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The plasma sea in which the solar system floats extends out to what is called the heliopause - where there is probably a double layer that separates our Sun's plasma from the lower voltage plasma that fills our arm of the Milky Way galaxy.
In solar flares and coronal mass ejections (CME's), charged particles are thrown outward from the Sun. These flows constitute electrical currents. And what form do (Birkeland) currents take in plasmas? - They twist!
Interactions of Magnetotails
The plasma sheath of Venus is extremely long, almost touching the Earth when the two planets are at their closest approach. Jupiter's plasma sheath has the same relationship with Saturn. Recently NASA astronomers have discovered what they call 'stringy things' in the long plasma tail of Venus. Such twisted (stringy) filaments are exactly the paths Birkeland currents take in plasmas.
Apparently Venus is discharging an electrical current. The plasma tails of all the planets today are in the dark current mode of operation. But were they always thus?
The ancients reported that Venus once was seen to have a fiery tail and 'twisted hair'.
Could it have been that her plasma tail was then in the normal glow or even the arc mode of operation?
So the Venusian tail is approximately a thousand times as long as it is broad at its thickest point. That is a very long, thin, twisting snakelike shape. If, at some time in the past, this plasma tail were in the normal glow mode, it would have been visible from Earth!
How would the ancients have described it?
Intersecting Plasma Sheaths
When a planet is surrounded by a double layer sheath, it is protected from direct electrical interaction with any outside body. Two electrically charged planets, each surrounded by such a plasma sheath cannot see each other electrostatically. However, if a body having a different electrical charge, penetrates the double layer, moving into the plasmasphere surrounding a planet, electrical interactions (current discharges) can and will occur.
Thus, if any other body such as a large meteor (or asteroid, comet, etc.) should come close enough to Earth to penetrate our plasma sheath, violent electric discharges would occur between the two bodies. It would, of course, be unfortunate to be standing at the point of origin of such a discharge.
But the discharge itself might destroy the intruder and thus protect the Earth from an otherwise disastrous collision.
NASA released the photo of Io shown below. Io is pretty much aglow. Note the heaviest glows on Io are on the sides directly toward and directly away from Jupiter. The famous 'volcanoes' on Io cannot be true volcanoes because they have moved around a distance of many miles since their discovery. Also the material ejected from the site of these phenomena is not disbursed over a circular area as volcanic ejecta would be.
lands in a thin ring - just as the output of a plasma gun does.
These are clearly electric discharges, not volcanoes.
NASA recently directed the Galileo space probe to pass very close to one of the "volcanos" (electric arc discharges) on Io - with the following result (New Scientist October 30, 1999):
Flying a computer through a high intensity electric field is much more likely to "zap" its electronics than simply passing it no nearer than 380 miles distant from some smoke and molten rock.
The Grand Canyon of Arizona would be lost in one small section of it.
There are many visible examples of electrical scarring on Mars. Electrical scars have characteristics that enable us to distinguish between them and water erosion and/or impact cratering.
exhibits evidence of having been electrically machined.
They are made up of chains of craterlets.
This too is characteristic of electric arc machining (certainly not water flow). Notice the faint horizontal rilles crossing the large one. The horizontal rilles obviously were made later than the large rille. Notice too that the horizontal rille goes up hill and down hill, cutting right across the earlier structure.
Terraced crater walls and small secondary craters sitting on the edge of larger craters are characteristic of electric arc machining. Also notice the flat floors and almost perfect circularity of the craters. If the twisting arc that creates an electrically formed crater stops on the rim and does not extinguish, it will form a secondary crater.
This effect is clearly demonstrated in a
laboratory experiment shown on physicist Wal Thornhill's CD "The Electric Universe."
Sinuous rilles are one of the typical characteristics of electric arc machining. The standard mainstream explanation for these horseshoe shaped craters is that one side of the crater wall has collapsed.
What do you think?
If all the "impact" craters on Mars, Venus, and our Moon were really formed by impacts, then probability would dictate that most (or at least a significant fraction) of them should be elliptical. Meteors very rarely come straight down. On the other hand, electric fields always impinge on conducting spheres at right angles to their surfaces (i.e., vertically) and that is why all these so-called circular "impact" craters are round.
They were not made by impacts.
They were caused by electric anode scarring.
But one of the official explanations is that,
And yet another property of Saturn's rings is that some of them are braided! They twist! The following is a quote from Science, Vol. 210, 5 Dec 1980, p. 1108:
Are the "braids" in Saturn's F ring due to just the kind of twisting currents that Birkeland observed? | <urn:uuid:6321ff35-1ca5-46fc-9881-088f62ff13b5> | 3.8125 | 1,186 | Knowledge Article | Science & Tech. | 47.247021 |
A small motor is mounted on the axis of a space probe with its rotor (the rotating part of the motor) parallel to the axis of the probe. its function of the probe about the axis. The moment of inertia of the probe is 6200 times that of the rotor. Initially, the probe and rotors are at rest. The motor is turned on and after some period of time, the probe is seen to have rotated by positive 32.6 degrees. Through how many revolutions has the rotor turned. | <urn:uuid:93a946d6-5e0c-4ce9-9496-0811b13a2652> | 3.109375 | 102 | Q&A Forum | Science & Tech. | 65.604157 |
In recent decades, technologies have been developed that harness the energy of the sun, the wind, the earth and even the ocean. While current supplies of coal, oil, and natural gas are finite and will eventually run out, wind and solar are examples of renewable energy. These sources are not limited and can be tapped indefinitely.
The concept of sustainable energy or green energy embraces practices, policies, and technologies that provide energy at the least financial, environmental and social costs. When these costs are factored in calculating life-cycle costs for fossil fuels, sustainable energy options make an even more compelling case for long-term strategic applications.
Types of renewable energy:
Join the Climate Institute e-news mailing list:
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This tutorial is an introductory guide to get you started in the world of server-side-scripting and web databases. It covers installation and configuration of MySQL, Apache, and PHP. An example script is also included as a guide for making your own server-side-scripts.
This guide walks you through installing a web server, an SQL database server, and a server-side scripting tool that ties everything together. Some of the more popular tools for doing this are Apache, MySQL, and PHP3.
This is what you will have accomplished after successfully completing this guide:
setup the MySQL database server
setup the Apache web server
setup the PHP 3.0 Hypertext Preprocessor for server-side-scripting
create a simple web enabled database
This guide is meant as an introductory guide to get you started in the world of server-side-scripting and web databases. It will help you get up and running with the aforementioned products, and hopefully give you a better understanding of how this stuff all works.
How It Works
It is helpful to have a feeling for what goes on behind the scenes, so here is an over simplification of how things would work,. This diagram isn't really correct but it should be enough for now:
So let's set the scenario. We have a web page that pulls some data out of a database. John Doe requests this page from his browser, the request is sent to the web server which in turn calls a PHP script. The PHP script is executed by the PHP preprocessor, it pulls data from the database. The results are then massaged by the rest of the PHP script and turned into HTML. The final HTML gets sent back to the user's browser.
Got that? Let's look at this step by step:
John Doe clicks on a link to from his web browser; his web browser sends a request for http://www.foo.com/foofoo.php3.
Apache gets the request for foofoo.php3. It knows that .php3 files are handled by the PHP preprocessor, so it tells PHP to deal with it.
foofoo.php3 is a PHP script that contains commands. One of these commands is to open a connection to a database and grab some data. PHP knows how to talk to the database, so it does its thing.
The data comes back from the database, and foofoo.php3 does something to format the data. Typically this would be to make it look pretty before formatting it into HTML.
The HTML goes back to Apache.
Apache sends this back to John Doe's browser, as the response to his request. John Doe now sees a pretty web page containing some information from a database.
Again, that's not 100% correct but it's enough to understand what goes on :). Now that we have a basic understanding of what we are trying to accomplish, let's get on to installing the software. | <urn:uuid:ca4060bd-d76c-488e-9ac5-577fe578a060> | 3.046875 | 606 | Tutorial | Software Dev. | 70.459576 |
This illustration demonstrates the charge separation that goes on within a thunderstorm which leads to lightning. Strong updrafts within the thunderstorm force moisture into colder portions of the atmosphere where supercooled water droplets, graupel (like snow pellets or small hail), and ice crystals form. What happens next is still being studied by scientists, but it is believed that when the ice crystals and graupel collide, electrons are transferred from the ice crystals to the graupel (the same process that charges your body when you walk across carpet or rub a balloon on your head). This gives the ice crystals a positive charge, and the graupel becomes negatively charged. The heavier graupel and water droplets become concentrated at the bottom of the cloud, while the lighter ice crystals are kept higher up by the storm's updraft. This produces a charge separation within the cloud. Additionally, the negatively-charged cloud base repels electrons at the earth's surface, and the ground becomes slightly positively charged. This electric field results in an electrical discharge (lightning). This can be within the cloud or from the cloud to the ground. | <urn:uuid:22f223d6-5b14-4f25-9b20-bd43dd0fb03a> | 3.90625 | 228 | Knowledge Article | Science & Tech. | 40.764785 |
Lead scientist Amber Straughn and observatory manager Paul Geithner answer questions during James Webb Space Telescope Night at the NASA Goddard Visitor Center on August 26, 2010.
Photo Credit: NASA Goddard Space Flight Center/Bill Hrybyk (Click image for full size.)
On a small farm in the Middle of Nowhere, Arkansas, the sky was beautiful at night. Looking up at all those stars is how I became interested in astronomy as a child. Later on, Hubble began to release its beautiful images, which made me start asking those big science questions, such as, “How are those stars formed? How did we get here? What all is out there?” Years later, I’m able to study some of these intriguing questions thanks to my work at NASA.
I first got hands-on experience with Hubble during my graduate studies several years ago, when I used data from its ultra-deep field as part of my dissertation work at Arizona State University. Later, I was able to work with Hubble’s wide-field camera 3, which was installed during the last servicing mission in 2009. With that instrument and several others, we gave Hubble new eyes, extending its capability into the near infrared and also the ultraviolet. This allowed us to look at the universe in greater detail and learn more about the universe around us.
Although Hubble’s new instruments extend its capability into the near infrared, in order to push the boundaries and answer the biggest astronomy questions of our day, we need a much larger telescope that also extends into the mid-infrared. Not only does this help us peer through dust, as in the case of newborn stars inside their dusty cocoons, but it also gives us a better view of distant galaxies.
For example, when we look at ultra-deep-field images from Hubble, we find the most distant galaxies in those images are tiny red dots. The light we receive from these distant galaxies has been shifted to longer wavelengths by the expansion of the universe—the more distant, the redder their light. In order to see them, we need to see light that is redder, and that’s exactly what infrared light is. That’s one of the big reasons the James Webb Space Telescope (JWST) was designed to be an infrared telescope: it will detect the very first galaxies to be born in the early universe.
Technicians and scientists check out one of the Webb telescope’s flight mirrors in the clean room at Goddard Space Flight Center. Wavefront-sensing technology was used to measure the shape of each mirror and has spun off into ophthalmology, where it has been used to more perfectly measure the topography of the human eye.
Photo Credit: NASA/Chris Gunn (Click image for full size.)
In addition to improving our vision of these distant galaxies and learning more about how stars form, JWST will also reveal more about how galaxies assemble over time and expand our study of exoplanets—planets orbiting other stars outside our solar system. With this, JWST will study every phase of our universe: from the very first galaxies to form more than 13 billion years ago to the very recent formation of planets that could be capable of supporting life. JWST will observe the universe near its distant edge, and also in our own “backyard” as it helps us learn more about objects within our own solar system.
Succeeding in building this new telescope is only part of our mission—of any NASA mission. Another important component of what we do is outreach, telling people what we’re doing and why.
Since what we do at NASA involves complex engineering of one-of-a-kind missions, explaining the intricacies of what we do in a way that’s easy to understand is important not only to maintain support for the mission, but also to engage people in what we’re doing.
To engage an audience, first they have to be interested in what you have to say. One of the great things about astronomy is it’s something the public is interested in and captivated by. The sky is beautiful; the images we get back from Hubble are inspiring and appeal to the public. Astronomy is a good starting point for getting the public interested in science and technology in general. And once you have that entry point, it’s easier to expand upon the engineering required to build these big missions and do the great things NASA does.
Finding time and budget to communicate frequently can be a challenge, but it’s so important and rewarding. The Science Mission Directorate requires a minimum of 1 percent of all mission funding go to education and public outreach.
Kids and adults alike are drawn in by the captivating images from Hubble, Spitzer, and all the other space telescopes, as well as the cutting-edge technology that goes into building them. Additionally, discussing spin-offs of our technology that apply to their everyday lives helps keep them engaged.
One of the really cool examples of technology spin-off with JWST involves the way we ensure the mirrors are perfect. We used a technology called wavefront sensing to measure the shape of each mirror, and this technology has spun off into the medical field of ophthalmology. Ophthalmologists have used it to more perfectly measure the topography of the human eye.
Behind-the-scenes photo from the filming of the”Hubble Gotchu!” segment from Late Night with Jimmy Fallon.
Photo Credit: NASA/Maggie Masetti (Click image for full size.)
Another spin-off example involves JWST’s cryogenic application-specific integrated circuits (ASICs). ASICs are very small and can contain an entire circuit board’s worth of electronics. These circuits were installed on Hubble as part of its advanced camera for surveys, and JWST’s investments enabled these circuits to be programmable, which was important when the camera needed to be repaired. This became a case of “future heritage,” where a program in development invents a technology for a program well into operations.
And those are just two examples of spin-offs that come from the big, bold research-and-development efforts that go into building our huge missions. There are thousands more.
These are ways to structure successful outreach communication, but I think the most important thing is to be enthusiastic about what we’re sharing with the public. Excitement is contagious, and I truly love my job. Ever since I looked up at those Arkansas skies I wanted to be involved with studying the universe, and I find sharing my personal story is a great way to convey my enthusiasm for what we do. It’s also a great way to engage students, showing them one path into space exploration. It’s important for the future of our country to get kids interested and educated in science, technology, engineering, and math—and on the path to making new discoveries in the future.
One question I often get about JWST specifically is why it looks the way it does. Indeed, it is an odd-looking telescope. One generally thinks of tubes and circular mirrors when they envision a telescope—Hubble is of this design, of course. But the answer to that question is we are building it to function optimally for what it’s designed to do: observe in the infrared. Because of this, its mirrors and instruments have to be shielded from the sun (hence the tennis-court-sized sunshield). People are always fascinated by the design of this observatory.
Finding time and budget to communicate frequently can be a challenge, but it’s so important and rewarding. The Science Mission Directorate requires a minimum of 1 percent of all mission funding go to education and public outreach. It’s a good structure because it allows us to do the great things that get the mission science out not only to students and teachers but also the general public. Creating stunning visuals is one aspect of that. We have a team here at Goddard Space Flight Center who put together stunning visuals, videos, and imagery to go along with the story of the science, which really helps draw in the audience and communicate the science on a deeper level.
NASA Astrophysicist Amber Straughn demonstrates the cold environment where the Webb telescope will be by dipping flexible rubber surgical tubing into liquid nitrogen in a demonstration video.
Photo Credit: NASA (Click image for full size.)
Social media has become another of the primary means by which we communicate news, and we have a great team here at Goddard that ensures we are on the cutting edge of new media and new communication.
I’m so glad that part of my official mission duties include communication and outreach. I’ve been fortunate to be involved in some cool, quirky things. We filmed with a crew from Late Night with Jimmy Fallon a couple years ago for their “Hubble Gotchu!” segment. They were here all day, and we got to do a funny rap video about NASA that aired on the show. That got a lot of attention and response, and it was a fun and positive experience overall.
These are only a few examples of how to engage others in what we do at NASA. It’s important to do because our missions wouldn’t exist without support and interest from the community. And it helps engage the next generation so they can continue exploring wherever we leave off. Who knows what JWST will teach us along the way, and where we’ll go as a result of what we learn? The only thing we can be sure of is we will need future explorers to take us there. But making sure they’re involved to ask the next big questions of tomorrow takes communication today.
Amber Straughn is a research astrophysicist in the Observational Cosmology Laboratory at Goddard Space Flight Center and serves as the deputy project scientist for James Webb Space Telescope education and public outreach. | <urn:uuid:056517b5-4491-4ed2-8c49-c9b027bc451a> | 3.28125 | 2,055 | Audio Transcript | Science & Tech. | 45.406065 |
A geologic and oceanographic study of the waters and Continental Shelf of Gulf of the Farallones adjacent to the San Francisco Bay region. The results of the study provide a scientific basis to evaluate and monitor human impact on the marine environment.
Manual for research program on the nesting habits of sea turtles of the Virgin Islands, with descriptions of species, nesting behavior, observation methods, record keeping, tagging, and tissue sample collection. (PDF file, 121 pp.)
Changes in both the ocean and coastal ecosystems may have negative effects on sea otter populations in the coastal Northwest and Alaska. A study underway will examine these factors and the overall health of sea otter populations.
Report with mini-movie and photos on the hypothesis that the atmospheric transport of dust arising from the desertification in northern Africa led to algal infestation of corals, coral diseases, and the near extinction of associated sea urchins.
Shows how coral reef specimens are collected, the type of information gained from them, and the methods by which they are measured and studied to understand recent (past few centuries) changes in climate.
By measuring the current and historical growth rates of coral skeletons, and using field experiments, we intend to find out whether rising atmospheric CO2 and rising sea levels will cause coral reefs to erode and cease to function. | <urn:uuid:3f7024c5-7abe-4b37-85cd-5b6e07add3f7> | 3.34375 | 270 | Content Listing | Science & Tech. | 28.222658 |
How a New Star Looks (Jun, 1935)
How a New Star Looks
WHEN Nova Herculis was announced in the papers, a few days before last Christmas, many people went out to look for it. As a matter of fact, it was a little disappointing as a naked-eye spectacle; it never came up to first magnitude (the smaller the magnitude, the brighter the star. The two brightest stars are below zero in magnitude.) But it was extremely interesting. Astronomers are still watching it through telescopes and spectroscopes.
What does a star look like through a telescope; even a moderate sized one, like that in the photo at the left?
Well, the photo is a bit deceptive. In a good instrument, a star is still only a point of light. The better the telescope, and the better seeing conditions, the smaller the star. Its brightness increases; but not its apparent size. A comet or a planet, on the other hand, can be magnified. In the eastern sky we have the planet Mars and the star Arcturus, in the early evening. They look alike to the eye; but a telescope makes Mars spread out, bigger and bigger, perhaps till it looks as big as the head of a lead pencil. Arcturus remains simply a point of yellow light; because, while Arcturus is millions of miles across, it is trillions of miles away.
Therefore, when we see Nova Herculis in the photograph as a spot about 1/12″ across, we know it is simply because the plate has been fogged a little around the bright star; while the smaller stars—all too small to be seen by the naked eye— produce spots large or small in proportion to their brightness. The longer a plate is left in the camera of a telescope, the larger all the stars appear on it, and the more of the dim ones appear on the plate. Stars a hundred thousand times too dim to be seen by the eye can be photographed with big instruments.
Because of the brightness of these points of light, it is impossible to measure their apparent diameter in a telescope, or on a photograph; but by an instrument called the interferometer, which brings together two images of the same star to form “fringes” of light, it is possible to measure the diameters of some of our largest “near neighbors” when they run into millions of miles. Such figures, roughly, confirm calculations as to the probable sizes of these stars, in order that they may seem as bright to us as they do. They run from about 300,000,000 miles in diameter down. Since Nova Herculis (as explained in our last issue) blew off a great cloud of hot white material, it is hoped that this may continue expanding until we can see it separate from the star—as a “ring nebula,” like a puff of smoke, with the star in the center. Such objects are known in the heavens; but the explosion must get a great many billion miles away from the star before the smoke puff can be seen separately. | <urn:uuid:3b17de2b-a00e-4b17-b3ac-8acbd897d99b> | 4.125 | 635 | Personal Blog | Science & Tech. | 54.93069 |
Space.com: NASA has long planned to mine water on the Moon to supply human colonies and future space exploration. Now the discovery of small amounts of water across much of the lunar surface has shifted that vision into fast-forward, with the US space agency pursuing several promising technologies.
A hydrogen reduction plant and lunar rover prospectors have already passed field tests on Hawaii’s volcanic soil, and more radical microwave technology is being evaluated.
“You can make back costs fairly quickly [within a year] compared to the launch costs of just throwing tanks of water and oxygen at the moon,” said Gerald Sanders, manager of NASA’s InSitu Resource Utilization Project.
Still, Sanders cautioned that there are big unknowns—how much water the Moon holds, where it is, and how deep will they have to excavate to get to it.
Nature News: An independent report has all but ruled out radioactive contamination from the experiments of physicist Ernest Rutherford as the source of a cluster of deaths at the University of Manchester, UK.
Manchester University deaths not linked to Rutherford radiation The Guardian
BBC News: Engineers hope an early warning system being installed at the Large Hadron Collider could prevent incidents of the kind that shut down the machine last year.
Physics Today: A team of engineers and artists working at the University of Washington’s Solheim Rapid Manufacturing Laboratory has developed a way to create glass objects using a conventional three-dimensional printer and “open-sourced” the technique so anyone can use it.
The team’s method, which it named the Vitraglyphic process, is a follow-up to the Solheim Lab’s success last spring printing with ceramics. (See an example image on the right. Photo credit: University of Washington)
“It became clear that if we could get a material into powder form at about 20 microns we could print just about anything,” said UW professor Mark Ganter.
Three-dimensional printers are used as a cheap, fast way to build prototype parts. In a typical powder-based 3D printing system, a thin layer of powder is spread over a platform and software directs an inkjet printer to deposit droplets of binder solution only where needed. The binder reacts with the powder to bind the particles together and create a 3D object.
Glass powder doesn’t readily absorb liquid, however, so the approach developed for ceramic printing had to be radically altered.
By adjusting the ratio of powder to liquid the team found a way to build solid parts out of powdered glass that fused when heated to the right temperature.
Glass is a material that can be transparent or opaque, but is distinguished as an inorganic material (one which contains no carbon) that solidifies from a molten state without the molecules forming an ordered crystalline structure. As the glass molecules remain in a disordered state, the resulting object is technically a super-cooled liquid rather than a true solid.
“By publishing these recipes without proprietary claims, we hope to encourage further experimentation and innovation within artistic and design communities,” said UW associate professor Duane Storti.
Ronald Rael, an assistant professor of architecture at the University of California, Berkeley, has been working with the Solheim Lab to set up his own 3D printer. Rael is working on new kinds of ceramic bricks that can be used for evaporative cooling systems.
“3D printing in glass has huge potential for changing the thinking about applications of glass in architecture,” Rael said. “Before now, there was no good method of rapid prototyping in glass, so testing designs is an expensive, time-consuming process.” Rael adds that 3D printing allows one to insert different forms of glass to change the performance of the material at specific positions as required by the design.
Science: At the height of the Korean War, a scared 16-year-old boy made a promise as he lay wounded by shrapnel on a battlefield. “I said, ‘God, if you save my life, I will return this love to my enemy,’” recalls Kim Chin-Kyung, who was fighting for the south against the north.
Six decades later, the 74-year-old businessman turned university administrator is keeping his word. Last week, Kim was appointed president of Pyongyang University of Science and Technology (PUST) at a ceremony in Pyongyang to commemorate completion of the $35 million campus, which after 4 years of delays is expected to open in November to the crème de la crème of North Korea’s science graduate students.
NYTimes.com: With a federal plan to handle nuclear waste in deadlocked disarray, the Nuclear Waste Technical Review Board—an advisory panel that has spent 20 years studying a proposed repository at Yucca Mountain—turned Wednesday to discussing ways of reusing the fuel instead.
But as the panel made evident during the meeting, such reuse was uncertain, along with the future of Yucca Mountain.
Earth Island Journal: A recent New York Times article pointedly asked whether NASA climate scientist James Hansen still matters. The subtext to the story was, has Hansen been too vocal and too unconventional in his criticism of Washington’s response to climate change to be taken seriously?
Nell Greenberg interviews Hansen over his recent political action on combating climate change, and how he ended up in climate science in the first place.
NPR: NASA is running out of the special kind of plutonium needed to power deep space probes, worrying planetary scientists who say the US urgently needs to restart production of plutonium-238.
But it’s unclear whether Congress will provide the $30 million that the administration requested earlier this year for the Department of Energy to get a new program going.
NYTimes.com: The modern car is still 60% of steel by weight.
But automotive steel has changed quite a bit since the Ford company’s first Model T rolled off the assembly line in 1908. Metallurgists and manufacturers have learned to manipulate steel’s microstructure through precise control of processing to create sheet steels of increasing strength. Prompted by crash-worthiness requirements and the need to make cars lighter to improve gas mileage, automakers are replacing conventional steels with advanced high-strength ones.
Where once a single grade of steel might have sufficed, the typical “body in white,” as automakers call a car’s basic skeleton, might now be a patchwork of a dozen or more steels of different types and strengths, tailored through computer modeling to handle the stress and strain of normal driving—and of severe crashes.
Nature News: Canada’s Perimeter Institute for Theoretical Physics was intended to become a world leader in the field. Nature‘s Eric Hand finds out if it has lived up to its ambitions. | <urn:uuid:0d189daf-09b9-420b-96ad-2401b5b1f0b8> | 3.890625 | 1,422 | Content Listing | Science & Tech. | 36.801962 |
Polar bears are considered by many to be marine mammals. The name Ursus maritimus means maritime bear. Their preferred habitat is the pack ice of the Arctic Ocean. The ice edge and pressure ridges where fractures and refreezing occur provide the best hunting ground. Bears will travel as much as 1,000 km north and south, as the ice melts and freezes. During summer bears may remain on islands or coastlines with landfast ice, drift on ice flows, or get stranded on land where they are forced to endure warm weather. (DeMaster and Stirling, 1981; Nowak, 1999; Stirling and McEwan, 1975)
Habitat Regions: Polar; Terrestrial; Saltwater or marine
Terrestrial Biomes: Tundra; Icecap
Aquatic Biomes: Coastal
- Nowak, R. 1999. Walker's Mammals of the World. Baltimore and London: The Johns Hopkins University Press.
- DeMaster, D., I. Stirling. 1981. *Ursus maritimus*. Mammalian Species, 145: 1-7.
- Stirling, I., E. McEwan. 1975. The caloric value of whole ringed seals (*Phoca hispida*) in relation to polar bear (*Ursus maritimus*) ecology and hunting behavior. Canadian Journal of Zoology, 53: 1021-1027. | <urn:uuid:463d59d9-c217-49d6-b1b7-bf04b44fc04d> | 3.484375 | 288 | Knowledge Article | Science & Tech. | 58.836591 |
PreparedStatement in Java is one of several ways to execute SQL queries using JDBC API. Java provides Statement,
PreparedStatement and CallableStatement for executing queries. Out of these three, Statement is used for general purpose queries, PreparedStatement is used for executing parametric query and CallableStatement is used for executing Stored Procedures. PreparedStatement is also a popular topic in java interviews. Questions like Difference between Statement and PreparedStatement in Java and How to prevent SQL Injection attacks in Java are popular java interview questions. In this Java JDBC tutorial we will see why should you use use PreparedStatement in Java, What are the major advantages of using PreparedStatement in Java and how PreparedStatement prevents SQL Injection attacks in Java.
This article is in continuation of my earlier post on database and java like 4 tips to improve performance of Java application with database and Difference between truncate and delete in SQL.If you haven’t read them already you may found those tutorial useful and interesting.
What is PreparedStatement in Java
PreparedStatement is a class in java.sql package and allows Java programmer to execute SQL queries by using JDBC package. You can get PreparedStatement object by calling connection.prepareStatement() method.SQL queries passed to this method goes to Database for pre-compilation if JDBC driver supports it. If it doesn't than pre-compilation occurs when you execute prepared queries. Prepared Statement queries are pre-compiled on database and there access plan will be reused to execute further queries which allows them to execute much quicker than normal queries generated by Statement object. Here is an example of how to use PreparedStatement in Java:
In this example of PreparedStatement same query and access path will be used if you pass a different parameter e.g.
"Standard Charted" or "HSBC". ResultSet returned by prepared statement execution is of "TYPE_FORWARD_ONLY" but can be customized by using overloaded method of prepareStatement().
Benefits of Java Prepared Statement
PreparedStatement in Java JDBC offers several benefits and it’s a recommended way to execute SQL queries in any enterprise Java application or in production code. Here are few advantages of using PreparedStatement in Java:
1. PreparedStatement allows you to write dynamic and parametric query.
By using PreparedStatement in Java you can write parametrized sql queries and send different parameters by using same sql queries which is lot better than creating different queries. Here is an example of parametric query written using PreparedStatement in java:
Now you can run this query for any loan type e.g. "personal loan”, "home loan" or "gold loan". This example of SELECT query is called parametric or parametrized query because it can be invoked with different parameter. Here “?” is used as place holder for parameter.
2. PreparedStatement is faster than Statement in Java
One of the major benefits of using PreparedStatement is better performance. PreparedStatement gets pre compiled
In database and there access plan is also cached in database, which allows database to execute parametric query written using prepared statement much faster than normal query because it has less work to do. You should always try to use PreparedStatement in production JDBC code to reduce load on database. In order to get performance benefit its worth noting to use only parametrized version of sql query and not with string concatenation. Out of following two examples of SELECT queries, first example of SELECT query will not offer any performance benefit:
SQL Query 1: PreparedStatement with String concatenation
SQL Query 2: Parameterized query using PreparedStatement
Second SQL query is correct use of PreparedStatement in Java and give better performance than SQL query1.
3. PreparedStatement prevents SQL Injection attacks in Java
If you have been working in Java web application you must be familiar with infamous SQL Injection attacks, last year Sony got victim of SQL injection and compromised several Sony play station user data. In SQL Injection attack, malicious user pass SQL meta-data combined with input which allowed them to execute sql query of there choice, If not validated or prevented before sending query to database. By using parametric queries and PreparedStatement you prevent many forms of SQL injection because all the parameters passed as part of place-holder will be escaped automatically by JDBC Driver. Though It’s worth remembering that in above example of two PreparedStatement only second example will prevent SQL injection attacks and first example is not secure with SQL injection.
4. At last PreparedStatement queries are more readable and secure than cluttered string concatenated queries.
Limitation of Java PreparedStatement
Despite of being very useful PreparedStatement also has few limitations:
1. In order to prevent SQL Injection attacks in Java, PreparedStatement doesn't allow multiple values for one placeholder (?) who makes it tricky to execute SQL query with IN clause. Following example of SQL query with IN clause using prepared Statement will not work in Java:
Though there are some workarounds and ways to execute IN queries using PreparedStatement but those are
rather tricky or have performance impact.
Important points on PreparedStatement in Java
Here are few important points about PreparedStatement Class in Java, worth remembering:
1. PreparedStatement in Java allows you to write parametrized query which gives better performance than Statement class in Java.
2. In case of PreparedStatement, Database use an already compiled and defined access plan, this allows prepared statement query to run faster than normal query.
3. Parametrized query written using PreparedStatement in Java prevents many common SQL Injection attacks.
4. PreparedStatement allows you to write dynamic query in Java.
5. PreparedStatement are associated with java.sql.Connection object, once you drop a connection all PreparedStatement associated with that connection will be dropped by Database.
6. "?" is also called placeholder or IN parameter in Java.
7. PreparedStatement query return FORWARD_ONLY ResultSet, so you can only move in one direction Also concurrency level of ResultSet would be "CONCUR_READ_ONLY".
