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|Title||Temporal and spatial patterns of laying in the Moluccan megapode Eulipoa wallacei (G.R. Gray)|
|Keywords||Moluccan megapode; Eulipoa wallacei; egg production; lunar synchrony|
|Abstract||The Moluccan megapode Eulipoa wallacei (G.R. Gray, 1860) lays its eggs at night in the sand at communal nesting beaches. The majority of the world’s Moluccan megapode population rely on only two nesting grounds on the islands of Halmahera and Haruku, Indonesia. An understanding of the ecological characteristics of these breeding sites is thus important in terms of conservation. Studies of the largest of the two nesting grounds in Halmahera have shown specific temporal and spatial patterns of egg laying. In this paper I discuss the adaptive significance and conservation implications of these laying patterns.|
|Download paper|| http://www.repository.naturalis.nl/document/46262 | | <urn:uuid:98b4fecc-fb15-4189-8e5b-661392044a09> | 2.734375 | 228 | Structured Data | Science & Tech. | 37.591538 |
During the Star Wars years of the 1980s, Tom Paterson worked at a defense think tank creating elaborate mathematical models to help military commanders quickly decide which weapons to deploy to counter incoming missiles. Inputs from hundreds of sensors had to be combined to generate a consummate picture of events that would be unfolding in a matter of minutes, enabling the fateful choice about when to launch.
When the cold war ended, Paterson, like many defense engineers, tried to find a way to apply his skills elsewhere. He ultimately took on a task that made shooting down missiles seem pedestrian. A challenge faced by engineers in the Star Wars program--designing software to pick out critical targets despite an overload of data--carried over to simulations of how drugs work in the metabolic and immune systems that drive the most complex machine we know.
This article was originally published with the title Reverse-Engineering Clinical Biology. | <urn:uuid:8c5268a3-fb7e-4809-b768-86b4ebe3e60c> | 2.984375 | 180 | Truncated | Science & Tech. | 25.887308 |
These is a drawing of the interior of Io.
Click on image for full size
Interior of Io
The diagram to the left shows the interior of Io.
When the Galileo spacecraft flew by Io it took measurements which showed that Io was separated into two layers, as shown in this picture.
Thus scientists think that Io has a large core, covered with a rocky material. There is no ice within Io.
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Differentiation is a scientific term which really means "to separate". In their earliest history, elements which made the planets would part into separate regions, if the planet were warm enough. This...more
Galileo is a spacecraft that has been orbiting Jupiter for eight years. On September 21, 2003, Galileo will crash into Jupiter. It will burn up in Jupiter's atmosphere. The crash is not an accident! The...more
Amalthea was discovered by E Barnard in 1872. Of the 17 moons it is the 3rd closest to Jupiter. Amalthea is about the size of a county or small state. Amalthea is named after the goat in Greek mythology...more
Callisto was first discovered by Galileo in 1610. It is the 2nd largest moon in the solar system, and is larger than the Earth's moon. It is about as big as the distance across the United States. Callisto...more
Measurements by the Galileo spacecraft have been shown that Callisto is the same inside from the center to the surface. This means that Callisto does not have a core at the center. This means that, unlike...more
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The surface of Callisto is deeply marked with craters. Craters are the little white marks in the picture. It looks like it might be the most heavily cratered body in the whole solar system. And some of...more | <urn:uuid:889341f1-6688-4305-a1ca-a53e92e4feaa> | 3.8125 | 466 | Content Listing | Science & Tech. | 64.861136 |
In a typical year, it is not uncommon for a dozen or so comets to come within range of amateur telescopes. During the month of October, 2010, a small comet will pass unusually close to Earth. On Oct. 20, Comet Hartley 2 will pass just over 11 million miles (18 million km) from Earth. That is close enough for the comet to be seen through binoculars or even, in the darkest skies, with the naked eye.
Amateur stargazers aren’t the only ones looking out for Hartley 2 this month. In September 2007, NASA woke up its hibernating DI spacecraft and, in November, sent it the maneuvering instructions to intercept Hartley 2. The spacecraft is precisely on schedule to rendezvous with the comet on November 4 as it approaches the sun.
This week’s online current events activity is a study of comets, the Hartley 2 Comet, and NASA’s attempt to study it.
Begin your investigation into comets by visiting Worldbook@NASA, which features excellent overviews on many topics related to space and astronomy, including Comets. As you read this page, look for answers to the following questions:
- What are some of the ingredients that make up a comet?
- How big are most comets?
- How does a comet tail form, and which direction does it always point?
- What is the relationship between comets and meteor showers?
- What have scientists learned about the nucleus of a comet?
More information about comets can be found at the Nine Planets site. As you read, look for answers to these questions:
- Name two examples of comet appearances in antiquity (ancient human history)
- How many comets have been cataloged?
- What are the five parts of a comet?
- How do comets “die”?
Comet Hartley 2
Now that you have some solid background information about comets in general, let’s see what we can learn about Comet Hartley 2. Start by going to the web site of Sky and Telescope magazine, and read Comet Hartley 2 At Its Best, written by Greg Bryant. This first half of the page is an ongoing blog with dated status updates, followed by the original article. As you read, just understand that you are reading backwards in time.
When you get to the October 8 update, watch the wide-field animation created by Ernesto Guido and Giovanni Sostero. Can you see the slight movement of the comet against the stationary star field?
As you read the original article, look for answers to the following questions:
- In what year was Hartley 2 discovered?
- Why does the moon play a factor in viewing comets?
- What does the EPOXI spacecraft’s name stand for?
- How close will the spacecraft get to the comet?
- What does the number 2 mean in “Hartley 2”?
- Why was this comet beyond visual discovery until after 1982?
Learn more about the EXOXI mission by visiting the official mission web site. From the home page, click Mission on the left and read the 10 phases of the mission. What is the purpose of the Earth fly-bys? What happens during the Comet Approach Phase? What will scientists be looking for during the Encounter Phase? What data will be gathered?
Finish your online study of comets this week by Comparing Comets. This is a student activity developed by NASA in which students can make their own observations based on photos of two different comet nuclei. Print this worksheet or follow along online and record your answers separately. Follow the directions on each page. On page 2, as you are looking at the two photos of comet surfaces, listen to this audio recording of students making their own observations about the comets in a teacher-led discussion.
Comets are not easy to study. Because of their speed and orbit, it is (currently) impossible for humans to travel to comets to make firsthand observations. Instead, scientists send up remotely controllable probes to intercept comets, take photographs, and make a variety of different measurements. This practice is not limited to astronomers. For centuries humans have been creating tools used to measure, weigh, count, or in many other ways analyze things that are beyond our physical senses. In a current or recent issue of the e-edition, look for news stories that cite examples of people using tools to measure or analyze. A good example might be DNA testing for criminal evidence, but you will find many others. Based on your findings, how important have these tools become in our daily lives? Why is it becoming increasingly important to measure, collect, and analyze information? | <urn:uuid:bae30682-110c-416b-bf84-eaae0f65eb55> | 4.28125 | 978 | Knowledge Article | Science & Tech. | 54.011878 |
Posted Aug 24, 2003 by Joe Otten
The thing that has always puzzled me about black holes is what happens to the entropy of objects that fall into them?
By its description, a single infinitely dense point seems to have a very low entropy. But if we then let a high entropy object fall into a black hole, we appear to have a contradiction to the second law of thermodynamics.
This topic is an active one in the field of astrophysics and quantum gravitation. In general, however, it is required of a black hole that its event horizon always increase, much like the total entropy of a closed system (i.e. - the universe). This thought lead to the hypothesis that a black hole's entropy is proportional to its event horizon's surface area. This came to be the Bekenstein-Hawking Formula:
If a black hole has an entropy, then it follows all the other laws of thermodynamics and has a temperature, also. So the black hole will radiate energy. This is where things start getting fuzzy. How can something that is impossible to escape radiate anything? I'm afraid I don't know much about what's new in that field of thought.
Thanks for that.
There is Hawking radiation, but I guess that is not what you are talking about. Could it be a mistake to consider a black hole demarcated by its event horizon to be an object, and thus to apply thermodynamic principles to that object.
After all the event horizon is not a physical structure and need not be in the same place from one moment to the next. (That episode of Voyager where the ship was stuck inside the event horizon of a black hole, looking for a crack to get out would have been hilarious if it had been slightly less obtuse.)
The natural answer is that the laws of physics break down in a black hole. The entropy just vanishes. Entropy is a property of the universe, and all properties of the universe break down at the event horizo of a black hole.
Please note that Not Panicking Ltd is not responsible for the content of any external sites listed. The content on h2g2 is created by h2g2's Researchers, who are members of the public. Unlike Edited Guide Entries, the content on this page has not necessarily been checked by a h2g2 editor. In the event that you consider anything on this page to be in breach of the site's House Rules, please | <urn:uuid:9616e3bc-10ce-4eb0-8304-f62106edf360> | 2.75 | 505 | Comment Section | Science & Tech. | 56.145625 |
As soon as they lay their eggs, the female cichlids scoop them up into their mouths and incubate them until they hatch.
R. Buckminster Fuller was a twentieth century scientist, philosopher, inventor, and was also named a great architect.
Frogs also aren’t fussy eaters: any live prey will do. Some large species of frogs can gulp up a mouse, bat, or small snake in one mouthful, which is fortunate, because frogs can’t chew. If they have any teeth at all, they’re usually only good for holding onto the prey. | <urn:uuid:fb056eb6-e471-4532-8e19-5716b878c886> | 2.6875 | 127 | Knowledge Article | Science & Tech. | 64.371667 |
About this Base Converter
Base-2 to base-62 are accepted. "A" stands for 10, "Z" for 35, "a" (lower-case) for 36 and "z" (lower-case) for 61. Decimals are supported. This is a custom function because PHP's base_convert() doesn't accept decimals and only goes up to base-36. It's only as precise as PHP is, so don't blindly copy the smallest decimal thinking it will always be correct.
Is there any standard for displaying numbers higher than base-36? I've used lowercase letters to go up to base-62, but I couldn't find if that's what is commonly done. (Then again, I guess nothing is commonly done, since anything beyond base-16 doesn't really have much use, to my knowledge.)
Fun game: Enter your name and supply base-36 (or higher) as the starting base and see what number you get in another base. My first name in base-38 for instance returns EPKCO in base-42.
What's this about?
A base is the system with which numbers are displayed. If we talk about base-n, the system has n characters (including 0) available to display a number. Numbers are represented with digits which are smaller than n. Therefore, 3 in base-3 is 10: because that system doesn't have a "3", it starts over (1, 2, 10, 11, 12, 20, 21, 22, 100, etc.).
The base we usually use is base-10, because we have 10 (when including 0) digits until we start over again (8,9,10). In base-2 (binary), we only have 2 characters, i.e. 0 and 1, until we start over again. Following this example, the binary number 10 is 2 in our (base-10) system.
Does it make sense that a finite fraction ("decimal") is infinite in another base?
It totally does. If you want to convert 645 from base-8 to base-10, you do 6*82 + 4*81 + 5*80 = 421. After the comma you keep on decrementing the exponent, meaning that if you have 21.35 in base-7 you get to its base-10 equivalent by doing 2*71 + 1*70 + 3*7-1 + 5*7-2. 7-1 (= 1/7), however, is 0.142857... in base-10, while it's simply written as 0.1 in base-7. | <urn:uuid:ce241d9c-a5e7-42c3-95fb-ca084d804bf4> | 3.3125 | 547 | Q&A Forum | Software Dev. | 86.924719 |
The ICM and the IGM show metal lines in the X-ray spectra. These metals cannot have been produced in the gas, but they must have been produced in the galaxies and subsequently transported from the galaxies into the ICM/IGM by certain processes like e.g. ram-pressure stripping, galactic winds, galaxy-galaxy interaction or jets from active galaxies. The metallicity is the best indicator for finding out which of these processes are most important. Of special interest is the distribution of metals. So far there are only few examples of measured metallicity variations in real 2D maps and not only profiles. In CL0939+4713 we find different metallicity in the different subclusters (De Filippis et al. 2002). In the Perseus cluster also clear metallicity variations were found (Schmidt et al. 2002). 1D profiles are not very useful in this context because photons from regions in the cluster which are very far apart are accumulated in the same spectrum.
Apart from the metallicity distribution also the evolution of the metallicity is interesting. As soon as enough XMM and CHANDRA observations of distant clusters are available we can compare the metallicities in these clusters with those of nearby clusters. This is another way of distinguishing between the enrichment processes as different processes have different time dependence. In addition element ratios can be derived, e.g of Fe and -elements to get information on the different types of supernovae that have contributed to the metal enrichment.
Various processes have been suggested for the transport of gas from the galaxies to the ICM/IGM. 30 years ago Gunn & Gott (1972) suggested ram-pressure stripping: as the galaxy moves through the cluster and approaches the cluster centre it feels the increasing pressure of the intra-cluster gas. At some point the galaxy is not able anymore to retain its ISM. The ISM is stripped off and lost to the ICM and with it all its metals. Many numerical simulations have been performed to investigate this process, first 2D models (Takeda et al. 1984; Gaetz et al. 1987; Portnoy et al. 1993; Balsara et al. 1994). With increasing computing power also more detailed 3D models could be calculated (Abadi et al. 1999; Quilis et al. 2000; Vollmer et al. 2001; Schulz & Struck 2001; Toniazzo & Schindler 2001). In Fig. 6 such a simulated stripping process is shown for an elliptical galaxy.
Figure 6. Gas density (grey scale) and pressure (contours) of a galaxy moving downwards towards the cluster centre. The arrows show the Mach vectors (white when M > 1, black otherwise). The gas of the galaxy is stripped due to ram pressure (from Toniazzo & Schindler 2001).
Another possible process is galactic winds e.g. driven by supernovae (De Young 1978). Also for this process simulations have been performed on order to see whether only winds can account for the observed metallicities. The results were quite discordant as the following two examples show. Metzler & Evrard (1994, 1997) found that winds can account for the metals, while Murakami & Babul (1999) concluded that winds are not very efficient for the metal enrichment. In the simulations of Metzler & Evrard quite steep metallicity gradients showed up which are not in agreement with observations.
A third possible process is galaxy-galaxy interactions, like tidal stripping or galaxy harassment. Also during these interactions a lot of ISM can be lost to the ICM and IGM. This process is very likely more efficient in groups of galaxies, because in these systems the relative velocities are smaller and therefore the interaction timescales are longer. The ram-pressure stripping on the other hand is probably less efficient in groups because not only the pressure of the IGM is lower than that of the ICM, but also the velocities are smaller. This is also very important as the stripping is about proportional to gas v2.
A forth possible mechanism is jets emitted by active galaxies. These jets can also carry metals. Fig. 7 shows the interaction of jets with the ICM as it was discovered by X-ray observations. In the cluster RBS797 minima in the X-ray emission have been detected in a CHANDRA observation (Schindler et al. 2001). The X-ray depressions are arranged opposite with respect to the cluster centre. It is very likely that the pressure of the relativistic particles in the jets push away the X-ray gas. Preliminary radio observations with the VLA confirm this hypothesis.
Figure 7. CHANDRA image of the central part of the cluster RBS797 (from Schindler et al. 2001). There are depressions in the X-ray emission which are located opposite to each other with respect to the cluster centre (see arrows). These depressions can be explained by an active galaxy in the centre of the cluster, which has two jets. The pressure of the relativistic particles in the jets push away the X-ray gas resulting in minima in the X-ray emission.
Simulations with different enrichment processes were also performed on cosmological scales. Also here quite discordant results have been found as the two following examples show. Gnedin (1998) found that galactic winds play only a minor role, while galaxy mergers eject most of the gas. In contrary to these results Aguirre et al. (2001) concluded that winds are most important and ram-pressure stripping is not very efficient. The reason for these differences are probably the large ranges in scale that are covered by these simulations, from cosmological scale down to galaxy scales. Therefore only a small number of particles are left for each single galaxy and hence galaxies are not well resolved. This can be the reason for the discordant results.
In order to clarify this we are currently performing comprehensive simulations, which include the different enrichment processes. | <urn:uuid:b0a9cfe3-eed9-450e-b1d8-fa1847ed42a6> | 3.109375 | 1,246 | Academic Writing | Science & Tech. | 47.962867 |
One of the biggest questions in science has always been how the universe formed. Over the last century, we've made a lot of progress about understanding the way it has developed: The Big Bang Model. With the most sophisticated telescopes ever built, scientists have now made measurements confirming the accuracy of this model within just moments of when the universe began.
Despite all this evidence, the question remains: What actually started the whole process?
Physics actually does have an answer to this question - one which doesn't require the intervention of a creator deity - and in his newest book physicist Lawrence Krauss lays the explanation out in language that is accessible to non-scientists. If this sounds interesting, check out our review of Krauss's A Universe From Nothing.
If you've read the book, then be sure to let us know what you thought of it. Could the laws of quantum physics and relativity have created the universe as we know it? Is God a necessary component of the universe? | <urn:uuid:00b71dff-bd72-4193-b5dd-967dea413b6c> | 3.359375 | 198 | Personal Blog | Science & Tech. | 46.765129 |
A theoretical analysis of recent experiments suggests that a key feature of a topological quantum computer—the unusual statistics of quasiparticles in the quantum Hall effect—may finally have been observed.
By exploiting the concept of particle-hole duality, one can realize a point junction between integer and fractional quantum Hall phases, which constitutes a crucial building block towards possible applications of the quantum Hall effect.
The fractional quantum Hall effect, thought to be special to two dimensions, may also flourish in three, providing a possible explanation for anomalies observed in certain 3D materials in high magnetic fields.
Physics2, 24 (2009) – Published March 30, 2009
The surprising prediction that currents can flow forever in small normal metal rings was confirmed almost twenty years ago. Highly precise new experiments find good agreement with theory that was not seen till now.
H. A. Fertig,
Physics2, 15 (2009) – Published February 23, 2009
Measurements of the heat transport at the edges of two-dimensional electron systems appear to provide explanations about the quantum Hall state that have not been forthcoming via charge transport experiments.
Crystalline structures have been observed in nanoislands of electrons floating above superfluid helium. The energy required to add or subtract an electron from these quantum-dot-like islands agrees well with theory.
Physics1, 36 (2008) – Published November 24, 2008
The esoteric concept of “axions” was born thirty years ago to describe the strong interaction between quarks. It appears that the same physics—though in a much different context—applies to an unusual class of insulators.
Graphene has been idealized as a two-dimensional electron system in which the electrons behave like massless fermions, but how “perfect” is it? Scientists now show they can prepare free-standing sheets of graphene that have some of the highest electron mobilities of any inorganic semiconductor.
A decade ago, experimentalists showed that persistent currents can flow in nonsuperconducting mesoscopic metal rings, but there was no theory that correctly explained the magnitude or direction of the unexpectedly large currents. Theorists are now proposing a simple idea that may at last explain these results.
Electrons in graphene can be described by the relativistic Dirac equation for massless fermions and exhibit a host of unusual properties. The surfaces of certain band insulators—called topological insulators—can be described in a similar way, leading to an exotic metallic surface on an otherwise “ordinary” insulator. | <urn:uuid:a7f014e1-dfcd-46b7-926a-0554c521be0c> | 3 | 528 | Content Listing | Science & Tech. | 26.498604 |
Cascading Importance: Wolves, Yellowstone, and the World Beyond. A talk with William Ripple. Jonathan Batchelor Winter 2013.
Large Predators and Ecological Health WAMC Northeast Public Radio August 23.
Top Predators Protect Forests The Wildlife Professional Summer 2012.
Cougars Encourage Lizards in Zion Year of the Lizard News July 2012.
Predators and Plants Science Update April 26.
Herbivores take toll on ecosystem The Register Guard April 10.
Loss of predators affecting ecosystem health OSU Press Release April 9.
Wolves to the Rescue Defenders of Wildlife Defenders Magazine Winter 2012.
Wolves help Yellowstone, researchers say Local 10, CNN January 5, 2012.
How Wolves Are Saving Trees in Yellowstone Good Environment January 4, 2012.
Study says that with more wolves and fewer elk, trees rebounding in portions of Yellowstone The Washington Post January 3, 2012.
Yellowstone transformed 15 years after the return of wolves OSU Press Release Dec 21, 2011.
Lopped Off Science News November 2011.
The Crucial Role of Predators: A New Perspective on Ecology Yale Environment 360 September 15, 2011.
For Want of a Wolf, the Lynx Was Lost? Science Magazine September 9, 2011.
Red wolf comeback in N.C. helps other animals thrive The Charlotte Observer August 13, 2011.
The case for large predators The Oregonian July 23, 2011.
Study tracks effects of declining predator numbers The Register-Guard July 17, 2011.
Loss of top predators causes chaos, including fires and disease The Vancouver Sun July 15, 2011.
Loss of large predators disrupting multiple plant, animal and human ecosystems OSU Press Release July 14, 2011.
Loss of Top Predators Has Far-Reaching Effects PBS Newshour July 14, 2011.
Oregon State researchers: Predators Important To Ecosystems OPB Earthfix July 14, 2011.
Using Wolves and Other Predators to Restore Western Ecosystems Eugene Natural History Society November 2010.
Sharks and Wolves: Predator, Prey Interactions Similar on Land and in Oceans US News Nov. 15, 2010.
New Theory for Megafaunal Extinction American Archaeology Fall 2010.
New theory on what killed off the woolly mammoths Science Fair, USA Today July 2, 2010.
Study probes role of key predators in ecosystem disruption Corvallis Gazette-Times July 1, 2010.
Ripple Marks: The Story Behind the Story Oceanography June, 2010.
Destination Science 2010: The reintroduction of wolves has helped bring a severely damaged ecosystem back from the brink Discover Magazine April, 2010.
Mess O' Predators The Discovery Files January 20, 2010.
Top predators' decline disrupts ecosystems, says study The Epoch Times October 14-20, 2009.
Ripple receives Spirit of Defenders Award for Science The Barometer October 7, 2009.
Wolves, jaguars are out, coyotes, foxes are in: New global study The Arizona Daily Star - Blogging in the desert October 2, 2009.
Decline in big predators wreaking havoc on ecosystems, OSU researchers say The Oregonian October 1, 2009.
Where Tasty Morsels Fear to Tread The New York Times: The Wild Side September 29, 2009.
Wolves to the Rescue in Scotland ScienceNOW Daily News (Science Magazine) July 22, 2009.
Can wolves restore an ecosystem? Seattle Times January 25, 2009.
Wolf Loss and Ecosystem Disruption at Olympic National Park Island Geoscience Fall 2008.
The Silence of the Wild William Stolzenburg essay, Powell's Books 2008.
Century without the wolf The Oregonian July 30, 2008.
Monitoring cougar in Yosemite Valley Difficult San Mateo County Times June 22, 2008.
Lack of predators harms wild lands San Mateo County Times June 21, 2008.
Cougar decline resuls in critical changes to Yosemite ecosystem Land Letter - E&E Publishing Service May 8, 2008.
Yosemite: Protected but Not Preserved. Science Magazine May 2, 2008.
How humans, vanishing cougars changed Yosemite San Francisco Chronicle May 2, 2008.
Wolves and Elk Shape Aspen Forests CurrentResults.com 2007.
Return of the Wolves. Weekly Reader December 2007.
Oregon State is No. 1 in conservation biology. The Oregonian via OregonLive.com September 6, 2007.
Yellowstone's Wolves Save Its Aspens. The New York Times August 5, 2007.
Presence Of Wolves Allows Aspen Recovery In Yellowstone. Science Daily (ScienceDaily.com) July 31, 2007.
Apsens Return to Yellowstone, With Help From Some Wolves. www.sciencemag.org July 27, 2007.
Yellowstone trees get help from wolves. MSNBC.com July 27, 2007.
It All Falls Down: A plummeting cougar population alters the ecosystem at Zion National Park. Smithsonian Magazine/Smithsonian.com December, 2006.
Cougar Predation Key To Ecosystem Health. ScienceDaily.com / University of Toronto October 25, 2006.
The Ecology of Fear. emagazine.com March 2006.
Hunting Habits of Yellowstone Wolves Change Ecological Balance in Park. The New York Times Oct. 18, 2005.
Episode 3 "Predators", Strange Days on Planet Earth. National Geographic April 2005.
Ecological changes linked to wolves. The Seattle Times Jan. 12, 2005.
Mystery in Yellowstone: wolves, wapiti, and the case of the disappearing aspen. Notable Notes, Oregon State University 2004.
A Top Predator Roars Back. On Earth Summer 2004.
Research Shows Wolves Play Key Role in Ecosystems. ABC News Dec. 15, 2004.
Who's Afraid of the Big Bad Wolf? The Yellowstone Wolves Controversy. Journal of Young Investigators Nov. 2004.
Lessons from the Wolf. Scientific American Jun. 2004.
Wolves linked to vegetation improvements. Wyoming Tribune-Eagle Mar. 18, 2004.
Endangered Wolves Make a Comeback. National Public Radio Feb. 20, 2004.
Wolves' Leftovers Are Yellowstone's Gain, Study Says. National Geographic News Dec. 4, 2003.
Wolves enhance biodiversity in Yellowstone, report says. Oregonian Oct. 29, 2003.
Wolves linked to tree recovery. Billings Gazette Oct 29, 2003.
A top dog takes over. National Wildlife Federation Oct./Nov. 2003.
OSU student maps L&C wildlife observations. Corvallis Gazette-Times Mar. 28, 2003.
Aspens wither without wolves. Herald and News Nov. 19, 2000.
Observatory: Fates of wolf and aspen. New York Times Sep. 26, 2000.
Quiet Decline: Fewer wolves and wildfires may have led to aspen's decline. ABC News Sep. 21, 2000.
Support for the Leopold site is provided by: Dept. of Forest Resources, OSU,
280 Peavy Hall, Corvallis, OR 97331.
phone: 541-737-4951 | fax: 541-737-3049
Copyright 2003, Oregon State University | Disclaimer. | <urn:uuid:8d55d791-f938-4846-9347-17c697c329a0> | 3.390625 | 1,508 | Content Listing | Science & Tech. | 56.17466 |
This Dawn FC (framing camera) image shows some of the undulating terrain in Vesta’s southern hemisphere. This undulating terrain consists of linear, curving hills and depressions, which are most distinct in the right of the image. Many narrow, linear grooves run in various directions across this undulating terrain. There are some small, less than 1 kilometer (0.6 mile) diameter, craters in the bottom of the image. These contain bright material and have bright material surrounding them. There are fewer craters in this image than in images from Vesta’s northern hemisphere; this is because Vesta’s northern hemisphere is generally more cratered than the southern hemisphere.
This image is located in Vesta’s Urbinia quadrangle and the center of the image is 63.0 degrees south latitude, 332.2 degrees east longitude. NASA’s Dawn spacecraft obtained this image with its framing camera on Oct. 25, 2011. This image was taken through the camera’s clear filter. The distance to the surface of Vesta is 700 kilometers (435 miles) and the image has a resolution of about 70 meters (230 feet) per pixel. This image was acquired during the HAMO (high-altitude mapping orbit) phase of the mission.
The Dawn mission to Vesta and Ceres is managed by NASA’s Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, for NASA’s Science Mission Directorate, Washington D.C. UCLA is responsible for overall Dawn mission science. The Dawn framing cameras have been developed and built under the leadership of the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, with significant contributions by DLR German Aerospace Center, Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The Framing Camera project is funded by the Max Planck Society, DLR, and NASA/JPL.
More information about Dawn is online at http://dawn.jpl.nasa.gov.
Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA | <urn:uuid:070933fb-a8a3-406a-8b89-95e2d798f517> | 3.265625 | 459 | Knowledge Article | Science & Tech. | 44.139553 |
|Freshwater Mussels of the Upper Mississippi River System|
Mussel Conservation Activities
2005 Highlights: Possible fish predation of subadult Higgins eye was observed in the Upper Mississippi River, Pools 2 and 4.
