels like gasoline in air makes nitrogen oxides. Most nitrogen oxides come from cars and trucks. They help to make smog. They also mix with water droplets in the air to make nitric acid. Nitric acid is a part of acid rain.|
|Oxygen & Ozone||
O2 & O3
|PAN (Peroxyacytyl nitrate)||
|Smog is a mixture of smoke and fog. Photochemical smog is a kind of air pollution. It has nitrogen oxides, ozone, VOCs, and PAN in it.|
SO2 & SO3
|Sulfur dioxide and sulfur trioxide are types of pollution. People make them when we burn coal and oil. Volcanoes also give off sulfur oxides. Sulfur dioxide mixes with water droplets in the air to make sulfuric acid. Sulfuric acid is in acid rain.|
Sulfuric acid is in acid rain. Sulfuric acid in the air is made when sulfur dioxide gas mixes with water droplets. The sulfur dioxide gas comes from volcanoes and from coal and oil that people burn for fuel. | <urn:uuid:a800bdcf-e1db-440c-be70-52d8fc4c7a92> | 3.59375 | 844 | Knowledge Article | Science & Tech. | 54.262259 |
Fluids and gases can move in strange and mysterious ways that aren’t always apparent to our unaided eyes. It's only with the use of tracers or dyes, photographic techniques and a bit of luck, that we can capture fluid dynamics in action.
Here are some of the weird and beautiful ways in which fluids flow.
Supersonic Shock Wave
When an object moves faster than the speed of sound, funny things start to happen. The bullet in the image above is moving so fast, the air in front of it can’t get out of the way quickly enough. So it starts to pile up in front of the bullet, forming an area of compressed air — a shock wave.
The same thing happens with supersonic jets. As they fly faster than the speed of sound, they build up a shock wave in front of them. The sonic boom that accompanies these aircraft is actually the wave of compressed air hurtling by your ears.
Image: Andrew Davidhazy/Rochester Institute of Technology | <urn:uuid:dadbd057-e7d6-46cb-881a-5f112fbe5869> | 3.375 | 213 | Truncated | Science & Tech. | 61.886842 |
A team of researchers from the U.S. Army Research Laboratory in
Adelphi, Md., and the University of Maryland in Baltimore, captured
reflected photons from a highly specialized laser beam to create a VGI
image of a remote target.
In the case of VGI, reflection does not refer to a mirror image of an
object. Rather it is merely the individual reflected photons of light
that are counted with a single-pixel camera known as a light bucket.
"Virtual ghost imaging is an amazing tool," says Ronald Meyers, a
quantum physicist with the U.S. Army Research Laboratory, in a paper
published in the American Institute of Physics' journal Applied Physics
Letters. "Because we are no longer bound by the need to collect spatial
information – as is necessary in a typical camera – we can
produce an image in some rather adverse and highly obscured conditions."
In normal ghost imaging, harnessing information to make an image is a
two-step process. First, you analyze the light source, which could be
the sun or a lamp, with a charge-coupled device (CCD) camera. You then
use a second detector, a light bucket, to count the reflected photons.
By combining the data from the light source with the properties of the
collected photons, an image can be created.
The trick to making an image from photons that contain no spatial
information lies in physics related to "entanglement," a property of
light that Einstein referred to as "spooky action at a distance."
Through entanglement, photons (individual packets of light) can share a
certain degree of information. This property is already being developed
for specialized communications and computers.
Virtual ghost imaging is a more self-contained and robust application
of this phenomenon. For example, in VGI, one light source was a laser
that produced an incredibly coherent beam of light known as a Bessel
beam. Bessel beams, unlike normal laser beams, produce
concentric-circle patterns. If a portion of the beam is blocked or
obscured along its trajectory, the original pattern eventually reforms.
"Bessel beams are self-healing and provide an important tool in virtual
ghost imaging," said Meyers. "Even after passing through distortions or
a mask, the same well-defined ring shapes reemerge." So long as enough
photons make it to the target and back to the single-photon detector,
it's possible to construct an image.
In their proof-of-concept demonstration, the researchers compared a
Bessel beam's VGI imaging capabilities with that of a normal "Gaussian"
laser beam. Their target was the letters "ARL." The light was then
reflected back to the single pixel bucket detector. The researchers
conducted this same test several times, placing different objects or an
obscuring medium in the paths of the two light beams. In each case
– whether passing through an offset aperture, cloudy water, or
heat distortion – the Bessel beam reformed to produce a
recognizable VGI image. The Gaussian beam produced a much less faithful
image, and, in the case of the offset aperture, produced virtually no
image at all.
"What this demonstrates is that by combining virtual ghost imaging with
a highly diffraction-free coherent light source like a Bessel beam,
it's possible to probe through conditions that would normally thwart
other imaging technologies," Meyers says.
According to the researchers, potential spin-offs of ghost imaging and
virtual ghost imaging include applications in
Intelligence-Surveillance-Reconnaissance (ISR), medical imaging, and
Article: "Virtual Ghost Imaging through Turbulence and Obscurants using
Bessel Beam Illumination" is published in Applied Physics Letters.
Authors: Ronald E. Meyers (1), Keith S. Deacon (1), Arnold D. Tunick (1), and Yanhua Shih (2). | <urn:uuid:14bff35f-9ef9-4145-a325-c077e9e51a26> | 3.859375 | 840 | Knowledge Article | Science & Tech. | 41.320084 |
The monarch's inbuilt solar compass
Some designs defy our imagination and will probably be fully understood and certainly not improved upon. The monarch butterfly's navigation system is awe inspiring. Quite an example of "doing more with less". (GW)
How migrating butterflies use body clocks to find their way
By Steve Connor
January 8, 2008
The spectacular migration of the monarch butterfly, which covers a 2,000-mile round trip in a year, uses an inbuilt precision clock that enables the insect to use the sun as a compass, a study has found.
An internal biological clock that times the 24-hour cycle of night and day allows the monarch butterfly to calculate its direction of flight when migrating either north or south, depending on the time of the year, scientists have discovered.
Monarch butterflies are famous for the journey they make each spring from their winter roosting sites in the mountain pine trees of Mexico to as far as the US-Canadian border and back again in autumn – an unparalleled migratory feat for such as small creature. As the monarchs fly north in spring they breed several times during their summer journey. Four or five generations later, their offspring make the long journey home again, often landing in the same Mexican valley and even on the same tree that their great, great grandparents left the previous winter.
Scientists have known for years that the monarchs use the sun as a compass to guide them on their journey, and as a calendar for telling them when to begin the return journey to Mexico. But a compass based on the sun's moving position in the sky would not work unless the insects also have an accurate clock to tell them the time of day.
No one had been able to locate this internal timepiece, until now. A study by Steven Reppert, professor of neurobiology at the University of Massachusetts Medical School, has identified the key gene in the monarch butterfly that acts as a biological clock for estimating the 24-hour cycle of the circadian rhythm.
Professor Reppert said that the gene was responsible for a light-sensitive protein called cryptochrome (CRY) which counts the passing hours of each day, and also communicates the information to the monarch's inbuilt solar compass for the insect to calculate its correct direction of flight.
It is the second CRY gene to be found in insects. The first, CRY1, was discovered in drosophila fruit flies but the monarch's gene is sufficiently different to warrant a distinctive name, CRY2, Professor Reppert said. "This is a very interesting realignment of how one thinks about insect-clock models. There was no reason to suspect the butterfly clock would be different," he said.
"What we have in the butterfly is an astounding clock mechanism, one that is more similar to our own circadian clock and less similar to the clock of a fly," he said. "We have still to understand how the tiny brain of the monarch butterfly, which is no bigger than the head of a ballpoint pen, can arrange information about time and space that leads it to carry out the appropriate flight behaviour," Professor Reppert told the online journal Public Library of Science. | <urn:uuid:eaa26860-8158-42a2-89f2-145c0054ed36> | 3.609375 | 644 | Truncated | Science & Tech. | 41.260643 |
As I know all cells require oxygen. So my question is how efficiently can plants operate in no-oxygen atmosphere? Do all plants produce enough oxygen for themselves? Can they consume their own oxygen or the oxygen will be quickly lost to the air? Is there a plant that consumes more oxygen than they produce?
During the daylight, the plant is photosynthesising faster than it is respiring so there is no net uptake of oxygen (the oxygen of course being produced in the as part of the photosynthesis).
Of course, this only applies for tissues where photosynthesis is occurring. In the roots of the plant, oxygen must always be present in the surrounding soil/growth medium for respiration. Therefore if there is no oxygen in the roots then the root cells will be unable to produce ATP from respiration and consequently die. This will eventually lead to the death of the entire plant as it is unable to take up nutrients due to the lack of a functioning root network.
This is the cause of plant death when soil is waterlogged - the water fills spaces in the soil that would otherwise contain air (i.e. oxygen).
Certain plants (often crop plants), rice being given as an example in the comments below, are able to survive being waterlogged and the resulting low oxygen supply. However they can only do so in the short term. Rice plants in particular have adaptations that allow the transport of oxygen from the aerial parts of the plant down to the roots. This does of course mean that the rice can not survive being totally submerged for an extended period of time. Plants such as rice may have better adapted anaerobic fermentation pathways that become the main producer of ATP when aerobic respiration has arrested thus allowing them to better cope when transiently submerged than other plants. | <urn:uuid:20430785-47e6-430f-83ba-3e5a7c922ed4> | 3.09375 | 361 | Q&A Forum | Science & Tech. | 49.476834 |
Chirality and Optical Activity
|Chiral Stereoisomers||The Difference Between Enantiomers on the Macroscopic Scale|
|The Difference Between Enantiomers on the Molecular Scale|
The cis/trans or E/Z isomers formed by alkenes aren't the only example of stereoisomers. To understand the second example of stereoisomers, it might be useful to start by considering a pair of hands. For all practical purposes, they contain the same "substituents" four fingers and one thumb on each hand. If you clap them together, you will find even more similarities between the two hands. The thumbs are attached at about the same point on the hand; significantly below the point where the fingers start. The second fingers on both hands are usually the longest, then the third fingers, then the first fingers, and finally the "little" fingers.
In spite of their many similarities, there is a fundamental difference between a pair of hands that can be observed by trying to place your right hand into a left-hand glove. Your hands have two important properties: (1) each hand is the mirror image of the other, and (2) these mirror images are not superimposable. The mirror image of the left hand looks like the right hand, and vice versa, as shown in the figure below.
Objects that possess a similar handedness are said to be chiral (literally, "handed"). Those that do not are said to be achiral. Gloves are chiral. (It is difficult, if not impossible, to place a right-hand glove on your left hand or a left-hand glove on your right hand.) Mittens, however, are often achiral. (Either mitten can fit on either hand.) Feet and shoes are both chiral, but socks are not.
In 1874 Jacobus van't Hoff and Joseph Le Bel recognized that a compound that contains a single tetrahedral carbon atom with four different substituents could exist in two forms that were mirror images of each other. Consider the CHFClBr molecule, for example, which contains four different substituents on a tetrahedral carbon atom. The figure below shows one possible arrangement of these substituents and the mirror image of this structure. By convention, solid lines are used to represent bonds that lie in the plane of the paper. Wedges are used for bonds that come out of the plane of the paper toward the viewer; dashed lines describe bonds that go behind the paper.
If we rotate the molecule on the right by 180 around the CH bond we get the structure shown on the right in the figure below.
These structures are different because they cannot be superimposed on each other, as shown in the figure below.
CHFClBr is therefore a chiral molecule that exists in the form of a pair of stereoisomers that are mirror images of each other. As a rule, any tetrahedral atom that carries four different substituents is a stereocenter, or a stereogenic atom. However, the only criterion for chirality is the nonsuperimposable nature of the object. A test for achirality is the presence of a mirror plane within the molecule. If a molecule has a plane within it that will cut it into two symmetrical halves, then it is achiral. Therefore, lack of such a plane indicates a molecule is chiral. Compounds that contain a single stereo-center are always chiral. Some compounds that contain two or more stereocenters are achiral because of the symmetry of the relationship between the stereocenters.
The prefix "en-" often means "to make, or cause to be," as in "endanger." It is also used to strengthen a term, to make it even more forceful, as in "enliven." Thus, it isn't surprising that a pair of stereoisomers that are mirror images of each are called enantiomers. They are literally compounds that contain parts that are forced to be across from each other. Stereoisomers that aren't mirror images of each other are called diastereomers. The prefix "dia-" is often used to indicate "opposite directions," or "across," as in diagonal.
The cis/trans isomers of 2-butene, for example, are stereoisomers, but they are not mirror images of each other. As a result, they are diastereomers.
|Practice Problem 10:
Which of the following compounds would form enantiomers because the molecule is chiral?
The Difference Between Enantiomers on the Macroscopic Scale
If you could analyze the light that travels toward you from a lamp, you would find the electric and magnetic components of this radiation oscillating in all of the planes parallel to the path of the light. However, if you analyzed light that has passed through a polarizer, such as a Nicol prism or the lens of polarized sunglasses, you would find that these oscillations were now confined to a single plane.