8. All JDBC Driver doesn't support pre compilation of SQL query in that case query is not sent to database when you call prepareStatement(..) method instead they would be sent to database when you execute PreparedStatement query.
9. Index of placeholder or parameter starts with "1" and not with "0", which is common cause of . So in a PreparedStatement t of two placeholder, first will be referred by index 1 and second will be reference by index 2.
These were the reasons Why PreparedStatement in java is very popular and useful. You can still use Statement object for test programmers but consider PreparedStatement before moving to production.
Other Java tutorials you may like | <urn:uuid:515dfe0c-ced6-4bfc-936f-9c440b9355ef> | 3.109375 | 1,437 | Tutorial | Software Dev. | 26.142544 |
JSON is a lightweight, text-based data interchange format that is used to serialize structured data for transmission over networks. It has three primitive data types: string, number, and Boolean. It has two data structures: array and object. An array is an ordered collection of values, where the value can be a JSON primitive, object or array. An object is an unordered set of key/value pairs. The key is a string and the value, as with the array, can be a JSON primitive, object, or array.
In this documentation, the serialized textual representation of JSON is referred to as “text-based JSON” to distinguish it from the deserialized representation of JSON as a Common Language Runtime (CLR) type, which is referred to here as a “JSON CLR type” or as a “JSON CLR object” if we are referring to an instance of the type.
JSON CLR types represent the two text-based structured types with JsonArray and JsonObject. A JsonArray is an ordered sequence of zero or more JsonValue objects. A JsonValue is the JSON CLR representation of a JSON text-based value, which can be either a primitive or structured type. A JsonObject is an unordered collection of zero or more String/JsonValue pairs, which represent the key/value pairs of the text-based JSON object.
|JsonArray||A JsonArray is an ordered sequence of zero or more JsonValue objects.|
|JsonObject||A JsonObject is an unordered collection of zero or more key/value pairs.| | <urn:uuid:3e524ffc-2e92-4bb7-a238-c0fa0a490f2b> | 3.96875 | 338 | Documentation | Software Dev. | 44.404113 |
I have two stars, both of which have Balmer lines at the same wavelength positions.
Why does this pattern exist?
Assuming by "depths of the Balmer lines" you mean how broad they are, this information can be used to determine the (surface) temperature of the star1. In particular, and that may be the only thing the homework question is about, the star with the broader Balmer lines have the higher surface temperature.
The thermal Doppler broadening (not Doppler shift) is correlated with temperature and depends on three factors:
The first factor is the same for any particular Balmer line, and the second factor is the same as the Balmer lines are all from emissions from hydrogen. Thus, in this case, the broadening only depends on temperature (assuming thermal Doppler broadening is the only effect).
1. Spectral linewidth - "In astronomy and plasma physics, the thermal Doppler broadening is one of the explanations for the broadening of spectral lines, and as such gives an indication for the temperature of observed material."
I'm going to obfuscate here to avoid directly answering the question!
Well it begins with an assumption that physics is the same throughout the universe, which seems pretty fair to me. Given that physics is the same throughout then we can expect phenomena that look similar to have similar causes. This can be a trap and isn't perfect reasoning but it applies in your question... | <urn:uuid:d0c8c7b9-a17f-4f68-b365-3229d9dd52bd> | 3.75 | 299 | Q&A Forum | Science & Tech. | 45.976695 |
The concept of mass is one of the most fundamental notions in physics, comparable in importance only to those of space and time. But in contrast to the latter, which are the subject of innumerable physical and philosophical studies, the concept of mass has been but rarely investigated. Here Max Jammer, a leading philosopher and historian of physics, provides a concise but comprehensive, coherent, and self-contained study of the concept of mass as it is defined, interpreted, and applied in contemporary physics and as it is critically examined in the modern philosophy of science. With its focus on theories proposed after the mid-1950s, the book is the first of its kind, covering the most recent experimental and theoretical investigations into the nature of mass and its role in modern physics, from the realm of elementary particles to the cosmology of galaxies.
The book begins with an analysis of the persistent difficulties of defining inertial mass in a noncircular manner and discusses the related question of whether mass is an observational or a theoretical concept. It then studies the notion of mass in special relativity and the delicate problem of whether the relativistic rest mass is the only legitimate notion of mass and whether it is identical with the classical (Newtonian) mass. This is followed by a critical analysis of the different derivations of the famous mass-energy relationship E = mc2 and its conflicting interpretations. Jammer then devotes a chapter to the distinction between inertial and gravitational mass and to the various versions of the so-called equivalence principle with which Newton initiated his Principia but which also became the starting point of Einstein's general relativity, which supersedes Newtonian physics. The book concludes with a presentation of recently proposed global and local dynamical theories of the origin and nature of mass.
Destined to become a much-consulted reference for philosophers and physicists, this book is also written for the nonprofessional general reader interested in the foundations of physics.
"The book reads likes an engaging, well-planned lecture, with many a historical aside and opinionated excursion."--Publishers Weekly
"A valuable and badly needed account that manages to be undogmatic, comprehensive and accessible. . . . I can strongly recommend this beautifully written and accessible book."--Andrew Pinsent, Physics World
"An interesting and stimulating mix of physics and philosophical issues. . .Jammer has produced a fascinating look into the nature of a quantity that most of us take for granted . . . and its also fun to read."--Barry R. Holstein, American Scientist
"[Jammer's] contributions to the conceptual foundations of physics have been, and continue to be, both fruitful and enlightening."--Jonathan Bain, Physics Today
"Concepts of Mass in Contemporary Physics and Philosophy addresses an important issue, covering a large swathe of territory and presenting technical results in clear and accessible way. There is no comparable study of mass in the field, and the need for a synoptic review is obvious. Philosophers and historians of science, who often lack the technical expertise to evaluate the work of physicists, will find the book very useful. Physicists, too, will value the book, particularly because it brings together results that are widely dispersed in the literature."--Tim Maudlin, Rutgers University
"Professor Max Jammer's book is a significant and important contribution to the conceptual foundations of physics, especially in the manner in which it explores how the concept of mass occurs in the context of gravitational and space-time theories."--Ronald Anderson, Boston College
Table of Contents:
CHAPTER 1 Inertial Mass 5
CHAPTER 2 Relativistic Mass 41
CHAPTER 3 The Mass-Energy Relation 62
CHAPTER 4 Gravitational Mass and the Principle of Equivalence 90
CHAPTER 5 The Nature of Mass 143
Another Princeton book authored or coauthored by Max Jammer: | <urn:uuid:d46147ec-a55c-400f-b9f8-e3e4d024839c> | 2.734375 | 786 | Knowledge Article | Science & Tech. | 26.927644 |
Science subject and location tags
Articles, documents and multimedia from ABC Science
Friday, 26 April 2013
A bizarre stellar system made up of two dead stars 7000 light-years away has put Einstein's famous general theory of relativity under its most extreme test yet.
Wednesday, 16 January 2013
Russia will resume a long-dormant quest to explore the Moon by sending an unmanned probe to our closest neighbour.
Friday, 2 November 2012
The first solids to form in our solar system appeared at the same time, more than 4.5 billion years ago, according to a new study.
Thursday, 27 September 2012
Astronomers are monitoring a newly discovered comet, which is expected to put on a spectacular sky show next year.
Friday, 22 June 2012
The Arctic went through ice-free periods of extreme warmth over the past 2.8 million years.
Wednesday, 22 February 2012
Russian scientists have grown flowering plants using seeds stored by squirrels 30,000 years ago.
Wednesday, 16 November 2011
Concerns about a crippled Russian spaceship crashing back to Earth with a load of toxic fuel aboard have been played down by an Australian engineer.
Tuesday, 8 November 2011
Ancient cave painters who drew spotted horses were depicting what they saw around them and were not, as often believed, being abstract or symbolic, suggests a new study.
Tuesday, 26 July 2011
Last year's Nobel winning physicists have devised ways of studying graphene at the fundamental level of the electron.
Friday, 13 May 2011
A Neanderthal-style toolkit found in the frigid far north of Russia may mark the last refuge of Neanderthals before they became extinct.
Wednesday, 13 April 2011
Planets, maybe even advanced life, could theoretically exist inside a black hole according to a new theory.
Thursday, 24 March 2011
Scientists are planning to drill through the Earth's crust to retrieve a sample of mantle.
Monday, 7 February 2011
Russian scientists are on the brink of piercing through to the secrets of an icebound lake which has been sealed deep beneath Antarctica's frozen crust for 15 million years.
Tuesday, 18 January 2011
Japanese researchers plan to resurrect the long-extinct mammoth by using cloning technology to bring the ancient pachyderm back to life in around five years time, according to a report.
Monday, 11 October 2010
The long lost lunar rover Lunokhod 1, has been rediscovered by astronomers using laser pulses, thirty-six years after it disappeared. | <urn:uuid:0e12a322-990c-4ef4-95fe-b58fc4b849ca> | 2.96875 | 513 | Content Listing | Science & Tech. | 49.91849 |
Simply begin typing or use the editing tools above to add to this article.
Once you are finished and click submit, your modifications will be sent to our editors for review.
...is an integer greater than 2), they have two fewer hydrogen atoms than an alkane with the same number of carbon atoms. Cyclopropane (C3H6) is the smallest cycloalkane, whereas cyclohexane (C6H12) is the most studied, best understood, and most important. It is customary to represent cycloalkane rings as polygons, with the understanding that each corner...
Ring compounds often have a particularly rich set of conformational isomers. By far the most interesting of the ring compounds is cyclohexane (C6H12), shown here with cyclopropane (C3H6).
A structural feature especially common among isoprenoid compounds is a ring of six carbon atoms; the simplest compound possessing this structure is cyclohexane (not an isoprenoid), represented by structural formula 1, by a condensed version 2, or simply by the hexagon 3. In compounds of this kind, the six ring atoms are not coplanar, but the ring usually is puckered, as shown in 4 and 5.
...the carbon chain can develop branches or form cyclic structures. A very common ring structure contains six carbon atoms in a ring, each bonded in a tetrahedral arrangement, as in the hydrocarbon cyclohexane, C6H12. Such ring structures are often very simply represented as regular polygons in which each apex represents a carbon atom, and the hydrogen atoms that complete...
What made you want to look up "cyclohexane"? Please share what surprised you most... | <urn:uuid:8b3643ae-3c14-4e18-930b-3f1ffc0f5c56> | 3.65625 | 363 | Knowledge Article | Science & Tech. | 47.82151 |
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The biological significance of pteridine compounds (from Greek pteron, “wing”) has become apparent since the first known members of the group were discovered as pigments of butterfly wings. One example is the yellow pigment 2-amino-4,6- pteridinedione (xanthopterin).
relation to pyrazine
Other members of the pyrazine family are pteridines, alloxazines, and phenazines. Certain pigments, first isolated from butterfly wings in 1891, are pteridines, as are the folic acids, which participate in a variety of essential chemical reactions in the body. Riboflavin (vitamin B2), a growth-promoting factor, is an alloxazine compound. Among the large group of phenazine dyes, the...
What made you want to look up "pteridine"? Please share what surprised you most... | <urn:uuid:37ada656-e0ac-4451-9547-02337ce27c15> | 3.59375 | 226 | Knowledge Article | Science & Tech. | 35.162329 |
'Mesoscale Convective' System
Yet heerein will I imitate the Sunne
Who doth permit the base contagious cloudes
To smother vp his Beauty from the world...
William Shakespeare, "Henry the Fourth", Actus Primus, Scaena Secunda.
Type "Mesoscale Convective system" looks on satellite images as a circle,
an oval, sometimes disorderly, but always compact.
It can be emerged
This is spreading type.
To the "Mesoscale Convective system" belong also "Cloud Clusters", "Squall Lines" and mainly the "Circular Cloud Areas", which are accompanied with a Hurricane or a Typhoon. The last one will be described in the separate article.
The structures of this type will observed also over the land between the latitudes of 40°N and 40°S.
If warm air rises above the cooler one, it begins to cool
down and the water vapour condenses as water droplets. This condensation
causes the heating of surrounding air and thus the continuation of its
| Glob. occr. diagram
of 'Mesoscale Convective' System
Microscale Meteorology Scientific Highlights | <urn:uuid:6ae95bb9-93a6-4b55-adc2-75eef52316bd> | 2.859375 | 257 | Knowledge Article | Science & Tech. | 39.076944 |
Brook Snaketail Dragonfly
The beautiful brook snaketail dragonfly is listed as a species of special concern in New Jersey.
The beautiful brook snaketail dragonfly (Ophiogomphus aspersus) is listed as a species of special concern in New Jersey. A Threatened status listing has been proposed by the Endangered and Nongame Species Advisory Committee; however, no formal rule proposal has been filed to date.
In what is hoped will be the first of many articles about odonates (dragonflies and damselflies), I would like to highlight the beautiful brook snaketail dragonfly (Ophiogomphus aspersus). The Latin root Ophio means snake-like or serpent, hence the very appropriate common name applied to this group. The snaketails were given this name because males have sinuous or snake-like claspers at the end of the abdomen which are used during mating.
Snaketail adults usually emerge from rivers and streams from late May to early June in New Jersey. They are generally active through mid-June though stragglers have been observed into August. Five species of this group have been reported in our state although one has not been observed since the early 20th century. These are among the most environmentally sensitive dragonflies in North American and as such are outstanding indicators of water quality and overall watershed health.
Snaketails belong to the greater clubtail family (the Gomphids). All clubtails have widely spaced eyes that do not touch at any point. Most have a widening at the tip of the abdomen, also called a club. While most clubtails have simple patterns or dull coloration, the snaketails are mostly bright green. Other color patterns vary subtly, but they are stunning insects and among our most beautiful dragonflies. The majority of clubtails inhabit rivers and streams.
Many North American species are declining or are severely imperiled due to water quality degradation. Toxic run-off, siltation from erosion and the construction of dams are among the greatest threats facing clubtails and other odonates. The snaketails are generally the most sensitive to any environmental changes. Even minor increases in the silt or mud content in streams can alter dissolved oxygen levels and harm or kill snaketail larvae. Like most odonates, snaketails also need undisturbed fields and wooded uplands adjacent to breeding waters. It is here that critical foraging and breeding occurs. This habitat also provides vital shelter for fragile newly emerged adults during severe weather events and protects them from predators.
Toxic run-off, siltation from erosion and the construction of dams are among the greatest threats facing clubtails and other odonates.
Of the four snaketail species known to breed here, the rarest is the brook snaketail. The first New Jersey colony was not discovered until 1986 in the Whippany River watershed in Morris County. Since then, an additional four colonies have been found in the Skylands and Ridge and Valley regions. This highly localized species also inhabits small segments of the Musconetcong, Wallkill and Flat Brook watersheds.
The brook snaketail has very specific habitat requirements while the other three related species are slightly more elastic. This species inhabits clean, relatively quiet or slow moving streams with an abundance of sandy sediments. It shares this habitat requirement with the federally endangered dwarf wedgemussel and co-exists with it at two locations in New Jersey. It is often associated with the harpoon clubtail (Gomphus descriptus) and river jewelwing (Calopteryx aequabilis). The individual populations of brook snaketail in New Jersey are referred to as colonies due to the limited amount of appropriate habitat in our area. Unlike more common or generalized species, breeding is restricted to relatively small sections of the rivers and streams they inhabit.
Due to the many challenges facing this species, and the small size of the five known colonies, the brook snaketail has been proposed as a threatened species in New Jersey. This species will be carefully monitored to ascertain whether its status is changing. Further colonies are also being sought, particularly in the Ridge and Valley region. A study will be undertaken next year that will hopefully quantify the actual distance from breeding streams that this species travels while foraging. This information will eventually allow for the establishment of effective protective buffers around known brook snaketail colonies and their critical habitat areas.
written by Allen Barlow
Find Related Info: Invertebrates | <urn:uuid:ffd4b0a7-2440-4429-96f3-33d32520ce13> | 3.046875 | 952 | Knowledge Article | Science & Tech. | 30.553554 |
Using GIS Mapping to Examine Influence of Forest and Box Spacing on Bluebird Nesting Success
In this project I was using GIS mapping to examine the effect of 2 environmental variables on the success of bluebird boxes on Wye Island. I monitored 50 boxes this year and used the mapping to see what effect forest proximity and box spacing had on bluebird nesting success.
In order to find a solution to this problem I had to do various things. One thing I had to do was I had to check the fifty bluebird boxes. This took the whole summer to do. I checked them at a pretty consistent rate, which was one time every three four weeks. I then used the GPS and plotted the location of all the fifty boxes and used ArcView to get all my data arranged on the maps.
Relationship to Forest
The successful and unsuccessful bird boxes all had a different relationship to the forest. In our background information it stated that a bird's ideal habitat would be in fields and orchards. From this information I hypothesized that boxes near the forest would be unsuccessful.
From the data collected I found most unsuccessful bird boxes were less than about 200 meters away from the forest. I also found that successful boxes were all over 200 meters away. Some reasons I think bird boxes closer than 200 meters were unsuccessful are there are many predators that live in the forest and less protection.
Relationship to Other Boxes
Territory size had large impact on the success of the boxes. My background information states that most bluebirds like their boxes to be at least 300 feet (91 meters) away. My background information also says that around breeding season the birds expect to have 2-3 acres to themselves and are very territorial which is a reason that successful bird boxes were so far away from each other. Therefore I hypothesized that boxes less than 300 feet would be unsuccessful.
From the data I collected I found that bird boxes that were successful were generally about 200 feet (60 meters) and farther from other boxes. Therefore my hypothesis was significantly close to the data gathered.
If I were to do this project again I would change some things. On thing I would change is instead of having a project I would control an experiment. I would put ten boxes near the forest and I would put ten boxes in an open field area. I would then see which group was more successful. I would also replace the missing boxes and put them in area that were successful this year.
- Does the environment surrounding bluebird boxes effect how successful the boxes are? Specifically in this investigation does the distance from the forest affect the success of bluebird boxes?
- Does the distance between bluebird boxes affect the success of bluebird boxes?
The Bluebird that appears more often throughout the Eastern United States is the Eastern Bluebird. You may know them as Blue Robin, Blue Redbreast, American Bluebird or Red-Breasted Bluebird. It's all the same species. | <urn:uuid:ed19b30e-5495-4868-86c4-c6135126a004> | 3.296875 | 601 | Personal Blog | Science & Tech. | 53.688621 |
Sharing and Accessing Biodiversity Data Globally
Clicking on the Online Mapping link from the CBIF portal sends the user to a page with three links. The first link allows a user without specialized GIS knowledge to use the global index via WMS as just described. The second link leads to the Generic Point Mapper. With this tool, anyone can generate a dynamic map with typical functionality such as zooming and re-centering. Users can access this tool to build such maps for their own Web sites. The third link lets programmers and developers who do have specialized GIS knowledge add GBIF species occurrence layers to other online GIS applications and access the actual WMS that underlies the Map GBIF Occurrence Data service.
Similar mapping services are provided by other sites, but these sites do not currently use data from the GBIF central data portal. Berkeley mapper works against those DiGIR providers that belong to the MaNIS and HerpNet networks. Centro de Referência em Informação Ambiental (CRIA) in Campinas, Brazil, offers a wide suite of geographic and other data quality checking services for the Brazilian data providers in the SpeciesLink network.
Becoming a GBIF Data Provider
It is important to understand that GBIF is not just a secretariat based in Copenhagen or just a data portal. GBIF is all the institutions, corporations, and individuals whose countries or organizations have signed the Memorandum of Understanding that mandates GBIF. In so doing, they have expressed their willingness to openly share biodiversity data, in the spirit of important initiatives, such as the Conservation Commons, that highlight the importance of open sharing of data for societal and scientific benefit.
The GBIF data sharing agreement upholds the principles of sharing biodiversity data openly for common benefit. It is only through the combined efforts of the owners of this data can some of the most burning environmental questions be answered and new scientific discoveries made. Sharing data is a scientific responsibility of all taxonomists, observer networks, and environmental surveys.
Becoming a GBIF data provider is easy and, in many cases, will not take more than a few hours. It includes a few steps that are explained on the GBIF Web site (www.gbif.org/DataProviders/HowTo). The technical tasks consist of downloading and configuring the BioCASE- or DiGIR-based data provider software. There are three integrated packages for Windows and Linux that install in minutes and are supported through a central help desk and documentation. These packages have been put together from open source components. GBIF naturally provides these packages as well as central Web services and registry for free enabling and facilitating open sharing by data holders.
Future Steps and Conclusions
GBIF will soon add a few more data types, going beyond primary data. There will be data provider tools for names and checklists. Species home pages that include digital images are mushrooming on the Internet. Linking to these will add value to shared primary data. Images can be shared by BioCASE/ABCD providers, but extending that capability to all data providers is an important extension to the Darwin Core currently under development. Interfaces for accessing GBIF portals and data providers directly from GIS software tools will also soon be available. The new TAPIR provider will have an Open Geospatial Consortium (OGC) Web Feature Service (WFS). These interfaces can be registered in the UDDI registry as additional alternate bindings.
Recently, GBIF experimented with slicing its global index by country. For instance, a slice of all data from Madagascar was used for a geographic demonstration put together by Conservation International. GBIF is in the process of installing mirror sites for its central data portal in Germany, Korea, and the United States. There will probably also be specialized service providers that use these mirror sites' interfaces. The experience of the CBIF WMS site has been so positive that other similar services can now be encouraged and standard mechanisms for building such value-adding services will have to be established. The data quality assurance services of CRIA and SpeciesLink are examples of what can be achieved. Under an agreement between CRIA and GBIF, some of these services are also being modified for the GBIF data portal.
In closing, it should be emphasized that the GBIF data portal does not intend to be all things for all users. The open interfaces of the GBIF UDDI registry mean that anyone can build portals that access GBIF registered data providers. Some specialized communities have already taken advantage of this such as the Lifemapper project that made use of this open availability. For more information, contact
Deputy Director for Informatics
Peterson, A. T. 2001. "Predicting Species' Geographic Distributions Based on Ecological Niche Modeling." Condor, 103:599-605.
Peterson, A. T., M. A. Ortega-Huerta, J. Bartley, V. Sanchez-Cordero, J. Soberon, R. H. Buddemeier, and D. R. B. Stockwell. 2002. "Future Projections for Mexican Faunas Under Global Climate Change Scenarios." Nature, 416:626-629.
Soberón, J., and A. T. Peterson. 2004. "Biodiversity Informatics: Managing and Applying Primary Biodiversity Data." Philosophical Transactions of the Royal Society of London B, 359:689-698.
Guy Baillargeon, Derek Munro, and Françoise Guilbault of the Canadian Biodiversity Information Facility built the dynamic Web mapping service and contributed text to this article. Johan Duflost, Patricia Mergen, and Frédéric Wautelet of the Belgian Biodiversity Information Facility built the Belgian mapping service. Donald Hobern, Meredith Lane, and Larry Speers of the GBIF Secretariat contributed text, reviewed this article, and improved the language. Thanks to them all.
About the Author
Hannu Saarenmaa has served as the deputy director for informatics of the GBIF since August 2002. He is responsible for the overall strategy, planning, budget, and integration of the informatics aspects of GBIF. Prior to his work at GBIF, he was the project manager for information technology at the European Environment Agency (EEA) where he was instrumental in developing the overall information infrastructure for EEA and the European Environment Information and Observation Network (EIONET), a network that connects environment ministries and agencies in all European Union and accession countries. Between 1978 and 1994, Saarenmaa held various research positions at the Finnish Forest Research Institute. He received a doctorate in applied zoology from the University of Helsinki. The majority of his approximately 190 publications have dealt with the intersection of information technology and ecological sciences. An avid lepidopterologist since 1966, his collection database today includes more than 40,000 records and 300,000 observed specimens.
Reference Web Resources | <urn:uuid:b1cbd68c-f190-48f9-b6eb-d516cadb5fd7> | 2.859375 | 1,468 | Knowledge Article | Science & Tech. | 33.754449 |
Named Parameters in Hibernate Query
There is two types of query parameters binding in the Hibernate Query. One is positioned parameter and another one is named parameter. But, hibernate recommend to use the named parameters since it is more flexible and powerful compare to the positioned parameter. Here we will look into the named parameter type in detail.
Named parameters are as name itself suggests, the query string will be using the parameters in the variable name. That can be replaced at runtime and one advantage of using named parameter is, the same named parameter can be used many times in the same query.
1 2 3 4 5
String queryStr = "from Student s where s.name like :searchName"; List result = session.createQuery(queryStr) .setString("searchName",searchNameValue) .list; </code>
In the above code “:searchName” is the named parameter and it is dynamically added to the query string.
Another good feature is using the named query instead of writing the SQL queries every where. In the named query,all the queries are written inside the .hbm files. Each query is associated with a unique name. Application can load the query by using the name of that query. It avoids writing queries inside the java code itself. The method getNamedQuery() is used for retrieving the query from the mapping file.
1 2 3
session.getNamedQuery("findStudentByName") .setString("searchName",searchNameValue) .list();
1 2 3
<query name="findStudenetbyName"><![CDATA[ from Student s where s.name like :searchName ]]></query> | <urn:uuid:cfb27d76-4472-4a02-bf68-670d1c9e9e28> | 3.09375 | 356 | Tutorial | Software Dev. | 38.655699 |
What kind of language is Java? I've heard various phrases tossed around, like "object oriented," etc. And, as a low-level programmer highly proficient in something like Axe, would it be easy or hard to pick up?
It's easy to pick up if you have experience in other OOP languages.
Object Oriented Programming is like:
str1 = "hey"
a = str1.length()
#a = 3
The upper code is python, but OOP is when you access object properties.
A property of a string can be its length, it's number of words, it's position (GUI), it's size (GUI).
Objects have an enormous number of properties and methods.
Take a look at this Java method:
JButton button = new JButton(); //This creates a button
button.setVisible(true); // setVisible() is a method, and I set it to true in order to show the button
Explaining OOP is hard, here's a Python example:
a = "hello"
print len(a) # This is non-OOP
print a.__length__ #This is OOP
This last example is what made me understand OOP, I'll never forget it.
If you have experience in Python (and I know you do), you'll find Java more OOPy and easier to handle when it comes to GUI.
The inheritance is DAMN hard to get, but when you get it, you'll like it. | <urn:uuid:786e2316-3086-4e9c-99ea-191043ca844a> | 2.84375 | 319 | Comment Section | Software Dev. | 69.080301 |
The mechanics of creating a table are relatively straight forward. Being able to design a well thought out database that will scale to meet the needs of a large scale enterprise is a very challenging undertaking. In these examples we will be working through development of a fairly simple three table database. In doing so we will get to cover a good deal of the development basics for creating tables and indexes.
CREATE TABLE IF NOT EXISTS person ( num INT(11) NOT NULL DEFAULT 0 , firstname VARCHAR(20) NULL , gender_code CHAR(1) NULL , birth_dttm DATETIME NULL , inactive_date DATETIME NULL , lastname VARCHAR(30) NULL , PRIMARY KEY (num) ) ENGINE = MYISAM GO
CREATE TABLE IF NOT EXISTS phone ( person_num INT(11) NOT NULL DEFAULT 0 , type_code CHAR(3) NOT NULL , area_code CHAR(3) NULL , exchange CHAR(3) NULL , extension CHAR(4) NULL , PRIMARY KEY (person_num, type_code) ) ENGINE = MYISAM GO
CREATE TABLE IF NOT EXISTS address ( person_num INT(11) NOT NULL DEFAULT 0 , type_code CHAR(4) NOT NULL , street1 CHAR(30) NULL , street2 CHAR(30) NULL , city CHAR(30) NULL , state CHAR(2) NULL , postal_code CHAR(10) NULL , PRIMARY KEY (person_num, type_code) ) ENGINE = MYISAM GO
It is possible, though not advised to create a table without a primary key. I will discuss primary keys on a different page yet to be created. It is also possible to set initial default values for a column though none of the columns in our tables were suitable candidates to do this. There are many good primers on creating tables and databases. The purpose of this page is just to show the basic MySQL syntax by example for creating a table. Also, taking the create table for an existing table and using it as a model is also a very good practice and means of learning. | <urn:uuid:457a46b5-cf5b-460e-be31-f71d7ce3e421> | 3.0625 | 451 | Tutorial | Software Dev. | 41.739007 |
This page is the start of the tour of the Evolution of the Solar System. The navigation button for the tour can be found at the top of the page. With a subject like the evolution of the solar system, there are a lot of things to discuss; the initial formation of the Sun, the 9 planets, various interesting moons, and their evolution from the dawn of time through where they are today. Because of the size of the subject, the tour has been broken into three segments. This is the first segment, and will present the solar nebula and the forming Sun and planets. You can skip ahead if you like by using the links at the bottom of this page. To proceed with the tour, just press the forward link (F) on the button at the top of the page.
This is page 1 of 60 | <urn:uuid:d75dfcf7-3242-4b18-b0b8-53a774f48d2c> | 2.96875 | 167 | Truncated | Science & Tech. | 68.192568 |
PBS' premier science series helps viewers of all ages explore the science behind the headlines. Along the way, NOVA programs demystify science and technology, and highlight the people involved in scientific pursuits.
Wednesday, January 2 at 9:00 p.m. Doomsday Volcanoes
The eruption of Iceland’s Eyjafjallajökull volcano in 2010 turned much of the northern hemisphere into an ash-strewn no-fly zone. But Eyjafjallajökull was just the start. Katla, an Icelandic volcano 10 times bigger, has begun to swell and grumble. Two more giants, Hekla and Laki, could erupt without warning. Iceland is a ticking time bomb: When it blows, the consequences will be global. Meet scientists trying to understand those consequences — for air travel and for the global food supply and Earth’s climate. Could we be plunged into years of cold and famine? What can we do to prepare for the coming disaster?
Wednesday, January 9 at 9:00 p.m. Decoding Neanderthals
What happened when the first modern humans encountered Neanderthals 60,000 years ago? In 2010, a team led by geneticist Svante Paabo announced that they had reconstructed much of the Neanderthal genome and the analysis showed that modern humans and Neanderthals had interbred, leaving a small signature of Neanderthal genes in everyone outside Africa today. NOVA explores the implications of this exciting discovery. Were Neanderthals really mentally inferior, as inexpressive and clumsy as the cartoon caveman they inspired? NOVA examines a range of new evidence for Neanderthal self-expression and language, suggesting that we may have underestimated our long-vanished cousins.
Watch the Preview
Wednesday, January 16 at 9:00 p.m. Ice Age Death Trap
Racing against developers in the Rockies, archaeologists uncover a unique site packed with astonishingly preserved bones of mammoths, mastodons and other giant extinct beasts, opening a window on the vanished world of the Ice Age.
Watch the Preview
Wednesday, January 23 at 9:00 p.m. Rise of the Drones
Drones. These unmanned flying robots — some as large as jumbo jets, others as small as birds — do things straight out of science fiction. Much of what it takes to get these robotic airplanes to fly, sense and kill has remained secret. But now, with unprecedented access to drone engineers (including a rare interview with the “Father of the Predator,” Abe Karem) and those who operate drones for the U.S. military, NOVA reveals the amazing technologies that make them so powerful. Discover the cutting-edge technologies that are propelling us toward a new chapter in aviation history. | <urn:uuid:0ee0dcd2-52fa-45bc-8c2b-fdefb7c8d306> | 3.15625 | 572 | Content Listing | Science & Tech. | 47.249101 |
Chel Anderson is a North Shore naturalist. She lives here in Cook County and joins us periodically to talk about phenology or what’s going on in the woods right now. Welcome, Chel!
Well, one of the most common tracks we see in winter snow is the familiar snowshoe hare. So, what are they doing to get ready for spring?