Subadult Higgins eye pearlymussels (Lampsilis higginsii) from the Upper Mississippi River, Pools 2 and 4. Shell damage may be due to predation by fish (i.e. common carp or freshwater drum). Top photo by Mike Davis, Minnesota Department of Natural Resources; bottom photo by Gary Wege, U.S. Fish and Wildlife Service.
Species Identification and Location • Threatened and Endangered Mussels • Life History • Ecology • Mussel Harvest on the River • Current Threats • Mussel Conservation Activities • Ongoing Studies and Projects • Multimedia • Teacher Resources • Frequently Asked Questions • Glossary • References • Links to Other Mussel Sites
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HELCOM Indicator Fact Sheets for 2005
As the environmental focal point of the Baltic Sea, HELCOM has been assessing the sources and inputs of nutrients and hazardous substances and their effects on ecosystems in the Baltic Sea for almost 30 years. The resulting indicators are based on scientific research carried out around the Baltic Sea under the HELCOM PLC and COMBINE monitoring programmes. During the past few years, HELCOM Indicator Fact Sheets have been compiled by responsible institutions and approved by the HELCOM Monitoring and Assessment Group. The Indicator Fact Sheets for 2005 are listed in the navigation menu on the left and older ones can be found in the Indicator Fact Sheet archive.
The development of sea surface temperature in the Baltic Sea in 2004 was characterised by rather cold months of June and July and by a warm August. The wave climate in the northern Baltic Sea in 2004 was charactrised by a spring season that was calmer than usual and by a storm in December during which the significant wave heigth in the northern Baltic Proper reached a record value of 7.7 meters. The following ice winter was, by the extent of the ice cover, classified as normal. The break up of ice was in most waters earlier than normal and on the 23rd of May the Baltic Sea was ice free.
Life pulsates according to water inflows
The present state of the Baltic Sea is not only the result of the anthropogenic pressures but is also influenced hydrographic forces, such as water exchange between the Baltic Sea and the North Sea. After the major Baltic inflow in January 2003, which renewed most of the deep water in the Baltic Sea, no new major inflow has taken place and the near-bottom water in the Bornholm and eastern Gotland Basin returned back to anoxic conditions in the middle of 2004.
The Baltic Sea continues to suffer the impacts of human activities
Baltic Sea habitats and species are threathened by eutrophication and elevated amounts of hazardous substances as a result of decades of human activities in the surrounding catchment area and in the sea.
Eutrophication is the result of excessive nutrient inputs resulting from a range of anthropogenic activities. Nutrients enter the either via runoff and riverine input or through direct discharges into the sea. Although nutrient inputs from point sources such as industries and municipalities have been cut significantly, the total input of nitrogen to the Baltic Sea is still over 1 million tonnes per year, of which 25 % enters as atmospheric deposition on the Baltic Sea and 75 % as waterborne inputs. The total input of phosphorus to the Baltic Sea is ca. 35 thousand tonnes and enters the Baltic Sea mainly as waterborne input with the contribution of atmospheric deposition being only 1-5 % of the total. The main source of nutrient inputs is agriculture. (Please note that Indicator Fact Sheets on nutrient inputs to the Baltic Sea will be published in the near future).
The inputs of some hazardous substances to the Baltic Sea have been reduced considerably over the past 20 to 30 years. In particular discharges of heavy metals have decreased. The large majority of heavy metal enters the Baltic Sea via rivers or as direct discharges: 50 % for mercury, 60-70 % for lead and 75-85 % for cadmium. The remaining share of inputs is mainly from atmospheric deposition of these heavy metals.
Eutrophication intensifies phytoplankton blooms
The waterborne loads for nitrogen and phosphorus were significantly higher in 2004 compared to the previous year, partly due to the natural flutuations in inputs caused by varying hydrographical conditions. Annual emissions of nitrogen from the HELCOM Contracting Parties were lower in 2003 than in 1995. Mainly because of interannual changes in meteorology, no significant temporal pattern in nitrogen depositions to the Baltic Sea and its sub-basins can be detected, however depositon in 2003 was 11% lower than in 1995.
Eutrophication is an issue of major concern almost everywhere around the Baltic Sea area. The satellite-derived chlorophyll-like pigments in the Baltic Sea are clearly higher than in the Skagerrak and North Sea. The average biomass production has increased by a factor of 2.5 leading to decreased water clarity, exceptionally intense algal blooms, more extensive areas of oxygen-depleted sea beds as well as degraded habitats and changes in species abundance and distribution.
Annual integrated rates for sedimentation of organic matter in the Gotland Sea have not show significant trends between 1995 and 2003. However, decrease in water clarity has been observed in all Baltic Sea sub-regions over the last one hundred years, with it being most pronounced in the Northern Baltic Proper and the Gulf of Finland.
Although no rising trend can be detected in spring blooms from 1992 to 2005, the 2005 spring bloom in the Gulf of Finland was more intense than in the previous year while negligable in the Arkona Basin.
Due to the poor weather during the summer of 2004, there were no major cyanobacteria blooms that year. As a result, levels of dissolved inorganic nutrients in the winter nutrient pool remained extremely high throughout the Baltic Proper and meant that the risk for severe cyanobacterial blooms remained. The average concentrations of dissolved inorganic nitrogen were lower in all regions except at the entrance to and within the Gulf of Finland throughout the year 2004 when compared to the reference (the average of the years 1993-2003). This was confirmed by the 2005 summer blooms of cyanobacteria being amongst the most intense and widespread ever encountered in the Northern and Central Baltic Proper. High surface water temperatures are a prerequisite for intensive blooms of toxic Nodularia species.
In 2004, the abundance of the nitrogen fixing cyanobacteria as well as the ratio between the toxic Nodularia spumigena and the non-toxic Aphanizomenon flos-aquae were almost at the same level as in the previous four years.
Heavy metals and organic pollutant still persistent in marine environment
The inputs of some hazardous substances to the Baltic Sea have reduced considerably over the past 20 to 30 years. However, the concentrations of heavy metals and organic pollutants in sea water are still several times higher in the Baltic Sea compared to waters of the North Atlantic. As a result of efforts to reduce pollution, annual emissions of heavy metals to the air have decreased since 1990 and consequently their annual deposition onto the Baltic Sea has also halved since 1990. Riverine heavy metal loads (notably cadmium and lead) have also decreased for most of coastal states.
Concentrations of contaminants in fish vary according to substance, species and location, but in general, the concentrations of cadmium, lead and PCBs have decreased. Still the content of dioxins in the fish muscle may exceed the authorized limits set by the European Commission.
Overall the levels of radioactivity in the Baltic Sea water and biota have shown declining trends since the Chernobyl accident in 1986, which caused significant fallout over the area. Radioactivity is now slowly transported from the Baltic Sea to the North Sea via Kattegat. The amount of caesium-137 in Baltic Sea sediments however has remained largely unchanged, with highest concentrations in the Bothnian Sea and the Gulf of Finland.
Habitats and species under threat
This year HELCOM introduces its first biodiversity indicators. The degenerating state of the the Baltic Sea affects marine life in many ways. Macrobenthic communities have been severely degraded by increased eutrophication throughout the Baltic Proper and the Gulf of Finland and are below the longterm averages. Populations of the amphipod Monoporeia affinis have crashed in the Gulf of Bothnia and the invasive polychaete Marenzelleria viridis has spread.
The lack of salt water inflows has diminished the habitat layer for heterotrophic organisms in general and those of marine origin, such as copepods, in particular. Although the total number of copepods has not change dramatically, the ratio between different species has been affected which in turn has had consequences in higher trophic levels. Herring for instance has suffered from a decline in its favoured diet and now competes with sprat for other species of copepods.
Decrease in observed illegal oil spills
An increase in the number of maritime transportation during the past decade has increased the potential for an increased numbers of illegal oil discharges. Since the late 1990s ships have been required to deliver oil or oily water from the machinery spaces as well as from ballast or cargo tanks to reception facilities in ports. As of 1999, the number of observed illegal oil discharges has gradually been decreasing every year, but in 2004, still almost 300 illegal spills were detected.
Information on the long-term varaitions in the Baltic marine environment can be found in:
Fourth Periodic Assessment of the State of the Marine Environment of the Baltic Sea, 1994-1998; Executive Summary (2001)
List of 2005 Indicator Fact Sheets | <urn:uuid:7c6ebf00-01dd-49e4-b7ae-1c894499c4ed> | 3.15625 | 1,838 | Structured Data | Science & Tech. | 32.555379 |
slot-missing class object slot-name operation &optional new-value => result*
slot-missing (class t) object slot-name operation &optional new-value
Arguments and Values:
class---the class of object.
slot-name---a symbol (the name of a would-be slot).
operation---one of the symbols setf, slot-boundp, slot-makunbound, or slot-value.
The generic function slot-missing is invoked when an attempt is made to access a slot in an object whose metaclass is standard-class and the slot of the name slot-name is not a name of a slot in that class. The default method signals an error.
The generic function slot-missing is not intended to be called by programmers. Programmers may write methods for it.
The generic function slot-missing may be called during evaluation of slot-value, (setf slot-value), slot-boundp, and slot-makunbound. For each of these operations the corresponding symbol for the operation argument is slot-value, setf, slot-boundp, and slot-makunbound respectively.
The optional new-value argument to slot-missing is used when the operation is attempting to set the value of the slot.
If slot-missing returns, its values will be treated as follows:
Affected By: None.
The default method on slot-missing signals an error of type error.
defclass, slot-exists-p, slot-value
The set of arguments (including the class of the instance) facilitates defining methods on the metaclass for slot-missing. | <urn:uuid:b143a54e-cab0-40a5-9564-dd175c5caccb> | 3.015625 | 348 | Documentation | Software Dev. | 51.614314 |
AN ILLUSION device that makes one object look like another could one day be used to camouflage military planes or create "holes" in solid walls.
The idea builds on the optical properties of so-called metamaterials, which can bend light in almost any direction. In 2006, researchers used this idea to create an "invisibility cloak" that bent microwaves around a central cavity, like water flowing around a stone. Any object in this cavity is effectively invisible.
Now a group of researchers has gone a step further. "Invisibility is just an illusion of free space, of air," says Che Ting Chan, a physicist at the Hong Kong University of Science and Technology and a co-author of the study. "We are extending that concept. We can make it look like not just air but anything we want."
Instead of bending light around a central cavity, the team has worked out ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:1a023e00-0243-4afa-8be5-70df19c7bc36> | 3.4375 | 215 | Truncated | Science & Tech. | 47.467219 |
The Array object is used to store multiple values in a single variable.
Create an array, and assign values to it:
You will find more examples at the bottom of this page.
An array is a special variable, which can hold more than one value at a time.
If you have a list of items (a list of car names, for example), storing the cars in single variables could look like this:
However, what if you want to loop through the cars and find a specific one? And what if you had not 3 cars, but 300?
The solution is an array!
An array can hold many values under a single name, and you can access the values by referring to an index number.
An array can be created in three ways.
The following code creates an Array object called myCars:
You refer to an element in an array by referring to the index number.
This statement access the value of the first element in myCars:
This statement modifies the first element in myCars:
| is the first element in an array. is the second . . . . . (indexes start with 0)|
Because of this, you can have variables of different types in the same Array.
You can have objects in an Array. You can have functions in an Array. You can have arrays in an Array:
The Array object has predefined properties and methods:
For a complete reference of all properties and methods, go to our complete Array object reference.
The reference contains a description (and more examples) of all Array properties and methods.
The example above makes a new array method that transforms array values into upper case.
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|Life depends on an essentially continuous exchange of
mass and energy between living organisms and their environment.
Human impact on this vital exchange has occurred on a global or
macroclimate scale. Understanding the physical principles
involved in heat transfer and absorption in the atmosphere is critical
to understanding how these physical factors affect living
organisms. The specific objectives of this section are to explain
the properties of heat transfer, and to describe laboratory activities
that can be used at a variety of academic levels with only slight
Described below are three series of experiments performed in
the laboratory to address questions that emphasize the underlying
principles of heat transfer. These hands-on experiments focused
on principles that relate to conduction and convection. The object was to identify the method of heat transfer
through solids, liquids, gases, and between boundaries.
Understanding these concepts gave us a better understanding of how heat
is transferred between our environment and living
organisms. These experiments were used as an integral part
of the workshop, which consisted of reflections on redesigning or
modifying lab exercises to fit personal needs of workshop
teachers. These exercises could be adapted for middle
school, high school, and college level courses.
The methods utilized for the three experiments involved increasing
or decreasing the temperature of a solid or liquid, and where
applicable, observing the motion of a dye caused by the changes in
temperature and density of the medium.
|Modes of Heat Transfer:
- Conduction: heat transfer resulting from direct contact
between substances of different temperatures; heat is transferred
from the high-temperature substance to the low by direct molecular
- Convection: heat transport by a moving fluid (gas of
liquid). The heat is first transferred to the fluid by
conduction, but the fluid motion carries the heat away.
- Radiative exchange: heat transfer via electromagnetic
waves, the amount of radiant energy emitted, transmitted, or
(Figure from Microsoft Encarta)
Return to Top
Laboratory Apparatus for Labs 1-3
|Lab 1: Heating
from Below: Convection
In this experiment, water was heated from below to produce
convection. Although the atmosphere is composed of air, this
experiment was relevant to atmospheric motion as well. The lower
atmosphere (troposphere) is mostly heated from below because the
oceans and continents absorb radiation from the sun and then transfer
some of the resulting heat energy to the lower atmosphere.
In Lab 1, a beaker was heated (see figure below). Thermometers were placed in 1/2 cm
below water surface and 1/2 cm above the bottom of the beaker.
The temperature was recorded at 30 second intervals. Drops of
dye were added to the bottom of the beaker between intervals.
After three minutes the beaker was removed from the hot plate and
temperature reading recorded for another five minutes.
Convection was visualized by observing the motion of the
The motion of the dye was circular from bottom to top and returning to
the bottom of the beaker. The energy from heating created a less
dense liquid at the bottom, thus causing the upward motion of the
dye. Upon reaching the surface, the dye was now in the denser
medium and therefore returned to the bottom. This motion is an
example of convection. This phenomenon is evident in the motion
of wind. The difference in densities and kinetic movement of the
water molecules driven by temperature change resulted in the movement of
air molecules. This lab can be used at lower levels to
demonstrate simple properties of heat transfer and convection.
At higher levels, this lab illustrates these basic principles, and
could be extended to address more complex applications related to
convection such as the Coriolis
1. Explain the process by which the water is heated.
2. Describe the motion of the water as made visible by the
3. Why does convection occur?
4. Did convection cease? When? Why?
Environmental Applications of Principles
of Radiative Exchange, Conduction and Convection (Figure from E. Zerba, Princeton University; email@example.com)
Return to Top
|Lab 2: Conduction
Comparison of this experiment with the first illustrated the
difference between the rate of heat transfer by conduction and that of
convection. It also illustrated the difference in heat
capacities between water and the solid materials of the
Lab 2 was configured similarly to Lab 1, but looked at the effect of
heating and cooling temperature difference using sand of equal weight
as water used in experiment 1. No dye was used in this experiment, as convection was not a
The temperature difference between the top and bottom layers of sand
indicated that sand heats and cools at a faster rate compared to
water. When the beaker was removed from the heat, the
temperature continued to increase via conduction from the bottom of the
beaker. This lab exercise is useful for demonstrating the concept of conduction to lower level students. Upper level
students can use this lab to make the connections between conduction and
heat capacity of various substances related to heat transfer that occurs between the
earth's surfaces and the surface of living organisms.
1. Is there any convection in the sand? Explain.
2. Why did the temperature recorded by the lower thermometer
continue to rise dramatically after the heating ceased?
3. On the basis of heat capacity, explain why the temperature
changes for the sand and water were different.
4. Using what you have observed in the two experiments, predict
whether a cold front will lower temperatures more at inland locations
or on the coast. Explain your answer.
Return to Top
|Lab 3: Cooling From Above
In lakes and oceans, convection is generally the result of cooling
from above rather than heating from below. This was demonstrated
by adding ice to the water.
Using an experimental setup that allowed
measurement of temperature at the top and the bottom of a beaker of
water, ice was added to the top of the beaker. This experiment
illustrated the concept that at 4 °C, water
has higher density and sinks. Convection was
visualized by the movement of dye added to the bottom of the beaker
which was displaced by the cooler more dense water.
This lab demonstrates several physical principles associated with heat
transfer, including density, kinetic molecular theory, and
convection. On a larger scale, this laboratory exercise
demonstrates the process by which seasonal turnovers occur in ponds
and lakes. At
lower levels, teachers may choose to discuss physical principles of
heat transfer only, while at upper levels, teachers may choose to
integrate this small-scale investigation with the study of climate
processes and lake nutrient stratification and mixing.
1. Why does ice float?
2. Is there any evidence of convection? Why does or does
it not occur?
3. Draw a diagram to explain how seasonal turnover occurs in a
Return to Top
to The Passerine Birds home | <urn:uuid:77831d47-ed83-47e1-aa8f-16bc431d8619> | 4 | 1,507 | Tutorial | Science & Tech. | 37.059793 |
Introduction to Enzymes
The following has been excerpted from a very popular Worthington publication which was originally published in 1972 as the Manual of Clinical Enzyme Measurements. While some of the presentation may seem somewhat dated, the basic concepts are still helpful for researchers who must use enzymes but who have little background in enzymology.
Enzyme Kinetics: Energy Levels
Chemists have known for almost a century that for most chemical reactions to proceed, some form of energy is needed. They have termed this quantity of energy, "the energy of activation." It is the magnitude of the activation energy which determines just how fast the reaction will proceed. It is believed that enzymes lower the activation energy for the reaction they are catalyzing. Figure 3 illustrates this concept.
The enzyme is thought to reduce the "path" of the reaction. This shortened path would require less energy for each molecule of substrate converted to product. Given a total amount of available energy, more molecules of substrate would be converted when the enzyme is present (the shortened "path") than when it is absent. Hence, the reaction is said to go faster in a given period of time. | <urn:uuid:cb68bdbc-cf40-4d1b-ba86-741aa42fc245> | 4.09375 | 234 | Tutorial | Science & Tech. | 32.380483 |
In Journey into the Cell, we looked at the structure of the two major types of cells: prokaryotic and eukaryotic cells. Now we turn our attention to the "power houses" of a eukaryotic cell, the mitochondria.
Mitochondria are the cell's power producers. They convert energy into forms that are usable by the cell. Located in the cytoplasm, they are the sites of cellular respiration which ultimately generates fuel for the cell's activities. Mitochondria are also involved in other cell processes such as cell division and growth, as well as cell death.
Mitochondria: Distinguishing Characteristics
Mitochondria are bounded by a double membrane. Each of these membranes is a phospholipid bilayer with embedded proteins. The outermost membrane is smooth while the inner membrane has many folds. These folds are called cristae. The folds enhance the "productivity" of cellular respiration by increasing the available surface area.
The double membranes divide the mitochondrion into two distinct parts: the intermembrane space and the mitochondrial matrix. The intermembrane space is the narrow part between the two membranes while the mitochondrial matrix is the part enclosed by the innermost membrane. Several of the steps in cellular respiration occur in the matrix due to its high concentration of enzymes.
Mitochondria are semi-autonomous in that they are only partially dependent on the cell to replicate and grow. They have their own DNA, ribosomes and can make their own proteins. Similar to bacteria, mitochondria have circular DNA and replicate by a reproductive process called fission.
Journey into the Cell:
To learn more about cells, visit: | <urn:uuid:725b19ff-601b-4c5b-9e4d-2293b902f895> | 4.0625 | 351 | Knowledge Article | Science & Tech. | 31.740185 |
- About Us
- SW Climate
February 2012 La Niña Drought Tracker
February 08, 2012 / Vol. 2 / Issue 3 / Drought Tracker / A Publication by CLIMAS
After a wet December, more typical, dry La Niña conditions returned in January. Across Arizona and New Mexico precipitation generally was less than 50 percent of average, with large swaths of both states experiencing less than 25 percent of average (top figure). Most of the West also experienced scant rain and snow, including the mountains of the Upper Colorado River Basin, where about 70 percent of the water in the Colorado River originates. In many La Niña winters, the impacts of dry conditions are minimized by average or above-average snow in these mountains, which was the case last winter. This year, however, storms have been pushed farther north than typical by a dome of high-pressure off the northwestern coast. The Pacific Northwest, for example, which typically bares the brunt of winter storms during La Niña, was exceptionally dry for most of December and January.
Warm conditions also accompanied January’s scarce precipitation. January temperatures were between 2 and 6 degrees F above average (Supplemental Figure 1), which helped drive a precipitous decline in mountain snow. Most of the country also experienced unseasonably mild temperatures, and many scientists point to the Arctic Oscillation (AO) as part of the cause. The AO describes changes in surface pressure in and around the Arctic (Supplemental Figure 2) that intensify or slacken the winds circulating the polar regions. In the positive phase of the AO, fierce winds prevent the frigid air from flowing south, while the reverse occurs during the negative phase. Up until mid-January this winter, the AO was positive (Supplemental Figure 3). Historically, the confluence of a positive AO and La Niña tends to bring warmer conditions to the Southwest (Supplemental Figure 4), jiving with temperatures in the region in the past month. The AO recently switched to negative and may help bring colder conditions in coming weeks; the AO was negative during February 2011, when several cold snaps froze the region.
Drought conditions are still widespread and extend into Mexico (Supplement Figure 5). The soggy December spurred only minimal drought improvements because wet conditions did not persist. With a recent return of dry weather, moderate drought expanded in Arizona by about 13 percent since January 3, most notably in central Arizona (bottom figure). Abnormally dry conditions or a more severe drought category currently cover more than 92 percent of both Arizona and New Mexico. Forecasts also suggest La Niña will continue through the February–April period (Supplemental Figure 6), likely bringing more dry weather.
Source: National Resources Conservation Service
- The amount of water contained in the snowpack, or snow water equivalent (SWE), was largely below average in Arizona and New Mexico on February 6 (left); SWE in southern mountains dropped by more than 50 percent from one month ago.
- Winter storms were few and far between in the Upper Colorado and Rio Grande basins in January. As of February 8, SWE in these basins were reporting less than 80 percent of average (Supplemental Figure 7).
- Early streamflow forecasts suggest only a 50 percent chance that the April–June flow into Lake Powell will be above 64 percent of average (Supplemental Figure 8); streamflow forecasts progressively become more accurate as the winter advances.
- The precipitation outlook for February–April calls for increased chances for below-average precipitation in all of Arizona and New Mexico (right). Odds for below-average precipitation are 50–60 percent in the southern tier of Arizona and New Mexico (right). There is greater than a 40 percent chance for below-average precipitation in all of Arizona and New Mexico for the February–April period.
- The February–April outlook calls for increased odds of above-average temperature in all of Arizona and New Mexico; odds for above-average temperatures are greater than 40 percent in all of New Mexico and in eastern Arizona (Supplemental Figure 9).
La Niña conditions were present 16 times between 1950 and 2008. In this period, precipitation during the February–April period was often 0.2–2.7 inches below average in most of Arizona and northern New Mexico; central Arizona experienced the most precipitation deficits (Supplemental Figure 10). Two inches is about 25 percent of the total winter precipitation in many areas.
- The Seasonal Drought Outlook calls for drought to persist or intensify in all of the Southwest during the February–April period (Supplemental Figure 11). This forecast is influenced by expectations for below-average precipitation and the continuation of La Niña.
- A looping jet stream, which often accompanies La Niña events, combined with a negative Arctic Oscillation that allows cold polar air to waft south, could begin to ferry colder air into the region in coming weeks.
- While it is too early to reliably forecast the 2011–2012 winter, it is worth noting that there have been 10 back-to-back La Niña events since 1900. In four of those cases, a La Nina developed for a third consecutive winter, while an El Niño developed in the third winter in the other six cases. ENSO-neutral conditions have never followed a two-year La Niña.
- This winter has evolved similarly to the last, as a dry January followed a wet December. However, this January delivered dry conditions to the Upper Colorado and Rio Grande basins (Supplemental Figure 12), which was not the case last winter.
- Spring streamflow forecasts in Arizona call for high probabilities for below-average flows in all river basins. In New Mexico, flow in the Rio Grande measured at Otowi Bridge has a 30–50 percent chance of being above average; most other basins have lower odds for above-average flows. | <urn:uuid:4d01727a-1f35-48cc-bf09-97d8ab052898> | 2.84375 | 1,202 | Knowledge Article | Science & Tech. | 30.820836 |
Date of this Version
Nebraska Public Power District (NPPD) has monitored water quality since 1989 and fish populations since 1993 on the Niobrara River in Nebraska in the vicinity of Spencer Hydro during "flushing" or "sluicing" activities. These sluicing activities alter water quality in the river downstream, which can negatively impact fish populations. Higher numbers offish were sampled in 1995 when compared to 1993 and 1994. Of the 6,187 fish and 22 total species sampled above and below the hydro, six species comprised approximately 93 percent of the total sample. The most common species sampled were sand shiner, Notropis ludibundus (35.4%), red shiner, Cyprinella lutrensis (22.9%), flathead chub, Hybopsis gracilis (14.4%), carpsucker spp., Carpoides sp. (10.9%), bigmouth shiner, Hybopsis dorsalis (5.1%), and channel catfish, lctalurus punctatus (4.0%). Operational modifications instituted since 1989, such as opening the flood gates slower and dropping the pond at a slower rate, have reduced sluicing impacts and the hydro structure may not be limiting species diversity to the extent originally thought. | <urn:uuid:942a696e-3c5f-47bb-a446-1ed17907725a> | 3.421875 | 265 | Knowledge Article | Science & Tech. | 47.09828 |
A bag contains n discs, made up of red and blue colours. Two discs are removed from the bag.
If the probability of selecting two discs of the same colour is 1/2, what can you say about the number of discs in the bag?
Let there be r red discs, so P(RB) = r/n (nr)/(n1), similarly,
P(BR) = (nr)/n r/(n1).
Therefore, P(different) = 2r(nr)/(n(n1)) = 1/2.
Giving the quadratic, 4r2 4nr + n2 n = 0.
Solving, r = (nn)/2.
If n is an odd square, n will be odd, and similarly, when n is an even square, n will be even. Hence their sum/difference will be even, and divisible by 2.
In other words, n being a perfect square is both a sufficient and necessary condition for r to be integer and the probability of the discs being the same colour to be 1/2.
Prove that n(n+1)/2 (a triangle number), must be square, for the probability of the discs being the same colour to be 3/4, and find the smallest n for which this is true.
What does this tell us about n and n(n+1)/2 both being square?
Can you prove this result directly? | <urn:uuid:c329b7b4-cde7-4cf9-96f3-2a0ef6253d5c> | 2.9375 | 304 | Q&A Forum | Science & Tech. | 94.961703 |
June 22, 1976. North Atlantic. At 21:13 GMT a pale orange glow behind a bank of towering cumulus to the west was observed. Two minutes later a white disc was observed while the glow from behind the cloud persisted.
High probability that this may have been caused by interferometry using 3-dimensional artificial scalar wave? Fourier expansions? as the interferers.
Marine Observer. 47(256), Apr. 1977. p. 66-68.
"Unidentified phenomenon, off Barbados, West Indies."
August 22, 1969. West Indies. Luminous area bearing 310 degrees grew in size and rose in altitude, then turned into an arch or crescent.
High probability that this may have been caused by interferometry using artificial scalar wave? ((Fourier expansions.))
Marine Observer. 40(229), July, 1970. p. 107-108.
"Optical phenomenon: Caribbean Sea; Western North Atlantic."
Mar. 20, 1969. Caribbean Sea and Western North Atlantic. At 23:15 GMT, a semicircle of bright, milky-white light became visible in the western sky and rapidly expanded upward and outward during the next 10 minutes, dimming as it expanded.
High probability that this may be caused by interferometry using artificial scalar wave? Fourier expansions?.
Marine Observer, 40(227), Jan. 1970. p.17; p. 17-18.
