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It’s fun to dress up and pretend you’re someone else, at least for a little while. But in the bug world looking different isn’t just for fun, it’s a way of life. Being in disguise helps insects hunt for food and stay safe. Some grasshoppers, spiders and caterpillars have a unique way of keeping “undercover.”
It’s a Stick…It’s a Leaf…It’s a Grasshopper?
The grasshoppers we’ve all seen aren’t too shy about hip-hopping and bopping around the long grass. But some of their far-away relatives need to be safer. The Monkey-Hoppers of the tropical rain forest use the shape and color of leaves in order to hunt and hide. Other grasshoppers known as Stick Grasshoppers have long, thin, bumpy brown bodies that look exactly like twigs. The Pygmy Grasshopper is also good at looking like a mossy log or the stony ground it lives on. In fact, they are so good at blending in you’ll probably never see one; at least not that you know of.
Crab Spider Surprise
It’s no secret that spiders catch bugs in their webs, but when it comes to the Crab Spider, he’s got a few extra-sneaky secret weapons. To catch bees, flies, or moths, the crab spider’s front legs are very strong with a claw on the end, something like a crab. So when a bug comes near all it has to do is reach out and snap it up. If that isn’t enough, this funny fellow matches his colors to any flower he’s waiting on. However, patterns, dots and colors aren’t the only thing this rain forest spider can do. One spider actually looks like a big blob of bird droppings. Yuck! How’s that for a disguise?
Creepy Caterpillar Camouflage
Caterpillars need to keep safe from their many predators, so they have adapted different ways to keep hidden.
The Elephant-hawk moth caterpillar is large (3 in) and gets it’s name, not from its size, but rather from the way it will curve its body into a trunk-like posture when it feels threatened. This caterpillar also has unique markings all along its body that resembles a snake. It has a large head and four big eye-like patches that will scare off most hunting birds - at least for a little while.
The Wavy-lined Emerald moth caterpillar is one of the more fascinating and unusual of its species. This guy will actually take out pieces of the plant or flower that it’s munching on and stick them into it’s own back. This technique is very effective in keeping this creepy caterpillar camouflaged from most everything.
The next time you’re out for a nature walk look very carefully. That twig or pretty flower you spot may just be an undercover insect.
For more information on these and other bugs, check out your local library, a bug museum or the Internet. | <urn:uuid:1b9e1060-6419-46a2-9153-3cec99a029f5> | 2.75 | 669 | Personal Blog | Science & Tech. | 67.123439 |
Fact sheet number: FS-2002-2002-84-MSFC
Missions: Expedition 6, ISS Mission 11A, STS-113 Space Shuttle Flight, return flight ULF1, STS-114
Experiment Location on ISS: U.S. Lab EXPRESS Rack No. 4
Principal Investigator: Dr. Daniel C. Carter, New Century Pharmaceuticals, Inc. Huntsville, Ala.
Project Manager: Clark Darty, NASA's Marshall Space Flight Center in Huntsville, Ala.
Structural biology experiments conducted in the Diffusion-controlled Crystallization Apparatus for Microgravity (DCAM) may improve our understanding of the function of important macromolecules and possibly contribute to the development of new therapeutics.
Scientists select macromolecules, crystallize them, and use the crystals to determine the atomic arrangements of atoms within the molecules using intense beams of x-rays or neutrons - a process and field of research known as 'crystallography.' Knowledge gained through crystallography has played a key role in understanding many important chemical and biological processes. The determination of the three-dimensional structures of important proteins and other macromolecules, such as DNA, has contributed significantly over the past 50 years to the scientific understanding of fundamental processes in disciplines ranging from material science to biochemistry and medicine.
Microgravity - the near-weightless condition created as a spacecraft free-falls in orbit around the Earth - has been shown in many cases to produce crystals of improved perfection. This improvement can allow scientists to determine with greater precision the three-dimensional structure of the molecules making up the crystal.
The International Space Station provides for longer-duration experiments in an acceleration-free (no change in the rate of speed, or velocity, of the spacecraft that could affect the experiments), dedicated laboratory, than that provided by the Space Shuttle. Macromolecular crystals require from several days to several months to grow to optimum size. Mission 9A provides for longer-duration experiments in a more research friendly environment. One of the principal objectives of DCAM on the STS-113 mission is to produce extremely large highly ordered crystal specimens specifically for neutron diffraction applications (a more highly specialized subdiscipline of 'crystallography') - a long duration experiment series well suited for the International Space Station.
The Single-locker Thermal Enclosure System (STES) for the structural biology experiment is an incubator/refrigerator module that can house different devices for growing biological crystals in microgravity.
On the Shuttle STS-113 mission to the International Space Station, scheduled for launch in November 2002, the STES unit will house the Diffusion-Controlled Crystallization Apparatus for Microgravity (DCAM). Once on board the International Space Station, the unit will be located in the U.S. Lab EXPRESS Rack No. 4. After an extended growth period of four months, the experiments are scheduled to return to Earth aboard the Shuttle STS-114 mission in March 2003.
The DCAM is designed to grow crystals using the liquid-liquid diffusion method. A total of 81 individual experiments are housed inside the STES in three separate tray assemblies. In each tray, there are 27 reservoirs, each containing a different protein sample. Each device is slightly smaller than a 35mm film canister. The inside of the container is molded into two cylindrical chambers joined by a tunnel. The smaller chamber contains a buffer/precipitant solution. The end cap for this chamber holds the biological sample solution, covered by a semi-permeable membrane. This membrane allows the precipitant solution in the larger chamber to pass into the biological sample solution. A plug filled with porous material separates the two chambers and controls the rate of diffusion. Exposure to the precipitant causes the biological sample to crystallize. Diffusion -- the mixing of the biological sample solution with the precipitant solution -- starts on Earth as soon as the chambers are filled. However, the rate is so slow that no appreciable change occurs before the samples reach orbit one, two -- or even several weeks later.
Protein samples that will be processed during Expedition Six include:
The DCAM has no mechanical system. No crew interaction is necessary except for transferring the PCG-STES unit to the Space Station and back to the Shuttle at the end of the mission.
With science being performed on the International Space Station, scientists are no longer restricted to relatively short-duration flights to conduct structural biology experiments, opening the application of microgravity to a greater selection of important macromolecules. This research will enhance the accuracy of the 3-dimensional structures of specially selected macromolecules, providing improved crystallographic information, which has the potential to impact, a broad base of scientific research on Earth.
Additional information on structural biology crystal growth in microgravity is available at: | <urn:uuid:2810380e-e02d-4a64-9bb4-66a938c99ac8> | 2.71875 | 992 | Knowledge Article | Science & Tech. | 24.354579 |
|Version 19 (modified by zerny, 5 years ago)|
Welcome to the OpenEngine project
OpenEngine is a cross platform framework for creating 3D applications. It is a free software initiative started, at the Department of Computer Science at the University of Aarhus, in order to create a game engine geared towards educational usage. The engine provides a clean base and flexible architecture allowing many possible applications.
- Getting Started - Start here if you are new.
- Download - Obtaining the source code.
- Building - Building and running.
- Developers - Guides and resources for developers. | <urn:uuid:4444fd6d-f7c0-4ecd-ad8b-4be72365dc27> | 2.6875 | 123 | Content Listing | Software Dev. | 22.952273 |
Laser technology has recently evolved to the point where tunable uv radiation can be obtained using commercially available lasers. The uv output between 217–260 nm is generated indirectly by using nonlinear optical devices such as frequency doubling and mixing crystals and/or by utilizing anti-Stokes Raman shifting techniques. For any scientist using lasers, even experts, the choices in commercial laser systems can be confusing. Because these laser systems are extremely expensive, an error in choice can result in a major scientific disaster.
Sanford A. Asher, "Some Important Considerations in the Selection of a Tunable UV Laser Excitation Source," Appl. Spectrosc. 38, 276-278 (1984) | <urn:uuid:5fa3dbb7-2cdc-42c0-ac55-c71631463053> | 2.765625 | 140 | Academic Writing | Science & Tech. | 29.448019 |
Nuclear Power Can and should be the Solution for both Global Warming and Nuclear Waste
OK, I’ll say it even though it may be wildly unpopular in the wake of the nuclear disaster in Fukushima, Japan. We still need a nuclear renaissance in the U.S.A. I’ve been studying nuclear energy and there just might be a design that is safe, burns nuclear waste, emits no CO2 and might just help save the world.
Environmentalists are right that nuclear power, as we have it today and have seen it in Fukushima, is not entirely safe. The light water reactors we have today are not passively safe, use only about 1% of the natural uranium in their fuel, are badly sited and are getting old. Despite that, by the numbers nuclear is not nearly as dangerous as coal, gas, wind or even solar. The reality is that we have had Three Mile Island, Chernobyl and Fukushima, yet commercial nuclear power has not killed a single person in the U.S.A. in 61 years and only 56 at Chernobyl which was an epic failure of communist management, incompetence and disregard for their workers. Maybe we have just been lucky, but as of today, at least forty-one workers have died in the production of modern wind turbines, hundreds, thousands in China every year, have died mining coal ( 25 at the Upper Big Branch mine in W.Va last April) not to mention thousands or tens of thousands affected by emissions by coal plants. Hundreds have died in petroleum plant disasters and extraction accidents. Natural gas is certainly safer and cleaner, but still emits tons of CO2. Don’t get me wrong because I’m still a strong advocate for solar, wind and biofuels (there is nothing so efficient as a liquid fuel for transportation). Natural gas is leaps and bounds better than coal in so many ways so I am strongly in favor of replacing as many of our aging coal plants as can be replaced quickly with natural gas plants. Even with all these options, none of them really solves all the problems we need to solve for global society for power generation in the first half of this century.
For modern society there are three major problems that we have to solve or at least get on the road to solving in the next ten to twenty years. Those problems are as follows:
- We have to find some way to lower and then eliminate the majority of CO2 emissions as early in this century as possible.
- We have a serious problem with nuclear waste and weapons grade nuclear materials that we have to deal with by using them for fuel or storing them safely.
- We need a base power source for the grid that can produce reliable power on a 24x7x365 basis which solar and wind cannot satisfy.
Nuclear power plants also have some problems that we have seen close up at Fukushima and some that are not so obvious:
- Most of our plants are old and based on old designs that are very inefficient and not nearly as safe as the new designs. The last plant was begun in 1977 as a Gen II design and now we have Gen IV designs almost ready to go.
- Nuclear power plants are take a very long time to build and are incredibly expensive as well because they are each one off designs built in place.
- Supplies of known uranium will run out using current designs in 50 to 150 years depending on how many new plants are built.
- Both light and heavy water reactors of current designs in use less than 1% of the natural uranium that begins th fuel cycle and they produce masses of dangerous waste products that cannot reused.
What if there were a safe new nuclear reactor design that produced consistent reliable energy with almost no CO2 emissions and could be mass produced and put into service much more quickly and inexpensively than our existing designs? What if those new nuclear plants were designed for passive safety and could use up most of the nuclear waste and weapons grade fissile materials that we need to get rid of at a 95% efficiency? What if the new nuclear plant designs could do all that and revive U.S. manufacturing prowess and rejuvenate America as a leader in safe green energy in the world? What if we had tested this new technology safely for 30 years and one of our industrial titans has a design ready to build now as a prototype and could begin manufacturing commercial reactors as early as 2015.
You say that sounds like too good to be true? Well, GE has their S-PRISM advanced reactor design almost ready to go. What it mostly needs now is public, political and financial support to get going again. The design, known as an Integral Fast Reactor (IFR), Sodium-cooled Fast Reactor (SFR) or Advanced Liquid Metal Reactor (ALMR), is not new, so it is tested. It was originally developed at the Argonne National Laboratory in Idaho achieving first criticality in 1965 and it operated until 1994. GE Hitachi has a variant for commercialization called the Power Reactor Innovative Small Module (S-PRISM), which is the reactor portion and a key component to closing the nuclear fuel cycle by reusing spent nuclear fuel (and weapons grade fuel) instead of storing it. The DOE in 2001 created a 200+ PERSON task force of scientists from DOE, UC Berkeley, MIT, Stanford, ANL, LLNL, Toshiba, Westinghouse, Duke, EPRI, and others to evaluate the best new reactor designs on 27 different criteria. The IFR ranked #1 in their study released April 9, 2002. Though there are a few IFRs operating as test beds at present there are no Integral Fast Reactors in commercial operation.
- Meet the Man Who Could End Global Warming – Eric Loewen
- The Integral Fast Reactor (IFR) Project
- GE Hitachi’s PRISM Reactor
- Dan Rather’s take on Nuclear Reactors
- TEDxYYC – Kirk Sorenson on Thorium LFTR reactors
- Energy From Thorium.com
While I believe that in the near term the IFR derivatives like GE’s S-PRISM are the answer to both managing our nuclear waste stream and producing CO2 free electric power for management of global warming, the Thorium LFTR reactor concept is probably the answer to base electric production in combination with wind, solar, wave and bio fuels. In fact the LFTR can help in production of eco-friendly synthetic fuels via heat from water and CO2. | <urn:uuid:475c2961-a22b-403e-adbc-0275eadebdcf> | 2.84375 | 1,333 | Personal Blog | Science & Tech. | 50.670508 |
- How many planets do you think there are beyond the solar system we live in?
- How do you think scientists are able to detect these planets beyond our solar system?
- What is an exoplanet?
- When was the first exoplanet discovered, and how far away is it?
- How many exoplanets have scientists confirmed?
- How many possible exoplanets need to be studied further before they can be confirmed? What instrument has discovered these faraway blips?
- How many exoplanets reside in the galaxy we call home, the Milky Way?
- Describe the extreme conditions found on two exoplanets.
- Have planet hunters found an Earth-like planet? What three characteristics would make a planet Earth-like?
- How do astronomers estimate the temperature of faraway planets?
- Explain the Goldilocks zone.
- Are most confirmed exoplanets like the planets in the solar system we live in?
- Are most of the exoplanet solar systems similar to the solar system we live in? Describe two faraway solar systems and how they differ from ours.
- Explain how watching a star’s wobbles can help astronomers detect exoplanets.
- Does the Kepler telescope watch a large or small patch of sky? Roughly how many stars are in that patch of sky?
- Were you surprised to learn that astronomers haven’t found another Earth-like planet or another solar system like ours?
- Do you think other forms of life exist in the universe? Explain your answer.
- How will scientists be able to identify other life forms if they don’t resemble life as we know it on Earth?
1. How important do you think it is for scientists to continue to look for exoplanets? | <urn:uuid:12ba2379-2d63-4e67-b569-5d0712daa4ef> | 3.6875 | 372 | Q&A Forum | Science & Tech. | 52.993 |
Acronym for the Common Gateway Interface
A standard that defines the conditions a CGI program should be able to expect.
A CGI program is run by a WebServer to process certain requests. It is expected to return output to be sent back as the server's response to that request. That output will often be a WebPage, but might also be anything else the server can send, like an image or a binary file.
The standard specifies EnvironmentVariables that provide information about the request, like PATH_INFO, QUERY_STRING, REMOTE_USER, and more, as well as details such as where STDIN/OUT/ERR should be connected.
lib/main.php:944: Notice: PageInfo: Cannot find action page | <urn:uuid:62d98fe2-ba30-4f38-a785-7a0b0247eb26> | 2.953125 | 156 | Documentation | Software Dev. | 43.974034 |
45In meteorology, three different temperature scales are used: Fahrenheit, Celsius, and Kelvin.
German-born scientist Gabriel Daniel Fahrenheit developed the Fahrenheit Scale. He introduced his scale and new mercury thermometer in 1714 in Holland. Zero Fahrenheit was the coldest temperature Fahrenheit could create with a mixture of ice and salt. On the Fahrenheit Scale, water freezes at 32 and boils at 212.
Swedish astronomer Anders Celsius introduced his scale in 1742. He used 0 as the freezing point of water, and 100 as the boiling point.
For many years, the Celsius scale was also called the Centigrade because the Greek prefix "centi-" means one-hundredth, and each degree Celsius is one-hundredth of the way between the freezing and boiling points of water.
The third scale we use is the Kelvin Scale. British scientist William Thomson, Lord Kelvin did research on heat in the 1800s. Theoretically, the coldest temperature possible is -273.15 Celsius. This temperature is called absolute zero because at this temperature scientists believe that molecular motion stops. The Kelvin Scale uses this number as zero.
From Fahrenheit to Celsius
C = 5/9 x (F - 32)
From Celsius to Fahrenheit
F = (9/5 x C) + 32
From Celsius to Kelvin
K = C + 273.15 | <urn:uuid:c440db07-89fa-42b2-ac5d-aa3cc8459b08> | 4.25 | 278 | Knowledge Article | Science & Tech. | 56.550036 |
One of these things is not like the other: Astronomers have spotted a dwarf galaxy that spans just 3,000 light years across (as opposed to our Milky Way’s diameter of 100,000 light years), but hosts an outsize supermassive black hole for its puny size.
Some smaller galaxies have supermassive black holes as well, but in general these dwarf galaxies have some structure to them, with a well-defined core. Henize 2-10, as you can see, it a mess! It doesn’t have much overall structure, which is why it’s classified as an irregular galaxy. The thinking for big galaxies is that the black hole forms at the same time as the galaxy itself, and to regulate the growth of each other. When you look at lots of big galaxies, there’s a pretty clear overall correlation between the mass of the black hole and the galaxy around it.
So it’s pretty weird that Henize 2-10 has a supermassive black hole at all, but it turns out the hole is also about a million times the mass of the Sun — that’s pretty freakin’ big for such a tiny galaxy! That’s 1/4 the mass of our own black hole, in a galaxy that itself is far smaller than ours.
For more details about this weird galaxy, check out the rest of this post at Bad Astronomy. And for more galaxy-black hole weirdness, read last week’s 80beats post about whether mergers of galaxies truly cause supermassive black holes to become hyperactive.
80beats: Study: Hyperactive Black Holes Aren’t Caused by Galactic Smash-ups
80beats: LHC’s Lack of Black Holes Rules Out Some Versions of String Theory
80beats: Far-Off Quasar Could Be the Spark That Ignites a Galaxy
80beats: Researchers Spot an Ancient Starburst from the Universe’s Dark Ages
Image: Reines, et al., NRAO/AUI/NSF, NASA | <urn:uuid:779994d6-5c8f-49e4-bf81-ff2a4ad79837> | 3.484375 | 432 | Personal Blog | Science & Tech. | 52.454537 |
David Honig is a graduate student in marine science at Duke University in the lab of Dr. Cindy Van Dover. He is participating in LARISSA, a 2 month multinational expedition to study the causes and consequences of the ice shelf collapse. He will be posting regular updates on the expedition exclusively for Deep Sea News readers!
22 January 2010
Next stop in our fjord-hopping: Barilari Bay.
Andvord Bay and Barilari Bay are complete opposites. Andvord Bay was productive and teemed with life. Surface waters were thick with krill and phytoplankton. Whales surrounded the Palmer at all times, breaching and bubble-net feeding. The seafloor was strewn with kelp fragments and swarms of brittle stars. Rocks were covered with giant sponges and soft corals. Barilari Bay is comparatively quiet and barren. Surface waters are crystal clear. Seafloor life is much sparser and more fragile, consisting mostly of holothurians and small, sessile salps.
Glaciers likely play a role in this sharp contrast between the fjords. While Andvord Bay had only one large tributary glacier at the head of the fjord, Barilari Bay has six. Marine phytoplankton is averse to glacial runoff and as a result Barilari may have lower levels of primary productivity than fjords with fewer glaciers such as Andvord. Benthic communities in Barilari Bay are also likely to be strongly influenced by the glaciers, which spew carbon-lean rock flour onto the seafloor.
Andvord and Barilari are excellent sites to study the interaction between glaciers and the marine ecosystem. As our glaciologists fly to out to field sites, we will spend the next few days using CTD casts, water column samples, ROV transects, yo-yo cam images, and mega core samples to map patterns of primary productivity and benthic diversity in Barilari Bay. | <urn:uuid:6b65adc3-cbca-43c2-b1dd-a1246148e19f> | 2.78125 | 423 | Personal Blog | Science & Tech. | 42.569602 |
Topological quantum computer
A topological quantum computer is a theoretical quantum computer that employs two-dimensional quasiparticles called anyons, whose world lines cross over one another to form braids in a three-dimensional spacetime (i.e., one temporal plus two spatial dimensions). These braids form the logic gates that make up the computer. The advantage of a quantum computer based on quantum braids over using trapped quantum particles is that the former is much more stable. The smallest perturbations can cause a quantum particle to decohere and introduce errors in the computation, but such small perturbations do not change the topological properties of the braids. This is like the effort required to cut a string and reattach the ends to form a different braid, as opposed to a ball (representing an ordinary quantum particle in four-dimensional spacetime) simply bumping into a wall. The original proposal for topological quantum computation is due to Alexei Kitaev in 1997. While the elements of a topological quantum computer originate in a purely mathematical realm, experiments in Fractional quantum Hall systems indicate these elements may be created in the real world using semiconductors made of gallium arsenide near absolute zero and subjected to strong magnetic fields.
Anyons are quasiparticles in a two-dimensional space. Anyons are not strictly fermions or bosons, but do share the characteristic of fermions in that they cannot occupy the same state. Thus, the world lines of two anyons cannot cross or merge. This allows braids to be made that make up a particular circuit. In the real world, anyons form from the excitations in an electron gas in a very strong magnetic field, and carry fractional units of magnetic flux in a particle-like manner. This phenomenon is called the fractional quantum Hall effect. The electron "gas" is sandwiched between two flat plates of aluminum gallium arsenide, which create the two-dimensional space required for anyons, and is cooled and subjected to intense transverse magnetic fields.
When anyons are braided, the transformation of the quantum state of the system depends only on the topological class of the anyons' trajectories (which are classified according to the braid group). Therefore, the quantum information which is stored in the state of the system is impervious to small errors in the trajectories. In 2005, Sankar Das Sarma, Michael Freedman, and Chetan Nayak proposed a quantum Hall device which would realize a topological qubit. In a key development for topological quantum computers, in 2005 Vladimir J. Goldman, Fernando E. Camino, and Wei Zhou were said to have created the first experimental evidence for using fractional quantum Hall effect to create actual anyons, although others have suggested their results could be the product of phenomena not involving anyons. It should also be noted that nonabelian anyons, a species required for topological quantum computers, have yet to be experimentally confirmed.
Topological vs. standard quantum computer
Topological quantum computers are equivalent in computational power to other standard models of quantum computation, in particular to the quantum circuit model and to the quantum Turing machine model. That is, any of these models can efficiently simulate any of the others. Nonetheless, certain algorithms may be a more natural fit to the topological quantum computer model. For example, algorithms for evaluating the Jones polynomial were first developed in the topological model, and only later converted and extended in the standard quantum circuit model.
To live up to its name, a topological quantum computer must provide the unique computation properties promised by a conventional quantum computer design, which uses trapped quantum particles. Fortunately in 2002, Michael H. Freedman along with Zhenghan Wang, both with Microsoft, and Michael Larsen of Indiana University proved that a topological quantum computer can, in principle, perform any computation that a conventional quantum computer can do.
They found that conventional quantum computer device, given a flawless (error-free) operation of its logic circuits, will give a solution with an absolute level of accuracy, whereas a topological quantum computing device with flawless operation will give the solution with only a finite level of accuracy. However, any level of precision for the answer can be obtained by adding more braid twists (logic circuits) to the topological quantum computer, in a simple linear relationship. In other words, a reasonable increase in elements (braid twists) can achieve a high degree of accuracy in the answer. Actual computation [gates] are done by edge states of fractional quantum Hall effect. This make models one dimensional anyons important. In one space dimension anyons are defined algebraically.
Error correction and control
Even though quantum braids are inherently more stable than trapped quantum particles, there is still a need to control for error inducing thermal fluctuations, which produce random stray pairs of anyons which interfere with adjoining braids. Controlling these errors is simply a matter of separating the anyons to a distance where the rate of interfering strays drops to near zero. Simulating the dynamics of a topological quantum computer may be a promising method of implementing fault-tolerant quantum computation even with a standard quantum information processing scheme. Raussendorf, Harrington, and Goyal have studied one model, with promising simulation results.
See also
- "Computing with Quantum Knots" Graham P. Collins, Scientific American, April 2006.
- "Topologically Protected Qubits from a Possible Non-Abelian Fractional Quantum Hall State", Sankar Das Sarma, Michael Freedman, and Chetan Nayak , Phys. Rev. Lett. 94, 166802 (2005).