In 1813 Jean Baptiste Biot noticed that plane-polarized light was rotated either to the right or the left when it passed through single crystals of quartz or aqueous solutions of tartaric acid or sugar. Because they interact with light, substances that can rotate plane-polarized light are said to be optically active. Those that rotate the plane clockwise (to the right) are said to be dextrorotatory (from the Latin dexter, "right"). Those that rotate the plane counterclockwise (to the left) are called levorotatory (from the Latin laevus, "left"). In 1848 Louis Pasteur noted that sodium ammonium tartrate forms two different kinds of crystals that are mirror images of each other, much as the right hand is a mirror image of the left hand. By separating one type of crystal from the other with a pair of tweezers he was able to prepare two samples of this compound. One was dextrorotatory when dissolved in aqueous solution, the other was levorotatory. Since the optical activity remained after the compound had been dissolved in water, it could not be the result of macroscopic properties of the crystals. Pasteur therefore concluded that there must be some asymmetry in the structure of this compound that allowed it to exist in two forms.
Once techniques were developed to determine the three-dimensional structure of a molecule, the source of the optical activity of a substance was recognized: Compounds that are optically active contain molecules that are chiral. Chirality is a property of a molecule that results from its structure. Optical activity is a macroscopic property of a collection of these molecules that arises from the way they interact with light. Compounds, such as CHFClBr, that contain a single stereocenter are the simplest to understand. One enantiomer of these chiral compounds is dextrorotatory; the other is levorotatory. To decide whether a compound should be optically active, we look for evidence that the molecules are chiral.
The instrument with which optically active compounds are studied is a polarimeter, shown in the figure below.
Imagine a horizontal line that passes through the zero of a coordinate system. By convention, negative numbers are placed on the left and positive numbers on the right of zero. Thus, it isn't surprising that levorotatory compounds are indicated with a negative sign (-).and dextrorotatory compounds are with a positive sign (+).
The magnitude of the angle through which an enantiomer rotates plane-polarized light depends on four quantities: (1) the wavelength of the light, (2) the length of the cell through which the light passes, (3) the concentration of the optically active compound in the solution through which the light passes, and (4) the specific rotation of the compound, which reflects the relative ability of the compound to rotate plane-polarized light. The specific rotation of the dextrorotatory isomer of glucose is written as follows:
When the spectrum of sunlight was first analyzed by Joseph von Fraunhofer in 1814, he observed a limited number of dark bands in this spectrum, which he labeled A-H. We now know that the D band in this spectrum is the result of the absorption by sodium atoms of light that has a wavelength of 589.6 nm. The "D" in the symbol for specific rotation indicates that it is light of this wavelength that was studied. The "20" indicates that the experiment was done at 20C. The "+" sign indicates that the compound is dextrorotatory; it rotates light clockwise. Finally, the magnitude of this measurement indicates that when a solution of this compound with a concentration of 1.00 g/mL was studied in a 10-cm cell, it rotated the light by 3.12.
The magnitude of the rotations observed for a pair of enantiomers is always the same.
The only difference between these compounds is the direction in which they rotate plane-polarized light. The specific rotation of the levorotatory isomer of this compound would therefore be -3.12.
The Difference Between Enantiomers on the Molecular Scale
A strategy, which is based on the Latin terms for left (sinister) and right (rectus), has been developed for distinguishing between a pair of enantiomers.
In this example, the path curves to the left, so this enantiomer is the (S)-2-bromobutane stereoisomer.
It is important to recognize that the (R)/(S) system is based on the structure of an individual molecule and the (+)/(-) system is based on the macroscopic behavior of a large collection of molecules. The most complete description of an enantiomer combines aspects of both systems. The enantiomer analyzed in this section is best described as (S)-(-)-2-bromobutane. It is the (S) enantiomer because of its structure and the (-) enantiomer because samples of the enantiomer with this structure are levorotatory; they rotate plane-polarized light clockwise. Note that the sign of the optical rotation is not correlated to the absolute configuration.
Return to Organic Topic Review Page
Organic Chemistry: Structure and Nomenclature of Hydrocarbons
Structure and Nomenclature of Hydrocarbons | Isomers | The Reactions of Alkanes, Alkenes, and Alkynes | Hydrocarbons | Petroleum and Coal | Chirality and Optical Activity
Periodic Table | Periodic Table | Glossary | Cool Applets
Gen Chem Topic Review | General Chemistry Help Homepage | Search: The general chemistry web site. | <urn:uuid:a7cc3062-b819-40f7-a110-45dc3a474799> | 3.640625 | 2,242 | Academic Writing | Science & Tech. | 37.660774 |
Potassium Atomic Number: 19
Potassium Symbol: K
Potassium Atomic Weight: 39.0983
Discovery: Sir Humphrey Davy 1807 (England)
Electron Configuration: [Ar]4s1
Potassium Word Origin: English potash pot ashes; Latin kalium, Arabic qali: alkali
Isotopes: There are 17 isotopes of potassium. Natural potassium is composed of three isotopes, including potassium-40 (0.0118%), a radioactive isotope with a half life of 1.28 x 109 years.
Potassium Properties: Potassium's melting point is 63.25°C, boiling point is 760°C, specific gravity is 0.862 (20°C), with a valence of 1. Potassium is one of the most reactive and electropositive of metals. The only metal that is lighter than potassium is lithium. The silvery white metal is soft (easily cut with a knife). The metal must be stored in a mineral oil, such as kerosene, as it oxidizes rapidly in air and catches fire spontaneously when exposed to water. Its decomposition in water evolves hydrogen. Potassium and its salts will color flames violet.
Uses: Potash is in high demand as a fertilizer. Potassium, found in most soils, is an element that is essential for plant growth. An alloy of potassium and sodium is used as a heat transfer medium. Potassium salts have many commercial uses.
Sources: Potassium is the 7th most abundant element on earth, making up 2.4% of the earth's crust, by weight. Potassium is not found free in nature. Potassium was the first metal isolated by electrolysis (Davy, 1807, from caustic potash KOH). Thermal methods (reduction of potassium compounds with C, Si, Na, CaC2) are also used to produce potassium. Sylvite, langbeinite, carnallite, and polyhalite form extensive deposits in ancient lake and sea beds, from which potassium salts can be obtained. In addition to other locations, potash is mined in Germany, Utah, California, and New Mexico.
Element Classification: Alkali Metal
Density (g/cc): 0.856
Appearance: soft, waxy, silvery-white metal
Atomic Radius (pm): 235
Atomic Volume (cc/mol): 45.3
Covalent Radius (pm): 203
Ionic Radius: 133 (+1e)
Specific Heat (@20°C J/g mol): 0.753
Fusion Heat (kJ/mol): 102.5
Evaporation Heat (kJ/mol): 2.33
Debye Temperature (°K): 100.00
Pauling Negativity Number: 0.82
First Ionizing Energy (kJ/mol): 418.5
Oxidation States: 1
Lattice Structure: Body-Centered Cubic
Lattice Constant (Å): 5.230
CAS Registry Number: 7440-09-7
References: Los Alamos National Laboratory (2001), Crescent Chemical Company (2001), Lange's Handbook of Chemistry (1952) | <urn:uuid:395c28a9-4ff5-470d-bc2e-f66f6f65564f> | 3.53125 | 669 | Knowledge Article | Science & Tech. | 55.935882 |
Butt, Kevin R., Lowe, Christopher N., BEASLEY, Toby, HANSON, Ian and KEYNES, Randal
Darwin's earthworms revisited.
European Journal of Soil Biology, 44
Official URL: http://dx.doi.org/10.1016/j.ejsobi.2008.03.004
Down House was Charles Darwin's home from 1842 until his death in 1882 and where he wrote “The Formation of Vegetable Mould through the Action of Worms”. The work described here is based upon passages from this book and from further observations on earthworms in this area. General observations were made in addition to systematic sampling in areas selected either from signs of earthworm activity, habitat type or in direct relation to Darwin's documented work.
Greatest species richness (n = 9) was found in Middle Field. Greatest earthworm density was present in Darwin's Kitchen Garden (715 m−2) with the largest associated biomass (261 g m−2). Aporrectodea longa was the most abundant species. Lumbricus terrestris, described by Darwin in terms of its behaviour, but not directly named, was located in relatively low numbers, but its diagnostic middens and associated burrows were easily detected. Earthworms associated with Darwin's cinder and chalk application experiments were also examined. In total, 19 of Britain's 28 earthworm species were located within the nominated World Heritage Site.
Repository Staff Only: item control page | <urn:uuid:cd17b2e6-912f-47d5-a42e-cd782822093f> | 2.765625 | 314 | Academic Writing | Science & Tech. | 53.930495 |
The location of this disaster, Carhuaz, is very close to where one of the most tragic disasters occurred in modern world history. In 1970, a massive earthquake triggered a landslide that killed an estimated 25,000 people who lived in the city of Yungay.
Posts Tagged ‘climate change’
Posted in Environment, Peruvian News, tagged Carhuaz, climate change, earthquakes, electricity, glaciers, global warming, melting glaciers, Pedro Suarez-Vertiz, Peru, tsunamis, video, water, Yungay on April 13, 2010 | Leave a Comment »
Posted in Energy, Environment, Peruvian News, tagged alternative energy, biomass, clean energy, climate change, glaciers, global warming, hydroelectric power, micro hydro, Peru, renewable energy, solar, solar energy, solar power, wind, wind energy, wind power on February 17, 2010 | Leave a Comment »
Last week Peru’s government approved wind, solar, micro hydro, and biomass energy projects that will add 500 megawatts of clean, renewable energy, meeting 12% of the current electricity needs of the country.
This is a crucial boost for a country that currently produces 80% of its electricity via hydroelectric power– an uncertain resource of energy going forward. Peru’s Andean glaciers provide most of the water for hydroelectric dams and they are expected to melt by 2022 as a result of global warming and climate change. However, Peru’s El Comercio suggests that in addition to the more well-known alternative energy projects the government has approved, up to 500 megawatts of energy will also be produced by up to 17 small micro hydro projects that might not be dependent on the glaciers. Some of these facilities are already operational but did not have government contracts prior to this time.
Posted in Environment, Music, Peruvian Culture, Peruvian News, tagged Amazon Rainforest, Amazonas, Andes Mountains, climate change, Cuando Piensas en Volver, glaciers, global warming, hydroelectric power, lyrics, Music, music videos, musicians, Pedro Suarez-Vertiz, songs, water on January 13, 2010 | Leave a Comment »
One of Peru’s most popular musicians has released an optimistic climate change anthem as the title track of his newest album Amazonas.
While Pedro Suarez-Vertiz has produced numerous hits, he is also well known for writing socially conscious songs. For these reasons, he is a beloved musician and celebrity in Peru. He has also gained an international audience because of songs like “Cuando Piensas en Volver” (When You Think of Returning), an anthem for expatriates who miss their countries.
Click here to read more and watch the video on The Huffington Post.
Posted in Environment, Peruvian News, tagged Andes Mountains, Barbara Drake, climate change, glaciers, Huaraz, hydroelectric power, Jorge Vera, NBC News, Pastoruri Glacier, Peru, water on December 16, 2009 | Leave a Comment »
NBC News ran a fantastic 3.5 minute segment last week about Peru’s emerging water crisis.
As the country’s Andean glaciers melt, this will mean less water and electricity for everyone. We lived in Huaraz last year near the ice formerly known as the Pastoruri Glacier (shown in the video). It’s a serious issue that’s getting too little attention in my opinion.
I would like to give kudos to my friend Barbara Drake and her husband Jorge Vera for being part of the team that helped NBC to find locations for their shoot and for helping arrange logistics.
Posted in Environment, Peruvian News, tagged bicycles, Christmas, Christmas Tree, climate change, LED, LED lights, Lima, Peru, San Borja, solar, solar energy, solar power, wind, wind energy, wind power, zero emissions on December 16, 2009 | Leave a Comment »
On Friday I wrote about how the Lima district of San Borja planned to light an eco-friendly Christmas Tree using LED lights, wind power, solar power, and bicycles. As promised, here are several photos of the beautiful tree.
Posted in Environment, Peruvian News, tagged Alto Purús National Park, Amazon Rainforest, biodiversity loss, Brazil, climate change, deforestation, Environment, global warming, national park, park ranger, Peru, sustainable development, tropical rainforest on November 25, 2009 | Leave a Comment »
This article was originally published on ecopolitology.org– a website covering the politics of energy and the environment.
While it’s not news to most of us who work in or follow international conservation, Peru’s El Comercio newspaper ran a story today about how only 8 park rangers patrol Alto Purús National Park. Alto Purús is the largest national park in Peru and the third largest in all of South America.
Alto Purús “protects” 2,724,263 hectares of tropical rainforest (~ 6.7 million acres). The math’s not too challenging on this one. That’s almost a million acres for each of the 8 rangers to patrol. | <urn:uuid:39a4feb8-d117-4b1d-ba8b-78b715f8d686> | 2.890625 | 1,068 | Personal Blog | Science & Tech. | 30.266945 |
Geoengineering: Whiter skies?