7B.21 - Electricity
13.06 - Triple Currents of Electricity
14.35 - Teslas 3 6 and 9
((16.04 - Nikola Nikola Tesla describing what electricity is))
16.07 - Electricity is a Polar Exchange
16.10 - Positive Electricity
16.16 - Negative Electricity - Russell
16.17 - Negative Electricity - Tesla
16.29 - Triple Currents of Electricity
((Figure 16.04.05 and Figure 16.04.06 - Nikola Nikola Tesla and Lord Kelvin))
Part 16 - Electricity and Magnetism
Tesla - Electricity from Space
What Electricity Is - Bloomfield Moore
Page last modified on Wednesday 19 of May, 2010 05:23:05 MDT | <urn:uuid:5ff0ec8a-893b-4fc8-b51a-53a907c3402b> | 2.921875 | 452 | Knowledge Article | Science & Tech. | 62.622889 |
Herschel Space Observatory
Launch Date: May 14, 2009
Mission Project Home Page - http://herschel.jpl.nasa.gov/
Herschel's infrared image of the Andromeda Galaxy shows rings of dust that trace gaseous reservoirs where new stars are forming and XMM-Newton's X-ray image shows stars approaching the ends of their lives. Both infrared and X-ray images convey information impossible to collect from the ground because these wavelengths are absorbed by Earth's atmosphere. Credits: ESA/Herschel/PACS/SPIRE/J.Fritz, U.Gent/XMM-Newton/EPIC/W. Pietsch, MPE
The Herschel Space Observatory is a space-based telescope that is studying the light of the Universe in the far-infrared and submillimeter portions of the spectrum. It is revealing new information about the earliest, most distant stars and galaxies, as well as those closer to home in space and time. It is also taking a unique look at our own Solar System.
Herschel is the fourth Cornerstone mission in the European Space Agency’s Horizon 2000 program. Ten countries, including the United States, participated in its design and implementation. Launched on May 14, 2009, the mission will operate until the cryostat runs out of helium during the first half of 2013. The mission will operate until the cryostat runs out of helium, perhaps four years after launch. Originally called “FIRST,” for “Far InfraRed and Submillimeter Telescope,” the spacecraft was renamed for Britain’s Sir William Herschel, who discovered in 1800 that the spectrum extends beyond visible light into the region we today call “infrared.”
Herschel’s namesake will give scientists their most complete look so far at the large portion of the Universe that radiates in far-infrared and submillimeter wavelengths. With a primary mirror 3.5 meters (approximately 11.5 feet) in diameter, Herschel is the largest infrared telescope sent into space as of its launch date. Using detectors cooled to temperatures very close to absolute zero (0 degree Kelvin), the three instruments called HIFI, SPIRE, and PACS, which enables Herschel to be the first spacecraft to observe in the full 60-670 micron range.
The far-infrared and submillimeter wavelengths at which Herschel observes are considerably longer than the familiar rainbow of colors that the human eye can perceive. Yet, this is a critically important portion of the spectrum to scientists because it is the frequency range at which a large part of the universe radiates.
Much of the Universe consists of gas and dust that is far too cold to radiate in visible light or at shorter wavelengths such as x-rays. However, even at temperatures well below the most frigid spot on Earth, they do radiate at far-infrared and submillimeter wavelengths.
Stars and other cosmic objects that are hot enough to shine at optical wavelengths are often hidden behind vast dust clouds that absorb the visible light and re-radiate it in the far-infrared and submillimeter range.
Last updated: October 26, 2012
- ESA Herschel Website - http://www.esa.int/SPECIALS/Herschel/index.html
- More about Herschel - http://www.nasa.gov/mission_pages/herschel/index.html
- Science@ESA - ISO/Herschel video - http://astronomy2009.esa.int/science-e/www/object/index.cfm?fobjectid=44698&fattributeid=885 | <urn:uuid:1ce46b18-ab5f-48ab-aacd-8ef745e71dd4> | 3.671875 | 768 | Knowledge Article | Science & Tech. | 50.385784 |
Science Fair Project Encyclopedia
Knot theory is a branch of topology that was inspired by observations, as the name suggests, of knots. But progress in the field no longer depends on experiments with twine. Knot theory concerns itself with abstract properties of theoretical knots — the spatial arrangements that in principle could be assumed by a loop of string.
In mathematical jargon, knots are embeddings of the closed circle in three-dimensional space. An ordinary knot is converted to a mathematical knot by splicing its ends together. The topological theory of knots asks whether two such knots can be rearranged to match, without opening the splice. The question of untying an ordinary knot has to do with unwedging tangles of rope pulled tight. A knot can be untied in the topological theory of knots if and only if it is equivalent to the unknot, a circle in 3-space.
Knot theory originated in an idea of Lord Kelvin's (1867), that atoms were knots of swirling vortices in the æther (also known as 'ether'). He believed that an understanding and classification of all possible knots would explain why atoms absorb and emit light at only the discrete wavelengths that they do (i.e. explain what we now understand to depend on quantum energy levels). Scottish physicist Peter Tait spent many years listing unique knots under the belief that he was creating a table of elements. When ether was discredited through the Michelson-Morley experiment, vortex theory became completely obsolete, and knot theory fell out of scientific interest. Only in the past 100 years, with the rise of topology, have knots become a popular field of study. Today, knot theory is inextricably linked to particle physics, DNA replication and recombination, and to areas of statistical mechanics.
An introduction to knot theory
Creating a knot is easy. Begin with a one-dimensional line segment, wrap it around itself arbitrarily, and then fuse its two free ends together to form a closed loop. One of the biggest unresolved problems in knot theory is to describe the different ways in which this may be done, or conversely to decide whether two such embeddings are different or the same.
The unknot, and a knot
equivalent to it
Before we can do this, we must decide what it means for embeddings to be "the same". We consider two embeddings of a loop to be the same if we can get from one to the other by a series of slides and distortions of the string which do not tear it, and do not pass one segment of string through another. If no such sequence of moves exists, the embeddings are different knots.
A useful way to visualise knots and the allowed moves on them is to project the knot onto a plane - think of the knot casting a shadow on the wall. Now we can draw and manipulate pictures, instead of having to think in 3D. However, there is one more thing we must do - at each crossing we must indicate which section is "over" and which is "under". This is to prevent us from pushing one piece of string through another, which is against the rules. To avoid ambiguity, we must avoid having three arcs cross at the same crossing and also having two arcs meet without actually crossing (we would say that the knot is in general position with respect to the plane). Fortunately a small perturbation in either the original knot or the position of the plane is all that is needed to ensure this.
In 1927, working with this diagrammatic form of knots, J.W. Alexander and G.B. Briggs , and independently Kurt Reidemeister, demonstrated that two knot diagrams belonging to the same knot can be related by a sequence of three kinds of moves on the diagram, shown right. These operations, now called the Reidemeister moves, are:
- Twist and untwist in either direction.
- Move one loop completely over another.
- Move a string completely over or under a crossing.
Knot invariants can be defined by demonstrating a property of a knot diagram which is not changed when we apply any of the Reidemeister moves. Some very important invariants can be defined in this way, including the Jones polynomial.
You can unknot any circle in four dimensions. There are two steps to this. First, "push" the circle into a 3-dimensional subspace. This is the hard, technical part which we will skip. Now imagine temperature to be a fourth dimension to the 3-dimensional space. Then you could make one section of a line cross through the other by simply warming it with your fingers.
Two knots can be added by breaking the circles and connecting the pairs of ends. Knots in 3-space form a commutative monoid with prime factorization. The trefoil knots are the simplest prime knots. Higher dimensional knots can be added by splicing the spheres. While you cannot form the unknot in three dimensions by adding two non-trivial knots, you can in higher dimensions.
- The Knot Book: An Elementary Introduction to the Mathematical Theory of Knots, Colin Adams , 2001, ISBN 0716742195
- Knots: Mathematics With a Twist, Alexei Sossinsky , 2002, ISBN 0674009444
- Knot Theory, Vassily Manturov , 2004, ISBN 0415310016
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:5224c8e3-2023-4490-bcb0-4fefe395a832> | 4.03125 | 1,141 | Knowledge Article | Science & Tech. | 51.304251 |
colorful images are of thin slices of meteorites viewed through a
Part of the group classified as HED meteorites
for their mineral content (Howardite, Eucrite, Diogenite), they likely
to Earth from 4 Vesta,
the mainbelt asteroid currently being explored by NASA's
Why are they thought to be from Vesta?
Because the HED meteorites have visible and infrared spectra
that match the spectrum of
The hypothesis of their origin on Vesta
is also consistent with data from
Dawn's ongoing observations.
by impacts, the diogenites shown here
would have originated deep within the crust of Vesta.
are also found in the lower crust of planet Earth.
A sample scale is indicated by the white bars,
each 2 millimeters long.
Hap McSween (Univ. Tennessee),
A. Beck and T. McCoy (Smithsonian Inst.) | <urn:uuid:ebe51457-c1d9-4dd2-ae15-e45a12f08e6c> | 3.359375 | 192 | Knowledge Article | Science & Tech. | 49.004658 |
The recognized authority for satellite observations of Amazon deforestation is the Brazilian Space Research Institute (Portuguese acronym, INPE). This organization has been monitoring Amazon deforestation since 1988. Currently, INPE publishes monthly reports (for example, see the August 2009 [PDF] report in Portuguese) describing the latest satellite data and deforestation rates estimated from them. The area shown here is in the southern part of Mato Grosso, which had the highest deforestation rate among all Brazilian states between 2001 and 2005 (and subsequently surpassed by Pará state [PDF]). The images come from INPE, but were provided to Climate Central by Dr. Ruth DeFries (Columbia University) and Dr. Douglas Morton (University of Maryland).
Close to 20% of total human-caused emissions of carbon dioxide come from deforestation. Trees, other vegetation and soil return carbon to the atmosphere when forests are cut or burned down. There are many causes of deforestation. Analysis by Tim Searchinger and colleagues found that biofuels crop production in countries like the U.S. may be one contributing factor because of pressure it may generate to increase the amount of land cultivated for food production abroad. | <urn:uuid:285048c7-93aa-4420-917d-d409dcd86a84> | 3.5625 | 233 | Knowledge Article | Science & Tech. | 26.751402 |
ICMAKE Part 2
Icmake source files are written according to a well-defined syntax, closely resembling the syntax of the C programming language. This is no coincidence. Since the C programming language is so central in the Unix operating system, we assumed that many people using the Unix operating system are familiar with this language. Providing a new tool which is founded on this familiar programming language relieves everybody of the burden of learning yet another dialect, thus simplifying the use of the new system and allowing its new users to concentrate on its possibilities rather than on its grammatical form.
Considering icmake's specific function, we have incorporated a lot of familiar constructs from C into icmake: most C operators were implemented in icmake, as were some of the standard C runtime functions. In this respect icmake's grammar is a subset of the C programming language. However, we have taken the liberty of defining two datatypes not normally found in C. There is a datatype `string' (yes, its variables contain strings) and a datatype `list', containing lists of strings. We believe these extensions to the C programming language are so minor that just this paragraph would probably suffice for their definition. However, they will be described in somewhat greater detail in the following sections. Also, some elements of C++ are found in icmake's grammar: some icmake-functions have been overloaded; they do different but comparable tasks depending on the types of arguments they are called with. Again, we believe this to be a minor departure from the `pure C' grammar, and think this practice is very much in line with C++'s philosophy.
One of the tasks of the preprocessor is to strip the makefile of comment. Icmake recognizes two types of comment: standard C-like comment and end-of-line comment, which is also recognized by the Gnu C compiler and by Microsoft's C compiler.
Standard comment must be preceded by /* and must be closed by */. This type of comment may stretch over more than one line. End-of-line comment is preceded by // and ends when a new line starts.
Lines which start with #! are skipped by the preprocessor. This feature is included to allow the use of executable makefiles. Apart from the #! directive, icmake recognizes two more preprocessor directives: #include and #define. All preprocessor directives start with a `#'-character which must be located at the first column of a line in the makefile.
The #include directive must obey the following syntax:
When the preprocessor icm-pp encounters this directive, `filename' is read. The filename may include a path specification. When the filename is surrounded by double quotes, icm-pp attempts to access this file exactly as stated. When the filename is enclosed by < and >, icm-pp attempts to access this file relative to the directory pointed to by the environment variable IM. Using the #include directive, large icmake scripts may be modularized, or a set of standard icmake source scripts may be used to realize a particular icmake script.
The #define directive is a means of incorporating constants in a makefile. The directive follows the following syntax:
#define identifier redefinition-of-identifier
The defined name (the name of the defined constant) must be an identifier according to the C programming language: the first character must be an underscore or a character of the alphabet; subsequent characters may be underscores or alphanumerics.
The redefinition part of the #define directive consists of spaces, numbers, or whatever is appropriate. The preprocessor simply replaces all occurrences of the defined constant following the #define directive by the redefinition part. Note that redefinition's are not further expanded; an already defined name which occurs in the redefinition part is not processed but is left as-is.
Also note that icm-pp considers the redefinition part to be all characters found on a line beyond the defined constant. This would also include comment, if found on the line. Consequently, it is normally not a good idea to use comment-to-end-of-line on lines containing #define directives.
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Free Webinar: Hadoop
How to Build an Optimal Hadoop Cluster to Store and Maintain Unlimited Amounts of Data Using Microservers
Realizing the promise of Apache® Hadoop® requires the effective deployment of compute, memory, storage and networking to achieve optimal results. With its flexibility and multitude of options, it is easy to over or under provision the server infrastructure, resulting in poor performance and high TCO. Join us for an in depth, technical discussion with industry experts from leading Hadoop and server companies who will provide insights into the key considerations for designing and deploying an optimal Hadoop cluster.
Some of key questions to be discussed are:
- What is the “typical” Hadoop cluster and what should be installed on the different machine types?
- Why should you consider the typical workload patterns when making your hardware decisions?
- Are all microservers created equal for Hadoop deployments?
- How do I plan for expansion if I require more compute, memory, storage or networking? | <urn:uuid:031f7ec1-ba10-4fc6-af49-782fc65e4df5> | 3.109375 | 1,292 | Documentation | Software Dev. | 31.781229 |
When you have 400 earthquakes on top of one of the largest supervolcanoes on Earth, people pay attention.
And since the day after Christmas, that's what has happened at Yellowstone National Park. Scientists are seeing what they call a "swarm" of low intensity earthquakes -- the largest since the 1980s. The biggest quake had a magnitude of 3.9, below the level that can cause damage.
But the earthquakes have made worldwide news because the park lies on a giant caldera, the crater of a volcano that scientists say could one day explode and destroy most of North America and freeze the rest of the world under a shroud of ash for up to two years. Still, the latest earthquakes are nothing to fear, said park geologist Hank Heasler.
Read the full story at idahostatesman.com. | <urn:uuid:47cbb496-cca8-47cb-8acd-5f6b47f47afd> | 2.9375 | 171 | Truncated | Science & Tech. | 61.486928 |
WHILE telling the world that they have stopped producing plutonium for nuclear weapons, Britain and the US are planning to carry on making tritium for H-bombs. The US government is proposing to bring a major new tritium production plant into operation by 2010, while British Nuclear Fuels (BNFL) is continuing to manufacture tritium for Trident missiles at the Chapelcross nuclear plant in Scotland.
During the 178-nation conference on the Nuclear Non-Proliferation Treaty (NPT), which finished in New York last week, the US and Britain were criticised by non-nuclear weapons states for failing to make enough progress towards nuclear disarmament. In response, both the US Vice-President Al Gore and the British Foreign Secretary Douglas Hurd stressed that they had stopped producing plutonium for weapons. But they failed to explain that this was because they have large plutonium stockpiles. Nor did they mention their plans for tritium production.
Tritium is a naturally ...
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Inside RelativeLayoutby James Elliott, coauthor of Java Swing, 2nd Edition
As promised in my first article, "RelativeLayout: A Constraint-Based Layout Manager," here's a look inside the
RelativeLayout package. This article explains how the layout manager works, and discusses how to extend it to support new kinds of constraints. Readers should be familiar with the original article, which introduces
RelativeLayout and explains how to use it as a tool.
Once you download and expand the source archive, you'll find the following items inside of it (Figure 1 shows everything it will contain once you're ready to build and run
Figure 1: RelativeLayout Source
This is a build file for the Ant tool from Apache's Jakarta project. It is used to compile and test
RelativeLayout. Once you have installed Ant on your system (which you have likely done already, since it has rapidly and deservedly become the build tool of choice for Java projects) you can compile
RelativeLayout simply by moving to the top-level source directory and typing
ant compile (after you've set up the
lib directory as described below).
Other interesting build targets you can run include:
ant ex1: runs the first example program discussed in the first article. Similarly, the targets
ex3run the second and third examples.
ant doc: builds the JavaDoc for
RelativeLayout. You may want to refer to this documentation from time to time as you read the overview of how the classes work, below.
ant dist: builds the distribution file
RelativeLayout.jarso you can easily use
RelativeLayoutwith other projects.
ant clean: cleans up any generated files and removes the
These files are used by the XML-based examples in the first article. They contain the layout constraints used by the second and third example programs.
Contains libraries used by
RelativeLayout. It's empty when you first download and expand the source archive, because these libraries are available from separate organizations. In order to compile and use
RelativeLayout, you'll need the JDOM library and (if you're using a Java SDK earlier than version 1.4) an XML parser such as Apache Xerces, as discussed in the first article. Once you've downloaded any libraries you need (which you likely did in order to run the examples when reading Part 1), copy their library jars (e.g.
xerces.jar) into the
lib directory, and
RelativeLayout will compile and run properly.
I used this file along with a test program while I was developing
RelativeLayout. It's not too useful now, unless you want to study and play with that test program. Note that the current configuration of the program (invoked through
ant test) and this file are inconsistent and cause an over-constraint error to be reported. If you're into that sort of thing, debugging and fixing the problem could be an interesting exercise.
The rest of the source is organized under the
src directory, so let's move in there and see what we find.
- The files
These are the three example programs discussed in Part 1.
This is the test program that works with
test.xmlas described above. It's no longer of much interest except for software archaeology, in that it provides a little insight into the development of the package.
This package overview document is used by JavaDoc to provide introductory information on the starting page.
The Java source for
RelativeLayoutitself is grouped under this directory. To be precise, it's in the nested directory src/com/brunchboy/util/swing/relativelayout, corresponding to the package in which the classes themselves are organized,
com.brunchboy.util.swing.relativelayout. The classes that make up
RelativeLayoutare explained in the next few sections. You'll best understand how everything works if you can examine the source itself while you read the descriptions below, perhaps by printing one or the other.
relativelayoutdirectory also contains the file
package.html, used by JavaDoc to provide an introductory explanation for the classes in the directory, and
constraint-set.dtd, the XML document type definition (described below), used by
XmlConstraintBuilderto parse constraint specifications expressed as XML. | <urn:uuid:1b0ddc5f-b616-4f83-9c81-b11dbb31528f> | 2.890625 | 901 | Documentation | Software Dev. | 42.500558 |
Heat loss and hydrothermal ciruculation due to sea-floor spreading.
Abstract (Summary)Lithospheric cooling along the Galapagos Spreading Center at 86°W longitude, as determined by surface heat-flow measurements, appears dominated by hydrothermal circulation. This same phenomena apparently exists on the Mid-Atlantic Ridge at 36°N and presumably, in some form on all active oceanic ridges. It is responsible for removing the majority of the heat () 80%) lost through young (few m.y. old) oceanic crust. This component of heat has been ignored in previous calculations of the total rate of heat loss by the Earth. A theoretical expression is used to estimate the heat released by sea-floor spreading, since current technology does not provide any means for direct measurement. The revised va lue of lO. 2 x iOl2 cal/sec (il5%) represents a 32% increase over previous estimates. More than 20% of this heat apparently escapes through hydrothermal vents near sea-floor spreading centers. The previously accepted equality of oceanic and continental heat flux is invalid. The revised analysis indicates the oceanic heat flux is 2.2 x iO-6 cal/cm2-sec (HFU) versus l.5 HFU for the continents . The average for the Earth is then approximately 2.0 HFU. The horizontal wavelength of inferred hydrothermal convection at the Galapagos Spreading Center, in the one dimension measured, is 6 il km. The systematic modulation suggests cellular convection. If the system is dominated by cellular convection, the depth of penetration, based on laboratory modeling experiments should be 3 to 4 kilometers. -3- The data from the Galapagos Spreading Center and laboratory experiments both suggest that the position of the cells in a cellular convection system can be a strong function of the local topography, the rising limbs of flow being located beneath topographic highs and the descending limbs beneath topographic lows. The addition of topography enhances the heat transfer efficiency of a convection system. Lateral variation in permeability or the systems bottom boundary condition will also influence the position of cells. Even if the circulation system were strongly influenced by some combination of variations in the strength of the heat source, topography or discrete zones of high permeability, it would probably still be cellular in nature, and similar deep penetration is indicated. If the Galapagos Spreading Center is typical, there are presumably numerous hydrothermal springs and fissures in each square kilometer of near-ridge sea floor and sediment thicknesses of at least 50 meters are apparently penetrable to the flow of water. As the sea floor ages the surface of the hydrothermal system becomes less permeable and eventually both the surface and the deep system are completely clogged and sealed. The age at which this occurs varies from ridge to ridge but there is evidence that suggests it may not be complete until the crust is at least 8 m.y. old and possibly as much as 40-50 m.y. old. Most of the surface is apparently sealed long before hydrothermal circulation stops, although some vents do persist. This behavior of the hydrothermal system has a dramatic effect on conductive heat-flow measurements and is largely responsiBTe--fbr Ene variations observed in conductive heat flow near active spreading ridges. The results of this study show the difficulties in resolving systematic patterns in the heat-flow distribution on spreading ridges. Numerous, closely-spaced measurements with precise navigation combined with a relatively uniform sediment cover, appear to be necessary ingredients for recognition of the heat-flow pattern near active sea-floor spreading centers. Thesis Supervisor: Dr. Richard P. Von Herzen Ti tle: Senior Scientist -4-
School Location:USA - Massachusetts
Source Type:Master's Thesis
Date of Publication: | <urn:uuid:6b27fe4e-b678-4b8b-965f-6d6a0bdfc6c7> | 3.203125 | 793 | Academic Writing | Science & Tech. | 36.658399 |
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Convert String into date
In this example we are going to convert String into date. SimpleDateFormat is a concrete class for formatting the dates which is inside package "java.text.*" which have a date format which convert a string into Date format.. | <urn:uuid:616e711f-c1f6-4ca6-a0db-cef4720f6309> | 3.578125 | 1,670 | Content Listing | Software Dev. | 49.885241 |
1. Fifty years of manned spaceflight. April marked the 50th anniversary of the first manned spaceflight by Yuri Gagarin aboard Vostok 1 in 1961. Russia continued regular launches with its Soyuz becoming the only way too carry astronauts to the International Space Station (ISS) and making their first unmanned launches from Europe's spaceport at French Guyana. But the crash of a Progress cargo ship in August led to questions of relying too much on Russia. In February, the European Space Agency (ESA) successfully launched its second unmanned Automated Transfer Vehicle (ATV) Johannes Kepler to the ISS.
2. End of the road for the Space Shuttle. Atlantis touched down in July, marking the final spaceflight and the end of the Space Shuttle programme. It also meant that construction of the ISS was essentially complete. Meanwhile, as NASA's own manned space launches appeared to be temporarily abandoned, China's began to accelerate, including the launch of its own first space station module, Tiangong-1, in September.
3. Big strides by commercial space companies. The growing interest in the US and beyond to turn space exploration over to private enterprise got a boost in April when NASA awarded $269 million to companies including SpaceX, Sierra Nevada, Boeing and Blue Origin. Meanwhile, seven years after the first successful suborbital flights by prototype SpaceShipOne, Virgin Galactic is steadily preparing to carry its first paying tourists to the edge of space.
4. New missions to deep space. NASA continued to pioneer exploration of the Solar System. Probes were launched both to Jupiter in August (Juno) and Mars in November (Mars Science Laboratory, or Curiosity). In March, their Messenger probe went into orbit around Mercury, and in July, Dawn began circling the asteroid Vesta. Twin Grail probes to investigate the interior of the Moon are arriving this weekend following a September launch. Russia's bid to fly to Mars failed when its Phobos-Grunt craft became stranded in Earth orbit.
5. Advances in astronomy. The number of planets discovered around other stars climbed above 700 as the year drew to a close including the first two Earth-sized worlds discovered by NASA's Kepler space mission and others found in the so-called habitable zones of their host suns. Another boost for astronomy came with fresh support for the successor to Hubble, the James Webb Space Telescope after a battle in Congress over its budget. In other astronomical news, the Sun roared back into activity with many sunspots and eruptions plus the closest flypast by a giant asteroid ever witnessed was watched in November when 2005 YU55 came well inside the orbit of the Moon. | <urn:uuid:fafccad4-c02d-483d-9fe6-c5e4a5a6007f> | 3.28125 | 534 | Listicle | Science & Tech. | 45.12835 |
There’s a third more carbon dioxide in the air than at the start of the Industrial Revolution. The carbon acts like insulation in the atmosphere, or like glass in a greenhouse — that’s why it’s called a greenhouse gas – and it is warming the air, which warms the seas.
The current carbon dioxide concentration is higher than it has been for several million years and rising 100 times faster than any time in the past 650,000 years. Warmer ocean water is already having dramatic effects.
Some corals bleach and die when water gets too warm for too long. Bleaching means corals eject algae cells that live inside them and provide them with food and often color.
What happens to reefs will affect the hundreds of millions of people worldwide who depend on reefs for food and income.
Ocean warming and higher air temperatures also melt polar ice. As polar ice melts, animals that need ice suffer. Polar bears, some seals and many penguins require ice to live. At the base of the Antarctic food web, shrimp-like krill require ice and they are vital food sources for many Antarctic whales, seals, seabirds, and fishes.
Melting land-ice, such as glaciers, raises sea levels. (Sea ice is already displacing all the water it will displace, and like ice cubes in a drink, sea ice does not raise sea level when it melts.) Meanwhile, as seawater warms it expands a little, also raising sea levels.
Global sea level rise threatens coastal habitat–both marine environments and human settlements. Because such a large proportion of people live within 50 miles of a coast, it’s estimated that over 600 million people—roughly one in ten people on Earth, will be directly affected by sea level rise.
Entire island nations in the South Pacific may disappear beneath the waves as the ocean envelops them. Rising sea levels threaten habitats such as coral reefs and coastal mangroves, as well as low islands relied upon by many millions of breeding seabirds.
The solution: We need an energy economy based on renewable energy, especially energy sources that do not have to be burned, such as the power of the sun, wind, tides, and the heat of the Earth—the power that drives the whole planet.
3 things you can do to curb ocean warming:
1. Conserve energy at home and at work.
2. Switch to renewable energy whenever possible.
3. Change your driving habits to conserve fuel – walk, ride a bike or carpool.
Other great ways you can make a difference.
LINKS & VIDEOS
Warming 101 – Carl’s Blog
Baked Alaska – Carl’s Blog
Global Warming – National Wildlife Foundation
Coral Reef Bleaching Affects Fish Communities – Science Daily
Coral Reef Bleaching Impacts – Coral Reef Resilience
Global Climate Change & Krill – Antarctic Krill Conservation Project
Polar Bear Habitat
2010 Warmest Year on Record – USA Today
Aquarius Ocean Circulation, NASA
Until now, researchers did not have a full set of data on ocean salinity and how it impacts climate change.
Climate Change Affects Everything, State of the World’s Oceans
Climate change affects everything. All the organisms that live in the ocean are used to being bathed in it, are used to its temperature, are used to where the ocean currents flow and all those things change with global climate change.