- "Non-Abelian Anyons and Topological Quantum Computation", Chetan Nayak , Steven H. Simon, Ady Stern, Michael Freedman, Sankar Das Sarma, Rev. Mod. Phys. 80, 1083 (2008); http://www.arxiv.org/abs/0707.1889, 2007
- "Topological fault-tolerance in cluster state quantum computation", Robert Raussendorf, Jim Harrington, Kovid Goyal, http://arxiv.org/abs/quant-ph/0703143, 2007
- "Quantum Computing with a Twist", Steven H. Simon, http://physicsworld.com/cws/article/indepth/43623. | <urn:uuid:ddc7fca8-309f-4082-9e13-4c0ad0010cf6> | 3.671875 | 1,330 | Knowledge Article | Science & Tech. | 29.540934 |
A ball whooshes down a slide and hits another ball which flies off
the slide horizontally as a projectile. How far does it go?
How high will a ball taking a million seconds to fall travel?
A weekly challenge: these are shorter problems aimed at Post-16 students or enthusiastic younger students.
Suppose we have a pool table without pockets and with side lengths $a$ and $2b$. The ball is placed at point A.
1) Find four different angles for the ball to get back to the same point A.
2) Find four possible angles for the ball to go to the point D.
3) This is a bit more challenging question. Find four different angles in each situation 1) and 2) if we have the same pool table but with pocket. The ball starts to move from the point A which is just in front of the pocket.
State any assumptions that you make. | <urn:uuid:ae2c602e-9a25-4feb-a0df-e6106d4b3f76> | 2.890625 | 189 | Tutorial | Science & Tech. | 78.013616 |
But who killed the Medieval Warm Period?
Before we begin the investigation into the usual suspects, some background for people who those who don’t follow climate science closely, which certainly includes most of the disinformers and apparently at least two statisticians.
- There is a high probability that the recent warming is unprecedented for 1000 years and probably much longer (see “Sorry disinformers, hockey stick gets longer, stronger: Earth hotter now than in past 2,000 years” and here and here).
- This conclusion is based on an analysis of multiple proxies for temperature, which individually engender much uncertainty and collectively still engender a fair amount. It is a canard of Curry-esque proportions to assert that scientists have not clearly explained the nature and extent of these uncertainties. They have bent over backwards to do so.
- The temperature trend in the past millennium prior to about 1850 is well explained in the scientific literature as primarily due to changes in the solar forcing along with the effect of volcanoes, whereas the recent rise in temperature has been driven primarily — if not almost entirely — by human activity (see Scientist: “Our conclusions were misinterpreted” by Inhofe, CO2 — but not the sun — “is significantly correlated” with temperature since 1850 and Part 3 [to come]).
- Absent human emissions, we’d probably be in a slow long-term cooling trend due primarily by changes in the Earth’s orbit — see Human-caused Arctic warming overtakes 2,000 years of natural cooling, “seminal” study finds.
- Thus, the rate of human-driven warming in the last century has exceeded the rate of the underlying natural trend by more than a factor of 10, possibly much more. And warming this century on our current path of unrestricted greenhouse gas emissions is projected to cause a rate of warming that is another factor of 5 or more greater than that of the last century. We are punching the climate beast — and she ain’t happy about it!
Back to the investigation of attempted murder — and the ‘innocent victim’ who may have been killed in the attempt. The folks who don’t follow climate science closely have been trumpeting a new paper “A Statistical Analysis of Multiple Temperature Proxies: Are Reconstructions of Surface Temperatures Over the Last 1000 Years Reliable?” by McShane and Wyner about to be published in Annals of Applied Statistics. Supposedly it is fatal to the Hockey Stick.
Here is the police lineup. Take a look at three independent reconstructions of the past one to two millennia and the new one by the statisticians — and see if you can pick out which one allegedly killed the others (with apologies to Deltoid): | <urn:uuid:3e1d97c6-b7d4-40d7-8c12-0d5712ba08c2> | 2.953125 | 577 | Personal Blog | Science & Tech. | 32.143074 |
Letter to the Editor
Effects of dust on light-curves of ϵ Aurigae-type stars
Astronomical Institute, Slovak Academy of Sciences, 05960 Tatranska Lomnica, Slovak Republic
Received: 23 May 2011
Accepted: 15 July 2011
Context.ϵ Auriga is one of the most mysterious objects in the sky. Previous modeling of its light-curve assumed a dark, inclined, non-transparent or semi-transparent dusty disk with a central hole. The hole was necessary to explain the light-curve with a sharp mid-eclipse brightening.
Aims. The aim of the present paper is to study the effects of dust on the light-curves of eclipsing binary stars and to develop an alternative physical model for ϵ Aur-type objects that is based on the optical properties of dust grains.
Methods. The code Shellspec was modified to calculate the light-curves and spectra of these objects. The code solves the radiative transfer along the line of sight in interacting binaries. Dust and angle-dependent Mie scattering were included in the code for this purpose.
Results. Our model of ϵ Aur consists of two geometrically thick flared disks: an internal optically thick disk and an external optically thin disk, which absorbs and scatters radiation. Disks are in the orbital plane and are almost edge-on. We argue that there is no need for a highly inclined disk with a hole to explain the current eclipse of ϵ Aur even if there is a possible shallow mid-eclipse brightening. We demonstrate that phase-dependent light scattering and the optical properties of the dust can have a significant effect on the light-curves of these stars and can even produce a mid-eclipse brightening. This is a natural consequence of the strong forward scattering. We also demonstrate that shallow mid-eclipse brightening might result from eclipses by nearly edge-on flared (dusty or gaseous) disks.
Key words: accretion, accretion disks / scattering / binaries: eclipsing / circumstellar matter / stars: individual:ϵAur
© ESO, 2011 | <urn:uuid:384e9aca-ca86-4b0b-8e26-d921ed9432dc> | 2.75 | 453 | Academic Writing | Science & Tech. | 42.312516 |
Citizen Science Goes to Sea
The Royal Navy was taught to be very thorough during World War I. At sea, despite battles and storms, they recorded the weather every four hours dutifully into logbooks. Good thing, too. Little did those sailors realize that 100 years later, those books would be digitized (huh?) and distributed on the internet (the what?) for citizen scientists to record for a noble purpose.
Universe Today puts it this way:
The project is designed to provide a detailed map of the world’s climate around 100 years ago, which will help tell us more about the climate today. Anyone can take part, read the logs, follow events aboard the vessels and contribute to this fun and historical project, which could tell us more about our climate’s future.
How can old data help us see into the future? We asked Academy researcher Peter Roopnarine.
One method of verification is to apply the models to reconstructions of past climate. That only works, of course, if we have actual climate measures of the past. We've kept pretty good instrument measures for almost 200 years for various parts of the globe, and excellent records for the past 100 years. But most of those records are land-based, and the models utilize both land and sea-based parameters. So this project is searching for sea-based data, using nautical logs from the Royal Navy.
An article in Wired confirms this:
Climate scientists can feed hundreds of individual observations of the weather, temperature and air pressure into atmosphere models to build weather maps of the entire globe. Data on the ocean, which is a good store of heat, can provide information on what was happening on land as well.
It sounds like a fun way to relive history and help climate scientists at the same time. And the effort is fun and easy, too. There’s a great video showing you how to get started and the process includes maps and old images to help put you onboard. | <urn:uuid:aacfe9bf-936b-41d3-9842-dd0db05946cc> | 3.5 | 409 | Personal Blog | Science & Tech. | 54.271441 |
Poisson's equation is a partial differential equation named after the French mathematician and physicist Simeon-Denis Poisson. Derived from Coulomb's law and Gauss's law, it is a second-order partial differential equation used for solving problems, such as finding the electric potential for a given charge distribution, or modeling gravitational fields. It is commonly used in the fields of electrostatics, mechanical engineering, and theoretical physics.
Chegg is for students
See what's inside! | <urn:uuid:893bd934-3cac-4b31-8aa1-9dd27a7494c7> | 3.359375 | 100 | Knowledge Article | Science & Tech. | 29.481579 |
Another Test of the CLAW Hypothesis: What do the results suggest about the ability of oceanic phytoplankton to buffer earth's climate against greenhouse-gas-induced global warming?
Medieval Warm Period Record of the Week
This issue's Medieval Warm Period Record of the Week comes from the Western Slope of the Northern Okinawa Trough, East China Sea.
Subject Index Summary
Medieval Warm Period (Regional - Africa): What do we know about it? And how did we figure it out?
Tropical Cyclone Genesis: How is it affected by rising sea surface temperatures, according to a recently modified model?
Australian-Region Tropical Cyclone Characteristics: How have they varied over the last 3.5 decades?
Rapid Evolution of a Plant in Response to a Change in Climate: What life history traits were altered? ... and how rapid were the alterations?
The Carbon Balance of Old-Growth Forests: Is it positive, neutral or negative?
Leaf-Galls and Leaf-Mines of Mature Oak Trees: How are they affected by medium-term atmospheric CO2 enrichment? | <urn:uuid:03d56e2d-9746-4891-9c0f-e17e533b2763> | 3.046875 | 235 | Content Listing | Science & Tech. | 42.576429 |
An oxidizing agent is a chemical substance that takes electrons from other substances. Oxidizing agents, sometimes called oxidizers or oxidants, are missing electrons and take them from other things that have electrons. The oxidizing agent is reduced as it gains electrons. The substance the electrons are taken from is the reducing agent. It is oxidized as the electrons leave. | <urn:uuid:4f358a94-f974-4973-9cb5-1ac966d80470> | 3.171875 | 73 | Knowledge Article | Science & Tech. | 25.658 |
How Does Lightning Form?
Lightning is an electrical current and occurs within thunderclouds, or cumulonimbus clouds. In these clouds, small pieces of ice collide into each other creating an electrical charge. After a while, the cloud fills up with electrical charges. Positive electrical charges form at the top of the cloud and negative electrical charges form at the bottom of the cloud, closest to the surface of the Earth.
On the ground, a positive electrical charge builds up on the ground and concentrates around things that stick up, such as mountains, houses, telephone poles and trees. The positive charge streams up from the ground and connects with negative charge reaching down from the cloud (opposites attract!) creating the lightning strike!
Take the Earth Gauge Kids quiz to learn how thunder is created!
All images courtesy of NOAA.
Learn More about Lightning!
- You can determine how far away a thunderstorm is by doing math! Start off by counting the number of seconds between a flash of lightning and the next boom of thunder. Once you have that number, divide it by five to determine the distance to the lightning in miles. For example, if you count 10 seconds between a flash of lightning and the next boom of thunder, the thunderstorm is about two miles away.
- Lightning can strike up to 10 miles away from a storm! Always remember “When Thunder Roars, Go Indoors!” Take cover immediately when you hear thunder or see lightning!
- Sometimes lightning will give you a few seconds of warning before it strikes. For example, your hair will stand on end, your skin will tingle, palms get sweaty or a metallic taste in your mouth. Yuck!
Both images courtesy of NOAA. | <urn:uuid:345eb0ff-58f8-4f3a-b128-d7529c193295> | 4.03125 | 355 | Knowledge Article | Science & Tech. | 59.38509 |
By OurAmazingPlanet Staff:
Some of Asia's most magnificent animals are at a crossroads and may not survive if steps aren't taken to save them, an environmental group announced today (Sept. 5) at the World Conservation Congress in Jeju, Korea.
The Wildlife Conservation Society released a list of animals in danger of extinction, including tigers, orangutans, Mekong giant catfish, Asian rhinos, Asian giant river turtles and Asian vultures.
SCROLL DOWN FOR PHOTOS
The group said the problem could be solved by following the "Three R's Approach": recognition, responsibility and recovery.
A good example of a species saved from the brink is the American bison. In this case the iconic animal's imminent demise was recognized, responsibility for its survival was taken by conservationists and politicians, and it has recovered somewhat.
But if this approach isn't followed, Asian animals on the list could go the way of the American passenger pigeon, and die off, the WCS warned.
Each Asian species on the list faces daunting challenges from a variety of factors including habitat loss and illegal hunting and trade. Nevertheless, the group said it believed that Asian governments have the ability and financial means to prevent these species from going extinct.
The tiger may be going the way of the bison, since India has taken some steps to protect it and encourage its recovery. Orangutans face a bleaker future, with widespread conversion of its habitat into palm oil plantations reducing wild populations. Asian rhinos and giant river turtles face relentless poaching in the illegal wildlife trade, while Asian vultures have been nearly wiped out due to poisoning. Mekong giant catfish numbers have also plummeted due to overfishing.
The WCS warned that time is running out. Two large mammal species in Asia have recently gone extinct, including the kouprey, a type of wild cattle once found in Southeast Asia, and the baiji, a species of Chinese freshwater dolphin.
- Asian Species on the Edge of Extinction
- Only Known Footage of Extinct Wild Ox | Video
- 10 Species You Can Kiss Goodbye
Copyright 2012 OurAmazingPlanet, a TechMediaNetwork company. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
All photos and captions below courtesy of The Wildlife Conservation Society.
© Eleanor Briggs Thousands of years ago, ranged from China through Southeast Asia to Indonesia. Now just restricted to parts of Sumatra and Borneo. Most populations of both species are located outside protected areas, in forests that are exploited for timber production or being converted to agriculture. Bornean orangutan - 50 percent decline during the last 60 years, as a result of habitat loss due to conversion of forest to agriculture and fires. Between 45,000 and 69,000 individuals remain. Habitat loss, poaching, and the pet-trade are major threats across Borneo. Sumatran orangutan - 80 percent decline over the last 75 years; approximately 7,300 individuals remain. Most remaining populations are in Aceh Province. Pressure on forests is increasing as a result of the recent peace accord, and a dramatic increase in demand for timber and other natural resources after the December, 2004 tsunami.
© Stephen Leatherwood Extinct: A freshwater dolphin called a Baiji
Mekong Giant Catfish
©WCS Endemic to the Mekong basin. Local fisheries began to report the disappearance of this fish in the 1970s. Current population size is unknown, but a decline of more than 80 percent since 1990 can be estimated from past annual catch records. Fishing effort in the Mekong basin is increasing, and the loss of migratory routes through the construction of dams may also have a negative impact on fish abundance in the river.
© Dennis deMello/WCS Three species, all suffered from dramatic population declines and range shrinkages. Greater one-horned rhino - well protected in some parts of India, but 70 percent of population in one National ParkP (Kaziranga), and remaining populations fragmented, some declining. Sumatran rhino - once widespread throughout Southeast Asia, now only remaining in Sabah and few fragmented parts of Indonesia, with a total of probably only about 250 animals remaining in the wild. Javan rhino - again, once widespread across Southeast Asia, but by 2000, limited to two wild populations, one each in Vietnam and Java. Last year, Vietnam population declared extinct. So now just one population remaining, in Ujong Kulong, possibly numbering only about 40 animals.
© Julie Larsen Maher/WCS Only about 3,200 remaining, and of those, only about 1,000 breeding females. Occupy only 7 percent of their historic range, and 70 percent of the remaining population is in 6 percent of the current range. But we know what to do to save them. In areas with good habitat, with tigers and prey protected effectively against poachers, populations are recovering. Example: Nagarahole National Park in India.
©WCS Group of turtles closest to extinction. Heavily harvested and exploited for flesh and eggs. Five species are critically endangered and one is endangered. So few individuals remain in some cases that assurance colonies are the only hope for species survival. Batagur baska - Northern River Terrapin - Previously highly abundant in river deltas of India and Myanmar. Now, no known nesting areas, and only a few individuals remain in the wild. Concerted effort is needed to bring captive individuals together for breeding groups. B. trivittata - Burmese Roofed Turtle - Considered extinct from 1930s to 2002 when remnant populations were discovered. Only 5-7 breeding adult females in the wild. Almost 400 hatchlings have been transferred to headstarting facilities. Plans for release of 5-year old headstarted males. B. affinis - Southern River Terrapin - Previously considered one species with B. baska. Only isolated populations remain, but poaching of turtles and eggs still occurs. Conservation projects have only been able to secure hatchlings and adult mortality has not yet been effectively addressed. B. kachuga - Red-crowned Roofed Turtle - Exists primarily along the Chambal River in central India, with isolated populations in Bangladesh. Approximately 500 adult females remain. Breeding programs have produced over 4000 hatchlings. B. borneoensis - Painted Terrapin - Global status not fully elucidated; most populations in serious decline. Suffered from uncoordinated conservation efforts. 200 head-started ndividuals have been released, but all rivers with viable populations have not been identified.
©WCS Declined by more than 90 percent across the Indian subcontinent. Direct killing account for 10 percent of recorded vulture deaths, but the main cause of mortality has been diclofenac, an anti-inflammatory drug used for veterinary reasons in cattle that is toxic to vultures when the carcass is consumed. Populations remain stable in Cambodia where the government has placed restrictions on the use of diclofenac. Critically Endangered Species: Red-headed Vulture (Sarcogyps calvus) White-rumped Vulture (Gyps bengalensis) Slender-billed Vulture (Gyps tenuirostris)
©WCS Extinct: The Kouprey - a mysterious species of wild cattle | <urn:uuid:2b9ba470-6ea0-4a93-a6d2-4e4d69a06c04> | 3.0625 | 1,514 | Truncated | Science & Tech. | 34.923511 |
Total renewable water resources: 0.03 cu km (1999)
Definition: This entry provides the long-term average water availability for a country in cubic kilometers of precipitation, recharged ground water, and surface inflows from surrounding countries. The values have been adjusted to account for overlap resulting from surface flow recharge of groundwater sources. Total renewable water resources provides the water total available to a country but does not include water resource totals that have been reserved for upstream or downstream countries through international agreements. Note that these values are averages and do not accurately reflect the total available in any given year. Annual available resources can vary greatly due to short-term and long-term climatic and weather variations.
Source: CIA World Factbook - Unless otherwise noted, information in this page is accurate as of February 21, 2013
© 2013 IndexMundi. All rights reserved. | <urn:uuid:88ad0e61-8c8d-4f1f-bf9a-8de4972654b6> | 2.984375 | 174 | Knowledge Article | Science & Tech. | 24.384947 |
Synchrotron radiation was initially
sapping energy from circulating electron beams and upsetting
calculations. Fortunately physicists learned that the fan of
synchrotron radiation "waste" from high energy electron
rings could be used to probe the structure of a wide range
There are many views on how synchrotrons and synchrotron
light developed. Below, I have written one of the views.
On April 24, 1947, Herb Pollock, Robert Langmuir, Frank
Elder, and Anatole Gurewitsch saw a gleam of bluish-white
light emerging from the transparent vacuum tube of their
new 70MeV electron synchrotron at General Electric's
Research Laboratory, Schenectady, New
York: Synchrotron radiation had been seen. Here is a picture
of the first synchrotron radiation seen. The first
seen synchrotron radiation is indicated by arrow in the picture
on the left.
(The first seen
But the idea of
synchrotron light goes as far back as the 19th century.
A French physicist
Alfred Lienard of the Ecole des Mines in Paris described the
concept of retarded potentials in the calculation of the
effects due to the motion of charged particles, and worked
out a basic theory of what is now known as synchrotron
radiation. Lienard's theory is still followed in
modern physics text books today. This work was supplemented
by Emil Wiechert, so the formalism is generally known as the
Lienard-Wiechert potentials. Lienard's paper appeared just
after the discovery of the electron by J. J. Thomson exactly
one hundred years ago at Cambridge. However an embryonic
idea of synchrotron radiation can be traced farther back
than Lienard's paper to 1867, to Ludwig Lorenz.
(The brightness of light beam produced by first,
second, and third generation Synchrotrons)
The next major
development of synchrotron radiation theory came in 1908
from G. A. Schott, first as an student of Cambridge, then at
Aberystwyth, Wales in a prizewinning paper about mechanical
reactions of electromagnetic radiation. The idea of
synchrotron radiation lay dormant for a few decades before
synchrotron radiation was seen April 24, 1947. From there, continuous advancement of
synchrotrons occurred and the brightness of the light
produced also kept increasing. Third
generations synchrotrons are the most advanced ones today
and the radiation produced by them is exceptionally
brighter than the first seen radiation (see picture below).
(Today's Synchrotron radiation beam)
light source building, Saskatoon, SK)
Today, there are more than fifty synchrotrons worldwide but
the facilities vary in their capacity and the brightness of
the light they produce.
source facility (Synchrotron) is one of the few "third
generation" synchrotrons (most advanced)
and is among the five most powerful synchrotrons in the
The top three world's most powerful synchrotrons are "Advanced
Photon Source (APS)" in the United States of America, "European
Synchrotron Radiation Facility (ESRF)" and the "SPring-8"
facility in Japan. The SPring-8 synchrotron is the most powerful and the
biggest synchrotron in the world. | <urn:uuid:6dd51c91-a384-4e06-97f8-c75864499b87> | 4 | 757 | Knowledge Article | Science & Tech. | 37.24572 |
By James Barrante
Scientists tend to throw words around that we sometimes mistakenly assume the layperson will understand. So it should not surprise us when laypeople or individuals from other areas of science misinterpret a word, or do not use it correctly. One such word is "entropy."
People generally associate the word entropy with some idea of order or disorder. What most laypeople do not understand is that the word only has specific meaning in an area of physics called "thermodynamics," and the systems to which the systems apply are those at the atomic level.
For example, I have heard people say a shuffled deck of cards is at a higher entropy than one ordered by suit and number. Nothing could be further from the truth. Or, similarly, that a messy bedroom is at a higher entropy than a tidy bedroom. They will use as an argument, "What are the chances that if you throw an ordered deck of cards in the air and have it fall, it will return with all the cards ordered by suit and number?" My answer to this is a question. "What are the chances that if you throw a shuffled deck of cards in the air and have it fall, it will return with the cards ordered exactly as they were in the shuffled deck before you threw it in the air?" Any ordering of the deck is equally probable. They are all at the same entropy.
So what is entropy? A simple definition is that it is a measure of lost work. For example, if you drop a book to the floor, it does no work as it falls. You could have done work by dropping the book. That is, you could have rigged the book with a pulley and rope, so that as it fell, it lifted another object, doing work in the process. That work is lost forever by just dropping the book.
You might argue, "I'll lift the book up and then drop it again with the pulley system in place and recover that lost work." Sorry! Once the book has fallen, it will take work to lift the book up again.
No, that work can never be recovered, and the work lost will cause the entropy of the universe to increase.
So every time you design a machine and it doesn't do as much work as thermodynamically possible (that's where efficiency comes in), the entropy of the universe increases by an amount equal to the lost work.
So what about this order-disorder thing? This is a more subtle and, perhaps, a more accurate description of entropy. It has to do with the energy states a system can occupy. All particles, atoms, and molecules occupy energy states. And the more energy states available to be occupied, the higher the entropy.
If we were to cool a system to absolute zero (the lowest possible temperature, equaling minus 460), only one energy state is possible, and the entropy of the system is zero.
As one heats the system up, its entropy increases, since more energy states become available (hot solids have more energy states than cool solids, liquids more states than solids, gases more states than liquids). Liquids are more disordered than solids, gases are more disordered than liquids, entropy increases from solid to liquid to gas.
You can excite an electron (those little negative things zipping around the nucleus of an atom like planets around the sun) in an atom to a higher energy by zapping it with electricity.
The electron will then drop back to a lower energy state, releasing a photon (a particle of light) to the surroundings. Why? Most people would say that it is because the electron is lowering its energy. But the energy lost by the electron is gained by surroundings. It's the emitted photon that drives the process.
There are more energy states for the photon in the surroundings than in the atom. Its entropy increases when it is emitted.
It's entropy, not energy, that drives the process.
James Barrante of Cheshire is a retired college professor of physical chemistry. | <urn:uuid:6598d806-d4d9-4b6d-9d26-9d120bc9fe7e> | 3.3125 | 827 | Nonfiction Writing | Science & Tech. | 53.624979 |
From Netherlands Organization for Scientific Research
DNA's oscillating double helix hinders electrical conduction DNA has an oscillating double-helix structure. This oscillating means that the DNA molecules conduct electricity much less well than was previously thought. Ultrafast cameras were one of the devices the researchers from Amsterdam used to demonstrate this.
It turns out the DNA does not have a rigid regular structure as stated in textbooks. In reality the double helix of DNA forms a very dynamic chaotic system. The rigid structure in textbooks should be regarded as the average position of many structures taken over a period of time.
The Amsterdam researchers showed that the chaotic movements limit the electrical conductivity properties of DNA. Electrical conductivity, even if it is imperfect, is of vital importance for the cell. For example, the cell uses electrons from the charge transfer in DNA to repair damaged bonds.
According to the researchers the electrical conductivity would be much better if DNA had a fixed double-helix structure in which the individual building blocks were neatly stacked on top of each other.
The results have consequences for scientists who are developing new molecular microelectronics. In this sort of experimental electronics the DNA molecules would have to be able to initiate a range of reactions by means of charge transfer. The electronics specialists must now take the inefficient electrical conductivity of DNA into consideration.