Anderson: They are doing what everything’s doing still, right now, which is just trying to stay alive and that’s increasingly hard at this time of year if you’re a browser in particular. So, something that’s eating the woody vegetation in the case of wintertime. Lots of things are getting buried under the snow that otherwise would be available to you, and you’re eating right along and snowshoe hares don’t travel huge distances in the winter. They’re not, you know, covering huge areas, so they’re working through their available foods, which, at this time of year, like I said, includes, you know, woody vegetation, but not heavy woody vegetation. They can’t be, you know, eating great, big limbs of things, they have to work on small twigs, on buds, on the inner bark of branches of trees that might fall down, you know, in a windstorm or something, or in the case of willows, things like that, that don’t get real heavy branches or stems, they can clip those off and work on the inner bark of those. And, of course, they’ll also eat the needles of conifers, so they’re just trying to stay on top of making sure they get enough to eat and out of sight of predators, which also are on the steady lookout for prey and hares are a very important prey species for many critters: foxes, coyotes, fishers, bobcats, lynx, raptors, owls, goshawks and returning things, things that will be starting to come back early on as winter kind of starts to melt away, new things will be on the lookout for hares. So, hares spend a lot of time this time of year, and really at all times, just kind of resting during the day when they can stay of sight, find a secluded spot and hanging out there. And they’re primarily crepuscular and nocturnal, so they’re feeding mostly at night, and they generally stick to fairly regular routes and areas that they spend different parts of their day in.
Anderson: Yeah, and that reminds me that I just feel like the dullest of observers this year, because they have been lots of tracks around where I frequent, you know, trails around our house, and I have yet to actually see a hare this year. And, I just can’t believe how dull-witted I must be to not have been able to pick one out this year.
I don’t know. Earlier in the year, I did see quite a few, but this winter I haven’t really seen that many. I’ve seen tracks, but I haven’t seen them actually.
Anderson: Well, as I said, they are mostly active in the dim light and darkness, so I guess that gives me a little bit of an excuse. But, one thing is that they’re probably aren’t as many around as it seems based on the tracks, because, again, hares are sticking into a fairly small area and they’re very well camouflaged. They do take quite awhile to fully molt and change color, so that’s why sometimes in the spring when the snow goes early we see hares that are looking really obvious because they’re still mostly white and the reverse in the fall. So, it takes about 10 weeks, I think, for the total molt to happen.
I tend to categorize hares, bunnies, and rabbits all together and I shouldn’t do that. These are snowshoe hares.
Anderson: It’s a common thing. These are snowshoe hares, so perfectly, marvelously adapted to our world here, because they have those incredibly long hind legs and huge feet that allow them to literally float on top of the snow. So, I don’t know if you stepped off the trails anywhere when the snow was at its deepest, but around our place it was about 40 inches deep. So, you know, without your own snowshoes of some kind of another, it was not much for good going out there. But, again, when the hare populations are large, they tend to show up, you know, a lot in the summer out eating in the herbaceous vegetation that grows along the roadsides, especially at night, again, because that’s when they’re most active. And, during the time when the first litters are being born, then, you know, there’s a sudden surge in the population.
When is that going to start?
Anderson: Yeah, well, they’ll start in the spring. Here, hares might have two litters over the course of the summer. They’re very prolific breeders. Hares tend to live only about a year, so they have to do a good job on the reproducing side in order to keep their numbers going. And they do have cyclic populations, the reasons for which are not all that well understood, but it’s kind of a 10-year cycle of peaks and valleys, and the predators that they feed have kind of a trailing cycle often that’s associated with the cycle that the hares have.
When you say they’ll start to have litters in spring is it in April? May?
Anderson: Oh, May. June. Yeah. And, I’m not sure where the cycle is supposedly right now. I’m pretty sure it’s not at peak right now, but I don’t know if it’s really down in the valley or if it’s somewhere in the middle. But, there may just be fewer around then there were, say, a few years ago. I’m not really sure, but it’s discouraging to me that I haven’t actually seen one, but I’m going to keep an eye out for them.
Chel Anderson, botanist and plant ecologist. Thanks for helping us understand snowshoe hares.
Anderson: You bet. | <urn:uuid:d029049a-8e83-439d-bdcc-92859927c3c7> | 2.859375 | 1,388 | Audio Transcript | Science & Tech. | 66.205302 |
eqn not supported
If point antialiasing is disabled, the actual size is determined by rounding the supplied size to the nearest integer. (If the rounding results in the value 0, it is as if the point size were 1.) If the rounded size is odd, then the center point ($ x $, $ y $) of the pixel fragment that represents the point is computed as
where $w$ subscripts indicate window coordinates. All pixels that lie within the square grid of the rounded size centered at ($ x $, $ y $) make up the fragment. If the size is even, the center point is
and the rasterized fragment's centers are the half-integer window coordinates within the square of the rounded size centered at ($ x $, $ y $). All pixel fragments produced in rasterizing a nonantialiased point are assigned the same associated data, that of the vertex corresponding to the point.
If antialiasing is enabled, then point rasterization produces a fragment for each pixel square that intersects the region lying within the circle having diameter equal to the current point size and centered at the point's ($ x sub w $, $ y sub w $). The coverage value for each fragment is the window coordinate area of the intersection of the circular region with the corresponding pixel square. This value is saved and used in the final rasterization step. The data associated with each fragment is the data associated with the point being rasterized.
Not all sizes are supported when point antialiasing is enabled. If an unsupported size is requested, the nearest supported size is used. Only size 1 is guaranteed to be supported; others depend on the implementation. To query the range of supported sizes and the size difference between supported sizes within the range, call glGet with arguments GL_SMOOTH_POINT_SIZE_RANGE and GL_SMOOTH_POINT_SIZE_GRANULARITY. For aliased points, query the supported ranges and granularity with glGet with arguments GL_ALIASED_POINT_SIZE_RANGE and GL_ALIASED_POINT_SIZE_GRANULARITY.
A non-antialiased point size may be clamped to an implementation-dependent maximum. Although this maximum cannot be queried, it must be no less than the maximum value for antialiased points, rounded to the nearest integer value.
GL_POINT_SIZE_RANGE and GL_POINT_SIZE_GRANULARITY are deprecated in GL versions 1.2 and greater. Their functionality has been replaced by GL_SMOOTH_POINT_SIZE_RANGE and GL_SMOOTH_POINT_SIZE_GRANULARITY.
GL_INVALID_OPERATION is generated if glPointSize is executed between the execution of glBegin and the corresponding execution of glEnd.
Table of Contents | <urn:uuid:6767456b-22ef-493f-9dee-c6cf86118e68> | 2.84375 | 603 | Documentation | Software Dev. | 31.528058 |
Radar studies of the vertical distribution of insects migrating over southern Britain: the influence of temperature inversions on nocturnal layer concentrations
Reynolds, D.R., Chapman, J.W., Edwards, A.S., Smith, A.D., Wood, C. R., Barlow, J. F. and Woiwod, I.P. (2005) Radar studies of the vertical distribution of insects migrating over southern Britain: the influence of temperature inversions on nocturnal layer concentrations. Bulletin of Entomological Research, 95 (3). pp. 259-274. ISSN 0007-4853
Official URL: http://journals.cambridge.org/action/displayAbstra...
Insects migrating over two sites in southern UK (Malvern in Worcestershire, and Harpenden in Hertfordshire) have been monitored continuously with nutating vertical-looking radars (VLRs) equipped with powerful control and analysis software. These observations make possible, for the first time, a systematic investigation of the vertical distribution of insect aerial density in the atmosphere, over temporal scales ranging from the short (instantaneous vertical profiles updated every 15 min) to the very long (profiles aggregated over whole seasons or even years). In the present paper, an outline is given of some general features of insect stratification as revealed by the radars, followed by a description of occasions during warm nights in the summer months when intense insect layers developed. Some of these nocturnal layers were due to the insects flying preferentially at the top of strong surface temperature inversions, and in other cases, layering was associated with higher-altitude temperature maxima, such as those due to subsidence inversions. The layers were formed from insects of a great variety of sizes, but peaks in the mass distributions pointed to a preponderance of medium-sized noctuid moths on certain occasions.
Repository Staff Only: item control page | <urn:uuid:df85ca36-dc0d-44e2-a86d-c833d08ccf42> | 2.71875 | 404 | Academic Writing | Science & Tech. | 38.208579 |
Two weeks ago, we published a new map of the Earth at night, built by Earth Observatory designers together with colleagues at the National Geophysical Data Center. That map—made possible by a new NASA and the National Oceanic and Atmospheric Administration (NOAA) satellite—showed the footprint of human civilization on the planet, as revealed by the lights we use to brighten the darkness.
But it turns out the map showed something more. Astute readers noticed lights in areas that were thought to be uninhabited. Many of those readers pointed to Western Australia and asked: How can there be so much light there?
The top image above shows the night lights of Australia as observed by the Visible Infrared Imaging Radiometer Suite (VIIRS) on the Suomi NPP satellite in April and October 2012. The composite image includes manmade light sources and the light of wildfires. The data were acquired over nine days in April 2012 and thirteen days in October 2012, and it took the satellite 312 orbits and 2.5 terabytes of data to get a clear shot of every parcel of Earth’s land surface.
The second map is a mosaic showing the burned areas of the landscape (red) from October 11–24, 2012, combined with urban areas (black). The data were collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on NASA’s Terra and Aqua satellites. In effect, the map shows where fires burned that month. Though many rural areas of interior Australia are dry and relatively barren by some standards, there is still enough vegetation to burn, as you can see by clicking on this view from the International Space Station and others from the MODIS instruments.
The extent of the lighting in the Outback and bush country is a function of composite imaging. Fires and other lights that were detected on one day were integrated into the composite, multi-day picture despite being temporary phenomena. Because different lands burned at different times that the satellite passed over, the cumulative result is the appearance of a massive blaze. But while the cities are fixed, the fires were temporary, moveable features. The night lights data set is a scientific work in progress, and the maps will be refined and improved over time.
Not every light in the night view matches up with a fire—partly because the fire map does not include fires from April and partly because not every fire leaves a scar that is detectable from space. Even simple cloud cover could prevent burn scars from being observed.
Aside from the fires, some of the night lights appearing in uninhabited areas can be attributed to natural gas flares, lightning, oil drilling or mining operations, and fishing boats—all of which can show up as points of light. One example is natural gas drilling in the Bakken Formation in North Dakota; another is the fishing boats plying the seas of Asia.
And ultimately, the new images of Earth at night are ripe for new discoveries. It’s easy to say that lands are uninhabited or barren—that there’s nothing out there to make light. But the satellite says there is light, so we should probably go take a look at what we have been overlooking or simply could not see before.
NASA Earth Observatory images by Robert Simmon, using Suomi NPP VIIRS data provided by Chris Elvidge (NOAA National Geophysical Data Center); MODIS Active Fire & Burned Area Products; and urban data from the University of Wisconsin-Madison Center for Sustainability and the Global Environment. Suomi NPP is the result of a partnership between NASA, NOAA, and the Department of Defense. Caption by Michael Carlowicz.
- Suomi NPP - VIIRS | <urn:uuid:8ec2352c-e1b2-48b6-af5c-ce04e9f07ac6> | 3.84375 | 755 | Knowledge Article | Science & Tech. | 38.737404 |
Static Sub LineWidth ( Width As Float )
Specify the width of rasterized lines.
Specifies the width of rasterized lines.
The initial value is 1.
specifies the rasterized width of both aliased and antialiased
Using a line width other than 1 has different effects,
depending on whether line antialiasing is enabled.
To enable and disable line antialiasing, call
Gl.Enable and Gl.Disable
with argument Gl.LINE_SMOOTH. Line
antialiasing is initially
If line antialiasing is disabled,
the actual width is determined by rounding the supplied width
to the nearest integer.
(If the rounding results in the value 0,
it is as if the line width were 1.)
pixels are filled in each column that is rasterized,
is the rounded value of width
pixels are filled in each row that is rasterized.
If antialiasing is enabled,
line rasterization produces a fragment for each pixel square
that intersects the region lying within the rectangle having width
equal to the current line width,
length equal to the actual length of the line,
and centered on the mathematical line segment.
The coverage value for each fragment is the window coordinate area
of the intersection of the rectangular region with the corresponding
This value is saved and used in the final rasterization step.
Not all widths can be supported when line antialiasing is enabled. If an
unsupported width is requested, the nearest supported width is used.
Only width 1 is guaranteed to be supported; others depend on the
implementation. Likewise, there is a range for aliased line widths as well.
To query the range of supported widths and the size
difference between supported widths within the range, call Gl.Get
with arguments Gl.ALIASED_LINE_WIDTH_RANGE,
Gl.SMOOTH_LINE_WIDTH_RANGE, and Gl.SMOOTH_LINE_WIDTH_GRANULARITY.
The line width specified by Gl.LineWidth
is always returned when Gl.LINE_WIDTH
Clamping and rounding for aliased and antialiased lines have no effect on the specified value.
Nonantialiased line width may be clamped to an implementation-dependent maximum. Call Gl.Get
with Gl.ALIASED_LINE_WIDTH_RANGE to determine the maximum width.
In OpenGL 1.2, the tokens Gl.LINE_WIDTH_RANGE and Gl.LINE_WIDTH_GRANULARITY were replaced by Gl.ALIASED_LINE_WIDTH_RANGE,
Gl.SMOOTH_LINE_WIDTH_RANGE, and Gl.SMOOTH_LINE_WIDTH_GRANULARITY. The old names are retained for backward compatibility, but should not be used in new code.
Gl.INVALID_VALUE is generated if width
is less than or equal to 0.
with argument Gl.LINE_WIDTH
Gl.Get with argument Gl.ALIASED_LINE_WIDTH_RANGE
Gl.Get with argument Gl.SMOOTH_LINE_WIDTH_RANGE
Gl.Get with argument Gl.SMOOTH_LINE_WIDTH_GRANULARITY
with argument Gl.LINE_SMOOTH
See original documentation on OpenGL website | <urn:uuid:e7f54ffd-0c3a-412b-a6d1-2c31fd73de0a> | 2.6875 | 747 | Documentation | Software Dev. | 41.363927 |
June 2012 Wildfire Smoke Dispersion
Credit: NOAA Visualization Lab
The HYSPLIT wildfire smoke model run on June 29th, 2012 shows the cloud of smoke being emitted from many of the wildfires raging in the Western U.S. at that time.
The actual locations of these point-source pollutants can be seen as very high concentration smoke areas. The ability of the GOES satellite to detect aerosols is an important input to these models, as are the wind measurements derived from GOES infrared imagery. | <urn:uuid:469d2737-8307-4e43-8e5c-ce7f2258acaa> | 3 | 105 | Knowledge Article | Science & Tech. | 44.229373 |
[whatwg] Physical quantities: <var> or <i>?
Jukka K. Korpela
jkorpela at cs.tut.fi
Thu Apr 14 07:02:18 PDT 2011
Looking at the nice summary (with examples) of text-level markup at
I started wondering why there is no example of markup for symbols of
physical quantities. The descriptions of individual elements or their
examples don't seem to say anything about this either.
So what markup should we use for E = mc², given that by the applicable
standards, E, M, and c should appear in italics and the other characters as
Physical quantities surely satisfy the requirement that "typical typographic
presentation is italicized" in the following, and they are to be offset from
the normal prose, but why aren't they mentioned in the fairly long list of
"The i element represents a span of text in an alternate voice or mood, or
otherwise offset from the normal prose, such as a taxonomic designation, a
technical term, an idiomatic phrase from another language, a thought, a ship
name in Western texts, or some other prose whose typical typographic
presentation is italicized."
(As an aside, the wording "a taxonomic designation" is too broad, as by
biological nomenclature rules, genus and species names are to be italiced
but higher taxons, e.g. family names, like Canidae, must not. Besides, e.g.
an English name of a species is taxonomic too... So "scientific names of
organisms" would be a better formulation.)
But the i element should obviously be used in the absence of a more semantic
element; e.g., not for expressions that fall into the scope of use of the
Should we consider the var element as covering physical quantities too?
After all, they can be regarded as variables in a broad sense, as symbols
that denote different values in different situations. However, <var>c</var>
would be odd, wouldn't it, since the symbol denotes a universal constant of
So I would guess that <i>E</i> = <i>m</i><i>c</i>² is the way to go.
I think an example like this, or the addition of physical quantities into
the list of examples, or both, would be the semantics and intended use of
elements somewhat clearer.
More information about the whatwg | <urn:uuid:2a85ed44-a8c1-44cd-9bb4-21f9dc322193> | 2.859375 | 533 | Comment Section | Software Dev. | 49.987727 |
I don't quite get this "string".find()
programmer.py at gmail.com
Thu Nov 11 21:04:56 CET 2004
Ahh, I see it now. It seems strange to me, but your find helped make
sense of it.
I guess I thought:
1) an empty string is like "nothing"
2) you can never find "nothing" in something
But I guess an empty string isn't nothing, but a string with no
length. Ahh, it's still darned strange :).
On Thu, 11 Nov 2004 14:57:12 -0500, Tim Peters <tim.peters at gmail.com> wrote:
> [Jaime Wyant]
> > Will someone explain this to me?
> > >>> "test".find("")
> > 0
> > Why is the empty string found at position 0?
> Because index 0 is the smallest index at which "" is found:
> >>> "test"[0:0] == ""
> As a string method, find() acts like this (skipping obfuscating optimizations):
> def find(haystack, needle):
> for i in range(len(haystack)):
> if haystack[i : i+len(needle)] == needle:
> return i
> return -1
More information about the Python-list | <urn:uuid:0e9b8fa8-2270-49f2-be10-d9d9bd13ac2f> | 2.703125 | 298 | Comment Section | Software Dev. | 89.896429 |
a tank initially contains salt in the pores of inert materials and 10 gal of fresh water. The salt dissolved at a rate per min of 2 times the difference between 3lb/gal and the concentration of the brine. The two gal of fresh water enters the tank per min. How much salt will be dissolved in the 1st 10 min?
Can I get the initial value of salt from the equation?
what equation should i use?
dE/dt = 2(3-C)
where C = E/(100+2t) or C = (X-E)/(100+2t)
x=initial value of salt | <urn:uuid:8ec399b6-1ad9-43f9-90cf-c638271090d2> | 2.984375 | 133 | Q&A Forum | Science & Tech. | 88.391361 |
Here are three 'tricks' to amaze your friends. But the really
clever trick is explaining to them why these 'tricks' are maths not
magic. Like all good magicians, you should practice by trying. . . .
Write down a three-digit number Change the order of the digits to
get a different number Find the difference between the two three
digit numbers Follow the rest of the instructions then try. . . .
Pick the number of times a week that you eat chocolate. This number must be more than one but less than ten.
Multiply this number by 2. Add 5 (for Sunday). Multiply by 50... Can you explain why it. . . .
Replace each letter with a digit to make this addition correct.
Which set of numbers that add to 10 have the largest product?
Choose any three by three square of dates on a calendar page.
Circle any number on the top row, put a line through the other
numbers that are in the same row and column as your circled number.
Repeat. . . .
Liam's house has a staircase with 12 steps. He can go down the steps one at a time or two at time. In how many different ways can Liam go down the 12 steps?
In the following sum the letters A, B, C, D, E and F stand for six
distinct digits. Find all the ways of replacing the letters with
digits so that the arithmetic is correct.
Take any whole number between 1 and 999, add the squares of the
digits to get a new number. Make some conjectures about what
happens in general.
This jar used to hold perfumed oil. It contained enough oil to fill
granid silver bottles. Each bottle held enough to fill ozvik golden
goblets and each goblet held enough to fill vaswik crystal. . . .
Eight children enter the autumn cross-country race at school. How
many possible ways could they come in at first, second and third
Use the numbers in the box below to make the base of a top-heavy
pyramid whose top number is 200.
Take any two digit number, for example 58. What do you have to do to reverse the order of the digits? Can you find a rule for reversing the order of digits for any two digit number?
Make a set of numbers that use all the digits from 1 to 9, once and
once only. Add them up. The result is divisible by 9. Add each of
the digits in the new number. What is their sum? Now try some. . . .
Three dice are placed in a row. Find a way to turn each one so that
the three numbers on top of the dice total the same as the three
numbers on the front of the dice. Can you find all the ways to. . . .
A little bit of algebra explains this 'magic'. Ask a friend to pick 3 consecutive numbers and to tell you a multiple of 3. Then ask them to add the four numbers and multiply by 67, and to tell you. . . .
What are the missing numbers in the pyramids?
Six points are arranged in space so that no three are collinear.
How many line segments can be formed by joining the points in
Can you fit Ls together to make larger versions of themselves?
Points A, B and C are the centres of three circles, each one of
which touches the other two. Prove that the perimeter of the
triangle ABC is equal to the diameter of the largest circle.
Look at what happens when you take a number, square it and subtract your answer. What kind of number do you get? Can you prove it?
Find the area of the annulus in terms of the length of the chord
which is tangent to the inner circle.
Consider the equation 1/a + 1/b + 1/c = 1 where a, b and c are
natural numbers and 0 < a < b < c. Prove that there is
only one set of values which satisfy this equation.
Advent Calendar 2011 - a mathematical activity for each day during the run-up to Christmas.
Imagine we have four bags containing a large number of 1s, 4s, 7s and 10s. What numbers can we make?
There are four children in a family, two girls, Kate and Sally, and
two boys, Tom and Ben. How old are the children?
Can you discover whether this is a fair game?
In this 7-sandwich: 7 1 3 1 6 4 3 5 7 2 4 6 2 5 there are 7 numbers between the 7s, 6 between the 6s etc. The article shows which values of n can make n-sandwiches and which cannot.
Some puzzles requiring no knowledge of knot theory, just a careful
inspection of the patterns. A glimpse of the classification of
knots and a little about prime knots, crossing numbers and. . . .
Imagine we have four bags containing numbers from a sequence. What numbers can we make now?
In how many distinct ways can six islands be joined by bridges so that each island can be reached from every other island...
Semicircles are drawn on the sides of a rectangle ABCD. A circle passing through points ABCD carves out four crescent-shaped regions. Prove that the sum of the areas of the four crescents is equal to. . . .
Can you cross each of the seven bridges that join the north and south of the river to the two islands, once and once only, without retracing your steps?
A paradox is a statement that seems to be both untrue and true at the same time. This article looks at a few examples and challenges you to investigate them for yourself.
What does logic mean to us and is that different to mathematical logic? We will explore these questions in this article.
This article invites you to get familiar with a strategic game called "sprouts". The game is simple enough for younger children to understand, and has also provided experienced mathematicians with. . . .
Here are some examples of 'cons', and see if you can figure out where the trick is.
If you can copy a network without lifting your pen off the paper and without drawing any line twice, then it is traversable.
Decide which of these diagrams are traversable.
Choose a couple of the sequences. Try to picture how to make the next, and the next, and the next... Can you describe your reasoning?
Can you find all the 4-ball shuffles?
Use your logical reasoning to work out how many cows and how many
sheep there are in each field.
How many pairs of numbers can you find that add up to a multiple of
11? Do you notice anything interesting about your results?
Euler discussed whether or not it was possible to stroll around Koenigsberg crossing each of its seven bridges exactly once. Experiment with different numbers of islands and bridges.
Spotting patterns can be an important first step - explaining why it is appropriate to generalise is the next step, and often the most interesting and important.
What can you say about the angles on opposite vertices of any
cyclic quadrilateral? Working on the building blocks will give you
insights that may help you to explain what is special about them.
A game for 2 players that can be played online. Players take it in
turns to select a word from the 9 words given. The aim is to select
all the occurrences of the same letter.
Pick a square within a multiplication square and add the numbers on
each diagonal. What do you notice?
Can you arrange the numbers 1 to 17 in a row so that each adjacent
pair adds up to a square number?
This article stems from research on the teaching of proof and
offers guidance on how to move learners from focussing on
experimental arguments to mathematical arguments and deductive
This is the second article on right-angled triangles whose edge lengths are whole numbers. | <urn:uuid:0a3bb0e1-7e20-4b1a-8025-4b6cebb889d0> | 3.421875 | 1,695 | Content Listing | Science & Tech. | 74.789409 |
Major Section: PROGRAMMING
For non-negative integers,
(integer-length i) is the minimum number
of bits needed to represent the integer. Any integer can be
represented as a signed two's complement field with a minimum of
(+ (integer-length i) 1) bits.
The guard for
integer-length requires its argument to be an
Integer-length is defined in Common Lisp. See any
Common Lisp documentation for more information. | <urn:uuid:2c5a8c6a-08d8-496f-b9e8-2847ca0957c1> | 2.78125 | 97 | Documentation | Software Dev. | 41.53 |
Science subject and location tags
Articles, documents and multimedia from ABC Science
Thursday, 10 May 2012
A new study has found sand dunes on the red planet are at least five times more active than earlier estimates, being comparable to dune movement rates on Earth.
Wednesday, 9 May 2012
StarStuff Podcast Astronomers witness a black hole ripping apart and destroying a star. Plus; the truth about last weekend's 'super Moon', and SpaceX flight delayed again.
Tuesday, 8 May 2012
Astronomers searching for Earth-like planets can strike off stars that have a 'hot Jupiter' orbiting around them, according to a new study.
Friday, 4 May 2012
Scientists have used sound waves to determine the composition of the Earth's inner mantle, possibly solving the mystery of our planet's missing silicon.
Wednesday, 2 May 2012
StarStuff Podcast All systems go for the launch of the first private spaceflight to the International Space Station. Plus; gamma ray bursts ruled out as the source of cosmic rays, and plans to mine asteroids.
Monday, 30 April 2012
Of all the hurdles facing Planetary Resources' plan to mine asteroids, legal jurisdiction is not at the top of the list
Friday, 27 April 2012
Finding planets outside our solar system that can sustain life should be made a top priority, say Australian astronomers.
Wednesday, 25 April 2012
StarStuff Podcast Professor Brian Schmidt tells how dying stars led to Nobel notoriety. Plus; scientists create a cloaking device, the world's smallest transistor and measuring the perfect kilogram.
Monday, 23 April 2012
Scientists studying life deep below an asteroid impact crater in the United States have found tiny organisms thriving kilometres below the surface.
Wednesday, 18 April 2012
StarStuff Podcast Fresh look at data from NASA's Viking landers suggests evidence of life on the red planet. Plus; new data confirms the presence of dark energy and North Korea's failed launch into space.
Friday, 13 April 2012
New analysis of 36-year-old data, resuscitated from printouts, shows NASA may have found life on Mars.
Wednesday, 11 April 2012
StarStuff Podcast No decision yet about over who will host the world's largest radio telescope as a new working group examines the bids. Plus; supernova remnant Cassiopeia-A has turned itself inside out, and did the Moon sink the Titanic?
Wednesday, 4 April 2012
StarStuff Podcast Scientists say it's time to abandon existing theories that Earth is composed of the same material as chondritic meteoroids. Plus, pinpointing when dark energy became the dominate force in the universe, and North Korea prepares controversial missile launch.
Monday, 2 April 2012
Dark patches visible across much of the northern Martian hemisphere are volcanic glass according to a new study
Thursday, 29 March 2012
A new report claims existing assumptions about the composition of the Earth are wrong and don't match the evidence. | <urn:uuid:8bd65f11-27e6-4bed-a494-169249660ca6> | 2.890625 | 600 | Content Listing | Science & Tech. | 44.198176 |
A karyotype is the complete set of all chromosomes of a cell of any living organism. The chromosomes are arranged and displayed (often on a photo) in a standard format: in pairs, ordered by size. Karyotypes are examined in searches for chromosomal aberrations, and may be used to determine other macroscopically visible aspects of an individual's genotype, such as sex (XX vs. XY pair). The study of karyotypes is known as karyology.
Normal human karyotypes are denoted 46,XX (for most women) and 46,XY (for most men). However, some individuals have other karyotypes with added or missing sex chromosomes, including 47,XYY, 47,XXY, 47,XXX and 45,X. The other possibility, 45,Y, does not occur, as an embryo without an X chromosome is incapable of survival.
In the "classic" (depicted) karyotype, a dye, often Giemsa, is used to make bands on the chromosomes visible. This is also referred to as G-banding. Each chromosome has a characteristic banding patern which helps to identify them (notice that the two chromosomes of one pair have the same banding pattern).
In this newer technique, several different probes specific of one chromosome pair, carrying different amounts of a set of fluorescent dyes, are hybridized to the chromosomes in a technique known as fluorescent in situ hybridization (FISH). This gives each chromosome pair unique spectral characteristics due to the relative amount of each of the fluorochromes. Chromosomes can be automatically identified in fluorescence microscopy through an interferometer and a computer analysis (spectral imaging ) | <urn:uuid:783b2366-a0c3-49a7-9086-cf010c424f9d> | 3.875 | 352 | Knowledge Article | Science & Tech. | 29.038187 |
Can you tell a glass of sparkling mineral water from Alka Seltzer, a “just ripe” melon from one that should be eaten only after a few days?
We perceive our environment through our eyes and they can only detect certain light wavelengths. Actually there are many more wavelengths available (and insects are able to exploit some of them). What if we insert in our cell phone a sensors that can be used to look at what is around detecting a much larger wavelength set? This is what some researchers at the Media Lab are trying to do.
Already today digital camera sensors (and the one in our cell phone are derived from those) can detect a broader wavelength set than the one detected by our eyes, and this is why manufacturers overlay on the sensor a filter to cut out those extra wavelengths. Remove that filter and you can get more data from the filter that would actually let a computer see more and discriminate characteristics in the environment (current sensors can detect infrared wavelength so a computer can get information on temperature of the object in the image…).
New sensors can be developed to intercept much broader wavelength spectrum and there may be a system of filters that can be over layered to restrict wavelengths depending on the purpose of the photo. There might even be sensors having individual pixel with different sensitivity to wavelength (or with different filter over layered) and these can be selected via software, thus allowing the detection of different characteristics in objects.
This is what people at the Media Lab are working on, embedding a sensor in your cell phone you can use to find out more about your environment. To this filter a glass full of Alka Seltzer would look very different from one filled with sparkling mineral water, a ripe melon looks different from one you are not supposed to eat for a few more days…
More specialized sensors are also in the making, such as the one shown in the photo, developed by NASA to fit your iPhone. This sensor plug in the iPhone port and can detect a number of substances in the environment. An app in your phone (or in the web for more serious analyses) can process these data and give you a quite different view of the place you are in.. It can also be used to create a map of the environment as more and more cell phone report data. Get ready for a new way to look around yourself! | <urn:uuid:e3251a5a-3569-4ac8-9a54-91193abfeace> | 2.8125 | 474 | Personal Blog | Science & Tech. | 40.06816 |
Error handling is an essential procedure in Visual Basic programming because it can help make the program error-free. An error-free program can run smoothly and efficiently, and the user does not have to face all sorts of problems such as program crash or system hang.
Errors often occur due to incorrect input from the user. For example, the user might make the mistake of attempting to ask the computer to divide a number by zero which will definitely cause system error. Another example is the user might enter a text (string) to a box that is designed to handle only numeric values such as the weight of a person, the computer will not be able to perform arithmetic calculation for text therefore will create an error. These errors are known as synchronous errors.
Therefore a good programmer should be more alert to the parts of program that could trigger errors and should write errors handling code to help the user in managing the errors. Writing errors handling code should be considered a good practice for Visual Basic programmers, so do try to finish a program fast by omitting the errors handling code. However, there should not be too many errors handling code in the program as it create problems for the programmer to maintain and troubleshoot the program later.