Coral Bleaching Firsthand, Penn State Research
Iliana Baums, an assistant professor of biology at Penn State, dons scuba gear for work. She studies coral reef ecosystems, the “forests of the oceans,” diverse habitats that are vital to many species of ocean life. Warming ocean temperatures disrupt that ecosystem and cause episodes of coral bleaching, | <urn:uuid:701d3eb8-eec0-4799-91ca-06d038d4829d> | 3.609375 | 796 | Knowledge Article | Science & Tech. | 46.412199 |
Scientific name: Epione vespertaria
July - August. Aberdeenshire, Moray and Yorkshire. This small moth is either yellow or orange, with brown bordered wings. Found in open woodland or on grassland. Similar to the Bordered Beauty.
The female tends to be a lighter yellow than the male, it also has a deeper indentation in the dark border along the edge of the wings. The shape of the dark border helps to distinguish this species from the Bordered Beauty, which can also be slightly larger.
The male flies during the day, especially just after sunrise and both sexes can be disturbed from the foodplants in the afternoon. Also flies from dusk and at dawn.
Size and Family
- Family – Thorns, Beauties and allies (Ennomines)
- Small Sized
- UK BAP: Priority Species
- Rare (Red Data Book 3)
Particular Caterpillar Food Plants
Aspen in Scotland, and Creeping Willow in Yorkshire.
- Countries – England, Scotland
- Restricted to a very few sites in Scotland, in Aberdeenshire and the Moray area. Restricted to one site in England, in Yorkshire. Individual records at other localities indicate that it may occur elsewhere.
Prefers open and damp scrubby and heathy grassland, usually near tall trees. | <urn:uuid:38288833-445f-4b79-ab0e-0862d266d631> | 3.078125 | 281 | Knowledge Article | Science & Tech. | 46.377029 |
The Midwestern region of the United States experienced its second coldest December in the 106 year record of observations. The December 2000 average temperature was 14.3°F, just missing the 1983 record of 13.9°F. A number of first-order stations broke their all-time cold records for December, including South Bend, IN; Chicago-Midway, Rockford, and Moline, IL; and Louisville and Paducah, KY. The center of unusually cold conditions was in Iowa, Missouri, and Illinois, where temperatures averaged 12-15°F below normal over most of the three states (Figure 1). Even in relatively warmer locations such as northern Michigan, temperatures were still more than 5°F below normal. The temperature departure pattern in December 2000 was similar to that in December 1983, in the sense that the largest negative anomalies were in the western half of the region (Figure 2). The causes were similar, too. Both cold months occurred during a somewhat neutral to slightly La Niña oriented season, with central equatorial sea surface temperatures slightly cooler than normal. The resulting upper air patterns indicate the preference for a strong trough to develop over the central and eastern United States in both seasons. During December 2000, a strong ridge dominated the western coast of North America, helping to accentuate the north-south delivery of very cold air in the Midwest trough (Figure 3). December 1983 was similar; while the amplitude of the western upper air ridge was less than in 2000, the eastern trough was deeper (Figure 4).
While the amount of liquid water in the precipitation that fell during December 2000 is only slightly above normal overall in the Midwest, some more active regions can be seen in Iowa and the northern tier states (Figure 5). It is unusual for a cold month during winter to also be a month with normal or above normal precipitation. The remarkable aspect of the precipitation in December, though, was that almost all of it was delivered in the form of snow, leading to a widespread deep snow pack that helped to maintain cold temperatures. The snow totals reported in real time in December 2000 vary widely depending on the reliability of reporting, but can be seen to include many very large values, especially in the north-central latitudes of the Midwest (Figure 6). A subset of stations with good climate records and available real-time data show that the snow fall totals were typically more than 10 inches above normal in most of the Midwest (Figure 7). Snow fall exceeded 300% of normal in the central and southern Midwest (Figure 8). While there were several major snowstorms that traversed the region during December, the sheer number of smaller "clipper" systems originating in the northern Rocky Mountains contributed greatly to the overall snow fall totals. At least 15 first-order stations broke all-time records for December snowfall, and five of these set their all-time record snowfall for any month of the year (Table 1). Most of these stations are located in a belt from central Iowa and southern Minnesota eastward through the Great Lakes region (Figure 9). As might be expected, December 1983 was similarly snowy, with the axis of heaviest snow perhaps shifted somewhat to the northern part of the Midwest (Figure 10).
Overall, conditions during December 2000 were quite extraordinary in the Midwest. Illinois experienced its single coldest December in 106 years, while Iowa experienced its largest December snow fall state-wide (Harry Hillaker, Iowa State Climatologist). The December 2000 temperature rankings for each of the nine states in the Midwestern region are available in Table 2, and the temperature and snow fall rankings for a list of major Midwestern cities is given in Table 3. The Climate Prediction Center in Washington, D.C., has indicated an appreciable likelihood for cold weather to continue through the upcoming winter months, especially in the northern Great Lakes region. However, it should be noted that following the record cold December 1983, January-February 1984 was the 25th warmest on record for the Midwest. | <urn:uuid:7b95f622-3145-4801-a016-2adda5d7e638> | 3.421875 | 802 | Academic Writing | Science & Tech. | 39.362833 |
4. CHECKLIST FOR THE NEXT DECADE
As I have been careful to stress the basic tenets of Inflation
+ Cold Dark Matter have not yet been confirmed definitively.
However, a flood of high-quality cosmological data is
coming, and could make the case in the next decade.
Here is my version of how "maybe" becomes "yes."
- Map of the Universe at 300,000 yrs. COBE mapped
the CMB with an angular resolution of around 10°;
two new satellite missions, NASA's MAP (launch 2000)
and ESA's Planck Surveyor (launch 2007), will map the
CMB with 100 times better resolution (0.1°). From
these maps of the Universe as it existed at a
simpler time, long before the first stars and
galaxies, will come a gold mine of information:
Among other things, a definitive measurement of
a determination of the Hubble constant to a precision of
better than 5%;
a characterization of the primeval lumpiness; and possible
detection of the relic gravity waves from inflation.
The precision maps of the CMB that will be made are crucial
to establishing Inflation + Cold Dark Matter.
- Map of the Universe today. Our knowledge of the structure
of the Universe is based upon maps constructed from the positions
of some 30,000 galaxies in our own backyard. The Sloan Digital
Sky Survey will
produce a map of a representative portion of the Universe,
based upon the positions of a million galaxies.
The Anglo-Australian 2-degree Field survey will determine the position of
several hundred thousand galaxies. These surveys will
define precisely the large-scale structure that exists today,
answering questions such as, "What are the largest structures
that exist?" Used together with
the CMB maps, this will definitively test the Cold
Dark Matter theory of structure formation, and much more.
- Present expansion rate H0. Direct measurements
of the expansion rate using standard candles, gravitational time
delay, SZ imaging and the CMB maps will pin down the elusive
Hubble constant once and for all. It is the fundamental parameter
that sets the size - in time and space - of the observable Universe.
Its value is critical to testing the self consistency of Cold
- Cold dark matter. A key element of theory is the
cold dark matter particles that hold the Universe together;
until we actually
detect cold dark matter particles, it will be difficult to argue
that cosmology is solved.
Experiments designed to detect the dark matter that
holds are own galaxy together are now operating with sufficient
sensitivity to detect both neutralinos and axions.
In addition, experiments at particle accelerators (Fermilab
and CERN) will be hunting for the neutralino and its other
- Nature of the dark energy. If the Universe is indeed accelerating,
then most of the critical density exists in the form of dark energy. This
component is poorly understood. Vacuum energy is only the
simplest possibly for the smooth dark component; there are
other possibilities: frustrated topological defects
or an evolving scalar field (see e.g.,
Caldwell et al, 1998;
Turner & White, 1997).
Independent evidence for the existence
of this dark energy, e.g., by CMB anisotropy, the SDSS and 2dF
surveys, or gravitational
lensing, is crucial for verifying the accounting of matter and energy
in the Universe I have advocated. Additional measurements of SNe1a could
help shed light on the precise nature of the dark energy. The dark
energy problem is not only of great importance for cosmology, but
for fundamental physics as well. Whether it is vacuum energy or
quintessence, it is a puzzle for fundamental physics and possibly
a clue about the unification of the forces and particles. | <urn:uuid:606aa78d-6e2e-4f18-ba06-96b1eb161c6a> | 2.921875 | 827 | Academic Writing | Science & Tech. | 40.179762 |
light in space
1. According to the books, the speed of light in a vacuum
is 300,000 km per second. If you send out a sudden pulse
of light in space, does it have to accelerate to that speed?
2. If you could make a _very_ long tube in space, with
a mirror at both ends (perfect mirrors, and perhaps long
enough to reach from earth to Venus), could you open one end,
shine a bright light in for a few seconds, then slide the
mirror back in place, trapping the beam of light in there?
Would the light beam keep bouncing back and forth?
1. No, light starts out at the speed of light - it does not
have to accelerate. What does happen is that the amplitude
(of the electric and magnetic fields) gradually increases
so that at the start of the pulse the amplitude is small,
it then rises to a peak, and then falls back down to
2. Yes, you sure could do that. In fact, that is essentially
the way some experiments on fiber optics work (and somewhat
related to the way lasers work). Apparently a recent
experiment by some Japanese researchers has sent light
pulses round and round a fiber optic cable for some
180 million miles - that is getting into astronomical
distances right here on earth!
But why does not light "have to accelerate"? In truth it does,
but the acceleration to light speed is instantaneous. That is because light
is made up of massless photons. The force that creates the photons
gives them infinite acceleration, so they reach the speed of light
Click here to return to the Physics Archives
Update: June 2012 | <urn:uuid:996dd21f-14ac-4602-86ae-847a661c620d> | 3.578125 | 356 | Knowledge Article | Science & Tech. | 65.286147 |
7 February 2006
Most cosmologists believe that the universe is dominated by “dark energy” — a mysterious form of energy that could explain why the universe is expanding and accelerating at the same time.
Now, however, theoretical physicists have studied a new model of gravity that can, they claim, account for the acceleration of the universe without any need for dark energy.
Their model relies instead on modifications to the way that gravity behaves at ultra-large cosmological distances (Phys. Rev. Lett. 96 041103). | <urn:uuid:1b0008e7-bee1-4ade-8ba4-88118b31bf00> | 3.0625 | 110 | Truncated | Science & Tech. | 36.844769 |
Comet 32 Runtime
The RETURN statement transfers program control to the statement
immediately following the most recently invoked subroutine call.
All subroutine calls in Internet Basic place a "return address" in a subroutine stack. The RETURN statement simply transfers program control to the address on the top of this stack. It also removes or "pops" the address from the top of the stack so that a subsequent RETURN statement will use the next address it finds on the top of the stack.
Executing a RETURN statement with no return address in the subroutines stack causes a "GOSUB STACK UNDERFLOW" exception condition.
Processing continues in the subroutine until the program encounters the RETURN statement. At this point, control is transferred back to the main section of the program (to the statement immediately after the GOSUB 1000 statement).
The STOP statement is included in the main section of the program to prevent program flow from entering the subroutine without using the GOSUB statement. | <urn:uuid:64fce9e0-e974-4384-ae61-a0fed57fe972> | 3.078125 | 215 | Documentation | Software Dev. | 39.27769 |
Phenology: Changes in Ecological Lifecycles
By Zack Guido | The University of Arizona | September 12, 2008
Lilac flowers bloom with cues from the weather. Caribou give birth at the peak of plant abundance so that their newborns have plenty to eat. In the Southwest, as well as all other parts of the world, variations in the climate trigger life cycle events in plants and animals. Studying these events and their relation to climate is known as phenology. The information obtained is vital for understanding the impact climate change has on humans and ecosystems.
A Gila woodpecker feeding on the flowers of the giant saguaro cactus. The timing of blooming may shift in a changing climate.
Credit: ©Frank Leung, istockphoto.com
Phenology includes the timing of flower blooms, agricultural crop stages, insect activity, and animal migration. All of these events are changing as a result of climate change and these changes impact humans. The date flowers bloom, for example, controls the timing of allergens and infectious diseases—impacting human health—and alters when tourists visit regions to enjoy wildflowers, which impacts economies. Variations in crop phases affect agriculture by influencing the timing of planting, harvesting, and pest activity.
Quantitative assessments of the impact of phenological changes on humans in the Southwest are scant primarily because phenology is a relatively recent scientific endeavor in the Southwest. However, increasing concern about climate change has amplified efforts in the following areas:
- Documenting observed phenological changes
- Projecting phenological changes from climate change
- Establishing a national phenological network
Phenology in the Southwest is relatively young and there are only a few observational records more than 20 years old. Nonetheless, records less than 20 years are sufficient to observe trends in phenological changes, and experts believe that changes in life cycle events in the Southwest will be similar to those documented in other parts of the world where longer records exist.
Two of the more important and well-documented effects of climate change on phenology are changes in the date of flowering and food-chain disruptions.
Changes in flower blooms
Studies indicate an advance in the date that flowers bloom in the West. Important conclusions include the following:
- Shrub specimens collected in the Sonoran Desert of the southwestern U.S. and northwestern Mexico and biological models suggest that the spring bloom of shrubs may have advanced by 20 to 41 days between 1894 and 20041
- A study published in 2001 concluded that the average date of bloom for lilacs in the western U.S. advanced by 7.5 days between 1957 and 1994, while the average bloom date of honeysuckle advanced by 10 days between 1968 and 1994.2
- A 20-year record of the timing of flower blooms for hundreds of plant species across 4,000 vertical feet in the Santa Catalina Mountains near Tucson, Arizona, suggests more than 15 percent of the surveyed species bloom at elevations as much as 1,000 feet higher than they did in the past.3
- The same 20-year record showed the average total number of species in bloom per year increased over the 20-year period by nearly three species per year at the highest elevations—this increase was associated with increasing summer temperatures.4
Food chain disruption
Important life cycle events in plants and animals are often triggered by each other. When the timing of life cycle events changes in one species, it can disrupt symbiotic relationships and affect other species. For example, in the northeastern U.S., nectar-producing trees currently bloom 25 days earlier than in the past. As a result, honey bees have switched their source of nectar from the tulip poplar tree to black locust tree, impacting the pollination of tulip poplars and causing their numbers to crash.5 In the Arctic, the peak in plant abundance and caribou births no longer coincide, causing a 400 percent jump in offspring mortality.
Future phenological changes will be localized, depending on the specific plant and animal species and the magnitude of climate change. Some species may profit, while others suffer. In general, flowers will likely bloom earlier and food-chain disruptions will likely be more frequent. Several changes are likely in the Southwest:
- Because the date and abundance of flower blooms are highly correlated with winter snowpack, projected declines in snowpack will decrease flower abundance and advance the date of flowering.6
- Global warming may have a disproportionate effect on montane plant communities. Some mountain species may not be able to respond to changes in temperature by migrating north or south. In addition, an upward shift in altitudinal range of species to encounter cooler temperatures will decrease habitat area.2
- Earlier flower blooms could have substantial impacts on plant and animal communities in the Sonoran Desert, especially on shrubs and migratory hummingbirds.1
In addition, climate change will cause plant species to move in response to changes in temperature and precipitation. This may be most evident on mountains, where changes in elevation help create specific habitat zones within small areas. In the Santa Catalina Mountains near Tucson, Arizona, for example, the habitat of many species has expanded upslope, and to a lesser extent downslope.
The USA National Phenology Network (NPN) is headquartered in Tucson, Arizona. Its mission is to facilitate collection and dissemination of phenological data from the United States. NPN primarily supports scientific research concerning interactions among plants, animals, and the lower atmosphere, especially the long-term impacts of climate change.
NPN encourages involvement in phenological research and provides opportunities for interested people to contribute to science. Scholars, students of all grades, and citizens record the timing of life cycle events in key plant and animal species and submit their observations on-line. In this manner, a detailed database is growing. Currently, 800 people in the U.S. participate in NPN. Among them, amateur scientists in the Southwest have provided some of the more valuable and longer observational data.
- Bowers, J. E. 2007. Has climatic warming altered spring flowering date of Sonoran desert shrubs? The Southwestern Naturalist, 52(3):347-355.
- Cayan, D. R., et al. 2001. Changes in the onset of spring in the western United States. Bulletin of the American Meteorological Society, 82(3):399-415.
- Personal communication with Dave Bertelsen, August 4, 2008.
- Crimmins, T. H., M. A. Crimmins, D. Bertelsen and J. Balmat. 2008. Relationships between alpha diversity of plant species in bloom and climatic variables across an elevation gradient. International Journal of Biometeorology, 52:353-366.
- Personal communication with Jake Weltzin, July 21, 2008.
- Inouye, D. W., M. A. Morales and G. J. Dodge. 2002. Variation in timing and abundance of flowering by Delphinium barbeyi Huth (Ranunculaceae): The roles of snowpack, frost, and La Niña, in the context of climate change. Oecologia, 130:543–550. | <urn:uuid:c4515ae2-0ac7-44ec-a9dc-42ec8a5adf76> | 3.609375 | 1,489 | Knowledge Article | Science & Tech. | 42.405384 |
Some animals, like earthworms, snails, and spiders, have nerves but not actual brains.
A one-year-old child's brain weighs about 2 pounds (950 g), ten times the weight of a dog's brain.
The primate cortex is so large that it has to be folded to fit inside the skull. That's why the surface of the brain is wrinkly.
The nervous system runs on electricity, but the levels are low. Brain signals involve less than one-tenth the voltage of an ordinary flashlight battery.
AT THE MUSEUM
See how good you're at recognizing emotions.
How fast can you catch a falling ruler? Measure your reaction time.
Take the jellybean test to see how your sense of smell enhances taste.
Use Braille to create a message for a friend.
Explore your nerves by creating a life-sized drawing.
Try these trippy experiments to fool your brain.
Scientist Rob DeSalle answers kids' questions about the brain!
Test your sight and memory with these brain games. | <urn:uuid:3bd155a1-25f8-411c-9c34-1d130efec406> | 3.53125 | 219 | Knowledge Article | Science & Tech. | 69.394547 |
What's a Mangrove? And How Does It Work?
If you've ever spent time by the sea in a tropical place, you've probably noticed distinctive trees that rise from a tangle of roots wriggling out of the mud. These are mangroves—shrub and tree species that live along shores, rivers, and estuaries in the tropics and subtropics. Mangroves are remarkably tough. Most live on muddy soil, but some also grow on sand, peat, and coral rock. They live in water up to 100 times saltier than most other plants can tolerate. They thrive despite twice-daily flooding by ocean tides; even if this water were fresh, the flooding alone would drown most trees. Growing where land and water meet, mangroves bear the brunt of ocean-borne storms and hurricanes.
There are 80 described species of mangroves, 60 of which live exclusively on coasts between the high- and low-tide lines. Mangroves once covered three-quarters of the world's tropical coastlines, with Southeast Asia hosting the greatest diversity. Only 12 species live in the Americas. Mangroves range in size from small bushes to the 60-meter giants found in Ecuador. Within a given mangrove forest, different species occupy distinct niches. Those that can handle tidal soakings grow in the open sea, in sheltered bays, and on fringe islands. Trees adapted to drier, saltier soil can be found farther from the shoreline. Some mangroves flourish along riverbanks far inland, as long as the freshwater current is met by ocean tides.
One Ingenious Plant
How do mangroves survive under such hostile conditions? A remarkable set of evolutionary adaptations makes it possible. These amazing trees and shrubs:
- cope with salt: Saltwater can kill plants, so mangroves must extract freshwater from the seawater that surrounds them. Many mangrove species survive by filtering out as much as 90 percent of the salt found in seawater as it enters their roots. Some species excrete salt through glands in their leaves. These leaves, which are covered with dried salt crystals, taste salty if you lick them. A third strategy used by some mangrove species is to concentrate salt in older leaves or bark. When the leaves drop or the bark sheds, the stored salt goes with them.
- hoard fresh water: Like desert plants, mangroves store fresh water in thick succulent leaves. A waxy coating on the leaves of some mangrove species seals in water and minimizes evaporation. Small hairs on the leaves of other species deflect wind and sunlight, which reduces water loss through the tiny openings where gases enter and exit during photosynthesis. On some mangroves species, these tiny openings are below the leaf's surface, away from the drying wind and sun.
- breathe in a variety of ways: Some mangroves grow pencil-like roots that stick up out of the dense, wet ground like snorkels. These breathing tubes, called pneumatophores, allow mangroves to cope with daily flooding by the tides. Pneumatophores take in oxygen from the air unless they're clogged or submerged for too long.
Roots That Multitask
Root systems that arch high over the water are a distinctive feature of many mangrove species. These aerial roots take several forms. Some are stilt roots that branch and loop off the trunk and lower branches. Others are wide, wavy plank roots that extend away from the trunk. Aerial roots broaden the base of the tree and, like flying buttresses on medieval cathedrals, stabilize the shallow root system in the soft, loose soil. In addition to providing structural support, aerial roots play an important part in providing oxygen for respiration. Oxygen enters a mangrove through lenticels, thousands of cell-sized breathing pores in the bark and roots. Lenticels close tightly during high tide, thus preventing mangroves from drowning.
The mangroves' niche between land and sea has led to unique methods of reproduction. Seed pods germinate while on the tree, so they are ready to take root when they drop. If a seed falls in the water during high tide, it can float and take root once it finds solid ground. If a sprout falls during low tide, it can quickly establish itself in the soft soil of tidal mudflats before the next tide comes in. A vigorous seed may grow up to two feet (about 0.6 m) in its first year. Roots arch from the seedling to anchor it in the mud. Some tree species form long, spear-shaped stems and roots while still attached to the parent plant. After being nourished by the parent tree for one to three years, these sprouts may break off. Some take root nearby while others fall into the water and are carried away to distant shores.
A World Traveler
Botanists believe that mangroves originated in Southeast Asia, but ocean currents have since dispersed them to India, Africa, Australia, and the Americas. As Alfredo Quarto, the head of the Mangrove Action Project, puts it, “Over the millions of years since they've been in existence, mangroves have essentially set up shop around the world.” The fruits, seeds, and seedlings of all mangrove plants can float, and they have been known to bob along for more than a year before taking root. In buoyant seawater, a seedling lies flat and floats fast. But when it approaches fresher, brackish water—ideal conditions for mangroves—the seedling turns vertical so its roots point downward. After lodging in the mud, the seedling quickly sends additional roots into the soil. Within 10 years, as those roots spread and sprout, a single seedling can give rise to an entire thicket. It's not just trees but the land itself that increases. Mud collects around the tangled mangrove roots, and shallow mudflats build up. From the journey of a single seed a rich ecosystem may be born.
More About This Resource...
Our innovative Science Bulletins are an online and exhibition program that offers the public a window into the excitement of scientific discovery. This essay was published in May 2004 as part of the Mangroves: The Roots of the Sea Bio Feature.
- It begins by explaining that these remarkably tough shrub and tree species can live in water up to 100 times saltier than most other plants can tolerate and thrive despite twice-daily flooding by ocean tides.
- It then details the remarkable set of evolutionary adaptations that allow mangroves to survive under such hostile conditions.
- The essay concludes with a note about how botanists believe that mangroves originated in Southeast Asia, but ocean currents have since dispersed them to India, Africa, Australia, and the Americas.
Supplement a study of biology with a classroom activity drawn from this Science Bulletin essay.
- Have students read the essay (either online or a printed copy).
- Working individually or in small groups, have them investigate the Explore a Mangrove Forest interactive. | <urn:uuid:0f198350-c837-4dc6-bdfe-ac3b5bfad431> | 4.0625 | 1,472 | Knowledge Article | Science & Tech. | 51.604172 |
Web Programming is the process of creating Internet Applications. Any application that uses the Internet in a way, can be considered an Internet application. They can be classified into four common categories:-
Web Applications - Applications based on the Client/Server architecture over the Internet.
The Client/Server architecture is composed of a server, which is responsible for providing services to the other computer systems - Clients. Typically, there is a single server which handles requests from multiple clients and responds to these requests by providing the client with the appropriate information.
In a Web Application, the server is the machine where the web page is stored and the clients employ web browsers to view the application. Such a server is called a Web Server.
Web Services - Web Services are components that expose processing services from a server to other applications over the Internet. The services themselves are executed remotely in the server hosting them.
Internet Enabled Applications - Any stand-alone application that uses the Internet falls into this category. Such an an application uses the Internet for online Registration/Activation, Help, Updates, etc.
Peer-to-Peer Applications - These are stand-alone applications that use the Internet to communicate with other users running their own instances of the application. They use decentralized network architecture where there is no central server, rather individual nodes. Examples of such applications can include the famous Bit Torrent client.
Note:- In this tutorial, we would be involved with Web Application only.
Working of the Web Applications
As mentioned before, the client side of the Web Application includes a web browser, which interprets Hypertext Markup Language (HTML) transferred by the server and displays the user interface. The server itself runs the web applications under Microsoft Internet Information Services (IIS) which is responsible for managing the application, passing request from clients to the application and returning the application's responses to the client. The intricate communication involved in this process is done by using a standard set of rules (Protocols) known as the Hypertext Transfer Protocol (HTTP).
The responses generated by the Web application is made from the resources (Executable code running on the server, Web Forms, HTML pages, images and other media files) found on the server. These responses are similar to traditional Web sites with HTML pages, except that they are dynamically generated. Consider a university's web site which releases the exam results. Do they take the pain of creating different HTML pages for each of the student's mark sheet? No, they use web applications to retrieve data (marks, subjects, student name, roll no, etc) from a database and dynamically generate the HTML output which is then sent to the client's browser.
The executable portion of the Web application is responsible for overcoming the limitations of static web pages. They can be used to:-
- Collect information from the user and store the information on the server (in a database).
- Performing tasks for the user such as placing an order for a product, performing complex calculations, or retrieving information from a database.
- Identify a user and present customized user interface.
ASP .NET is the platform that allows us to create Web applications and services that run under IIS. One must note that ASP .NET is NOT the only platform to develop Web applications. Other platforms such as Common Gateway Interface (CGI) can also be used to create Web applications. ASP .NET is unique in the way it is tightly integrated with Microsoft server, programming, data access and security tools. It forms a part of the Microsoft .NET suite of products and is composed of:-
- Visual Studio .NET Web Development Tools - These are Graphical User Interface (GUI) based tools to facilitate easy designing of Web pages using What You See Is What You Get (WYSIWYG) editors, project management and deployment tools.
- The System.Web namespaces - These form a part of the .NET Framework Base class libraries and include the programming classes that deal with Web specific items such as HTTP requests and responses, browsers and e-mail.
- Server and HTML Controls - The user interface components such as Text Box, label, Button, ListBox, etc. that are used to gather information from and provide to users.
- Microsoft ADO.NET database classes and tools - Database access is one of the key components of modern Web applications. These tools provide methods to access and use Microsoft SQL Server and ODBC databases.
- Microsoft Application Center Test (ACT) - Testing environment for Web applications.
Why Choose ASP .NET?
The following are the advantages that ASP .NET has over other platforms:-
- Faster execution - Executable portions of Web applications are compiled to facilitate faster performance.
- On the fly updates of deployed Web applications thus preventing the need to restart the server.
- The amount of code to be written is greatly reduced because of the access to .NET Framework base class libraries which includes classes and methods to perform common operations.
- Language independent - Developers have the choice to write codes in the friendly Visual Basic programming language or the type safe C# language. Other third party .NET compliant languages can also be used.
- Automatic state management for controls on a web page (server controls) makes the controls behave more like the Windows controls.
- New controls can be created and existing controls can be extended.
- Built in security through the Windows server or through other authentication/authorization methods.
- Integration with ADO .NET to provide database access and database design tools from within Visual Studio .NET
- Full support for Extensible Markup Language (XML) and Cascading Style Sheets (CSS)
- Automatic intelligent caching of frequently requested Web pages, localizing content for specific languages and cultures and detecting browser capabilities.
Previous Tutorial - The .NET Framework & CLR : Basic Introduction
Edited by turbopowerdmaxsteel, 06 April 2007 - 09:35 AM. | <urn:uuid:0c01a907-82ff-48b2-a8d2-a12fdb03cb7f> | 3.703125 | 1,205 | Tutorial | Software Dev. | 33.535153 |
Two long straight wires cross each other at right angles, and
the horizontal wire carries 2 I (capital i ) Amp and vertical wire
carries one I Amp. Assume ABC and D are equal distance L from both
vertical and horizontal wires. Calculate B field in term of I and L
and other fundamental constants at each of the points ABC and D due
to the two wires.