Article first published online: 1 JUN 2012
Copyright 2012 by the American Geophysical Union
Geophysical Research Letters
Volume 39, Issue 11, June 2012
How to Cite
2012), Geoengineering: Whiter skies?, Geophys. Res. Lett., 39, L11801, doi:10.1029/2012GL051652., , and (
- Issue published online: 1 JUN 2012
- Article first published online: 1 JUN 2012
- Manuscript Accepted: 2 MAY 2012
- Manuscript Revised: 1 MAY 2012
- Manuscript Received: 9 MAR 2012
One proposed side effect of geoengineering with stratospheric sulfate aerosols is sky whitening during the day and afterglows near sunset, as is seen after large volcanic eruptions. Sulfate aerosols in the stratosphere would increase diffuse light received at the surface, but with a non-uniform spectral distribution. We use a radiative transfer model to calculate spectral irradiance for idealized size distributions of sulfate aerosols. A 2% reduction in total irradiance, approximately enough to offset anthropogenic warming for a doubling of CO2 concentrations, brightens the sky (increase in diffuse light) by 3 to 5 times, depending on the aerosol size distribution. The relative increase is less when optically thin cirrus clouds are included in our simulations. Particles with small radii have little influence on the shape of the spectra. Particles of radius ∼0.5 μm preferentially increase diffuse irradiance in red wavelengths, whereas large particles (∼0.9 μm) preferentially increase diffuse irradiance in blue wavelengths. Spectra show little change in dominant wavelength, indicating little change in sky hue, but all particle size distributions produce an increase in white light relative to clear sky conditions. Diffuse sky spectra in our simulations of geoengineering with stratospheric aerosols are similar to those of average conditions in urban areas today. | <urn:uuid:c7636b91-a619-4711-b7e4-eea552d49dba> | 3.0625 | 415 | Academic Writing | Science & Tech. | 31.573841 |
Classes defined by the macros defclass! or defclass* have a set of methods for instance creation, visualisation and edition. For example if you define a class by:
(defclass! rgb-color () ((red-comp :initform 0 :initarg :red-comp :accessor red-comp) (green-comp :initform 0 :initarg :green-comp :accessor green-comp) (blue-comp :initform 0 :initarg :blue-comp :accessor blue-comp)) (:documentation "color with components red, blue and green.") (:icon 179))
A factory and an editor are associated to the class by default.
To change the "miniview" appearance you need only to subclass the mehod
(defmethod draw-obj-in-rect ((self rgb-color) x x1 y y1 edparams view))
The view parameter determine the view where the object is shown, x, x1, y, y1 specify a rectangle into the view. Some instances need some values for edition (i.e. font size, etc), you can use the edparams parameter for this porpose.
For our example the next method definition:
(defmethod draw-obj-in-rect ((self rgb-color) x x1 y y1 edparams view) (declare (ignore edparams view)) (om-with-fg-color self (om-make-color (red-comp self) (green-comp self) (blue-comp self)) (om-fill-rect x y x1 y1)))
shows the rgb-color instance as a color (!!!)
You can define a subclass of omboxeditcall, for example :</P>
(defclass colorfactory (omboxeditcall) ())
To associate the new box class with the rgb-color class using the next method:
(defmethod get-type-of-ed-box ((self rgb-color)) colorfactory)
..and redefine methods of omboxeditcall.
Double-click on a factory call the
OpenEditorFrame method with the factory as argument. If there is not an editor for the class the default editor is open. In order to write an editor we start to define the method
(defmethod Class-has-editor-p ((self rgb-color)) t)
The next method associate the editor's class name with the class edited:
(defmethod get-editor-class ((self rgb-color)) 'colorEditor)
Finally we define the editor class which is a subclass of EditorView:
(defclass colorEditor (EditorView) ())
You can not put rgb-color instances in a maquette because they are not temporal objects, if you want the instances of your class to be temporal objects your class must inherit from the simple-container or the container classes:
(defclass! rgb-color (simple-container) ((red-comp :initform 0 :initarg :red-comp :accessor red-comp) (green-comp :initform 0 :initarg :green-comp :accessor green-comp) (blue-comp :initform 0 :initarg :blue-comp :accessor blue-comp)) (:documentation "color with componenents red, blue and green.") (:icon 179)) | <urn:uuid:626b43df-f60b-446b-a9bd-e5b027441124> | 3.03125 | 711 | Documentation | Software Dev. | 47.628158 |
Earth has been experiencing an incredible increase in the number of global earthquakes just since 1973.
- In 1973, there were more than 5,000 Global Quakes
- In 1983, there were more than 10,000 Global Quakes
- In 1993, there were more than 20,000 Global Quakes
- In 2003, there were more than 30,000 Global Quakes.
We are on target now for over 40,000 Global quakes by 2013.
The March 11, magnitude 9.0 earthquake in Japan may have shortened the length of each Earth day and shifted its axis. But do not worry! You will not notice the difference.
Using a United States Geological Survey estimate for how the fault responsible for the earthquake slipped, research scientist Richard Gross of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., applied a complex model to perform a preliminary theoretical calculation of how the Japan earthquake—the fifth largest since 1900—affected Earth’s rotation. His calculations indicate that by changing the distribution of Earth’s mass, the Japanese earthquake should have caused Earth to rotate a bit faster, shortening the length of the day by about 1.8 microseconds (a microsecond is one millionth of a second).
The calculations also show the Japan quake should have shifted the position of Earth’s figure axis (the axis about which Earth’s mass is balanced) by about 17 centimeters (6.5 inches), towards 133 degrees east longitude. Earth’s figure axis should not be confused with its north-south axis; they are offset by about 10 meters (about 33 feet). This shift in Earth’s figure axis will cause Earth to wobble a bit differently as it rotates, but it will not cause a shift of Earth’s axis in space—only external forces such as the gravitational attraction of the sun, moon and planets can do that.
Both calculations will likely change as data on the quake are further refined.
In comparison, following last year’s magnitude 8.8 earthquake in Chile, Gross estimated the Chile quake should have shortened the length of day by about 1.26 microseconds and shifted Earth’s figure axis by about 8 centimeters (3 inches). A similar calculation performed after the 2004 magnitude 9.1 Sumatran earthquake revealed it should have shortened the length of day by 6.8 microseconds and shifted Earth’s figure axis by about 7 centimeters, or 2.76 inches. How an individual earthquake affects Earth’s rotation depends on its size (magnitude), location and the details of how the fault slipped.
Gross said that, in theory, anything that redistributes Earth’s mass will change Earth’s rotation.
“Earth’s rotation changes all the time as a result of not only earthquakes, but also the much larger effects of changes in atmospheric winds and oceanic currents,” he said. “Over the course of a year, the length of the day increases and decreases by about a millisecond, or about 550 times larger than the change caused by the Japanese earthquake. The position of Earth’s figure axis also changes all the time, by about 1 meter (3.3 feet) over the course of a year, or about six times more than the change that should have been caused by the Japan quake.”
Gross said that while we can measure the effects of the atmosphere and ocean on Earth’s rotation, the effects of earthquakes, at least up until now, have been too small to measure. The computed change in the length of day caused by earthquakes is much smaller than the accuracy with which scientists can currently measure changes in the length of the day. However, since the position of the figure axis can be measured to an accuracy of about 5 centimeters (2 inches), the estimated 17-centimeter shift in the figure axis from the Japan quake may actually be large enough to observe if scientists can adequately remove the larger effects of the atmosphere and ocean from the Earth rotation measurements. He and other scientists will be investigating this as more data become available.
Gross said the changes in Earth’s rotation and figure axis caused by earthquakes should not have any impacts on our daily lives. “These changes in Earth’s rotation are perfectly natural and happen all the time,” he said. “People shouldn’t worry about them.”
Alan Buis 818-354-0474
Jet Propulsion Laboratory, Pasadena, Calif. | <urn:uuid:31cd3bc0-9d21-4b5b-8133-393cbd0ea9f0> | 4.0625 | 927 | Knowledge Article | Science & Tech. | 52.294409 |
How Do you know if it is a meteorite?
The purpose of this page in not to make you an expert at identifying meteorites. It is to help save time and money by eliminating things that are not meteorites. Probably 99% of the items that are presented by finders as meteorites turn out to be not to be meteorites. There are a number of features that can be used to help identify if you have a meteorite or not. Rather than start with meteorite features, since most rocks are not meteorites, lets start with things that will help eliminate rock as being possible meteorites.
Keep in mind that none of these features is 100% conclusive. So far no rock from earth has ever been identified as having been blasted into space and returned as a meteorite. But, that doesn't mean it couldn't happen. If any of the terrestrial features below are found with some of the meteorite features listed below it should be looked into further.
Terrestrial (earth) Features that indicate a rock is not a meteorite.
1. If there is quartz (a clear or milky white crystal) it is not a meteorite. As far as I know quartz has never been found in any meteorite.
2. If there is an easily visible crystal structure it might not be a meteorite. This is not conclusive because some of the rarer meteorites do have some crystal structure. However, most ordinary meteorites do not unless viewed under a microscope.
3. If the rock has many small holes in its interior it is probably not a meteorite. Small holes are almost never found in the interior of meteorites. The one or two that do have them are extremely rare.
4. If the rock feels light it is not a meteorite. Stony meteorites generally have a density around 3.5 grams per cm3 and normal earth crustal rock is around 2.7 grams per cm3. In other words stony meteorites are about 30% heavier for the same size rock. The opposite is not true however. A rock that is denser than normal does not have to be a meteorite. There are many examples of dense terrestrial rocks.
5. If the exterior has sharp pointed features (except on obviously broken surfaces) it is not a meteorite. As meteorites come through the atmosphere any sharp points are melted away. As a result meteorites have smooth surfaces, although they may have depressions, called regmaglypts, that look like thumbprints pushed into clay.
Pictures of some common meteor-wrongs
A brief description is below each picture. Each picture has been thumbnailed to make the page load faster. If you click on the pictures you will see the full image. The pictures with DF at the end were graciously provided by Dave Freeman.
ball. These are used in ore crushing operations to reduce the ore
to smaller sizes. They are generally round in shape and can come
in various sizes from 2 inches up to at least 6 inches in diameter.
|Rusted magnetite. Magnetite is one of the most common meteorwrongs. Notice the rough surface texture. DF|
| Eroded and
wind polished cretaceous hematite. The piece on the left looks
nice and smooth like you might expect from a meteorite. The piece
on the right has small surface pits. DF
|Iron ore from Atlantic City, Wyoming DF|
|Coal fired locomotive clinker. Notice the numerous small holes. DF|| Lucite Hills
oil shale with iron pyrite encrusted oolites. This is a slice that
shows circular inclusions that look like chondrules. DF
|Smelter ore, titanium 16%. Note that the surface is rough and not smooth. DF||Worm coprolite hematite
encrusted. The surface has some linear
"cliffs". These are from a layer of the rock chipping
away. Meteorites don't have layers and as a result don't have
these type features. DF
|This is not a meteorite. It is a rock with desert varnish. Notice how bumpy the rock is instead of being smooth like the others.|
Now that we have thrown away 90% of our rocks lets look at some meteorite features that will help identify a meteorite.
Features that indicate a rock is a meteorite.
1. Fusion crust is what forms as a meteor passes through the atmosphere. It is the melted exterior of the meteor. Because meteorites are composed of different materials not all fusion crusts look the same. Fresh fusion crusts are usually a matte (dull) black, but some fresh meteorites have crusts that look like shiny black plastic and others are a light yellow brown color. Once a meteorite is on the ground it starts weathering. This weathering causes an oxidation of the crust and it turns from black to brown in color. Depending upon the climate conditions where it falls this will take varying amounts of time.
Fusion crust is one of the more difficult things for a novice to get a good feeling for. It really requires looking at a number of different meteorites. Many people picture the crust as being like the skin on an orange, but it is much more like the skin on an apple. Fusion crust is very thin, usually less than 1mm thick. It is generally the thickness of a heavy piece of paper. Out west it is many times confused with desert varnish which is a dark coating on rocks exposed to the sun and elements for a long time. Below are pictures that show both.
2. Most meteorites contain large amounts of iron and as a result are attracted to a magnet. This is not definitive because some meteorites are not attracted to a magnet and many earth rocks are. However, it is another clue for separating the trash from the treasures.
3. If the interior of the meteorite is visible, there are a couple clues. If it is an ordinary chondrite it will have small flecks of metal. The flecks may not be visible on a broken weathered surface, but if you grind a fresh surface they will be visible except for extremely weathered chondrites. Native terrestrial iron is extremely rare and found in only three locations. If you find metal flecks it is a very good indication of a meteorite.
4. Chondrules may also be visible on broke surfaces. Sometimes they are whole and look like little round balls sticking out of the surface.
Fusion Crust Pictures.