The DNA examined by researchers included a piece of DNA with the form of a hair clip. It is similar to an important piece of RNA in the HIV virus. Researchers incorporated fluorescent molecule groups in a very specific manner. They then bombarded the piece of DNA with extremely short laser pulses. A special type of camera registered how the molecule fluoresced.
The experimental set-up of the Amsterdam researchers can observe movements or vibrations which occur in one millionth of a millionth of a second. Or put scientifically the set-up has a resolution of a picosecond. To put this into perspective: normal film cameras take 24 pictures per second and only detect the vibration if it lasts longer than 0.02 seconds.
Further information can be obtained from Olaf Larsen (Biophysics and Physics of Complex Systems, Free University of Amsterdam), tel. 31-20-422-0903 or 31-62-500-7670 (home), 31-20-444-7426 (work), fax 31-20-444-7999 (work), e-mail firstname.lastname@example.org and email@example.com. A short film (all rights reserved) about oscillating DNA can be found on the Internet: http://www.nat.vu.nl/n_s_old/vakgroepen/bio/english/research/index4.html. The defence of the doctoral thesis will take place on 3 October 2002. Mr Larsen's supervisor is Prof. Rienk van Grondelle.
The research was funded by the Netherlands Organisation for Scientific Research (NWO). | <urn:uuid:7e6bd000-cca1-42d2-8d50-4384a0da8911> | 3.609375 | 609 | Knowledge Article | Science & Tech. | 45.555616 |
Using the left mouse button, select piece and drag into position. Pressing the right mouse button rotates piece. If you need a hint, press the "V" key to view the whole image. Change the number of pieces: 9 | 24 | 48 | 160.
Tall objects such as trees and skyscrapers are commonly struck by lightning. Mountains also make good targets. The reason for this is their tops are closer to the base of the storm cloud. Remember, the atmosphere is a good electrical insulator. The less insulation the lightning has to burn through, the easier it is for it to strike. However, this does not always mean tall objects will be struck. It all depends on where the even if the tree line is close by. Learn more about lightning, go to JetStream - an Online School for Weather. | <urn:uuid:cdd3e77a-74a8-4b6a-b376-abb1c8f3ad6b> | 2.796875 | 169 | Tutorial | Science & Tech. | 71.541961 |
>100 keV Electrons (90° detector)
The red box in the plot shows the location of the beginning of
the satellite track for this plot. The red triangle
indicates the location of the end of the track. Data gaps or missing
orbits appear as gaps in the satellite track around the earth.
Select another plot from the list. | <urn:uuid:46ede9f7-153f-4e6f-a59c-034050cd07d3> | 2.765625 | 74 | Structured Data | Science & Tech. | 69.181776 |
Permitted Context: %Body.Content
Content Model: %Body.Content
The DIV element is used with the CLASS attribute to represent
different kinds of containers, e.g. chapter, section, abstract, or
appendix. For example:
<P>TheChieftain product range is the white hot hope for the
coming year. This report sets out how to position Chieftain
against competing products.
- An SGML identifier used as the target for hypertext
links or for naming particular elements in associated style sheets.
Identifiers are NAME tokens and must be unique within the scope of the
- This is one of the ISO standard language abbreviations,
e.g. "en.uk" for the variation of English spoken in the United Kingdom.
It can be used by parsers to select language specific choices for
quotation marks, ligatures and hypenation rules etc. The language
attribute is composed from the two letter language code from ISO 639,
optionally followed by a period and a two letter country code from ISO
- This a space separated list of SGML NAME tokens and is
used to subclass tag names. For instance, <DIV CLASS=APPENDIX>
defines a division that acts as an appendix. By convention, the class
names are interpreted hierarchically, with the most general class on
the left and the most specific on the right, where classes are
separated by a period. The CLASS attribute is most commonly used to
attach a different style to some element, but it is recommended that
where practical class names should be picked on the basis of the
element's semantics, as this will permit other uses, such as
restricting search through documents by matching on element class
names. The conventions for choosing class names are outside the scope
of this specification.
- The ALIGN attribute can be used to explicitly specify
the horizontal alignment of paragraphs within a division:
- Paragraphs are rendered flush left (the
- Paragraphs are centered.
- Paragraphs are rendered flush right.
- Text lines are justified where practical,
otherwise this gives the same effect as the default align=left
- The NOWRAP attribute is used when you don't want the
browser to automatically wrap lines. You can then explicitly specify
line breaks in paragrphs using the BR element.
- This attribute is common to all block-like elements. When
text flows around a figure or table in the margin, you sometimes want
to start the division below the figure rather than alongside it. The
CLEAR attribute allows you to move down unconditionally:
- move down until left margin is clear
- move down until right margin is clear
- move down until both margins are clear
Alternatively, you can decide to place the element alongside the
figure just so long as there is enough room. The minimum width needed
is specified as:
- clear="40 en"
- move down until there is at least 40 en units free
- clear="100 pixels"
- move down until there is at least 100 pixels
The style sheet (or browser defaults) may provide default minimum
widths for each class of block-like elements. | <urn:uuid:d3a95f20-e5fe-45eb-9f46-a45cfc31d2a0> | 3.234375 | 675 | Documentation | Software Dev. | 41.383765 |
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.
September 24, 1996
Explanation: If the thick clouds covering Venus were removed, how would the surface appear? Using an imaging radar technique, the Magellan spacecraft was able to lift the veil from the Face of Venus and produce this spectacular high resolution imageof the planet's surface. Red, in this false-color map, represent mountains, while blue represents valleys This 3-kilometer resolution map is a composite of Magellan images compiled between 1990 and 1994. Gaps were filled in by the Earth-based Arecibo Radio Telescope. The large yellow/red area in the north is Ishtar Terra featuring Maxwell Montes, the largest mountain on Venus. The large highland regions are analogous to continents on Earth. Scientists are particularly interested in exploring the geology of Venus because of its similarity to Earth.
Authors & editors:
NASA Technical Rep.: Sherri Calvo. Specific rights apply.
A service of: LHEA at NASA/ GSFC | <urn:uuid:96d8fee4-4956-405c-a0b7-693c49ee5df0> | 4.21875 | 227 | Knowledge Article | Science & Tech. | 34.100259 |
Capturing celestial crinoline
October 2012: Learn how to photograph one of the sky’s more colorful phenomena: atmospheric coronae.
August 28, 2012
|When thin clouds or tiny airborne particles wash over the Sun or Moon in the sky, a colorful phenomenon called the atmospheric corona may encircle these bodies like a crinoline skirt. The spectacle consists of two parts: a bright glow (known as the aureole) with a smoggy orange fringe centered on the object, and a series of fainter colored rings (graduating from blue on the inside to red on the outside) surrounding the aureole. You can photograph both with DSLR or manual cameras. Here’s how.|
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Mira: "Wonderful" Star Reveals its Hot Nature
The Chandra image shows Mira A (right), a highly evolved red giant star, and Mira B (left), a white dwarf. To the right of the image is an artist's conception of the Mira star system. Mira A is losing gas rapidly from its upper atmosphere via a stellar wind. Mira B exerts a gravitational tug that creates a gaseous bridge between the two stars. Gas from the wind and bridge accumulates in an accretion disk around Mira B and collisions between rapidly moving particles in the disk produce X-rays.
The separation of the X-rays from the giant star and the white dwarf was made possible by the superb angular resolution of Chandra, and the relative proximity of the star system, at about 420 light years from Earth. The stars in Mira AB are about twice as far apart as Pluto is from the Sun.
The ability to distinguish between the interacting stars allowed a team of scientists to observe an X-ray outburst from Mira A. An ultraviolet image made by the Hubble Space Telescope was key to identifying the X-ray outburst with the red giant star.
Mira A (or simply, Mira) was named "The Wonderful" star in the seventeenth century because its brightness was observed to wax and wane over a period of about 330 days. In this advanced red giant phase of Mira A's life, its diameter has swollen to about 600 times that of the Sun and it is pulsating, due to increasingly energetic nuclear reactions in its core.
Mira A is now approaching the stage where its nuclear fuel supply will be exhausted, and it will collapse to become a white dwarf. In contrast, Mira B has already reached the white dwarf stage, and is about the size of the Earth, but about a quarter million times more massive.
Before this observation it was assumed that all the X-rays came from a hot disk surrounding Mira B, so the detection of an X-ray flare from the red giant star came as a surprise. This outburst was likely an indirect consequence of the internal turmoil in Mira A.
X-ray studies of the Mira star system may also provide better understanding of interactions between other binary star systems consisting of a "normal" star and a collapsed star such as a white dwarf, black hole or a neutron star. | <urn:uuid:92213985-05b2-4249-821c-e30f5c694079> | 3.875 | 487 | Knowledge Article | Science & Tech. | 49.125035 |
Everyone has seen waves on water, heard sound waves and seen light waves. But, what exactly is a wave? Of course, the goal of this course is to answer this question for you. But for now you can think of a wave as a traveling or oscillatory disturbance in some continuous medium (air, water, the electromagnetic field, etc.). As we shall see, waves can be viewed as a collective e↵ect resulting from a combination of many harmonic oscillations. So, to begin, we review the basics of harmonic motion.
harmonic oscillition, traveling wave, chapter 1, one
Torre, Charles G., "01 Harmonic Oscillations" (2012). Foundations of Wave Phenomena. Book 22. | <urn:uuid:0744ecf1-0f8f-4e6b-8c2e-49db34ae93a9> | 3.8125 | 151 | Truncated | Science & Tech. | 54.74241 |
The big issues
Causes of speciation
In the fruit fly example, some fruit fly larvae were washed up on an island, and speciation started
because populations were prevented from interbreeding by geographic isolation. Scientists think that geographic
isolation is a common way for the process of speciation to begin: rivers change course, mountains rise,
continents drift, organisms migrate, and what was once a continuous population is divided into two or more
It doesn't even need to be a physical barrier like a river that separates two or more
groups of organisms it might just be unfavorable habitat between the two populations that keeps them from
mating with one another.
Reduction of gene flow
However, speciation might also happen in a population with no specific extrinsic barrier to gene flow.
Imagine a situation in which a population extends over a broad geographic range, and mating throughout
the population is not random. Individuals in the far west would have zero chance of mating with individuals
in the far eastern end of the range. So we have reduced gene flow, but not total isolation. This may or
may not be sufficient to cause speciation. Speciation would probably also require different selective
pressures at opposite ends of the range, which would alter gene frequencies in groups at different ends
of the range so much that they would not be able to mate if they were reunited.
Even in the absence of a geographic barrier, reduced gene flow across a species' range can encourage
page 4 of 7 | <urn:uuid:822a4a94-fdc3-4858-8b5a-7360ca8fd846> | 3.78125 | 308 | Academic Writing | Science & Tech. | 25.726073 |
Potential energy stored in the capacitor is U=1/2CV^2. Dielectric with d=4 will increase the capacitance by 4. Calculate the energy stored in the capacitor before and after the dielectric is inserted - the difference will be the work done to insert the dielectric.
The justification why ΔU is the work done in this case is somewhat fishy, at least from what I can think of at the moment. There is another example, where you have two connected capacitors with no battery and a dielectric is inserted in one of them causing change of charge. Calculating the total energy in both capacitors before and after the insertion shows that there is a change in energy. In that case it's easy to argue that the change of energy comes from work because there are no other sources - the two capacitors are a closed system. In your problem there is a transfer of energy from the battery, so...
What's the source of the problem? | <urn:uuid:905536bf-6bf4-4390-88c3-36a2f76391c2> | 3.21875 | 204 | Comment Section | Science & Tech. | 51.367125 |
MARS, in astronomy, the outermost of the four earth-like planets revolving about the sun. Its orbit lies completely outside that of the earth, its mean distance from the sun being 141,500,000 miles, and with the single exception of the orbit of Mercury, it has the most eccen tric orbit of the solar system, the greatest dis tance of the planet from the sun exceeding its least distance by 26,400,000 miles. Mars occu pies 687 days in completing the circuit of its path, so that this is the length of the year on this planet. As the orbits of Mars and of the earth both approximate to circles, having the sun near their centres, it follows that the dis tance apart of these planets varies enormously. When Mars, the earth and the sun are in one straight line, Mars and the earth being on the same side of the sun, this distance may be so little as 35,500,000 miles, while if the former planet is beyond the sun in the most remote part of its orbit, the distance may be so great as 248,600,000 miles. In the former case Mars is more favorably situated for observation from the earth than any other planet in the solar system; the planet Venus when nearest us is, indeed, much less far away, but at this time it is the dark, or night, side of Venus that is turned toward us, while when we are nearest to Mars it is the fully illuminated, day side of the planet upon which we look. On account of the eccentricity of the orbit of Mars, its dis tances from the earth differ greatly at different oppositions; if an opposition occurs while Mars occupies that part of its orbit which is nearest the sun, the distance may be so small as 35,500, 000 miles, while if at this time Mars is at the point of its orbit most remote from the sun, even at the instant of nearest approach the distance may exceed 61,600,000 miles. The in terval between successive close approaches of Mars and the earth is 780 days, much the long est synodical period in the planetary system, — while the usually favorable close approaches occur in groups separated by 15 or 17 years. These favorable oppositions always occur dur ing the months of August or September; the date of the last one was 1909, while the three succeeding ones will be seen in the years 1924, 1939 and 1941. It is at these times that very unusually favorable opportunities are afforded for studying the surface of the planet. The day on Mars is 24 hours, 37 minutes, 22.67 seconds in length, being thus but little longer than our own; the axis of the planet is inclined at an angle of 24° 0' to the axis of its orbit, so that spring, summer, autumn and winter succeed one another there in almost precisely the same way as with us, but the Martian seasons arc each of nearly twice the duration of ours since the year is nearly two of our years in length. (The inclination of the earth's
axis is 23° 27').
In 1877, Asaph Hall, of Washington, dis covered that Mars is attended by two minute satellites to which he gave the names Phobos and Deimos. Both of these bodies are very minute objects, and as may be seen from the following table their motions are in many re spects unique among the satellites of the solar system.
The distance away of each of the moons from the planet is remarkably small; thus, even Deimos is less than one-seventeenth as far away from Mars as our own moon is from the earth, while Phobos is separated from the planet's surface by less than one diameter of the planet. The latter moon is, in fact, so close to Mars that it would remain forever invisible to any observers on the planet in higher latitudes than 69 degrees, being hidden by the curvature of the planet's surface. But still more striking is the apparent motion of these bodies as it would be witnessed from the surface of Mars itself. As Phobos completes a revolution in 7 hours 39 minutes. which is far less than the time of the rotation of the planet, it follows that this moon would be seen to rise in the west, run rapidly eastward among the stars and finally set in the east_ Eleven hours later it would again appear in the west, to repeat the same retrograde motion. Deimos, though rising in the east in the usual way, would mount the sky very slowly: the various constellations would be seen to drift past it and the moon would not finally attain the western horizon until about 66 hours after rising. Both moons would be seen to go through their phases in the course of their peculiar motions. With such minute objects it is impossible for us to discern any measur able discs, but from observations of the amount of light which their surfaces reflect, their diam eters can be, at least approximately, determined. The figures of the above table are those found in this way at the Lowell Observatory. These indicate that Phobos, as seen from the nearest point on Mars, would appear somewhat larger than our moon does to us, though its surface would be but one-half as bright, while the ap parent diameter of Deimos would be but three minutes of arc. This satellite would therefore only be visible as a disc with difficulty to the naked eye; it would have merely the appear ance of a very brilliant star. | <urn:uuid:2694438a-2668-4afe-a47c-260ca3d65eaf> | 3.765625 | 1,113 | Knowledge Article | Science & Tech. | 45.44603 |
A little mouse called Delia lives in a hole in the bottom of a
tree.....How many days will it be before Delia has to take the same
Investigate the number of paths you can take from one vertex to
another in these 3D shapes. Is it possible to take an odd number
and an even number of paths to the same vertex?
You can trace over all of the diagonals of a pentagon without
lifting your pencil and without going over any more than once. Can
the same thing be done with a hexagon or with a heptagon?
Could you draw the shapes without removing your pencil from the
paper. Which ones were possible and which ones impossible?
These are the networks that Mithran, who is from Australia,
could follow. He has sent in his results and shown with arrows the
path that he took in completing the shapes. Try some for | <urn:uuid:c522f344-e4d8-4a53-afde-8a19de90e064> | 3.0625 | 187 | Tutorial | Science & Tech. | 66.606878 |
Loki, Io: New ground-based observations and a model describing the change from periodic overturn
Article first published online: 6 SEP 2006
Copyright 2006 by the American Geophysical Union.
Geophysical Research Letters
Volume 33, Issue 17, September 2006
How to Cite
2006), Loki, Io: New ground-based observations and a model describing the change from periodic overturn, Geophys. Res. Lett., 33, L17201, doi:10.1029/2006GL026844., and (
- Issue published online: 6 SEP 2006
- Article first published online: 6 SEP 2006
- Manuscript Accepted: 24 JUN 2006
- Manuscript Revised: 17 JUN 2006
- Manuscript Received: 5 JUN 2006
Loki Patera is the most powerful volcano in the solar system. We have obtained measurements of Loki's 3.5 micron brightness from NASA's Infrared Telescope Facility (IRTF) and have witnessed a major change in eruptive behavior. While Loki brightened by a factor of several every 540 days prior to 2001, from 2001 through 2004 Loki remained at a constant, intermediate brightness. We have constructed a quantitative model of Loki as a basaltic lava lake whose solidified crust overturns when it becomes buoyantly unstable. By altering the speed at which the overturn propagates across the patera, we can match our ground-based brightness data. In addition, we can match other data taken at other times and wavelengths. By slowing the propagation speed dramatically, we can match the observations from 2001–2004. Such slowing could be due to a small change in volatile content in the lava. | <urn:uuid:4342b6cf-b823-4d0b-8965-5de7a84c5de1> | 2.890625 | 342 | Academic Writing | Science & Tech. | 48.877022 |
Mission Type: Lander, Orbiter
Launch Vehicle: Titan IIIE-Centaur (TC-4 / Titan no. E-4 / Centaur D-1T)
Launch Site: Cape Canaveral, Florida, USA
NASA Center: Jet Propulsion Laboratory, Langley Research Center
Spacecraft Mass: 3,527 kg
1) imaging system
2) atmospheric water detector
3) infrared thermal mapper
1) imaging system
2) gas chromatograph mass spectrometer
4) x-ray fluorescence
5) biological laboratory
6) weather instrument package (temperature, pressure, wind velocity)
7) remote sampler arm
1) retarding potential analyzer
2) upper-atmosphere mass spectrometer
Deep Space Chronicle: A Chronology of Deep Space and Planetary Probes 1958-2000, by Asif A. Siddiqi, NASA Monographs in Aerospace History No. 24
NSSDC Master Catalog, http://nssdc.gsfc.nasa.gov/nmc/
Viking 1 was the first of a pair of complex deep space probes that were designed to reach Mars and collect evidence on the possibility (or lack thereof) for life on Mars.
Each spacecraft was composed of two primary elements, an orbiter (2,339 kilograms) and a lander (978 kilograms). The orbiter design heavily borrowed from the Mariner buses, while the lander looked superficially like a much larger version of the Surveyor lunar lander.
Prior to launch, the batteries of the first spacecraft were discharged, prompting NASA to replace the original first spacecraft with the second, which was launched as Viking 1.
After three midcourse corrections (on 27 August 1975 and 10 and 15 June 1976), the spacecraft entered orbit around Mars on 19 June 1976. Initial orbital parameters were 1,500 x 50,300 kilometers. The following day, when the orbiter began transmitting back photos of the primary landing site in the Chryse region, scientists discovered that the area was rougher than expected.
Using the new photos, scientists targeted the lander to a different site on the western slopes of Chryse Planitia. The lander separated from the orbiter, and after a complex atmospheric entry sequence, during which the probe took air samples, Viking 1 lander set down safely at 22.483° north latitude and 47.94° west longitude at 11:53:06 UT on 20 July 1976.
Once down, the spacecraft began taking high quality photographs (in three colors) of its surroundings. Instruments recorded temperatures ranging from -86°C (before dawn) to -33°C (in the afternoon). The seismometer on the lander was inoperable.
On 28 July, the lander's robot arm scooped up the first soil samples and deposited them into a special biological laboratory that included a gas chromatograph mass spectrometer. While some data could be construed as indicating the presence of life, a major test for organic compounds gave negative Results.
The lander continued to return daily (and then eventually weekly) weather reports until loss of contact on 1 February 1983. Further attempts to regain contact proved unsuccessful. The orbiter was shut down on 7 August 1980, after it ran out of attitude-control propellant. | <urn:uuid:aa8e2393-84ed-400b-841e-a01853b00570> | 3.359375 | 684 | Knowledge Article | Science & Tech. | 44.435871 |
“Petroleum-Eating Mushrooms To Decontaminate Our Most Polluted Sites”
“Rather than just waiting for nature to take its course, scientists are now speeding up the process by selecting fungi, microorganisms, and even trees to do the job in just a few years. Mohamed Hijri, a professor of biological sciences and researcher at the University of Montreal’s Institut de Recherche en Biologie Végétale (IRBV), has been engineering these toxic ecosystems. And he is succeeding.
“If we leave nature to itself, even the most contaminated sites will find some sort of balance thanks to the colonization by bacteria and mushrooms,” says Hiri on the University of Montreal’s website. “But by isolating the most efficient species in this biological battle, we can gain a lot of time.” | <urn:uuid:63f6a390-a99b-4a14-bed7-923c609c8080> | 2.84375 | 184 | Personal Blog | Science & Tech. | 30.185571 |
The American Alligator
The large american alligator, is a feared animal in the wild. It moves as quickly on land as in the water.
The American alligator moves as quickly on land as it does in the water. This alligator makes his home in the warm wetlands and swamps of Florida, Georgia, Texas, Louisiana, and Alabama. He is the largest of all crocodiles in the United States.
The alligator spends its time in its habitat. An adult alligator will eat any thing he finds: some of his favorites are birds, turtles and snakes. Young alligators eat shrimp, frogs, and fish. Most of its meals ore found in the water, but alligators also hunt larger prey on land. These animals are grabbed and pulled into the river and drowned. Then he will eat them, by taking large bites and swallowing them whole.
The male and female alligators mate at night. The male defends his mate against other males. The breeding season is from April to May. The female lies from twenty five to sixty eggs. She will lay these eggs in a nest on the shore. She covers the nest to protect her young from various predators. The eggs will hatch in two to three months. When the young have hatched, they will squeal out, to let their mother know they have hatched. The female will uncover the nest; the young are born fully developed. They are about one foot in size. They will leave the nest and begin feeding on their own. They do not reach full maturity until about six years of age.
Once the American Alligator was an endangered species, but due to conservation efforts they are no longer an endangered species. | <urn:uuid:376b1ed7-735c-40ca-ad1c-8d93420ecc0f> | 3.078125 | 342 | Knowledge Article | Science & Tech. | 59.881209 |
Take a pristine coral reef off the mangrove-forested coast of Belize, one that draws a handsome roster of fish and other sea creatures--and, therefore, a complement of scuba divers, sports fishermen, photographers, and other consumers of nature. Add an airstrip to serve these cash customers, then a hotel, then a seawall, then a golf course, then a desalination plant. In no time, thanks to the changes you've wrought on the coastal ecology, you'll have a dead reef in a dead patch of sea.
Such wanton destruction is the norm for today, writes science journalist Colin Woodard, who debarks from his travels on the world's seas with depressing and unremittingly bad news. One of the victims is the Black Sea of Eurasia, once a thriving extension of the Atlantic, now all but destroyed by "overfishing, oil spills, industrial discharges, nutrient pollution, wetlands destruction," and other ills. The ravaged Black Sea is mirrored in other places to which Woodard travels: the South Pacific, the Gulf of Mexico, the Antarctic. In such places significant ecological transformations are occurring, all in a very short period of time, all perhaps irreversible, all certainly dangerous to the health of the biosphere. "The oceans," Woodard urges his readers to consider, "are finite and destructible. Wastes dumped and drained into the ocean do not disappear; they are neither economic nor ecological externalities. Likewise, marine fish and animals are not commodities like iron, wheat, or broilers; they are wildlife." Adding to works such as Carl Safina's Song for the Blue Ocean, Woodard makes a clear and urgent call for the reversal of all this destruction and for the protection of the world's waters. --Gregory McNamee
-- Dieser Text bezieht sich auf eine vergriffene oder nicht verfügbare Ausgabe dieses Titels.