( for some reason I am having trouble uploading the figure.. If you need the figure I can probably try to describe it.. Just comment)
so the top left of the square is "A" ; bottom left is "B" ; bottom right is "C" and top right is "D"
on the horizontal,, there should be an arrow pointing to the right which has a value of 2I and on the vertical axis there should be an arrow pointing upward that has a value of I. L would be the distance from the the vertical and horizontal wires. (so on each quadrant, the horizontal and vertical lines from the partial square would have a label "L") | <urn:uuid:dbf258ab-85bc-4fb4-af12-9ab01bb08037> | 3.125 | 220 | Q&A Forum | Science & Tech. | 65.655599 |
Definitions for ultra-gaseous matter
The Standard Electrical Dictionary
Gas so rarefied that its molecules do not collide or very rarely do so. Experiments of very striking nature have been devised by Crookes and others to illustrate the peculiar phenomena that this matter presents. The general lines of this work are similar to the methods used in Geissler tube experiments, except that the vacua used are very much higher. When the vacuum is increased so that but one-millionth of the original gas is left the radiant state is reached. The molecules in their kinetic movements beat back and forth in straight lines without colliding, or with very rare collisions. Their motions can be guided and rendered visible by electrification. A tube or small glass bulb with platinum electrodes sealed in it, is exhausted to the requisite degree and is hermetically sealed by melting the glass. The electrodes are connected to the terminals of an induction coil or other source of high tension electrification. The molecules which come in contact with a negatively electrified pole are repelled from it in directions normal to its surface. They produce different phosphorescent or luminous effects in their mutual collisions. Thus if they are made to impinge upon glass, diamond or ruby, intense phosphorescence is produced. A piece of platinum subjected to molecular bombardment is brought to white heat. A movable body can be made to move under their effects. Two streams proceeding from one negative pole repel each other. The stream of molecules can be drawn out of their course by a magnet. The experiments are all done on a small scale in tubes and bulbs, resembling to a certain extent Geissler tubes. [Transcriber's note: These effects are caused by plasma--ionized gas and electrons.]
Use the citation below to add this definition to your bibliography:
"ultra-gaseous matter." Definitions.net. STANDS4 LLC, 2013. Web. 19 May 2013. <http://www.definitions.net/definition/ultra-gaseous matter>. | <urn:uuid:6b1b6976-2352-4b69-8132-9755a8ffd135> | 3.0625 | 414 | Structured Data | Science & Tech. | 41.175427 |
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The OSV Bold supports a variety of monitoring and educational tasks. The ship carries high-tech instruments to collect data from the water column, sediments, and even marine life. The Bold also carries onboard equipment that can take underwater video, side-scan sonar, and sampling instruments such as corers, dredges, and trawls. Onboard laboratories allow scientists to process, analyze, and store samples while they are out at sea.
The sturdy A-frame on the back deck of the Bold, helps the scientists deploy the equipment for sampling and monitoring.
A bottom grab, does exactly what it sounds like! This piece of equipment catches muddy sediment, and it can collect down to about two feet into the bottom. The grab is lowered to the bottom by a cable and water is able to flow through it as it is lowered down. When it hits the bottom, it releases a catch that allows the two doors to close, capturing the mud. Scientists use this grabbing technique to measure the concentrations of pollutants in the mud or to look at the small marine invertebrates, such as worms (polychaetes), crustaceans (such as amphipods), or mollusks (such as small clams) that may live in the surface of the sediments. This type of sample is incredibly important. Scientists can tell if the study area is a healthy environment or polluted depending on the types of species of organisms they find in the mud grabs.
Next to the onboard dry lab, there is a computer room. In here, scientists can use remote control equipment to steer the side scan tow fish, tell the CTD how deep to go and watch underwater video of the area they are studying!
A CTD is the primary tool for understanding the physical properties of sea water that are essential for supporting marine life. C stands for "Conductivity," T stands for "Temperature," and D stands for "Depth". A CTD gives scientists an accurate and comprehensive charting of the distribution and change in water temperature, salinity, and density for the water column they are studying. All of these are important for understanding how healthy an area of water is for supporting marine life.
How does a CTD work?
The CTD is made up of a set of small high tech probes, attached to the large metal rosette water sampler. The rosette is lowered on a cable down to the depths that the scientists want to evaluate, sometimes all the way to the seafloor. While the CTD is still underwater it reports electronic messages through a cable back to the onboard computer lab. While the CTD is gathering data underwater, computers on the ship are constantly reading that data and creating charts and line graphs. This helps the scientists understand right away the changes in the water column as the CTD goes deeper and deeper.
A typical CTD drop, or hydro-cast as the scientists like to call it, can take 5 to 15 minutes depending on how deep the scientists want to go. For the work that EPA does, generally within depths of 300 feet, gathering a complete set of CTD data can take less than 20 minutes.
True or False?
Salinity and conductivity both refer to the amount of dissolved salt in a body of water.
Up in the dry lab, on board the ship, scientists can look at organisms under microscopes. These organisms can be collected in the mud, or water and by looking at the species, the scientists can tell if the environment is healthy or polluted, or even being taken over by invasive species that don't naturally belong there.
Believe it or not! Some oceanic organisms like pollution, and there presence in a mud sample can tell a scientist a lot about that underwater environment.
The otter trawl is a specialized net for catching fish on the bottom of the ocean in sandy, silty seabeds. Contrary to the name, it is not used for collecting otters! When scientists are trying to determine the health of ocean bottom environment, it is sometimes helpful to collect real fish for the study.
If the ocean bottom is too muddy, or has too many rocks or boulders, the otter trawl doesn't work very well. When it is slowly dragged on the bottom, (at about 2 knots, or 2 mph) the scientists do not want it to get snagged on a boulder that could tear it!
In 2007, this type of trawl helped scientists on the OSV Bold check on some close-to-shore habitats for winter flounder in Rhode Island Sound. The population of winter flounder has decreased dramatically off the coast of Rhode Island in the past 25 years. To try to better understand why this has happened, the scientists wanted to identify the most important nursery zones for flounder. The Bold helped scientists collect data from off shore adult flounder to compare with younger, juvenile flounder still living in the near-shore nursery habitats. By a trace chemical, "fingerprint technique", the scientists could tell which nursery zone the adult flounder had come from. Once EPA and the state of Rhode Island have a better idea where most of the flounder are coming from, everyone can work to better protect those important habitats.
A rocking chair dredge is like the trawl, as it is slowly pulled behind the boat. This type of dredge is used to collect or sample for shellfish such as clams, or scallops in the bottom sediments, it works well in sandy bottom environments. The dredge rocks up and down in the sediment collecting the shellfish, which are contained in its mesh bag.
While EPA scientists usually collect waters samples within 300 feet deep, this equipment has the ability to go down thousands of meters.
How many feet are in 1 meter?
Read about the latest dive mission in Puerto Rico!
Every day, I commute to my EPA office in downtown New York. However, twice a year, I'm assigned to work on EPA's Ocean Survey Vessel BOLD. I am currently on assignment in Puerto Rico to monitor coral reefs. Read More »
Coral Condition Survey Continues
We spent the first eight days of BOLD operations deploying dive teams to 60 locations spread across the entire southern coast of Puerto Rico to collect data on the corals. Read More »
Side-scan sonar is a type of sonar system that is used to be able to understand what lies at the bottom of the sea floor. On the Bold, the side-scan sonar "tow fish" can create an image of the sea floor so that the scientists can understand the hills, valleys, reefs and debris that are in the study area. This tool is used for mapping the seabed for a wide variety of purposes, including creation of nautical charts and detection and identification of underwater objects and bathymetric features.
Bathymetry is the study of underwater depth. Check out this map! Purple areas are the deepest, yellow shows areas of land above the surface of the water.
Side scan sonar can be used to conduct surveys for maritime archaeology; along with seafloor samples, the sonar can help scientists understand the different materials and textures of the seabed. The pictures that the sonar tow fish sends back to the ship oftentimes find debris items left from human activities. Check out our gallery of side scan images!
What else can side scan sonar help with?
On the Bold, the side-scan sonar is called the "tow fish" because it is pulled behind the ship underwater. Slowly, and carefully, the ship’s crew guides the ship in a set path to gather an image of the ocean floor beneath.
To make the image, the sonar "tow fish" sends out a fan shaped series of pulses (sound frequencies) down toward the seafloor. The intensity of the acoustic reflections from the seafloor of this fan-shaped beam is recorded in a series of cross-track slices. When stitched together by a computer, these slices can form an image of the sea bottom within the swath (coverage width) of the beam.
One of the inventors of side-scan sonar was German scientist, Dr. Julius Hagemann, who worked for the US navy Mine Defense Laboratory in Florida after WW II. His work is documented in US Patent 4,197,591, which remained classified by the US Navy until it was issued in 1980.
In 1963 Dr. Harold Edgerton, Edward Curley, and John Yules used side-scan sonar to find the sunken Vineyard Lightship in Buzzards Bay, Massachusetts.
A team led by Martin Klein developed the first successful towed, commercial, (non-military) side-scan sonar system from 1963 to 1966.
In 1967, Klein's sonar helped find King Henry VIII's flagship Mary Rose. That same year the side scan sonar also aided in the archaeologist George Bass, find a 2000 year old ship off the coast of Turkey.
In 1968 Klein founded Klein Associates, Inc, the company that designed the side scan sonar that is used on the Bold.
Why do YOU think this area is called the WET LAB? This room is right on the deck where scientists on the Bold deploy the sampling equipment. This way, a mud grab can be put directly into the wet lab to be studied. Sometimes the scientists hose down the sediment to see what organisms are in it and it can get a little messy!
The wet lab is equipped with a sieve station (sieving tables and trays), wash station with hot and cold, freshwater and salt water, an ice machine for sample preservation, refrigerator, and an electronic navigation chart that displays the ship’s location and navigation information.
Contact the Bold Kids web editor to ask a question, provide feedback, or report a problem. | <urn:uuid:2d0d0052-c712-4ad6-89ec-a82e943091b9> | 3.703125 | 2,037 | Knowledge Article | Science & Tech. | 53.947236 |
Number of stars en
The best estimated count of the total number of stars in a galaxy. It's primarily an estimate because of the inherent difficulty to ascertain the exact total body of galaxies and possible obscuring of portions of a galaxy by itself or intervening celestial objects between the observer and the observed galaxy. The Milky Way is particularly difficult as we can only see our local portions of the galaxy with a portion of it not visible or measurable. [ - ]
What are Properties? Properties
Estimated number of stars in the celestial body/region,
The estimate error range +/- value,
What are Included Types? Included Types
This type doesn't have any included types. | <urn:uuid:3fb7d2a2-acce-4b9b-84b5-e39ee1a603f4> | 2.921875 | 135 | Structured Data | Science & Tech. | 30.965789 |
There’s a course at Yale University in which undergraduates travel to the Amazon rain forest to collect fungi.
The fungus samples are often nothing you’ve encountered. One of them, however, which will be featured in a paper accepted by a scientific journal, might solve the problem of polyurethane building up in our landfills. The fungus basically eats the plastic and breaks it down into carbon.
That’s just one discovery being studied in the Rainforest Expedition and Laboratory course taught by professor Scott A. Strobel.
“We take 15 undergraduates into the Ecuadorean rain forest and collect plant samples,” said Kaury Kucera, co-instructor of the course and a postdoctoral researcher in the department of molecular biophysics and biochemistry.
The fungus they’re looking for “grows in the inner tissues of plant samples that is symbiotic with the plant and often produces natural compounds that are interesting to medicine,” Kucera said.
Click "source" for entire article. | <urn:uuid:2d6808b0-5c98-46c6-849f-49b15d671b18> | 3.078125 | 221 | Truncated | Science & Tech. | 36.633347 |
The IDLgrTessellator class is a helper class that converts a simple concave polygon (or a simple polygon with holes) into a number of simple convex polygons (general triangles). A polygon is simple if it includes no duplicate vertices, if the edges intersect only at vertices, and exactly two edges meet at any vertex.
Tessellation is useful because the IDLgrPolygon object accepts only convex polygons. Using the IDLgrTessellator object, you can convert a concave polygon into a group of convex polygons.
The IDLgrTessellator::Init method takes no arguments. Use the following statement to create a tessellator object:
myTess = OBJ_NEW('IDLgrTessellator')
See IDLgrTessellator for details on creating tessellator objects.
The procedure file
obj_tess.pro, located in the
examples/visual subdirectory of the IDL distribution, provides an example of the use of the IDLgrTessellator object. To run the example, enter OBJ_TESS at the IDL prompt. The procedure creates a concave polygon, attempts to draw it, and then tessellates the polygon and re-draws. Finally, the procedure demonstrates adding a hole to a polygon. (You will be prompted to press Return after each step is displayed.) You can also inspect the source code in the
obj_tess.pro file for hints on using the tessellator object. | <urn:uuid:55ea103e-d05b-4d17-afe3-3d22471f1685> | 2.71875 | 329 | Documentation | Software Dev. | 30.638619 |
Refraction at a Boundary
Need to see it? View The Broken Pencil animation from the Multimedia Physics Studios.Flickr Physics
Visit The Physics Classroom's Flickr Galleries and enjoy a photo overview of the topic of refraction and lenses.Flickr Physics
Visit The Physics Classroom's Flickr Galleries and enjoy the terrific display of photos showing the refraction of light by dew drops.Flickr Physics
View a collection of incredible photos of reflection and refraction phenomena from TPC's Flickr Pool.
Looking for a lab that coordinates with this page? Try the Refraction Action Lab from The Laboratory.Flickr Physics
View a collection of incredible photos of reflection and refraction phenomena from TPC's Flickr Pool.Curriculum Corner
Learning requires action. Give your students this sense-making activity from The Curriculum Corner.Treasures from TPF
Need ideas? Need help? Explore The Physics Front's treasure box of catalogued resources on ray optics, including the topic of refraction.
Refraction and Sight
In Unit 13 of The Physics Classroom Tutorial, it was emphasized that we are able to see because light from an object can travel to our eyes. Every object that can be seen is seen only because light from that object travels to our eyes. As you look at Mary in class, you are able to see Mary because she is illuminated with light and that light reflects off of her and travels to your eye. In the process of viewing Mary, you are directing your sight along a line in the direction of Mary. If you wish to view the top of Mary's head, then you direct your sight along a line towards the top of her head. If you wish to view Mary's feet, then you direct your sight along a line towards Mary's feet. And if you wish to view the image of Mary in a mirror, then you must direct your sight along a line towards the location of Mary's image. This directing of our sight in a specific direction is sometimes referred to as the line of sight.
As light travels through a given medium, it travels in a straight line. However, when light passes from one medium into a second medium, the light path bends. Refraction takes place. The refraction occurs only at the boundary. Once the light has crossed the boundary between the two media, it continues to travel in a straight line. Only now, the direction of that line is different than it was in the former medium. If when sighting at an object, light from that object changes media on the way to your eye, a visual distortion is likely to occur. This visual distortion is witnessed if you look at a pencil submerged in a glass half-filled with water. As you sight through the side of the glass at the portion of the pencil located above the water's surface, light travels directly from the pencil to your eye. Since this light does not change medium, it will not refract. (Actually, there is a change of medium from air to glass and back into air. Because the glass is so thin and because the light starts and finished in air, the refraction into and out of the glass causes little deviation in the light's original direction.) As you sight at the portion of the pencil that was submerged in the water, light travels from water to air (or from water to glass to air). This light ray changes medium and subsequently undergoes refraction. As a result, the image of the pencil appears to be broken. Furthermore, the portion of the pencil that is submerged in water appears to be wider than the portion of the pencil that is not submerged. These visual distortions are explained by the refraction of light.
In this case, the light rays that undergo a deviation from their original path are those that travel from the submerged portion of the pencil, through the water, across the boundary, into the air, and ultimately to the eye. At the boundary, this ray refracts. The eye-brain interaction cannot account for the refraction of light. As was emphasized in Unit 13, the brain judges the image location to be the location where light rays appear to originate from. This image location is the location where either reflected or refracted rays intersect. The eye and brain assume that light travels in a straight line and then extends all incoming rays of light backwards until they intersect. Light rays from the submerged portion of the pencil will intersect in a different location than light rays from the portion of the pencil that extends above the surface of the water. For this reason, the submerged portion of the pencil appears to be in a different location than the portion of the pencil that extends above the water. The diagram at the right shows a God's-eye view of the light path from the submerged portion of the pencil to each of your two eyes. Only the left and right extremities (edges) of the pencil are considered. The blue lines depict the path of light to your right eye and the red lines depict the path of light to your left eye. Observe that the light path has bent at the boundary. Dashed lines represent the extensions of the lines of sight backwards into the water. Observe that these extension lines intersect at a given point; the point represents the image of the left and the right edge of the pencil. Finally, observe that the image of the pencil is wider than the actual pencil. A ray model of light that considers the refraction of light at boundaries adequately explains the broken pencil observations.
Flickr Physics Photo
The broken pencil phenomenon occurs during your everyday spearfishing outing. Fortunately for the fish, light refracts as it travels from the fish in the water to the eyes of the hunter. The refraction occurs at the water-air boundary. Due to this bending of the path of light, a fish appears to be at a location where it isn't. A visual distortion occurs. Subsequently, the hunter launches the spear at the location where the fish is thought to be and misses the fish. Of course, the fish are never concerned about such hunters; they know that light refracts at the boundary and that the location where the hunter is sighting is not the same location as the actual fish. How did the fish get so smart and learn all this? They live in schools.
Now any fish that has done his/her physics homework knows that the amount of refraction that occurs is dependent upon the angle at which the light approaches the boundary. We will investigate this aspect of refraction in great detail in Lesson 2. For now, it is sufficient to say that as the hunter with the spear sights more perpendicular to the water, the amount of refraction decreases. The most successful hunters are those who sight perpendicular to the water. And the smartest fish are those who head for the deep when they spot hunters who sight in this direction.
Since refraction of light occurs when it crosses the boundary, visual distortions often occur. These distortions occur when light changes medium as it travels from the object to our eyes. | <urn:uuid:f573244e-5ac3-4fed-b8f9-567bac22c4bf> | 4.09375 | 1,417 | Tutorial | Science & Tech. | 58.77676 |
Copyright: This document has been placed in the Public Domain.
Many thanks to Bill Baxter, Jarrett Billingsley, Anders F Björklund, Lutger Blijdestijn, Thomas Kuehne, Pierre Rouleau and Max Samuha for their input, and to Walter Bright for making such a great language.
One of the great features of D is its’ fantastic support for text. However, many people new to D have trouble understanding why things are the way they are. People coming from a C or C++ background are quickly confused by the fact that char does not appear to work the way they expect it to, whilst people coming from a Java, C# or interpreted language background wonder why D has three different character types, and no string class.
This article will hopefully address these questions, and help explain the how and why of text in D. But first, some background.
Back when C was created, the dominant character encoding in use was ASCII. ASCII was cool because it could encode every letter of the western alphabet, numbers, and a whole bunch of punctuation. If you needed more characters, then by golly you could just stick them in the upper 128 fields as an extension to ASCII.
This led to the rather unfortunate mess that are character encodings. They arose out of the impossibility of fitting every language’s symbols into just 128 characters. Things became worse with multi byte character sets like Shift_JIS where you couldn’t even count on each 8-bit code being an actual symbol. You also had to carry around a description of which code page you were using. It only got worse if you wanted to use multiple character encodings in a single text document: you usually can’t.
In the end, this led to the creation of Unicode; a character encoding to replace all other character encodings. Unicode significantly differs from most other character encodings in that it encodes every one of its’ symbols using a unique integer identifier called a code point. For example, the N-ary summation symbol “∑” is identified in Unicode as code point 0x2211. By contrast, this symbol is not defined in most character encodings, usually because there simply isn’t room.
However, Unicode by itself does not specify how to actually store these code points; it merely defines what they mean. This is where the Unicode Transformation Formats come in to play.
UTF-32 is the easiest to understand. Every Unicode code point is stored literally as a 32-bit unsigned integer. The obvious disadvantage to this is that it requires a large amount of space to store even the simplest of text.
UTF-16 is somewhat more complex. As the name suggests, it is based around 16-bit unsigned integers. However, since you cannot represent every Unicode code point with only 16-bits, it uses variable length encoding to make sure you can store any code point you please. Most normal code points will only use a single 16-bit value, with more uncommon code points taking up two. Each of these 16-bit values is called a “code unit.”
UTF-8 can be thought of as an “extension” of UTF-16 in that it uses a similar variable length encoding scheme based on 8-bit integers. Code points that fall into the traditional ASCII range remain exactly the same (meaning ASCII is effectively a subset of UTF-8), with other code points taking somewhere between 2 and 4 bytes (aka: code units) to store.
So, by now, you’re probably thinking “what a complete and total mess!” To a degree it is, but it’s important to realise that this is a huge simplification of how things used to be. What’s important to take from all this is that there are three distinct ways of representing Unicode text, and all three are supported directly in D.
Unlike C which says nothing on, for example, how to store Japanese text, D is designed to use Unicode internally for all text storage. This means that instead of having to support multiple character encodings in your programs, you only need to support one, possibly using a library to convert to and from Unicode as necessary.
Specifically, here is how the various encodings translate to D types:
- char is a UTF-8 code unit,
- wchar is a UTF-16 code unit,
- dchar is a UTF-32 code point,
- char is a UTF-8 string,
- wchar is a UTF-16 string and
- dchar is a UTF-32 string.
The first thing that trips up people new to D is that the following program works:
But this one doesn’t:
It simply crashes out with an error saying something about “invalid UTF sequence.” Many people see this and wonder what’s going on.
The answer is something like this: remember how UTF-8 encodes code points using somewhere between one and four individual code units? Well, in D, a char is only a single UTF-8 code unit, so it cannot contain all possible code points. The problem is that “є” requires two code units to represent; it is actually stored as "\xD1\x94".
So when the program comes to print out the second “character,” the standard library throws up the red flag saying “wait a second, 0xD1 isn’t a valid UTF-8 sequence; you can’t print that!” You’re basically trying to write out half a code point, which really doesn’t make any sense.
Is the standard library at fault? Not really; you don’t exactly want to be outputting incomplete code points, otherwise other programs could choke on your output. You certainly wouldn’t appreciate being fed garbage text.
The way to fix this is to realise that you’re using the wrong type for the job. Remember, a single char cannot possibly hold all valid code points. What you need to do is use a type which can:
The above code works perfectly, since the foreach loop is smart enough to decode a single complete code point at a time.
The second problem comes up when programmers discover the power of D’s arrays. They see things like the built-in length property and slicing and think “cool; I can use those on strings!”
When their code fails miserably on international text, they wonder just what’s gone wrong. The problem is, once again, that UTF-8 and UTF-16 don’t necessarily store a single code point in a single code unit. For example, if we are using UTF-8,
does not give you “є”. It gives you "\xD1" which isn’t what you really wanted. Similarly,
gives you “єll” and not “єllѲ” as you would expect (since the “є” actually takes up two chars.) The reason for this is that decoding a UTF-8 or UTF-16 stream is all well and good, but trying to decode a slice in the middle is difficult to do efficiently.
Similarly, the length property of a UTF-8 or UTF-16 string can be misleading; it is counting the number of code units, not the number of actual code points.
The simplest way to deal with this is to stick to UTF-32 strings (aka: dchar) if you’re going to be doing a lot of indexing or slicing. This is because they do not suffer from these variable length encoding problems. Another possible way to do this is to use a foreach loop to convert your string into individual code points, and manually extract the slice you want as you go.
The std.utf module provides many functions which you might find useful:
- std.utf.toUTF8(s) – converts s from any UTF encoding to UTF-8, and returns the result.
- std.utf.toUTF16(s) – as above, but for UTF-16.
- std.utf.toUTF32(s) – as above, but for UTF-32.
Another trick to keep in mind is that when using foreach, you can also ask it to give you the index of each code point within the string:
The above code produces the following output (assuming your terminal can display UTF-8):
Note that the index is that of the first code unit for that code point. These indices can be used in slicing operations to ensure you get a valid UTF sequence.
This is an area of active discussion. Many people assert that D needs a string class, whilst others say that it is unnecessary. Instead of trying to convince you either way, I’ll just explain why D doesn’t have a string class, and show what you can do without one.
An important thing to remember is that C++ grew a string class because C’s string handling was so incredibly painful. Java has a string class because Java is object-oriented to the extreme, and it makes sense to have one.
On the other hand, D does many of the things that C++ needed the string class for quite nicely by itself:
- Since all strings are arrays, all strings have a length property, meaning you don’t need a function to go looking for the end of a string.
- Strings can also be trivially concatenated together using the concatenation operator ~.
- Slicing works as expected for UTF-32 strings, and in UTF-8 and UTF-16 strings as long as you slice on known code point positions.
can be rewritten as:
Which means that although you don’t have a string class, you can “fake” it, by simply writing functions that take strings as their first argument; you aren’t even limited to what comes in the standard library, unlike in C++ and Java!
For a full list of what string manipulation functions come with D, take a look at http://www.digitalmars.com/d/phobos/std_string.html.
If you really, really can’t live without the warm comforting embrace of a string class, you can find a good one at http://www.dprogramming.com/dstring.php.
By now you should understand the problems that arise because of D’s use of UTF encodings. However, there is another problem that comes about because of how D represents arrays.
Back before D had the std.stdio.writefln method, most examples used the old C function printf. This worked fine until you tried to output a string:
Statements like the above are very likely to print out garbage, which leaves many people scratching their heads. The reason is that C uses NUL-terminated strings, whereas D uses true arrays. In other words:
- Strings in C are a pointer to the first character. A string ends at the first NUL character.
- Strings in D are a pointer to the first code unit, followed by a length. There is no terminator.
Thankfully, there is an easy solution:
The std.string.toStringz function converts any char string to a C-compatible char* string by ensuring that there is a terminating NUL.
So you’ve been clever and added some nifty symbols into your source file using Unicode, only to have the compiler barf on them. “What's wrong?” I hear you ask; “I thought D supported Unicode source!”
In fact, it does. There are two problems you might run into:
- The editor you used may support Unicode, but didn't end up saving in it. Go back and double-check that the file really is Unicode. How you do this depends on your editor, but there's usually an option lying around somewhere to set a file's character encoding.
- The other is a bit obscure: if you save your source file in Unicode without a Byte Order Mark and the first character is outside the ASCII character range, D won't be able to read it properly.
Use an editor that properly supports UTF. Seriously, even Windows Notepad does it correctly!
Yes, it can. D source files support four character encodings: ASCII, UTF-8, UTF-16 and UTF-32. Provided your source file is saved in one of these encodings, you can include any character you like.
Of course, this requires that you use an editor that properly supports UTF; as stated above, using an editor that incorrectly writes out UTF files can cause the D compiler to choke on your source files.
There are two ways to do this:
- Enter the characters you want directly, and save the source file in one of the UTF encodings.
- Find out what the code point for the symbol you want to use is, and then manually enter it into the string literal using \uXXXX for code points 0xFFFF and below, or \UXXXXXXXX if they don't fit in the first form. Remember, each X is a hexadecimal digit.
You can store ASCII text directly using char strings. Remember, ASCII is a subset of UTF-8, which means that all ASCII strings are valid UTF-8 strings.
You can use pretty much any character allowed in C99. This boils down to any of the following:
- underscore (_),
- code points greater than or equal to \u00A0 and less than \uD800 and
- code points greater than \uDFFF.
- \u0024 ($),
- \u0040 (@) and
- \u0060 (`).
For that, you will need to use a ubyte array. You should not use char for this purpose, since char is supposed to contain UTF-8 strings, and other encodings more than likely aren't valid UTF-8 strings.