A brief description is below each picture. Each picture has been thumbnailed to make the page load faster. If you click on the pictures you will see the full image.
|This picture shows a 100% crusted Nuevo Mercurio (H5) meteorite. This black crust is what an ordinary chondrite looks like just after a fall.||This picture shows a 100%
crusted Gao-Guenie (H5) meteorite. These pieces fell in 1969 and
were recovered only recently. Notice the crust has weathered to a
|This picture is of a 1/2 Jengcheng (H5) stone. Notice how thin the crust is. This is a typical thickness.||This is picture of a slice of
Sahara 97094. Notice the 2 parallel black lines which show the
thickness of the crust. These lines are about 1mm apart.
|Different types of meteorites
can have different crusts. This is a carbonaceous chondrite,
|This piece is from an aubrite called Cumberland Falls. Notice the very thin almost yellowish crust.|
|This is a howardite, Great Sand
Seas 010. The crust is a shiny, black that is almost plastic looking.
It also has flow lines where melted crust flowed in streams pushed by
the atmosphere during entry.
The next pictures are not fusion crust pictures, but show what the interior of a couple ordinary chondrites look like.
|This is a super slice of Sahara 98175 an LL3.5 Notice the abundant chondrules as well as several large light colored clasts.||This is a piece of the El
Hammami meteorite. Notice the numerous metal flecks. If you
look closely you can also see some small gray chondrules.
Now that you know all about meteorite ID here are a few more pictures for you to look at and try to identify. | <urn:uuid:522d0ff5-7b1d-4919-9196-b0ac23b4cd79> | 3.390625 | 1,761 | Knowledge Article | Science & Tech. | 57.733535 |
CH4 - Methane:
First draw the Lewis dot structure:
Electron geometry: tetrahedral. Hybridization: sp3
Then draw the 3D molecular structure using VSEPR rules:
The molecular geometry of methane - CH4 - is tetrahedral with symmetric charge distribution on the central atom.
Therefore this molecule is non-polar.
Methane on Wikipedia.
Back to Molecular Geometries & Polarity Tutorial: Molecular Geometry & Polarity Tutorial.
For homework help in math, chemistry, and physics: www.tutor-homework.com. | <urn:uuid:6b09946e-32e6-405f-94e2-98a1b8ca3690> | 2.96875 | 125 | Tutorial | Science & Tech. | 20.298016 |
4th Grade Lesson Plan
Students will compare and contrast a coral reef and a kelp forest ecosystem and identify the abiotic and biotic factors within each.
2.a. Students know plants are the primary source of matter and energy entering most food chains.
3.a. Students know ecosystems can be characterized by their living and nonliving components. b. Students know that in a particular environment some kinds of plants and animals survive well, some survive less well, and some cannot survive at all. | <urn:uuid:85f0f20b-4925-47d3-bd98-10153e25cf90> | 3.453125 | 103 | Tutorial | Science & Tech. | 54.775649 |
Found 0 - 10 results of 63 programs matching keyword "solar power"
Watch the beginning of Venus’s transit across the disk of the sun, one of the rarest astronomical events. Watch the conclusion of Venus’s 6.5-hour journey across the disk of the sun, one of the rarest astronomical events. Senior Exploratorium Scientist, Paul Doherty demonstrates how you can make your own sun viewer. You can safely view sunspots, eclipses and transits with this equipment that you may have laying around the house!
To learn more about the upcoming Transit of Venus visit: http://www.exploratorium.edu/venus/question3.html There are green sea turtles in San Diego Bay? Where did they come from? Do they really live over 100 years? Why is it important for scientists to keep track of these giant creatures, and how on earth do they do it? In this interview with ecologist Tomoharu Eguchi (NOAA Marine Fisheries Service) and ecology graduate student Sheila Madrak, we meet the sea turtles and explore these 'big' questions.
Ever wondered where that crust on your car battery comes from? Exploratorium staff member Chuck Mignacco explains galvanic corrosion and the basics of battery maintenance using a time-honored miracle solvent: Coke. Watch for a surprise guest at the end of the video. This After Dark event presented a collection of objects, organizations, and activities use various alternative energy sources, and also looked at sustainably raised food. Astronomer Dr. Isabel Hawkins's journey to the stars began with two chance moments of enchantment with celestial bodies in her native Argentina. Inspired by the mystery of the sky, she went on to study physics and astronomy in California and then to work for 20 years as a research astronomer at UC Berkeley. Now retired from research and devoted to inciting a love of the stars and sky in young people, Dr. Hawkins reflects on her own initial moments of inspiration, on sharing her love of stars with others, and on how astronomy can, and should, remind us of our connection to one another, under a canopy of mystery.
Dr. Laura Peticolas is a physicist at UC Berkeley's Space Physics Research group. She studies the Aurora to learn more about the Earth and the workings of our Solar System. She's currently working with NASA's Mars data to understand why the Martian aurora looks the way it does. In this podcast she discusses her research, her inspiration and how and why scientists sonify data. We tour the NOAA Atmospheric Research Observatory at the South Pole where scientists are monitoring carbon dioxide levels, CFCs, solar radiation, and the ozone hole. An Exploratorium and NASA Sun-Earth Connection Education Forum Event
Overnight eclipse viewing party at Exploratorium begins July 31, 2008 at
9pm. and continues through Friday, August 1 in the wee hours.
San Francisco's Exploratorium brings its fifth eclipse expedition team to
remote Xinjiang Province in Northwestern China, very close to the Mongolian
border, where the Exploratorium will webcast a total solar eclipse live to
the world. Spend the Night at the Exploratorium! See the eclipse in person
live at the Exploratorium. Pack your sleeping bag and camp out on the museum
floor for an overnight eclipse party...or come to the viewing party in Second Life and enjoy the live webcast, exhibits, and music. | <urn:uuid:96153c90-ffa2-40c0-9345-a9adc97b6f2a> | 2.96875 | 700 | Content Listing | Science & Tech. | 48.858107 |
Anatomy and Physiology
Discussion Topic: Chemistry of Life, Cells, and Tissues Select an organ and provide an example of how it uses the following: carbohydrates, lipids, proteins, and nucleic acids. Also, describe an area of interest related to one of the types of molecules, for example, cholestero...
A string under a tension of 43 N is used to whirl a rock in a horizontal circle of radius 3.3 m at a speed of 26.46 m/s. The string is pulled in, and the speed of the rock increases. When the string is 0.635 m long and the speed of the rock is 80.5 m/s, the string breaks. What...
Length of a rectangle is 13 cm less than 5 times it's width. Its area is 28 square cm. Find dimensions of rectangle
how do you find the orthocenter of a triangle with the vertices A(4,0) B(-2,4) C(0,6)? Please explain to me how you get x after doing point slope form for the two slopes.
give the conjugate base for HNO2
never mind...i understand
Hey Steve, Thanks....but how could it be -4?
what is the orthocenter of triangle with the vertices of X(-11,0), Y(-11,-8), Z(-1,-4)?
i think it is line 14
How do the ideas of positive psychology differ from the traditional model of illness?
For Further Reading | <urn:uuid:07deb77b-6700-4f25-8e04-89a4bb9f80b2> | 3.609375 | 317 | Comment Section | Science & Tech. | 88.945254 |
Unit 1: Many Planets, One Earth // Section 9: The Age of Mammals
The first mammals on Earth were rodent-sized animals that evolved in the shadow of dinosaurs during the Jurassic and Triassic periods. After the K-T boundary extinction eliminated dinosaurs as predators and competitors, mammals radiated widely. Most of the modern mammal orders, from bats to large types like primates and whales, appeared within about 10 million years after dinosaurs died out. Because mammals could maintain a relatively constant internal temperature in hot or cold environments, they were able to adapt to temperature changes more readily than cold-blooded animals like reptiles, amphibians, and fish. This characteristic helped them to populate a wide range of environments.
Another important ecological shift was the spread of angiosperms (flowering plants), which diversified and became the dominant form of land plants. Unlike earlier plants like ferns and conifers, angiosperms' seeds were enclosed within a structure (the flower) that protected developing embryos. Their flower petals and fruits, which grew from plants' fertilized ovaries, attracted animals, birds, and insects that helped plants spread by redistributing pollen and seeds. These advantages enabled angiosperms to spread into more diverse habitats than earlier types of plants.
Earth's climate continued to fluctuate during the Cenozoic, posing challenges for these new life forms. After an abrupt warming about 55 million years ago, the planet entered a pronounced cooling phase that continued up to the modern era. One major cause was the ongoing breakup of Gondwanaland, a supercontinent that contained most of the land masses in today's southern hemisphere, including Africa, South America, Australia, and India (Fig. 20).
Figure 20. Gondwanaland
See larger image
Source: © United States Geological Survey.
Once these fragments started to separate about 160 million years ago, ocean currents formed around Antarctica. Water trapped in these currents circulated around the pole and became colder and colder. As a result, Antarctica cooled and developed a permanent ice cover, which in turn cooled global atmospheric and ocean temperatures. Climates became dryer, with grasslands and arid habitat spreading into many regions that previously had been forested.
Continued cooling through the Oligocene and Miocene eras, from about 35 million to 5 million years ago, culminated in our planet's most recent ice age: a series of glacial advances and retreats during the Pleistocene era, starting about 3.2 million years ago (Fig. 21). During the last glacial maximum, about 20,000 years ago, ice sheets covered most of Canada and extended into what is now New England and the upper Midwestern states.
Figure 21. Cenozoic cooling
See larger image
Source: © Global Warming Art. GNU License/www.globalwarmingart.com.
Human evolution occurred roughly in parallel with the modern ice age and was markedly influenced by geologic and climate factors. Early hominids (members of the biological family of the great apes) radiated from earlier apes in Africa between 5 and 8 million years ago. Humans' closest ancestor, Australopithecus, was shorter than modern man and is thought to have spent much of its time living in trees. The human genus, Homo, which evolved about 2.5 million years ago, had a larger brain, used hand tools, and ate a diet heavier in meat than Australopithecus. In sum, Homo was better adapted for life on the ground in a cooler, drier climate where forests were contracting and grasslands were expanding.
By 1.9 million years ago, Homo erectus had migrated from Africa to China and Eurasia, perhaps driven partly by climate shifts and resulting changes to local environments. Homo sapiens, the modern human species, is believed to have evolved in Africa about 200,000 years ago. Homo sapiens gradually migrated outward from Africa, following dry land migration routes that were exposed as sea levels fell during glacial expansions. By about 40,000 years ago Homo sapiens had settled Europe, and around 10,000 years ago man reached North America. Today, archaeologists, anthropologists, and geneticists are working to develop more precise maps and histories of the human migration out of Africa, using mitochondrial DNA (maternally inherited genetic material) to assess when various areas were settled.
Early in their history, humans found ways to manipulate and affect their environment. Mass extinctions of large mammals, such as mammoths and saber-toothed cats, occurred in North and South America, Europe, and Australia roughly when humans arrived in these areas. Some researchers believe that over-hunting, alone or in combination with climate change, may have been the cause. After humans depleted wildlife, they went on to domesticate animals, clear forests, and develop agriculture, with steadily expanding impacts on their surroundings that are addressed in units 5 through 12 of this text. | <urn:uuid:65261dde-5c95-4198-a01c-afa024b39ab7> | 4.25 | 1,009 | Academic Writing | Science & Tech. | 33.045986 |
peek-char &optional peek-type input-stream eof-error-p eof-value recursive-p => char
Arguments and Values:
peek-type---a character or t or nil.
input-stream---input stream designator. The default is standard input.
eof-error-p---a generalized boolean. The default is true.
eof-value---an object. The default is nil.
recursive-p---a generalized boolean. The default is false.
char---a character or the eof-value.
peek-char obtains the next character in input-stream without actually reading it, thus leaving the character to be read at a later time. It can also be used to skip over and discard intervening characters in the input-stream until a particular character is found.
If peek-type is not supplied or nil, peek-char returns the next character to be read from input-stream, without actually removing it from input-stream. The next time input is done from input-stream, the character will still be there. If peek-type is t, then peek-char skips over whitespace characters, but not comments, and then performs the peeking operation on the next character. The last character examined, the one that starts an object, is not removed from input-stream. If peek-type is a character, then peek-char skips over input characters until a character that is char= to that character is found; that character is left in input-stream.
If an end of file occurs and eof-error-p is false, eof-value is returned.
If recursive-p is true, this call is expected to be embedded in a higher-level call to read or a similar function used by the Lisp reader.
When input-stream is an echo stream, characters that are only peeked at are not echoed. In the case that peek-type is not nil, the characters that are passed by peek-char are treated as if by read-char, and so are echoed unless they have been marked otherwise by unread-char.
(with-input-from-string (input-stream " 1 2 3 4 5") (format t "~S ~S ~S" (peek-char t input-stream) (peek-char #\4 input-stream) (peek-char nil input-stream))) >> #\1 #\4 #\4 => NIL
*readtable*, *standard-input*, *terminal-io*.
If eof-error-p is true and an end of file occurs an error of type end-of-file is signaled.
If peek-type is a character, an end of file occurs, and eof-error-p is true, an error of type end-of-file is signaled.