"[Woodard] successfully brings to life the fascinating mysteries of marine science [and] outlines strategies that, he contends, must be taken to save our seas."-Publishers Weekly. The Black Sea is already dead. Because of sea-level rise, an entire nation in the South Pacific, the Republic of the Marshall Islands, is being washed away. Throughout the Caribbean Sea, vast stretches of coral reef-called the "rainforests of the ocean" because of their diversity of life-are dying at increasingly rapid rates. The reefs along the entire north coast of Jamaica are dead. Ocean's End is not about the damage our oceans could suffer (and inflict) in ten or a hundred years, if we're not careful. It's an eyewitness account, in compelling and vivid detail, of the massive worldwide destruction that's already happened. | <urn:uuid:3da7e03e-872c-46d6-8dc4-b2bdc90dd613> | 2.734375 | 573 | Truncated | Science & Tech. | 40.777667 |
Scientists at the Laboratory for Laser Energetics of the University of Rochester, Rochester, N.Y., have developed a membrane that blocks gas from flowing through it when one color of light is shined on its surface, and permits gas to flow through when another color of light is used.
Eric Glowacki, a graduate student at the university, and Kenneth Marshall, research engineer, optical materials, invented the membrane, which reportedly is the first one whose permeability is controlled by light.
Applications could include those where gas flow must be cycled on and off but where making electrical or other hardware connections would be difficult. "Think in terms of very small or micro-scale apparatus that would need gas delivery — such as very small hand-held chemical analyzers, medical equipment, complex process equipment, or even nano-scale processes," says Marshall. Another possibility is the separation of straight-chain from branched-chain hydrocarbons, he adds.
The researchers create 400-mm pores in a commercial "Isopore" polycarbonate membrane and fill these with liquid crystals and a dye (Figure 2).
Then, when purple light illuminates the surface of the membrane, the dye molecules straighten out and the liquid crystals fall into line, which allows gas to easily flow through the holes. But when ultraviolet light illuminates the surface, the dye molecules bend into a banana shape and the liquid crystals scatter into random orientations, clogging the tunnel and blocking gas from penetrating. This switching takes about 5 sec, but faster times are possible, notes Marshall. Gas cutoff isn't total; the permeability change is about an order of magnitude, he adds.
"Controlling a membrane's permeability with light is preferable to controlling it with heat or electricity — two readily used alternative methods — for several reasons," Glowacki says. "For starters, light can operate remotely. Instead of attaching electrical lines to the membrane, a lamp or a laser can be directed at the membrane from a distance. This could allow engineers to make much smaller, simpler setups." In addition, heating and cooling take a relatively long time and repeated heating and cooling can damage the membrane.
Also, light does not have the potential to ignite a gas, which could be a crucial benefit when working with hydrocarbons or other flammable gases. Lastly, the amount of light energy needed to switch the membrane on and off is miniscule.
However, challenges remain. Currently, the membrane can't stand high pressures or temperatures because the liquid crystal (LC) material is only held in the pores by capillary action. The researchers currently are working on a new cross-linkable LC material that has the dye bonded to the polymer backbone. It promises to raise the pressure range and extend the temperature limit well above 100°C.
The next step in the development is to look at how the membrane performs with other gases, as only nitrogen has been used to date. "We also want to look at other liquid crystal phases (e.g., smectic phases) which are highly ordered and a bit more viscous than the nematic materials we now use, and thus may provide both larger permeability switching ratios and greater operating pressure differentials across membranes," notes Marshall.
"This technology has a very bright and important future, but it is still in its infancy," says Marshall. | <urn:uuid:4b9af12d-5774-4a3c-ba54-eb959942e81a> | 3.390625 | 687 | Knowledge Article | Science & Tech. | 34.731511 |
The lowest level one is called Xlib. This provides a simple way for a
client program to create a window, show it (map) onto the
screen, and put various graphical things (including text) in the
window. This is illustrated in #fnxlib#1672>.
[Inside the Xlib is all the stuff to implement these simple functions,
and to turn the parameters into messages that are sent (using the X
Protocol) to the right display server].
The next library is called the X Toolkit (it is made of two parts:-
the intrinsics and the Athena widgets libraries).
There are several other Toolkit Libraries - the main contenders
for standards (i.e. ones you will find on lots of makes of machine)
is MOTIF. Others are DECWidgets and HP
Widgets, which ressemble the basic Athena widgets we will look at
A C++ library which is very easy to use and very elegant is called
Interviews. This is not widely available or documented yet -
some of the staff have used it here.
Figure: Library and Protocol Layers Model of X
Nowadays, toolkits are emerging at ever higher levels. The latest fad
is for the one associated with the tool language, Tcl, called Tk. | <urn:uuid:bd34c376-7bba-40db-82de-993cc27e72a5> | 2.96875 | 275 | Documentation | Software Dev. | 55.327413 |
In our last series of tutorials we worked with Conditionals and Loops to create some basic Perl programs. This time around we are going to be working with files. Text files, CGI files, PL files, boiled files, fried files, Files Benedict, steamed Files. Okay, so I was kidding about the steamed Files.
Creating a file to read from in Perl is pretty simple. Simply open up a .txt file and enter the following data:
The Incredible Hulk|Super Strength|I rip my pants
Daredevil|Heightened Senses|I have poor fashion sense due to blindness
Apache Chief|the ability to grow Very Tall|I Wear a skirt
When you enter the data, note a few things. First, there are no headers here. Second, we separate each column of data with a pipe(|) symbol. And third, each line of data is separated by pressing the Enter key. Note that nothing should appear on the blank lines, not even a space. This is because when Perl reads it, it will read that line as a new row of data.
When you finish entering the data, save the file. You can leave it as a .txt file if you like. The only downside to this is that the data will be visible to any users who happen upon your page. If you want to limit visibility of the data, you can save it as a .cgi or .pl file, depending upon your host. For simplicity's sake, save the file (use the name super.txt) in the same directory as you are saving your script. If you don't, you will have to point to the directory where your file is being saved.
At this point we could set permissions, but I will save that for another time. Setting permissions allows you to choose whether the file can only be read, can be edited, neither, or both. | <urn:uuid:8057bf07-d2c4-4e99-ac39-ed0b6109fae9> | 3.3125 | 386 | Tutorial | Software Dev. | 66.292277 |
The Whales of Southern California project is new extension of our Whales of British Columbia project. Earthwatch scientists have achieved interesting results in British Columbia and are excited to be expanding their project.
The Whales of British Columbia:
From 1994 to 2008, a total of 126 grey whale individuals were identified in the waters near Cape Caution - approximately a third of which were seen regularly (i.e. during almost every field season). Grey whale distribution and abundance in Canadian waters was well-known and predictable each summer until 2004, when their status appeared to change with a quantifiable shift in foraging behavior. The Earthwatch scientists hypothesize that this was due to a decline in traditional prey resources, encouraging whales to become opportunistic and exploit new areas and food resources, rather than relying on the long-established feeding areas indentified in the initial years of the research. Historically, mysid prey were recorded in the research area in spatially and temporally stable swarms, which were large and extremely dense, with a mean abundance of 440,000 per m³. However, in 2005 and 2006, the mysid “crop” failed and the whales did not return to their usual grounds. In 2007, the mysids started to reappear and, by the end of the season, whales had returned. In 2008 the situation improved further, as the mysid population boomed again, Holmsimysis sculpta returned as the dominant mysid species and grey whale was resident again for extended periods.
Earthwatch research is providing essential data, and through the scientists’ network and links with the US National Marine Fisheries
Service and the Province of BC, the information is getting to the right places. The results are now being incorporated into international management plans drawn up by the Canadian and American governments for the grey whale in the northeast Pacific.
Related publications include:
Laskin, D.N., Duffus, D.A. & Bender, D.J. (2010) Mysteries of the not so deep: An investigation into gray whale habitat use along the west coast of Vancouver Island, British Columbia. In: Breman, J. (Ed.) Ocean Globe. ESRI Press Academic, Redlands, California, USA.
Nelson, T.A., Duffus, D.A., Robertson, C., Laberee, K., Feyrer, L.J. (2009) Spatial-temporal analysis of marine wildlife. Journal of Coastal Research (Special Issue), 56: 1537-1541.
Stelle, L.L., Megill, W.M. & Kinzel, M.R. (2008) Activity budgets and diving behavior of gray whales (Eschrichtius robustus) in feeding grounds off coastal
British Columbia. Marine Mammal Science, 24 (3): 462 - 478. | <urn:uuid:f9b8ea46-0dff-4643-9088-74ea09a3e90a> | 3.1875 | 582 | Knowledge Article | Science & Tech. | 52.693984 |
Now, the first thing the sceptics say is, "Statistical outlier!" Yes, there are warmer than usual and colder than usual winters. It's the trend line that counts. If the trend line was flat then this winter would be a statistical anomaly. However, the trend line points upwards so winters are getting warmer, year on year.
"But," the sceptics say, "there were ice fairs on the Thames in the middle ages and the Romans cultivated wine grapes all over England." That is meant to be proof that the climate changes and we should be grateful for the increased warmth. Climate does change, over long periods of time not in decades as we are seeing now.
"More warmth means less heating fuel used and longer growing seasons are good for our farmers," say the sceptics. Try saying that to our pensioners who die of heat exhaustion during the summer or to Australian farmers who haven't seen water for years and haven't grown anything this year.
Oceanic islands are disappearing under the sea and bio-diversity is in decline throughout the world all because of our impact on the climate. It is selfish to want global warming to heat your country just because you can no longer squeeze your obese backside into an airliner for your yearly visit to the Mediterranean.
A warmer winter in the temperate zone is an unbearable one in the tropical zone. "Tourists" from the tropics might be coming here for good if the planet heats up too much.
BBC - Winter 'second warmest on record' | <urn:uuid:9c6a21fc-ed29-456b-a1c2-a1b62a161514> | 2.921875 | 311 | Personal Blog | Science & Tech. | 57.401129 |
Save Casco Bay from an Oil Spill!
- To demonstrate what happens in an oil spill, fill a glass bottle two-thirds full of water. Add blue food coloring to make the "ocean."
- Pour 1/2-inch or more of cooking oil into the bottle. This is the "oil spill."
Where does the oil congregate? (It floats on the surface)
What happens to an object (a cork) that you drop into the bottle? (It becomes coated with oil)
- Put on the cap and shake the bottle vigorously (like storm or wave action). What happens to the oil? (Some of it mixes with the water)
- Ask what would happen to organisms that float on the surface (sea birds, ducks, seaweeds, planktonic animals) or that need to come to the surface to breathe (whales, seals, sea turtles). (They'd be coated with oil.)
- Explain that over time the water and oil mix somewhat and that some of the oil (which is heavier than this cooking oil) will sink to the bottom of the ocean.
What would happen to flounders, sea urchins, lobsters, crabs, and other bottom dwellers?
- Students have to try to clean up an oil spill before it pollutes the ocean, animals, and shoreline.
- To a large pan of water with a sandy shoreline (mound of sand at one end), add cooking oil to simulate a spill.
- Let each team of three to four students choose two or three different clean-up materials to test.
- Have students make a plan for how they will use each material, then test it.
- Discuss why their efforts worked or didn't work.
Was all the oil removed?
How well might their methods work on an actual spill?
Discuss what kinds of equipment actual oil spill clean-up personnel use (such as oil containment booms, skimmers, dispersants, oil absorbing materials, etc.) and how similar they are to items the students used.
- Make a diagram or list of the life in a marine environment near you. How would each organism be affected by an oil spill?
What animals are most vulnerable to an oil spill? (Those that can't move; filter feeders like oysters, barnacles, and clams; those that surface often; those that depend exclusively on marine life for their food supply.)
- What can we as consumers do to mitigate oil spills? (Drive less, lower thermostats, use alternative forms of energy, use fewer oil-based products, demand, and be willing to pay for, safer transport mechanisms like double-hulled tankers.)
Repeat this procedure but apply wave action by blowing "wind" across the surface of the water through a straw or with an electric fan. Discuss how the weather affects clean-up efforts.
Oil Spill Contingency Plans
Find out how your area is prepared to deal with oil spills. Find out what materials would be used and under what ocean conditions. Research what has been learned in the wake of the Exxon Valdez spill.
Birds and Oil
Examine a bird feather. Oiliness on the feather keeps the feathers from becoming waterlogged. Notice how it can fluff up after it's handled.
Drop the feather into a pan of clean water. Does it float? Shake it off.
Allow it to dry completely. Does it still fluff up?
Drop a bird feather into the pan of water and oil. What happens to it?
Try to clean it up. Some students may use liquid detergent; others may just scrub with a toothbrush.
Allow the feather to dry naturally, or dry it with a hair dryer. Does it still fluff up?
Drop it into a pan of water. Does it still float as well as it did before?
These tests indicate that the feather has lost its ability to insulate, and to resist water.
Sea Otters and Oil
Read Spill! the Story of the Exxon Valdez, Terry Carr, Franklin Watts, NY (1991) and Sea Otter Rescue, Roland Smith, Cobblehill Books, New York, (1990) which is the story of how sea otters were rescued, cleaned and returned to the wild after the Alaska Exxon Valdez oil spill in 1989.
Discuss the implications for marine mammals on our coast, especially harbor seals.
Find other resources about the Exxon Valdez spill and its consequences on the environment.
Tracking Oil Spills
After the Exxon Valdez oil spill, people realized the importance of tracking large oil spills, possibly by satellite imagery, to figure out where they were moving. Using imagery from the radar range of the electromagetic spectrum, scientists have developed a means for tracking the spill. Take a look at a sample image from NASA and a series of images from the Tromsø Satellite Station, Norway's national receiving station. Discuss with your students what measures they would use to track oil spills and why it is important.
- cooking oil mixed with black tempura paint
- one or more glasses or clear plastic pans of water tinted with blue food coloring
- wide-mouthed glass bottle with cap
- a cork or toy boat
Materials to use for cleanup
- cotton balls
- cut-up panty hose
- paper towels
- bandage pads
- drinking straws
- turkey basters or eye droppers
- popsicle sticks
- liquid dishwashing detergent diluted in spray bottle. | <urn:uuid:78ed640e-7049-41a4-98e3-1ecca33e0fb5> | 4.1875 | 1,149 | Tutorial | Science & Tech. | 63.133431 |
Return a string holding the external representation of the number n in the given radix. If n is inexact, a radix of 10 will be used.
Return a number of the maximally precise representation expressed by the given string. radix must be an exact integer, either 2, 8, 10, or 16. If supplied, radix is a default radix that may be overridden by an explicit radix prefix in string (e.g. "#o177"). If radix is not supplied, then the default radix is 10. If string is not a syntactically valid notation for a number, then
string->numberabove, but taking a C string, as pointer and length. The string characters should be in the current locale encoding (
localein the name refers only to that, there's no locale-dependent parsing). | <urn:uuid:634a0d41-a03d-49d2-8880-67748bb1b0e8> | 2.84375 | 175 | Documentation | Software Dev. | 63.234523 |
(pronounced Air-Dersh) was the most prolific mathematician of all time. He wrote almost 1500 papers with many others, leading to the creation of the Erdös number
, connecting mathematicians to each other by way of their co-authored papers. Even a horse
has an Erdös number of 3. He also had his own language
- if a person had "left", they had died, but if they had "died", they had stopped doing mathematics.
posted by Orange Goblin
on Nov 18, 2003 -
The colour of numbers -
For the math geeks out there (which I'm not - maybe his theories will be shot down in flames), Karl Palmen has discovered that numbers can be assigned one of eight "colours", related to their prime factors. He goes on to show the interesting mathematical properties of these colours. A novel way of playing with numbers. Software is on offer
posted by Jimbob
on Aug 11, 2003 -
is an environment that generates small, walking computational organisms. "Each walking thing is built up from totally random conditions. Appearance, behavior, and walking characteristics are all assigned from a range enabling effective, functional mobility. Click on a walking thing to permutate its characteristics".
Just one of the very many wonderful (open source
) creations at levitated.net
(more bugs with bling here
). Kick off your shoes, fill your coffee cup or wine glass, and dip in.
posted by taz
on Jul 2, 2003 -
'The Poincare Conjecture' Solved?
"Dr Grigori Perelman, of the Steklov Institute of Mathematics of the Russian Academy of Sciences, St Petersburg, claims to have proved the Poincare Conjecture, one of the most famous problems in mathematics. The Poincare Conjecture, an idea about three-dimensional objects, has haunted mathematicians for nearly a century. If it has been solved, the consequences will reverberate throughout geometry and physics."
Also of note is that Perelman's solution is only a benign side effect of his efforts toward defining all three-dimensional surfaces mathematically, which if successful would allow humanity to "produce a catalogue of all possible three-dimensional shapes in the Universe, meaning that [mankind] could ultimately describe the actual shape of the cosmos itself."
posted by eyebeam
on May 8, 2003 -
For Great Justice.
Man appeals to High Court of Australia to apply their jurisdiction to the laws of mathematics. Justice Kirby not amused.
posted by Bletch
on Apr 7, 2003 -
The man who wrote 10,000 Grooks
), Piet Hein, was also the inventor of Hex
and the creator of the Soma Cube
. In the design world, he is most famous for the SuperEllipse
, a figure that rivals Buckminster Fuller's geodesics in ingenuity, an aesthetic balance between a circle and a square, and a mathematical figure
which has been used to design a square in Stockholm.
From the SuperEllipse, you can get the SuperEgg, a strange solid which will unexpectedly balance on one end and has been mistaken for an alien artifact
posted by Winterfell
on Oct 28, 2002 -
has finished his book, "A New Kind of Science
," which purpotedly is being espoused as a paradigm shift in many fields. But, I'm starting to see a very reductionistic attitude in many of the main theorists of complextity theory and emergent phenomena. Is the idea that the Universe is in lines of code a phallus-extension/masculine overdriven idea? Isn't math a man made mapping and can the Universe be reduced to an equation by a man? Still this book is going to be groundbreaking. Read the following exceperpt from the wired.com
q: "I've got to ask you," I say. "How long do you envision this rule of the universe to be?"
w: "I'm guessing it's really very short."
q: "Like how long?"
w: "I don't know. In Mathematica, for example, perhaps three, four lines of code."
link via protofunk.org
, old similar thread
posted by nakedjon
on May 20, 2002 -
Can you stump the Encyclopedia of Integer Sequences?
Every identifiable sequence known to man, including:
Name: Busy Beaver problem: maximal number of steps that an n-state Turing machine can make on an initially blank tape before eventually halting.
Comment: The sequence grows faster than any computable function of n, and so is non-computable.
If your sequence does not appear there, you might want to try the Super Seeker
posted by vacapinta
on Apr 15, 2002 -
NDb -(60% x Nc/Nt +40% x Dc/Dt) x 17,585
"Mathematicians called in by the Metropolitan Police think they have worked out the best way to beat crime in the capital."
Are there any UK mathematician/cops out there that know what the variables actually are?
posted by badstone
on Jan 17, 2002 -
Laws of Form
In 1969, George Spencer-Brown published a mathematical book called Laws of Form
, which has inspired explorations in philosophy, cybernetics, art, spirituality, and computation. The work is powerful and has established a passionate following as well as harsh critics. This web site explores these people, their ideas and history, and provides references for further exploration. I read this then, didn't understand much of the math due to my innumeracy, but was struck by a passage in passing... I especially am curious to see what the numerate in MetaFilter have to say.
posted by y2karl
on Nov 11, 2001 -
What Color is My Hat?
I [heart] these mathematical conundrums -- simple, easy-to-state, seemingly obvious logic problems that have solutions that completely defy common sense. Here's another you can spring on a friend: "You want to fry up three pieces of french toast. You have a frying pan that is just large enough to accomodate two pieces of bread at a time. If it takes you 30 seconds to fry one side of bread, and each piece of must be fried on both sides, how long will it take you to cook up three pieces (assuming that the act of flipping a piece or adding/ removing it to or from the pan takes no time). Think about it. Answer inside.
posted by Shadowkeeper
on May 25, 2001 -
...harnessing the power of Lava Lite® lamps to generate truly random numbers....
That's a bold statement, but who am I to doubt the power of the lava lamp
. The mathematical purist may disagree with the "truely random" part, but this geek speak
convinced me that LavaRand can handle all my random number needs.
posted by bicyclingfool
on Apr 30, 2001 -
Mathematician Bums Out Entire Scientific Community
His "Omega" number--infinite and incalculable--guts hopes for pure mathematics, physicists' hopes for a Theory of Everything, and is just in general kind of bafflingly cool. Builds on the whole Godel/Turing foundation of hopelessness!
posted by Skot
on Mar 15, 2001 -
The passing of a giant.
Claude Shannon has died. He was a man of towering intellect, whose achievements are dwarfed only by the ignorance of the public to the value of those achievements. All our lives have been radically changed by him, but I bet not one person in a hundred has even heard of him.
posted by Steven Den Beste
on Mar 2, 2001 -
The Key Vanishes: Scientist Outlines Unbreakable Code [NEW YORK TIMES - free reg required] In essence, the researcher, Dr. Michael Rabin and his Ph.D. student Yan Zong Bing, have discovered a way to make a code based on a key that vanishes even as it is used. While they are not the first to have thought of such an idea, Dr. Rabin says that never before has anyone been able to make it both workable and to prove mathematically that the code cannot be broken.
Once this gets out, the debate on exporting strong crypto would seem to be essentially over.
posted by mikewas
on Feb 20, 2001 -
Americans suck at math. Mathematician trade deficit ensues...
I only find this article interesting because of a talk with my math teacher recently about how most math teachers these days are foriegners, although she isn't, and not that foriegners are bad. But I'm curious if this a bad problem in today's economy or not? Or if this is a problem? What country is good at math? India and China? That's where most of the Silicon Valley CEO's workers are from these days. Or is that political, financial? I don't know. Do you know?
posted by redleaf
on Feb 7, 2001 -
Another unified theory!
And this time it's not just about physics, but the eternity domain, diallel lines, sunspots, egg resonance, planetary alignment, plant dehydration and the Book of Mormon too.
posted by rodii
on Feb 4, 2001 -
Statistics is cool! (Amazing introduction to the concept of estimation, and error computing.)
posted by rschram
on Oct 24, 2000 -
Mersenne Prime Search
is a distributed computing project much like Seti@home
, except instead of searching for aliens, you're in the running for $100,000 and a place in math history (shouldn't your computer actually be the one that goes into the math history books?).
posted by mathowie
on Jul 7, 2000 -
The Poincaré Conjecture
: If we stretch a rubber band around the surface of an apple, then we can shrink it down to a point by moving it slowly, without tearing it and without allowing it to leave the surface. On the other hand, if we imagine that the same rubber band has somehow been stretched in the appropriate direction around a doughnut, then there is no way of shrinking it to a point without breaking either the rubber band or the doughnut. We say the the surface of the apple is ‘simply connected,’ but that the surface of the doughnut is not. Poincaré, almost a hundred years ago, knew that a two dimensional sphere is essentially characterized by this property of simple connectivity, and asked the corresponding question for the three dimensional sphere (the set of points in four dimensional space at unit distance from the origin). This question turned out be be extraordinarily difficult, and mathematicians have been struggling with it ever since.
...but if you can prove it, [or any of six other 'millenium prize problems
'] the clay mathematics institute
wants to line your pockets with $1M
posted by palegirl
on May 24, 2000 - | <urn:uuid:f32caedc-2e99-475d-abf1-2f863b79caf4> | 2.859375 | 2,327 | Comment Section | Science & Tech. | 54.954427 |
The following HTML text is provided to enhance online
readability. Many aspects of typography translate only awkwardly to HTML.
Please use the page image
as the authoritative form to ensure accuracy.
New Worlds, New Horizons in Astronomy and Astrophysics
eral dark energy projects including the Baryon Oscillations Spectroscopic Survey on the Apache Point Observatory 2.5-meter telescope, and a new Dark Energy Camera to be installed on the 4-meter Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile, small but pioneering efforts on CMB research, and R&D for upcoming projects. Many of these investments are collaborative with either NASA or NSF (NSF-AST and NSF-PHY). In addition, DOE supports a vibrant program of underground dark matter direct-detection experiments and related research and development as part of the cosmic frontier core area. DOE also continues to provide adaptive optics (AO) expertise for instruments on ground-based telescopes. High-energy-density facilities of its National Nuclear Security Administration and laboratory experiments growing out of the Fusion Energy Sciences program play an increasing role in laboratory astrophysics.
National Aeronautics and Space Administration
NASA successfully operates a fleet of nine space telescopes at present and collaborates on several foreign missions (Box 6.1). The annual operating astrophysics budget is roughly $1 billion. All major astrophysics projects are managed by NASA centers,3 whereas smaller Explorer-class spacecraft experiments can be led by university-based teams. What is striking about the past decade is that nearly all space astrophysics missions have surpassed expectations, both in the technical performance achieved and in the scientific discoveries made. This remarkable accomplishment is one in which the nation can take great pride. Two European space missions with significant U.S. participation, Herschel, a far-infrared telescope, and Planck, a cosmic microwave background experiment, have been launched recently and appear to be working very well. X-ray telescopes led by Japan (Suzaku) and Europe (XMM-Newton) are also producing exciting results and have significant U.S. participation and contributions.