To convert between Unicode and your chosen code page, you will want to use a library designed to do this: iconv < http://www.gnu.org/software/libiconv/ > is a popular open source library for code page conversions.
On windows, you can look in std.windows.charset, functions toMBSz() and fromMBSz() for converting to/from Win-ANSI/Oem? encodings.
Not directly. You can either roll your own system, or use an existing library like gettext < http://www.gnu.org/software/gettext/ > to do this.
This one’s tricky to answer.
For most cases, char is more than sufficient. It’s also usually the most succinct encoding for Unicode text. Problems only really arise when you need to look at a string's length or do indexing/slicing on fixed locations.
The first problem (getting the length) can be solved by using a function like the following:
This will give you the correct answer. The second problem’s a little trickier. First of all, it’s important to realise that you can slice a UTF-8 or UTF-16 string: you just need to make sure you're not slicing in the middle of a code sequence. For example:
Works just fine since the find function returns the code unit index, and not the code point index. What you need to be careful of is code like this:
This doesn't work because ‘ö’ requires two UTF-8 code units to encode. Currently, there is no function in the standard library for extracting the nth character from a string, however you can use something like this:
Once you take care of those two problems, aside from things like the system API or what kind of text you're storing, it doesn't really matter which encoding you use.
It is a bit, actually. Here's a fast version written by Derek Parnell and Frits van Bommel that supports any given string type passed to it (not just char.)
See the newsgroup thread starting at http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=7444.
Here's the long and short of it:
- Windows: ASCII for old Win9x APIs, UTF-16 for WinNT? APIs. You can tell the difference because ASCII APIs have a trailing 'A' on their name, whilst UTF-16 APIs have a trailing 'W'. For example: GetCommandLineA? and GetCommandLineW?.
- Linux: Depends on what you're calling, how it was compiled, system (locale) settings, etc. Best to read the documentation.
- Mac OSX: Usually UTF-8, some old-old-old functions may expect MacRoman? (yuck!). Be careful with filenames though, becase they allow only specific normalized subset of UTF-8 (you can read them as UTF-8, but you can't use any UTF-8 as filename unless you normalize it). http://developer.apple.com/qa/qa2001/qa1173.html
So here’s the short and sweet on text in D:
- char is a UTF-8 code unit, and may not be a complete code point.
- wchar is a UTF-16 code unit, and may not be a complete code point.
- dchar is a UTF-32 code unit, which is guaranteed to be a complete code point.
- char is a UTF-8 string, and uses one to four bytes per code point.
- wchar is a UTF-16 string, and uses two to four bytes per code point.
- dchar is a UTF-32 string and uses four bytes per code point.
- Outputting an incomplete UTF-8 or UTF-16 sequence will result in an error.
- You cannot reliably index or slice a UTF-8 or UTF-16 string due to variable-length encoding.
- The length property of a char or wchar array is the number of code units, not code points.
- Strings destined for a C function that expects NUL-terminated strings need to be passed through std.string.toStringz first (or manually make sure the NUL-terminator exists).
This version was manually transcribed from the original, and so there may be a few formatting errors.
If you update this document, please inform the original author. | <urn:uuid:8c26b6c4-f47b-44dd-adb5-553017cb9d24> | 3.4375 | 3,926 | Documentation | Software Dev. | 65.643465 |
Dr. James McClintock, a renowned University of Alabama-Birmingham marine biologist who has conducted research in Antarctica for more than 25 years, told me the following story.
"You work in a scientific lab in the quietest place on Earth - Antarctica.
"There's a crack! Boom!
"You rush to the window of your remote lab with a number of your fellow scientists, and you witness a glacier 'calving' a chunk of ice the size of a house into the water. Adrenaline permeates the room.
"Ten years ago, that exciting and incredible sight would happen about once a week. It was an event. Something rare.
"Today, at that same lab in Antarctica, the calving glacial ice, the explosive sounds, are a daily occurrence.
"The scientists are almost 'ho-hum' about it, barely lifting their heads to recognize the melting ice.''
Such is life in a warming world.
McClintock has spent most of his life searching the ends of the earth for a cure for cancer and other human diseases. In fact, his research team has discovered marine species in the Antarctic that produce compounds active against skin cancer and influenza.
McClintock is not an alarmist. He does not have a political agenda. But he knows firsthand the earth is warming and he understands some of the consequences. Mid-winter temperatures on the Antarctic Peninsula where he works are 10 degrees Fahrenheit warmer than they were 60 years ago. That may not seem like a big difference to us non-scientists, but it's devastating to a delicate polar ecosystem (and other ecosystems).
In fact, this spring, McClintock and his research associates documented an invasion of king crabs that are likely to endanger fragile Antarctic clams, snails and brittlestars, or perhaps even the sea squirts that he and his colleagues study that could unlock a cure for skin cancer. This new predator, with its crushing claws, is moving in because of the rapidly warming seas. Once they make their way up onto the Antarctic shelf, an archaic marine ecosystem that has been without crushing predators for millennia will find itself largely defenseless. King crabs could very well destroy McClintock's living lab. For McClintock, it's like discovering someone is about to burn down your home and your life's work and possessions.
I have always believed the National Academies of Science and the National Research Council motto, "Where the nation turns for independent and expert advice,'' accurately portrays that most venerable institution. As a nation, we have been seeking their advice since President Lincoln established this scientific body in 1863. Last month, without much fanfare, and little to no attention from the national media, the National Academies released their latest congressionally requested report on climate change.
The report, "America's Choices,'' does not pull any punches. It reaffirms that climate change is occurring now and that the most effective strategy to combat it would be to begin cutting greenhouse gas emissions immediately.
What makes this report more shocking is the fact that it is not new. As far back as 2005, the National Academies of the U.S., France, Canada, the United Kingdom, India, Italy, Japan, Germany, Brazil and China have jointly called upon policymakers throughout the world to address climate change.
The message from the National Academies six years ago was virtually identical to the one in 2011. Climate change is real. We need to drastically reduce greenhouse emissions. We need to aggressively seek technological and scientific solutions. Delaying will only make matters worse.
And now, more than ever, the signs of climate change are becoming starker. The extreme weather and floods in the Midwest and South this spring, historical droughts and fires in Texas and Arizona, permafrost disappearing in Russia and Siberia, floods in Pakistan, massive drought followed by flooding in Australia and whole villages in Alaska disappearing because of sea level rise are just a few recent examples.
The climate is changing so rapidly that the Arbor Day Foundation has changed its recommendations for when and where you should plant your trees.
Are we going to follow the National Academy of Sciences and countless scientists' advice on climate change? Are we going to listen to Dr. James McClintock and try to save a place that can lead to cures for cancer? Or are we going to barely lift our heads and refuse to recognize the climate changing around us?
Byington is publisher of Bama Environmental News. He is a longtime environmental advocate from Birmingham, Ala., who has served on numerous state and national environmental boards. | <urn:uuid:e3719562-5a0a-40ad-8e62-37bffdd44b6e> | 2.78125 | 935 | Nonfiction Writing | Science & Tech. | 44.132143 |
Just three Latin words unlock the meanings of most cloud names: Stratus meaning layer; cumulus, the word for lump or heap; and cirrus, which means wispy or curly. Add to this basic group the word nimbus, which means 'pouring down rain,' alto, the word meaning middle, and fracto for broken and you've got almost the entire sky covered.
Stratocumulus? That's easy - a layer of lumpy clouds. Cirrostratus - a wispy, curly layer of clouds. Cumulo-nimbus - big lumpy clouds that can pour down rain. How about fractostratus - a smooth layer of clouds that looks sort of torn apart.
Our system of cloud names was created by an English pharmacist named Luke Howard back in 1803. Though it has been refined and expanded over the years by various meteorologists, Howard's basic nomenclature remains in use today.
A modest man of science and a dedicated amateur weather observer, Howard was also evidently something of a poet, for the Latin names he proposed for the clouds have proven to be as memorable, as apt, and as seemingly inevitable as some of the great lines of Shakespeare. Luke Howard's latin cloud names. Nearly 200 years old, and unlike the latin names of plants and animals, have not been superceded by a non-latin moniker.
Thanks today to writer David Laskin. Our show is funded by Subaru and by the National Science Foundation. | <urn:uuid:6654aabd-6844-42a1-aa27-240393908739> | 3.453125 | 313 | Audio Transcript | Science & Tech. | 56.412175 |
Galileo Finds Veritable Chemical Factory On Europa
News story originally written on March 29, 1999
Scientists using instruments aboard the Galileo spacecraft have found
hydrogen peroxide on Jupiter's moon Europa
. This is added to the list
of chemicals such as sulfur dioxide, water ice, and carbon dioxide that
have already been discovered there.
The hydrogen peroxide is created by the intense radiation coming from
Jupiter. Hydrogen peroxide isn't found naturally on Earth's surface
because we aren't hit by as much radiation as Europa.
Shop Windows to the Universe Science Store!
Learn about Earth and space science, and have fun while doing it! The games
section of our online store
includes a climate change card game
and the Traveling Nitrogen game
You might also be interested in:
Europa was first discovered by Galileo in 1610, making it one of the Galilean Satellites. It is Jupiter's 4th largest moon, 670,900 km from Jupiter. With a diameter that is about half the distance across...more
The picture to the left shows examples of the many amazing different surface features of Europa. Many exciting discoveries were made about Europa during the Galileo mission. The surface of Europa is unusual,...more
It was another exciting and frustrating year for the space science program. It seemed that every step forward led to one backwards. Either way, NASA led the way to a great century of discovery. Unfortunately,...more
The Space Shuttle Discovery lifted off from Kennedy Space Center on October 29th at 2:19 p.m. EST. The weather was great as Discovery took 8 1/2 minutes to reach orbit. This was the United States' 123rd...more
A moon was discovered orbiting the asteroid, Eugenia. This is only the second time in history that a satellite has been seen circling an asteroid. A special mirror allowed scientists to find the moon...more
Will Russia ever put the service module for the International Space Station in space? NASA officials want an answer from the Russian government. The necessary service module is currently waiting to be...more
A coronal mass ejection (CME) happened on the Sun early last month. The material that was thrown out from this explosion passed the ACE spacecraft. The SWICS instrument on ACE has produced a new and very...more | <urn:uuid:da12cf53-daa9-4ff6-8f4d-b844e1254f90> | 3.15625 | 476 | Content Listing | Science & Tech. | 50.005108 |
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.
May 26, 1998
Explanation: Isn't the Sun round? Yes, but in the above picture, the Earth's atmosphere makes it appear almost square. Here a layer of air near the Earth was so warm it acted like a giant lens, creating increasingly distorted paths for sunlight to reach the camera. Similarly, on a long flat highway, it may appear that the road in the distance is covered with water. In this case, light from the blue sky is being unusually refracted by warm air just above the dry road. No matter how the Earth's atmosphere makes the Sun appear, the Sun will always be spherical. This setting Sun was photographed over Lake Michigan in Muskegon, MI.
Authors & editors:
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U. | <urn:uuid:e6393952-ed60-4e2f-8be1-a3148fd67144> | 3.375 | 210 | Knowledge Article | Science & Tech. | 58.759634 |
The manmade changes pushing the planet toward a critical transition
Nature changes gradually—until it doesn’t. As the changes in an ecosystem pile up, they can push the system past a “critical threshold,” and then the change can become extremely fast (in relation to geological timescales) and unstoppable. And in a review in the journal Nature, researchers suggest that the same thing is happening to the whole world: Humans could be driving Earth’s biosphere towards a tipping point beyond which the planet’s ecosystems will collapse abruptly and irreversibly.
This global ecosystem collapse has occurred before, most recently about 12,000 years ago with the last transition from a glacial period to the current interglacial (i.e., warm) period, say the review authors. Over the relatively short period of 1,000 years, fluctuations in the Earth’s climate largely killed off about half the large mammal species, along with birds, reptiles, and a few smaller mammal species. The millennium-long shift was triggered by rapid global warming, and once this warming pushed the planet past its tipping point, the end of the 100,000-year-old ice age became inevitable, giving way to the current 11,000-year-old interglacial era. | <urn:uuid:082ad00c-9939-40e5-bdcb-ef0b369ed52a> | 3.6875 | 263 | Truncated | Science & Tech. | 41.051789 |
People and other living beings depend on natural resources for food, shelter, and protection, as well as for generating energy and all the products we manufacture. With current consumption patterns, people are using these resources at an unsustainable rate. Many resources are at risk of becoming depleted.
The U.S. has about 5 percent of the world's population, but accounts for about 40 percent of the world's resources consumption (U.N. Human Development Report). If everyone lived like the average North American, the combined "ecological footprint" — the land and resources needed to support humanity — would be at least five Earths. Developed nations have by far the biggest global impact, but developing nations also experience strain on local environments and their limited resources.
Fossil fuels, groundwater, forests, minerals, cropland soils, marine fisheries, and other natural resources are being depleted much more quickly than they can be replenished. Resources are also under pressure for other reasons, such as climate change leading to the melting of the Himalayan glaciers that are the source of major Asian rivers. As resources dwindle, the likelihood of resource wars increases (Shah, "Human Population").
We are living well beyond the Earth's carrying capacity, a measure of the number of people and the kinds of activities that the environment can sustain indefinitely. Overconsumption — taking more than than the Earth can provide — is threatening sustainability.
Schooling for sustainability includes everything from learning from the school's efforts to conserve resources to studying the global patterns that tax the planet's capacity.
References cited in this article may be found in "References" in the Resources page of our website. | <urn:uuid:6e8d5e4d-a641-4ff5-aede-f7d38374f40b> | 3.8125 | 335 | Knowledge Article | Science & Tech. | 32.068728 |
A whispering gallery is usually a circular, hemispherical, elliptical or ellipsoidal enclosure, often beneath a dome or a vault, in which whispers can be heard clearly in other parts of the gallery. Such galleries can also be set up using two parabolic dishes. Sometimes the phenomenon is detected in caves.
A whispering gallery is most simply constructed in the form of a circular wall, and allows whispered communication from any part of the internal side of the circumference to any other part. The sound is carried by waves, known as whispering-gallery waves, that travel around the circumference clinging to the walls, an effect that was discovered in the whispering gallery of St Paul's Cathedral in London. The extent to which the sound travels at St Paul's can also be judged by clapping in the gallery, which produces four echoes. Other historical examples are the Gol Gumbaz mausoleum in Bijapur and the Echo Wall of the Temple of Heaven in Beijing. A hemispherical enclosure will also guide whispering gallery waves.
The gallery may also be in the form of an ellipse or ellipsoid, with an accessible point at each focus. In this case, when a visitor stands at one focus and whispers, the line of sound emanating from this focus reflects directly to the focus at the other end of the gallery, where the whispers may be heard. In a similar way, two large concave parabolic dishes, serving as acoustic mirrors, may be erected facing each other in a room or outdoors to serve as a whispering gallery, a common feature of science museums. Egg-shaped galleries, such as the Golghar Granary at Bankipore, and irregularly shaped smooth-walled galleries in the form of caves, such as the Ear of Dionysius in Syracuse, also exist.
||This section needs additional citations for verification. (January 2012)|
United Kingdom
- St Paul's Cathedral in London is the place where whispering-gallery waves were first discovered by Lord Rayleigh c. 1878.
- The library of Dollar Academy in Scotland.
- The entrance gallery of the Aston Webb Great Hall at the University of Birmingham.
United States
- The Battle House Hotel in Mobile, Alabama has a whispering arch in the front lobby.
- Cincinnati Museum Center at Union Terminal.
- Grand Central Terminal in New York City — the gallery in front of the Oyster Bar restaurant.
- The Mapparium at The Mary Baker Eddy Library in Boston allows visitors to enter the interior of a reflecting surface forming a nearly complete sphere.
- A whispering gallery can be found on the main floor of the Museum of Science and Industry (Chicago).
- Statuary Hall in the United States Capitol.
- Salt Lake Tabernacle in Salt Lake City, Utah.
- The rotunda at San Francisco's City Hall.
- Curved stone benches on either side of the Smith Memorial Arch in Fairmount Park.
- Centennial fountain in front of Green Library at Stanford University in California
- The rotunda of the Texas Capitol and the Missouri State Capitol.
Rest of the world
- Barossa Reservoir, Williamstown, South Australia.
- Cathedral of Brasília in Brazil.
- Martello towers.
- The Echo Wall in the Temple of Heaven in Beijing.
- The Gol Gumbaz in Bijapur, India.
- The Golghar Granary in Bankipore, India.
- The Victoria Memorial in Kolkata.
- Masjed-e Imam in Esfahān, Iran.
- Basilica of St. John Lateran, Rome.
- Santa Maria del Fiore, Florence Cathedral.
- The Church of the Holy Sepulcher, Jerusalem.
- Leaning Tower of Nevyansk, Sverdlovsk Oblast.
- Selimiye Mosque in Edirne, Turkey.
- St. Peter's Basilica in the Vatican City.
- Monument to the Negev Brigade in Beersheba, Israel.
- The Salle de Cariatides in the Louvre, Paris, France.
- The Treasury of Atreus, Greece
- Secret's Chamber in El Escorial in Madrid, Spain.
- The Whispering Gallery in the Alhambra in Granada, Spain.
- Cleopatra's Bath in the Siwa Oasis, Egypt.
- Ear of Dionysius cave in Syracuse, Sicily.
- Meštrović Pavilion in Zagreb, Croatia
See also
- Lord Rayleigh, The problem of the whispering gallery, Philos. Mag. 20, 1001,1910.
- O. Wright, Gallery of Whispers, Physics World 25, No. 2, Feb. 2012, p. 31.
- C. K. Raman, On whispering galleries, Proc. Indian Ass. Cult. Sci. 7, 159, 1921-1922.
- W. C. Sabine, Collected Papers on Acoustics (Harvard University Press, Cambridge MA) 1922, p. 255.
- Peiping (American National Red Cross, American Red Cross Embassy Club) 1946, p. 17.
- Lord Rayleigh, Theory of Sound, vol. II, 1st edition, (London, MacMillan), 1878. | <urn:uuid:f53e0151-721e-4b72-9a2e-414aac8f2f82> | 3.484375 | 1,108 | Knowledge Article | Science & Tech. | 50.96221 |
Why wait (), notify () and notifyAll () must be called from synchronized block or method in Java
Most of Java developer knows that wait() ,notify() and notifyAll() method of object class must have to be called inside synchronized method or synchronized block in Java but how many times we thought why ? Recently this questions was asked to in Java interview to one of my friend, he pondered for a moment and replied that if we don't call wait () or notify () method from synchronized context we will receive IllegalMonitorStateException in java. He was right in terms of behavior of language but as per him interviewer was not completely satisfied with the answer and wanted to explain more about it. After the interview he discussed the same questions with me and I thought he might have told about race condition between wait () and notify () in Java that could exists if we don't call them inside synchronized method or block. Let’s see how it could happen:
We use wait () and notify () or notifyAll () method mostly for inter-thread communication. One thread is waiting after checking a condition e.g. In Producer Consumer example Producer Thread is waiting if buffer is full and Consumer thread notify Producer thread after he creates a space in buffer by consuming an element. calling notify() or notifyAll() issues a notification to a single or multiple thread that a condition has changed and once notification thread leaves synchronized block , all the threads which are waiting fight for object lock on which they are waiting and lucky thread returns from wait() method after reacquiring the lock and proceed further. Let’s divide this whole operation in steps to see a possibility of race condition between wait () and notify () method in Java, we will use Produce Consumer thread example to understand the scenario better:
1. The Producer thread tests the condition (buffer is full or not) and confirms that it must wait (after finding buffer is full).
2. The Consumer thread sets the condition after consuming an element from buffer.
3. The Consumer thread calls the notify () method; this goes unheard since the Producer thread is not yet waiting.
4. The Producer thread calls the wait () method and goes into waiting state.
So due to race condition here we potential lost a notification and if we use buffer or just one element Produce thread will be waiting forever and your program will hang.
Now let's think how does this potential race condition get resolved? This race condition is resolved by using synchronized keyword and locking provided by java. In order to call the wait (), notify () or notifyAll () methods in Java, we must have obtained the lock for the object on which we're calling the method. Since the wait () method in Java also releases the lock prior to waiting and reacquires the lock prior to returning from the wait () method, we must use this lock to ensure that checking the condition (buffer is full or not) and setting the condition (taking element from buffer) is atomic which can be achieved by using synchronized method or block in Java.
I am not sure if this is what interviewer was actually expecting but this what I thought would at least make sense, please correct me If I wrong and let us know if there is any other convincing reason of calling wait(), notify() or notifyAll method in Java.
Just to summarize we call wait (), notify () or notifyAll method in Java from synchronized method or synchronized block in Java to avoid:
1) IllegalMonitorStateException in Java which will occur if we don't call wait (), notify () or notifyAll () method from synchronized context.
2) Any potential race condition between wait and notify method in Java.Some of my other favorite interview discussions are Why String is immutable or final in Java, how HashMap works in Java and what are differences between HashMap and hashtable in Java is. | <urn:uuid:86f8b432-2bb3-48d1-af4d-d4d85a904118> | 3.671875 | 774 | Personal Blog | Software Dev. | 41.163405 |
Your estimates are not scale invariant, so I am trying to guess what you want from the picture.
A closed geodesic cuts your surface into two discs. Both have geodesic as a boundary, positive curvature and area $\le$ than area of your original surface. If geodesic is long, then (with the intrinsic metric) these discs look almost like segments. It has to have curvature near $\pi$ in concentrated form near the ends.
Thus if long geodesic exist then almost all curvature can be covered by 4 fingers on your surface...
- you can not have it if Gauss curvature $\ge 1$. (in In this case you can still have long shapes).shapes: say a doubling of a slice of unit shpere between meridians can be embedded into $\mathbb R^3$ as a convex surface, one can smooth singularities on the poles.)
- you can not have it on a polyhedral surface with more than 4 vertexes. If you have it for an arbitrary long simple geodesics on the surface of tetrahedral, the sum of angles around the vertexes each vertex has to be $=\pi$. | <urn:uuid:bbdaa247-b383-4d03-ac96-36887f2e0b44> | 2.734375 | 248 | Q&A Forum | Science & Tech. | 57.357967 |
Return to Physics Index
Monegain, Louise J. Park Manor
1) Students will learn basic understanding of inertia.
2) Students will demonstrate some activities illustrating inertia.
3) Students will develop a basic understanding of Newton's laws of motion.
Balls various sizes, pie pans with one fourth slice removed, pennies, heavy paper
circle, checkers, skate board, stuffed animal, glass, two eggs (one boiled, one raw),
cloth napkin, glass of water and straws.
Students should have prior knowledge of speed, force, acceleration, gravity and
friction. Demonstrate inertia by snatching a cloth napkin from under a glass of
water, and a paper circle from under a checker so that the checker falls into the
glass and spinning the two eggs. Group students into cooperative groupings to carry
out the following activities:
Activity 1 - Place a ball in the pie pan and spin the ball. Repeat this activity
using two balls of different mass.
Activity 2 - Put a ball in motion and try to blow it off of its path with a straw.
Repeat this activity using balls of various masses.
Activity 3 - Stack five checkers one on top of the other. Using your fore-finger
flick another checker sharply against the bottom checker of the stack to move it from
pile keeping pile undisturbed.
Discuss Newton's first law of motion with students. Have students answer these three
questions: 1) How does the pie pan and ball activity help prove the first law of
motion? 2) Which ball was the hardest to move off of the straight path? 3) Does
inertia increase with mass? | <urn:uuid:36e6f5ef-921e-4991-8a06-69f079752c70> | 4.3125 | 354 | Tutorial | Science & Tech. | 57.706937 |
[en] The efficiency of the transmission of surface plasmon waves by use of a dielectric diffraction grating is discussed. The Kretschmann device allows us to obtain a surface plasmon resonance that consists of an absorption peak in the reflection spectrum. When surface plasmon resonance occurs, the TM-polarization mode of the incident electromagnetic wave is neither transmitted nor reflected. The procedure to transform an absorption peak into a transmission peak is described. Transmittivity of 68% is obtained for a simple structure that consists of a thin-film layer of Ag coated on a volume diffraction grating and embedded between two dielectric media. The results presented herein were obtained by numerical simulations that were carried out by use of an algorithm based on the rigorous coupled-wave theory.
Service de Physique Générale, Hololab
Fonds pour la formation à la Recherche dans l'Industrie et dans l'Agriculture (Communauté française de Belgique) - FRIA | <urn:uuid:abf25383-07bd-4879-8bed-60a2b7af74d1> | 2.78125 | 214 | Academic Writing | Science & Tech. | 21.615337 |
I love classic sci fi movies, but if some advanced alien being could make the whole Earth (as opposed to just the man-made parts) literally stand still, the end results would be nothing short of catastrophic.
You see, because most of Earth’s surface is covered with water, that water is hugely affected by the motion of our planet; Earth’s rotation has a potent effect on the way that water is distributed across our planet’s surface. Succinctly, Earth looks the way it does because of centrifugal force.
According to geophysicist Witold Fraczek, this is how our world would look if it were completely stationary. A huge band of dry land across the planet’s surface, with two vast polar oceans. The full details are available on ESRI, and are really quite fascinating.
Some part of me has to wonder how things might fare in the long term if such a bizarre fate were to somehow befall our world. After all, one of the biggest differences between Earth and Venus is the fact that our sister world has a greatly slower rotation rate…
With a tip of the centrifuge to io9!
Image credit: Witold Fraczek, Esri | <urn:uuid:e9fb9166-bf59-4a4d-a97a-a3a2ae76a15a> | 3.4375 | 252 | Personal Blog | Science & Tech. | 47.550114 |
Green Tree Ant
A Green Tree Ant worker adopts an aggressive stance as it defends the nest.
A Green Tree Ant nest in the foliage of a tree.
An adult Moth Butterfly, Liphyra brassolis. The caterpillars of this butterfly live only inside Green Tree Ant nests where they feed on ant larvae and pupae.
Green Tree Ants, sometimes called Weaver Ants, build balloon-shaped nests among the foliage of trees and shrubs. Groups of workers pull leaves close to each other and 'weave' them together with silk produced by the larvae. A Green Tree Ant colony may consist of many nests spread over several trees but there is only a single queen.
Green Tree Ants occur across northern Australia from the Kimberly region in Western Australia to about Gladstone in Queensland. They are found in all forest types but do not occur in the highlands. Green Tree Ant workers are aggressive and defend their nests by swarming onto the attacker. They cannot sting but bite with their jaws and squirt a burning fluid from the tip of the abdomen onto the wound. Green Tree Ants are predators and also collect honeydew from sap-sucking insects.
The caterpillars of many species of butterflies are tended by Green Tree Ants. The flattened, armoured caterpillars of the Moth Butterfly live only inside Green Tree Ant nests where they feed on ant eggs, larvae and pupae. Adult Moth Butterflies emerge inside the nest and are attacked by the ants. They are covered with loose scales that fall out when they are grabbed by the ants. In this way the butterflies can escape the nest without being damaged.
Workers are about 5-10 mm long and yellowish-green. Workers from the same nest vary in size but all have similar body proportions. The waist has a single, relatively long segment.
Queensland Museum's Find out about... is proudly supported by the Thyne Reid Foundation and the Tim Fairfax Family Foundation. | <urn:uuid:98919a77-eced-4777-9741-acd3e17805e4> | 3.53125 | 402 | Knowledge Article | Science & Tech. | 60.853901 |
This type of image shows heat based radiation from the infrared spectrum. In other words, the warmer the surface, the more infrared radiation it emits. For a satellite image, cooler surfaces are bright and warmer surfaces are dark. Since the atmosphere cools as you increase in altitude, clouds would show up as bright areas and land surfaces as dark areas. In addition, low clouds will be more gray and higher clouds will show up more white. Tall thunderstorm clouds will show up as bright white and fog will be hard to discern from land areas. A large advantage of IR is that you can view it 24 hours a day. | <urn:uuid:2bc2e4e0-c73f-4d36-944b-09a8f26b4a58> | 3.125 | 124 | Knowledge Article | Science & Tech. | 60.908636 |
Threat of eutrophication to the Baltic Ecoregion
A widespread and persistent problem
Eutrophication it is a process where bodies of water, such as lakes, estuaries, or slow-moving streams, receive excess nutrients that stimulate excessive plant growth.