Writing the Errors Handling Code :
We shall now learn how to write errors handling code in Visual Basic. The syntax for errors handling is
On Error GoTo program_label
where program_label is the section of code that is designed by the programmer to handle the error committed by the user. Once an error is detected, the program will jump to the program_label section for error handling. It acts like a bookmark in VB
Intro : This code shows how to handle error 'Division By Zero'.
Private Sub CmdCalculate_Click() Dim firstNum, secondNum As Double firstNum = Txt_FirstNumber.Text secondNum = Txt_SecondNumber.Text On Error GoTo error_handler Lbl_Answer.Caption = firstNum / secondNum Exit Sub 'To prevent error handling even the inputs are valid error_handler: Lbl_Answer.Caption = "Error" Lbl_ErrorMsg.Visible = True Lbl_ErrorMsg.Caption = " You attempt to divide a number by zero!Try again!" End Sub
The line 'On Error GoTo error_handler' gets executed when there occurs an error in DIVISION.
When we input secondnum=0 then the line returns an error. then the 'error_handler' section of code is executed, simple.
NOTE : IT may be noticed that if there is no error , the error handling part of code is NOT executed due to use of EXIT SUB.
Was'nt that easy, handling errors? | <urn:uuid:4fe99e90-7ffa-45fc-9670-bc1eca9227cf> | 3.859375 | 567 | Tutorial | Software Dev. | 47.12036 |
In many circumstances you may want to draw a DisplayObject into a Bitmap. Perhaps you want to take a 'snapshot' of a Sprite, or create a particle effect in which particles leave trails. This very important method became even more important in development for mobile as Bitmaps are easier to process for mobile devices than vector content. We discuss BitmapData.draw method with special emphasis on the second, often overlooked, transform matrix parameter. Click the screen shot below or on this link to open the SWF version in a new window:
Download the well-commented source files corresponding to the how-to.
Comments and Code
Below is the Timeline code behind the example above. We left the comments within the code for greater clarity.
A MovieClip has been created on the stage, stored in the Library, and linked to AS3 under the name of 'ClipToDraw'.
var clip:MovieClip=new ClipToDraw();
We are adding an instance of ClipToDraw, 'clip',to the Display List for comparison purposes, although the BitmapData.draw method will work regardless if 'clip' is or is not on the Display List.
We creating a BitmapData, 'bd1', with the same dimensions as our 'clip'. The BitmapData does not support transparency ('false' parameter), and is filled with white color. We create a Bitmap, 'bitmap1', with bitmapData 'bd1', add the Bitmap to the Display List and position it.
var bd1:BitmapData=new BitmapData(clipWidth,clipHeight,false,0xFFFFFFFF);
var bitmap1:Bitmap=new Bitmap(bd1);
We call the BitmapData method 'draw'. The first and the only non-optional parameter of the method is the DisplayObject that we want to draw - in our case 'clip'. If no other parameters of 'draw' method are supplied, 'clip' will be drawn at the original scale and positioned at (0,0) of 'bitmap1'. (At runtime, 'bitmap1', is the one next to 'clip').
To illustrate the second (optional) matrix parameter of the BitmapData.draw method, we create a second larger BitmapData object, 'bd2', filled with white, create a corresponding Bitmap, 'bitmap2', and add it to the Display List.
var bd2:BitmapData=new BitmapData(460,200,false,0xFFFFFFFF);
var bitmap2:Bitmap=new Bitmap(bd2);
We want to draw 'clip' into 'bd2' but a version of it that is scaled down by 70%, and translated with respect to 'bd2' by 30 and 40 pixels. We create a matrix, 'mat', apply 'scale' and 'translate' to it, and draw 'clip' into 'bd2' with the matrix 'mat'. This gives the first copy of 'clip' in the white Bitmap. Note that the transform matrix, 'mat' is used only for drawing purposes and does not affect the transform matrix of 'clip'. And vice-versa clip.transform.matrix (which is all along (a=1, b=0, c=0, d=1, tx=50, ty=40) as 'clip' is positioned at (50,40) on the stage) does not affect drawing into a BitmapData.
var mat:Matrix=new Matrix();
Now we want another copy of 'clip' drawn into 'bd2', scaled even more, rotated, and translated. We use the same matrix, 'mat', but clear previous transformations by resetting the matrix to 'new Matrix()' that returns the identity matrix.
Note: The BitmapData.draw method has several other parameters:
BitmapData.draw(source:IBitmapDrawable, matrix:Matrix = null,
colorTransform:flash.geom:ColorTransform = null, blendMode:String = null,
clipRect:Rectangle = null, smoothing:Boolean = false):void
We used the first two: 'source' which is most typically a DisplayObject (it can also be a BitmapData), and 'matrix' which defines the transform matrix to be applied to 'source' before drawing. The other (optional) parameters define the ColorTransform to be applied before drawing, or specify a blend mode. A useful 'clipRect' parameter defines a rectangular region in the source object to be drawn in the case when you do not wish the whole source object to be drawn. We find the first two parameters most useful.
This tutorial was written by Barbara Kaskosz of flashandmath. | <urn:uuid:9bbe9b08-564c-4d20-9aca-7c4589630fe2> | 2.734375 | 999 | Tutorial | Software Dev. | 53.204228 |
Atmosphere Under Assault
The Plot Against Hurricanes
By Joel Carlinsky
July 17, 2010 -
The term "hurricane" is an official but arbitray designation for a tropical storm that reaches sustained wind speeds of more than 75 miles per hour. Thus a single storm might pick up speed and become a "hurricane", then lose speed and be downgraded to a "tropical storm", then gain speed again and so on, several times in the course of it's existence. There therefore is really no such thing as a "hurricane", distinct from other tropical storms of the same type.
These strong tropical storms are quite common seasonally in the regions where they occur. They form along the equator, on both sides of it, and move toward the pole as they gain in strength. In modern times, forecasting when they will make landfall so inhabitants of low-lying coastal areas can evacuate has become the most important safety precaution available.
Other protective measure include building codes that try to design structures to withstand the high winds, and insurace coverage to enable owners of damaged buildings to rebuild afterwards.
Despite all efforts, however, nearly every year finds one or more hurricanes causing what the news media term a "natural disaster". When this happens the cameras pan over the wreakage and the announcer's voice describes the suffering of the "innocent victims" of "nature's wrath". The wisdom of millions of people choosing to live in a low-lying coastal area where hurricanes are known to be a frequent occurence is never mentioned. It is taken for granted that cities and such large populations belong there and it is "nature" that is to blame if they suffer any damage.
In the well-known case of New Orleans, the media constantly used the term "natural disaster". Not many were asking if maybe it was not very smart to build a city of 2,000,000 people in a low-lying coastal area known to have frequent hurricanes. Most of them simply assumed New Orleans belonged there.
More recently, in Haiti, many people were killed by mudslides
caused by heavy rains. The heavy rains were inevitable in
that climate. The mudslides, however, could have been avoided
by not deforesting the hillsides uphill from where the people
lived. The media called it a "natural disaster"
and called the people "innocent victims", but in
fact they were not innocent; they had committed suicide by
deforesting the hills above their villages.
But as a direct result of these and other news stories reflecting the views of the media ( and those who own the media ) there has been a growing demand in recent years to "do something" about hurricanes. The people who are asking that "something be done" about hurricanes are not demanding that "something be done" about deforestation, or about the construction of large cities in coastal zones, or about allowing millions of people to live in those areas. Those factors are simply accepted as normal and inevitable, and the demand is to "do something" about the hurricanes instead.
While at first glance it might seem not much could be done about such powerful storms, there have in fact been several suggestions along those lines. As long ago as the 1960s, the United States Air Force tried seeding hurricanes in the Carribean in the hope that they could be induced to use up most of their water content before reaching land. This program was not successful.
More recently other suggestions have been made, and one of them has been tried out by accident. The suggestion that a thin coating of oil on the waters of the ocean would retard evaporation sufficiently to prevent storms from growing is now being seen in action in the Gulf of Mexico as a result of an accidental oil spill. We shall soon see if this hypothesis has any merit.
By whatever means, though, it would be a serious mistake to prevent or weaken hurricanes. They are a normal and necessary part of the global environment we live in and are essential to the functioning of the coastal ecosystems of the regions where they occur.
Because they are a regular, seasonal phenomena, hurricanes are a part of the expected annual series of weather events and all species that live in a hurricane zone are adapted to their regular recurrence. They are therefore a part of the process that keeps the ecology in dynamic balance. Many species are dependent on them for creating the conditions they need.
A few examples:
- Hurricanes over water stir up bottom sediment which provides extra nourishment to plankton, which are the base of the oceanic food chain, so for several weeks after a hurricane all aquatic life florishes.
- Swift-churning waters break off small
pieces of coral reefs, which are carried some distance away and sink to the bottom to grow into new reefs. This is one important way in which coral propagates, so without hurricanes the reefs would continuet to grow in size,but could not spread to other areas to start new reefs.
- When a big tree falls, the gap in the canopy allows sunlight to reach a lot of seedlings and underbrush which need sunlight to grow and could not grow in the shade of the big tree. Many species in a forest community need these gaps and the sunlight they permit to fill their role in the forest ecosystem.
- While a big fallen tree is being recycled back into the forest floor to provide nutrients for a next generation of trees, it is also providing years of food and habitat for the insects and microbes that do the recycling.
- It also is providing habitat for many species of animal life that hide in the tangle of broken branches to protect them from predators.
- In areas where hurricanes are common, all native species are adapted to them. Non-native species in adjacent areas, which are not so adapted, therefore are kept out of the area by the recuring hurricanes. If the hurricanes stopped, they would be able to invade the former huricane zone, to the detriment of the native species there, as all introduced species are always destructive to native species that are not adapted to them.
- In areas where hurricanes are common, a significant portion of the yearly water supply comes from them. Without hurricanes there would be a water short-fall amounting to a major drought.
- The water shortfall could not be made up by simply causing extra ordinary rainstorms because the heavy downpour typical of hurricanes provides enough water all at once to flush out coastal ecosystems and rejuvenate them. Since this is an annual event, these coastal ecosystems are adapted to it and need it.
- Low-lying coastal areas in the tropics and subtropics are the richest, most diverse ecosystems on earth. Many such areas are under heavy threat from unrestricted development. Other areas are still relatively intact because the frequency of hurricanes discourages human occupation. If hurricanes wre no longer a factor, these fragile coastal ecosystems would soon be overrun by development from which they are now protected by the fact that hurricanes are common there.
From these few examples, it should be plain that a program to prevent hurricanes or weaken them to the point of any significant alteration of their major features, would be a disasterous mistake. Yet there is an increasing chorus of voices demanding that "something be done" about this important and much-needed phenomena and sooner or later "something" will be attempted. So now is the time for people who understand the necessity for hurricanes to start to organize to protect them from those who in their ignorance, would attempt to tamper with them.
Instead of waiting until it is too late and a program of hurricane supression is already underway, a movement to protect our atmosphere from well-meaning, but ignorant interference which could spell incaluable disaster should be begun now, while there is still time to gain strength before any serious damage is done to ability of the atmosphere to support the conditions upon which life depends.
Anyone interested in joining such a movement and helping to protect natural weather conditions, please contact me at: email@example.com . | <urn:uuid:9187a69b-891f-4a07-b1ed-e0222c90db36> | 2.890625 | 1,634 | Personal Blog | Science & Tech. | 36.084188 |
Apollo 11 Mission
Lunar Sample Overview
Apollo 11 basalt 10049. This sample has a mass of 193 grams and is up to 10 centimeters across. (NASA/Johnson Space Center photograph S76-25456.)
Apollo 11 breccia 10018. This sample has a mass of 213 grams and is up to 8 centimeters across. (NASA/Johnson Space Center photograph S75-30226.)
Apollo 11 carried the first geologic samples from the Moon back to Earth. In all, astronauts collected 22 kilograms of material, including 50 rocks, samples of the fine-grained lunar "soil," and two core tubes that included material from up to 13 centimeters below the Moon's surface. These samples contain no water and provide no evidence for living organisms at any time in the Moon's history. Two main types of rocks, basalts and breccias, were found at the Apollo 11 landing site.
Basalts are rocks solidified from molten lava. On Earth, basalts are a common type of volcanic rock and are found in places such as Hawai'i. Basalts are generally dark gray in color; when one looks at the Moon in the night sky, the dark areas are basalt. The basalts found at the Apollo 11 landing site are generally similar to basalts on Earth and are composed primarily of the minerals pyroxene and plagioclase. One difference is that the Apollo 11 basalts contain much more of the element titanium than is usually found in basalts on Earth. The basalts found at the Apollo 11 landing site range in age from 3.6 to 3.9 billion years and were formed from at least two chemically different magma sources.
Breccias are rocks that are composed of fragments of older rocks. Over its long history, the Moon has been bombarded by countless meteorites. These impacts have broken many rocks up into small fragments. The heat and pressure of such impacts sometimes fuses small rock fragments into new rocks, called breccias. Many fragments can be seen in the breccia photograph shown above. The rock fragments in a breccia can include both mare basalts as well as material from the lunar highlands. The lunar highlands are primarily a light-colored rock known as anorthosite, which consists primarily of the mineral plagioclase. It is very rare to find rocks on Earth that are virtually pure plagioclase. On the Moon, it is believed that the anorthosite layer in the highland crust formed very early in the Moon's history when much of the Moon's outer layers were molten. This stage in lunar history is known as the magma ocean. The plagioclase-rich anorthosite floated on the magma ocean like icebergs in the Earth's oceans.
Collecting Moon Rocks
This document describes the tools and procedures used by the Apollo astronauts to collect lunar samples. | <urn:uuid:1026ee00-d5d9-4252-898c-1889371fae94> | 4.0625 | 597 | Knowledge Article | Science & Tech. | 55.437399 |
The capercaillie probably became extinct in Britain in the mid-eighteenth century, largely due to the destruction of native woodland habitat.
In 1837 birds from Sweden were reintroduced into Perthshire, and by the early 1970s there were around 20,000 birds living there. However, urgent conservation action was needed when the population plummeted to just 1,000 in the early 1990s.
The rate of decline was so dramatic that by the mid 1990s they were expected to become extinct in the UK within 20 years. However, the bird has benefited from intensive conservation work, with a survey in 2008 indicating that the population had stabilised at around 2,000 individuals.
A number of possible causes of the decline are:
The capercaillie is a UK Biodiversity Action Plan (UKBAP) priority species and is on the Scottish Biodiversity List. It is listed on Annex 1 of the EC Birds Directive and is fully protected under the Wildlife and Countryside Act 1981, as amended, which also protects their leks.
The Scottish Natural Heritage (SNH) Species Action Framework’s Five-Year Implementation Plan 2007–2012 aims to increase the population of capercaillie in Scotland to 5,000 birds by 2010 and achieve an increase in the range of the capercaillie.
This framework has resulted in stakeholders, including the Forestry Commission, implementing guidelines when capercaillie or their active leks are found within a working area.
The Royal Society for the Protection of Birds (RSPB) reserves in Scotland manage all their key capercaillie habitats with the birds in mind.
There is much hope for the future recovery of this species, as we know a lot about them, and the habitat management vital for the species is being implemented jointly through industrial, environmental and governmental bodies. | <urn:uuid:fa2840d7-1ae0-4a58-a717-b2cbd19bd978> | 3.953125 | 380 | Knowledge Article | Science & Tech. | 34.094133 |
Where the Birds Are
The consequences of even one bird smashing into a plane's windshield or being pulled into an engine can be disastrous
Although collisions with birds in flight are infrequent causes of airplane accidents, the consequences of even one bird smashing into a plane's windshield or being pulled into an engine can be disastrous. That's why several scientists from various institutions recently joined forces with researchers at the Center for Conservation Research and Technology at the University of Maryland to figure out how to alert pilots about where the birds are. The researchers first fitted ten American white pelicans in Nevada with satellite transmitters. Then they tracked the birds' flights and compared the results with the weather and atmospheric conditions. Pelicans are soaring birds, and like glider pilots, they seek out "lift," usually in the form of thermals rising from the ground.
The study found that in the morning or when clouds kept the ground cool, birds on their way to and from their breeding colony and foraging grounds tended to fly at relatively low levels, as low as 100 feet above the ground. When thermals rose from the warmed earth later in the day, flying pelicans rose with the lift, as high as 10,000 feet. Their maximum limit apparently is 14,000 feet, which the birds can reach in a mere 10 minutes.
The team is optimistic that it can predict a day in advance how high various birds are likely to soar--and that pilots then can make sure to aim their planes higher than the birds, taking the information into account much as they do a weather forecast. The other species being investigated in the ongoing study include Swainson's hawks, turkey vultures, black vultures and red-tailed hawks. | <urn:uuid:f60dda88-2903-4a28-8cae-cb6128c3eb23> | 3.671875 | 346 | Knowledge Article | Science & Tech. | 42.022899 |
These are the Perl 6 Tablets, a comprehensive manual, aimed to support many different ways of learning. The content is nicely sorted and indexed and many links allow you to follow your interest freely. For a lightweight introduction, try the Perl 6 Tutorial. If its too easy, read the specs.
DISCLAIMER: This docs moved to tablets.perl6.org/ and no longer represent the current state.
Maybe this will vanish soon!
Tablet 2: Basic Syntax (Spaces, Comments, Literals, Quoting, Formatting)
Tablet 3: Variables (Sigils, Twigils, Assignment, Typing, Scopes)
Tablet 4: Operators (Comparison, Math, String, Logic, Metaops)
Tablet 5: IO (Command Line, Files, Sockets, Network, Misc.)
Tablet 6: Blocks (Conditions, Loops)
Tablet 7: Subroutines (Signatures, Modules)
Tablet 8: Objects (Classes, Roles)
Tablet 9: Regex (Rules, Grammars)
Tablet 10: Metaprogramming (Macros, DSL)
Appendix A: Index (all ops, builtins, methods and it terms, alphabetically ordered)
Appendix B: Tables, short reference (cheat sheets ans summary tables)
Appendix C: Cookbook (chunks of everyday Perl 5, translated into idiomatic Perl 6) | <urn:uuid:7b7ea713-6018-48de-a00d-f1f8c9aa8a32> | 2.796875 | 308 | Content Listing | Software Dev. | 41.321152 |
The function presented here is useful if:
- You've got one environment used to create many targets (too many to start messing with).
- The environment is configured differently for different platforms/compilers/etc.
- Some platforms/compilers/etc. need an additional source file to be compiled in order to work properly. This can be, for example, a replacement for a library that is not available on a certain platform.
This function wraps a given emitter with another emitter that adds another file to the source nodes.
Replaceable emitters (as of SCons 0.96.90):
PROGEMITTER - emitter for Program builder
SHLIBEMITTER - emitter for SharedLibrary builder
LIBEMITTER - emitter for Library builder
1 def add_file_to_emitter(env, emitter_name, file): 2 try: 3 original_emitter = env[emitter_name] 4 if type(original_emitter) == list: 5 original_emitter = original_emitter 6 except KeyError: 7 original_emitter = None 8 def emitter(target, source, env): 9 if original_emitter: 10 target, source = original_emitter(target, source, env) 11 return target, source + [file] 12 env[emitter_name] = emitter
In this example, the environment is searched for a library called somelib. If this library is not found, add_file_to_emitter is called to add somelibreplacement.c to every program built using the environment.
Changing the Emitter for StaticObject
If you want to change where a builder finds its C/C++ source files, you want to change the emitter for the StaticObject builder, aka Object. Unfortunately, there is no OBJEMITTER currently defined, but another way to do it is shown below.
1 # Assuming the BUILD_DIR is set to the location of the generated files 2 # and some other generated files are in OTHER_BUILD_DIR 3 def my_emitter(target, source, env): 4 ''' Tell SCons about the locations of some generated files. This could 5 be any emitter you want''' 6 if os.path.exists(source.path): 7 # The source file was generated in the local build directory 8 return (target, source) 9 altSrcName = source.abspath.replace(env['BUILD_DIR'] + os.sep, '') 10 if os.path.exists(altSrcName): 11 # The source file is in the source directory 12 return (target, altSrcName) 13 # Assume that the source file is in the other generated files build directory 14 altSrcName = "%s/%s%s" % (File('#'), env['OTHER_BUILD_DIR'], 15 source.path.replace(env['OTHER_BUILD_DIR'], '')) 16 return (target, altSrcName) 17 # This is the part where we override the emitter for the Object builder 18 from SCons.Tool import createObjBuilders 19 # Get the underlying builder objects 20 static_obj, shared_obj = createObjBuilders(env) 21 # Now SCons can find .cpp files in different locations 22 static_obj.add_emitter('.cpp', my_emitter) | <urn:uuid:2e9f7b28-7a26-446c-939d-417ec23f4210> | 3.078125 | 727 | Documentation | Software Dev. | 38.511165 |
These two images were taken just a few seconds apart, in the time it took to readjust the slide and snap the shutter. An Amoeba proteus can move at the rate of about 5 mm per minute. They move by extending and retracting pseudopods (false feet) over the surface. They have one disk shaped nucleus, and a contractile vacuole for expelling waste water. They are carnivores, in that they eat (engulf) bacteria and other small creatures.
Back To Image Index Page | <urn:uuid:aabf68e7-b20f-4413-a214-b886bcc831b9> | 2.796875 | 108 | Truncated | Science & Tech. | 48.347556 |
Sandia Develops Mini-Solar Cells
Sandia National Laboratory has developed tiny photovoltaic cells. Each is about 10 times thinner than conventional cells and can be integrated into clothing, turning its wearer into a mini-charger. The glitter-sized cells are 14-20 micrometers thick which is 10 times thinner than existing 6 X 6" solar modules. The team claims that they provide better performance, have a lower cost and are more efficient than those currently used.
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Posted by Sheila Franklin at December 28, 2009 9:20 PM | <urn:uuid:a71cd557-1e1e-4533-a99e-8a4f1dfebb10> | 2.78125 | 147 | Truncated | Science & Tech. | 48.902619 |
|00000STT, where STT is the type. If S == 1 then the piece is a slider. |
The POD base type of class Type.
This class uses the same internal type as Code to store the type bits. It even uses the same bits (the three least significant bits). All other bits are garanteed zero.
If the third bit is set then the object represents a sliding piece (bishop, rook or queen). If in addition the first bit is set it can moves like a bishop (bishop and queen), or if the second bit is set it can move like a rook (rook and queen). | <urn:uuid:f86c392c-f2ac-4576-8f5d-f838e8129e80> | 2.953125 | 131 | Documentation | Software Dev. | 78.776584 |
Any change in the balance between the quantity of energy absorbed compared to the amount emitted affects climate. The "greenhouse effect" is concerned with the infrared radiation given off by the earth. Part of this radiation is absorbed by the atmosphere, rather than being lost to space. The gases in the atmosphere that absorb infrared light primarily are water (H2), carbon dioxide (CO2), ozone (O3), nitrous oxide (NO2) and methane (CH4). The gases act as a sort of insulating blanket for the earth, in the same way they would act to lessen heat loss from a greenhouse, hence the name 'greenhouse effect'. It is estimated that the mean global surface temperature of the earth would be -25°C (-13°F) if not for the absorption of energy by carbon dioxide and water.
The concentration of water vapor in the atmosphere is higher than that of carbon dioxide. Consequently, most of this energy conservation is attributable to water. You can see this effect when you look at how temperature drops less on nights with heavy cloud cover as opposed to clear skies or when you consider how large the temperature difference between day and night is in places with lower relative humidity, like the desert.
Although the concentration of carbon dioxide in the atmosphere is low (~375 ppm in 2005), it has been increasing appreciably over time. A century ago, the carbon dioxide concentration was less than 300 ppm. Human activites are accountable for this increase, including consumption of fossil fuels and extensive clearing of land (less carbon dioxide can be consumed by photosynthesis). Changes in the levels of carbon dioxide in the atmosphere are associated with changes in the earth's climate. | <urn:uuid:f07a471a-f709-406b-8d72-6e50a6299cce> | 4.21875 | 336 | Knowledge Article | Science & Tech. | 39.017308 |
A Scientist’s Blog from the Arctic:
By Steve Zack, Wildlife Conservation Society
Unraveling Mysteries of Migration
12 Jul 2011
“We have the Japan bird over here, and the China bird is nearby,” Wildlife Conservation Society
field assistant Lizzie Goodrick states confidently into the walkie-talkie. She is reporting to our other field assistants monitoring birds near our remote field camp on the Ikpikpuk River on Alaska’s North Slope. The birds in question — small, long-billed shorebirds called dunlin — have indeed been photographed in those countries last winter and have returned to breed again where we captured, banded, and applied geolocators to them, here in our Ikpikpuk site.
Steve Zack of the Wildlife Conservation Society blogs from the Arctic for Yale Environment 360. The first in a series.
The Ikpikpuk camp, located on the far western edge of the Teshekpuk Lake Special Area in the U.S. National Petroleum Reserve — Alaska, is a 1 1/2 -hour flight by bush plane from near the Prudhoe Bay oilfields to the east, and 70 miles from Barrow to the west. We are in the heart of Arctic Alaska’s biggest wetland complex, surrounded by a truly international assemblage of breeding birds. Birds from every continent, and from every ocean, migrate to Arctic Alaska to breed in the brief summer. And with new technologies and international collaborations, we are teasing apart the geographic details of these birds’ remarkable migratory lives.
Geolocators are the newest high-tech toy to track migratory birds. Consisting of a computer chip, a battery, and a light sensor bound together in a very small package, geolocators gather day length and sunrise time information on a daily basis, revealing the location (latitude and longitude) of a migratory bird over the course of a year. Geolocators do not transmit, and must therefore be recovered. Taking advantage of the site-fidelity of breeding birds gives us the opportunity to retrieve the geolocator a year after applying it.
For dunlins, the tiny geolocator is glued to a band around the leg. Last year at Ikpikpuk, we applied several geolocators to breeding dunlins after capturing them with a bow trap sprung over incubating birds on their tundra nests. Because we also adorn these birds with color “flags” (a band with a stiff flange that sticks out from the leg) and because these flags are color-coded to indicate the region where banded (in this case, green for Alaska), bird photographers around the world can see a flagged bird, photograph it, and identify where it nests. The green flag on our dunlin also had alpha-numeric coding indicating the individual identification; thus “EEK” was photographed in Japan and, with the assistance of the U.S. Fish and Wildlife Service, we saw the picture of our bird in its winter home. Incredibly, another photograph of an Ikpikpuk dunlin came to us from China.
A dunlin, known as ‘EEK,’ with a geolocator on its right leg.
Lizzie and her partner, John Diener, captured EEK for the second time in two years at Ikpikpuk and retrieved the geolocator. I am taking this and another dunlin geolocator back with me to send to our U.S. Fish and Wildlife colleagues. They will download the data from the geolocators as part of a collective, continent-wide effort to determine where key Arctic shorebird species are wintering, and learn of their migratory pathways to and from the Arctic.
That’s not all. We also flagged and color-banded several semipalmated sandpipers at Ikpikpuk to begin to understand adult survivorship patterns, as part of a continent-wide effort in the Arctic. As expected, most of those banded birds returned this summer to Ikpikpuk to breed, affording us the opportunity to monitor who is back, and who is new to our plots. Semipalmated sandpipers winter on shorelines of South America, quite a journey for a bird that weighs less than an ounce.
Finally, I sighted a female bar-tailed godwit with an orange flag, indicating that it had been banded in Australia. Remote is a relative term, I guess: Ikpikpuk is a veritable gathering ground of birds with fancy jewelry — color bands and flags — from all over the globe. I flew from Oregon, and was surrounded by birds that had arrived from Japan, China, South America, and Australia.
And then there was the champion migrator, the Arctic Tern, which defended its nest by swooping down and striking my head when I got too close. These birds make an annual round-trip from the Arctic to the Antarctic, covering more than 40,000 miles.
The stunning yellow-billed loon that was nesting just across the river likely flew in from the Yellow Sea. The lone Smith’s longspur, singing nonstop because it had no partner to court, winters in the American Midwest. The pomerine jaegers stopped to breed at Ikpikpuk this year, as we had abundant brown lemmings; these birds winter in tropical oceans worldwide, stealing food from albatross and petrels. The male pectoral sandpipers, all puffed up with their chesty flight displays, will soon leave the chick-rearing to females and return to their wintering grounds in southern South America. Finally, graceful tundra swans at Ikpikpuk may be among the swans I see in winter by my home in Portland, Oregon. We are migrants all, drawn to Arctic Alaska.
Most of our migratory Arctic shorebirds are thought to be declining, some — such as the semipalmated sandpipers — dramatically so. We are only beginning to understand where in their expansive migratory worlds these birds are facing threats, such as deforestation and development, causing their declines. New technologies like geolocators, as well as satellite transmitters for larger birds, are revealing the details of migratory movements of these and other birds for the first time. With that information, we can look at their migratory geographies and learn of the threats and challenges these birds are facing. Their conservation is truly a global challenge.
A few years ago, my WCS colleague, Joe Liebezeit, and I traveled to South Korea to assess whether some Arctic breeders, like dunlin and the bar-tailed godwit, were infected by avian flu amid a huge outbreak of millions of poultry. There we saw, up close, one of the major threats to migratory birds in the Asian flyway: the new Saemangeum Sea Wall, more than 40 miles long, which has closed off the tidal flow to the most important wetland for migratory birds in all of Asia. As we worked with Koreans to gain research permission, I joked that we wanted to work with “our” birds while they were studying “their” birds. They nodded in amusement. If we could recognize that these and other migratory birds are indeed our collective responsibility, perhaps we could help make migration less perilous for birds in our changing world.
19 July 2011: Tracking the Impact of Oil Development on Wildlife
26 July 2011: A Place for Wildlife in the National Petroleum Reserve
2 August 2011: As Climate Warms, a Shifting Landscape for Wildlife | <urn:uuid:af16925f-0e60-4656-8cca-8e6618e9f04e> | 3.171875 | 1,598 | Nonfiction Writing | Science & Tech. | 41.787847 |
Currently, there is much emphasis on the study of magnetic properties of materials. While magnets date back to ancient times, new techniques have made it possible to use magnets in a wide variety of applications, as exemplified by flexible magnets. Perhaps the most common place to encounter flexible magnets is the refrigerator door in the form of flexible sheet refrigerator magnets.
The common flexible sheet refrigerator magnet (RM) has a complex, ingenious magnetic structure. The field lines in the RM are U-shaped; therefore, most of the magnetic field extends from the back of the magnet and very little magnetic field from the front. A RM can essentially be thought of as an array of very small horseshoe magnets. The magnetic field structure therefore comprises a striped pattern of alternating north and south poles on the brown, unprinted side of the RM, with a typical stripe width of 1-2 mm. This unusual magnetic topography can be used for a number of interesting demonstrations and experiments.
Figure 1. (top) Cross-section of a flexible sheet refrigerator magnet and (bottom) its analogy to an array of horseshoe magnets.
RMs are composite materials, typically containing magnetic strontium ferrite, SrFe12O19, particles dispersed in the elastomer Hypalon. Strontium ferrite may be thought of as having the general formula MO-6Fe2O3, where M is a divalent metal cation. The metal M2+ ions (such as Sr2+ or Ba2+) substitute for O2- ions in the close-packed oxygen layers. The Fe3+ ions are arranged throughout this lattice, having oxygen coordination numbers of 4, 5, or 6.
Figure 2. Unit cell model of strontium ferrite built using the Solid State Model Kit.
Figure 3. Chemical structure of the elastomer Hypalon.