The largest space telescope currently under construction is the James Webb Space Telescope (JWST; Figure 6.2). It was the top large space mission recommended as a result of the 2001 decadal survey4 and is a successor to both the Hubble Space Telescope and the Spitzer Space Telescope. It is scheduled for launch in 2014. The ambition (the cost exceeds $5 billion) and challenge (the mirror is 2.5 times the diameter of the Hubble mirror) represented by JWST have led to delay in the remaining space astrophysics program proposed in the 2001 decadal survey. JWST
Typically one of the following: Ames Research Center, Goddard Space Flight Center, or Jet Propulsion Laboratory. | <urn:uuid:2ed23b44-3e28-4540-93b8-07b9eb7d368b> | 2.953125 | 579 | Knowledge Article | Science & Tech. | 27.815536 |
For the more information about the geologic resources of the National Park Service, please visit http://www.nature.nps.gov/geology/.
BioBlitz: A Snapshot of Biodiversity
A bioblitz is part rapid biological survey and part a public outreach event that brings together scientists and volunteers to compile a snapshot of biodiversity in a relatively short amount of time.
Bioblitzes are an important part of the National Park Service A Call to Action: Preparing for a Second Century of Stewardship and Engagement. Biodiversity discovery events such as bioblitzes are the focus of Action 7: Next Generation Stewards, which calls for the National Park Service to "create a new generation of citizen scientists and future stewards of our parks by conducting fun, engaging, and educational Biodiversity Discovery activities in at least 100 national parks, including at least five urban parks."
The National Park Service and National Geographic Society are collaborating to host one bioblitz per year for the 10 years leading up to the National Park Service Centennial in 2016. These large-scale events have involved thousands of people of all ages and backgrounds who have worked together to discover hundreds of different species. Explore this website for details and watch the video below to see footage from the 2012 BioBlitz in Rocky Mountain National Park.
We warmly invite you to participate in the next National Park Service/National Geographic Society BioBlitz at Jean Lafitte National Historical Park and Preserve on May 17–18, 2013. Go on assignment in the bayou with other volunteers and subject matter experts to discover and learn about the living resources of one of the most unique ecosystems in the United States.
Last Updated: February 07, 2013 | <urn:uuid:3e508fb2-0eab-4f06-a2ad-32bbf7584c4b> | 3.359375 | 351 | Knowledge Article | Science & Tech. | 29.965238 |
Mon Jul 23 23:03:29 BST 2012 by Dirk Pons
I am surprised that the seismologists are surprised about this. Are their fracture models too simplistic? After all we see irregular fracture surfaces and time delays in other fracturing materials. You only have to look at how a piece of stale bread crumbles under load, to appreciate that cracks do not always follow straight lines. Nor does the whole crack have to appear at one time and propagate at the speed of sound. To see that, look at a complex failure like a slow motion car crash and note how the deformation of one sub-structure progressively (hence time delay) puts strain onto other sub-structures, which then fail in turn. The popular mental model of earthquakes being caused by simple linear motion along a smooth plane in a homogeneous material is not all it's cracked up to be
Thu Jul 26 21:25:50 BST 2012 by Eric Kvaalen
Well, if we're gonna make puns, I just did a little rusk analysis.
I took a "biscotte" and stressed it with shear until it broke. And you're right, it made a jagged break.
But that's because it has the freedom to separate. When the earth slips, there's rarely any separation formed (with exceptions such as in Numbers 26).
Also, the earth is different from a car. The car deforms drasticly, whereas the earth hardly deforms at all in an earthquake. It just undergoes very slight elastic deformation.
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support. | <urn:uuid:808f0008-97f5-4912-b0c1-8e8c665a8ef8> | 2.796875 | 369 | Comment Section | Science & Tech. | 60.809697 |
Many species of scarab beetles, in fact, have very specialized relationships with their environments. Adult male and female Phanaeus difformis dung beetles, for example, work as a team to locate animal dung, shape the dung into so-called brood balls, and dig tunnels where the balls can be stored. The female then lays an egg in each brood ball, which serves as a ready-to-eat food source for the larva when it hatches about a week later. If the dung ball dries out or does not contain sufficient nutrients, the larva will die. If conditions are just right, however, within a little over a month the larva has matured into an adult, eaten its way out of its brood ball, and gone in search of fresh dung and a mate, beginning the cycle again. Hence, the survival of dung beetles is dependent on fresh dung, which they will travel great distances to locate.Compared with P. difformis, larvae of the eastern hercules beetle (Dynastes tityus), a type of rhinoceros beetle with a notably menacing appearance, have a much longer generation time. This species, which is one of the largest beetle species found in the United States, also has a very different relationship with its environment. In the summer, females lay eggs in decaying wood on hardwood trees. The larvae that hatch from the eggs typically remain in the wood, feeding on decaying matter for more than a year and a half before becoming pupae. The pupa stage is spent inside a hollow cell that the larva constructs for itself by using saliva to glue together tiny pieces of wood and feces. Within about 6 to 8 weeks, the pupa emerges as an adult.
The entire life cycle of the eastern hercules beetle may last two to three years, and while larvae feed almost exclusively on decaying wood, adults may feed on sap and decaying leaves. Although eastern hercules beetles can damage trees by ovipositing (laying) eggs in the same sites year after year, the breakdown of dead wood by the larvae releases nutrients to be returned to the soil. Hence the larvae play an important ecological role in hardwood forests.
Other scarab beetles include Japanese beetles (Popillia japonica), June beetles (Phyllophaga), and flower chafers (subfamily Cetoniinae). Some of the world’s most massive insects, measuring up to 11 cm in length and weighing as many as 3.5 oz., are African goliath beetles (Goliathus), which belong to the flower chafer subfamily. Found in tropical and subtropical Africa, goliath beetles differ from most other scarab beetles in that they live buried in the soil as larvae and spend a much longer time—sometimes as many as five months—in the pupa stage. In addition, their life cycles are intimately associated with Africa’s wet and dry seasons. For example, pupation takes place at the end of the wet season, allowing the larva to cocoon itself below ground in a sandy cell that hardens with the onset of the dry season. By the time heavy rains return, the pupa has metamorphosed into an adult goliath beetle, which breaks free from its rain-softened cell and emerges from the soil.
Kara Rogers is the senior editor of biomedical sciences at Encyclopaedia Britannica, Inc. She is also a member of the National Association of Science Writers and a contributor to the Britannica Blog, where she runs a series called Science Up Front. She holds a Ph.D. in Pharmacology/Toxicology, but enjoys reading and writing about all things science. You can follow her on Twitter at @karaerogers.
This post also appears on the Britannica Blog. | <urn:uuid:c2fdc3a4-45f8-4339-9ff3-1cac08f0b7b9> | 4.1875 | 785 | Personal Blog | Science & Tech. | 47.998109 |
Why the Earth's air is really an ocean
Explore This Story
The next time you're in Carnegie Hall and the atmosphere seems stuffy, don't blame the upper crust in their box seats. Blame the building's air. It weighs almost 32,000 kilograms.
It's one of many little-known facts about the stuff we breathe that British science writer Gabrielle Walker packs into the engrossing, surprisingly light book, An Ocean of Air: Why the Wind Blows and Other Mysteries of the Atmosphere.
Though we take air pollution very seriously, we tend not to pay much attention to the air itself unless it's threatening us with harmful chemicals. Yet Walker's book tells the story of the inventive scientists who studied the air and came to fascinating conclusions.
"We live submerged at the bottom of an ocean of air," wrote Renaissance mathematician Evangelista Torricelli, whose experiments discovered atmospheric pressure.
Walker takes us on a buoyant tour of the brilliant, though often flawed minds that have probed a substance so difficult to study. The Sunday Star spoke to her about the weight of air, the good intentions behind CFCs, and the first man in space (it's not who you think it is).
In what way is the Earth's air an "ocean"?
It's because it's so big and heavy. It's so heavy that it's almost inconceivable that we walk around and brush it aside, but it's actually weighing down on us. Just like an ocean, it's also got currents that distribute warmth throughout the world, and it also has creatures moving through it. I had thought that we were living on the surface of a rocky planet. I had no idea I was living at the bottom of an ocean. I imagined shrimps and lobsters marching around on the sea floor who have no idea of the miraculous substance above their heads.
What made you write a book about the atmosphere?
Since working for Nature, I had to research the atmosphere and the oceans, and I found it really interesting. I found out this story about the amazing Capt. Joseph Kittinger. I discovered that this extraordinary man had actually fallen through the atmosphere.
He'd jumped out of a plane. And I found footage of him doing it. You can see what it was like when he jumped out, you can see him tumbling, and you see the balloon up overhead, and it's incredible. He could see the curvature of the Earth, and he could see that delicate, thin, blue curving line of the atmosphere. This is before the astronauts saw it. And as he was doing that, I was thinking, what would it feel like to be out in space, above the atmosphere and falling through it?
I mentioned Capt. Kittinger to several people, but no one believed the story.
It is incredible, and it is completely true. But what really struck me about his description was that he was only 20 miles (32 kilometres) up. He was above the part (of the air) that brings food and water and rain and oxygen to the air; it transforms the Earth. That's actually 99 per cent of the atmosphere. He didn't feel like he was in a vacuum, he didn't know the air was so thin there that he would have died if he hadn't had his pressure suit working. But he felt like there was something deadly, an incredibly hostile environment.
He said, in a quote that I have in the beginning of my book, "There's a hostile sky above me. Man will never conquer space. He may live in it, but he will never conquer it."
And as he fell through space he got more and more comfortable, and by the time he landed on the ground, even though he was in a desert, he felt like it was the Garden of Eden because it was so full of life and it was so nurturing. And the thing that made the difference between those two states was the air. Twenty miles of it.
The book mentions a lot of striking facts, such as the revelation that if levels of carbon dioxide in the atmosphere get high enough, there's a 1 per cent chance this planet could turn into another Venus. One per cent seems pretty high.
Venus is a very different planet, but it's (still) extraordinarily similar to the Earth. It would take a lot more than we have now for there to even be a chance. But we also know there's more carbon dioxide now than ever before in human history. We're changing the atmosphere beyond anything that we've ever experienced.
Why is Thomas Midgley, the American who invented such environmental hazards as leaded gasoline and Freon, a sympathetic figure?
The thing that amazed me about him is that I really did think, let's look at the person who invented Freon. And I had this notion that this must be a bad guy who didn't care about polluting the planet as long as he made a profit. I couldn't believe it when I found out who it actually was – someone who was really trying to help. He was brilliant. He was so unlucky, yet everybody liked him.
Midgley was feted in his lifetime and died without knowing the true nature of his inventions ...
At least that meant that he never lived to find out how much damage he'd done. He'd certainly be heartbroken by it. I have this image of him: He's showing how safe Freon is, showing that it isn't toxic by breathing it in himself, and showing it isn't flammable by exhaling it out on a flame (and putting it out). He wanted it to be safe, he really did. It was just one of those tragedies. It showed that when we put things into the atmosphere, we get it wrong more than we get it right.
- Updated Harper under pressure as senate scandal claims his chief of staff
- Rob Ford, gas plants, senators: trust takes a hit at all levels of government
- 7 triggers that may lead to a tax audit
- Harper's chief of staff resigns amid Senate expenses scandal
- Canadian to head 13 million-member International Council of Nurses
- Is this too much for Ford Nation?
- If you think northern reserves are about suicide and despair, this flight is for you
- Updated Struggling Brampton actor discovers he’s big in Serbia — really big | <urn:uuid:30186760-d5e7-44eb-b360-da8d9366af52> | 3.34375 | 1,313 | Truncated | Science & Tech. | 64.366232 |
|Although many people call all insects "bugs," entomologists use the name "bug" to refer only to insects in the order Hemiptera.|
True bugs have all the general characteristics of typical insects. They are divided into three regions: head, thorax and abdomen. The thorax bears legs and wings; the head bears eyes, antennae and mouthparts. However, a true bug (Order Hemiptera) is very different from a grasshopper (Order Orthoptera) which you already studied in Unit I.
Notice that in the true bug, the mouthparts are formed into a beak extending from the bottom side of the head. It is adapted for taking liquid food. The grasshopper has chewing mouthparts adapted for eating solid food. In the bug illustrated in this exercise, the pronotum is large and flat and not saddle-shaped like on the grasshopper. (In other orders of insects behind the pronotum is a triangular-shaped piece, called the scutellum.) On true bugs the scutellum is easy to see, but in the grasshopper it is hidden under the pronotum. The front wing of a typical true bug is different from that of other insect orders. The area of the front wing next to the body is thickened or leathery, and the end area of the wing is membranous. The front wing of a bug is also called a hemelytron (meaning half wing). When a bug is not flying, its front wings lie flat over its back, and the membranous parts overlap each other. The hind wings are hidden under the front wings.
Labeling the True Bug Exercise
Answers to Labeling the True Bug Exercise | <urn:uuid:6daa3086-12bc-410a-83ad-bc3ce8cb4570> | 3.96875 | 358 | Tutorial | Science & Tech. | 54.855682 |
A viewer asked "Todd, why does fog form so often on fall mornings?"
That's a great question! And remember, fog is actually just a cloud that forms close to the ground. The ingredients needed for it tend to come together during the long, cool nights of fall.
Autumn days can still get relatively warm, with plenty of invisible water vapor in the air. Clear, lengthening nights allow the air to become saturated as it cools to the dew point temperature.
Fog forms from the ground up, becoming thickets around dawn.
After sunrise, heating from the sun and the mixing of higher altitude winds down to the Earth's surface help to dissipate fog layers. | <urn:uuid:2d23f04b-0859-4c09-8c39-2410e25006d0> | 3.3125 | 142 | Q&A Forum | Science & Tech. | 66.447853 |
BACKGROUND: Researchers at the University of Arizona have found that the same mathematical formula used to describe the shape of stalactites that form in caves also describes the shape of icicles. This is surprising because the physical processes that form icicles are very different from those that form stalactites. Both have a unique underlying shape, resembling a kind of elongated carrot. This sheds light into the physics of how drips of icy water can swell into long, skinny spikes (icicles).
HOW THEY FORM: Stalactites are formations that hang from the ceilings of caves, formed when water erodes limestone and taking the calcium carbonate. As the water drips inside the cave and evaporates, it leaves behind the calcium, which forms a stalactite. The continued diffusion of carbon dioxide gas fuels the growth of a stalactite. In contrast, heat diffusion and a rising air column are keys to an icicle's growth. Icicles form when melting snow begins dripping down from a surface such as the edge of a roof. There must be a constant layer of water flowing over the icicle in order for it to grow. The growth is caused by the diffusion of heat away fro the icicle by a thin fluid layer of water, and the resulting updraft of air traveling over the surface. That updraft occurs because the icicle is generally warmer than its surrounding environment, and thus convective heating causes the surrounding air to rise. As the rising air removes heat from the liquid layer, some of the water freezes, and the icicle grows thicker and elongates.
PUT TO THE TEST: To compare the predicted shape to real icicles, the researchers compared pictures of actual icicles with their predicted shape. They found that it doesn't matter how big or small the actual icicles were, they could all fit the shape generated by the mathematical equation. The next step is to solve the problem of how ripples are formed on the surfaces of both stalactites and icicles.
ICE, ICE, BABY: Ice is the frozen form of liquid water. The same substance will behave differently at various temperatures and pressures. Water (H2O) is the most familiar example. It can be a solid (ice), a liquid (water), or a gas (steam), but it is still made up of molecules of H2O, so its chemical composition remains unchanged. At sea level, water freezes at 32 degrees Fahrenheit (0 degrees Celsius) and boils at 212 degrees Fahrenheit (100 degrees Celsius), but this behavior changes at different altitudes because the atmospheric pressure changes. In fact, get the pressure low enough and water will boil at room temperature. The critical temperature/pressure point at which H2O changes from one form to another is called a phase transition. | <urn:uuid:bd605d94-6c29-4c01-b58d-3a1e2d6ff6d8> | 4.4375 | 563 | Knowledge Article | Science & Tech. | 41.541147 |
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 20, 1996
Credit: EIT Consortium, SOHO project, ESA, NASA
Explanation: Above is an image of the relatively quiet Sun made on May 18 in light emitted by ionized Helium atoms in the Solar chromosphere. Helium was first discovered in the Sun in 1868, its name fittingly derived from from the Greek word Helios, meaning Sun. Credit for the discovery goes to astronomer Joseph Lockyer. Lockyer relied on a recently developed technique of spectroscopy, dissecting sunlight into a spectrum, and the idea that each element produces a characteristic spectral pattern of bright lines. He noticed a yellow line in a solar spectrum made during an eclipse which could not be accounted for by elements known on Earth. Almost 27 years later Helium was finally discovered on Earth when the spectrum of a Helium bearing mineral of Uranium provided an exact match to the previously detected element of the Sun. Helium is now known to be the second most abundant element (after Hydrogen) in the Universe.
Authors & editors:
NASA Technical Rep.: Sherri Calvo. Specific rights apply.
A service of: LHEA at NASA/ GSFC | <urn:uuid:e0baa22d-61a5-4a99-8bb6-30c02a73f890> | 3.734375 | 271 | Knowledge Article | Science & Tech. | 37.937821 |
In the constellation Ursa Major
Approximately 1,000 times the mass of the Sun
Diameter equal to the size of Mars
X-ray views from Chandra X-Ray Observatory show a flare-up from the possible black hole. The black hole is just to the right of the green cross, which marks the galaxy's center. It is much brighter in the second view than the first. [NASA/SAO/CXC]
This document was last modified: August 29, 2011. | <urn:uuid:692d8343-0e2f-4b1d-917d-60046fd19a50> | 2.75 | 103 | Knowledge Article | Science & Tech. | 72.073269 |
This is a short article that explains a lot about the field of geoengineering. It introduces the reader to a subject they likely haven’t heard of before, and explains some pressing issues surrounding this technology. Overall, the article conveys its ideas well with the help of good organization and strong transitions.
The topic heading used in this article aren’t very specific (“Lone Rangers”) but they do inform the reader where one point of discussion ends and another one begins. “Albedo Enhancers” is about the advantages and disadvantages to one geoengineering approach, “Lone Rangers” describes the harm that just one country could cause with a geoengineering venture, and “From Science Fiction to Facts” emphasizes the need for scientific and international consensus on geoengineering matters. Tying these sections together are strong transitions that serve to orient the reader. These transitions help speed up the pace, when it is easy get caught in technical details.
One particularly strong transition appears at the very end of “Albedo Enhancers”: the author writes about potential disadvantages and disasters caused by artificially raising albedo. He (or she) then mentions that the massive consequences of geoengineering projects mean that international responsibility is needed, before moving on to “Lone Rangers” and the risks of unilateralism. | <urn:uuid:2268229c-3322-4ae2-bd2b-f7153e6007c9> | 2.734375 | 277 | Nonfiction Writing | Science & Tech. | 24.345491 |
Spectroscopy and Unknowns
Sarah Madden, Matt Grandbois, Eric Nelson
October 31 and November 7 2000
Chem 120 H / Viste
The purpose of this lab was to identify an unknown using various methods of spectroscopy. The unknown could have contained any or all of these elements: carbon, oxygen, and chlorine. The number of carbon atoms in the unknown molecule ranged from one to six. The following methods of spectroscopy are various ways to obtain the spectrum of an unknown: FTIR (infrared), which relates to molecular vibrations; Raman, which relates to molecular vibrations; NMR (nuclear magnetic resonance); GC/MS (mass spectroscopy); and UV-vis (ultraviolet-visible). Other chemical characteristics that can help identify organic unknowns are the boiling point, refractive index, and the flame test.
The lab began with obtaining an unknown organic compound. The first test that was completed was the Beilsteinís flame test for the presence of chlorine. The next part of the labs involved observing different types of spectra through use of FTIR, Raman, NMR, GC/MS, and UV-vis. The refractive index and the boiling point of the unknown were also found. The results of these various tests along with the different spectra types were then analyzed and the unknown was identified.
Beilsteinís Test: no chlorine
Boiling Point: 139-141 o C
Refractive Index: 1.4504
Additional Raman Spectra
NMR (nuclear magnetic resonance):
GC/MS (mass spectroscopy):
Cyclohexanone vibration 27:
Vibration Spectrum 35:
Microscopic picture of the atoms.
In this lab various methods of spectroscopy were used to identify an unknown. Based on observations and analysis of the spectras the unknown of this lab was identified as Cyclohexanone. | <urn:uuid:64b98257-44f1-4422-8b4d-37426dd06dc7> | 3.328125 | 393 | Academic Writing | Science & Tech. | 38.74 |
||It has been suggested that this article be merged into Symbol (chemical element). (Discuss) Proposed since February 2013.|
Only the first letter is capitalised. For example, "He" is the symbol for helium (English name, not known in ancient Roman times), "Pb" for lead (plumbum in Latin), "W" for tungsten (wolfram in German, not known in Roman times). Temporary symbols assigned to newly or not-yet synthesized elements use 3-letter symbols based on their atomic numbers. For example, "Uno" was the temporary symbol for Hassium which had the temporary name of Unniloctium.
Chemical symbols may be modified by the use of prepended superscripts or subscripts to specify a particular isotope of an atom. Additionally, appended superscripts may be used to indicate the ionization or oxidation state of an element.
Attached subscripts or superscripts specifying a nucleotide or molecule have the following meanings and positions:
- The nucleon number (mass number) is shown in the left superscript position (e.g., 14N)
- The proton number (atomic number) may be indicated in the left subscript position (e.g., 64Gd)
- If necessary, a state of ionization or an excited state may be indicated in the right superscript position (e.g., state of ionization Ca2+). In astronomy, non-ionised atomic hydrogen is often known as "HI", and ionised hydrogen as "HII".
- The number of atoms of an element in a molecule or chemical compound is shown in the right subscript position (e.g., N2 or Fe2O3)
- A radical is indicated by a dot on the right side (e.g., Cl· for a chloride radical) | <urn:uuid:28e2d019-95f3-45e7-9d45-8e25fd15330c> | 3.828125 | 385 | Knowledge Article | Science & Tech. | 44.543826 |
Can you construct an equilateral triangle? Assume each line has length 2.
Then bi-sect one of the angles (or lines)?
I.e. bi-sect the equilateral triangle?
Which of the lines can now be AD, because it has length root 3?
And then which end of it is best as A, in order to find B?
Actually... that requires a straight edge.
Ok then, with your compass mark a unit length from one end, A, then one further from the mark.
From the two marks, a point having distance of unit length from both.
How far is the new (third) mark from A? (Think, angles at a diameter.)
Mark a point, D, that same distance from A.
Yes, much simpler.
Compass point at A opened out to B, obtain a point C (on BA extended), so that CA=AB=1, CB=2 units.
Compass point at C opened out to B, draw a semi-circle.
Keep the same radius and draw a semi-circle centre B intersecting the last semi-circle (the one with centre C), at D'.
D' will be at a distance root 3 from A, so simply scribe the distance AD' onto the line AB to obtain the point D.
The proof of the result can be seen either from Pythagoras in the triangle CAD' or by making use of the intersecting chords theorem. | <urn:uuid:97de33d6-2470-4730-b1b2-c6c4780b4b19> | 3.59375 | 307 | Q&A Forum | Science & Tech. | 86.199577 |
The term 'slug' refers to a body type and not a group of closely related animals. The slug form has evolved several times in both land and marine molluscs.
A Leopard Slug, Limax maximus
Photographer: Alan Henderson / Source: Museum Victoria
Land snails and slugs belong to the Phylum Mollusca, the second-largest Phylum in the animal kingdom. They are all gastropods, and the slugs are all included in the order Pulmonata. In slugs, the shell that is so typical of most molluscs is lost or reduced to a small remnant buried in the soft tissue. The long, soft body of the slug is unsegmented and has tentacles on the head. It is capable of occupying very small spaces.
Distribution and habitat
Approximately 11 species of land slugs are found in Victoria. Most are introduced from Europe, however two native species, Cystopelta purpurea and Cystopelta astra, occur in forest & woodland areas of Victoria.
Slugs are generally found in cool, damp situations, with the introduced species preferring man modified areas, such as cultivated gardens and areas planted with crops and pasture. Because they have no shell, slugs are very susceptible to desiccation.
Most slugs feed on living plants, but some also eat decaying vegetable matter, and some will eat almost anything, including dog faeces and dog food. Some are regarded as serious pest in gardens, crops and pasture. Slugs are hermaphrodites and many species have complex courtship behaviour.