If recursive-p is true and an end of file occurs, an error of type end-of-file is signaled.
See Also: None. | <urn:uuid:9c42b6b3-b017-4bb0-ad46-58afc251d109> | 3.390625 | 633 | Documentation | Software Dev. | 66.65025 |
MOON rocks were just the start. Now NASA wants to add cometary dust to its collection of celestial rubble. In February 2004 it will send a probe into orbit to capture a little bit of Comet P/Wild-2 and bring it back to Earth.
The probe, called Stardust, will fly within 100 kilometres of the comet. Three times during its mission - once as it approaches the comet, once in the thick of the dust, and again as it heads away - a collecting plate about a metre across will pop out from the back of the probe. A gel covering the collecting plate will trap dust expelled from the comet.
Scientists at the University of Washington in Seattle, who are in charge of Stardust, hope to trap about 10 000 dust particles larger than 15 micrometres across and a few as large as 0.25 millimetres across.
A capsule will carry ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:a27f56c3-8af2-4cf4-8aea-8d321151efc1> | 3.890625 | 209 | Truncated | Science & Tech. | 65.841741 |
Termites dominate the insect world in some tropical soils. In the rainforests of West Africa, there can be 10,000 individuals under each square metre. In some soils they can make up 98 per cent of all insect biomass!
Like earthworms in Britain, termites help to maintain the quality and stability of tropical soils. But what happens to the termites when rainforests are cleared for wood or agriculture?
David Jones and Paul Eggleton has been collecting and studying these insects in rainforests across the globe to try and find out.
Termites are busy workers. Their tunnelling and mound building activities, coupled with their amazing digestive systems, play a critical role in recycling nutrients from dead plants and releasing them back into the soil.
In Sumatra, a lot of the rainforest has been cleared for agriculture. Paul's Soil Team has been collecting soil samples from different deforested areas in order to identify and count the termite species left there.
Threat to agriculture
The researchers have found 34 species of termites in rainforests compared with only one in formerly forested areas that have been cleared for agriculture.
Since these insects are so important for breaking down plant material - and therefore providing nutrients that plants use to grow - a lack of them could have a detrimental effect on the soil quality and agriculture in these areas. In areas that depend on subsistence farming, this could have serious effects for the local population.
Paul's work will be important for understanding soil ecology in tropical environments. It might lead to ways of 'mending' infertile soil by re-introducing key termite species. | <urn:uuid:dfb45a0c-d944-4300-a6da-186f26d93e1b> | 3.796875 | 333 | Knowledge Article | Science & Tech. | 40.966005 |
The nuclear physics is the science which not seuleument studies the Atomic nucleus as such (development of an ideal model) but also the way in which it interacts when a particle arrives " with proximité" (the order of magnitude is 1E-12 cm, one usually speaks in nuclear physics about cross Section of which the unit is the Barn that is to say 1E-24 cm ²) core (obtaining experimental results). After a short historical background, this article is devoted to describe:
- the nuclear Structure , which aims at including/understanding how the Nucléon S (Proton S and Neutron S) interact to form the core.
- the mechanisms of the nuclear reactions of which the goal is to describe the various ways that have the cores to interact: fission, fusion, diffusion (elastic, inelastic), Radioactivity…
- the scopes of application of the nuclear physics : Medicine with the Astrophysical , while passing by the production of energy, all these spheres of activity exploits the physics of the interactions radiation-matters.
- the research organizations in nuclear physics, France and in the world.
The matter consists of Molécule S, themselves consisted of Atome S. These atoms are made of a central core surrounded by an electronic cloud. The nuclear physics is the science which is interested in the whole of the physical phenomena utilizing the atomic nucleus. Because of the microscopic size of this one, the mathematical tools used primarily lie within the scope of the formalism of the quantum Mécanique.
The Atomic nucleus consists of Nucléon S, which is divided into Proton S and in Neutron S. the protons are particles which have a electric Charge elementary positive, whereas the neutrons are neutral particles. They have only one magnetic moment, and are thus only not very sensitive to the electromagnetic Champ, contrary to the protons. If one compared the atomic nucleus to a hard sphere, the ray of this sphere would be of some Fermi S, 1 Fermi being worth 10-15 meters (1 Fermi = 1 femtometer). Cores having the same value of Z, i.e. the same number of protons, and not having the same number of neutrons are called Isotope S.
The core in the History
Until the turning of the 20th century, one believed that the Atome S were the ultimate components of the matter. The discovery of the Radioactivity in 1896 by Henri Becquerel and the studies which followed, in particular with the husbands Curie, started to suggest that the atoms were perhaps themselves of the made up objects. How, if not, the matter could it spontaneously emit particles as in the case of the radioactivity alpha?
It is into 1911 that Rutherford discovered that the Atomes seemed indeed to be made up objects. While analyzing the diffusion particles alpha emitted by a radioactive source through a gold sheet, it came from there to conclude that simplest seems to suppose that the atom contains a central load distributed in a very small volume (" it seems simplest to supposes that the atom contains has central charges distributed through has very small volume… " , Philosophical Magazine, Series 6, vol. 21, May 1911, p. 669-688). The model of Rutherford of the atom was thus a central core having an electric charge surrounded by electrons maintained in orbit by the electromagnetic interaction. He had already been proposed in 1904 by Nagaoka.
In 1919, Rutherford always discovers the existence in the core of the Proton, particle having an elementary positive load E , but having a mass much larger than that of the electron (which has a negative elementary electric charge to him). In 1932, Chadwick highlights the existence of the neutron, particle very similar to the proton, except the fact that it does not have an electric charge (from where its name). At the same period, Heisenberg proposes that the atomic nucleus is in fact made up of a unit of protons and neutrons.
The strong Interaction maintains the cohesion of the nucleons within the core. It is most intense of the four fundamental forces of nature (from where its name). It characterizes by fact that it is strongly gravitational at short distance (when the nucleons approach very close one the other), repulsive with " moyenne" outdistance, and cancels itself with long distance. The protons being charged particles, they also interact via the Coulomb interaction. If the number of protons in the core is important, the latter takes the step on the strong interaction and the cores become unstable. The quantity of energy which ensures the cohesion of the core is called energy binding of the core.
See also: nuclear Structure
Nuclear reactionsA reaction is known as nuclear power when there is modification of the quantum state of one or more cores. Take part then in the reaction protons and neutrons (noted respectively p and N ), but also of other particles, the such electrons e-, the positrons e+…
The nuclear reactions can be several types. To only quote most important:
- the fission: a heavy core breaks in several fragments. It is this type of reaction which is implemented in the atomic bombs of the type has, and, with a more peaceful aim, the nuclear plants.
- the fusion: several light cores amalgamate. It is the mode of production of energy of stars. Nuclear fusion is with the source of the Nucléosynthèse which makes it possible to explain the genesis of all the elements of the periodic Tableau of Mendeleïev and of their Isotopes. It is also the type of reaction which is used in the bombs called to hydrogen. The use of fusion at ends of civil energy production is not controlled yet. Its control is the object of the international project ITER.
- the Radioactivity: a core emits one or more particles spontaneously. One distinguishes the radioactivities , where a helium core is emitted; the radioactivity where either a electron and an electronic anti-neutrino are emitted (), or a Positron and a electronic Neutrino () and the radioactivity by which a core loses its energy by an electromagnetic radiation of high energy.
- reactions of knocked-out or spallation: light particles (Neutron S for example) are sent on a core targets and expel one or more Nucléon S of this core.
- reactions of diffusion (elastic or inelastic): light particles or cores, which constitute the projectile, are sent on a target core but in order to avoid a head-on collision. The projectile is deviated by the target but modified the state of the latter. In the case of a elastic Scattering, the energy of the target is not modified, contrary to a inelastic Scattering.
Applications of the nuclear physics
The Nucléosynthèse explains manufacture in the Universe of the various cores which currently constitute it. Two quite distinct processes are however necessary to explain the abundance of different the éléements chemical in the universe:
- In a first phase, at the time of the Big Bang, is formésà to leave the Hydrogène, the cores of 2 H (Deuterium), 3 He, 4 He and 7 Li. Aucn heavier element is not synthesized, because this phase is relatively short. However, to form elements heavier than lithium, it is necessary to have recourse to a reaction utilizing three helium cores, known as Réaction triples alpha. This type of reaction is extremely difficult to realize and can be done only over period much longer than the few minutes of the paramount nucleosynthesis.
- the continuation of the nucleosynthesis occurs thus in the middle of the star S. One then speaks about stellar Nucléosynthèse. This one scince besides in two processes: slow nucleosynthesis, taking place in the stars, which makes it possible to synthesize the elements lighter than the Fer, then explosive nucleosynthesis, only produced during the star explosions, called Supernova E. One speaks then about explosive nucleosynthesis.
See also: stellar Nucleosynthesis
See also: paramount Nucleosynthesis
See also: radioactive Dating
The Nuclear medicine rests on the use of radioactive sources and the interaction of these sources with human tissues. This interaction is exploited at ends of diagnosis (Radiologie for example) or of treatment (Radiothérapie). As from years 1980 developed the techniques of imagery by nuclear Magnetic resonance (IRM) which call upon the magnetic properties of the cores.
See also: Nuclear medicine
See also: Radiotherapy
The energy production can be:
- brêve and intense: it is the principle of a nuclear bomb,
- controlled (at ends of civil but so military production).
Controlled energy productionCurrently, the industrialists can exploit only the energy which comes from the fission of the heavy cores. Energy is then used:
- is to produce electricity, it is the case of the nuclear plants
See also: Nuclear plant
- is to make it possible to drive a vehicle, particularly in the maritime field (aircraft carrier, submarines with nuclear propulsion) and of the aerospace one
See also: thermal nuclear Propulsion
Military application (nuclear bomb)
See also: Bombe has
See also: Bomb H
Research organizations in Nuclear physics
- Commissariat à l'Energie Atomique (ECA)
- Large National Accelerator of Heavy Ions (GANIL, Caen)
- Laboratory of the linear accelerator (LAL, Orsay)
- Center of nuclear spectrometry and mass spectrometry (CSNSM, Orsay)
- Imagery and modeling in neurobiology and cancerology (IMNC, Orsay)
- SUN synchrotron (Saclay)
- European Synchrotron Radiation Facility (ESRF, Grenoble)
- Institute Laue Langevin (ILL, Grenoble)
- Laboratory Leon Brillouin (LLB, Orsay)
- National laboratory Henri Bequerel (Saclay)
- Center of nuclear studies (CENBG, Bordeaux Gradignan)
- Institute of nuclear physics (IPN, Orsay, Villeurbanne)
- Corpuscular Physics laboratory (LPC Caen, Clermont-Ferrand)
- multi-field Institute Hubert Curien (IPHC, Strasbourg)
- nuclear Physics laboratory and of high energies (LPNHE, Paris Jussieu)
In the world
- Oak Ridge National Labotory (ORNL)
- Los Alamos National Labotory (LANL)
- Nuclear fission
- nuclear Fusion
- Physique of the particles
- Quantum Mécanique
- Nuclear energy
- Bombe has
- Bombe H
- Bombe with neutrons
- atomic Bombardements of Hiroshima and Nagasaki
Service of Nuclear physics CEA/DAM, France
- National institute of Nuclear physics and Physics of the Particles (In2p3), France
- Large National Accelerator of Heavy Ions (GANIL), France
- Commissariat à l'Energie Atomique (ECA), France
- Gesellschaft für Schwerionenforschung (GSI), Germany
- Joint Institute for Nuclear Research (JINR), Russia
- National Laboratory, (ANL) the United States
- Center European of Nuclear Research, Swiss Argonne
- Riken, Japan
|Random links:||Ocelot | Vico | Kénan | Delmore Schwartz | Hiring| | <urn:uuid:f0aa8ea1-36c9-4aaf-9435-499292088125> | 3.5625 | 2,422 | Knowledge Article | Science & Tech. | 25.600051 |
Narrator: This is Science Today. Seismologists and computer scientists at the Lawrence Livermore National Laboratory used their supercomputers to recreate simulations of the devastating 1906 San Francisco earthquake to measure where the hardest hit areas were. Applied mathematician Anders Petersson describes how these sophisticated computer simulations provide insight into what the next big earthquake will look like.
Petersson: We can predict how badly the Earth will shake in different locations and see how that varies, depending on the soil type and such things. So, we can also predict the duration of the shaking. And what we want to look at in the future is coupling to structures to predict if bridges will fall down.
Narrator: Petersson says the computer simulations can also provide insight into another important, potential problem – the state's levee systems.
Petersson: And if they will stand because you get extended shaking out there in the sedimentary basins and that type of soil can liquefy and we hope to couple our simulations to programs to predict liquefaction as well.
Narrator: For Science Today, I'm Larissa Branin. | <urn:uuid:f6c566af-5ad6-4e35-a05e-db51ab42bb01> | 4.125 | 226 | Audio Transcript | Science & Tech. | 31.435 |
Brief review of bat research in the San Francisco Bay area and southern California providing land managers with information on the occurrence and status of bat species with links to bat inventories for California and related material.