During the manufacture of RMs, an array of permanent magnets forms the magnetic stripes as a sheet of ferrite/Hypalon passes by the array. The magnetic fields from the array align the magnetic dipoles of the ferrite particles, resulting in the striped pole pattern. Channeling the magnetic field to the back of the magnet puts the maximum amount of this field to work holding the RM onto a metal surface such as a refrigerator door. The RM poles induce temporary poles of opposite polarity in the refrigerator door, enabling the RM to stick to the door. This site explores RM-based experiments that use these unusual striped structures to demonstrate a number of principles.
Patrick Doolan has constructed a magnetic worm gear system using refrigerator magnets. The alternating north and south magnetic fields act as the teeth of a gear. The gear system can operate without physical contact between the two gears.
Different materials respond to applied stresses in different ways. How a material will respond depends on the arrangement of atoms in the material and how these atoms are bonded together. We have found that flexible sheet refrigerator magnets can be used to show macroscopically how salts and metals respond to an applied stress. | <urn:uuid:c366aa1e-b0e5-466a-828f-731a83ed9471> | 3.03125 | 612 | Knowledge Article | Science & Tech. | 40.741129 |
Friday, April 20, 2012 - 17:30 in Earth & Climate
On the eve of Earth Day, find out which of the world's forests are on the brink.
- Mangroves among the most carbon-rich forests in the tropicsMon, 4 Apr 2011, 17:10:49 EDT
- Forest mortality and climate change: The big pictureSun, 9 Sep 2012, 16:03:11 EDT
- Forest Service unveils first comprehensive forecast on southern forestsTue, 17 May 2011, 13:34:54 EDT
- Hotspots of carbon confusion in Indonesia threaten to warm the world more quicklyMon, 28 Feb 2011, 10:05:56 EST
- If a tree falls in the forest, and no one is around to hear it, does climate change?Thu, 12 Jun 2008, 17:21:51 EDT | <urn:uuid:4ecdc302-231c-4dd8-b584-194742e64a37> | 3.171875 | 173 | Content Listing | Science & Tech. | 44.047335 |
CRAZY CLOUDS: The newly discovered Undulatus Asperatus!
Last week, several viewers submitted photos to the WDRB Weather Facebook Page of a strange and fascinating cloud feature the appeared across the area.
Now known as Undulatus Asperatus, until recently, this cloud was largely undocumented.
These clouds are characterized by turbulent, but soft undulating wave motions. It kind of looks like the surface of the ocean, only looking at it from below.
First photographed at Cedar Rapids in Iowa, U.S. in 2006, undulatus asperatus has since been spotted in many parts of the world including right here in Kentuckiana.
In fact the cloud has been documented enough that the Cloud Appreciation Society (CAS) has submitted it to the Royal Meteorological Society for consideration for the next edition of the International Cloud Atlas.
If the new formation is accepted, it will be the first new entry to the atlas since 1951, and one of the more exciting ones, because not only do undulatus asperatus make the sky look like aliens are coming, but they’d also be the first classification discovered through crowd sourcing—average people taking pictures of new clouds and lobbying to have them recognized.
According to Wikipedia:
Undulatus asperatus (or alternately, asperatus) is a cloud formation, proposed in 2009 as a separate cloud classification by the founder of the Cloud Appreciation Society. The name translates approximately as roughened or agitated waves.
The clouds are most closely related to undulatus clouds. Although they appear dark and storm-like, they tend to dissipate without a storm forming. The ominous-looking clouds have been particularly common in the Plains states of the United States, often during the morning or midday hours following convective thunderstorm activity.
As of June 2009, the Royal Meteorological Society is gathering evidence of the type of weather patterns in which undulatus asperatus clouds appear, so as to study how they form and decide whether they are distinct from other undulatus clouds.
Here's a cool time lapse video of the phenomena for your viewing pleasure...
Meteorologist Jeremy Kappell | <urn:uuid:57fe3632-49f1-4e06-967a-01d4b2d073c1> | 2.765625 | 454 | Personal Blog | Science & Tech. | 30.171254 |
HYDROZOA, a class of Ccelenterata (q.v.) embracing the polyps, all of which bear a general resemblance to Hydra (q.vd. There are two alternating generations, that is, (1) the sessile asexual polyp, which gives rise to (2) a jelly fish or medusa. The hydroid polyp is like hydra, a two-layered vase-like sac, with a circle of tentacles around the mouth. This gives off by a budding process a bell-shaped medusa, which is much more highly organized than the polyp, having a well-developed digestive and nervous system, and sense-organs (eyes and ears, or otocysts). They have the peculiar cells known as Nematocysts (q.v.), which are numer ous in the tentacles, and secrete a fluid resem bling formic acid, which may be exploded with danger to their enemies. The Hydrozoa are cnidaria capable of producing two different types of individual, the polyp and the medusa. (See Goaco). Each of these develops from the egg through the blastula, porenchymula, gastrula and actinuala. The Hydrozoa are at
present divided into seven orders, the most im portant of which are, besides Hydraria repre sented by hydra: the Hydrocorallince, of which Millepora (q.v.) is the type; the Tubularia, comprising Hydractinia, Tubularia, etc.; the Campanurari, of which Campanularia, Clytia and °bolo are examples. Near this group be longs the extinct order of Graptolites, which were floating forms living in the Paleozoic seas. The last order (Stphonophora) comprises the Portuguese man-of-war (q.v.) and other forms, which are beautiful transparent pelagic animals, very brightly colored and highly specialized. An interesting type is the Actinozoa and the subclasses Zoontharia and Aleyosaria. Consult Hickson, and Ctenophora' (in (Cambridge Natural History,' Vol. I, 1906). See JELLYFISH ; POLYP. | <urn:uuid:0b6a63cf-9b4c-4571-a9f7-d9428518eea0> | 2.90625 | 474 | Knowledge Article | Science & Tech. | 44.067456 |
|GLib Reference Manual|
Compiling the GLib package
Compiling the GLib Package — How to compile GLib itself
On UNIX, GLib uses the standard GNU build system, using autoconf for package configuration and resolving portability issues, automake for building makefiles that comply with the GNU Coding Standards, and libtool for building shared libraries on multiple platforms. The normal sequence for compiling and installing the GLib library is thus:
The standard options provided by GNU autoconf may be passed to the configure script. Please see the autoconf documentation or run ./configure --help for information about the standard options.
The GTK+ documentation contains further details about the build process and ways to influence it.
Before you can compile the GLib library, you need to have various other tools and libraries installed on your system. The two tools needed during the build process (as differentiated from the tools used in when creating GLib mentioned above such as autoconf) are pkg-config and GNU make.
is a tool for tracking the compilation flags needed for
libraries that are used by the GLib library. (For each
library, a small
.pc text file is
installed in a standard location that contains the compilation
flags needed for that library along with version number
information.) The version of pkg-config
needed to build GLib is mirrored in the
on the GTK+ FTP
The GTK+ makefiles will mostly work with different versions of make, however, there tends to be a few incompatibilities, so the GTK+ team recommends installing GNU make if you don't already have it on your system and using it. (It may be called gmake rather than make.)
GLib depends on a number of other libraries.
libiconv library is needed to build GLib if your
system doesn't have the
function for doing conversion between character
encodings. Most modern systems should have
iconv(), however many older systems lack
iconv() implementation. On such systems,
you must install the libiconv library. This can be found at:
If your system has an
iconv() implementation but
you want to use libiconv instead, you can pass the
--with-libiconv option to configure. This forces
libiconv to be used.
Note that if you have libiconv installed in your default include
search path (for instance, in
don't enable it, you will get an error while compiling GLib because
iconv.h that libiconv installs hides the
If you are using the native iconv implementation on Solaris instead of libiconv, you'll need to make sure that you have the converters between locale encodings and UTF-8 installed. At a minimum you'll need the SUNWuiu8 package. You probably should also install the SUNWciu8, SUNWhiu8, SUNWjiu8, and SUNWkiu8 packages.
The native iconv on Compaq Tru64 doesn't contain support for UTF-8, so you'll need to use GNU libiconv instead. (When using GNU libiconv for GLib, you'll need to use GNU libiconv for GNU gettext as well.) This probably applies to related operating systems as well.
The libintl library from the GNU gettext
package is needed if your system doesn't have the
gettext() functionality for handling
message translation databases.
A thread implementation is needed, unless you want to compile GLib without thread support, which is not recommended. The thread support in GLib can be based upon several native thread implementations, e.g. POSIX threads, DCE threads or Solaris threads.
In addition to the normal options, the configure script in the GLib library supports these additional arguments:
configure [[--enable-debug=[no|minimum|yes]]] [[--disable-gc-friendly] | [--enable-gc-friendly]] [[--disable-mem-pools] | [--enable-mem-pools]] [[--disable-threads] | [--enable-threads]] [[--with-threads=[none|posix|dce|win32]]] [[--disable-included-printf] | [--enable-included-printf]] [[--disable-visibility] | [--enable-visibility]] [[--disable-gtk-doc] | [--enable-gtk-doc]] [[--disable-man] | [--enable-man]]
Turns on various amounts of debugging support. Setting this to 'no'
disables g_assert(), g_return_if_fail(), g_return_val_if_fail() and
all cast checks between different object types. Setting it to 'minimum' disables only cast checks. Setting it to 'yes' enables
The default is 'minimum'.
Note that 'no' is fast, but dangerous as it tends to destabilize
even mostly bug-free software by changing the effect of many bugs
from simple warnings into fatal crashes. Thus
--enable-debug=no should not
be used for stable releases of GLib.
By default, and with
as well, Glib does not clear the memory for certain objects before they
are freed. For example, Glib may decide to recycle GList nodes by
putting them in a free list. However, memory profiling and debugging tools like Valgrind work better if an
application does not keep dangling pointers to freed memory (even
though these pointers are no longer dereferenced), or invalid pointers inside
uninitialized memory. The
--enable-gc-friendly option makes Glib clear
memory in these situations:
When shrinking a GArray, Glib will clear the memory no longer available in the array: shrink an array from 10 bytes to 7, and the last 3 bytes will be cleared. This includes removals of single and multiple elements.
When growing a GArray, Glib will clear the new chunk of memory. Grow an array from 7 bytes to 10 bytes, and the last 3 bytes will be cleared.
The above applies to GPtrArray as well.
When freeing a node from a GHashTable, Glib will first clear the node, which used to have pointers to the key and the value stored at that node.
When destroying or removing a GTree node, Glib will clear the node, which used to have pointers to the node's value, and the left and right subnodes.
Since clearing the memory has a cost,
--disable-gc-friendly is the default.
Many small chunks of memory are often allocated via collective pools
in GLib and are cached after release to speed up reallocations.
For sparse memory systems this behaviour is often inferior, so
memory pools can be disabled to avoid excessive caching and force
atomic maintenance of chunks through the
g_free() functions. Code currently affected by
GList, GSList, GNode, GHash allocations. The functions g_list_push_allocator(), g_list_pop_allocator(), g_slist_push_allocator(), g_slist_pop_allocator(), g_node_push_allocator() and g_node_pop_allocator() are not available
GMemChunks become basically non-effective
GSignal disables all caching (potentially very slow)
GType doesn't honour the
n_preallocs field anymore
the GBSearchArray flag
G_BSEARCH_ALIGN_POWER2 becomes non-functional
Do not compile GLib to be multi thread safe. GLib
will be slightly faster then. This is however not
recommended, as many programs rely on GLib being
multi thread safe.
Specify a thread implementation to use.
'posix' and 'dce' can be used interchangeable to mean the different versions of Posix threads. configure tries to find out, which one is installed.
'none' means that GLib will be thread safe,
but does not have a default thread
implementation. This has to be supplied to
g_thread_init() by the programmer.
By default the configure script will try
to auto-detect whether the C library provides a suitable set
printf() functions. In detail,
configure checks that the semantics of
snprintf() are as specified by C99 and
that positional parameters as specified in the Single Unix
Specification are supported. If this not the case, GLib will
include an implementation of the
These options can be used to explicitly control whether
an implementation fo the
should be included or not.
By default, GLib uses ELF visibility attributes to optimize
PLT table entries if the compiler supports ELF visibility
attributes. A side-effect of the way in which this is currently
implemented is that any header change forces a full
recompilation, and missing includes may go unnoticed.
Therefore, it makes sense to turn this feature off while
doing GLib development, even if the compiler supports ELF
visibility attributes. The
option allows to do that.
By default the configure script will try
to auto-detect whether the
gtk-doc package is installed. If
it is, then it will use it to extract and build the
documentation for the GLib library. These options
can be used to explicitly control whether
gtk-doc should be
used or not. If it is not used, the distributed,
pre-generated HTML files will be installed instead of
building them on your machine.
By default the configure script will try
to auto-detect whether xsltproc
and the necessary Docbook stylesheets are installed. If
they are, then it will use them to rebuild the included
man pages from the XML sources. These options can be used
to explicitly control whether man pages should be rebuilt
used or not. The distribution includes pre-generated man | <urn:uuid:dcc107a1-162a-4987-8dd5-a2ec12b78bad> | 3.265625 | 2,114 | Documentation | Software Dev. | 41.801166 |
(gdbint.info) Overall Structure
GDB consists of three major subsystems: user interface, symbol
handling (the "symbol side"), and target system handling (the "target
Ther user interface consists of several actual interfaces, plus
The symbol side consists of object file readers, debugging info
interpreters, symbol table management, source language expression
parsing, type and value printing.
The target side consists of execution control, stack frame analysis,
and physical target manipulation.
The target side/symbol side division is not formal, and there are a
number of exceptions. For instance, core file support involves symbolic
elements (the basic core file reader is in BFD) and target elements (it
supplies the contents of memory and the values of registers). Instead,
this division is useful for understanding how the minor subsystems
should fit together.
The Symbol Side
The symbolic side of GDB can be thought of as "everything you can do
in GDB without having a live program running". For instance, you can
look at the types of variables, and evaluate many kinds of expressions.
The Target Side
The target side of GDB is the "bits and bytes manipulator". Although
it may make reference to symbolic info here and there, most of the
target side will run with only a stripped executable available - or
even no executable at all, in remote debugging cases.
Operations such as disassembly, stack frame crawls, and register
display, are able to work with no symbolic info at all. In some cases,
such as disassembly, GDB will use symbolic info to present addresses
relative to symbols rather than as raw numbers, but it will work either
"Host" refers to attributes of the system where GDB runs. "Target"
refers to the system where the program being debugged executes. In
most cases they are the same machine, in which case a third type of
"Native" attributes come into play.
Defines and include files needed to build on the host are host
support. Examples are tty support, system defined types, host byte
order, host float format.
Defines and information needed to handle the target format are target
dependent. Examples are the stack frame format, instruction set,
breakpoint instruction, registers, and how to set up and tear down the
stack to call a function.
Information that is only needed when the host and target are the
same, is native dependent. One example is Unix child process support;
if the host and target are not the same, doing a fork to start the
target process is a bad idea. The various macros needed for finding the
registers in the `upage', running `ptrace', and such are all in the
Another example of native-dependent code is support for features that
are really part of the target environment, but which require `#include'
files that are only available on the host system. Core file handling
and `setjmp' handling are two common cases.
When you want to make GDB work "native" on a particular machine, you
have to include all three kinds of information.
automatically generated byinfo2html | <urn:uuid:95cab212-c8f6-4610-a1c0-224930e5b10f> | 3.171875 | 678 | Documentation | Software Dev. | 34.678966 |
Some very early testing of fluorescence imaging in our optical tweezers instrument. A 10 kb long piece of DNA (ca 3 um long when stretched) is held between two optically trapped microspheres. The DNA is coated with a fluorescent dye (SYBR-gold) which is exited by a 488 nm blue laser and the fluorescence signal is collected with a CCD camera looking through a narrow-band filter centered on the emission spectrum of SYBR-gold.
At around 1:10 in the video there's a double-tether (two DNA-molecules between the beads). We don't want that but there is not much that we can do about it, except discard the data. At the very end there's an image of QDots on the coverglass surface.
A ~48 000 base-pair long (ca 16 um) piece of DNA is stretched between two optically trapped ca 2 um diameter polystyrene beads. Bright-field real-time view through a 100x microscope. Scale-bar in microns on the right.
Some promising results yesterday with trying to stretch DNA molecules. The molecule is attached between two microspheres, and we are actively moving the smaller sphere while the force acting on the bigger sphere is being measured. The image and video shows the view through a 100x microscope objective on the optical tweezers instrument I am building. Towards the end you can see the construct breaking in two stages, so that probably means there were two molecules of DNA between the beads and not one as intended. This is a control experiment and will hopefully set the stage for bigger and better things to come... | <urn:uuid:7c4fc00d-50ed-44d8-bf8c-79f853f75561> | 3.046875 | 336 | Personal Blog | Science & Tech. | 60.089932 |
by Jeffrey M. Perkel
Today’s mass spectrometers are faster, more sophisticated and more sensitive than ever. Yet if the molecules that are fed into these machines aren’t charged, the machine is as blind as a bat.
That’s because mass spectrometers don’t actually measure a molecule’s mass, but rather its mass-to-charge ratio (m/z). Given a molecule’s m/z value and its charge state, researchers can compute the mass, but to do that the molecule first must be vaporized and ionized.
“If you don’t ionize or you can’t ionize, then you can’t do mass spectrometry,” says mass spec expert R. Graham Cooks, Professor of Chemistry at Purdue University. Naturally, then, ionization sources are critical components of any mass spec setup. So critical, in fact, that two of the most popular life-science ionization techniques, ESI (electrospray ionization) and MALDI (matrix-assisted laser-desorption ionization), won their inventors the Nobel Prize in Chemistry in 2002.
ESI and MALDI revolutionized biological mass spectrometry, and especially proteomics, because they are “soft”: They ionize biomolecules without smashing them to pieces in the process. Yet they are not the only ionization methods available to life-science researchers today. There are APCI and APPI, DESI and DART and LAESI, CI and EI and more. “Here’s the deal with ionization methods,” says Neil Kelleher, the Walter and Mary Elizabeth Glass Professor in the Life Sciences at Northwestern University, “it’s a bit of an alphabet soup—lots of acronyms for lots of new methods.”
In part, that’s because researchers still have not figured out how to overcome two fundamental issues: sample preparation and ionization efficiency. Sample ionization, and transmission of those ions into the mass spectrometer, are “the most inefficient parts of the [mass spec] process,” says Steve Smith, senior director of product management for mass spectrometry at Waters. Cooks notes that dozens of new ionization techniques have been developed in the past five years. “That wouldn’t be true if there weren’t still problems [with existing methods].” Fortunately, the alphabet soup of ionization approaches has sufficient diversity to handle just about any class of molecule.
MALDI and ESI
Mass spec ionization techniques can be subdivided into several categories. Most interface with chromatographic methods, including both liquid chromatography (e.g., ESI, nanoESI, APPI and APCI) and gas chromatography (e.g., EI and CI). Others handle surface-based samples that are either processed off-line (e.g., MALDI) or analyzed directly without preparation, that is, in situ, (e.g., DESI, DART and LAESI).
MALDI (available, for instance, in Bruker Daltonics’ microflex™, autoflex™ speed and ultrafleXtreme™ series of instruments) is most appropriate for use with a two-dimensional gel electrophoresis (2DGE) workflow, in which protein spots are excised from the gel, processed and spotted onto MALDI plates for MS analysis.
In MALDI, a sample is mixed with a UV-absorbing crystalline matrix material, such as 2,5-dihydroxybenzoic acid and alpha-cyano-4-hydroxycinnamic acid, and spotted onto a metal target plate. The plate is then inserted into the MS instrument, where it is placed in a vacuum (though an atmospheric-pressure variant, AP/MALDI, is also available from MassTech) and hit with a UV laser. The matrix absorbs the irradiation, heating and volatilizing the sample and ionizing it at the same time.
Generally, MALDI imparts a +1 charge to proteins (with an occasional +2 or +3, as well), which both simplifies and complicates downstream analysis. On one hand, mass calculation is trivial, as m/z = m for z of +1. But the +1 charge also makes it more difficult to analyze intact proteins, as their large size pushes their m/z values outside the “sweet spot” of most mass spectrometers.
The +1 ions also do not respond well to fragmentation, says Kelleher, making MALDI a tougher ionization source for use in tandem mass spec applications (such as post-translational modification analysis and peptide sequencing).
ESI, in contrast, produces a range of charged species for each molecule: +2, +3, +4 and so on. That kaleidoscope of ions complicates mass analysis but greatly enables tandem mass spec work. And, because it is a liquid-based method, ESI is compatible with the chromatographic separations so often used in biosample analyses, from ultra-fast UPLC to low-flow nanoLC.
Kelleher recently published a study in which he used top-down proteomics (an approach in which proteins are analyzed intact, rather than as peptides, to study their post-translational modifications) to identify and characterize some 3,000 protein species produced from 1,043 human genes. The study was driven by a pair of high-end ESI-powered mass spectrometers coupled to a “nanocapillary reversed-phase liquid chromatography” system, including a Thermo Scientific 12-Tesla LTQ FT Ultra Fourier-transform ion cyclotron resonance MS and a Thermo Scientific Orbitrap Elite.
John Yates, a mass spectrometrist at the Scripps Research Institute in La Jolla, Calif., also favors ESI-based mass specs, mostly Orbitraps. His lab, though, tends to build its own low-flow sources rather than using off-the-shelf solutions. “Since we make our own columns, it’s easier to use our own source than to try to fit to commercial ones,” he says.
Yates’ lab recently acquired a new Thermo Scientific Q Exactive, a hybrid quadrupole-Orbitrap instrument. Featuring high mass resolution and accuracy and fast scan speeds, the instrument, he says, “is smoking.”
A class issue
According to Smith, the key variable to consider in choosing an ionization source is the kind of molecule a researcher is looking for. “Each method is good for molecules of a certain polarity,” he says.
ESI most effectively ionizes relatively polar molecules, especially proteins and peptides, says Keith Waddell, director of LC-MS marketing at Agilent Technologies. (The company offers a custom form of ESI, called Agilent JetStream, which uses heated nitrogen gas to concentrate and direct the electrospray into the MS inlet, increasing sensitivity five- to 10-fold, Waddell says.)
For less polar metabolites and other compounds, such as steroids, researchers can consider ESI variants such as APCI (atmospheric pressure chemical ionization) and APPI (atmospheric pressure photoionization). APCI uses an ion molecule reaction to impart charge, whereas APPI uses light energy to do the same thing.
Waters offers as a standard component of its mass specs a dual-mode ionization source called ESCI, which rapidly alternates between ESI and APCI modes.
For highly nonpolar molecules, Waddell says, researchers should consider gas chromatography (GC)-based approaches instead. GC most commonly employs one of two ionization methods: EI (electron impact) or CI (chemical ionization). In EI, molecules are ionized by collision with electrons produced by a heated filament, generally by “chipping off an electron” and producing a positive charge, says Waddell. CI does the same thing, but in the presence of a gas such that the gas becomes charged; collision with the gas ions ionizes the sample instead.
Surface-based ambient ionization
According to Cooks, one of the key issues in biological mass spectrometry today is sample preparation. “Mass spectrometrists are not spending their time with the samples in the instrument, they spend most of their time on chromatography,” he says.
This is especially true if researchers are interested in radically different classes of molecules, as an extraction method that works for, say, sugars, will not capture lipids. Many researchers, Cooks says, would prefer to analyze samples directly—that is, to read their molecular profiles without all the sample preparation and chromatographic acrobatics. “Put simply, the desire people have is the desire to do mass spectrometry in situ,” he says.
Enter ambient ionization methods, which enable researchers to analyze the chemistry of biological samples with little or no sample preparation by essentially blasting ions off their surfaces.
According to Cooks, some 40 surface-based ambient ionization approaches have been described in the literature in the past five years or so, and four have been commercialized. One, developed by Cooks and coworkers, is DESI (desorption electrospray ionization).
Commercialized by Prosolia for instruments from AB Sciex, Agilent Technologies, Bruker Daltonics, Leco, Thermo Scientific and Waters, DESI essentially directs a beam of solvent at a tissue sample on a slide. As the solvent pools, it extracts some of the molecular components of the sample, which then splash up into the MS inlet upon subsequent solvent impacts, yielding an electrospray.
According to Cooks, ambient interface methods can be used in one of two ways: “point-and-shoot” and MS imaging. In the former case, the goal is to take a snapshot of the sample’s molecular profile, for instance, to test a food sample for contaminants; in the latter, researchers collect spectra at various points across a sample (that is, pixel by pixel).
The advantage of MS imaging is that instead of simply quantifying the bulk abundance of various compounds in a sample, researchers can produce a kind of spatially resolved map, or image, of the sample’s molecular composition. Vanderbilt University mass spec expert Richard Caprioli, who perfected the use of MALDI as an imaging ionization method, has compared the resulting images to the red/green/blue channels of a digital image, except that in this case, each “channel” corresponds to a single metabolite.
One disadvantage of ambient ionization methods, says Cooks, is sensitivity: Because there is no sample preparation and enrichment, molecules of interest may tend to be lost amidst the signal produced by far more abundant, but irrelevant, compounds. Furthermore, ion suppression, in which one molecule inhibits the ionization of another (thereby limiting sensitivity) can be particularly problematic in such experiments, he says.
MALDI imaging is not actually an ambient approach, as it occurs in a vacuum and requires sample preparation. Nevertheless, it is an alternative, complementary imaging approach. Kelleher recently has begun using that approach (in which MALDI matrix is sprayed on top of a tissue slice on a MALDI target plate) in his top-down work, getting a first-pass surface analysis of potential biomarker molecules using MALDI imaging, followed by a more detailed, “grind-and-find” ESI MS-based analysis to actually characterize those proteins in detail.
“There’s a good link between top-down proteomics and MALDI-based imaging,” Kelleher notes. “When people do MALDI imaging they do often direct analysis, top-down—they don’t digest.”
Another recently introduced imaging approach is LAESI (laser ablation electrospray ionization), commercialized by Protea Biosciences as the LAESI DP-1000 Ionization System. Developed by Akos Vertes at George Washington University, LAESI uses a mid-IR laser (2,940 nm) to excite the O-H bonds in water, acting as a kind of endogenous matrix. Gas-phase particles are created from the ablation of the sample and then ionized through interactions with an electrospray ionization plume, all at ambient pressure.
According to Alessandro Baldi, vice president and general manager at Protea Biosciences, the advantage of this approach compared with MALDI imaging is that it requires no matrix, simplifying the experiment and producing cleaner spectra, especially in the low m/z range. It also produces multiply charged ions, as does ESI. But perhaps most importantly, he says, LAESI allows researchers to take three-dimensional molecular profiles by repeatedly digging into a sample and reanalyzing it.
“LAESI can scratch the surface and then go deeper,” Baldi says. “So it’s a difference between seeing what is on the surface versus what is inside the biological entity. And this can be performed directly on living cells.”
The technique produces pixels approximately 200 microns in diameter and about 50 microns deep, Baldi says. The LAESI DP-1000, which was named one of the top 10 innovations of 2011 by The Scientist magazine , costs about $250,000.
Before you buy
By all accounts, it is relatively simple to install a new ionization source—a matter of removing and installing a few bolts, plus electrical and gas connections.
“These are very interchangeable,” says Iain Mylchreest, vice president of research and development for chromatography and mass spectrometry products at Thermo Scientific. “Typically they are small ‘source housings’ or probes that bolt on to the front of the instrument. None requires any kind of service intervention. It can take minutes to switch, for instance, from ESI to APCI.”
Expect to pay less than $30,000 or so for most standard sources (e.g., APCI and APPI), Waddell says. Third-party sources may cost more, but the bigger issue is physical compatibility: Instrument architecture varies among vendors and across instrument classes (e.g., ion trap, time-of-flight (TOF), quadrupole), so you’ll need to make sure your desired ion source can interface with the instrument in your lab.
And don’t be surprised if you need to purchase another ionization source in the years ahead. As research priorities change, it’s always possible that you’ll find yourself studying a new class of molecules that just doesn’t respond well to the technologies you have on hand.
“There’s no universal ionization technology out there,” Mylchreest says.
Tran, JC, et al., “Mapping intact protein isoforms in discovery mode using top-down proteomics,” Nature, 480:254-8, 2011.
Perkel, JM, “Mass spectacle,” The Scientist, 23(3):61, March 2009.
The Scientist Staff, “Top 10 Innovations, 2011,” The Scientist, January 2012.
The image at the top of this page is Thermo Fisher's Q Exactive.
Editor's Note: The article, “ESI Versus MALDI For Protein Characterization By Mass Spec,” (May 8, 2007) has been updated with the current article. | <urn:uuid:e64f8979-e16d-4b72-9e37-495a8e99081c> | 2.75 | 3,323 | Truncated | Science & Tech. | 34.457787 |
While some may hope that this column might define unit testing as a component of the software development process that we, as geo-developers, are allowed to ignore, our contention is that it is a critical component in any GIS software development effort. It is a facet of development that cannot be ignored.
An informal industry survey performed in 2008 by one of the coauthors of this column revealed that 48 percent of developers in the GIS industry do not write any unit tests. This statistic, when paired with the fact that maintenance costs for custom development projects typically exceed 50 percent of project life cycle costs, indicates that testing standards require a bit of attention in the GIS industry.
The basic principle underlying unit testing is simply to take the smallest executable segments of code—typically at the method level—and prove that the code works as expected under as many anticipated circumstances as possible. Most often this process is performed by writing code that can be repeatedly executed using an automated testing framework such as NUnit or MbUnit. While there are other methods, the primary reasons for this automated testing regimen are threefold:
At the conceptual level, the unit testing process is very simple and is illustrated in Figure 1. In a typical scenario, a test class is written that instantiates a class to be tested. The test fixture class calls methods on the class under test and validates the results of those method calls. Most automated testing frameworks will prepare a report of test results so the developer can quickly identify and address problem areas in the code.
Designing ArcObjects Applications and Complex Testing Scenarios
Simple methods with simple arguments mean simple unit test fixtures. Nearly everyone reading this article will understand that testing a summing function, a user authentication routine, or a method to fetch data is a relatively straightforward process. At the same time, testing complex methods that accept complex inputs results in complex test fixtures with results that are frequently difficult to reduce to a Boolean good or bad result.
While the authors work primarily in the Web realm on a daily basis, we have written literally hundreds of thousands of lines of ArcObjects code over the years and recognize the integral role such applications will continue to play in the GIS enterprise for the foreseeable future. Unit testing these applications is critical. Most ArcObjects code falls into the second, more complex, testing category. For example, how does the developer test that a custom edit sketch task returned a valid geometry or that the resulting geometry intersected with a target layer to return the correct number of features?
The first step in effective unit testing of ArcObjects applications is designing the application using patterns that facilitate unit testing from the start. In general this means following good object-oriented design patterns as shown in the diagram in Figure 2.
Methods should be single purpose and have no side effects or reliance on global variables (IApplication, for example). Wherever possible, application logic should be separated from eventing and the general "wiring" that makes the application go.
In the case of ArcGIS Desktop applications, the developer must be careful to separate ArcMap from ArcObjects. Keep custom code out of the ArcMap event handlers and encapsulate logic in business objects and utility classes that can be independently instantiated and tested. Conversely, keep event delegates and sinks out of your custom logic. Let's just all agree that ArcMap is going to raise that OnSketchFinished event and the .NET CLR is going to pass it off to your delegate. If they don't, what are you going to do about it? Simply pass needed data into your custom classes from your unit test fixtures and validate what you have control over.