Barker, G. M. 1999. Naturalised Terrestrial Stylommatophora (Mollusca: Gastropoda). Fauna of New Zealand, volume 38. Whenua Press, New Zealand.
Beesley, P. L. et al. (eds) 1998. Mollusca, the Southern Synthesis. Fauna of Australia, volume 5. CSIRO Publishing, East Melbourne.
Runham, N. W. and Hunter, P. J. 1970. Terrestrial Slugs. Hutchinson University Library, London.
Smith, B. J. 1979. Field Guide to the Non-marine Molluscs of South-eastern Australia. ANU Press, Canberra.
Smith, B. J. 1992. Non-Marine Mollusca. In Houston, W. W. K. (ed.) Zoological Catalogue of Australia. Canberra: AGPS Vol. 8. | <urn:uuid:fbd280c2-8873-4e4e-b6f7-40771d283a54> | 3.65625 | 523 | Knowledge Article | Science & Tech. | 55.479649 |
Sun Screen Strength
A student in the science fair tried sun screen on light
sensitive plastic beads... they all turned color, indicating the screen
didn't work. Is this a valid test of the strngth of sun screen? Ideas?
What would be the effect if no-sun screen was used.
Would the beads change color to a larger extent?
What would happen with the beads using lower/higher SBF sunscreens.?
What is sun screen trying to filter out? All light, or just (invisible)
ultraviolet? What do the beads detect? Only ultraviolet, or visible light?
I think you can answer these questions, and from that answer your original
Richard Barrans Jr., Ph.D.
I assume that the beads were subjected to sunlight and they changed color.
These are some possible explanations for the stated observations.
The beads could be visible light sensitive and change color when exposed to
visible light. In that case, the observation does not prove anything.
The beads could be sensitive to both UV and visible light, in which case,
the sun screen could stop the UV and pass the visible. The beads would turn
color as a result of the exposure to visible light. No conclusion can be
made about sunscreen effectiveness.
If the beads are sensitive only to UV radiation, then we need to ask how
sensitive they are. Will they still show a change in color when exposed
to the fraction of the UV radiation that passes through the sunscreen?
If the beads are very sensitive, then even low levels of UV radiation could
saturate them (i.e., complete the color change). Sunscreens, even the
ones with high SPF (sun protection factor) of 30 or more, pass some UV
radiation and this may be sufficient to show a full color change to the
human eye (which is not a good light meter) .
Dr. Ali Khounsary
Advanced Photon Source
Argonne National Laboratory
Sun screen only attenuates light in certain wavelength regions. If the
light-sensitive beads respond to a wavelength range the sun screen is
not intended to block, then the test results don't say anything about the
effectiveness of the sun screen.
Click here to return to the Physics Archives
Update: June 2012 | <urn:uuid:c495d7b5-f95f-4170-be11-4876ac2234ab> | 3.109375 | 478 | Q&A Forum | Science & Tech. | 65.490333 |
- Original Caption Released with Image:
This three-frequency space radar image shows the city of Samara, Russia in pink and light green right of center. Samara is at the junction of the Volga and Samara Rivers approximately 800 kilometers (500 miles) southeast of Moscow. The wide river in the center of the image is the Volga. Samara, formerly Kuybyshev, is a busy industrial city known for its chemical, mechanical and petroleum industries. Northwest of the Volga (upper left corner of the image) are deciduous forests of the Samarskaya Luka National Park. Complex patterns in the floodplain of the Volga are caused by "cut-off" lakes and channels from former courses of the meandering river. The three radar frequencies allow scientists to distinguish different types of agricultural fields in the lower right side of the image. For example, fields which appear light blue are short grass or cleared fields. Purple and green fields contain taller plants or rough plowed soil. Scientists hope to use radar data such as these to understand the environmental consequences of industrial, agricultural and natural preserve areas coexisting in close proximity.
This image is 50 kilometers by 26 kilometers (31 by 16 miles) and is centered at 53.2 degrees north latitude, 50.1 degrees east longitude. North is toward the top of the image. The colors are assigned to different radar frequencies and polarizations as follows: red is L-band, horizontally transmitted and received; green is C-band, horizontally transmitted and vertically received; and blue is X-band, vertically transmitted and received.
The image was acquired by the Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) on October 1, 1994 onboard the space shuttle Endeavour. SIR-C/X-SAR, a joint mission of the German, Italian and the United States space agencies, is part of NASA's Mission to Planet Earth.
- Image Credit:
Image Addition Date: | <urn:uuid:60eafc07-e022-4a0b-9fdb-4fbde07c24c3> | 3.375 | 416 | Knowledge Article | Science & Tech. | 40.850504 |
Square symmetric matrices (or rather complex Hermitian ones) represent the observables of a quantum mechanical system. Their eigenvalues represent the possible observed values in ideal experiments. There is a basis of orthonormal eigenvalues, which allows you to write any state vector as a linear combination (superposition) of basis vectors. Squared absolute values of inner products define probabilities. Then one needs functions of matrices, in particular the matrix exponential, which gives the dynamics of a system, and an explicit solution of the Schroedinger equation in the case of an n-level system.
Thus you need to learn enough to be able to have a good grasp on these concepts:
matrix, transpose, conjugate transpose, linear combination, basis, eigenvalue, eigenvector, inner product, matrix power series, matrix exponential. Wikipedia has good summarizing articles on each of these topics, to help you give an overview. You can skip other stuff, and get back to it in case you need it.
In analysis you need systems of linear differential equations with constant coefficients (these are related to the matrix exponential), and the Fourier transform. The latter involves integration in 3 dimensions, but again, you can skip a lot and turn back to things skipped once you need them.
Then you can look into various quantum mechanical texts or lecture notes,
for example my online book http://lanl.arxiv.org/abs/0810.1019 - the first chapter of it should be understandable even with little prior knowledge, if you can tentatively accept concepts without a full understanding. My FAQ http://www.mat.univie.ac.at/~neum/physfaq/physics-faq.html might also be of help. By reading these and noting where you lose track you can find out what other concepts you need to make sense of your reading. This will tell you what else you need to learn. Ultimately, almost all of linear algebra and analysis is useful in quantum mechanics, but what and when depends on what you are interested in. | <urn:uuid:aa53f9b8-f683-487c-afa4-9b1e368ad5fd> | 3.109375 | 431 | Q&A Forum | Science & Tech. | 45.418763 |
Aligning F-ATPase alpha and beta subunits
Change color chainD to grey/blue (rightclick in control panel on D in first column to select chain D, right click on COL, select color)
Scrol down the control panel and select all ATP analogs (press ctrl key and right click to select)
right click on COL in heading and select red color
Read the pdb file to get info on which chain is which
select chain F (including nuc) and save selected residues as betaTP.
select chain A (including nuc) and save selected residues as alphaE.
After playing with the F1-ATPase, close this file and open betaTP and alphaE.
Display layer info
select and display only the nucleotides
There are different ways to align 3-D structures. One way is to select 3 corresponding points in each of the two structures. To do so you can use the substrate molecule.
Using the mov check off in the Layer Info, reorient the two ANPs so that they are in a similar orientation (but not overlapping).
Click on the align bottom with the 3 green and 3 red dots. Notice the red instructions that appear in the header next to the pdb-page icon. Follow these instruction using three corresponding atoms.
SHIFT DISPLAY CA chain (Shift makes the commands act on both layers)
Using the mov checks in the Layer info, move the two chains next to each other.
What do you think about the result?
Another way to align structures is to use the magic fit in the tools command. Do this and run improve fit (notice the red info in the header)
Click on alpha in Layer info to make the alpha subunit the active layer
Make the beta subunit the active layer
COLOR rms . The further the atoms in the beta subunit are away from the alpha subunit, the longer wavelengths it is the colored.
DISPLAY Show alignment window - gives you the aligned sequences.
How does this alignment compare to the ones calculated using Clustalw?
If you have time, repeat the exercise for the three beta subunits to observe the structural changes the beta subunit is undergoing in the catalytic cycle.
If you have more time to spare and you are up for a challenge, take a look at the nucleosome. Right click here and save as pdb file. Open it from within spdbv. You might want to do some of the future exercises with the nucleosome in addition to the ATPases – thus save the pdb file, where you can find it again.
Align all the histones form the nucleosome to one reference histone and color in rmv:
The result might look something like this:
The picture shows a structure alignment of the 8 histones (2 each) that are part of the nucleosome. All the histones were colored regarding the match to H2A, except H2A, which was colored according to its match to H3. Coloring option RMS – shorter wavelengths – better match
Below same as last figure, but histones are depicted side by side
Below are two views of the complete nucleosome. Histones H2A are depicted as spacefilling balls and RMS colored regarding their match to H3. The rest of the molecule is colored according to chain. | <urn:uuid:95754a52-1dcf-42fb-8876-d317170d513a> | 3.109375 | 703 | Tutorial | Science & Tech. | 54.418952 |
C++ virtual function is a member function of a class, whose functionality can be over-ridden in its derived classes. The whole function body can be replaced with a new set of implementation in the derived class. The concept of c++ virtual functions is different from C++ Function overloading.
C++ Virtual Function - Properties:
C++ virtual function is,
- A member function of a class
- Declared with virtual keyword
- Usually has a different functionality in the derived class
- A function call is resolved at run-time
The difference between a non-virtual c++ member function and a virtual member function is, the non-virtual member functions are resolved at compile time. This mechanism is called static binding. Where as the c++ virtual member functions are resolved during run-time. This mechanism is known as dynamic binding.
C++ Virtual Function - Reasons:
The most prominent reason why a C++ virtual function will be used is to have a different functionality in the derived class.
For example a Create function in a class Window may have to create a window with white background. But a class called CommandButton derived or inherited from Window, may have to use a gray background and write a caption on the center. The Create function for CommandButton now should have a functionality different from the one at the class called Window.
C++ Virtual function - Example:
This article assumes a base class named Window with a virtual member function named Create. The derived class name will be CommandButton, with our over ridden function Create.
class Window // Base class for C++ virtual function example
virtual void Create() // virtual function for C++ virtual function example
cout <<"Base class Window"< }
class CommandButton : public Window
cout<<"Derived class Command Button - Overridden C++ virtual function"< }
Window *x, *y;
x = new Window();
y = new CommandButton();
The output of the above program will be,
Base class Window
Derived class Command Button
If the function had not been declared virtual, then the base class function would have been called all the times. Because, the function address would have been statically bound during compile time. But now, as the function is declared virtual it is a candidate for run-time linking and the derived class function is being invoked.
C++ Virtual function - Call Mechanism:
Whenever a program has a C++ virtual function declared, a v-table is constructed for the class. The v-table consists of addresses to the virtual functions for classes and pointers to the functions from each of the objects of the derived class. Whenever there is a function call made to the c++ virtual function, the v-table is used to resolve to the function address. This is how the Dynamic binding happens during a virtual function call. | <urn:uuid:fb4da04f-50d3-4c02-99a0-8d78f0600678> | 4.375 | 582 | Documentation | Software Dev. | 45.391575 |
Plunge into the Papuan Bird’s Head Seascape in eastern Indonesia and you’ll be stunned at what lies beneath. Across the seascape live 1,300 types of reef fishes and nearly 600 species of hard corals – not to mention whales, crocodiles, and the crowd favorite: a walking shark.
Dive headfirst off the west coast of Central and South America and you’ll discover the Eastern Tropical Pacific Seascape. Here, GPS and satellite technology allow us to keep a close eye on the turtles, sharks, and other marine life spanning Costa Rica, Panama, Colombia, and Ecuador. There are plenty of reasons you should keep a watchful eye on this Seascape too.
The Sulu and Sulawesi Seas encompass nearly 900,000 square kilometers in Southeast Asia. The coasts of Indonesia, Malaysia, and the Philippines are home to threatened species including hawksbill, olive Ridley, and green turtles, as well as giant groupers and giant clams.
Over the last decade, CI’s Marine Program in Brazil has focused on the design and implementation of a network of multiple-use and no-take marine protected areas (MPAs) in the Abrolhos Region, the richest South Atlantic marine realm. | <urn:uuid:6a7bff1e-ad53-44a9-97b9-60a0731981ff> | 2.71875 | 262 | Knowledge Article | Science & Tech. | 40.763669 |
Threads and processes are the basic units of execution in concurrent Java programming. Every process has at least one thread, and all of the threads in a process share its resources. Understand the benefits of threads and why it's essential to use them safely.
Learn how to use the thread-safe, well-tested, high-performance concurrent building blocks in the java.util.concurrent package, introduced in Java SE 5. And find out how to avoid both common and lesser-known concurrency pitfalls.
In response to advances in multicore processor hardware, approaches to writing concurrent applications for the Java platform are diversifying. Concurrency support in two alternate languages for the JVM — Scala and Clojure — eschew the thread model. Learn about the actor and agent concurrency in those languages, and about third-party Java and Groovy libraries that implement those models. And learn more about fork-join, a multicore-friendly concurrency enhancement in Java SE 7.
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The atomic number indicates the number of protons within the core of an atom. The atomic number is an important concept of chemistry and quantum mechanics. An element and its place within the periodic table are derived from this concept.
When an atom is generally electrically neutral, the atomic number will equal the number of electrons in the atom, which can be found around the core. These electrons mainly determine the chemical behaviour of an atom. Atoms that carry electric charges are called ions. Ions either have a number of electrons larger (negatively charged) or smaller (positively charged) than the atomic number.
The name indicates the mass of an atom, expressed in atomic mass units (amu). Most of the mass of an atom is concentrated in the protons and neutrons contained in the nucleus. Each proton or neutron weighs about 1 amu, and thus the atomic mass in always very close to the mass (or nucleon) number, which indicates the number of particles within the core of an atom; this means the protons and neutrons. Each isotope of a chemical element can vary in mass. The atomic mass of an isotope indicates the number of neutrons that are present within the core of the atoms. The total atomic mass of an element is an equivalent of the mass units of its isotopes. The relative occurrence of the isotopes in nature is an important factor in the determination of the overall atomic mass of an element. In reference to a certain chemical element, the atomic mass as shown in the periodic table is the average atomic mass of all the chemical element's stable isotopes. The average is weighted by the relative natural abundances of the element's isotopes.
Electronegativity according to Pauling
Electro negativity measures the inclination of an atom to pull the electronic cloud in its direction during chemical bonding with another atom.
Pauling's scale is a widely used method to order chemical elements according to their electro negativity. Nobel prize winner Linus Pauling developed this scale in 1932.
The values of electro negativity are not calculated, based on mathematical formula or a measurement. It is more like a pragmatic range.
Pauling gave the element with the highest possible electro negativity, fluorine, a value of 4,0. Francium, the element with the lowest possible electro negativity, was given a value of 0,7. All of the remaining elements are given a value of somewhere between these two extremes.
The density of an element indicates the number of units of mass of the element that are present in a certain volume of a medium. Traditionally, density is expressed through the Greek letter ro (written as r).Within the SI system of units density is expressed in kilograms per cubic meter (kg/m3). The density of an element is usually expressed graphically with temperatures and air pressures, because these two properties influence density.
The melting point of an element or compound means the temperatures at which the solid form of the element or compound is at equilibrium with the liquid form. We usually presume the air pressure to be 1 atmosphere.
For example: the melting point of water is 0 oC, or 273 K.
The boiling point of an element or compound means the temperature at which the liquid form of an element or compound is at equilibrium with the gaseous form. We usually presume the air pressure to be 1 atmosphere.
For example: the boiling point of water is 100 oC, or 373 K.
At the boiling point the vapour pressure of an element or compound is 1 atmosphere.
Even when two atoms that are near one another will not bind, they will still attract one another. This phenomenon is known as the Vanderwaals interaction.
The Vanderwaals forces cause a force between the two atoms. This force becomes stronger, as the atoms come closer together. However, when the two atoms draw too near each other a rejecting force will take action, as a consequence of the exceeding rejection between the negatively charged electrons of both atoms. As a result, a certain distance will develop between the two atoms, which is commonly known as the Vanderwaals radius.
Through comparison of Vanderwaals radiuses of several different pairs of atoms, we have developed a system of Vanderwaals radiuses, through which we can predict the Vanderwaals radius between two atoms, through addition.
Ionic radius is the radius that an ion has in an ionic crystal, where the ions are packed together to a point where their outermost electronic orbitals are in contact with each other. An orbital is the area around an atom where, according to orbital theory, the probability of finding an electron is the greatest.
The atomic number does not determine the number of neutrons in an atomic core. As a result, the number of neutrons within an atom can vary. Then atoms that have the same atomic number may differ in atomic mass. Atoms of the same element that differ in atomic mass are called isotopes.
Mainly with the heavier atoms that have a higher atomic number, the number of neutrons within the core may exceed the number of protons.
Isotopes of the same element are often found in nature alternately or in mixtures.
An example: chlorine has an atomic number of 17, which basically means that all chlorine atoms contain 17 protons within their core. There are two isotopes. Three-quarters of the chlorine atoms found in nature contain 18 neutrons and one quarter contains 20 neutrons. The mass numbers of these isotopes are 17 + 18 = 35 and 17 + 20 = 37. The isotopes are written as follows: 35Cl and 37Cl.
When isotopes are noted this way the number of protons and neutrons does not have to be mentioned separately, because the symbol of chlorine within the periodic chart (Cl) is set on the seventeenth place. This already indicates the number of protons, so that one can always calculate the number of neutrons easily by means of the mass number.
A great number of isotopes is not stable. They will fall apart during radioactive decay processes. Isotopes that are radioactive are called radioisotopes.
The electronic configuration of an atom is a description of the arrangement of electrons in circles around the core. These circles are not exactly round; they contain a wave-like pattern. For each circle the probability of an electron to be present on a certain location is described by a mathematic formula. Each one of the circles has a certain level of energy, compared to the core. Commonly the energy levels of electrons are higher when they are further away from the core, but because of their charges, electrons can also influence each another's energy levels. Usually the middle circles are filled up first, but there may be exceptions due to rejections.
The circles are divided up in shells and sub shells, which can be numbered by means of quantities.
Energy of first ionisation
The ionisation energy means the energy that is required to make a free atom or molecule lose an electron in a vacuum. In other words; the energy of ionisation is a measure for the strength of electron bonds to molecules. This concerns only the electrons in the outer circle.
Energy of second ionisation
Besides the energy of the first ionisation, which indicates how difficult it is to remove the first electron from an atom, there is also an energy measure for second ionisation. This energy of second ionisation indicates the degree of difficulty to remove the second atom.
As such, there is also the energy of a third ionisation, and sometimes even the energy of a fourth or fifth ionisation.
The standard potential means the potential of a redox reaction, when it is at equilibrium, in relation to zero. When the standard potential exceeds zero, we are dealing with an oxidation reaction. When the standard potential is below zero, we are dealing with a reduction reaction. The standard potential of electrons is expressed in volt (V), by the symbol V0.
Back to the periodic chart or to Chemistry subjects | <urn:uuid:944ebe69-f8d3-434d-b7d9-e1036321ce6c> | 3.96875 | 1,633 | Knowledge Article | Science & Tech. | 39.097799 |
Bonds between atoms shape the molecules of the atmosphere, the ocean, and and everything between them. Covalent bonding is one of the mechanisms that holds atoms together in compounds. Water is held together by covalent bonds as are carbon dioxide and ammonia.
What is chemical bonding?
Chemical bonding joins atoms into molecules. Stable compounds form when a molecule has a lower energy state than the separate atoms had, that is, when it takes less energy for the atoms to stay together than to exist independently.
The two extreme types of bonds are the ion bond, in which one atom takes electrons from another, and the covalent bond, in which atoms share electrons. Intermediate types of bonds exist as well.
What is covalent bonding?
In covalent bonding, atoms share electrons. Electrons exist in shells around an atomic nucleus, the way the layers of an onion surround its center. Each shell has a certain natural number of electrons it tends to hold. If it has too many electrons, it wants to remove the excess. If it has too few, it wants more. Atoms form molecules by trying to obtain the right number of electrons in their shells. The noble gases seldom form molecules because their outer shells already have the exact number of electrons they need. In covalent bonds, separate atoms share electrons in a way that tends to complete their shells.
What is the difference between covalent bonding and ionic bonding?
In ion bonds, one atom takes electrons from another. The atom that had too many electrons is whittled down to a complete outer shell and the atom with an incomplete outer shell adds the electrons it needs.
The molecule holds together because the atom that took electrons now has a negative charge (because electrons are negative) and the atom that gave up electrons now has a positive charge (also because electrons are negative). The positive and negative ions (atoms with a charge) attract each other the way opposite poles of two magnets attract.
In covalent bonds, atoms do not give or take electrons. Instead, they share pairs of them. Atoms needing more electrons to fill their shells count the shared elections as part of their shell. In this way, all shells are filled. These molecules are held together by the way each nucleus is attracted to the electrons in its outer shell. Since the nuclei in effect share an outer shell, each is attracted to the outer shell of the other.
What is electronegativity?
Electronegativity is the tendency of an atom to attract bonding electrons. Electronegativity generally increases from left to right and from bottom to top in the periodic table. Metals are the least electronegative elements.
Elements with high electronegativity are very reactive, because they easily form bonds by taking electrons. Oxygen and fluorine are the two elements with the highest electronegativity and are very reactive.
Elements with very low electronegativity are also very reactive, because they give up their electrons easily. Caesium is the stable element with the lowest electronegativity, and it can explode on contact with water.
Chemical bonds are an important topic in chemistry since they are crucial to compounds, and compounds are an essential part of all life. | <urn:uuid:13427914-8e1a-4cfc-b4c2-dbb2b5e6208c> | 4.15625 | 669 | Knowledge Article | Science & Tech. | 39.520831 |
write-byte byte stream => byte
Arguments and Values:
byte---an integer of the stream element type of stream.
stream---a binary output stream.
write-byte writes one byte, byte, to stream.
(with-open-file (s "temp-bytes" :direction :output :element-type 'unsigned-byte) (write-byte 101 s)) => 101
stream is modified.
The element type of the stream.
Should signal an error of type type-error if stream is not a stream. Should signal an error of type error if stream is not a binary output stream.
Might signal an error of type type-error if byte is not an integer of the stream element type of stream.
read-byte, write-char, write-sequence | <urn:uuid:063abd93-d100-4e35-84d7-0f9736f2b77e> | 2.953125 | 166 | Documentation | Software Dev. | 59.234408 |
Maintained by FAO-FI
|What is Rio+20 ?|
|Rio+20 Conference brought together world leaders, along with thousands of participants from governments, the private sector, NGOs and other groups to shape how we can reduce poverty, advance social equity and ensure environmental protection. It was hosted by the Government of Brazil and run from 20-22 June 2012 complemented by a range of events before, during and after.|
The Conference focused on two themes: (a) a green economy in the context of sustainable development poverty eradication; and (b) the institutional framework for sustainable development.
|Photo title: Official logo of the Rio+20 Conference|
|Oceans at Rio+20|
|Issues related to oceans and oceans sustainability figured high on the Rio+20 agenda - it was chosen as one of the seven main issues to be discussed in depth. In the Rio+20 Conference Outcome Document The Future We Want, there is a dedicated section on oceans and seas, and small island developing States (SIDS), which stressed the critical role the oceans play in all three pillars of sustainable development, and commit[ed] to protect, and restore, the health, productivity and resilience of oceans and marine ecosystems, and to maintain their biodiversity, enabling their conservation and sustainable use for present and future generations.|
For ocean related events, hosted by UNESCO-IOC, see Events below.
The world's oceans - their temperature, chemistry, currents and life - drive global systems that make the Earth habitable for humankind. Our rainwater, drinking water, weather, climate, coastlines, much of our food, and even the oxygen in the air we breathe, are all ultimately provided and regulated by the sea. Throughout history, oceans and seas have been vital conduits for trade and transportation. Careful management of this essential global resource is a key feature of a sustainable future.
printed on 2013/05/22 23:52:03 | <urn:uuid:c124b584-f6dd-48bf-90da-f6f99e083525> | 2.6875 | 403 | Knowledge Article | Science & Tech. | 26.264251 |
Summary: Hash Tables Page 1
· All elements have a unique key.
o Insert element with a specified key.
o Search for element by key.
o Delete element by key.
· Random vs. sequential access.
· If we have duplicate keys, need rule to resolve ambiguity.
· What ways could you use to implement a dictionary? (Name in class)
o Ordered array
o Unordered array
o Ordered linked list
o Binary search tree
· Let's use our newly acquired analysis skills to determine which of the following is better.
Let's analyze them for two operations insert and search. This is shown in Table 1.