This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water. This affects the ecosystem and might change it totally.
About 80% of all nutrients in the sea come from land-based activities, including sewage, industrial and municipal waste and agricultural run-off. The rest is mainly from nitrous gasses, emitted when burning fossil fuels, from traffic, industry, power generation and heating
The Baltic Sea contains 800% more phosphorus than it did 100 years ago
There are two main nutrients causing eutrophication, nitrogen (N) and phosphorus (P). They are deposited to the sea in several different ways. In 2000, about 660,000 tonnes of nitrogen and 28,000 tonnes of phosphorus entered the Baltic Sea via rivers. The Baltic Sea now contains four times as much nitrogen and eight times as much phosphorus as it did in the early 1900s. Five large rivers – the Neva, Nemunas, Daugava,Vistula, and Oder – together account for the majority of the nutrient loads entering the Baltic Sea. Although a decline in the nutrient loading has been observed in recent years, little change in eutrophic effects has been recorded in the Baltic Sea.
The expected development of agriculture in the new EU countries around the Baltic Sea will worsen the conditions measurably if no measures are taken to reduce the harmful effects of nutrient losses.
Global warming a contributor
Global warming is also stimulating eutrophication as higher temperatures in the Baltic Sea region increases the decomposition rates of the algae, compounding the effects of the nutrients.
Ecological effects of eutrophication
The imbalance caused by the abundance of nutrients has led to numerous changes in the ecological composition and state of the Baltic Sea. Certain plants and animals thrive, enabling them to increase in number and geographic spread, frequently at the expense of other species.
Some of the negative effects of the nutrient overload of the past century are:
- excessive growth of plants and algae – there has been an increase in primary production by 30-70%. Annuals such as green and brown filamentous algae have grown at the expense of the perennial bladder wrack, which in turn has had severe impacts on the littoral ecosystem
- algal blooms, some of them even toxic, are a frequent phenomenon in the Baltic every summer
- a decrease in water transparency by 2.5-3 metres as a result of the increase in biomass, e.g. an increase in zooplankton by 25%
- changes in fish species composition. Economically less valuable freshwater fish species are thriving and cod is severely affected
- a decrease in numbers and spread of predatory fish, such as pike, in coastal waters.
The loss of ecological functions on land – the nutrient retention capacity of wetlands, floodplains, coastal lagoons and free-flowing rivers – has added substantially to the eutrophication problem. Up to 90% of wetlands in the southern part of the Baltic Sea region have been drained over the past century.
State support for drainage and regulation of rivers and the construction of dams have been the key reasons for loss of these natural features. The changes have been driven by demands for additional land for farming, protection from flooding and a growing demand for electricity. The lack of market or regulatory mechanisms for assigning value to wetland functions is a major root cause for the loss of ecological functions.
Limiting the negative impacts of eutrophication
Efforts have been made to limit the production of algae and reverse the development of a eutrophied Baltic. Major investments have been made in Waste water treatment plants and industrial production. But the main problems are now non-point sources – mainly run-off from agriculture.
Eutrophication is a process where bodies of water, such as lakes, estuaries, or slow-moving streams, receive excess nutrients that stimulate excessive plant growth.
This enhanced plant growth, often called an algal bloom, reduces dissolved oxygen in the water. This can kill other marine life which also depend on disolved oxygen in the water. | <urn:uuid:ee26e634-1fd2-43bd-894f-25a168ff7293> | 3.84375 | 896 | Knowledge Article | Science & Tech. | 33.870112 |
It sounds like the plot to a science fiction story, but new scientific research hypothesizes that "advanced dinosaurs" may have evolved on other
planets in the universe.
In his report, Breslow discusses the age-old mystery of why the building blocks of terrestrial amino acids (which make up proteins), sugars, and
the genetic materials DNA and RNA exist mainly in one orientation or shape.
I saw this and thought it was an interesting concept, one I thought about often as a child. Anyway I glimpsed the title and was a little
dissappointed. My first thought was they were claiming dinosaurs evolved and are extraterrestrials. But they are only stating two things; a 'What if?'
dinosaurs didn't die and went spaceward, and the second is that perhaps life on other planets may have their own dinosaur 'step' in evolution. Anyway,
enjoy the read and thoughts to follow.
edit on 12-4-2012 by AMANNAMEDQUEST because: (no reason given) | <urn:uuid:85914a65-a20f-45c3-aa70-d0580dbe2320> | 2.703125 | 213 | Comment Section | Science & Tech. | 47.038117 |
Rising in the dark
hours before dawn,
wandering Venus now shines
as the brilliant morning star.
Its close conjunction with the Moon on August 13 was
appreciated around planet Earth.
But skygazers in eastern Asia were also treated to
a lunar occultation,
the waning crescent Moon passing directly in front of the bright planet in
still dark skies.
This composite image constructed from frames made at 10
minute intervals follows the
(vimeo video) from above
the city lights and clouds over Taebaek, Korea.
The occultation begins near the horizon and progresses as
the pair rises.
Venus first disappears behind the Moon's sunlit crescent,
emerging before dawn from the
dark lunar limb.
Kwon, O Chul | <urn:uuid:24875a5d-047e-4eb3-94a1-626227e48c95> | 2.734375 | 167 | Truncated | Science & Tech. | 48.342572 |
Solar Neutrino Experiments
Neutrinos are ghostlike particles that were postulated by Wolfgang Pauli in 1930 on purely theoretical grounds and, until recently, were believed to have zero mass. They are thought to be produced in the nuclear reactions that provide the sun's energy. They rain down on each square inch of the earth at the rate of about 400 billion per second.
Raymond Davis Jr. started investigating neutrinos that were produced in Brookhaven's Graphite Research Reactor and at a reactor at the Savannah River Plant in South Carolina, in the 1950s. But these experiments were really the prelude to Davisís major triumph, which came in the early 1970s, when he successfully detected solar neutrinos in a new experiment based in Lead, South Dakota (image at right). See more images of the detector.
A solar neutrino was expected to produce radioactive argon when it interacts with a nucleus of chlorine. Davis developed an experiment based on this idea by placing a 100,000-gallon tank of perchloroethylene, a commonly used dry-cleaning chemical and a good source of chlorine, 4,800 feet underground in the Homestake Gold Mine in South Dakota and developing techniques for quantitatively extracting a few atoms of argon from the tank.
The chlorine target was located deep underground to protect it from cosmic rays. Also, the target had to be big because the probability of chlorine's capturing a neutrino was ten quadrillion times smaller than its capturing a neutron in a nuclear reactor. Despite these odds, Davis's experiment confirmed that the sun produces neutrinos, but only about one-third of the number of neutrinos predicted by theory could be detected.
This so-called "solar neutrino puzzle" gave birth to different experiments by scientists around the world, all working to confirm the solar neutrino deficit. First came Kamiokande in Japan, then SAGE in the former Soviet Union, GALLEX in Italy, and then Super Kamiokande. Finally, in 2001-2002, scientists working at SNO, the Sudbury Neutrino Observatory in Ontario, Canada, found strong evidence that the neutrino has the ability to oscillate, or change form, among its three known types: the electron, muon and tau neutrinos.
1967 Brookhaven National Lab press release, "Solar Energy Generation Theory Being Tested in Brookhaven Neutrino Experiment" (PDF)
1967 Brookhaven Bulletin story, "Solar Neutrinos Are Counted at Brookhaven" (PDF)
Brief video featuring comments by Ray Davis on his neutrino research. (Note: This is a streaming video file. You must have RealPlayer installed.)
A "question and answer" interview with Dr. Davis, about 9 min. (RealPlayer required.) | <urn:uuid:5293fcfb-3889-4ffc-a74f-e9824a93e7c9> | 4.25 | 591 | Knowledge Article | Science & Tech. | 35.897327 |
Photo Credit: Scott Gravette
Scientific name: Carphophis amoenus ssp.
Other name: None
Description: There are two subspecies of worm snakes, Eastern worm snake Carphophis amoenus amoenus and Midwest worm snake Carphophis amoenus helenae. Worm snakes Carphophis amoenus ssp. are small secretive snakes only reaching 13 inches in length. They have a pointed head and very noted tiny black eyes. They also have a prominent sharp tip on the tail which is probably used for digging. The color varies from a dark brown to a pinkish brown on the back and almost always with a pinkish belly. Worm snakes greatly resemble earthworms which is how they got their name.
Distribution: The range of the worm snake is from Georgia across to Louisiana north to Illinois and east to Massachusetts. They are fairly common throughout most of Alabama, though they are seldom encountered.
Habitat: Worm snakes are fossorial in nature, in other words, they spend most of their life underground. They will also burrow into rotting logs and stumps, and can often be found under rocks. Worm snakes prefer damp forested soils with abundant leaf litter. However they can be found anywhere earthworms are found including fields and backyards.
Feeding Habits: The worm snake primarily eats earthworms. They will also feed on small salamanders, slugs, snails and insect larvae.
Life History and Ecology: Worm snakes spend the majority of their life underground or beneath rocks, logs and leaf litter. Very little is known about the life history of worm snakes because of their fossorial nature. They probably breed in spring and fall. One to eight eggs are laid under rocks or logs. They hatch in approximately seven weeks. The young are about 4 inches long and become full grown in 3 years. Predators include a variety of birds, small mammals, other snakes and even large salamanders and lizards.
Mirarchi, R.E., ed. 2004. Alabama wildlife. Volume 1. A checklist of vertebrates and selected invertebrates: Aquatic mollusks, fishes, amphibians, reptiles, birds, and mammals. The University of Alabama Press. Tuscaloosa, 209 pp.
Mount, Robert H. 1975. The Reptiles and Amphibians of Alabama. Auburn Printing Company, Auburn.
Author: Jim Schrenkel, Certified Wildlife Biologist, Alabama Division of Wildlife & Freshwater Fisheries. | <urn:uuid:584e8f89-7bf8-441d-8b1a-b2ed7bda5520> | 3.265625 | 516 | Knowledge Article | Science & Tech. | 50.1941 |
The issue of global climate change was identified decades ago. In fact, it was first noted in the media in the 1930s, when a prolonged period of warm weather demanded explanation, yet interest in the matter disappeared as cooler temperatures returned. For the past decade, most experts have accepted climate change as a fact, making the issue difficult to ignore—yet many politicians, and the voters who elect them, have done exactly that. Scientists, policymakers, and others have come up with good ideas to address climate change and other energy issues including oil, transportation, and electricity policies; carbon capture and storage; and the generation of innovative energy solutions; many of the core aspects of these ideas were developed long ago. However, predictable cognitive, organizational, and political barriers prevent us from addressing energy problems despite clearly identified courses of action.
This article borrows from the “predictable surprises” framework that Harvard Business School professor Michael Watkins and I developed to explain the human failure to act in time to prevent catastrophes. It also borrows ideas from a paper on cognitive barriers to addressing climate change. To focus the discussion, I treat climate change as the exemplar energy-related problem, but the ideas presented here are relevant to the enactment of wise policies across a range of issues, some of which I also discuss to demonstrate the dynamics of these barriers.
As an example of the human failure to act in time to prevent foreseeable catastrophes, Watkins and I argue that U.S. leaders had ample warning to act in time to prevent the events of September 11. We note that the U.S. government knew that Islamic terrorists were willing to become martyrs for their cause and that their hatred and aggression toward the United States had increased throughout the 1990s. The American government knew that terrorists had bombed the World Trade Center in 1993, hijacked an Air France airplane in 1994 and attempted to turn it into a missile aimed at the Eiffel Tower, and attempted to simultaneously hijack 11 U.S. commercial airplanes over the Pacific Ocean in 1995. High-ranking government officials also knew that it was easy for passengers armed with small weapons to board commercial airplanes. In fact, this information was presented in many Government Accountability Office reports and was identified by then–Vice President Al Gore’s special commission on aviation security in 1996. Together, this information created what we called a predictable surprise, or a failure to act in time. Watkins and I argue that the failure to act in time is an unfortunately typical pattern of human behavior, one that can also be seen in the persistent failure to solve the problem of auditor independence, which contributed to the collapse of Enron, Arthur Andersen, and many other firms at the start of the millennium.
Just as our government did not know how many planes the terrorists would take over on September 11 or what their targets would be, we do not know which energy crisis looms largest or which will hit first. We can be confident, however, that many energy issues will continue to grow and that large-scale disasters will occur if we fail to act in time.
The creation and implementation of wise policy recommendations require us to anticipate resistance to change and develop strategies that can overcome these barriers. Why don’t wise leaders follow through when the expected benefits of action far outweigh the expected costs from a long-term perspective? People typically respond to this question with a single explanation, a key error when explaining events. This tendency to identify only one cause holds true for social problems ranging from poverty to homelessness to teenage pregnancy. Ann McGill of the University of Chicago’s Booth School of Business illustrates this cognitive bias by noting that people have argued endlessly over whether teenage promiscuity or lack of birth control causes teenage pregnancy, when the obvious answer is that both cause the problem. Similarly, many people seek to identify one cause of climate change when it is abundantly clear that there are multiple causes.
Enacting legislation to act in time to solve energy problems requires surmounting cognitive, organizational, and political barriers to change. Efforts targeted at just one level of response will allow crucial barriers to persist. As an example, many well-intentioned organizations focus on identifying the political barriers to enacting stronger campaign finance reform in the United States. Such efforts overlook the fact that the issue of campaign finance reform is insufficiently salient in the minds of the public, for systematic and predictable reasons. True improvements in campaign financing will require changing the way citizens think about the topic and changing the political system that continually fights against meaningful reform. And, as explored later, current campaign financing plays a role in the political barriers to change in the realm of energy.
Drawing on this broad approach to reduce barriers to solving complex problems, the remainder of the article outlines three types of barriers—cognitive, organizational, and political—that confront the enactment of wise energy recommendations. The final section moves from the identification of barriers to highlight strategies for overcoming them. | <urn:uuid:3f3fcd06-76cd-4754-972c-625ca2030beb> | 2.84375 | 995 | Academic Writing | Science & Tech. | 25.413585 |
Libraries are handled a little differently for the Java grade. Instead of compiling object code into a static or shared library, the class files are added to a jar (Java ARchive) file of the form library-name.jar.
To create or install a Java library, simply specify that you want to use the java grade, either by setting ‘GRADE=java’ in your Mmakefile, or by including ‘--java’ or ‘--grade java’ in your ‘GRADEFLAGS’, then follow the instructions as above.
Java libraries are installed to the directory prefix/lib/mercury/lib/java. To include them in a program, in addition to the instructions above, you will need to include the installed jar file in your ‘CLASSPATH’, which you can set using ‘--java-classpath jarfile’ in ‘MCFLAGS’. | <urn:uuid:39d2eade-08f8-4aef-af7f-c415fc2d91ac> | 3.125 | 199 | Tutorial | Software Dev. | 38.146767 |
The Cassini probe may have already collected data that could reveal the presence of life on Saturn's moon Enceladus, a new study argues. But mission scientists say teasing out the subtle signature of life may prove difficult.
Researchers have been fascinated with Enceladus since July 2005, when Cassini revealed a dramatic plume of ice particles and water vapour shooting out from the moon's south pole.
The plume's origin is still being debated, but some models suggest the moon holds an ocean of liquid water beneath its surface. This ocean could be a potential habitat for extraterrestrial life.
Now, a team led by Christopher McKay of NASA's Ames Research Center in Moffett Field, California, says Cassini could offer up the first evidence that life exists or once existed on the 500 km-wide moon.
Though the probe was never designed to look for life, it could do so by studying organic chemicals such as methane in the plume, the team says.
"If you think about what you need for life, you need water, energy, organic material, and you need nitrogen, and they're all coming out of the plume," McKay told New Scientist. "Here is a little world that seems to have it all."
Life could take the form of methane-producing microbes, or methanogens, similar to those that have been seen buried under kilometres of ice in Greenland.
Cassini could potentially find evidence for such life by studying the relative abundances of methane and heavier organic chemicals, such as propane and acetylene.
Organic, carbon-containing molecules, including methane, are produced in various ways.
Abiological processes include the breakup of large, complex molecules called tholins, and the chemical buildup of carbon monoxide and hydrogen into organic molecules of varying weights.
None of these abiological methods should strongly favour the formation of methane over that of heavier organic molecules, McKay's team argues. Biological processes, in contrast, should produce much higher amounts of methane than heavier organic compounds, they say.
Researchers have taken advantage of this disparity to trace the source of organic compounds on Earth. Earlier this year, it was used to rule out a biological origin for oils and gases released from the "Lost City" hydrothermal vents at the bottom of the Atlantic Ocean.
McKay and colleagues believe a similar study could be carried out on Enceladus using data from Cassini's Ion and Neutral Mass Spectrometer (INMS), which can measure the concentration of different molecules in the plume.
That hints that the moon's methane was created early on, perhaps in clouds of gas that predate the solar system.
"That doesn't mean there's not a biological signal hidden under the other stuff, but we don't have any evidence to suggest that is the case," says INMS lead scientist Hunter Waite of the Southwest Research Institute in San Antonio, Texas.
"It's not a clear-cut, hands-down winner for biology," McKay acknowledges.
To better understand what a biological signal on Enceladus might look like, McKay has reconfigured a chamber previously used to simulate conditions on Saturn's moon Titan to simulate non-biological ways of making methane and other organic molecules. The signatures could help researchers interpret Cassini's results, McKay says.
Waite says the best way to search for evidence of life may be to return to Enceladus with more sensitive instruments. In 2009, NASA will choose between two competing ideas for the next mission to the outer planets.
One mission would send two orbiters to Jupiter and its moon Europa. The other would send an orbiter to Saturn and a probe that could descend to the surface of Saturn's moon Titan. The Titan-Saturn mission would also include a number of flybys of Enceladus, Waite told New Scientist.
Journal reference: Astrobiology (vol 8, p 909)
View a slideshow of Cassini's best images, narrated by imaging team leader Carolyn Porco.
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Get To It Then
Tue Nov 04 08:39:59 GMT 2008 by Supernova
It would only be the discovery of the Century.
Not Quite Panspermia
Tue Nov 04 10:54:37 GMT 2008 by Constantino
Its Tuesday morning and im letting my imagination get carried away with itself, but what if the conditions underneath Enceladus are perfect life-starting condtions with plumes spewing out jets of "biological starter packs" that over time ended up on the friendlier earth where they were able to develop and evolve.
That's assuming that conditions on earth have never been quite right to actually start biological processes, see where I'm going with this?
Anyway I'm fairly certain my last assumption is incorrect so I will file this idea under whimsical fantasy but it is nice to think of our solar system as all connected and "one big process"
Tue Nov 04 15:32:30 GMT 2008 by Larian Lequella
I am enthralled at the innovative thinking going on here. Considering the news that I have been force-fed for nearly 2 years, and the historic events taking place at US polls, I find this to be the most awe inspiring and significant news of the day!
I've seen Dr. McKay on a few NatGeo and Discovery Channel specials as of late. Best of luck!
Constantino, no harm in that sort of speculation. I am interested in seeing what sort of actual results come through though before making any fanciful leaps of the imagination. But if your whimsical fantasy bears out, I guess we're all aliens! INS will have a heck of a time deporting us! :P
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A few years ago, I decided that I needed to know more about the history of science, so naturally I volunteered to teach the subject. In working up my lectures, I was struck with the fact that in the ancient world, astronomy reached what from a modern perspective was a much higher level of accuracy and sophistication than any other science. One obvious reason for this is that visible astronomical phenomena are much simpler and easier to study than the things we can observe on the earth’s surface. The ancients did not know it, but the earth and moon and planets all spin at nearly constant rates, and they travel in their orbits under the influence of a single dominant force, that of gravitation.
In consequence, the changes in what is seen in the sky are simple and periodic: the moon regularly waxes and wanes, the sun and moon and stars seem to revolve once a day around the celestial pole, and the sun traces a path through the same constellations of stars every year, those of the zodiac. Even with crude instruments these periodic changes could be and were studied with a fair degree of mathematical precision, much greater than was possible for things on earth like the flight of a bird or the flow of water in a river.
But there was another reason why astronomy was so prominent in ancient and medieval science. It was useful in a way that the physics and biology of the time were not. Even before history began, people must have used the apparent motion of the sun as at least a crude clock, calendar, and compass. These functions became much more precise with the introduction of what may have been the first scientific instrument, the gnomon, attributed by the Greeks variously to Anaximander or to the Babylonians.
The gnomon is simply a straight pole, set vertically in a flat, level patch of ground open to the sun’s rays. When during each day the gnomon’s shadow is shortest, that is noon. At noon, the gnomon’s shadow anywhere in the latitude of Greece or Mesopotamia points due north, so all the points of the compass can be permanently and accurately marked out on the ground around the gnomon. Watching the shadow from day to day, one can note the days when the noon shadow is shortest or longest. That is the summer or the winter solstice. From the length of the noon shadow at the summer solstice one can calculate the latitude. The shadow at sunset points somewhat south of east in the spring and summer, and somewhat north of east in the fall and winter … | <urn:uuid:3cb64f11-a3d4-471d-8b76-fd94ca6e75fa> | 3.859375 | 522 | Personal Blog | Science & Tech. | 45.616693 |
This interactive activity from NOVA scienceNOW reviews several potential means of storing carbon dioxide (CO2) captured from industrial sources. Among the featured ideas are technologies that deliver compressed CO2 to underground cavities, saline aquifers, and the deep seabed. The benefit of storing, or sequestering, captured CO2 could be significant in the fight to slow or limit global warming. However, the list of drawbacks associated with carbon sequestration includes high cost, storage capacity limitations, a still-incomplete understanding of the relevant Earth systems, and uncertainty as to whether the CO2 can be safely and permanently contained.
Through the carbon cycle, Earth captures about half of an estimated eight billion metric tons of carbon dioxide (CO2) produced annually through the combustion of fossil fuels. Land plants absorb CO2 for photosynthesis, and in the oceans, CO2 readily dissolves in seawater. Because CO2 is a greenhouse gas and contributes to global warming, the overwhelming consensus among scientists is that something must be done to remove most of what otherwise accumulates in the atmosphere or to reduce our combustion of fossil fuels in the first place.
Many technological solutions are being explored to capture CO2 either in the air or directly at an emissions source. Once collected, the gas must be safely and permanently stored to prevent its release back into the atmosphere. Before that can happen, the CO2 must be compressed. By nature, gas is expansive and more difficult to contain than a solid or liquid. Using compression, CO2 gas can be converted into a "supercritical" fluid—somewhere between a gas and a liquid state. While this is both an energy-intensive and expensive process, once complete, the reformatted CO2 can be transported to a storage facility.
Various storage solutions have been proposed, tested, and even put into limited use. They involve sites aboveground, belowground, and in the ocean. Aboveground solutions mostly rely on agricultural means to "fix" carbon in soil, while belowground solutions generally involve filling existing cavities, including depleted coal beds, oil and gas fields, or aquifers, with the fluid CO2. Ocean storage can also take many forms, including injecting CO2 deep into the seabed or stimulating growth at the surface of plankton populations, which use CO2 in photosynthesis.
While each of these options has merits, each has its drawbacks as well. Although it may be appealing to plant trees and allow vegetation to absorb CO2 for photosynthesis, when plants die, they release much of their stored carbon back into the atmosphere. Another approach, using alkaline minerals to react with the acidic CO2 to form stable carbonates, appears effective, but the process of mining to obtain these minerals would make it prohibitively expensive. And as large a potential storage capacity as the oceans offer, the effects of increased levels of CO2 on organisms, especially benthic bottom-dwellers, is largely unknown. Existing research suggests that higher ocean acidity threatens calcium carbonate, the key structural constituent of coral skeletons and mollusk shells.
Among other concerns about these technological solutions cited by both scientists and potential investors is the potential for leakages that could spoil freshwater supplies, and the inadequate storage capacity that most terrestrial solutions offer. And then there's the price: using present sequestration technologies, cost estimates range from $100 to $300 per ton of carbon emissions kept out of the atmosphere. All of this suggests that geological and ocean sequestration may only realistically represent one part of the solution to the problem—a solution that likely must also include reducing our consumption of fossil fuels.
Academic standards correlations on Teachers' Domain use the Achievement Standards Network (ASN) database of state and national standards, provided to NSDL projects courtesy of JES & Co.
We assign reference terms to each statement within a standards document and to each media resource, and correlations are based upon matches of these terms for a given grade band. If a particular standards document of interest to you is not displayed yet, it most likely has not yet been processed by ASN or by Teachers' Domain. We will be adding social studies and arts correlations over the coming year, and also will be increasing the specificity of alignment. | <urn:uuid:88a43e2e-e54d-483b-adec-27075f6d6017> | 4.25 | 861 | Knowledge Article | Science & Tech. | 22.900349 |
Need help on Arrays Urgently ???
Posted by Java_Learner (Java_Learner), 23 March 2003hi.. there. Is there any great java programmers out there who can help me on Arrays ? I am really lose in it and i am trying to create a programme using Arrays. So if anyone out there who is kind enough to help me pls reply in either this forum or emailing me thks.. my email add is email@example.com
Posted by admin (Graham Ellis), 23 March 2003I've been updating the section on Array in our Java course over the last couple of days .... here's how it starts - it may help
There will be frequent occasions when you'll want to perform the same operation on a whole series of primitives or objects one after the other, and it won't be practical to hold each in a separate named variable.
Instead of using individual variables, we'll use a whole number of variables all in one:
* We'll give the whole thing a single name
* We'll access elements by their numeric position in the table
* And we'll call the whole thing an array
Let's see an example. We'll:
* Create an array
* Read a number of float values into it
* Write out the values back-to-front
(Clearly this is one of those cases where we have to store what could be a lot of numbers.)
Let's look through the various parts of that.
* Definition and declaration
Just like other variables we have seen, you must define that the variable called "costs" is going to contain float information, and you must also declare it's going to be an array:
That has defined how the variable name will be used, but has not set aside any memory for it.
Since computers store things one-after-another in memory, we must actually create our array, declaring its size:
costs = new float;
In Java, the array is actually an object created by using the new method.
It is important that you understand the distinction between defining an array and actually allocating the memory for it, although in practice you could do both in one line:
float costs = new float ;
We have defined that a variable name is to be used as an array, and we have set aside the memory for it. How do we actually make use of it?
We refer to the array name, and then the element number in square brackets. Elements are counted from 0 up, so our five-element array is numbered zero to four.
As well as referring to elements by giving an integer constant, we can use an integer variable, or even an integer expression within the square brackets, so that we calculate the element number.
And we can use array elements anywhere where we could use just a simple variable of the same type. Thus, in our sample program, we had:
costs[count] = wellreader.read_number();
which set an element of the array to contain the number read from the user, and:
if (costs[count] <= 0.0) break;
which used an element of the array in a calculation (in this case to yield a boolean result), and:
PH: 01144 1225 708225 • FAX: 01144 1225 899360 • EMAIL: firstname.lastname@example.org • WEB: http://www.wellho.net • SKYPE: wellho | <urn:uuid:46a0bc8b-46aa-4dc8-8df5-8d11f2f61b43> | 3.1875 | 726 | Comment Section | Software Dev. | 61.375416 |
Corophium volutator (known locally as mud shrimp) are actually not shrimp but a member of a suborder of crustaceans known as amphipods. These fine fellows inhabit the upper layers of mud in the Bay of Fundy and play a vital role in this complex ecosystem.
Corophium keeps a very low profile: so low in fact that until a couple of decades ago Fundy 's mudflats (fully exposed at low tide) were considered lifeless wastelands of little ecological interest. But, as sandpipers have known for ages and scientists have recently learned, if you probe beneath the surface, the mud is home to unbelievably large numbers of these tiny amphipods.