For stand-alone ArcGIS Engine and ArcGIS Server applications, the developer typically controls all the code so a custom app. will typically already contain code to create an instance of everything a unit test needs. While there is no IApplication lurking in the background to muddy the waters, validation of custom functions is still complex because we still need a way to validate a geometry or a feature class.
When developing applications for ArcGIS Server, custom code should be kept out of code-behind files and *.asmx files. This allows migration of custom components to the server object container (SOC) and will increase ease of unit testing.
Unit Testing Geometry Operations: A Test Case for ArcUnit
No matter how much we design for unit testing, we are still faced with the problems of how to collect the needed objects/data to pass in to a test method (feature class, geometry) and how to validate the results of the test (e.g., check that a given geometry result is correct). ArcUnit, a community-based open source project, provides tools and utilities to address this need. Currently hosted on Assembla at http://svn2.assembla.com/svn/ arcdeveloper/TestingUtilities, the ArcUnit effort consists of a series of utility classes and tools designed and implemented to assist the developer in manipulating and validating data when unit testing ArcObjects code. These tools can be freely downloaded by developers who are encouraged to use the tools provided and contribute new functionality for the benefit of the developer community.
The ArcUnit code base has been started with tools and utility classes to unit test custom geometry editing functions. To date, the effort has focused on how to simulate sketches, store and retrieve geometries, and create tests against independent datasets not tied to a specific instance of a geodatabase. A custom ArcGIS Editor extension and toolbar are included in the source code, as well as utilities for serializing and deserializing ArcObjects and classes to simulate commonly used ArcObjects interfaces such as IFeatureClass and IObjectClass.
As a test case for illustrating how to use ArcUnit utilities, assume that a developer must validate a custom Split Polygon edit task in ArcMap. Using the design principles discussed above, the developer separates the implementation of the polygon split from the eventing in ArcMap. To test the custom logic of the split edit task, the developer now needs
How might the developer get the information required for effective unit testing without being tied to user interaction and a geodatabase instance? The answer lies in the IXMLSerialize interface. More than 200 ArcObjects classes implement this interface (including many aspects of the geodatabase), and any of these objects can be stored as an XML representation. A custom editing toolbar supplied in the ArcUnit source code allows a developer to serialize sketch geometries or selected geometries from a map and load/draw geometries from existing XML files as shown in Figure 3.
The basic workflow for unit testing geometry operations with ArcUnit is simple. Using the ArcUnit editing toolbar in ArcMap, needed geometries are created and serialized into XML files for use within unit test fixtures. The resulting XML files are then stored as embedded resources within the unit testing project inside a Visual Studio solution (illustrated in Figure 4), so that they are source controlled and have no dependency on user action within ArcMap or on a specific instance of a geodatabase.
To write unit tests to validate the geometry operations involved in the Split Polygon edit task test case, serialized geometries are loaded from resource files at test startup and passed-into a function under test from within an individual unit test, and output geometries are compared using IRelationalOperation:: Equals(). The test source code example shown in Figure 5 leverages Geometry-Storage and GeometryRelations utility classes included with ArcUnit to assist with serialization/deserialization and unit test assertions, respectively.
The authors have generally found unit test coverage for custom GIS development initiatives within the Esri realm to be comparatively low relative to other software sectors. In defense of the geodeveloper community, unit testing for Esri applications presents a special case where typical spatial operations are complex and difficult to test without dependencies on the containing application, user interaction via the GUI, and geodatabase instances. We believe that unit testing is still a critical component of our custom development efforts and that the ArcUnit initiative can serve as a starting point for a whole host of mock objects, data serialization/deserialization routines, and test patterns that will assist the community in guaranteeing high-quality code against the Esri COM-based APIs by providing a library of functions covering many common GIS testing scenarios.
For more information, contact
Brian Noyle, Senior Software Architect
David Bouwman, CTO and Lead Software Architect
About the Authors | <urn:uuid:e27953e5-4fc6-44ff-a7d7-2820b035d9de> | 2.765625 | 1,755 | Documentation | Software Dev. | 22.381565 |
Classification / Names
Common names | Synonyms | Catalog of Fishes (gen., sp.) | ITIS | CoL | WoRMS | Cloffa
Actinopterygii (ray-finned fishes) > Synbranchiformes
(Spiny eels) > Mastacembelidae
Etymology: Macrognathus: Greek, makros = great + Greek, gnathos = jaw (Ref. 45335).
Environment / Climate / Range
Freshwater; benthopelagic. Tropical
Size / Weight / Age
Maturity: Lm ? range ? - ? cm
Max length : 30.0 cm SL male/unsexed; (Ref. 30857)
(total): 13 - 19;
soft rays: 49;
Vertebrae: 75. Distinguishable by its dorsal spine count of 13-19 and a series of 3-6 conspicuous ocelli along the base of the soft dorsal fin (Ref. 27732). The ocelli along the base of the dorsal fin are much larger than those in M. aral and the dorsal and caudal fins lack the fine striations seen in M. aral and M. meklongensis (Ref. 39392). Dorsal, caudal and anal fins not fused (Ref. 43281).
Asia: Mekong, Chao Phraya (Ref. 43281), Maeklong, Peninsular and Southeast Thailand river systems (Ref. 26336).
Found at bottom depths in slow-moving or standing waters. Often lies buried in the silt, sand, or fine gravel with only a portion of its head protruding from the bottom (Ref. 12693). Enters flooded forest (Ref. 9497). Emerges at dusk to forage for food. Feeds on benthic insect larvae, crustaceans, and worms (Ref. 12693). Marketed fresh and often seen in the aquarium trade (Ref. 12693).
Kottelat, M., 1998. Fishes of the Nam Theun and Xe Bangfai basins, Laos, with diagnoses of twenty-two new species (Teleostei: Cyprinidae, Balitoridae, Cobitidae, Coiidae and Odontobutidae). Ichthyol. Explor. Freshwat. 9(1):1-128.
IUCN Red List Status (Ref. 90363)
Threat to humans
Fisheries: commercial; aquarium: commercial
ReferencesAquacultureAquaculture profileStrainsGeneticsAllele frequenciesHeritabilityDiseasesProcessingMass conversion
CollaboratorsPicturesStamps, CoinsSoundsCiguateraSpeedSwim. typeGill areaOtolithsBrainsVision
Estimates of some properties based on empirical models
Phylogenetic diversity index (Ref. 82805
= 0.5000 [Uniqueness, from 0.5 = low to 2.0 = high].
Bayesian length-weight: a=0.00250 (-0.18863 - 0.19362), b=3.02440 (2.91846 - 3.13033), based on LWR estimates for this family-BS (Ref. 93245
Trophic Level (Ref. 69278
): 3.3 ±0.40 se; Based on food items.
Resilience (Ref. 69278
): High, minimum population doubling time less than 15 months (Preliminary K or Fecundity.).
Vulnerability (Ref. 59153
): Low vulnerability (24 of 100) . | <urn:uuid:ad8f10b9-a1ae-4adb-bd29-98b25b07867b> | 3.015625 | 766 | Knowledge Article | Science & Tech. | 61.54359 |
Invisible ink made from germs? Seeing is believing
Author JACQUELINE DETWILER
When designing experiments, scientists don’t usually consider what kids might like for their birthday, but it seems Manuel Palacios and David Walt of Tufts University have arrived at the perfect present (were it at all appropriate for children). Forget the Acme spy kit — these researchers have discovered how to make invisible ink out of germs. Using bacteria that they genetically modified to light up in different colors, they built a simple code (e.g., red plus green equals the letter “m”) and laid out the bacteria in order on a special piece of paper. The technology could be used for secret watermarks to, say, protect shipments of high-value pharmaceutical drugs from thieves. Here’s how they did it.
1. Specialty research suppliers sell genes for jellyfish proteins that glow blue, green, red, orange or yellow when exposed to fluorescent light. Palacios and Walt ordered a bunch and attached them to a common bacteria, then tested them to see which were the brightest.
2. The scientists used the bacteria to lay out a color-coded message on “paper” made of nitrocellulose. When the message’s intended receivers got it, all they had to do was press it into bacteria food (no, not your son’s socks — it’s called agar) to make it grow. After two days, they shined a fluorescent light on it and the colors appeared.
3. To better hide the secret missives, Palacios and Walt made some bacteria antibiotic-resistant. To read the message, the receivers grew it, then doused it in ampicillin before shining the light on it. The ampicillin killed off all the extra glowing bacteria, leaving only the message behind.
ILLUSTRATION BY DAN MATUTINA | <urn:uuid:4a7595d4-59cc-4041-9151-97ce92224aac> | 3.40625 | 400 | Truncated | Science & Tech. | 51.588107 |
Elachistidae was expanded by Hodges (1998), following the suggestion of Minet (1990), to include eight subfamilies: Stenomatinae, Ethmiinae, Depressariinae, Elachistinae, Agonoxeniinae, Hypertrophinae, Deuterogoniinae, and Aeolanthinae. Some of these families have previously been given family status or subfamily status within Oecophoridae and other families. Hodges defined Elachistidae by the apomorphic pupa with lateral condyles on abdominal segments 5-6 and 6-7, restricting their lateral movement as first mentioned by Minet (1990). In addition, the ventral surface of A9 often has two zones of recurved setae.
Hodges considered the Elachistidae to be a sister group to the remaining Gelechioidea. However, Kaila included Elachistidae as a derived clade within the oecophorid lineage of families, which he placed as a sister group to the gelechiid lineage of families (2004).
The family includes more than 165 genera and 3,270 species worldwide (Hodges, 1998). Larvae are leaf tiers, leaf rollers, leaf miners, seed feeders, stem borers, or external feeders on various dicots and monocots. The distribution and feeding habits are treated further in discussions of each subfamily.
Prior to being included within Elachistidae, this subfamily was included as a subfamily of Oecophoridae (Hodges, 1978) or as a separate family (Meyrick, 1906; Duckworth, 1964). Minet (1990) proposed inclusion of Stenomatinae in his expanded concept of Elachistidae. As defined by Hodges (1998), males have the second abdominal sternum lacking venulae and apodemes (homoplasious with Deoclonidae (Syringopainae). The abdominal terga of the adults lack spines. The genitalia are characterized by a valva bearing some thickened setae with bifid or multifid apices and an uncus that is uni-, bi-, trilobed, or absent. The hindwing is usually broader than the forewing, Rs is bent towards Sc near the end of the cell, and Rs and M1 are usually stalked (Scoble, 1992; Hodges, 1998). The male antenna is generally characterized by presence of long setae.
Stenomatinae include about 1,200 species of small to medium sized moths in more than 30 genera and are most diverse in the Neotropical Region, but also occur in Madagascar, India, New Guinea, Australia, and New Zealand. About 23 species in five genera, notably Antaeotricha, occur in America north of Mexico. Larvae feed as borers, leaf tiers, or leaf miners on living and wilted vegetation of a wide variety of plant families, although 35% of species with known hosts feed on Myrtaceae (Hodges, 1998). Pupation occurs within the larval shelter (Scoble, 1992).
Most Ethmiinae, at least those in North America, can be recognized superficially by their forewing shape and pattern: an elongate wing with longitudinal streaks or spots and a separation of fasciae and pigmented areas on the costal half of the wing from the lighter colored dorsal area. This subfamily has the forewing venation with R 5 terminating on the costa instead of the outer margin, an apomorphy shared with the sister taxa Depressariinae, Elachistinae, Agonoxeninae and some Hypertrophinae. The hindwing has Rs and M1 separate, a character shared with other gelechioids. Abdominal sternum II has only the venulae present, a homoplasious character shared with several other gelechioids. The gnathos is fused broadly with tegumen and has an apical projection that is spinose or is absent, and the phallobase is recurved (Hodges, 1998). Sattler (1967) distinguished Ethmiinae by the presence of an isolated costal lobe on male valva. The abdominal terga of the pupa are not spined (Scoble, 1992).
This subfamily includes more than 350 species in about 5 genera, and is most diverse in tropical-subtropical areas, especially those in seasonally arid areas (Hodges, 1998; Wei et al, 2007). The greatest diversity is in the northern Neotropical Region (Scoble, 1992). About 54 species in three genera, mainly Ethmia, occur in America north of Mexico. Larval hosts are mainly Boraginaceae and Hydrophyllaceae, although some species use Papaveraceae, Ranunculaceae, Rosaceae, Sabiaceae, and Scrophulariaceae (Hodges, 1998; Wei et al, 2007).
References: Common (1990), Keifer (1936), Minet (1990), Powell (1971, 1973, 1980, 1985), Sattler (1967), Stehr (1987), Scoble (1992), Wei et al. (2007).
Originally described as a family by Meyrick (1883), Depressariinae has been treated more recently as a subfamily of Oecophoridae (Gaede, 1939; Hodges, 1974, 1978; Scoble, 1992). Common (1990), Nielsen and Common (1991), and Minet (1990) raised this subfamily to family status. As defined by Hodges (1998), imagoes usually have a four-segmented maxillary palpus, hindwing with Rs and M1 separate, and fore- and hindwings broad. The abdominal terga usually lack spines, and the male genitalia are symmetrical with a gnathos composed of a single spinose lobe or sometimes two separate lobes (Scoble, 1992).
Depressariinae include about 600 species in about 80 genera and are most diverse worldwide, but absent from many island groups. Larvae feed as leaf tiers, seed feeders, and stem borers on dicots (17 families), including Apiceae, Asteraceae, Betulaceae, Corylaceae, Fabaceae, Fagaceae, Malvaceae, Rosaceae, Rutaceae, Salicaceae, Urticaceae (Hodges, 1998).
References: Common (1990), Gaede (1939), Hodges (1974, 1978, 1998), Kaila (2004), Minet (1990), Nielsen (1996), Nielsen and Common (1991), Scoble (1992).
Species are typically small sized and, consequently, are less collected than other members of the family. This subfamily is distinguished from other Gelechioidea by the following combination of characters: 1) hindwing lanceolate with Rs and M1 long stalked, 2) female retinaculum with anteriorly directed scales on CuA, 3) antennal pecten present (Hodges, 1998). Ocelli are generally absent, the antennal scape is large and often forms an "eye-cap." The forewings range from broad to narrow, but the hindwings are always narrow (Scoble, 1992).
The subfamily occurs worldwide and includes about 550 described species in 15 genera, primarily in the genus Elachista (Scoble, 1992; Hodges, 1998; Kaila, 1999).
Larvae are primarily leaf miners, but some are stem borers, on Poaceae (about 75%), but other species are miners of Boraginaceae, Commelinaceae, Cyperaceae, Juncaceae, Lamiaceae, and Loniceraceae (Hodges, 1998). Pupation usually occurs outside the mine in a cocoon or covering of silk, but the pupae of some species are exposed and attached by a girdle to the substratum (Scoble, 1992).
References: Braun (1948), Common (1990), Falkovitsch (1981), Hodges (1978), Kaila (1992, 1996, 1997, 1999a, 1999b, 2003, 2004), Kuroko (1982), Minet (1990), Powell (1980), Traugott-Olsen & Nielsen (1977), Wagner (1987).
Hodges (1978), Scoble (1992), and Koster and Sinev (2003) treated the Agonoxeninae as a family. Very few apomorphies are present, but these include the considerably enlarged valvellae (anellus lobes), the more or less weakened valvae, and the peculiar leg-shaped appendages of the pupa (Koster and Sinev, 2003). The latter character is a synapomorphy for Agonoxeninae and other subfamilies, including Ethmiinae and Hypertrophinae (Koster and Sinev, 2003). Hodges (1983), Scoble (1992), and others have included Blastodactini and Parametriotini as tribes (or subfamilies) of Agonoxenidae.
Larvae are usually twig- or bark-borers, miners, gall makers, or external feeders on various woody, rarely herbaceous, plants of various families, including Arecaceae, Euphorbiaceae, Proteaceae, Rosaceae, Theaceae, and Tiliaceae (Hodges, 1998; Koster and Sinev, 2003). Pupation occurs outside the larval habitat, but not in the ground (Hodges, 1998).
About 95 species in 23 genera are known to occur worldwide (Hodges, 1998). The family is especially well represented in tropical regions where many species were erroneously described in other groups of microlepidoptera.
References: Hodges (1978), Koster & Sinev (2003), Nielsen (1996), Scoble (1992).
Minet (1990) suggested that Hypertrophinae be included in his expanded concept of Elachistidae, but Nielsen (1996) subsequently gave this group family status. The genitalia are characterized by a valva bearing a free sclerite at the distal end of the sacculus, a supposed apomorphy but occurring also in Cryptophasa balteata (Xyloryctinae) (Hodges, 1998). The larva has the mesial crochets on A10 widely spaced or absent (Hodges, 1998).
Hypertrophinae include more than 50 species in 11 genera in Australia, Tasmania, and New Guinea. Larvae feed as external feeders within silk shelters on Myrtaceae, esp. Eucalyptus (Hodges, 1998).
References: Common (1980, 1990), Diakonoff (1954a), Hodges (1974, 1978, 1998), Minet (1990), Nielsen (1996).
Nielsen (1996) treated Deuterogoniinae as a subfamily in the Oecophoridae.
This subfamily of Elachistidae is defined by the tegumen being poorly developed and mesially membranous (unique within Gelechioidea), a weakly sclerotized uncus that is separated from the tegumen by a broad membrane, and a hindwing with an outer margin that is excavated below the apex (Hodges, 1998).
Immature stages, biology, and hosts are unknown, except for one record of an adult emerging from a cynipid gall on Quercus.
The subfamily includes four species in two genera, Deuterogonia and Paradeuterogonia in the Palearctic (eastern Europe, Japan, Taiwan) and Oriental (Thailand) Regions.
References: Fujisawa (1991), Hodges (1978), Saito (1987, 1989), Toll (1964).
The genitalia are characterized by the male having a valva broadly attached to the vinculum, usually parallel with the vinculum for basal 1⁄2, then directed posteriorly at a right angled lobe (an apomorphy within Gelechioidea) and an aedeagus ankylosed with the juxta (Hodges, 1998). The larva of one species feeds as a leaf roller on Cedrela (Meliaceae) (Fletcher, 1933).
The subfamily includes about 20 species in Aeolanthes in India and Western China (Hodges, 1998).
References: Clarke (1955b), Fletcher (1933), Hodges (1998). | <urn:uuid:1971f190-acd2-45a4-9ac4-8b72d9afa3c5> | 2.828125 | 2,677 | Knowledge Article | Science & Tech. | 29.897534 |
STARS rich in metals are more likely to host planets than your average star. This discovery will help astronomers refine how they search for planets, and is already providing fresh clues to how planets form.
In a survey of 754 nearby stars, those with roughly the same amount of iron and other metals as the sun have an 8 per cent chance of hosting planets. "Once we see stars with three times the metal content of our sun, the planet detection rate goes up to 20 per cent," says Debra Fischer, an astronomer at the University of California, Berkeley, who revealed the finding. But none of the 29 stars with less than one-third the sun's level of metal had planets
Fischer and ...
To continue reading this article, subscribe to receive access to all of newscientist.com, including 20 years of archive content. | <urn:uuid:b60a2bdb-e826-4532-b2d2-9c8a8e9d778d> | 3.609375 | 171 | Truncated | Science & Tech. | 60.17 |
Glauber – the father of quantum optics
that Roy Glauber took up was to formulate a theory
that gave optics a quantum-mechanical explanation
too. He succeeded in describing a general method
for observing photons which gave a correct picture
of, for example, the difference between light from
a laser and from an ordinary light bulb. | <urn:uuid:bdb0347f-ce1c-410b-92e9-b4a5bb49cc1a> | 3.1875 | 73 | Knowledge Article | Science & Tech. | 29.718864 |
Jenny Ribble submitted a handmade Ask Todd asking "If heat rises, why is it so cold in the mountains?"
Well Jenny, that's a great question!
It has to do with two things: air density and altitude.
Air is a poor insulator of heat in general, and is heated from below, from the ground up. So the sun heats the ground first, then the air right above it.
But as you move further away from the ground up into the atmosphere, the heat is filtered out and greatly diminished because the air is less dense. Less dense air cannot hold as much heat.
Higher altitudes have thinner air as well so this is why the mountains are colder. | <urn:uuid:3842eebf-2974-4b90-89ff-8eeae9aec47c> | 3.25 | 143 | Q&A Forum | Science & Tech. | 70.699343 |
Containers such as these usually contain industrial waste.
Click on image for full size
Septic tanks, city dumps, and watery waste from human activity may contaminate groundwater. Among many things which contribute to contamination are chemicals found in laundry detergents.
Lots of salt on icy roads in the winter may lead to sodium chloride (NaCl) contamination.
Another very common contaminant to ground water is some fertilizers used in farming which are healthy for plants, but toxic to humans.
Shop Windows to the Universe Science Store!
The Spring 2010 issue of The Earth Scientist
, focuses on the ocean, including articles on polar research, coral reefs, ocean acidification, and climate. Includes a gorgeous full color poster!
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Almost 3/4 of the Earth is covered with water. Almost all of that water is in the oceans. Have you ever been swimming in the ocean? If you have and you accidentally got water in your mouth, you know the...more | <urn:uuid:e8a41e50-37d8-4fa0-a381-446f52e54c0c> | 3.328125 | 478 | Content Listing | Science & Tech. | 53.09158 |
Science Fair Project Encyclopedia
|Name, Symbol, Number||Oxygen, O, 8|
|Group, Period, Block||16 (VIA), 2, p|
|Density, Hardness||1.429 kg/m3, NA|
|Atomic weight||15.9994 g/mol|
|Atomic radius (calc.)||60 (48) pm|
|Covalent radius||73 pm|
|van der Waals radius||152 pm|
|e− 's per energy level||2, 6|
|Oxidation states (Oxide)||−2,−1 (neutral)|
|State of matter||gas (paramagnetic)|
|Melting point||50.35 K (−369.04 °F)|
|Boiling point||90.18 K (−297.34 °F)|
|Heat of vaporization||3.4099 kJ/mol|
|Heat of fusion||0.22259 kJ/mol|
|Vapor pressure||__ Pa at __ K|
|Speed of sound||317.5 m/s at 25 °C|
|Electronegativity||3.44 (Pauling scale)|
|Specific heat capacity||920 J/(kg·K)|
|Electrical conductivity||ND MS/m|
|Thermal conductivity||0.02674 W/(m·K)|
|1st ionization potential||1313.95 kJ/mol|
|2nd ionization potential||3388.3 kJ/mol|
|3rd ionization potential||5300.5 kJ/mol|
|4th ionization potential||7469.2 kJ/mol|
|Most stable isotopes|
|SI units & STP are used except where noted.|
- This article is about the chemical element Oxygen. For other usage, see Oxygen (disambiguation)
Oxygen is the chemical element in the periodic table that has the symbol O and atomic number 8. The element is very common, found not only on Earth but throughout the universe, usually bound with other elements. Unbound oxygen (usually called molecular oxygen, O2) made its initial appearance on Earth as a product of the metabolic action of early anaerobes (archaea and bacteria). The atmospheric abundance of free oxygen in later geological epochs and up to the present has been largely driven by terrestrial plants, which release oxygen during photosynthesis.
At standard temperature and pressure, oxygen is predominantly found as a gas consisting of a diatomic molecule, with the chemical formula O2. O2 itself has two energetic forms; the low-energy, predominant single-bonded diradical triplet oxygen , and the high-energy double-bonded molecule singlet oxygen . This native diradical quality of oxygen contributes to its destructive chemical nature.
Oxygen is a major component of air, produced by plants during photosynthesis and is necessary for aerobic respiration in animals. The word oxygen derives from two words in Greek language.Greek, &oxus or oxys (acid) and &geinomai (engender). The name "oxygen" was chosen because, at the time it was discovered in the late 18th century, it was believed that all acids contained oxygen. The definition of acid has been revised so they do not require oxygen in their molecular structure.
Liquid oxygen,Liquid O2 and solid O2 have a light blue color and both are highly paramagnetic. Liquid oxygen|Liquid O2 is usually obtained by the fractional distillation of liquid air. Both liquid and solid O3 (ozone) have a deeper color of blue.
Another recently discovered allotrope of oxygen, O4, is a deep red solid that is created by pressurizing O2 to the order of 20 GPa. Its properties are being studied for use in rocket fuels and similar applications, as it is a much more powerful oxidizer than either O2 or O3.
Oxygen finds considerable use as an oxidizer, with only fluorine having a higher electronegativity. Liquid oxygen finds use as an oxidizer in rocket propulsion. Oxygen is essential to respiration, so oxygen supplementation has found use in medicine. People who climb mountains or fly in airplanes sometimes have supplemental oxygen supplies (as air). Oxygen is used in welding, and in the making of steel and methanol.
Oxygen, as a mild euphoric, has a history of recreational use that extends into modern times. Oxygen bars can be seen at parties to this day. In the 19th century, oxygen was often mixed with nitrous oxide to promote a kind of analgesic effect; indeed such a mixture (Entonox) is commonly used in medicine today.
Oxygen was first discovered by Michał Sędziwój, Polish alchemist and philosopher in late 16th century. Sędziwój assumed the existence of oxygen by warming nitre (saltpetre). He thought of the gas given off as "the elixir of life".
Oxygen was again discovered by the Swedish pharmacist Carl Wilhelm Scheele sometime before 1773, but the discovery was not published until after the independent discovery by Joseph Priestley on August 1 1774. Priestley published his findings in 1775 and Scheele in 1777; consequently Priestley is usually given the credit. It was named by Antoine Laurent Lavoisier after Priestley's publication in 1775.
Oxygen is the second largest single component of the Earth's atmosphere (20.947% by volume).
Due to its electronegativity, oxygen forms chemical bonds with almost all other elements (which is the origin of the original definition of oxidation). The only elements to escape the possibility of oxidation are a few of the noble gases. The most famous of these oxides is of course dihydrogen oxide, or water (H2O). Other well known examples include compounds of carbon and oxygen, such as carbon dioxide (CO2), alcohols (R-OH), aldehydes, (R-CHO), and carboxylic acids (R-COOH). Oxygenated radicals such as chlorates (ClO3−), perchlorates (ClO4−), chromates (CrO42−), dichromates (Cr2O72−), permanganates (MnO4−), and nitrates (NO3−)are strong oxidizing agents in and of themselves. Many metals such as Iron bond with oxygen atoms, iron (III) oxide (Fe2O3). Ozone (O3) is formed by electrostatic discharge in the presence of molecular oxygen. A double oxygen molecule (O2)2 is known, found as a minor component of liquid oxygen. Epoxides are ethers in which the oxygen atom is part of a ring of three atoms.
Oxygen has three stable isotopes and ten known radioactive isotopes. The radioisotopes all have half lives of less than three minutes.
Certain derivatives of oxygen, such as ozone (O3), hydrogen peroxide, hydroxyl radicals and superoxide, are also highly toxic. The body has developed mechanisms to protect against these toxic species. For instance, the naturally-occurring glutathione can act as an antioxidant, as can bilirubin which is normally a breakdown product of hemoglobin. Highly concentrated sources of oxygen promote rapid combustion and therefore are fire and explosion hazards in the presence of fuels. This is true as well of compounds of oxygen such as chlorates, perchlorates, dichromates, etc. Compounds with a high oxidative potential can often cause chemical burns.
The fire that killed the Apollo 1 crew on a test launchpad spread so rapidly because the pure oxygen atmosphere was at normal atmospheric pressure instead of the one third pressure that would be used during an actual launch. (See partial pressure.)
- Winkler test for dissolved oxygen for instructions on how to determine the amount of oxygen dissolved in fresh water.
- The role of oxygen as a diving breathing gas.
- oxygen depletion aquatic ecology
- Priestley Society, Dedicated to Joseph Priestley the man who discovered oxygen; Oxygen
- Joseph Priestley Information Website, about the man who discovered oxygen; Oxygen
- Los Alamos National Laboratory – Oxygen
- WebElements.com – Oxygen
- EnvironmentalChemistry.com – Oxygen
- It's Elemental – Oxygen
- Oxygen Therapy – The First 150 Years
- Oxygen Toxicity
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details | <urn:uuid:b265efbc-ef5b-4de7-95eb-15aed241d08e> | 3.765625 | 1,825 | Knowledge Article | Science & Tech. | 38.165444 |
One of the methods you can invoke on Strings is length(). The way you invoke a method on an Object is similar to the way you extract a field from an object; you use dot notation. For example:
int len = name.length(); System.out.println (len);
Notice the parentheses after length. They indicate that length is a method that takes no arguments, as opposed to a field named length. That probably (but not necessarily) indicates that length calculates the length of the String when you invoke it, as opposed to keeping the value in memory along with the String. All the methods you can invoke on Strings are described on page 326.
Another method you can invoke on a String is toUpperCase. This method returns a new String that is the same as the old String except that all the lower case letters are converted to upper case. It does not modify the existing String. In fact, nothing you do can modify an existing String--they are immutable. | <urn:uuid:58184f56-348f-49ed-8252-d8eb0d3aceb7> | 3.375 | 201 | Documentation | Software Dev. | 61.278791 |
|This article follows on from my earlier article about Application variables, and how they allow you to store "global" data for use by all your pages.|
Session variables are very similar. You can create them and store data in them in exactly the same way:
|// create a new Session variable to store the users name
Session ( 'Name' ) = 'James';
// display the name in any page on your site
Out ( 'Your name is ' + Session ( 'Name' ) );
The crucial difference between Application and Session variables is that Session variables are specific to each visitor to your site.
Background: The stateless webThe problem that Session variables have to overcome is that the HTTP protocol that you use to browse the web is stateless. Each request for a page is completely independant of earlier requests, so if you want subsequent pages to "remember" the users name that he entered on your front page you have to store that information somewhere.
This remembering of user-specific data is called "maintaining state". We'll see next how the ASP Session object can help us do just that.
Part 2: Creating a new Session... | <urn:uuid:35f8e42e-aa7f-44c0-9aef-7766d4ccae7a> | 3.03125 | 240 | Truncated | Software Dev. | 45.380743 |
The New York Times has a great article out this week, as we near the year anniversary of the Macondo Well blowout and the ensuing horror of the Gulf oil spill.
What has emerged in studies so far is not a final tally of damage, but a new window on the complexities of the gulf, and the vulnerabilities and capacities of biological systems in the face of environmental insults.
While there’s still a lot of speculation, hidden data, and many unknowns, here’s an update on what we know so far:
- Baby dolphin kills are still unexplained. Was it oil toxicity? Was it a virus? Or did we DSN-ers send them our bad Juju?
- Of the 28,000 turtle eggs that were moved in response to the spill, about 51% hatched (in line with expected survival rates – a hesitant yay!)
- Many scientific results are not yet public, since the government’s Natural Resource Damage Assesment (NRDA) process is still ongoing and working to come up with a sum for damages—the money needed to restore the gulf to its pre-spill condition
- Oil droplets in the deep water column were largely gone just weeks after the well was capped (present at less than 2 parts per billion), eaten up by specialized cold water microbes
- Likewise, 200,000 tons of methane were relased into the gulf, but this gas may have been degraded by autumn as well (but different labs reported conflicting data)
- Ashes, ashes, we all fall down. Yep, there seems to be an oil blanket in the deep sea and the muddy sediment looks like a Spongebob graveyard. Dead worms, dead coral, dead starfish (Noooooo, not Patrick!!).
- Although, EPA testing is showing that the dispersant-BP oil combo isn’t more toxic than the oil itself, this news isn’t entirely reassuring since obvious traces of the ‘biodegradable’ Corexit are still very present in the Gulf ecosystem. Long term exposure to chronic, subtle chemicals—isn’t that what causes cancer in humans?