Method Insert time Search Time
Ordered array 2/n nlog | <urn:uuid:3e888568-b721-4f4c-a633-b7c4c30505ae> | 3.3125 | 152 | Documentation | Software Dev. | 55.592727 |
infrared image of the star formation region Messier 17. Three
infrared wavebands, from 1 to 2.2 microns, have been combined
to provide a visual representation of the region as if we had
infrared eyesight. The circles show the regions studied with
the UNSWIRF camera - the northern and south-western bars of
the M17. Original image provided by Michael Merrill from the
US National Optical Astronomy Observatories.
molecules in space are comprised of the simplest kind, the hydrogen
molecule. It is over 10,000 times more abundant than the next most
common molecule, carbon monoxide. It might therefore be thought
that the study of molecular clouds, the sites for star formation
within the Galaxy, would be dominated by various types of measurement
of molecular hydrogen line emission. However this is not true. The
lowest lying energy levels of the hydrogen molecule are several
hundred degrees above the ground state, and therefore are not excited
in the cold conditions which are prevalent within molecular clouds.
emit when they are hot, through infrared lines from excited vibrational
and rotational states. Thus, when molecular hydrogen is observed
in space it points to an energetic event associated with star formation.
Typically this indicates either a shock wave or intense ultra-violet
radiation. The former occurs when winds or outflows from young stars
collide with molecular clouds, heating them to 1-2,000 degrees;
the latter when the energetic radiation field from massive stars
shines on a molecular cloud, fluorescing the gas.
There is, however,
potentially a third emission mechanism to be seen from molecular
hydrogenformation pumping. Hydrogen molecules form on surfaces
of dust grains. They release their binding energy on formation,
which both ejects them from the dust grain and places them into
an excited rotational / vibrational state. From this state they
will decay, thus giving rise to a formation spectrum.
The question is what will this spectrum look like, and could it
be observed on top of the strong shocked or fluorescent spectrum
which will also arise from the same regions? Predictions for the
formation spectrum have had it appearing in low-J, high-v levels,
or low-v, high-J levels, amongst other possibilities. Observations
have, till now, shed no light on the matter.
We believe that
we have now seen the first clear signature of molecular hydrogen
formation, through the emission from the v=64 O(3) line of
the molecule, which occurs at a wavelength of 1.74µm. Using
the UNSW Infrared Fabry-Perot (UNSWIRF) on the Anglo Australian
Telescope, we used a specially designed filter to pick up several
diagnostic emission lines near 1.7µm. We studied the massive
star formation region Messier 17 (the Omega Nebula). This is a strong
source of fluorescent line emission, arising from the molecular
cloud which surrounds a cluster of young stars. Fluorescence is
evident in the emission from the v=1 and 2 levels of the hydrogen
molecule. However the v=64 O(3) line, arising from the v=6,
J=1 level of H2, was found to have a quite different spatial distribution
to the lower-v lines, a result we attribute to the formation of
the molecule in this, or in a nearby, excited state. This is the
first clear detection of the emission from the formation of molecular
hydrogen in the interstellar medium, a fundamental process which
leads to the building of giant molecular clouds, and then to the
stars which form in them. | <urn:uuid:1c7e14e3-2de1-447d-bdf2-7e589df50b1a> | 3.3125 | 783 | Academic Writing | Science & Tech. | 43.634399 |
The Blacktip shark, Carcharhinus limbatus, is a large shark, native to the continental and insular shelves of tropical and warm temperate seas around the world.
The Blacktip is a large fairly stout shark, grey in color, normally with black-tipped fins. It has a long, narrow, pointed snout, long gill slits, a large first dorsal fin and fairly large second dorsal.
The Blacktip shark was first described by Achille Valenciennes in Müller & Henle (1839) as Carcharias (Prionodon) limbatus. The accepted scientific name is Carcharhinus limbatus (Müller & Henle, 1839). The epithet limbatus (“bordered”) refers to the black tips of its fins.
Behavior and diet
Like its close relative the spinner shark, the Blacktip shark is a fast swimming shark capable not only of breaching but also of rotating (spinning) several times before re-entering the water. It is non-aggressive and would be unlikely to attack humans without stimulus.
There is some evidence of segregation with some populations showing separation between groups of adult males and non-pregnant females on the one hand and pregnant females and young on the other.
Blacktip sharks feed mainly on a wide range of bony fish: sardines, herring, mullet, jacks, and Spanish mackerel, among others; the young of other sharks including dusky sharks; and some cephalopods and crustaceans.
The Blacktip shark is viviparous and has a yolk-sac placenta with 1 – 10 pups per litter (4 – 7 as a mean figure). The gestation period is believed to be 10 to 12 months and females are thought to breed every other year.
Importance to humans
Its flesh is used fresh, dried or salted for consumption; its hide is used for leather and its liver for oil. It is occasionally taken as a game fish and often by shore anglers. It has not been indicated in unprovoked attacks against humans but is potentially dangerous. | <urn:uuid:757b160e-dddc-4546-822a-5d3ad095f785> | 3.765625 | 456 | Knowledge Article | Science & Tech. | 45.245047 |
Sep. 19, 2005 Images returned during Cassini's recent flyby of Titan show captivating evidence of what appears to be a large shoreline cutting across the smoggy moon's southern hemisphere. Hints that this area was once wet, or currently has liquid present, are evident.
"We've been looking for evidence of oceans or seas on Titan for some time. This radar data is among the most telling evidence so far for a shoreline," said Steve Wall, radar deputy team leader from NASA's Jet Propulsion Laboratory, Pasadena, Calif.
The images show what looks like a shoreline dividing a distinct bright and dark region roughly 1,700 kilometers long by 170 kilometers wide (1,060 by 106 miles). Directly to the right of a bright and possibly rough area is one that is very dark and smooth.
"This is the area where liquid or a wet surface has most likely been present, now or in the recent past, said Wall. "Titan probably has episodic periods of rainfall or massive seepages of liquid from the ground."
The brightness patterns in the dark area indicate that it may once have been flooded with liquid that may now have partially receded. Bay-like features also lead scientists to speculate that the bright-dark boundary is most likely a shoreline.
"We also see a network of channels that run across the bright terrain, indicating that fluids, probably liquid hydrocarbons, have flowed across this region," said Dr. Ellen Stofan, Cassini associate radar team member from Proxemy Research, Laytonsville, Md.
Taken together with the two other radar passes in October 2004 and February 2005, these very high resolution images have identified at least two distinct types of drainage and channel formation on Titan. Some channels in images from this pass are long and deep, with angular patterns and few tributaries, suggesting that fluids flow over great distances. By contrast, others show channels that form a denser network that might indicate rainfall.
Dr. Larry Soderblom with the U.S. Geological Survey in Flagstaff, Ariz., said, "It looks as though fluid flowed in these channels, cutting deeply into the icy crust of Titan. Some of the channels extend over 100 kilometers (60 miles). Some of them may have been fed by springs, while others are more complicated networks that were likely filled by rainfall."
Titan has an environment somewhat similar to that of Earth before biological activity forever altered the composition of Earth's atmosphere. The major difference on Titan, however, is the absence of liquid water, and Titan's very low temperature. With a thick, nitrogen-rich atmosphere, Titan was until recently presumed to hold large seas or oceans of liquid methane. Cassini has been in orbit around Saturn for a year and has found no evidence for these large seas.
Cassini encountered an anomaly with one of two solid-state recorders during the Sept. 7 close flyby, resulting in some data not being recorded. Half of the data from the flyby was received, much to the delight of anxious scientists. The spacecraft team is troubleshooting the cause, and early indications point to a software problem that would be correctable with no long-term impacts.
This was Cassini's eighth out of 45 Titan flybys planned in the nominal four-year tour. The next radar pass will be Oct. 26 when the team will focus on the Huygens probe landing site close to the equator.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument team is based at JPL, working with team members from the United States and several European countries.
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Note: If no author is given, the source is cited instead. | <urn:uuid:1e5469f2-8548-4970-a7ee-1507db24b305> | 3.421875 | 855 | Truncated | Science & Tech. | 45.489967 |
SQLIPA: An Authentication Mechanism Against SQL Injection
Web application has been developed with very rapid progress. Web applications use database at backend for storing data and SQL for insertion and retrieval of data. There are some malicious attacks which can deceive this SQL. These attacks are called SQL injection. To stop SQL injection many techniques have been proposed but they require large code modification and/or large extra time overhead. The work of this paper proposes a technique using hash values of user name and password, to improve the authentication process. The paper had built a prototype, SQL Injection Protector for Authentication (SQLIPA), for the evaluation of idea. | <urn:uuid:63a7d14e-96c4-43a5-bff1-88b5a5f7e56a> | 2.84375 | 129 | Academic Writing | Software Dev. | 30.591667 |
Fuel cells are the dream power source for vehicles: they can use hydrogen and oxygen as fuel and oxidizer, respectively, and produce only electricity and water (plus a little heat). Compared to battery-powered electric vehicles, hydrogen-powered fuel cell vehicles offer higher energy density, which leads to greater range and lower weight. Sure, they have their downsides—such as requiring a complete hydrogen infrastructure à la oil pipelines and fueling stations—but batteries vs. fuel cells is a debate for another day (and story).
The first hydrogen fuel cell vehicle (General Motors/Chevy Electrovan) was created in 1966. Researchers have been developing proton exchange membrane (PEM) fuel cells for past 15 years. So why don’t we see any in cars on the road? In a word: catalysts. Despite intense development, catalysts used in PEM fuel cells haven’t reached the levels of performance, lifetime, or cost to be commercially viable. In a recent issue of Nature, Mark Debe, senior scientist in the Fuel Cell Components Program at 3M, summed up the recent progress and prospects for fuel cell catalysts, including potential manufacturing issues.
First off, what is a catalyst? How does a fuel cell even work? What is the air-speed velocity of an unladen swallow? (African or European?) One question at a time, please.
In brief, a fuel cell directly converts the chemical energy locked in a fuel (like hydrogen) into electricity though a reaction with an oxidizer (typically, oxygen). All fuel cells consist of an anode, cathode, and electrolyte, which classifies the type of fuel cell (for example, in a PEM fuel cell, the PEM is the electrolyte) and allows the charges to move between the anode and cathode.
In the case of hydrogen and oxygen in a PEM fuel cell, hydrogen is split on the anode side into protons and electrons. The protons travel through the membrane electrolyte while the electrons move through an external circuit—generating an electrical current—to the cathode, where oxygen molecules react with the arriving protons and electrons to create water.
Each individual fuel cell generates only a small amount of electricity (less than a volt), so the overall “fuel cell” is actually a stack of a couple hundred cells. Each cell, or membrane electrode assembly, is comprised of the two electrodes (anode and cathode) sandwiching the PEM, surrounded by porous gas diffusion layers that bring the fuel and air in and water out.
The overall reaction occurring in a fuel cell is the same as when you burn hydrogen: hydrogen plus oxygen produces water and energy. In both cases, the energy of the system must reach a certain activation level before the reaction will proceed. In the case of combustion, this is done with an ignition source such as a high-temperature spark. PEM fuel cells, on the other hand, operate at much lower temperatures. This is where the catalyst comes in: it effectively lowers the activation energy by increasing the reaction rate without being consumed in the process. (By contrast, solid oxide fuel cells operate at much higher temperatures and therefore don’t need a catalyst).
The most effective catalysts in hydrogen fuel cells use platinum for both the anode and cathode. Here is the problem (one of the problems, at least): platinum is expensive. Right now, the cost is over $1400 per troy ounce, just under that of gold. Most catalyst research focuses on how to use less platinum (or none at all) while simultaneously increasing performance and durability.
With all this in mind, let’s take a look at where we are now.
You may not realize it, but we actually do have some cars running on hydrogen on the road. The US Department of Energy (DOE) teamed up with a couple major car manufacturers (Ford, Hyundai, Kia, Daimler, and GM) to test a total of almost 200 vehicles. According to DOE reports, these test fleets used at least 0.4 milligrams of platinum per square centimeter on the cathode alone. The goal for 2017 is to use 0.125 milligrams per square centimeter of platinum group metals (which includes ruthenium, rhodium, palladium, osmium, iridium, and platinum) total between the anode and cathode. In a fuel-cell assembly rated at eight kilowatts per gram of platinum, this works out to eight grams total per vehicle—close to what is used in current internal combustion engines (in the catalytic converter).
According to a DOE technical plan, as of 2011 we’ve reached a power density of about 5.3 kilowatts per gram of PGM, and 0.15 milligrams of PGM per square centimeter—nearly there. However, the stability of the catalyst isn’t yet where we need it, limiting the lifespan to below the 5,000 hour target (corresponding to about 150,000 miles).
There are two conventional platinum-based catalyst approaches. The first uses “Pt blacks,” which are extremely small platinum particles that absorb light very well and appear black, with high surface-to-volume ratios—ideal for a catalyst, where the reaction activity occurs on the surface. The second involves platinum nanoparticles spread onto larger carbon black particles. However, both of these approaches would require far too much (expensive) platinum to reach the performance and durability goals necessary for use in commercially viable fuel cells.
Faced with the difficult task of improving catalyst performance but at the same time using an equal or less amount of platinum, researchers decided to simply design new catalyst nanoparticles.
New catalyst designs
Debe classified the new designs for platinum-based catalysts into four categories. The first, extended surface area catalysts, is fairly self-explanatory. By increasing the surface area, such as by applying thin films on particles or using a porous film, these catalysts can increase reaction activity while using less platinum in the process.
The most promising approach in this category appears to be nanostructured thin-film (NSTF) catalysts. In these, a thin film of a platinum alloy coats a tiny, thin layer of crystalline, organic whiskers. Each whisker is less than a micrometer tall and over 2,000 times thinner than a human hair. Since NSTF catalysts are so thin, the volume is low, resulting in a high surface-area-to-volume ratio. In addition, the organic whiskers are not conductive, preventing any corrosive electrical currents.
The second category involves platinum or platinum-alloy nanoparticles on low-aspect-ratio carbon black or oxide support particles. This is similar to the conventional approach using platinum nanoparticles, except now the size and shape of the nanoparticles are controlled to increase reaction activity and reduce the amount of platinum. The sizes are on the order of nanometers, and the shapes include octahedra, cubes, and more exotic shapes like truncated octahedrons.
Another promising approach in this category uses core-shell nanoparticles (think of a hollow ball). In these, the amount of platinum is reduced significantly since it is removed from the core, and the reaction activity can be increased by filling the core with a material that optimizes properties of the surface platinum layer. Core materials include palladium and palladium alloys with cobalt, iron, iridium, and gold, as well as alloys of other metals like gold and nickel. There are some issues to overcome with these catalysts, though. The performance in actual fuel cells wasn’t as high as in laboratory tests, and researchers need to develop a scalable manufacturing process capable of generating the particles without leaving a pinhole in the platinum layer (to protect the core from leaching).
Other categories of new platinum-based catalysts include nanoparticles on high-aspect-ratio supports (like carbon fiber or nanotubes) and unsupported nanoparticles (such as lone platinum nanotubes or nanoparticles). No specific catalyst designs in either of these have demonstrated particularly high performance yet, however.
What about avoiding platinum—and its high costs—altogether? Researchers have investigated catalysts using palladium and its alloys, but the performance can barely reach that of conventional platinum-based catalysts. Plus, the price isn’t that much cheaper.
Recently, according to Debe, catalysts avoiding precious metals altogether—using metals such as cobalt and iron—have demonstrated huge performance improvements. For example, an iron-based cathode catalyst reached about a tenth of the current density of platinum-based cathodes. However, the lifetime of such catalysts appears to be shorter at the voltage potentials necessary for use in vehicle fuel cells, so this area still needs some work.
Given all of these different approaches under development, which are the most promising? Several of the concepts mentioned above—in particular, the NSTF and shape/size-controlled nanoparticle catalysts—appear to perform at levels necessary to meet DOE targets. Even commercially available platinum-alloy/carbon catalysts come close, although the durability isn’t yet where it needs to be.
Of course, even the most promising catalyst technology still has to be manufactured. Up until now, the quantity of catalysts required for the small number of test vehicles (less than 200 for the DOE studies) didn’t pose much of a challenge. DOE cost targets are based on half a million fuel-cell vehicles produced per year, and the numbers start to get much bigger if the technology is to spread into the larger world market.
To demonstrate the scales involved in manufacturing fuel-cell catalysts for a large number of vehicles, Debe ran some numbers. Producing fifteen million vehicles (ten percent of the global market in 2030) would require 4.5 billion individual fuel cells if each stack contained 300 cells (each about 300 square centimeters in area). Given a production line operating at full capacity, this requires around 11,700 individual cells per minute (worldwide). Cars are produced around one per minute in each production line, so to match this, 20 fuel-cell lines would have to each produce 10 fuel cells a second.
What about the catalyst, which we’ve spent so much time talking about? At the target area density for platinum of 0.1 milligrams per square centimeter, the electrodes will be less than two micrometers thick—meaning precision coating methods. To produce the number of fuel cells needed, the production lines will have to run at 20 meters per minute. This would require one and a half kilograms of platinum per hour, or nearly $1.7 million worth of platinum in a day. Every day, per manufacturing line. This may seem high, but it is similar to the cost of platinum group metals already used in cars—that is what the target density is based on.
According to Debe, these manufacturing requirements will lead to a catalyst-coating approach similar to that already used to produce most multi-layer optical-film-coated glasses: all-dry vacuum coating. In that sector, manufacturers are already making 250 million square meters of glass per year—far more than the 135 million square meters of catalyst than would be needed.
Debe believes that, based on current progress, catalyst performance will peak in a few years well above the DOE goals for 2017. In fact, he argues that improving performance shouldn’t be the primary goal of researchers at this point—catalysts are already where they need to be. Instead, research should focus on creating catalysts that not only hit the durability and power targets, but can be manufactured at high volumes.
According to the article, there is cause for optimism. Recent developments in new kinds of catalysts offer higher performance without reducing the lifetime or increasing the cost. However, it will still be a few years before any of the newer concepts can be incorporated into realistic fuel cells, with the issue of high-volume manufacturing looming in the approaching horizon. | <urn:uuid:7eadc95d-955a-4d8d-819d-ee42152a0431> | 4 | 2,499 | Knowledge Article | Science & Tech. | 36.433148 |
For many years now, volunteers working from home —people like you— have been able to help scientists with important problems.
In the first wave of these “citizen science” projects, people simply lent their computers to help solve problems that could be farmed out in pieces to thousands of machines. Among the first of these was searching incoming radio signals for evidence of extraterrestrial intelligence, although my favorite involved analyzing the folding of proteins to help study diseases and treatments.
More recently, people with spare time have been able to go beyond just lending their computers to take a much more active role. Sitting at home in your pajamas, you can perform tasks like transcribing data from antiquated written records. As I pointed out last year, anybody who cares about climate science can get in on the act, helping to digitize paper records from old ships’ logs and weather balloons.
The Old Weather project might be the most interesting of these schemes, but in its initial incarnations, only British ships were included among the logs to be transcribed. Now two American agencies, the National Oceanic and Atmospheric Administration and the National Archives and Records Administration, have joined forces with Old Weather to put American ships’ logs into the mix.
The first records in need of transcription are logs from Arctic expeditions that sailed between 1850 and World War II. “Participants in Old Weather-Arctic will be able to work with the logbooks of the doomed 1879 U.S.S. Jeannette Arctic expedition, the Revenue Cutter Thomas Corwin that carried the famous naturalist John Muir to the far north in 1881, and the Coast Guard cutter Bear that sailed the coasts of Alaska for nearly 50 years,” NOAA says.
The information in these records that will be most useful to climate scientists is weather data, of course. But the material is also expected to find uses in other fields, including history and genealogy. How cool would it be to know the exact date and time and place that your great-great-great-grandfather stood on the deck of the Bear to record the frigid weather off the Alaskan coast?
Go here to sign up, then click on the Old Weather link. | <urn:uuid:b9a45a6b-5ebb-4536-8346-55eb5b52207c> | 3.171875 | 454 | Personal Blog | Science & Tech. | 46.096212 |
WCSCMP(3) Linux Programmer's Manual WCSCMP(3) NAME wcscmp - compare two wide-character strings SYNOPSIS #include <wchar.h> int wcscmp(const wchar_t *s1, const wchar_t *s2); DESCRIPTION The wcscmp() function is the wide-character equivalent of the strcmp(3) function. It compares the wide-character string pointed to by s1 and the wide-character string pointed to by s2. RETURN VALUE The wcscmp() function returns zero if the wide-character strings at s1 and s2 are equal. It returns an integer greater than zero if at the first differing position i, the corresponding wide-character s1[i] is greater than s2[i]. It returns an integer less than zero if at the first differing position i, the corresponding wide-character s1[i] is less than s2[i]. CONFORMING TO C99. SEE ALSO strcmp(3), wcscasecmp(3), wmemcmp(3) COLOPHON This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. GNU 1999-07-25 WCSCMP(3)
Generated by dwww version 1.11.3 on Wed May 22 17:42:39 CEST 2013. | <urn:uuid:de47810e-01fb-405d-ae41-66825e0bc6b3> | 2.6875 | 323 | Documentation | Software Dev. | 84.855936 |
MessageToEagle.com - Ants actively leave their nests before death and break up all social contact.
This social withdrawal is not due to manipulation through pathogens or parasites but it appears to be an altruistic act of the ants themselves.
The ants use chemistry and crowdsourcing, according to the research published in
When ants are confronted with information overload and face too many decisions - about where to live, for instance -
they revert to the wisdom of the crowd.
Despite having a brain smaller than the point of a pin, one ant species uses an elaborate system of sending out scouts
to look for new homes. The scouts report back, and then the whole colony votes, according to researchers at
Arizona State University.
"They have tiny brains, but nonetheless, they are able to do quite a bit with them," Pratt said. Honey bees also have small brains
but each brain has about a million neurons, which collectively have "quite a lot of processing power." Bees use a tail-wagging
dance to communicate.
The ants involved in the ASU study, Temnothorax rugatulus are red, about one-tenth of an inch long, and live in crevices between
rocks in forests in the western U.S. and parts of Europe.
The colonies themselves are not very big, usually a few hundred workers, Pratt said, and if an animal knocks a colony over, the
roof falls in, or if they need more space, the ants have to move.
"They distribute the task among colony members," said Sasaki.
That's where the crowdsourcing comes in.
According to Pratt and Sasaki, the ants send scouts to check out some potential home sites.
The scouts look at such things as the size of the entrance and how big the cavity is. If the ant likes what she sees, she returns to the colony.
She sends out a pheromone message, "Follow me," and another ant will join her in what is called tandem running. She takes her
colleague out to view the potential site.
If the second ant likes what she sees, she goes back and repeats the process, bringing back another ant. If she doesn't like it,
she merely returns to the colony. If enough ants like a site, the colony reaches a quorum, essentially choosing the new home.
The scouts pick up their nest mates and carry them to their new homes, usually taking the nest queen along with them.
Sasaki built an experiment in which one ant had to make the decision from two potential sites and then from eight. Half the
potential sites were unsuitable in both experiments. He was forcing the ants in the laboratory to do what ants in the wild would
not, send one ant to make the decision for the colony, Pratt said.
Individual ants, confronted with two choices, had no problems picking the most suitable site. When faced with choosing among eight,
however, an ant often selected the wrong place.
The two researchers tested a whole colony with the same choices, letting them send out more than one scout. The colonies, acting
as a crowd, did equally well in both experiments, picking suitable sites 90 percent of the time.
"It's a shared decision," Pratt said.
Part of the advantage of the colony system, Sasaki and Pratt hypothesized, is that each scout visited only a few potential sites,
minimizing the information it must process, while an individual ant, assigned to do it alone, had to visit them all and was the
victim of cognitive overload.
Evolution has produced the system that best increases the possibility of colony survival.
Honey bees have a similar system, said computer scientist James Marshall, from Sheffield University in the U.K. He models social
What we are seeing, he said, is something like how the human body functions: millions of cells organized into one super-organism.
In the case of the bees and ants, all the insects in the hive or nest form one individual organism.
"Here, it is very much of a group benefit," Marshall said. "Like super organisms, the interests of individuals are the same as
the interests of the group."
"Cognitive overload is a growing issue for human decision making, as unprecedented access to data poses new challenges to
individual processing abilities," Pratt and Sasaki wrote in their journal article. "Human groups also solve difficult problems
better when each group member has only limited access to information."
Lake In France Turns Red
This year, we have encountered the color red in places where we don't expect to see it. A while back the strange appearance
of Azov Sea stunned residents who saw how the water had turned red. The red rocks in China have also puzzled scientists for a long time.
Now, a lake in Southern France has also suddenly turned red.
An Incredible Geological Phenomena
Earth is an amazing planet and our nature is full of wonders. We have previously written about incredible singing plants.
This time we would like to focus our readers' attention on another amazing geological phenomena, namely so-called growing stones.