Maps and text (Word or PDF format) and database (Excel or HTML format) for bedrock, forest floor, and mineral soil sampling in Voyageurs National Park, Minnesota to establish the background and baseline geochemistry and terrestrial mercury sources.
Bird banding is used to study the movement, survival and behavior of birds. The Bird Banding Laboratory Site has links to the value, procedure and history of bird banding, how to report bird bands (English & Spanish), and resources for birders.
Manual for research program on the nesting habits of sea turtles of the Virgin Islands, with descriptions of species, nesting behavior, observation methods, record keeping, tagging, and tissue sample collection. (PDF file, 121 pp.) | <urn:uuid:7d34488c-64ec-466b-bbd8-3d5babfd5c24> | 3.171875 | 189 | Content Listing | Science & Tech. | 33.748333 |
The Wang Eclipse
Year: 2012 Pages: 4
The Wang eclipse has two bumps in the gravitational curve that have not been explained and therefore are called anomalies. This eclipse happened on March 9 of 1997 and Qien Shen Wang recorded the gravitational acceleration on the surface of the earth during a full eclipse. The results of the measurements are reported in the paper titled ?Precise measurement of gravity variations during a total solar eclipse? . The interesting point of his result is that the visual eclipse is shown in relation to the gravitational eclipse. If the measurements are accurate, we can then determine the speed of gravity relative to the speed of light. Also the two large bumps imply that the mass of the corona is very high. With the proper equations the speed of gravity and the mass of the corona can be determined.
Your membership status does not allow you to participate in discussion or see all comments.
About the Wang eclipse1 year 22 days ago [2012-05-04 09:47:16]
Results from a precision gravimeter experiment in China 1997 demonstrate an assumed gravitational shielding present before and after the eclipse. No (or very small) effect is demonstrated during the eclipse. This is explained by Bob as caused by a very masive corona around the Sun. An alternative interpretation is presented here by means of a compensating effect due to gravitational shielding effecting central parts of our planet. Just before and just after the eclipse gravitational shielding effects exist in peripheral parts of our planet, but not in the gravimeter mass. A more detailed description of this idea will soon be present on my personal NPA page. Regards _____________ John-Erik | <urn:uuid:b3f740b3-45ef-468e-bdef-ba5074e19614> | 2.96875 | 333 | Comment Section | Science & Tech. | 41.803742 |
See more from this Session: Soil Genesis and Classification: I
A starting point for a USC should come from the most documented existing system. It should have the highest amount and most accurate data collected to support the science. The sharing of additional existing documentation will represent an excellent starting point for standards will support the development of a USC System. The new system is one that is fair and based on the best science of today and is agreed upon by a group of international experts and political leaders.
The system need to be cognizant and flexible to incorporate new developments. For example, numerical classification concepts that have been developed over the last 30 years could be investigated and if found fit for purpose, incorporated into the new system.
Soil Scientists from around the world have expressed the desire and need to develop a common USC System. The future USC should not be solely an academic exercise, but should be developed together with the major agencies supporting soil survey and mapping in the world. A global soil classification system that will be adopted by the major National soil survey and mapping agencies will ensure a continuity and consistency of information across political boundaries to assist with some of the more critical environmental issues facing the world today. | <urn:uuid:e5706860-2b47-483f-9325-11c6f4ab60da> | 3.296875 | 239 | Academic Writing | Science & Tech. | 28.184307 |
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2013 January 29
Explanation: What would it be like to drive on the Moon? You don't have to guess -- humans have actually done it. Pictured above, Apollo 16 astronauts John Young and Charles Duke recorded video during one such drive in 1972, with a digital version now available on the web. No matter which direction it headed, the Lunar Rover traveled a path literally covered with rocks and craters. The first half of the above video shows the rover zipping about a moonscape near 10 kilometers per hour, while the second half shows a dash-cam like view. The Lunar Rover was deployed on the later Apollo missions as a way for astronauts to reach and explore terrain further from the Lunar Module basecamp than was possible by walking in cumbersome spacesuits. Possible future lunar missions that might deploy robotic rovers capable of beaming back similar videos include those by China, Russia, India, and Google X-Prize contestants.
Authors & editors:
Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
A service of: ASD at NASA / GSFC
& Michigan Tech. U. | <urn:uuid:4d2a6ec4-e5e2-4b78-8e44-4fde89fba01a> | 3.75 | 261 | Knowledge Article | Science & Tech. | 42.195815 |
In his comment to How much Estimation is too much Estimation?, Anthony Watts suggested I create a scatter plot showing station distribution with latitude/longitude. It turned out not to be the ordeal I thought it might be, so I have posted some of the results in this thread. I started with 1885 and created a plot every 20 years, ending in 2005. I deliberately ended with 2005 because this is the final year in the GHCN record prior to the US station die-off of 2006.
Every dot on a plot represents a station, not a scribal record. Stations may be comprised of multiple records. A blue dot represents a station with an annual average that was fully calculated from existing monthly averages. A red dot represents a station that had missing monthly averages for that year, so the annual average had to be estimated. Stations that had insufficient data to estimate an annual average are not shown.
In the case where multiple scribal records exist for a station in the given year, I assigned a blue dot if all records were fully calculated from existing averages, a red dot if at least one record was estimated, and no dot if none of the records could produce an estimate. I believe this errs in the direction of assigning more blue dots than is deserved. Hansen’s bias method mathematically forces estimation to occur during the period of scribal record overlap.
The first plot shows coverage in 1885, five years into the GHCN record.
1905 shows improved coverage across the continental US, Japan and parts of Australia. A few stations have appeared in Africa.
1925 shows increased density in the western US, southern Canada, and the coast of Australia.
At the end of WWII, not a lot of change is noticeable other than improved coverage in Africa and South America as well as central China and Siberia.
In 1965 we see considerable increases inChina, parts of Europe, Turkey, Africa and South America.
A decline in quality seems to be apparent in 1985, as many more stations show as red, indicating their averages are estimated due to missing monthly data.
A huge drop in stations is visible in the 2005 plot, notably Australia, China, and Canada. 2005 was the warmest year in over a century. Not surprising, as the Earth hadn’t seen station coverage like that in over a century.
The final plot illustrates the world-wide station coverage used to tell us “2006 Was Earth’s Fifth Warmest Year“.
Update (Steve Mc): USHCN station information gets added into GHCN with a lag of almost a year (noted in comments below). Jerry Brennan, who’s followed this for some time, reports the following update schedule in the past:
USHCN station data for the year 2002 were published in the USHCN website by May 2003, and added to GHCN between November 8, and December 10, 2003.
USHCN station data for the year 2003 were added to GHCN between April 10, and May 6, 2004, and published in the USHCN website by January 2005.
USHCN station data for the years 2004, 2005, and the first three months of 2006, were added to GHCN between August 13, and September 11, 2006, and published in the USHCN website, with data through October 2006 by March 2007. The additional months of data were not added to GHCN.
USHCN station data through May 2007 were published in the USHCN website in October 2007, but the “new” data have not been added to GHCN as of this date.
By the end of February of each year, GHCN will usually have data for the full previous year from only 120 (non USHCN) stations in the 48 contiguous USA states.
I might add that there are two locations for USHCN data, one at NOAA and one at CDIAC. The NOAA version is more updated than the CDIAC version – perhaps there are other differences as well. I personally confirmed that the NOAA version (Oct 2007 edition) is updated to May 2007 for most USHCN stations. There was a USHCN update in May or June 2007 which updated to late 2006 for most USHCN stations.
I personally confirmed that the most recent GHCN version (ftp://ftp.ncdc.noaa.gov/pub/data/ghcn/v2 Feb 2008 edition), as noted by Jerry, contains USHCN updates only to March 2006 or so. Thus, GHCN is two USHCN updates behind at present (May 2007, Oct 2007) and its USHCN version is at least 14 months stale relative to what it could be using. | <urn:uuid:1fb9eeeb-5fd0-4570-895a-c1982ed39291> | 3 | 969 | Comment Section | Science & Tech. | 59.584655 |
Python source files can now be declared as being in different character set encodings. Encodings are declared by including a specially formatted comment in the first or second line of the source file. For example, a UTF-8 file can be declared with:
#!/usr/bin/env python # -*- coding: UTF-8 -*-
Without such an encoding declaration, the default encoding used is 7-bit ASCII. Executing or importing modules that contain string literals with 8-bit characters and have no encoding declaration will result in a DeprecationWarning being signalled by Python 2.3; in 2.4 this will be a syntax error.
The encoding declaration only affects Unicode string literals, which will be converted to Unicode using the specified encoding. Note that Python identifiers are still restricted to ASCII characters, so you can't have variable names that use characters outside of the usual alphanumerics.
See About this document... for information on suggesting changes. | <urn:uuid:fa6f76e5-4c37-47ec-a408-8455db423d05> | 2.921875 | 202 | Documentation | Software Dev. | 43.021255 |
Comparison of Electrostatic & Gravitational Force
Points of similarity :-
a) Both these are central forces. i.e, they act along the line joining the centres of two interacting bodies.
b) Both the forces obey the inverse square law of distance.
c) Both are conservative forces, i.e, the work done by them does not depend upon the path followed.
d) Both forces can operate even in vacum.
Points of dissimilarity :-
a) While the gravitational forces are always attractive in nature, the electrostatic forces may be attractive or repulsive.
b) While the gravitational force does not depend upon the medium, the electrostatic force definitely depends upon the medium.
c) Electrostatic forces are extremely large as compared to gravitational forces.
note : On a dry day, a dry comb when it has run through your hair can lift a small piece of paper upwards. In this way, it can overcome the force of gravity exerted by the whole of earth on paper. | <urn:uuid:39aafa2a-470d-4c3a-a5f9-423387d14880> | 3.40625 | 210 | Personal Blog | Science & Tech. | 40.334124 |
Gets or sets the start point of the line.
Assembly: PresentationCore (in PresentationCore.dll)
XMLNS for XAML: http://schemas.microsoft.com/winfx/2006/xaml/presentation, http://schemas.microsoft.com/netfx/2007/xaml/presentation
<object> <object.StartPoint> <Point .../> </object.StartPoint> </object>
Property ValueType: System.Windows.Point
The start point of the line. The default is (0,0).
Metadata properties set to true
The following example shows how to create and render a LineGeometry. A Path element is used to render the line. Since a line has no area, the Path object's Fill is not specified; instead the Stroke and StrokeThickness properties are used.
Other simple geometry classes include LineGeometry and EllipseGeometry. These geometries, as well as more complex ones, can also be created using a PathGeometry or StreamGeometry. For more information, see the Geometry Overview.
Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported) | <urn:uuid:b67d0bfa-3969-41f1-8382-f58c4a78384f> | 3.390625 | 285 | Documentation | Software Dev. | 52.679286 |
|Annu. Rev. Astron. Astrophys. 1984. 22:
Copyright © 1984 by . All rights reserved
2.4 Stellar Populations
The blue colors of Irrs are generally taken to mean that a proportionally larger component of the stellar population consists of early-type stars (247, 248). This is consistent with the fact that the high surface brightness Irrs are endowed with numerous HII regions and are actively forming stars. Bagnuolo (15) and Huchra (178), for example, have fit the colors of Irrs with a composite between old and young stellar populations, while continuous star formation models have been computed by Searle et al. (313), by Huchra (178) and by Code & Welch (59).
Specifies of the OB star populations have been explored through IUE spectra that are now available for a variety of high surface brightness Irr galaxy family members (27, 28, 29, 179, 180, 219, 377; see also 47, 196). Generally the 1150-2000 Å UV spectra of Irrs show features consistent with rich OB star clusters having near normal IMFs, but there are important exceptions. On the basis of UV spectra, a case was made for a very massive superstar (~ 2 x 103 M) in the core of the giant 30 Doradus HII complex in the LMC (52, 107, 305) and more recently for the somewhat similar NGC 604 giant HII region in the nearby spiral M33 (237). Even if we do not accept the presence of superstars in these systems (245a), it is clear that extraordinary concentrations of high-mass stars (~ 102 M) must be present to meet the ionization requirements and to fit the observed spectral characteristics. Giant HII regions are common in Irrs (169), and their possible relationship to very massive stars is now receiving careful scrutiny.
The low surface brightness dwarf Irrs present more of a problem with regard to stellar content, since they are also fairly blue but do not have the many obvious star-forming regions that characterize the high surface brightness systems. In general, the dwarfs seem to have stellar population mixes similar to those of the larger Irrs (81, 82, 160, 189), but the numbers of luminous stars are down in a manner qualitatively consistent with a lower total star formation rate (173, 185, 228, 295). Some dwarf systems have extremely blue colors and high surface brightnesses, perhaps indicating that bursts of star formation have recently been completed (158, 177, 178, 232, 313); detailed population studies of a few resolved galaxies support these viewpoints (57, 288).