- Researchers from British Columbia calculated that a 50x ‘multiplier effect’ should be used to tabulate the true number of animal deaths. So even though only 115 whales and dolphin mortalities were visually recorded, accounting for unseen deaths this number should be 1115 x 50 = 5,750?!
- Bluefin tuna not as badly affected as feared? Some wiped out, but some spared? Reseacher interviewed being coy..SHOW ME THE DATA! (I’m sure I’ll see it in Nature soon enough…)
- We’re sitting with baited breath to see what happens to the marshes. Will new grass grow this year with such heavy pollution still coating the Louisiana shores? Satellite data suggest more brown marsh lacking new growth (150 square miles versus typically 25-30 square miles).
Clearly the Gulf is not quickly forgetting the effects of the oil — some residents have even flown all the way to London to protest at BP’s annual shareholder meeting. | <urn:uuid:2bf80282-9f3f-4bf7-b250-29de3bb66a43> | 2.6875 | 644 | Personal Blog | Science & Tech. | 56.66248 |
(Submitted October 18, 1998)
What are Brown Dwarfs?
Brown dwarfs are small-size objects, believed to result from
condensations of fragments of molecular clouds.
A brown dwarf has a small mass, too low to ignite nuclear
fusion. Such a star, would be small, not much larger than Jupiter, and
warm from its contraction.
It would emit copious infrared radiation, thus the name "brown dwarf".
You can check the following site on brown dwarfs:
Eric Christian for
for Ask an Astrophysicist | <urn:uuid:8be6bb03-bbfd-4abf-ab79-2d589b7518e0> | 3.765625 | 118 | Q&A Forum | Science & Tech. | 62.6375 |
The original superconductor was invented in 1911 by Dutch physicist, Heike Kammerlingh Onnes, when these superconductors are cooled, they act as a perfect conductors with no resistance. Onnes experimented with mercury, tin, and lead.
Meissner EffectIn 1933, Walther Meissner and R. Ochsenfeld discovered that superconductors are more than a perfect conductor of electricity, they also have an interesting magnetic property of excluding a magnetic field (Meissner Effect). A superconductor will not allow a magnetic field to penetrate its interior. It causes currents to flow that generate a magnetic field inside the superconductor that just balances the field that would have otherwise penetrated the material.
Mysteries of Superconductors - BCS TheoryIn 1957, scientists began to unlock the mysteries of superconductors. Three American physicists at the University of Illinois, John Bardeen, Leon Cooper, and Robert Schrieffer, developed a model that has since stood as a good example of why superconductors behave as they do and expressed the advanced ideas of the science of quantum mechanics. Their model suggested that electrons in a superconductor condense into a quantum ground state and travel together collectively and coherently.
In 1972, Bardeen, Cooper, and Schrieffer received the Nobel Prize in Physics for their theory of superconductivity, which is now known as the BCS theory, after the initials of their last names.
Georg Bednorz and Alex Mueller - High Temperature SuperconductorsIn 1986, Georg Bednorz and Alex Mueller, working at IBM in Zurich Switzerland, were experimenting with a particular class of metal oxide ceramics called perovskites. Georg Bednorz and Alex Mueller surveyed hundreds of different oxide compounds. Working with ceramics of lanthanum, barium, copper, and oxygen they found indications of superconductivity at 35 K, a startling 12 K above the old record for a superconductor. Soon researchers from around the world would be working with the new types of superconductors. In February of 1987, a perovskite ceramic material was found to superconduct at 90 K.
This discovery was very significant because now it became possible to use liquid nitrogen as a coolant. Because these materials superconduct at significantly higher temperatures they are referred to as High Temperature Superconductors. | <urn:uuid:edd3aa88-6d7d-4412-b8f0-6c9c8ca99648> | 4.21875 | 482 | Knowledge Article | Science & Tech. | 21.233215 |
In the global search for sustainable energy sources, photovoltaic (PV) cells are an area of keen interest because of their ability to convert absorbed sunlight to electricity through the interactions of photons (packets of light) and electrons in a semiconducting material.
In 1954 Bell Labs introduced the first modern silicon-based PV cells, but with production costs more than $1,000 per kilowatt, their use was limited. Flash forward more than 50 years, and the cost of producing PV cells now is around $4 per kilowatt, and their use, though not widespread, is more commonplace. Today PV systems power communication and navigation equipment, light homes and commercial buildings, and feed electricity back into the utility grid.
The sun radiates more energy in a single hour than the entire planet uses in a whole year, yet solar energy provides less than 1 percent of the world’s electricity. Although sunlight is free, PV-generated electricity costs about 5 times more than grid electricity.
Conventional PV cells are made with highly refined silicon and manufactured in labor- and energy-intensive processes, which accounts for about 80 percent of the cost. PV cells are also plagued by low efficiency regarding the amount of absorbed sunlight converted to electricity. Silicon-based PV cells convert about 20 percent of absorbed sunlight to electricity; PV cells made with little or no silicon, such as thin films and organic semiconductors, are less expensive to manufacture, but their conversion efficiencies are much lower.
Spurred on by more than scientific curiosity, researchers are intent on developing high-efficiency PV cells that can be manufactured in automated high-throughput processes, and University of Tennessee scientists are rising to the challenge.
“One of the bottlenecks in PV technology is in using less silicon while maintaining efficiency,” says Barry Bruce, an associate professor in UT Knoxille’s Department of Biochemistry and Cellular and Molecular Biology.
Instead of silicon, Bruce and his colleagues at the Massachusetts Institute of Technology have developed an organic PV cell using a photosynthetic protein complex isolated from spinach leaves. They use spinach because it’s cheap, it can be grown anywhere, and it’s rich in chlorophyll, the molecule that absorbs sunlight.
Through this process, researchers liquefy spinach in a food processor, extract the protein complex, “wrap it in surfactant peptides to stabilize it, and then integrate it into a solid-state device,” says Bruce. When bathed in laser light, the protein complex produces an electrical current; not enough current to power a lamp, but enough to prove that a biological reaction center will work in an electronic circuit.
Bruce’s photosynthetic PV cell has a conversion efficiency of about 12 percent, but he thinks he can boost that by layering the protein complex, like the skin on an onion, so the cell can absorb more light. The next steps seek to improve stability and durability, and if successful, spinach-powered PV cells might one day coat window surfaces to power the lights in a building.
The notion that electricity could be harvested from the garden doesn’t surprise Bruce, who was recently named by Forbes as one of 10 revolutionary innovators who could change the world.
“I got into photosynthesis 30 years ago because I believed it was the fundamental solution to energy,” he says. “Nature has spent 2 to 3 billion years perfecting an energy conversion system that is almost 100 percent efficient, and all we have to do is take advantage of it.”
Bruce’s colleague, Bamin Khomami—head of the Department of Chemical and Biomolecular Engineering and holder of the Armour T. Granger and Alvin and Sally Beaman Professorship—thinks that within 10 years, PV efficiencies could easily triple, which could push worldwide consumption of PV-generated electricity to 10 percent.
Semiconducting nanoparticles can be deposited on various substrates to create tailored PV films, and they can be added to organic or inorganic semiconductors to increase PV-cell efficiency. This class of PV material is attractive because nanoparticles can be tuned, making them photoactive in different ranges of light.
“Photons contain energy that corresponds to different wavelengths of light,” Khomami explains. “Only photons of the right energy can excite electrons in a given system, which then flow to create an electrical current.”
The properties of materials change as their size approaches the nanoscale, and with a model-guided experimental approach, Khomami tries to pin down the “magic” size that will deliver a desired property for a particular nanoparticle.
“By controlling particle composition, size, and distribution, we try to optimize photoactivity,” he says. With increased photoactivity, incoming photons excite more electrons, and more electrons mean more electricity and higher conversion efficiencies.
Khomami is also developing models and simulation strategies to guide development of efficient processes—for instance, a roll-to-roll process, similar to the way newspapers are printed—by which nanoparticle-based PV films can be coated onto various substrates.
“Compared with fossil-fuels technology, PV technology is in its infancy,” says Khomami, “but it is advancing at a rapid pace.” Those PV cells developed during the 1950s were for the space program, but until recently, the technology has languished because it lacked a driving force with the power of the Cold War’s space race.
But now a powerful new force created by a convergence of environmental and geopolitical factors is driving the development in the technology, says Khomami. And the expanded interest in solar energy is underpinned by a “paradigm shift from a traditional design process that had little regard for energy or environmental costs to a new process that includes sustainability,” he says.
Bin Hu agrees with Khomami. “Controlling the polymer PV process is challenging,” says Hu, an assistant professor in the Department of Materials Science and Engineering who specializes in functional polymers, “but PV technology is accelerating now.” Polymer PV cells, a developing technology, may soon be a practical alternative to conventional silicon-based PV cells.
“The fundamental principles of polymer PV cells are not yet understood,” says Hu. But, organic light-emitting diodes (OLED) and polymer PV cells are like two sides of the same coin: OLEDs convert energy to light and PV cells convert light to energy.
“OLED technology is very mature and we can learn from that science,” he says. Hu recently won a CAREER Award from the National Science Foundation to support his work with OLEDs, which dovetails precisely with his work in polymer PV cells.
When light hits a polymer PV cell, a negatively charged electron breaks free from an atom, creating a positively charged hole. The electrons and holes [charge carriers] must flow in different directions to generate current, but “sometimes the charge carriers get lost,” says Hu.
To boost efficiency, Hu blends nanostructures—microscopic roadmaps—into the polymers to direct the charge carriers to the electrodes.
The efficiency of polymer PV cells currently peaks at about 6 percent, but they will be commercially competitive at 10 percent.
“Polymer PV cells have a dramatic advantage over silicon,” says Hu. Polymer PV cells are lightweight and flexible, and they can be integrated easily into building materials—a concept that is evolving, but not yet widespread.
Cheaper photovoltaic building materials will make it possible to construct homes and commercial buildings that generate most, if not all, of the energy they use, which is a major focus of the Department of Energy’s Building Technologies Program (BTP). The goal of BTP is to have in place the technology to provide cost-effective “zero energy” buildings by 2025, which will reduce the strain on the utility grid during periods of peak demand and at the same time offset the emission of harmful pollutants.
- - -
Duncan Earl first set foot in Oak Ridge National Laboratory in the early 1990s as an undergraduate in the Science Alliance Summer Fellowship Program. Today, this UT alumnus (engineering physics and electrical engineering) is taking ORNL-developed technology into the private sector—harnessing the sun’s power to light up working environments all over the country.
Earl is founder and chief technology officer of Sunlight Direct, which uses solar collectors and optical fibers to pump sunlight into buildings. The system works in tandem with electricity, using natural sunlight when the rays are brightest and switching to grid power when the clouds roll in. Studies have shown that natural sunlight—versus incandescent or fluorescent lights—increases worker productivity and sets off retail merchandise in a much more pleasing glow.
At present the company has 23 beta-test units across the United States. Each is remotely monitored with the data going back to ORNL, which acts as an independent evaluator. Among the current sites are an Aveda Corporation plant in Minnesota and a new unit going in at the Naval Exchange at Pearl Harbor, Hawaii.
The company anticipates a move to the commercial market by the end of 2007. The current cost for each system is $16,000, but Earl says they hope to cut that in half by 2008. The investment recoup is based on the client’s location (Hawaii, for instance, has lots of sunny days) and it’s possible that some places will see payback in less than a year. On a bright day, a Sunlight Direct system can deliver the equivalent of 55 60-watt incandescent lamps, which can translate into a savings of about 6,000 kilowatt hours per year. Earl says in a couple of years the company hopes to start exploring residential possibilities for the technology.
With increasing interest from investors and a $1-million grant from the U.S. Department of Energy, Sunlight Direct is poised to find more customers and uses for solar technology. As Earl says, developing alternative energies will generate jobs, create new products to market at home and abroad, and improve the environment.
“It can be done,” he says. “It’s not a pipe dream.”
At present the company is housed at Tech 2020, a nonprofit partnership in Oak Ridge, Tennessee, but anticipates a move soon due to limited production capacity at the current location. Earl says the company plans to keep production local. And when the company starts looking for new employees, he says, he’ll be looking to the University of Tennessee.
For more information, contact Duncan Earl at 865-483-6624 or firstname.lastname@example.org.
— C. L. | <urn:uuid:51a3d88d-740c-435d-b85e-0bb58299de43> | 3.8125 | 2,257 | Knowledge Article | Science & Tech. | 34.092543 |
App::Chart::Timebase -- timebases
App::Chart::Timebase object represents a date/time period and a starting point.
Dates in a timebase are integers starting from 0 for the starting point. For example a timebase might be weeks starting from 19 Nov 2007, in which case that week is 0, the following week is 1, etc. Methods on the timebase objects allow conversion of year/month/day dates to or from such an index number.
Create and return a new timebase object representing the given days/weeks/etc type of period, and with a 0 at the given
$start is an ISO format string like "2007-12-31".
Days means weekdays, ie. trading days. Weeks is calendar weeks starting from each Monday, through to the following Sunday. Months is calendar months. Quarters are calendar quarters like Jan/Feb/Mar then Apr/May/Jun, etc.
Return an ISO date string like "2007-12-31" for the given
$t timebase index (an integer). For example,
my $timebase = App::Chart::Timebase::Days->new_from_iso ('2008-05-01'); my $iso = $timebase->to_iso (5); # $iso is '2008-05-08' (weekday 5 counting from 0 at 1 May)
$timebase->from_ymd_floor ($year, $month, $day)
Return a time value (an integer) in
$timebase which corresponds to the given date, either as values
$day, or an ISO date string
$str like "2007-12-31".
If the date is not representable in
$timebase, then for
floor the return is the next earlier timebase value or for
ceil the next later. This only arises on a
Days timebase when the date requested is a Saturday or Sunday. In that case
floor gives the preceding Friday or
ceil the following Monday.
$timebase->convert_from_floor ($from_timebase, $from_t)
$timebase->convert_from_ceil ($from_timebase, $from_t)
Convert an time value in
$from_timebase to a value in
$timebase. The two timebases can have different starting points and different units, such as converting a day number into a week number.
When the destination
$timebase is a higher resolution than
convert_from_floor version gives the start of the
$from_t period and the
convert_from_ceil version gives the end. For example if
$from_timebase is years but the destination
$timebase is months then
floor gives the first month (ie. January) in the
$from_t year and
ceil gives the last month (ie. December).
strftime formatted string which is timebase value
$t (an integer) under
$format. For example,
$timebase->strftime ('%d %b %Y', $t) # gives say "31 December 2007"
Return today's date as an integer in
$timebase. The optional
$timezone is a
App::Chart::TZ object to use, or the default is local time.
Return a string which is an adjective for the
$timebase. For example on a years timebase the return would be
"Yearly". The string is translated through the usual Chart internationalizations if possible. | <urn:uuid:a5a63865-c357-475c-89da-467faf24ea4b> | 2.921875 | 751 | Documentation | Software Dev. | 53.221487 |
Why is Earth so dry?
A new analysis of the common model explaining how the planets formed around our Sun uncovers a possible reason for Earth's comparative dryness.
July 17, 2012
With large swaths of oceans, rivers that snake for hundreds of miles, and behemoth glaciers near the North and South Poles, Earth doesn't seem to have a water shortage. And yet, less than one percent of our planet's mass is locked up in water, and even that may have been delivered by comets and asteroids after Earth's initial formation.
This illustration of two different disk models shows overhead views of the structure of the protoplanetary disk that encircled the newborn Sun 4.6 billion years ago. The Sun's family of planets agglomerated from dust and ices within the disk. Credit: NASA/ESA/A. Feild (STScI)
Astronomers have been puzzled by Earth's water deficiency. The standard model explaining how the solar system formed from a protoplanetary disk (a swirling disk of gas and dust surrounding our Sun) billions of years ago suggests that our planet should be a water world. Earth should have formed from icy material in a zone around the Sun where temperatures were cold enough for ices to condense out of the disk. Therefore, Earth should have formed from material rich in water. So why is our planet comparatively dry?
A new analysis of the common model explaining how planets form in a debris disk uncovered a possible reason for Earth's arid state. Led by Rebecca Martin and Mario Livio of the Space Telescope Science Institute in Baltimore, Maryland, the study found that our planet formed from rocky debris in a dry, hotter region inside the so-called "snow line." The snow line in our solar system currently lies in the middle of the asteroid belt, a reservoir of rubble between Mars and Jupiter; beyond this point, the Sun's light is too weak to melt the icy debris left over from the protoplanetary disk. Previous accretion-disk models suggested that the snow line was much closer to the Sun 4.5 billion years ago, when Earth formed.
"Unlike the standard accretion-disk model, the snow line in our analysis never migrates inside Earth's orbit," Livio said. "Instead, it remains farther from the Sun than the orbit of Earth, which explains why our Earth is a dry planet. In fact, our model predicts that the other innermost planets, Mercury, Venus, and Mars, are also relatively dry. "
In the conventional model, the protoplanetary disk around our Sun is fully ionized — a process where electrons are stripped off of atoms — and funnels material onto our star, which heats up the disk. The snow line is initially far away from the star, perhaps at least one billion miles. Over time, the disk runs out of material, cools, and draws the snow line inward, past Earth's orbit, before there is sufficient time for Earth to form.
"If the snow line was inside Earth's orbit when our planet formed, then it should have been an icy body," Martin said. "Planets such as Uranus and Neptune that formed beyond the snow line are composed of tens of percents of water. But Earth doesn't have much water, and that has always been a puzzle."
Martin and Livio's study found a problem with the standard accretion-disk model for the evolution of the snow line. "We said, wait a second, disks around young stars are not fully ionized," Livio said. "They're not standard disks because there just isn't enough heat and radiation to ionize the disk."
"Very hot objects such as white dwarfs and X-ray sources release enough energy to ionize their accretion disks," Martin said. "But young stars don't have enough radiation or enough infalling material to provide the necessary energetic punch to ionize the disks."
So, if the disks aren't ionized, mechanisms that would allow material to flow through the region and fall onto the star are absent. Instead, gas and dust orbit around the star without moving inward, creating a "dead zone" in the disk. The dead zone typically extends from about 0.1 astronomical unit to a few astronomical units beyond the star. (An astronomical unit is the distance between Earth and the Sun, roughly 93 million miles [150 million kilometers].) This zone acts like a plug, preventing matter from migrating toward the star. Material, however, piles up in the dead zone and increases its density, much like people crowding around the entrance to a concert waiting for the gates to open.
The dense matter begins to heat up by gravitational compression. This process, in turn, heats the area outside the plug, vaporizing the icy material and turning it into dry matter. Earth forms from the dry material in this hotter region, which extends to around a few astronomical units. Martin and Livio's altered version of the standard model explains why Earth didn't wind up with an abundance of water.
Martin cautioned that the revised model is not a blueprint for how all disks around young stars behave. "Conditions within the disk will vary from star to star," Livio said, "and chance, as much as anything else, determined the precise end results for our Earth."
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Learn more » | <urn:uuid:7c808bbe-2a83-4afa-ae45-b57b0235f477> | 4.28125 | 1,102 | Knowledge Article | Science & Tech. | 53.436458 |
nuclear physicist. He made fundamental contributions to molecular beam spectroscopy,
mass spectrometry, and electron acceleration technology. In 1989 he shared
the Nobel prize for physics with US scientists
Norman Ramsey and
for his development of the ion trap, or Paul trap, used to store single
atoms long enough to make useful measurements.
In 1957 he helped found the famous DESY accelerator laboratory in Hamburg.
From 1964-67, Paul was director of the nuclear physics laboratory of CERN,
the joint European laboratory for particle physics in Geneva. | <urn:uuid:bd46fbc4-bc21-4e35-9e8d-73d35c61e109> | 2.9375 | 114 | Knowledge Article | Science & Tech. | 30.014209 |
Copyright © 2009 All rights reserved.
Current Biology, Volume 19, Issue 17, R720, 15 September 2009
FeatureAdd/View Comments (0)
New elm hopes
- A new project is hoping to help restore one devastated British tree. Nigel Williams reports.
Britain's population of elm trees, one of the most desirable sources of hardwood timber, has been decimated, not by logging but by disease. The beetles carrying the lethal fungus of Dutch elm disease have almost wiped out the species from the UK. But a few have persisted, often in geographically or other physically isolated situations, and a new project now plans to plant saplings propagated from these survivors to see if they have survived because of immunity to the disease.
The charity Conservation Foundation is planning to plant 2,000 saplings later this year with the help of schoolchildren.
Some scientists are concerned that surviving British elms exist because of their isolation from invading beetles rather than inherent resistance but the new experiment should determine, within the next 15 years, whether a resistant British elm exists.
Some experts are also hoping that hybrid elms may be the way forward in beating the beetle. One tree, the Sapporo Autumn Gold, has been growing for 30 years in Britain but conservationists are concerned that it does not provide support for the many species that traditionally relied on the native elm.
Fifty years ago, the elm comprised a major tree species from southern England up to Scotland but the new strain of Dutch elm disease devastated the trees with 20 million of the estimated 30 million specimens killed by the early 1970s.
While conservationists hope to exploit genetic heterogeneity to monitor and protect tropical forests, the British hope is that remaining elms may show some resistance to the devastating Dutch elm disease. | <urn:uuid:92b9f02b-3c95-440f-acf0-0ea3b17c217a> | 3.65625 | 364 | Truncated | Science & Tech. | 36.725871 |
he Resource Description Framework (RDF)
and Web Ontology Language (OWL)
are important technologies driving development on the road to the semantic web. The former is a set of World Wide Web Consortium (W3C)
specifications that provide a model for representing metadata through specific statements, or triples
, made up of subject-predicate-object representations for specific resources. Data from disparate stores can then be mashed together or built into resources of machine-readable information, which can be processed, exchanged, and stored by web-based applications. The latter technology, OWL, is currently a W3C recommendation for a language that can be applied to define and represent data models more effectively than other metadata languages, such as XML, through the use of semantics and a vocabulary that provide class and property descriptions.
These and other technologies that are gaining more widespread adoption to build out the semantic web promote highly complex concepts and analytics, and the ability for the semantic web to extract, process, and deliver intelligent information efficiently is going to take time for developers and designers to refine and implement. Despite the learning curve, many people building applications that aim to provide Web 3.0 capabilities will need to begin embedding semantics now to get a head start delivering more meaningful, information-based content to customers and users. And one way to embed semantics for selected applications is to use microformats.
Microformats provide extensions to the standard HTML tags that have been used widely for some time to create web pages, and they are open and freely available elements for semantic-based markup in HTML or Extensible HTML (XHTML). Consider microformats as a means of lowering the barrier to your entry in semantic web development. They can even give web page designers without extensive programming experience the ability to program web sites. This discussion will take a look at microformats and demonstrate how they can be a convenient stepping-stone for developers and designers looking to participate in the evolution of the semantic web.
Rather than reinvent the web, microformats allow developers to approach the problem of embedding semantics from the perspective of existing and widely adopted web standards. Microformat-aware browsers can parse this code and use it to help extract meaning from web pages. Standard HTML markup describes how only text should be formatted. Microformats allow programs such as web crawlers to recognize items like contact information, events, and so on, which can be added to address books and calendars. Microformats also provide you the ability to aggregate content or create "mashups," such as adding a restaurant review to a MapQuest map.
Although they are in effect an attempt to turn a medium designed for publishing and presentation into something that is dynamic and programmable, it is important that microformats be designed for humans first and for machines second. Microformats should therefore be human readable and easily understood by content authors and designers as well as more experienced programmers. One way to think about microformats is that they are about people, events, places, and things, rather than just pages.
Think about the last developer conference you attended. Wouldn't it have been easier to manage your workshop schedule if the agenda on the conference web site could have found its way directly into the calendar on your laptop or PDA? Microformats can enable this kind of scenario.
From a technical point of view, microformats are a form of semantic markup using standard XHTML encoded with specific HTML attributes such as class, rel, and rev. What otherwise would be seen by a machine as just text, gains meaning through its context as indicated by wrapping items in span (or other HTML) elements with class names that are part of a specific microformat specification. A set of class namesfor example, formal name (fn), organization (org), telephone number (tel), and urlconstitutes a class (in this case, class="vcard"), which can be understood as a single, specific entity for the purposes of data exchange. Once detected, this information can be extracted by software and reused (indexed, searched for, saved, or cross-referenced). When encoded in this way, it can be used either by web services in a more programmatic manner or be imported into desktop applications.
Microformats are not unlike using XML tags, but there is one important difference: instead of allowing everyone to create their own custom XML tags, microformats are derived from existing web standards as much as possible. For example, hCard maps one-to-one to the vCard standard that has been in use for years by desktop applications like Microsoft Outlook and Apple's iCal.
Having this microformats markup based on easily understood and widely adopted standards gives authors of microformats the hope to speed adoption and provide a more generalized form of markup rather than the myriad industry-specific forms of XML. | <urn:uuid:da431171-b032-4c10-9fa4-14adbbbb9796> | 3.78125 | 987 | Knowledge Article | Software Dev. | 24.042573 |
Computer languages reflect the goals, target audiences, and to some degree the personalities of their creators and their communities. As a result, even languages that are created with similar goals in mind may yield highly disparate final results, depending on how their communities understand those goals. Ruby, Clojure, and Ceylon are three such languages.
Ruby is the oldest of the three. Created in the mid-1990s, it didn't achieve widespread popularity until the 2000s. One reason for Ruby's growth is the work of Charles Nutter, who created jRuby, a port of Ruby to the Java virtual machine (JVM). Ruby is a dynamic, object-oriented language, whereas Clojure and Ceylon use a functional programming approach.
[ InfoWorld's Paul Krill has interviewed the fathers of 9 modern programming languages; read the key excerpts from each. | Follow the latest issues in software development with InfoWorld's Developer World newsletter, and get Java users' tips from JavaWorld.com. ]
Clojure appeared in 2007, created by Rich Hickey. Although Clojure is new, it's a derivative of Lisp, the listy processing language specified in 1958, making it the second-oldest high-level language. Then there's Ceylon (the brainchild of Gavin King, the creator of the Hibernate ORM framework), which is on its second milestone prerelease.
In interviewing Ruby's Nutter, Clojure's Hickey, and Ceylon's King, I was surprised at how -- despite ending up with vastly divergent outcomes -- they share common goals and viewpoints. Each believe their language is designed to simplify the job of the developer, yet the approaches they each take toward achieving that simplicity vary wildly.
A key idea behind Ruby is to "feel as natural as possible, so you can do powerful things with Ruby but it doesn't get in your way," Nutter says. On the other hand, it "does not limit you to programs and development styles that fit into a strict statically typed world." | <urn:uuid:63e8faca-3e79-4ba1-92b5-a8d4e609545e> | 2.765625 | 408 | Nonfiction Writing | Software Dev. | 46.435219 |
Name: Mara N.
I have a spider in my house that is in a cocoon. Can you
please tell what it is doing? Is it laying eggs that in turn will create
more spiders? Please help. Thank you.
Spiders do not pupate in cocoons like insects, as far as I know the only stage of a spider life cycle
that includes a cocoon-like structure is the egg case, which the adult forms around the eggs. Yes,
they will hatch into more spiders!
The spider in question may be the sac spider.
"These spiders hide in silken tubes or sacs that resemble
cocoons during the day and hunt at night. They will bite humans
even when unprovoked. These bites are rather painful, but generally
not life-threatening." Thaks Pamela!
Click here to return to the Zoology Archives
Update: June 2012 | <urn:uuid:a4436544-8630-40be-aae3-d21af48b5a8c> | 3.109375 | 188 | Q&A Forum | Science & Tech. | 67.795659 |
An unusually strong storm moved across the Arctic earlier this week, bringing heavy winds and rain to Alaska and locations poleward. One of the most pronounced effects of the storm was a shift in Arctic sea ice concentrations. This image uses data from the SSMI/S microwave sensor on board the DMSP satellite to show the sea ice concentrations on August 1st and 8th, before and after the storm. Large reductions in extent and concentration can be seen in the left-hand side of each image where the Bering Sea empties into the Arctic Ocean. The sea ice, already at record-low concentrations this summer, is also incredibly thin after several years of intense summer melting, making the movement of ice flows very susceptible to large storm events such as the one this week. Often the thin ice flows are piled up along the northern Canadian and Greenland borders, which appears to have also happened in this case as concentrations are slightly higher in the latter image in those regions. | <urn:uuid:5003e8d8-8eb5-4c65-8d02-e06b89f62e77> | 3.421875 | 192 | Knowledge Article | Science & Tech. | 37.740196 |
Summary: rock samples. These results led to the slip-
weakening model, in which friction was
assumed to decrease as slip on the fault
increased. The key model parameter was the
slip-weakening distance (the amount of slip
required to reduce friction at high speeds).
This phenomenological model avoided the
difficult question of the origin of friction.
Mechanical studies of rocks in the late
1970s provided the first experimental evi-
dence that steady-state friction indeed
decreased logarithmically with slip rate.
Friction also depends on several parameters
representing the state of the slipping surface
(3). In these experiments, designed to under-
stand friction at low slip rates, the slip-weak-
ening distance is very small, on the order of
a fraction of 1 mm.
In the past 15 years, seismologists were
able to study in detail several major earth- | <urn:uuid:62519b71-3d6d-4602-b8fb-827c557a296b> | 3.34375 | 200 | Academic Writing | Science & Tech. | 38.468478 |
|On October 6, 2010 youth in the Twin Cities joined hundreds of thousands of young people across the nation as part of 4-HNational Youth Science Day, and conducted one simultaneous experiment: 4-H2O, the 2010 National Science Experiment. |
4-H2O showed youth how carbon dioxide can affect aquatic animals, plants and other living organisms in lakes, streams, rivers and oceans. It will feature a series of interactive activities and discussions to demonstrate the importance of water quality and its relevance to climate change, and how they can help reduce their carbon footprint in their own communities.
<< All categories| | <urn:uuid:8aaa215e-589f-41f9-8aa2-861eaa5bab3b> | 2.84375 | 124 | Content Listing | Science & Tech. | 25.503636 |
In our previous article GPGPU for Java Programming we showed how to setup an environment to execute CUDA from within java code. However the previous article focused only on setting up the environment leaving the subject of parallelism untouched. In this article we will see how we can utilize a GPU do what is doing best: parallel processing. Through this example we will take some metrics and see where GPU processing is stronger or weaker than using a CPU …and of course as the title suggests there is an ugly part at the end.
Read more at: | <urn:uuid:e3b22918-6f50-44a2-bfa3-75f9c568c0dd> | 2.984375 | 109 | Comment Section | Software Dev. | 42.674858 |
Scientific name: Thymelicus sylvestris
A small butterfly with a darting flight, widespread England and Wales
Bright orange-brown wings held with forewings angled above hind wings. Males have thin black line through centre of fore-wing. Essex Skipper is similar but has black tips to antenna (best viewed head on) and shorter scent brand which runs parallel to forewing edge rather than angled.
Small Skippers are insects of high summer. Although they spend much of their time basking or resting among vegetation, they are marvellous flyers, manoeuvring expertly through tall grass stems. It is these darting flights, wings glinting golden-brown in the sunlight, that normally alert an observer to their presence. Closer examination will reveal many more individuals nectaring or basking with their wings held in the half-open posture distinctive of skipper butterflies. The butterfly is widespread in southern Britain and its range has expanded northwards in recent years.