It is difficult to image that stones can really grow, but these stones seem to be alive!
Yangtze River In China Turns Red
We have seen on a couple of occassions how lakes and seas have suddenly turned red.
In August a lake in Southern France unexpectedly changed color and shortly before that the strange appearance of
Azov Sea stunned residents who saw how the water had turned red.... | <urn:uuid:69ef7040-4420-40ab-8f81-cb72858e14f7> | 3.0625 | 1,148 | Content Listing | Science & Tech. | 49.64632 |
More Logo for beginners. Now learn more about the REPEAT command.
At what angle should you release the shot to break Olympic records?
Turn through bigger angles and draw stars with Logo.
More Logo for beginners. Learn to calculate exterior angles and draw regular polygons using procedures and variables.
What happens when a procedure calls itself?
This is the second in a twelve part introduction to Logo for beginners. In this part you learn to draw polygons.
Learn to write procedures and build them into Logo programs. Learn to use variables.
Learn how to draw circles using Logo. Wait a minute! Are they really circles? If not what are they?
Write a Logo program, putting in variables, and see the effect when you change the variables.
STEM students at university often encounter mathematical difficulties. This articles highlights the various content problems and the 7 key process problems encountered by STEM students.
The third installment in our series on the shape of astronomical systems, this article explores galaxies and the universe beyond our solar system.
Learn about Pen Up and Pen Down in Logo
Can you puzzle out what sequences these Logo programs will give? Then write your own Logo programs to generate sequences.
See how little g and your weight varies around the world. Did this
variation help Bob Beamon to long-jumping succes in 1968?
Does weight confer an advantage to shot putters?
Moiré patterns are intriguing interference patterns. Create your own beautiful examples using LOGO!
This article explores ths history of theories about the shape of our planet. It is the first in a series of articles looking at the significance of geometric shapes in the history of astronomy.
Consider the mechanics of pole vaulting
A Short introduction to using Logo. This is the first in a twelve part series.
10 intriguing starters related to the mechanics of sport.
This part introduces the use of Logo for number work. Learn how to use Logo to generate sequences of numbers.
There has been a murder on the Stevenson estate. Use your
analytical chemistry skills to assess the crime scene and identify
the cause of death...
Under which circumstances would you choose to play to 10 points in
a game of squash which is currently tied at 8-all?
Design and test a paper helicopter. What is the best design?
The second in a series of articles on visualising and modelling shapes in the history of astronomy.
Maths is everywhere in the world! Take a look at these images. What mathematics can you see?
See how the weight of weights varies across the globe.
Can you drive a pointer using LOGO to create a simple version of
the Olympic Rings logo?
Have you ever wondered what it would be like to race against Usain Bolt?
Could nanotechnology be used to see if an artery is blocked? Or is this just science fiction?
An introduction to bond angle geometry.
Use the computer to model an epidemic. Try out public health policies to control the spread of the epidemic, to minimise the number of sick days and deaths. | <urn:uuid:03fa3402-e641-4e58-ac14-d28651e407dc> | 3.09375 | 629 | Content Listing | Science & Tech. | 55.92703 |
View all of the Antarctic Hemisphere daily maps of total ozone for February 1982. Satellite instruments monitor the ozone layer, and we use their data to create the images that depict the amount of ozone.
Click any map image to bring up a new page with a high-resolution map.
Missing areas (bad orbits and polar night) are filled from an atmospheric model. MERRA is a NASA reanalysis for the satellite era using a major new version of the Goddard Earth Observing System Data Assimilation System Version 5 (GEOS-5). The Project focuses on historical analyses of the hydrological cycle on a broad range of weather and climate time scales and places the NASA EOSsuite of observations in a climate context.
A week begins with Sunday. Fainter images are shown in the previous and following months. Missing days are indicated with a plain gray globe.
Monthly averages (1979–2013) | <urn:uuid:a70ed016-a61d-498f-9f51-d41cab1f23b3> | 3.3125 | 184 | Structured Data | Science & Tech. | 41.27138 |
NASA's Mars Exploration Rover Opportunity used its microscopic imager to get this view of the surface of a rock called "Block Island" during the 1,963rd Martian day, or sol, of the rover's mission on Mars (Aug. 1, 2009). The triangular pattern of small ridges seen at the upper right in this image and elsewhere on the rock is characteristic of iron-nickel meteorites found on Earth, especially after they have been cut, polished and etched. Block Island has been identified as an iron-nickel meteorite based on this surface texture and analysis of its composition by Opportunity's alpha particle X-ray spectrometer. At about 60 centimeters (2 feet) across, it is the largest meteorite yet found on Mars.
This image shows a patch 32 millimeters by 32 millimeters (1.3 inches by 1.3 inches) on the surface of Block Island while the target was fully illuminated by the sun. This target on the rock is informally named "New Shoreham." The vertical white streaks, especially near the top and bottom of the image, are artifacts caused by saturation of the camera's CCD (charge-coupled device, or image recorder) where sunlight glinted off metallic facets.
The triangular pattern in the texture of iron-nickel meteorites, called the Widmanstatten pattern, formed more than 4.5 billion years ago as the metal cooled. One iron-nickel mineral, kamacite, formed thin layers along the surface of crystals of another, taenite, which contains less nickel. The two minerals differ in their resistance to either etching by acid or erosion by wind-blown sand, so those processes can make the pattern visible. | <urn:uuid:27881946-df5f-4877-92ae-fac550fa89f7> | 3.59375 | 352 | Knowledge Article | Science & Tech. | 44.522555 |
This image shows a "bite mark" where NASA's Curiosity rover scooped up some Martian soil. The first scoop sample was taken from the "Rocknest" patch of dust and sand on Oct. 7, 2012, the 61st sol, or Martian day, of operations. A third scoop sample was collected on Oct. 15, or Sol 69, and deposited into the Chemistry and Mineralogy (CheMin) instrument on Oct. 17, or Sol 71.
This image was taken by Curiosity's Mast Camera. Scientists enhanced the color in this version to show the Martian scene as it would appear under lighting conditions on Earth, which helps in analyzing the terrain.
During the two-year prime mission of the Mars Science Laboratory Project, researchers are using Curiosity's 10 instruments to investigate whether areas in Gale Crater ever offered environmental conditions favorable for microbial life.
Image Credit: NASA| | <urn:uuid:62cacd6f-4b6b-4ea6-aea7-a965e94f8984> | 3.5 | 179 | Truncated | Science & Tech. | 50.813513 |
HR 8799Article Free Pass
HR 8799, star that has the first extrasolar planetary system to be seen directly in an astronomical image. HR 8799 is a young (about 60 million years old) main-sequence star of spectral type A5 V located 128 light-years from Earth in the constellation Pegasus. Observations of this star taken by the Infrared Astronomical Satellite and the Infrared Space Observatory showed a disk of dust such as that expected in the last stages of planetary formation. In 2008 an international team of astronomers released images taken with the telescopes at the Keck and Gemini North observatories of three planets orbiting HR 8799. A fourth planet was discovered in 2010. Observations show that the planets move with the star and therefore are not background objects. The planets range in mass from 7 to 10 times that of Jupiter and orbit between 2.2 and 10.2 billion km (1.3 and 6.3 billion miles) from HR 8799. These planets are gas giants with temperatures of about 900 to 1,100 kelvins (600 to 800 °C, or 1,200 to 1,500 °F).
The table lists comparative data for the planets of the HR 8799 system.
|object||distance from star||mass
|HR 8799b||71||10,600||7 (5–11)||~460||86,000|
|HR 8799c||38||5,700||10 (7–13)||~190||86,000|
|HR 8799d||24||3,600||10 (7–13)||~100||86,000|
|HR 8799e||14.5||2,200||9 (5–13)||~50|
|*One astronomical unit (AU) is the mean distance of Earth from the Sun.
**Numbers in parentheses indicate a range of likely masses.
What made you want to look up "HR 8799"? Please share what surprised you most... | <urn:uuid:46a7ed4d-6ff8-4df0-b4b6-b6e6a58de2c6> | 3.546875 | 413 | Knowledge Article | Science & Tech. | 86.992303 |
ne much-lauded feature of PostgreSQL is transactions. Transactions in a database help prevent accidental data loss or misrepresentation.
For example, let's say you want to delete records from a table. In PostgreSQL the command is:
template1=# DELETE FROM foo;
However, the above command will delete all of the records in the table. This is probably not what you want, andunless you were using transactionsthe only way to get the data back would be from a backup. Using transactions, getting the data back is simple. The command sequence would be:
DELETE FROM foo;
statement causes the database to initiate a transaction, so as soon as you realize that the preceding command failed to include a WHERE
clause, thus deleting the entire table, you could rollback the transaction.
DELETE FROM foo;
There is a drawback to using transactions in the current version of PostgreSQL. If any error occurs in the statements within your transaction, you must
issue a rollback. A rollback is issued by executing the rollback command within the transaction and must be executed before any other commands will be processed by your specific connection. Once a rollback is executed you must begin the transaction again and restate the commands in a manner that will not cause an error. This rule includes both user errors, such as deleting all records in a table, and syntactical errors, such as trying to select from a table that does not exist. For example:
UPDATE foo SET bar = (SELECT count(*) FROM baz));
INSERT INTO foo (column1) SELECT column2 FROM bar;
ERROR: relation "bar" does not exist
CREATE TABLE bar (column1 text, column2 float);
ERROR: current transaction is aborted,
commands ignored until end of transaction block
Because of the error, you will have to rollback and all your current work will be lost. This particular aspect of transactions with PostgreSQL is particularly irritating during testing and debugging. | <urn:uuid:2c169043-3e18-4682-a43c-0f641f4f47a0> | 2.984375 | 414 | Tutorial | Software Dev. | 39.538666 |
Here we are providing you an example with code that retrieves all columns name in a specific database table. Sometimes, you need to know the number of columns and the names of the columns of the table, so you can retrieve it with the help of this example. See detail information given below:
Description of program:
Create a class ColumnName. The name of the class should be such that the other person can easily understand what this program is going to do. Strictly follow the naming conventions of java. Now declare a static method inside which creates the connection with MySQL database through the JDBC driver. After establishing the connection then you get all columns name and number of columns of specified table with the help of some APIs and methods.
Description of code:
This is an interface of java.sql package that can be used for getting information about types and properties of columns in a ResultSet object.
Above method retrieves number of columns (integer types data) in the ResultSet object.
This method returns columns name (string type data) from ResultSetMetaData object and takes integer type value.
Here is the code of program:
Output of program:
Getting Column Names Example!
Number of Column : 2
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | <urn:uuid:b3243a48-6b00-4797-934c-0dfedc2577f5> | 2.875 | 292 | Documentation | Software Dev. | 45.437189 |
In mathematics, an operator is a function, usually of a special kind depending on the topic. An operator is a function that acts on functions to produce other functions. A operator symbol or operator name is a notation that denotes a particular operator.
There are many types of operators.
The code of the program is given below:
<HTML> <HEAD> <TITLE>Using Operators in Jsp</TITLE> </HEAD>
<BODY> <table border="1" align="center"> <tr><td> <H1>Using Operators in Jsp</H1> <% int Operator1 = 23, operartor2 = 40, SumOper;
SumOper = Operator1 + operartor2 ;
out.println(Operator1 + " + " + operartor2 + " = " + SumOper); %></tr></td> <BR><BR> <tr><td> <% int Operator3 = 3, operartor4 = 4, MulOper;
MulOper = Operator1 * operartor2 ;
out.println(Operator1 + " * " + operartor2 + " = " + MulOper); %></tr></td> </table> </BODY> </HTML>
Output of the Program:
If you are facing any programming issue, such as compilation errors or not able to find the code you are looking for.
Ask your questions, our development team will try to give answers to your questions. | <urn:uuid:21950a0a-1713-41ad-bab1-6dc4abe6d6ca> | 3.84375 | 315 | Documentation | Software Dev. | 39.276969 |
Imagine you’ve been working on a problem for days, maybe even weeks, but you can’t seem to figure it out. Your brain is working over solutions constantly but you feel stumped. So, you take a break. You walk down the street to the nearest coffee shop but as you’re walking home, sipping your drink and watching cars drive by, the solution rushes into your brain. That’s it!
In the above scenario, you aren’t thinking of the problem. You’re thinking of the coffee in your hand, the cars driving by, or the directions back to your house. That problem, that horribly frustrating problem, is solved almost out of thin air. What you’ve experienced is known as spontaneous and cognitive creativity. Your basal ganglia, a part of the brain involved in unconscious functions, took over your conscious brain’s efforts to solve the problem. Even while you were walking to the coffee shop and consciously paying attention to other stimuli (the coffee, the cars), your basal ganglia was working through the problem until it arriving at a solution. That’s the spontaneous part; the cognitive part is need for prior knowledge. You can’t have a spontaneous solution to a biology problem, for example, if you know nothing about biology.
This type of creativity brings up an interesting framework for understanding why scientists and engineers experience a different type of creativity from those in the entertainment industry. It’s not that the old myth of analytical, non-creative scientists and engineers is true – it’s just a different way of being creative (and we’ve got the science to back up that claim!).
Four Ways to Be Creative
Neuropsychologist Arne Dietrich studies the neuroscience of creativity, among other topics like consciousness. His research segments creativity into four types: deliberate and cognitive, deliberate and emotional, spontaneous and cognitive, and spontaneous and emotional. The type most associated with scientists and engineers is deliberate and cognitive, which equates to sustained focus in an area, such as a neuroscientist studying the brain.
Deliberate and cognitive creativity come from the prefrontal cortex, the part of the brain located behind your forehead. It is the area responsible for focused attention and forming connections between information stored in the brain. You can see how this might relate to a scientist or engineer: deliberate focus, cognitive knowledge of a subject area, and the ability to form connections between information.
On the other hand, artists, musicians, writers, and other traditional creative careers are associated with spontaneous and emotional creativity. This type of creativity stems from the amygdala, the part of the brain that processes basic emotions. In between are spontaneous and cognitive creativity (explained above) and deliberate and emotional creativity, which is akin to working through emotional thoughts or issues. But if you work in one mode of creativity, it does not preclude you from the other types of creativity. A scientist might study research through deliberate and cognitive creativity, but experience spontaneous and emotional creativity while engaged in other creative endeavors. (In fact, we know quite a few scientists and engineers who are also artists or musicians.)
Or, when a problem can’t be solved by deliberate and cognitive creativity, the brain can use spontaneous and cognitive creativity to find a solution. The Big Bang Theory’s Sheldon Cooper found this out during the episode "The Einstein Approximation." Everyone’s favorite fictional theoretical physicist found himself stumped on a problem, and nearly drove himself mad by trying to solve it with deliberate and cognitive creativity. But a short stint as a waiter at The Cheesecake Factory, where he was able to focus on other tasks, freed his basal ganglia to work toward a solution.
Sheldon also discovered another way to solve a problem in the episode: sleep. When you can’t think of a solution, studies have shown REM sleep will help you figure it out!
Homepage image credit: opensourceway
Top image credit: qpemfacilitators.wordpress.com | <urn:uuid:8629d154-b6c0-4732-af19-2e98defac18c> | 2.875 | 828 | Personal Blog | Science & Tech. | 37.06154 |
Happy New Year! Tomorrow is the first day of 2009. So what an appropriate time to look back and see what we have accomplished in science over the past years on this day.
On New Years Day, 1801, the dwarf planet Ceres was discovered by Giuseppe Piazzi. This dwarf planet is actually located inside our solar system, it is part of the asteroid belt between Mars and Jupiter. Astronomer Johann Elert Bode had suggested nearly forty years earlier that their might be large planets or land masses between Mars and Jupiter based off a theory (that is no longer used) proposed in 1766 by Johann Daniel Titus. It was this same theory that led to the discovery of Uranus in 1781. Because of the theory and the unknown location of a planet between Mars and Jupiter, 24 astronomers combined their efforts and began a methodical search for the planet.
|photo credit: Venom82|
On New Years Day, 1985, the Internet domain name system was created. The domain name system translates human names for sites into the numerical or binary identifiers associated with network equipment. A simple explanation is that the Internet domain name system acts as a “phone book” for the Internet by translating a human-friendly host name into an IP address.
|photo credit: mackenzienicole|
On New Year’s Day, 1995 the existence of freak waves was proven. The Draupner oil platform in the north sea was usually hit by large waves measuring about 39 feet in height. However, on Jan 1st of that year a freak wave that was 89 ft tall crashed down on the platform. Freak waves had been thought to exist before based off of stories of sailors, but it had never previously been recorded. | <urn:uuid:ed3796c7-03ab-419a-bf66-d9c3f0ede9f2> | 3.578125 | 354 | Personal Blog | Science & Tech. | 54.085562 |
Date of this Version
As natural predators of pest insects, woodland birds provide biological pest suppression in crop fields adjacent to woody edges. Although many birds using these habitats forage widely, earlier studies have found that most foraging activity occurs within 50 m of the woody edge. The goals of this study were to determine the primary area of use, or functional edge, for birds foraging in crop fields adjacent to woody edges, and to evaluate their foraging distance patterns. During the summers of 2005 and 2006, avian foraging behavior was observed at 12 research sites in east central Nebraska that contained either a shelterbelt or woody riparian edge. At each site, perches were provided at 10 m intervals out from the edge and insect larvae were placed in feeders at random locations to simulate a pest insect food resource. Birds were recorded foraging in five distance categories out from the edge (0–10, 10–20, 20–30, 30–40, and 40–50 m). Seven species foraged primarily within 20 m of the edge (72% all observations; 79% without perch or feeder observations). Ten species foraged throughout the plots but six of these generally foraged more often (45% and 49%) and four less often (30% and 30%) within 20 m of the edge. The 13 species that tended to forage more often within 20 m of the edge, with 56% of their foraging overall in this area, also tended to forage farther when perch and feeder observations were included, indicating willingness to forage farther when food resources were available. Based on a repeated measures analysis of variance, foraging distances appeared to be greater at sites with soybean as the planted crop, although this apparent trend was significant for only some species. There was no clear difference in foraging distances outward from shelterbelt versus riparian sites. These results indicate that conservation efforts within the 20 m functional edge offer potential to enhance the sustainability of both birds and crops in agricultural. | <urn:uuid:05b644dc-4f43-4d53-bf9c-b3a0c79f28d1> | 3.5 | 407 | Academic Writing | Science & Tech. | 34.846136 |
Posted Dec 8, 2005 10:03 UTC (Thu) by pkolloch
Parent article: The Boost C++ Libraries
One of the very impressive features are lambda functions (IMHO):
for_each(a.begin(), a.end(), std::cout << _1 << ' ');
"std::cout << _1 << ' '" defines lambda function object taking one parameter.
Unfortunately, one cannot totally freely define those. Correct me, if I am wrong, but the following should not be possible:
for_each(a.begin(), a.end(), std::cout << "blupps: " << _1 << ' ');
The "<<" is evaluated from left to right. That means that std:cout << "blupps: " is evaluated before the special magic _1 can interfere and "blupps: " is printed immediately. (there is some special function to make this possible, I do not remember)
Functional conditional statements like "if_then" etc. are also provided for usage inside of lambda functions.
to post comments) | <urn:uuid:33ddd468-a825-4df3-96ce-64017c8893d7> | 3.0625 | 233 | Comment Section | Software Dev. | 54.691172 |
Name: Kate A Shuchter
We are teachers in Colorado planning to work with fluid transport and
capillary action in vascular plants. According to our memories, at 33 feet the
forces of capillary action and gravity cancel each other out.
We would like to explore how a 100 foot tree can transport water to its
top. We are looking for factors that would effect long-term transport.
Is fluid pressure from below influential? Is soil type influential?
How about the purity of the water?
It's 32 ft, and that applies to siphoning. Capillary action is different
because it depends upon the surface tension properties of water.
Click here to return to the Biology Archives
Update: June 2012 | <urn:uuid:107893e0-a45e-49e9-ba20-be1eda54e3fb> | 3.390625 | 148 | Truncated | Science & Tech. | 56.255385 |
All these activities have something to do with multiplying and dividing. Can you spot the connections?
Put operations signs between the numbers 3 4 5 6 to make the highest possible number and lowest possible number.
On the planet Vuv there are two sorts of creatures. The Zios have 3 legs and the Zepts have 7 legs. The great planetary explorer Nico counted 52 legs. How many Zios and how many Zepts were there?
Investigate the different numbers of people and rats there could have been if you know how many legs there are altogether!
Use 4 four times with simple operations so that you get the answer 12. Can you make 15, 16 and 17 too? | <urn:uuid:0c60e951-db29-4a0a-9214-c6650e538fa0> | 3.421875 | 140 | Tutorial | Science & Tech. | 69.144115 |
- Calculate the EMT of the following weapons: 50 Mt, 10 Mt, 1 Mt, 100 Kt, 10 Kt.
- How much energy is contained in 1 Mt of TNT?
- If the overpressure is 20 psi, what is the associated wind velocity?
- What is the Mach Stem?
- Why is an overpressure of 'only' 5 p.s.i. likely to result in a 50% mortality rate for the occupants of residential structures?
- The overpressure for a 1-Kt ground burst is 10 p.s.i. at 1100 feet. What is the distance from ground zero will result in the same overpressure for a 64-Kt bomb?
- What fraction of the total energy released by a thermonuclear bomb goes into thermal radiation? Blast energy?
- What is the temperature of the surface of the fireball when it is at its maximum extent?
- At a distance of about seven miles from the burst point of a 1 Mt bomb, which effect is most dangerous to humans; blast or thermal radiation? Why?
- Will unprotected newspaper ignite if located one mile from a 10 megaton explosion?
- How far from a 10 Kt ground burst must you be in order for the pressure to be less than 1 p.s.i.?
- What are some of the biological hazards from fallout?
- What are some of the long-term radiation effects from a nuclear explosion?
- How many rems would produce mild radiation sickness?
- Discuss the predictions of the TTAPS study.
- Define delayed fallout.
- What effect would a nuclear exchange have on the ozone layer?
- What is the maximum radius of a fireball produced by a 100 Kt nuclear weapon?
- Why is strontium 90 a particularly dangerous component of delayed fallout?
- How are gamma rays emitted during a nuclear explosion?
- What are the effects of a High Altitude EMP?
- Give a short explanation of the relative importance of each of the four basic effects of a nuclear explosion for a 10 Kt bomb and a 10 Mt bomb.
click here for solutions | <urn:uuid:f76b3281-4141-40eb-bbce-09f232f3021c> | 3.375 | 443 | Tutorial | Science & Tech. | 72.813382 |
This image shows soil delivery to NASA's Phoenix Mars Lander's Microscopy, Electrochemistry and Conductivity Analyzer (MECA). The image was taken by the lander's Surface Stereo Imager on the 131st Martian day, or sol, of the mission (Oct. 7, 2008).
At the bottom of the image is the chute for delivering samples to MECA's microscopes. It is relatively clean due to the Phoenix team using methods such as sprinkling to minimize cross-contamination of samples. However, the cumulative effect of several sample deliveries can be seen in the soil piles on either side of the chute.
On the right side are the four chemistry cells with soil residue piled up on exposed surfaces. The farthest cell has a large pile of material from an area of the Phoenix workspace called "Stone Soup." This area is deep in the trough at a polygon boundary, and its soil was so sticky it wouldn't even go through the funnel.
One of Phoenix's solar panels is shown in the background of this image.
The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.
Photojournal Note: As planned, the Phoenix lander, which landed May 25, 2008 23:53 UTC, ended communications in November 2008, about six months after landing, when its solar panels ceased operating in the dark Martian winter. | <urn:uuid:fe222e66-b704-46bb-8b6d-d4c2de576da8> | 3.21875 | 314 | Knowledge Article | Science & Tech. | 47.627581 |
Dr. James Lovelock roposed the GAIA concept. Few ideas have ignited more contentious debate within the modern scientific community than James Lovelock's Gaia hypothesis -- the proposal that the Earth can be viewed as a superorganism with the capacity to regulate its internal environment. Lovelock, an atmospheric chemist employed in the 1960s by NASA, first proposed the Gaia concept to account for the anomalous composition of Earth's atmosphere relative to those of neighboring Mars and Venus. The peculiar mix of gases that envelope Earth and support life on the planet, Lovelock argues, is created and maintained by Life itself. The composition of the atmosphere, in turn, profoundly affects Earth's climate, which has remained favorable for life for at least 3.5 billion years. Lovelock's thesis, then, is that organisms have collectively acted throughout the history of the planet to make the global environment hospitable for the biosphere as a whole. | <urn:uuid:2b21c3cb-5196-48d2-aa50-5c3ddc355c4f> | 3.359375 | 189 | Q&A Forum | Science & Tech. | 32.599596 |