The Irrs, therefore, are correctly noted for their young stellar population, but they also contain older stars. Only a few of the extreme ``intergalatic HII regions'' seem to be without a possible older stellar component (cf. 179, 312, 349, 377), but the nature of this older population and the number of previous generations of stars are not so clear. In the dwarf Irr VII Zw 403, for example, the metallicity of the gas is sufficiently low and the level of current star formation sufficiently vigorous that one is forced to doubt whether the galaxy could have formed stars in this vigorous way at an earlier stage (361). Nevertheless, the existence of a diffuse stellar component implies that an older population is in fact present. (Star formation histories are discussed in a later section.)
Many Irr galaxies are close enough that they can be resolved into individual stars. The LMC and SMC are, in fact, the best systems outside our own for studying stellar populations and support the concept of a nearly constant IMF in disk galaxies (see below). Beyond the MC, only intermediate- to high-mass stars can be individually observed at present, and aside from very luminous supergiants, only colors and magnitudes are available (187, and references therein). In more luminous Irr dwarfs, observed color-magnitude diagrams are similar in form, with pronounced blue and red supergiant branches well separated by a Hertzsprung gap (184, 185, 186, 202, 295, 296, 301). Massive stars evidently are present with relatively constant properties in Irrs, and thus the door is open to modeling the light from young stellar populations in terms of fairly standard components (as in 76, 180, 189, 191, 225).
Differences in OB stellar content between galaxies are largely explainable in terms of statistical effects, which can be quite severe in faint dwarfs, where OB star formation probably involves a series of time-disconnected discrete events (172, 288, 313). At the upper extremes of stellar mass, the situation is, as we have seen, less well defined; for example, the presence of many Wolf-Rayet stars in a small galaxy like Tololo 3 (216) might be due either to statistics or to special processes (e.g. very massive stars) in very large star formation events that are seen as giant and supergiant HII regions (169, 237). Finally, we point out that intermediate-mass stars become very luminous during the AGB evolutionary phase (see 193) and may be seen as resolvable stars in the diffuse light of Irrs (140), as long-period variables of interest to the extragalactic distance scale (387), and as major contributors to the infrared luminosity (272).
Star clusters provide further important clues to stellar populations in galaxies (e.g. 56), and currently they can be detected to distances of several Mpc in Irrs as a result of the open structures of the parent galaxies (155, 188). While numbers, sizes, and richnesses of star clusters vary from galaxy to galaxy (160, 167, 369), the clusters themselves are found to be remarkably similar in their integral optical stellar properties within such diverse Irr systems as the LMC (370a), M82 (257), and NGC 6822 (165, 372). The main variables affecting integral cluster observables are well known to be IMF, age, and chemical composition, although stellar richness can also be a significant factor (279). From color-magnitude diagrams of individual Magellanic Cloud star clusters it has been possible to calibrate approximately variations in global cluster parameters as a function of age for metallicity levels appropriate to most Irrs. Unfortunately, some disturbing inconsistencies remain in the details of the age scales (170, 249), and subtle differences exist between clusters and stellar evolution model predictions (26, 112, 113). Still, the analysis of LMC cluster photometry in the classic work of Searle et al. (314), as well as Rabin's (277) investigations of individual cluster spectra, assures us that among younger clusters age is the major determinant of spectral properties, while in very old clusters metallicity is a primary factor. Star clusters thus are a comparatively reliable means for unraveling the stellar age/metallicity strata that hold the histories of galaxies.
Studies of the Magellanic Clouds and other nearby Irrs reveal star clusters covering a full range of age classes, and thus these galaxies have been actively producing stars for at least several billion years (162, 167). Recently photometry has been obtained by Stryker (336, see also 338) down to the main sequence turnoff in the red LMC halo cluster NGC 2257. As this cluster contains a well-defined horizontal branch and RR Lyrae variables, the preferred age calibration method, developed by Rood & Iben (284; see Iben 192) and based on the distance-independent luminosity difference between main sequence turnoff and horizontal branch, can be applied to show that NGC 2257 is as old as Galactic globulars. Evidently the LMC produced or obtained star clusters from the same early epoch as the Milky Way. In contrast to the Milky Way, however, the Magellanic Clouds are still making globularlike star clusters, the ``populous blue clusters'' or ``blue globular clusters'' (156). Although there has been some resistance to considering these as total parallels to young globular clusters, LMC blue globular cluster masses lie in the range of 104-105 M and therefore overlap with true globulars (58, 114, 118, 148, 254). These clusters are not unique to the Magellanic Clouds, and the luminous, near-stellar knot seen in actively star-forming regions of Irrs such as NGC 1569 or NGC 5253 (2, 84, 188, 189, 367, 370) may be populous stellar clusters in early evolutionary phases when OB stars and circumstellar gas are still present. It is therefore not appropriate to attribute the production of globular star clusters only to unique conditions in the early Universe (e.g. 85), but rather there may be a variety of channels for the formation of dense, spheroidal star clusters.
Not all Irrs, however, display the same small-scale spatial patterns of star-forming activity. At one extreme, the low astration rate dwarfs often lack rich clusters and pronounced OB associations, even when massive stars are present (e.g. 288, 301, 369). At the other extreme, some rapidly star-forming amorphous Irrs are also quite smooth in their optical appearances (125, 294, 300) and are pervaded by diffuse optical emission lines from ionized gas (84, 157, 188). It is quite clear that these galaxies may contain large complements of massive young stars, as evidenced by their high H luminosities and hot IUE ultraviolet spectra (219). The optically distinct, large star-forming complexes (OB associations, HII regions, etc.), which are the hallmark of most Irrs, are, however, missing. Perhaps in these systems the individual star-forming sites are overlapping or the stars are forming via a different mechanism than in most Irrs. But in either case, the amorphous Irrs illustrate that kinematically similar galaxies do not necessarily follow identical evolutionary paths. | <urn:uuid:514bf22c-2a7a-4107-ab1f-3da2105baf48> | 2.734375 | 2,070 | Academic Writing | Science & Tech. | 43.318846 |
Both experiments found excesses in the 130-150 GeV mass region. But the excesses did not have enough statistical significance to count as evidence of the Higgs.
Scientists measure statistical significance in units called sigma, written as the Greek letter σ. These high-energy experiments usually require 3σ level of confidence, about 99.7 percent certainty, to claim they’ve seen evidence of something. They need 5σ to claim a discovery. The ATLAS experiment reported excesses at confidence levels between 2 and 2.8σ, and the CMS experiment found similar excesses at close to 3σ.
Still, there's a very long way to go (and more data collection and analysis) before one can actually claim discovery. Unlike pseudosciences where even a weak correlation seems to be sufficient to claim that a phenomenon exists, in high energy physics, not only do you need a high confidence level that your result isn't simply due to chance, but you also need another independent detector, measuring things differently, to agree with your result! The fact that both ATLAS and CMS are getting almost the identical result is a very good start. And it is only a start.
Interestingly enough, the energy range where this is detected is also accessible at the Tevatron. I wonder if CDF and DZero might zero in (no pun intended) in this range and see what their data looks like with various background subtraction schemes. | <urn:uuid:8d0e34fd-6511-4a49-ae76-960a5b675243> | 3.15625 | 294 | Personal Blog | Science & Tech. | 45.976695 |
A couple of years ago, while I knew the word "sequestering," I would have been hard pressed to suggest a use for it other than the forced incarceration of juries, to which the word "sequestration" is quaintly applied by our legal profession. Certainly the phrase "carbon sequestration" would've drawn a blank stare from anybody except certain scientists.
Carbon sequestration, or the forced incarceration of carbon gas so that it does not contribute to global warming, is now commonly discussed, though still rarely implemented. Trapping it by pumping the gas deep underground is the plan:
Today, EPA is proposing a rule that supports promising technologies to prevent industrial emissions of carbon dioxide. Secure, long-term underground storage of the greenhouse gas is one way scientific innovation could lessen the effects of climate change.
"Today's proposal paves the way for technologies that would protect public health and help reduce the effects of climate change," said EPA Administrator Stephen L. Johnson. "With proper site selection and management, geologic sequestration could play a major role in reducing emissions of carbon dioxide into the atmosphere."
EPA's proposed regulation creates a consistent, national framework for the injection of carbon dioxide underground and protection of underground drinking water resources. The rule would create a new class of injection wells under the authority of the Safe Drinking Water Act's Underground Injection Control (UIC) program.
The proposed rule builds on the existing UIC program, including extensive requirements to ensure wells are appropriately located, constructed, tested, monitored, and ultimately, closed with proper funding. It would apply to owners and operators of wells that will be used to inject carbon dioxide into the subsurface for the purpose of long-term storage.
Carbon capture and storage is part of a portfolio of technologies available to reduce greenhouse gas emissions. EPA is coordinating with the Department of Energy on carbon sequestration research and development
Of course, if the CO2 does migrate to the drinking water supply, would we not all enjoy free carbonated water and thus reduce the use of bottled carbonated water or carbonation systems?
Just a wild thought... | <urn:uuid:15bc1129-9080-4690-bae6-4b14ad0e6cfc> | 2.90625 | 429 | Personal Blog | Science & Tech. | 27.765415 |
I'm making a unit converter just to practice. Currently, I've defined a function to figure out what type of conversion to make (distance, time, mass, etc.).
It then calls the correct converter for the type, asks what you're converting from, what you're converting to, and what the value for conversion is.
def mass_converter(): convert_from = raw_input('What unit are you converting from? ') convert_to = raw_input('What unit are you converting to? ') value = raw_input('How many of those do you have? ') if convert_from == "pounds" and convert_to == "kilograms": answer = float(value) * 0.453592 print "That many pounds is %d kilograms." % answer elif convert_from == "kilograms" and convert_to == "pounds": answer = float(value) * 2.20462 print "That many kilograms is %d pounds." % answer else: print "You have not selected a valid unit; please try again." mass_converter()
Currently, if I were to convert 10 pounds to kilograms, it tells me that the answer is 4 kilograms. It seems to be chopping off my decimals. Obviously int(value) will do the same thing. What can I use to keep the exact value entered by the user? | <urn:uuid:67c0683e-eac6-4eac-a694-8d2d65f462ee> | 2.984375 | 290 | Q&A Forum | Software Dev. | 61.675464 |
A set of change values calculated for all Weather Generator variables for a specified future time period. The change factors are obtained by calculating the difference between the modelled baseline climate and the climate given in the UKCP09 probabilistic projections, for each 25 km grid square.
In order to generate future daily and hourly synthetic time series of weather variables, change factors are calculated and are used to perturb the statistics of the Weather Generator (WG). These change factors are calculated on a calendar month basis using the UKCP09 probabilistic projections, and are calculated for each WG variable. The change factors used include changes in the averages of the climate variables and some additional statistical properties for rainfall and temperature.
- An overview of how the Weather Generator works is provided in Section 1.3 of the UKCP09 Weather Generator report.
- Further discussion of how the change factors were validated is provided in Chapter 3 and of how change factors are generated and used is in Annex 4.
- A simpler application of change factors is in the process of morphing baseline climate.
Find out more | <urn:uuid:d3b8d73c-4593-40e0-8dc0-f631506b00ac> | 3.15625 | 220 | Knowledge Article | Science & Tech. | 25.159976 |
Comment: 12:56 - 13:54 (00:58)
Source: Annenberg/CPB Resources - Earth Revealed - 5. The Birth of a Theory
Keywords: "Harry H. Hess", "sea floor spreading", "mid-oceanic ridge", Earth, crust, trench, subduction, "Alfred Wegener", data, geopoetry, paleomagnetism
Our transcription: If mid-ocean ridges were continuously creating new sea floor, it would seem that the Earth must be growing, swelling along the ocean ridges like a ball slowly being inflated.
But scientists saw no convincing evidence for an expanding Earth.
How, then could the excess oceanic crust be explained?
Hess suggested that the ocean floor simply sinks back into the planet at deep marine trenches.
He claimed that this process, now called subduction, destroys the surface formed by sea floor spreading.
Just as Wegener's hypothesis was weakened by lack of data, so, too, was the model of sea floor spreading.
Hess cautiously referred to his own theory as "Geopoetry," but supporting evidence would come from the emerging field of paleomagnetism.
Geology School Keywords | <urn:uuid:c47750e3-b434-4e39-b51b-c54b2cc579e8> | 4.03125 | 255 | Knowledge Article | Science & Tech. | 52.669932 |
Given the following data model, design a simple hypertext that allows the user to browse the modeled information.
The site publishes data about music artist and their albums. Each album contains a set of tracks (songs).