Size and Family
- Family – Skippers
- Small Sized
- Wing Span Range (male to female) - 30mm
- UK BAP Status: Not listed
- Butterfly Conservation priority: Low
- European Status: Not threatened
The Small Skipper almost exclusively uses Yorkshire-fog (Holcus lanatus), although several other grasses have been recorded as foodplants, for example Timothy (Phleum pratense), Creeping Soft-grass (H. mollis), False Brome (Brachypodium sylvaticum), Meadow Foxtail (Alopecurus pratensis), and Cock’s-foot (Dactylis glomerata).
- Countries – England, Scotland and Wales
- Widespread up to North Yorkshire and Scottish border
- Distribution Trend Since 1970’s = Britain: +4%
Prefers open places with long grass, such as unimproved rough grassland, downs, road verges, field edges and woodland glades.
- Woodlands for Butterflies and Moths
- Butterflies and farmland
- Farmland Butterflies ID chart
- Butterflies in towns and cities
- Gardening for Butterflies and Moths | <urn:uuid:0cc919a9-87f8-4b7f-97ec-98dc858f6d7e> | 3.5625 | 455 | Knowledge Article | Science & Tech. | 30.814091 |
Re: Question about using telescoping with recurrence in studying algorithms.
- From: Martin Eisenberg <martin.eisenberg@xxxxxxx>
- Date: 3 Feb 2006 21:45:20 GMT
I am relatively new to the study of algorithms, do not have an
extensive background in mathematics, and find some of the steps
in solving an equation to represent how long an algorithm will
take to be perplexing.
The use of telescoping in order to come up with a solution is
not intuitive to me. Could someone please point to a website or
book that will very explicitly go through each step and explain
this process in detail? Often in Sedgewick's Algorithms in C++
book when it says with x, y, z it is clear that a, b,c... it is
not clear to me.
I think you are referring to repeatedly substituting the right-hand
side of a recurrence relation into itself in order to guess the form
of its solution -- what Alf dug up is about something else entirely.
I can't point you anywhere in particular, but you might start by
looking over the hits on
for something with the level of detail you seek.
Quidquid latine scriptum sit, altum viditur.
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A quantitative survey of the ecology of mosses in the McMurdo Sound region was conducted in the 1976/77 field season. Moss was found around streams below the Rhone, Hughes and Calkin Glaciers in the Taylor Valley, the moraines below the Hobbs Glacier and in the Salmon, Garwood and Towle Valleys, and in the Scott Base, McMurdo Station areas. Other areas searched where moss was not found included ... Kennar and Beacon Valleys, the area below La Croix Glacier and the side of the Taylor Valley around Lake Conney not near melt streams below alpine glaciers and the Towle Valley. Algae and lichen were recorded from most of the areas visited. Detailed quantitative surveys of moss were done below the Rhone, Calkin and Hughes Glacier and on the delta below the snout of the Hobbs Glacier. Air spore samples were collected daily, fresh algae was collected from Lake Fryxell and Lake Vanda for C14 dating standards and soils were sampled for tests for microorganisms, pH, carbon and nitrogen content. | <urn:uuid:596ff182-173f-4310-b4fc-05bd99a2d205> | 3 | 221 | Academic Writing | Science & Tech. | 51.420476 |
Search Loci: Convergence:
To the pure geometer the radius of curvature is an incidental characteristic - like the grin of the Cheshire cat. To the physicist it is an indispensable characteristic. It would be going too far to say that to the physicist the cat is merely incidental to the grin. Physics is concerned with interrelatedness such as the interrelatedness of cats and grins. In this case the "cat without a grin" and the "grin without a cat" are equally set aside as purely mathematical phantasies.
The Expanding Universe..
Solving Euler Squares of Order Five
Euler squares were introduced on the first day of a problem solving class for mathematics teachers. Nineteen teachers were placed in collaborative groups and given a pegboard holding five different geometric shapes in five different colors (see Figure 4). The author acknowledges ETA Cuisenaire for providing the six Geo-Shapes Pegboards for her research.
Figure 4: a Geo-Shapes Pegboard
Challenged to find a way to place the pegs so that no shape or color repeated in any row or column, groups were observed using three methods to find a solution: diagonalization, the knight’s move, and Sudoku skills. | <urn:uuid:1a6ff4ec-8df7-4a0d-b9cc-c5cf4285f119> | 2.921875 | 258 | Academic Writing | Science & Tech. | 37.798384 |
Although plants are firmly rooted in the ground, they do move: sunflowers track the Sun across the sky; daffodils turn their floral faces away from the wind as it blows. Most plant motion is either quite slow (the sunflower), or driven by external factors (the wind on the daffodil). Herbal hustle caused by internal forces is uncommon. That’s no surprise, really: plants have neither nerves nor muscles, nor do they have other obvious mechanisms for generating force rapidly.
Yet despite the lack of muscle, several plant lineages have independently evolved some capacity for rapid movement. The trigger plants of Australia, for instance, slap a dab of pollen on visiting bees. More morbidly, the Venus flytrap slams two halves of a leaf shut on nutritious insects. Recently, investigators discovered that the flytrap owes its quick grasp to a “bistable configuration” of its leaves, whereby small movements can trigger much larger ones.
The Venus flytrap (Dionaea muscipula) is native to verdant, boggy coastal plains of North and South Carolina. Bogs are more acidic and have fewer nutrients than most plants can tolerate, and so it’s no coincidence that several bog plants supplement their root-gathered nutrition with insect snacks. That makes a bog into a minefield for winged and walking arthropods. Bladderworts, pitcher plants, and sundews all indulge their carnivorous tastes. Among those refugees from the Little Shop of Insect Horrors, though, the flytrap has a uniquely dynamic method for catching prey.
The flytrap features a set of inch-long, heart-shaped capture leaves, each fringed with trigger hairs and bisected by a deep fold. Any insect unwary enough to bend a single hair is a goner. The two halves of the leaf snap shut along its fold in just 100 milliseconds, swiftly enveloping the animal. The trigger hairs become the bars of a prison. In the ensuing few hours the trap seals itself airtight, and digestive glands in the leaf secrete enzymes that reduce the insect to a dry husk.
Botanists discovered the Venus flytrap several hundred years ago, and its behavior has fascinated people ever since. It may come as a surprise, then, that until recently no one knew how a flytrap, unthinking and without muscles, could move fast enough to capture flies. The mystery prompted Yoël Forterre, a physicist at the University of Provence in Marseille, France, and his colleagues to take up the case.
To improve visibility, the team began by daubing flytrap leaves with dots of paint that glows under ultraviolet light. Then they shot videos of the leaves closing, at 400 frames per second (a somewhat smaller video file, showing the action at 125 frames per second is available online at www.nature.com/nature/journal/v433/n7024/suppinfo/nature03185.html). Watching the videos in slow motion, and tracing the path of each painted dot in three dimensions, the investigators discovered that what appears to be a quick, fluid snap of the two halves of the leaf is actually a three-phase process.
In its initial, open configuration, the capture leaf looks like a paperback book that has been splayed open by breaking its binding, and further insulted by bending its spine into an arc. The two halves of the leaf also curve away from each other; if you were to see them from the hapless insect’s point of view, they would appear to be convex, with the center of each leaf toward you and the edges curving away. | <urn:uuid:6057b3ed-bc53-46a9-9ecb-44a71baf52f9> | 3.671875 | 753 | Knowledge Article | Science & Tech. | 47.584375 |
Gravity as a Wave
Name: David H.
If, as it is suspected, that gravitons exist and that
gravity is radiated, shouldn't gravity have wave properties? And
couldn't this suspected wave property of gravitons be used to show they
do exist? Which leads to a more practicle question, If gravity is shown
to have wave properties as is suspected then would it be possible to
cancel out the wave and nullify gravity? Or am I interpretting my
Not all radiation behaves as waves. In fact, beta radiation is just a bunch
of electrons being released. Gravitons can behave as particles.
Even if they do have some wave properties, we can only examine them after we
learn to detect them. Most waves we work with are electromagnetic: radio,
microwaves, visible light, x-rays. Gravitons would be based on
gravitational force. They would have no effect of electrical detectors.
Once we figure out how to detect them, we will know that they are there
One of the major reasons to believe in gravitons is the fact that gravity
decreases with distance as 1/(distance-squared). If gravitons are radiated
out in all directions, the number that reach you from the radiating object
will vary as 1/(distance-squared). The explanation works with photons
"carrying" electric force between charges. It would make several properties
of gravity easier to explain.
Dr. Ken Mellendorf
Click here to return to the Physics Archives
Update: June 2012 | <urn:uuid:3c6fd9ad-61e1-4f72-a7bc-3960cad882c5> | 3.078125 | 333 | Audio Transcript | Science & Tech. | 47.972289 |
BACKGROUND: Thundersnow is a thunderstorm that has snow reaching the surface instead of rain. Usually thunder and lightning are more commonly observed in warm seasons. A severe thundersnow occurs when the snow is accompanied by hail that is at least three-fourth of an inch in diameter, or when wind speeds reach at least 50 knots.
HOW STORMS DEVELOP: Storm clouds form as moisture evaporates from the earth into the atmosphere, where the droplets congregate and jostle against each other. The air cools off rapidly with altitude. Sometimes a cold front -- the boundary between where the cold air from one thunderstorm meets the air outside the storm for example ý will force the moist air upward into the colder air. This moist air cools off and the water vapor "condenses" into liquid drops, forming clouds. The process -- called the convective process by meteorologists -- continues: more and more water vapor turns into liquid, and the moist air warms up even more and rises higher and higher. A thunderstorm results.
WHAT CAUSES LIGHTNING? As more and more water droplets collide inside a cloud, their atoms bounce off each other more forcefully. This knocks off electrons. The ousted electrons gather at the lower portion of the cloud, giving it a negative charge, while the upper part of the cloud becomes positively charged. Eventually the growing negative charge becomes so intense that electrons on the Earth's surface are repelled and burrow deeper into the Earth. The Earth's surface becomes positively charged, and hence very attractive to the negative charge accumulating in the bottom of the cloud. All that is needed is a conductive path between cloud and Earth, in the form of ionized air.
TURBULENT FLOWS: A flow is the continuous movement of a fluid, like water or air, from one place to another. If the air molecules move smoothly in the same direction and at the same speed, this flow is said to be "laminar." Turbulence occurs when the molecules move in many different directions and at many different speeds, so turbulent flows are very common in Nature. How easily a fluid becomes turbulent depends on its viscosity: how much it resists movements. Air currents have low viscosity, so turbulence is quite common in the atmosphere. If you heat air at the bottom and cool it at the top, this convective process will cause it to become turbulent, much like water boiling in a pot. Changes in air pressure can also give rise to turbulent conditions. And when different air masses flow over each other at different speeds they can give rise to beautiful cloud formations.
The American Meteorological Society contributed to the information contained in the TV portion of this report. | <urn:uuid:4b4184d0-44ef-41e7-83a6-46c35d16966a> | 4.28125 | 554 | Knowledge Article | Science & Tech. | 43.897792 |
September 6, 2010
With the exception of a Great White, or possibly an Oceanic White-tip (on a bad day), nothing terrifies me more than the prospect of meeting a 20ft (6m) Saltwater ‘Estuarine’ Crocodile out in the open Ocean. And apparently that’s not as unlikely as I would have hoped for!
Despite being poor swimmers, researchers have discovered that the saltwater crocodile (also known as estuarine) commonly travels long distances over open oceans by riding ocean currents. The discovery, published in Journal of Animal Ecology, solves an unknown mystery of why saltwater crocodiles (Crocodylus porosus) are found across vast distance in the Pacific, yet have not diverged into different species.
Researchers tracked 27 adult saltwater crocodiles for one year using tags and sonar transmitters. The tagging showed that crocodile individuals, both male and female, regularly traveled more than 50 kilometers from their local rivers into the open sea. One crocodile traveled 590 kilometers in 25 days; another traveled 411 kilometers in 20 days.
The saltwater crocodile’s range extends from India to Fiji and from southern China to northern Australia. They are the world’s largest crocodile species.
Oh man, bring out the cello….
Having read this article I decided to read-up on where in the world precisely I might have a chance of bumping in to (or more like becoming a light snack of) one of these huge ocean-going beasts. Here’s what I found:
perhaps not so surprising that they frequent the region of the planet with the largest bio-diversity – and even less surprising that my number 1 must-see diving destination (planned for 2012) is PNG and is a veritable hot spot for the buggers! Great
March 16, 2009
A marine biologist has helped fill in the so-called lost years of Australia’s loggerhead turtles by discovering they are using ocean currents to undertake a 20,000-kilometre, round trip across the Pacific Ocean.
Dr Michelle Boyle, of the School of Marine and Tropical Ecology at James Cook University, Queensland, and colleagues used genetic testing to track the migratory behaviour of the Australian-born loggerhead turtle (Caretta caretta), which hatches in rookeries on the Queensland coast.
Boyle says it appears the endangered turtles use the ocean currents that make up the South Pacific gyre to travel across the southern Pacific Ocean to the waters off Peru and Chile.
In scenes reminiscent of the animated movie Finding Nemo, they then pick up the East Australian Current (EAC), which they “ride” down the coast of eastern Australia.
From ABC Science, Full Article HERE
May 28, 2008
Britain’s biggest shark species has been tracked for the first time for thousands of miles from waters southwest of the Isle of Man to Canada.
Until now little was known about endangered basking sharks (Cetorhinus maximus) when they moved outside British waters, but scientists have confirmed that the animals travel huge distances and plunder deep waters for food. The discoveries were made with the help of two sharks, known as A and B, who were tagged last year.
The detailed pattern of movements will now enable scientists to identify new ways to protect sharks from harm in British waters. There is still a risk of hunting in other waters, however, because of the shark’s highly valued fins, which are a delicacy in some countries.
From the Times: Read more | <urn:uuid:e53c5989-f1e3-4e27-a033-ab6613ebe5f1> | 3.109375 | 737 | Content Listing | Science & Tech. | 37.525 |
nuclear reaction equilibrium
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origin of chemical elements
Finally, at temperatures around 4 × 10 9 K, an approximation to nuclear statistical equilibrium may be reached. At this stage, although nuclear reactions continue to occur, each nuclear reaction and its inverse occur equally rapidly, and there is no further overall change of chemical composition. Thus, the gradual production of heavy elements by nuclear fusion reactions is...
What made you want to look up "nuclear reaction equilibrium"? Please share what surprised you most... | <urn:uuid:62da90f6-4a3a-45b2-91ea-ed0f382ee49a> | 3.515625 | 132 | Knowledge Article | Science & Tech. | 41.111646 |
A very small atom can cast a very large shadow. Well, not literally, but figuratively. Researchers at Griffith University have managed to snap the first image of a single atom's shadow and, while the dark spot may be physically small, the implications for the field of quantum computing are huge. The team of scientists blasted a Ytterbium atom suspended in air with a laser beam. Using a Fresnel lens, they were able to snap a photograph of the dark spot left in the atom's wake as the laser passed over it. The practical applications could improve the efficiency of quantum computers, where light is often used to transfer information. Since atoms have well understood light absorption properties, predictions can be made about the depth of a shadow cast, improving communication between the individual atoms performing calculations. The research could even be applied to seemingly mundane and established fields like X-Ray imaging, by enabling us to find the proper intensity levels to produce a quality image while minimizing damage to cells. For more info, check out the current issue of Nature. | <urn:uuid:bbdd7e34-e4f9-4029-938b-24b2fbf6c87e> | 3.734375 | 209 | Truncated | Science & Tech. | 35.026175 |
A protein is a string of amino acids, which you can think of, roughly, as a necklace of multi-colored beads. A protein, however, twists and folds into a shape that’s less like a necklace than a pretzel, and each protein has its own unique pretzel shape, determined by which beads are on the necklace and in what sequence.
Scientists know that sometimes if you switch one bead for another, the pretzel doesn’t change much, but other times — depending on which bead you switch or which new one you substitute — the pretzel may radically alter its shape. When a gene mutation causes this to happen in people, it may — depending on the protein — lead to a debilitating disease.
No wonder, then, that scientists want to decipher the underlying code of relationships between amino acids and protein shape, called the protein-folding problem. “It’s like saying you have a sentence and it has a meaning,” says computational chemist Carlos Simmerling. “How many words can you change before it doesn’t have that meaning anymore? How many of the amino acids in the protein can you change before it doesn’t fold properly and you have a disease?”
Simmerling, of the State University of New York at Stony Brook, and graduate student Melinda Layten used LeMieux, Pittsburgh Supercomputing Center’s terascale system, to see what happens when you switch beads on the necklace. With LeMieux, he’s been asking these questions with a special protein called Trp-cage, a short necklace of only 20 amino acids — compared to hundreds for most proteins. Because of its small size, Trp-cage’s folding is relatively simple and presents a model case for analysis.
Working in close collaboration with a laboratory team led by Niels Andersen at the University of Washington, Simmerling made efficient use of up to 1,000 of LeMieux’s processors to simulate Trp-cage, all of its atoms — first in its native state, then with several carefully chosen variations. He’s found, dramatically, that one switched amino acid transforms the pretzel to a floppy noodle, but another subtle switch changes it back to a pretzel. His simulations add detail and complexity to an emerging picture of sensitive relations between amino acids and structure in this special minimalist protein.
Trp-cage, significantly, is the smallest protein known that has a stable, folded shape. In 2002, starting with a longer protein from Gila monster saliva, Andersen and his team created Trp-cage in their laboratory. Their work was lauded as among the biochemistry highlights of the year.
“It provides a model system,” says Simmerling, “for close collaboration between experiment and simulation on the same sequence, and until Trp-cage there was nothing like this. The proteins that we could simulate were too small to be stable, and the systems that were stable experimentally were too big to simulate. It’s an important meeting place for experiment and theory.”
These graphics from the simulation show a simplified representation of Trp-cage with the protein backbone (yellow ribbon) and selected amino acids. In the native, folded structure (Gly), spheres of cyan (carbon) and white (hydrogen) represent side-chains of tryptophan (blue, nitrogen) within a "cage" of two prolines. This characteristic fold gives Trp-cage its name. The small glycine (green) is at a bend in the fold.
In one of many structures (Lala) adopted by Trp-cage after alanine (purple side chain) replaces the glycine, the tryptophan no longer packs into the cage and the protein remains floppy. A slight change to the alanine side-chain permits the tryptophan to pack in the cage, forming a structure (Dala) similar to native Trp-cage.
Simmerling is one among a team of computational biochemists who have developed a widely used software package, called AMBER, that employs a method called molecular dynamics (MD) to simulate proteins and DNA. MD calculates the forces that act among all the atoms in the molecule and tracks their movement over time.
Before Andersen’s group released their experimental findings of Trp-cage’s structure, Simmerling used AMBER to accurately predict it. Starting with only the amino-acid sequence, his simulations arrived at a structure in excellent agreement with the configuration, as determined by NMR methods, that Andersen’s group subsequently published. “We demonstrated,” says Simmerling, “that MD simulations have come a long way, and are at a point where accurate structure prediction by simulation may soon be routine enough to contribute significantly to our understanding of folding.”
This simulation also suggests structural detail that goes beyond the experimentally determined shape. Based on these details, Andersen’s group is working to further analyze and refine the structural picture.
This graphic represents the free-energy landscape of a small, stable protein segment called Trp-cage. Color (increasing from dark blue to red) corresponds to altitude in the landscape. Stable proteins tend to form in structures that correspond to the low-energy valleys. (Image courtesy of Asim Okur)
To predict Trp-cage’s shape, Simmerling relied on a well-tested axiom of molecular structure. A molecule tends to move toward being in a shape in which the atoms expend the least possible energy to maintain structure. Although Simmerling’s structure-prediction simulation was remarkably successful, proteins in the real world aren’t represented solely by their low-energy state.
“There’s a native lowest energy structure,” explains Simmerling, “and at the same time, there may also be non-native, unfolded structures. We need to know not just the native structure, but we want to know its relative probability. Is it native 30 percent of the time? Or 90 percent? All we can say from the first simulation is this structure is best, but we don’t know what that means in terms of real stability.”
To produce this information on relative probabilities, Simmerling employed a method called “replica exchange,” a relatively recent innovation in MD simulation that he implemented as part of AMBER. In this approach, designed to exploit a massively parallel system such as LeMieux, many separate simulations of a single protein run at the same time on different processors. The processors exchange information to arrive, eventually, at a picture of the protein’s “energy landscape” — a map of the relation between possible shapes and their likelihood.
Using LeMieux, Simmerling carried out replica-exchange simulations of Trp-cage, showing that it’s in its native, folded state 90 percent of the time, a very stable structure. In further studies, using up to 1,000 LeMieux processors (at 90 percent parallel efficiency), he simulated three altered versions of the protein — each with a single change of amino acid — which the Andersen group also looked at experimentally. One of these changes produced a dramatic result in the stability of the folded structure.
Among amino acids, glycine is the smallest, and is distinctive in having no attached chemical group, called a side chain. For this reason, glycine provides structural flexibility and often appears at a tight turn in a protein’s fold. In experiments, changing a Trp-cage glycine to alanine — an amino acid only slightly larger — prevented folding. “We can take something that’s over 90 percent folded,” says Simmerling, “make one small change, and it won’t fold anymore. Alanine has only a small side chain — a single methyl group (CH3) — and yet it has a huge effect.”
Somewhat differently from the experiments, the replica-exchange simulations showed that with alanine the folded structure still exists, but it’s highly unstable. Spurred by these simulations, further experiments found that this altered Trp-cage retains some areas of structure.
Based on analysis of these results, the researchers tried another switch. They replaced the alanine with its mirror image, called d-alanine — which flips alanine’s side-chain from one side to the other of the protein. With this slight change, simulations showed that Trp-cage regained nearly all of its folded stability. Experiments confirm that this switch restores nearly full stability.
“There’s wide interest in glycine,” says Simmerling, “and how it’s involved in folding. And there hasn’t been data, especially with respect to how it compares with d-alanine. We think this study, relying on both experiment and simulation, will be among the first to show that not only do we have this model system, Trp-cage, that’s sensitive to change, but also that simulations on computers like LeMieux are helping us to understand and begin to predict the effects that gene mutations will have on these key molecules of life.” | <urn:uuid:b2e2654a-ad08-40e9-8167-63d05e326905> | 3.421875 | 1,958 | Knowledge Article | Science & Tech. | 34.894361 |
Nov. 15, 2006 Most governments around the world set conservation policy based on the assumption that resource exploitation and species protection can co-exist in the same place. These policies have led to Orwellian "marine protected areas" that host commercial fishing operations, leading one to wonder who's protecting whom. A new study reveals the danger of this approach--showing that exploitation has led to a decline of a seabird species by 80% in the Dutch Wadden Sea--and concludes that it's time to let protection mean protection.
For decades, the Dutch government sanctioned mechanical cockle dredging in three-fourths of the intertidal flats of the Wadden Sea, a natural monument protected under two intergovernmental treaties. Before suction dredging began in the 1960s, an estimated 2,000 tons of cockles were hand-harvested from the reserve each year. In 1989, the high-pressure, motor-driven water pumps used in suction dredging sucked up close to 80,000 tons of cockles. By 2004, the Dutch government decided the environmental costs were too great and stopped the practice. Jan van Gils and colleagues investigated the ecological impacts of commercial cockle dredging on intertidal ecosystems by studying a long-distance migrant shorebird that dines principally on cockles, the red knot (Calidris canutus islandica). Up to 50% of the global red knot population uses the Dutch Wadden Sea at some point during their annual cycle.
Red knots are exquisitely adapted to their lifestyle. They have a pressure-sensitive bill that senses hard objects buried in the sand and a shell-crushing gizzard to accommodate the birds' penchant for swallowing their catch whole. They even have a flexible digestive system that minimizes the energy costs of flying up to 16,000 kilometers between their arctic breeding grounds and winter homes in Europe and the tropics; their gizzard expands and contracts to balance daily food intake and energy needs. To determine the effects of dredging on the birds, the authors sampled prey quality and density over 2,800 Wadden Sea sites during the late summer months (late July to early September) for five years starting in 1998. Dredging occurred each year from September to December, immediately after their sample collections. In undredged areas, cockle densities increased by 2.6% each year, and the quality remained stable. In dredged areas, cockle densities remained stable, and their quality (flesh-to-shell ratio) declined by 11.3% each year--paralleling the decline in the quality of the birds' diet (as measured by droppings). This finding falls in line with evidence that dredging disturbs the silt cockles like to settle in, as well as their feeding conditions, which in turn reduces their quality as a food resource.
Based on prey quality and densities, van Gils et al. predicted the energy intake rate for knots with an average-size gizzard at each site (all sites were pooled into 272 blocks, each with an area of 1 square kilometer), then calculated the percentage of blocks that would not yield sufficient intake rates for knots to avoid starvation. From 1998 to 2002, the percentage of blocks that couldn't sustain knots increased from 66% to 87%--all attributable to dredging in previously suitable sites. Reduced prey density caused some of this degradation, but most stemmed from declines in both cockle density and quality.
The authors caught and color-banded the birds so they could estimate survival rates the following year, and they measured gizzard mass with ultrasonography. As expected, when prey quality declined, birds needed larger gizzards to process the relatively higher proportion of shells in their diet. Their chances of surviving conditions at the Wadden Sea increased as a function of prey quality and gizzard flexibility. Birds that did not return had much smaller gizzards than those that did. Survival rate calculations based on gizzard size and prey quality revealed that if birds could not expand their gizzard and prey quality was low (0.15 grams of flesh per gram of shell), only 47% of arriving birds would avoid starvation. A much greater proportion would survive if their gizzard could expand by at least 1 gram (70% for 1 gram, 88% for 2 grams).
These degraded food conditions, the authors conclude, explains why red knot populations have declined by 80% in the Wadden Sea. And increased mortality in the Wadden Sea, which the authors estimate at 58,000 birds over five years, accounts for the 25% decline of red knots across their entire northwest European wintering grounds. Dredging reduced the quality of red knots' primary food source so drastically that even the birds' extraordinarily adaptable digestive system could not save them. The authors point out that dredging doesn't even provide significant economic benefits--only 11 outfits manage 22 fishing boats--yet is "directly responsible" for the widespread decline of a protected shorebird. These findings put the lie to the notion that commercial exploitation is consistent with conservation and underscore the risks of disturbing critical habitat for threatened or endangered species.
Citation: van Gils JA, Piersma T, Dekinga A, Spaans B, Kraan C (2006) Shellfish dredging pushes a flexible avian top predator out of a marine protected area. PLoS Biol 4(12): e376. DOI: 10.1371/journal.pmed.0030376.
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A fish out of water is not usually a graceful or impressive sight, unless that fish is flying—or hovering inside a laboratory wind tunnel.
The members of the flying fish family soar above the waves on unusually large pectoral and pelvic fins, which act as wings. Although scientists have studied the anatomy and behavior of these peculiar finned gliders, understanding flying fish aerodynamics has never been more than educated guesswork: Researchers have approximated the physics based on known aerodynamics of other gliding animals with similarly shaped wings. Now, for the first time, a pair of researchers has directly measured the way that air flows around flying fish fins inside a wind tunnel, used the data to confirm earlier assumptions about how fish fly, and concluded that these fish glide as well as some birds. The new study, by mechanical engineers Hyungmin Park and Haecheon Choi of Seoul National University in South Korea, appears in the September issue of The Journal of Experimental Biology.
"Before, there wasn't any real experimental data about lift and drag," said Frank Fish, a West Chester University of Pennsylvania zoologist who has studied flying fish but was not involved in the recent study. "This is a step forward in that they actually have taken the bodies of the animals and put them in wind tunnels."
The National Federation of Fisheries Cooperatives in Seoul provided Choi and Park with 40 darkedged-wing flying fish (Cypselurus hiraii) freshly caught in the Sea of Japan (East Sea). After freezing the fish in an icebox the researchers selected five fish that were the most similar in size and asked the Korea Research Center of Maritime Animals to dry and stuff the fish bodies, using urethane foam to maintain appropriate anatomical geometries. The researchers extended the pectoral and pelvic fins of three stuffed fish so they resembled biplanes, they extended only the pectoral fins of a fourth fish, and retracted all the fins of the fifth specimen, giving it the shape of a torpedo. Then the researchers gave each fish a turn inside a wind tunnel and compared how air moved around the differently arranged fins. The experimenters also attached force sensors to the fish and varied the angles of their bodies inside the tunnel, to assess which angles created the greatest lift or drag.
In further tests the researchers installed a tank of water beneath the tunnel to investigate how gliding just above the surface changes the way air moves around fins. To see these effects more clearly, the experimenters also observed how smoke flowed around the fins.
The analyses yielded a few key findings. First, Choi and Park confirmed that the angles that achieved the greatest lift in the wind tunnel were the same steep angles at which flying fish emerge from the water in the wild. Second, the researchers found that when the fish glided exactly parallel to the water—as observed in nature—they maximized their lift–to–drag ratio, ensuring they stayed airborne for as long as possible. Third, Choi and Park observed that the biplane arrangement of pectoral and pelvic fins helped stabilize the fish in flight, preventing them from pitching up or down. Fourth, they ascertained that flying fish glided just as effectively as some birds, such as hawks, petrels and wood ducks—all of which are excellent gliders. Finally, they discovered that flying fish achieved incredibly efficient flight when gliding just above the water's surface—reducing drag up to 14 percent—because of something called ground effect.
Normally, a flying fish gliding some distance above the water experiences drag because of a difference in air pressure over the fin surface. The air pressure is higher below the fin than above and "that high pressure below wants to move toward the low pressure on top," Fish explains, "but that can't happen except at the wing tip, where the airflow starts to move around the tip and up to the top of [the] wing. Because you are moving forward, a wingtip vortex forms—a swirling mass that creates a long cyclone trailing behind the animal on each fin or wing tip." These vortices are a major source of induced drag, but when a fish nears the water's surface the vortices start to break up. At the same time, pressure builds below the fins, increasing lift. The combined effect makes gliding just above the water's surface more energetically efficient than free flight. The ground effect is also responsible for the slight jolt you may feel when an airplane is moments away from touching down on the runway.
Flying fish can stay airborne for distances up to 400 meters by coupling the ground effect with a behavior known as taxiing, in which they whip their tail through the water while still aloft to reaccelerate whenever they are in danger of sinking below the waves. Some flying fish have even evolved specialized tail fins with enlarged lower lobes, providing greater thrust during taxiing to help keep them airborne. Two major hypotheses offer explanations for why flying fish fly: one hypothesis says that fish fly to escape ocean predators; the other argues that fish save energy when gliding instead of swimming.
Although Fish acknowledges the inherent flaws in drawing conclusions about behavior in nature based on laboratory tests with stuffed animals, he thinks the new study is the most accurate measurement of flying fish aerodynamics to date. "The problem that you always have with a stuffed system or a model is how close to reality it actually is: we don't know the exact geometry of the wing when it's deployed, for example," Fish says. "But does this get you into the ballpark? It's a closer approximation than what was done previously. It's probably pretty close to reality." Choi emphasizes how careful he was to preserve the living anatomy of the fish, especially the delicate fins.
Both Fish and Choi agree that the new research could have applications for airplane design. "Maybe the flying fish design is very good for traveling over the water surface and economizing fuel consumption," Fish says. "It's conceivable we could have little messengers going out over the ocean." Choi refers to improving the design of wing-in-ground-effect (WIG) vehicles, which are specifically constructed to take advantage of the ground effect. "One of our next lines of research," Choi says, "is to apply what we learn from flying fish to these special planes." | <urn:uuid:96eb348d-4ec1-4bb3-a54f-83bcdaab2c8a> | 3.875 | 1,281 | Knowledge Article | Science & Tech. | 39.411748 |