For the etymologists in the familly: volutator comes from the Latin volutare, meaning "to wallow". Seems apt for these mud loving creatures! | <urn:uuid:3b29a7d0-1ef3-4698-9891-981374a0be82> | 3.171875 | 180 | Personal Blog | Science & Tech. | 32.563333 |
Acanthaster planci are red colored echinoderms protected by thorn-like spines. They grow to a diameter up to 40 cm across. They have 12-19 arms extending from their center. These animals do not have a head, and are pentamerically symmetrical about the axis of the mouth. Acanthaster planci have tubed feet, or branched tentacles arranged along each arm that function in gas exchange and food gathering (Schmid, 1998; Perrins and Middleton, 1985; Encyclopedia Britannica, 2000). | <urn:uuid:29dc0975-fb39-46aa-971f-5c3cebeb394e> | 3.0625 | 113 | Knowledge Article | Science & Tech. | 44.470158 |
The pavement material that cars drive on may wind up in their fuel tanks as scientists seek ways of transforming asphaltenes - the main component of asphalt - into an abundant new source of fuel, according to the cover story in the current issue of Chemical and Engineering News, ACS' weekly newsmagazine...
- Component of asphalt eyed as new fuel sourceWed, 23 Sep 2009, 13:19:06 EDT
- Developing 'green' tires that boost mileage and cut carbon dioxide emissionsWed, 18 Nov 2009, 16:30:28 EST
- Battling the force that wastes 1 out of every 10 gallons of gasoline in carsWed, 13 Oct 2010, 13:36:35 EDT
- Alternative energy hits the roadTue, 12 Aug 2008, 14:56:30 EDT
- Gator in your tank: Alligator fat as a new source of biodiesel fuelThu, 18 Aug 2011, 16:05:07 EDT | <urn:uuid:45bcbaf6-54af-4753-8919-7ef1cc149156> | 2.765625 | 191 | Content Listing | Science & Tech. | 45.624939 |
"Earth's north magnetic pole is drifting away from North America and toward Siberia at such a clip that Alaska might lose its spectacular Northern Lights in the next 50 years, scientists said Thursday.
Despite accelerated movement over the past century, the possibility that Earth's modestly fading magnetic field will collapse is remote. But the shift could mean Alaska may no longer see the sky lights known as auroras, which might then be more visible in more southerly areas of Siberia and Europe.
The magnetic poles are part of the magnetic field generated by liquid iron in Earth's core and are different from the geographic poles, the surface points marking the axis of the planet's rotation.
Scientists have long known that magnetic poles migrate and in rare cases, swap places. Exactly why this happens is a mystery." | <urn:uuid:ce523f79-8529-46ef-b3cd-13f41acb24f6> | 3.265625 | 159 | Personal Blog | Science & Tech. | 41.144524 |
can occur anywhere in the world where convective storms occur. Near mountainous
terrain, the additional uplift often increases hail occurrences. Some of the
highest frequencies of hail occur in western China and
northern India. Hail
also occurs frequently near the Alps in Europe, Andes in S.
America, and in mountainous east Africa. Australia also has
hail, particularly in New South Wales. For
information on Australian hail, see: http://www.boin.gov.au/weather/nsw/sevwx/hailfact.shtml
for the 1999 Sidney, Australia
hailstorm. The climatology of hailstorms
in Great Britain may be
seen at: http://www.torro.org .
In the United
States, hails most frequently occur in
Hail Alley: The Great
Plains states, especially northeastern Colorado and southeastern Wyoming, receive more hail yearly than any
other part of the United States. The states experiencing the most
frequent hail include: Colorado, Wyoming, Nebraska, Kansas, Texas, and Oklahoma. Hail in this area of the country is most likely to
fall late in the afternoon during the months of May and June and is often
responsible for extensive crop loss, property damage and livestock
deaths. While hail is most frequent in NE Colorado, severe hail (3/4” or greater, or
damaging) shows highest frequencies further east, in Oklahoma.
Geography of large hail
Large hail is known to
farmers and insurance companies as the most destructive. In the map below, hail
of 2” and greater is mapped.
(source: NSSL, NOAA)
To look for hail occurrences in any state of the United
States, please go to http://www.nssl.noaa.gov/hazard/hazardmap.html
A map of severe hail in Colorado
shows that not all of the state has high risk for damaging hail. However, of the 1200 reported events,
clusters appear in NE Colorado over the High Plains
parallel to the Rocky Mountains.
Distribution of severe hail in Colorado.
For more information on Colorado
hail, please go to
hailstorm of 1998 is discussed at:
Canadian hailstorms occur most frequently to the east of the
Rockies in Alberta,
with damaging hail also occurring along the southern portions of the Prairie
For information on hailstorm patterns in Alberta
using radar, see: | <urn:uuid:1ede578d-97b4-4a66-9199-30e9a4f6c720> | 3.9375 | 519 | Knowledge Article | Science & Tech. | 52.648503 |
I am usually questioned by friends regarding Java IO. Questions usually revolve between byte and char conversion and what determines the codepage used. My answer to them is always the same: if you are using Streams you are dealing with bytes and if you are dealing with Readers and Writers then you are dealing with Chars (usually you specified codepage to be used or it is using system default). I usually tell them to distrust any class named SomethingStream that have any method that operates over Strings (eg.: ServletOutputStream) cause they’ll usually do some implicit conversion (either using system codepage or something else out of your control).
I’ve prepared a diagram to clarify the main Java IO classes (and their main methods also):
On the bottom you’ll find Stream classes, they operate on bytes so codepage here is irrelevant. In the middle you’ll find conversion classes: those are the ones that allow you to forcefully define a codepage, they are the bridge classes that allow you to plug a Writer on an OutputStream or a Reader on an InputStream. You may use them to specify, for example, a codepage for writing on a TCP socket. And lastly, on top, you’ll find Character (and therefore String) oriented classes: Reader and Writer.
You may have noticed that I have included the Buffered version of the Stream classes. The Output one provides better performance under certain scenarios. The BufferedInputStream on the other hand allows you to mark and rewind its content, something usually useful for implementing protocol interpreters. | <urn:uuid:671cbf0e-378c-4b50-ab3a-f89a495b5e8f> | 2.921875 | 332 | Personal Blog | Software Dev. | 37.118718 |
Creating a list/tuple/dictionary
ajw126NO at SPAMyork.ac.uk
Tue Jan 7 15:26:59 CET 2003
When the Python interpreter comes across a statement such as...
a = [1,2,3]
how does it go about creating that list?
Does it convert the code into something equivalent to
a =
(although obviously it would call the C functions directly)
or is there a quicker method that it uses, if so is that accessible from
ordinary python code?
The same question applies to tuples and dictionaries, although I'm guess
that the same answer will apply to all of them.
thanks in advance,
More information about the Python-list | <urn:uuid:1d7a0832-6a97-4d4c-b5bb-7adc13f68a4d> | 3 | 155 | Q&A Forum | Software Dev. | 67.799167 |
volume with calculus
find the volume of the solid whose base is the area bounded by the lines y=1-(x/2), y=(x/2)-1 and x=0 and whose cross sections perpendicular to the x axis are equilateral triangles.
do i do v=the integral of (1/2)(2x*x) dx
that seems too simple...
also, find the volume of the solid generated by revolving the region bounded by the graph y=x^2, y=4x-x^2 and revolved about the line y=6
i got 64/3 pi, is this right?
what am i doing wrong in these two problems?(Headbang)(Bow)
How would you arrive at that integral?
What is length of the base of one of those equilateral triangles? What is the height of that triangle? What is the area?
i have no idea.its an equilateral triangle so would each side be x? | <urn:uuid:af03f186-fb4b-49f1-aade-3dde5de459e0> | 2.828125 | 203 | Q&A Forum | Science & Tech. | 84.7315 |
ABCD is a trapezium, AB and CD are parallel sides, M is the midpoint of AD. Prove that the area of the triangle BMC is half the area of the trapezium.
I let A be the origin, then the vectors of AB, AC, and AD respectively are b, c, d. So vector AM=
Area of the trapezium=
vector CM= vector CB=
My problem is I am stuck here, I think it is just some rearrangement of the vectors, but I am no good at dot and cross-products. | <urn:uuid:35e4dae0-51fe-4896-b7ca-0893bf7f8def> | 3.328125 | 121 | Q&A Forum | Science & Tech. | 73.948182 |
Recent "the sky is falling" news stories have dealt with the fall from orbit of the Mir Space Station rather than NEO impacts. The press and public are clearly interested in the risk of falling objects, but sometimes risks are perceived in ways that are quite different from the hazard as calculated numerically. The following is a very rough estimate of risks, in "order of magnitude" terms only. It is intended to be illustrative, but certainly not precise. By risk I mean the chance or probability that any individual will be killed as a result of either a spacecraft atmospheric entry or the impact of a NEO.
Let's start with the risk of death as a result of being struck by a piece of Mir on the assumption that the fragments could land anywhere on Earth. Suppose 1000 large metal fragments survive to hit the ground, and that if you are within 1 meter of the impact point you will be killed. Thus 1000 square meters are at risk, out of a total surface area of the Earth of about 100 trillion (10**14) square meters (not counting the Polar Regions). This is one part in 100 billion of the Earth's surface, and that is the risk to each individual. Multiplying by the Earth's population of 6 billion, we get a chance of about 1 in 20 that one person on Earth would be killed.
In fact, the Mir atmospheric entry was far from random. It was steered to an impact point in the mid-Pacific Ocean. Unless you lived in that part of the world, the risk to you was zero (not allowing for an uncertainty in how well this controlled entry would be executed). Since the total population of the Pacific is only a few million, the chance that someone would be killed was less than 1 in 20,000. The folks who sold the Russians a $200 million insurance policy were very unlikely to have to pay off any claims.
For comparison, consider the annual risk of dying as a result of an NEO collision with the Earth. A number of studies (e.g., the paper that Clark Chapman and I published in Nature in 1994) have shown that this risk is dominated by near Earth asteroids of about 2 km diameter. There is a roughly 1 in a million chance of such an impact each year, with estimated death of 1-2 billion people. Thus the annual risk to each of us of from NEO impacts is about 1 in a few million, or more than 10,000 times greater than the risk from an uncontrolled Mir entry. (Note: This is a conservative estimate; many would argue for a NEO-impact risk that is higher by an order of magnitude.)
We see from these simple calculations that the risk (per year) to each of us from asteroid impact is thousands of times greater than from an uncontrolled Mir entry, and millions of times greater than from a controlled Mir dive into the Pacific. Yet no one is taking out insurance policies to protect from cosmic impacts, and this risk receives less news coverage than the demise of Mir. Why the disparity? For one thing, the death of Mir was a known event that provided a good story, while we have no specific prediction of any NEO impact. For another, Mir was a human-built object over which we had some control (and responsibility), while an NEO impact is considered an "act of God". But I suspect that the difference also reflects the fact that very few reporters tried to make a quantitative comparison of these risks. If they had, the results might have surprised them! | <urn:uuid:4baec056-e10b-4223-a5ec-6c66a3cfc126> | 3.125 | 704 | Nonfiction Writing | Science & Tech. | 58.301013 |
Scan is a collective algorithm that performs partial reductions on data provided by each process in the communicator. Scan combines the arrays stored by each process into partial results delivered to each process. The arrays are combined in a user-defined way, specified via a delegate that will be applied elementwise to the values in each arrays. If array(0), array(1), ..., array(N-1) are the arrays provided by the N processes in the communicator, the resulting array for the process with rank P will be array(0) op array(1) op ... op array(P). The processor with rank N-1 will receive the same result as if one had performed a Reduce<(Of <(T>)>)(array<T>(), ReductionOperation<(Of <(T>)>), Int32, array<T>()%) operation with root N-1. Scan is sometimes called an "inclusive" scan, because the result returned to each process includes the contribution of that process. For an "exclusive" scan (that does not include the contribution of the calling process in its result), use ExclusiveScan<(Of <(T>)>)(array<T>(), ReductionOperation<(Of <(T>)>), array<T>()%).Namespace: MPI
Assembly: MPI (in MPI.dll)
Version: 188.8.131.52 (184.108.40.206)
public void Scan<T>( T inValues, ReductionOperation<T> op, ref T outValues )
|Visual Basic (Declaration)|
Public Sub Scan(Of T) ( _ inValues As T(), _ op As ReductionOperation(Of T), _ ByRef outValues As T() _ )
public: generic<typename T> void Scan( array<T>^ inValues, ReductionOperation<T>^ op, array<T>^% outValues )
- Type: array<
The array contributed by the calling process. The arrays provided by each process must have the same length.
- Type: MPI..::.ReductionOperation<(Of <(>)>)
Operation used to combine two values from different processes.
The array array(0) op array(1) op ... op array(Rank)
- Any serializable type. | <urn:uuid:ee43273a-eb5a-4035-ad9d-6fde737b0523> | 2.90625 | 483 | Documentation | Software Dev. | 60.350325 |
Atoms, Elements, Compounds
the time the Curies
discovered polonium and radium, identifying new chemical elements was
one of the highest goals a scientist could hope to reach. A chemical
element is a substance that
contains only one kind of atom.
If you keep dividing up such a substance, you finally get to the tiny
atoms. Nobody had been able to divide an atom further, into smaller pieces.
in the world around us is made up of the atoms of the chemical elements,
combined with one another in countless ways in compounds.
For example, water is not an element but a compound of two true elements,
hydrogen and oxygen. When chemists describe water as H2O
they mean that the smallest particle of water is made of two atoms of
hydrogen and one atom of oxygen. For scientists of Marie Curies
time, it was a great mystery why atoms of different elements had different
chemical propertiesfor example, why it was in the nature of oxygen
atoms to combine in this way with hydrogen to make a wet liquid. Experiments
using radioactivity helped bring the answer after many years. | <urn:uuid:9d209525-3e68-4140-8c20-ac42c189e5f4> | 3.609375 | 242 | Knowledge Article | Science & Tech. | 39.400269 |
Why No Explosion?Science brain teasers require understanding of the physical or biological world and the laws that govern it.
It is scientific fact that if all else is held constant, the pressure of a gas varies directly with its temperature. In other words, if you have a gas in a sealed, insulated, rigid container and you double its temperature, its pressure will also double. If you triple the temperature, the pressure will triple, etc. This is not EXACTLY true, but it is close enough for the purpose of this teaser.
Why is it, then, that if I were to fill my tires with 32 psi of air on a day that is 2 degrees Celsius, the tires won't explode if the temperature later increases to 20 degrees Celsius (which would seemingly increase the pressure 10-fold to 320 psi, well beyond the capacity of most tires)?
Assume that the temperature of the air in the tire always matches the temperature outdoors: it starts at 2 degrees and ends at 20 degrees.
Also ignore the fact that the tires will expand.
HintThis problem is really more mathematical than scientific. Here's a hint: say you have a temperature of -10 degrees Celsius. Now double that temperature. You get -20 degrees. Doesn't it seem a little odd that when you double something's temperature that it actually goes DOWN?? When you double something's LENGTH, it never goes DOWN. What's wrong here?
AnswerLike the hint implies, the key to this teaser is understanding what you are really doing when you multiply numbers. For example, if you have the number 3 on a number line and you want to double it, what you could do is put your thumb at 0 and your index finger at 3, and then measure off that distance past 3 one time, which will of course bring you to 6. You are essentially doubling the distance that 3 is from 0 to get 6. The only reason this works, however, is because at 0 you really have ZERO length. 0 really means "nothing" in this case. With the Celsius temperature scale, however, 0 degrees does not mean that you have "no temperature". 0 degrees was chosen arbitrarily to coincide with the freezing point of water. Other than that, it has no real significance. So if you want to multiply 2 degrees C by 10, you have to increase its distance from ABSOLUTE zero by 10, not its distance from the arbitrary 0.
Absolute zero is about -273 degrees C. At this point, there really is "no temperature". So when the temperature in the problem goes from 2 degrees to 20 degrees, it is really going a "distance" of 275 degrees from zero to a distance of 293 degrees from zero, which is only an increase of 6.5 percent, not enough to make your tires explode.
The moral of this story is that if you want to multiply numbers, the numbers themselves must represent their "distance" from a true zero. You can add and subtract numbers without knowing this "distance", but you can't multiply and divide.
See another brain teaser just like this one...
Or, just get a random brain teaser
If you become a registered user you can vote on this brain teaser, keep track of
which ones you have seen, and even make your own.
Back to Top | <urn:uuid:8bbb4369-b8bc-4dee-99ef-6c1a295599ca> | 3.671875 | 675 | Personal Blog | Science & Tech. | 64.620179 |
|Figure 2-3: Components of the terrestrial carbon pool (compiled
and amplified from Apps and Price, 1996).
To fully account for carbon at a site, one must examine the forest, the crops, and the soils as a dynamic multi-component ecosystem, above- and below-ground, with changes in biomass and soil organic matter as key tracking mechanisms.
The most easily measurable pool is the total standing aboveground biomass of woody vegetation elements. The aboveground biomass comprises all woody stems, branches, and leaves of living trees, creepers, climbers, and epiphytes, as well as herbaceous undergrowth. In some inventories, dead fallen trees and other coarse woody debris, as well as the litter layer, are included in biomass estimates; in other inventories, these categories are considered as a separate dead organic matter pool. In practice, standing timber volumes per hectare are often taken as a proxy value, applying a locally tested conversion factor (see Section 2.4).
The below-ground biomass comprises living and dead roots, soil mesofauna, and the microbial community. There also is a large pool of organic carbon in various forms of soil humus (soil organic carbon, SOC). Other forms of soil carbon are charcoal from fires and consolidated carbon in the form of iron-humus pans or concretions. Many soils also contain a subpool of inorganic carbon in the form of hard or soft calcium carbonate (soil inorganic carbon, SIC).
Another major pool of carbon consists of forest products (timber, pulp products, non-timber forest products such as fruits and latex) and agricultural crops (food, fiber, forage, biofuels) taken off the site. Section 2.4 discusses their measurement and the monitoring of their routing and stability.
The components of the terrestrial carbon pools are illustrated in Figure 2-3.
Other reports in this collection | <urn:uuid:f9633ce4-5efc-4337-8fbd-3d72989f2884> | 3.40625 | 396 | Knowledge Article | Science & Tech. | 36.887571 |
Summary: THE GEOMETRY OF K3 SURFACES
LECTURES DELIVERED AT THE
SCUOLA MATEMATICA INTERUNIVERSITARIA
JULY 31--AUGUST 27, 1988
DAVID R. MORRISON
This is a course about K3 surfaces and several related topics. I want
to begin by working through an example which will illustrate some of
the techniques and results we will encounter during the course. So
consider the following problem.
Problem . Find an example of C X P3
, where C is a smooth
curve of genus 3 and degree 8 and X is a smooth surface of degree 4.
Of course, smooth surfaces of degree 4 are one type of K3 surface.
(For those who don't know, a K3 surface is a (smooth) surface X which
is simply connected and has trivial canonical bundle. Such surfaces
satisfy (OX ) = , and for every divisor D on X, D · D is an even
We first try a very straightforward approach to this problem. Let C | <urn:uuid:b5b3c86a-08e0-40fa-bbc0-ba8b5f9bc304> | 2.734375 | 232 | Academic Writing | Science & Tech. | 61.468521 |
Web edition: December 13, 2012
Print edition: December 29, 2012; Vol.182 #13 (p. 34)
According to one popular notion, everyone has a twin somewhere. Who knows, maybe the same is true for planets. Maybe there’s even a doppelgänger Earth orbiting at just the right distance from a sunlike star to support life. In his latest book, science writer Lemonick provides a behind-the-scenes look at the decades-long search for just such a planet. The endeavor, long considered a scientific backwater with little chance of success, is now one of the hottest fields in astronomy.
Like any nascent field of science, the search for exoplanets poses a challenge that has lured both established researchers and ambitious students. These pioneers aim to detect planets too distant to see directly, by discerning the subtle wobbles of stars being tugged back and forth by the planets, as well as slight dimmings that result when planets pass in front of their parent stars.
In a fascinating chronicle of camaraderie and competition, Lemonick profiles the prominent researchers in an astronomical discipline that is coming of age. He follows the twists and turns in their careers as well as the towering hurdles they faced and ultimately solved — including oft-denied funding requests and the equally daunting search for respect among scientific peers.
At first, researchers could discern only exceptionally large planets closely orbiting small stars. But techniques used to detect exoplanets are becoming more and more sensitive, and scientists may be getting close to discovering a mirror Earth — a find that might be revealed within months, not years, Lemonick contends. — Sid Perkins
Walker & Co., 2012, 294 p., $26 | <urn:uuid:c9218405-a15e-4b02-9a5e-f124aabe9c3a> | 3.109375 | 353 | Truncated | Science & Tech. | 47.021576 |
Young Cells in Old Brains [Preview]
The paradigm-shifting conclusion that adult brains can grow new neurons owes a lot to Elizabeth Gould's rats and monkeys
ELIZABETH GOULD: CHANGING MINDS
Image: PETER MURPHY
- Past thinking: Memories are stored by locked-in neural connections. Present: The brain can add neurons, perhaps to establish new memories.
- Hope for dementia: New neurons seem able to migrate, suggesting that therapeutic cells can be guided to areas damaged by disease or injury.
it or lose it: In lab animals not kept in a stimulating cognitive environment, "most new neurons will die within a few weeks."
PRINCETON, N.J.--Reunion weekend at Princeton University, and the shady Gothic campus has been inundated by spring showers and men in
boaters and natty orange seersucker jackets. Tents and small groups of murmuring alumni dot the courtyards. Everything proper, seemingly in its place. In
This article was originally published with the title Young Cells in Old Brains. | <urn:uuid:432f2674-a5de-42b2-9ab7-169c23f586c7> | 2.953125 | 224 | Truncated | Science & Tech. | 45.971972 |
Corals Corals All corals belong to the Phylum Cnidaria (Ni-da´-ri-a). The cnidarians are a natural group of invertebrate animals that have a simpler organization than most other inverte
The corals discussed in this article are capable of growing very fast. Fragging is in your future whether you realize it or not. Some of the slimy beginner corals like mushrooms, ...
Branching corals, especially shallow-water Acroporawhichare primary habitat builders, will become brittle and more easily damaged leading to extensive habitat deterioration.
Although sedimentation and destructive fishing methods may pose more risk to Indonesian coral reef ecosystems as a whole, the commercial extraction of corals cannot be overlooked.
*oceanservice.noaa.gov/education Subject Review Corals 8.
NOAA National Ocean Service Education: Corals NOS home NOS education home site index This site NOAA Corals Roadmap Corals Lesson Plans Welcome What are Corals?
© 2004, PETCO Animal Supplies, Inc. All rights reserved . (0315) 1 of 2 Soft corals are leathery or fleshy colonies with a soft skeleton. They are hardier than hard corals and grow rapidly.
Most corals consist of many small polyps living together in a large group or a colony. A single polyp has a tube-shaped body with a mouth which is surrounded by tentacles.
© 2004, PETCO Animal Supplies, Inc. All rights reserved . (0315) 1 of 2 "Stony" or "hard" corals have a hard calcium carbonate skeleton. They are a popular saltwater invertabrate for aquariums because of their beautiful colors or flower-like appearance.
This report was written by Patty Debenham, Ph.D. Contributing authors and editorial assistance from: Andrew Baker, Ph.D., Elisabeth Banks, Shannon Crownover, Lauren Cuneo, Hollis A. Hope, Corinne Knutson, Cindy Krupp, Dawn M. Martin, Bruce McKay, Elizabeth Neeley, Eric Punkay, Julia Roberson ... | <urn:uuid:afe86adf-7a3a-4729-8461-cced1e447b66> | 3.234375 | 449 | Truncated | Science & Tech. | 38.486573 |
The burning of fossil fuels like coal, gas and oil releases particles into the atmosphere. When fossil fuels are not burned completely, they produce black carbon -- otherwise known as soot. Soot looks like a black or brown powder and though it's made up of tiny particles, it can have a big impact on climate.
Black carbon stays in the atmosphere for several days to weeks and then settles out onto the ground. It can be produced from natural causes like when lightning causes a forest fire. Most black carbon results from human practices like slash and burn methods for clearing land, using diesel engines, and industrial processes that burn coal, gas and oil, and coal burning in homes. Black carbon is produced around the world and the type of soot produced varies by region.
Black carbon adds to global warming in two ways. First, when soot enters the atmosphere, it absorbs sunlight and generates heat, warming the air. Second, when soot settles on snow and ice, it makes the surface darker, so the surface absorbs more sunlight and generates heat. This warming causes more snow and ice to melt, in what can be a vicious cycle.
Black carbon lowers the albedo of a surface. Scientists use the term "albedo" as an indicator of the amount of energy reflected by a surface. Albedo is measured on a scale from zero to one (or sometimes as a percent).
- Very dark colors have an albedo close to zero (or close to 0%).
- Very light colors have an albedo close to one (or close to 100%).
Soot is dark in color, and so has a low albedo and reflects only a small fraction of the Sun's energy. Forests have low albedo, near 0.15. Snow and ice, on the other hand, are very light in color. They have very high albedo, as high as 0.8 or 0.9, so they reflect most of the solar energy that gets to them, absorbing very little. The more dark surfaces on Earth, the less solar energy is reflected and this means more warming as more solar radiation is absorbed. Soot makes surfaces (or the atmosphere) darker and so adds to global warming.
Scientists say that black carbon emissions are the second largest factor in global warming, after carbon dioxide. Reducing black carbon is one of the fastest ways for slowing global warming. Luckily, many policies have been put in place to lessen black carbon around the world, and the technology needed to lessen black carbon already exists. The importance of black carbon's role in global warming has come to the forefront of the minds of many concerned citizens and exciting steps are already being taken to address issues like making cleaner burning cookstoves available in developing nations and improving industrial practices that produce black carbon. Reducing black carbon around the world will not only lessen global warming, but will cut down on air pollution and will improve human health. | <urn:uuid:4bec3b16-8808-45c8-a741-13815cc65911> | 4.34375 | 597 | Knowledge Article | Science & Tech. | 54.113747 |
setfsuid - set user identity used for file system checks
#include /* glibc uses
int setfsuid(uid_t fsuid);
setfsuid sets the user ID that the Linux kernel uses
to check for all accesses to the file system. Normally, the
value of fsuid will shadow the value of the effective
user ID. In fact, whenever the effective user ID is changed,
fsuid will also be changed to new value of effective
An explict call to setfsuid is usually only used by
programs such as the Linux NFS server that need to change
what user ID is used for file access without a corresponding
change in the real and effective user IDs. A change in the
normal user IDs for a program such as the NFS server is a
security hole that can expose it to unwanted signals from
other user IDs.
setfsuid will only succeed if the caller is the
superuser or if fsuid matches either the real user
ID, effective user ID, saved set-user-ID, or the current
value of fsuid.
On success, the previous value of fsuid is returned.
On error, the current value of fsuid is
setfsuid is Linux specific and should not be used in
programs intended to be portable.
No error messages of any kind are returned to the caller. At
the very least, EPERM should be returned when the
When glibc determines that the argument is not a valid uid,
it will return -1 and set errno to EINVAL without
attempting the system call. | <urn:uuid:5265ab6b-9d40-44b4-9169-5ca2d64eac58> | 3.03125 | 355 | Documentation | Software Dev. | 46.508047 |
Science Fair Project Encyclopedia
Mist is a phenomenon of a liquid in small droplets floating through air. It can occur naturally as part of natural weather or volcanic activity, and is common in cold air above hot water, in exhaled air in the cold, and in a steam room of a sauna. It can also be created artificially with aerosol canisters. Fog is a definition closely related to mist, in that their definitions overlap. At performances and parties a fog machine can be used for visual effects, possibly combined with special lighting.
Not to be confused with the Myst computer game series.
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:37be06d5-2ae6-4b0e-8da4-7e7644cd38a5> | 3.125 | 151 | Knowledge Article | Science & Tech. | 45.384341 |