The hypertext should provide a home page which shows the list of all the artists. The list is paged, and shows 10 elements per page. By clicking on an artist, the user must be able to see the biography or, alternatively, the set of published albums. From the albums list, the album details(duration and list of tracks) must be reachable. | <urn:uuid:ae54ab26-928e-4fc3-be4d-1fa7636c31ca> | 2.84375 | 120 | Documentation | Software Dev. | 57.584433 |
A radio altimeter could be used to index the height at which each picture was taken. The camera system, developed by the Eastman Kodak Company for the Air Force, would be available within the year. The alternative approach of using direct television appeared less attractive because the resolution of the television system was at least an order of magnitude lower than the comparable photographic system. Because of the difficulty in placing an instrument package in a close lunar orbit, photographs taken by a vehicle orbiting the moon, including those taken of the far side and recorded on magnetic tape for later transmission, would probably have low resolution owing to the distance from the lunar surface. On June 12, Rosen described a new television system which could be used for early attempts at lunar photography. The system, which would be available within a year, would relay pictures comparable to that of the Eastman Kodak camera system. | <urn:uuid:8ba05dbd-1c79-41b9-84fe-ffd29a8d0c4f> | 3.578125 | 174 | Knowledge Article | Science & Tech. | 22.330296 |
A list of numbers that follows a rule is called a sequence. Sequences whose rule is the multiplication of a constant are called geometric sequences, similar to arithmetic sequences that follow a rule of addition. Homework problems on geometric sequences often ask us to find the nth term of a sequence using a formula. Geometric sequences are important to understanding geometric series.
A geometric sequence is a series of numbers where basically going from one to the next [IB] we are multiplying by a constant rate, okay? So right behind me what I have is, we're going from 2 to 6, multiplying by 3 from 6 to 18 we're multiplying by 3 as well. Okay? So that 3 is consistent so therefore I know I have a geometric sequence. Okay.
If this was just 2 terms, I wouldn't actually know what's going on because I could go from 2 to 6 one of 2 ways. I could either add 4 which would be an arithmetic sequence or multiply by 3 which tells me it's geometric. So I need that third term in order to figure out what exactly ki- what kind of sequence it really is, okay?
What we're going to do now is find the general term, find the s sub n in order for a geometric sequence, okay? So we're given the first term. s of 1 is equal to the first term. And in order to find the second term, what we do is take that first term and multiply it by that common rate okay and then we call it r.
To find the third term then we take the second term and multiply it by the rate as well okay. So we went from 2 to 6 and then [IB] 6 to 18 we again multiplied it by that common rate 3. But we know that a sub 2 is actually a sub 1 times r. So what we end up with is this is equal to a sub 1 times r squared. Continuing down the row, a sub 4 is just going to be another rate times the previous term leaving us with a sub 1 times r cubed, so on and so forth. Eventually we're going get to our general term. Ace of n is equal to ace of 1. And if you notice there's always one less rate than the term number, okay. So our second term has one rate, third term has 2 rates, fourth term has 3 rates. So if we're dealing with ace of n we are just going to have r to the n minus 1.
So, that is an introduction to a geometric sequence and the general term for geometric sequence ace of n is equal to ace of 1 times r to the n minus 1. | <urn:uuid:8b2d4637-a7fd-4ef0-8132-a42022142be7> | 3.984375 | 537 | Tutorial | Science & Tech. | 76.519306 |
Unlike other sea birds, the four-feet tall Emperor penguins breed and raise their young almost exclusively on sea ice.
If that ice breaks up and disappears early in the breeding season, massive breeding failure may occur, said the researchers from Woods Hole Oceanographic Institution (WHOI).
"Over the last century, we have already observed the disappearance of the Dion Islets penguin colony, close to the West Antarctic Peninsula," said Stephanie Jenouvrier, the lead author of the study published in the journal Global Change Biology.
"In 1948 and the 1970s, scientists recorded more than 150 breeding pairs there. By 1999, the population was down to just 20 pairs, and in 2009, it had vanished entirely."
Like in Terre Adelie, a coastal region of Antarctica where French scientists have observed penguins for more than 50 years, Jenouvrier thinks the decline of those penguins might be connected to a simultaneous decline in Antarctic sea ice due to warming temperatures in the region.
Disappearing sea ice, the researchers said, may also affect the penguins' food source.
The birds feed primarily on fish, squid, and krill, a shrimplike animal, which in turn feeds on zooplankton and phytoplankton, tiny organisms that grow on the underside of the ice.
If the ice goes, so too will the plankton, causing a ripple effect through the food web that may starve the various species that penguins rely on as prey, Jenouvrier said.
To project how penguin populations may fare in the future, Jenouvrier's team used data from several different sources, including climate models, sea ice forecasts, and a demographic model that Jenouvrier created of the Emperor penguin population at Terre Ad | <urn:uuid:2c2fec87-96cf-4b0c-b8be-f17818c4d392> | 3.8125 | 369 | Truncated | Science & Tech. | 31.327985 |
It’s difficult to conceive of just how large the hot gas halo is, but NASA notes it could extend more than 300,000 light years out from its center, and have a mass equivalent between 10 billion suns and 60 billion suns, or just as many or more than all of the stars in the Milky Way itself, at a temperature “a few hundred times hotter” than the surface of our Sun (between 1 million and 2.5 million kelvin).
The hot gas halo could also help solve the great cosmic mystery of the missing baryons, or particles including protons and neutrons which ancient galaxies have in abundance and which are thought to have composed a sixth of the matter at the universe’s dawn, but which are found in about half that amount in our galaxy and its neighbors.
The newly discovered gas halo itself could be where the baryons have ended up during the course of the universe’s evolution.
Previous studies indicated that the Milky Way, and other nearby galaxies, had a “warm” gas halo (between 100,000 and over 1 million kelvin), but this is the first time evidence of a “hot” gas halo has been uncovered.
NASA released an illustration of the hot gas halo around the Milky Way, seen at the top of this article and in its original ratio below. The Milky Way itself is pictured as a tiny formation in the center, with neighboring galaxies the Small and Large Magellanic Clouds, indicated by their respective abbreviations off to the Milky Way’s lower left.
This story was originally published by Talking Points Memo. | <urn:uuid:e5c93886-7c48-4adc-b5c1-8b0681a289de> | 3.734375 | 343 | Truncated | Science & Tech. | 41.381618 |
Image credit: NASA; image source
The Top of the Atmosphere
In this NASA image (high-res version) captured from the International Space Station (ISS), the top of the blue band marks what is often called the edge of Earth's atmosphere, about 100 km up. Note the moon, faintly visible in the left-center. To learn more, visit The Top of the Atmosphere.
The altitude of the ISS ranges from about 350 km to 450 km. Even at this height, atmospheric drag slowly degrades the orbit, so periodic boosts are required (see NASA's S'Mores), especially when intense solar activity puffs out parts of the atmosphere.
The New York Times on AOL: Sputnik
Fifty years ago, the Soviet Union shocked the world by beating the US into space with Sputnik, a beach-ball-sized satellite whose radio beeps proclaimed the Soviet triumph. To learn about Sputnik, you can visit The New York Times on AOL: Sputnik and also the NASA Sputnik site. | <urn:uuid:8cc707c6-dcd6-465c-a512-a8b56fe14479> | 3.671875 | 215 | Knowledge Article | Science & Tech. | 51.369325 |
- Agronomic trait - A characteristic in a plant or animal that will add economic value to agricultural production. For example, increasing the protein content in dairy cow milk means the milk would be worth more to the farmer.
- Bacteria - Single celled organisms capable of reproduction and growth. Bacteria can be beneficial or harmful.
- Biotechnology - A broad term for a group of technologies based on the application of biological processes. It is used to make or modify foodstuffs, medicines, reduce wastes and environmental impacts and create renewable energy sources. Modern biotechnology is the term used to describe a range of processes and techniques especially at the molecular level. Examples of biotechnology applications include cell culture, genomics, molecular marker-assisted breeding, cloning, bioprocessing and diagnostic testing as well as gene technology (genetic modification).
- Modern biotechnology - Term used to describe a range of processes and techniques, focusing on the genetic level, such as molecular marking, genetic modification and genomics.
- Chromosome - One of the threadlike 'packages' of genes and other DNA in the nucleus of a cell. Different kinds of organisms have different numbers of chromosomes. Humans have 23 pairs in all: 44 autosomes and two sex chromosomes. Each parent contributes one to each pair, so children get half of their chromosomes from their mother and half from their father.
- Clone - A group of genetically identical organisms. Cloning occurs naturally in some instances, for example when a new plant is formed from a cutting or when humans produce identical twins. Usually however, no two organisms are identical, even if they belong to the same species. Genes, cells or entire organisms can be cloned using modern biotechnology methods.Cloning is not genetic modification as genes are not modified but copied exactly.
- DNA - (Deoxyribonucleic acid) is the chemical of which genes are made. It is found in the nucleus of the cells of most living things. The chemicals in DNA are the same for every living organism, however the ordering or sequence of the chemicals varies and it is this variation that determines a plant's, animal's or an organism's physical make-up and the way it functions.
- Gene - A portion of DNA that has a message encoded in its chemical structure. Genes are the inherited genetic instructions that give organisms their characteristics. By changing the sequence of genes, turning off certain genes or inserting new genes changes can be made to an organism.
- Genetic engineering - See genetic modification.
- Genetic enhancement - See genetic modification.
- Gene splicing - See genetic modification.
- Genetic modification - ('gene technology', 'genetic engineering', 'genetic modification/manipulation', 'genetic enhancement', 'gene splicing', 'transgenics' ) A technology used to alter the genetic material of living cells in order to make them capable of producing new substances (e.g. an insect toxin) or functioning differently (e.g. tolerance to saline soil).
- Genetics - The study of heredity and variations in living organisms. Genetics or molecular genetics may also be used to describe the study of genes and their function at a molecular level.
- Genome - The total set of genes in an organism or species. The human genome consists of about 3 billion DNA bases coding for about 30 000 genes, packaged in 23 pairs of chromosomes.
- Genomics - The large-scale discovery of genes. It involves study of the total hereditary material of a cell in an animal or plant, including gene placement along a strand of DNA and function of a particular gene or set of genes.
- Marker gene - A gene, whose presence in easily detectable, which is inserted into a GMO along with the desired gene.
- Micro-organism - A microscopic living thing, such as all bacteria and viruses, many types of fungi and other single-celled lifeforms.
- Molecular markers - Easily identified pieces of DNA that are located near genes of interest. Molecular markers are particularly useful in breeding programs because the DNA marker can be screened for instead of waiting for the gene to be expressed and/or the desirable trait to become apparent in a plant or animal.
- Organism - Any living thing.
- Proteomics/proteome - All the protein produced by an organism's genes are referred to as the 'proteome'. Proteomics is the study of these proteins and how they interact to affect the life of the organism. Gene activity can be studied by looking for the range of proteins which are produced by a particular gene, genome or cell.
- Physiological trait - A characteristic in a plant or animal that determines the way the organism functions. For example, the ability of a plant to conserve water will determine whether it is drought tolerant.
- Transformation system - A method of delivering new genes or DNA to the plant or organism of interest, thereby transforming its genetic structure.
- Transgenic - Refers to an organism containing one or more deliberately inserted genes from another species. Examples are bacteria containing the gene for human insulin and plants that contain the gene for a naturally occurring insecticide. | <urn:uuid:b40fef61-4b42-49c5-be49-815cd5b518c8> | 3.46875 | 1,055 | Structured Data | Science & Tech. | 27.309091 |
http://www.fairewinds.com/content/fukus ... and-future
"Here is what would happen if Unit 4 were to crack and the water were to drain out of the nuclear fuel pool. The fuel is hot enough that it needs to be water-cooled. If air is all there is cooling the fuel, it will burn. It will burn the zircaloy cladding on the fuel, (and) will react with the oxygen to create a fire. And it is a fire that once it starts, cannot be put out by water. Water would make it worse. So the nuclear fuel would have to burn completely before the fire would ever go out.
In the process, all that radiation would go up into the atmosphere and blow all over Japan and all over the world.
There is as much cesium in the fuel pool at Unit 4 as there was in all of the atomic bombs dropped in all of the tests in the 1940's, the 1950's, the 1960's, and into the 1970's. All of the above ground testing has less cesium in it than is in the reactor pool at Fukushima 4 right now. So it is a grave situation. I don't believe that the Japanese Government is moving fast enough. If there is no earthquake, the plan to remove the fuel slowly is going to be adequate. But we cannot wait on Mother Nature. We have to quickly move that fuel out of that pool and onto the ground. The key here is quickly. The Japanese Government finally just this month came up with a plan to build a building around the fuel pool building and begin removing the fuel in 2013 or 2014."http://ajw.asahi.com/article/behind_new ... 1205100051
"Murata has his own predictions.
"If the storage pool should collapse and the 1,535 fuel rods began burning in the atmosphere, an endless amount of radiation would be emitted. Of course, that would mean that Tokyo would become unlivable," he said.
Murata continued: "Just 50 meters from the No. 4 reactor is the common pool for the No. 1 to No. 6 reactors. The common pool holds 6,375 spent nuclear fuel rods. If a fire should occur at the No. 4 reactor pool, the common pool would also not stand a chance."
Just great. We've got the population crashing from 2030 to 2070, then thermageddon 3000, and now this for a triple whammy.
And here we have 130 videos of the end of the world;http://noolmusic.com/search_videos/end_of_the_world | <urn:uuid:15053e72-cc73-4473-9579-698ed29f1b50> | 2.734375 | 544 | Comment Section | Science & Tech. | 82.317958 |