May 25, 2007, 3:28 PM CT

New Fabrication Technique Yields Nanoscale UV LEDs

Scientists at the National Institute of Standards and Technology (NIST), in collaboration with researchers from the University of Maryland and Howard University, have developed a technique to create tiny, highly efficient light-emitting diodes (LEDs) from nanowires. As described in a recent paper,* the fabricated LEDs emit ultraviolet light-a key wavelength range mandatory for a number of light-based nanotechnologies, including data storage-and the assembly technique is well-suited for scaling to commercial production.

Light-based nanoscale devices, such as LEDs, could be important building blocks for a new generation of ultracompact, inexpensive technologies, including sensors and optical communications devices. Ultraviolet LEDs are especially important for data-storage and biological sensing devices, such as detectors for airborne pathogens. Nanowires made of a particular class of semiconductors that includes aluminum nitride, gallium nitride and indium nitride are the most promising candidates for nanoscale LEDs. But, says NIST researcher Abhishek Motayed, "The current nanowire LEDs are created using tedious nanowire manipulation methods and one-by-one fabrication techniques, which makes them unsuitable for commercial realization".

The NIST team used batch fabrication techniques, such as photolithography (printing a pattern into a material using light, similar to photography), wet etching and metal deposition. They aligned the nanowires using an electric field, eliminating the delicate and time-consuming task of placing each nanowire separately......... Posted by: Kevin      Read more         Source

May 25, 2007, 3:24 PM CT

NIST Atom Interferometry Displays New Quantum Tricks

Physicists at the National Institute of Standards and Technology (NIST) have demonstrated a novel way of making atoms interfere with each other, recreating a famous experiment originally done with light while also making the atoms do things that light just won't do. Their experiments showcase some of the extraordinary behavior taken for granted in the quantum world-atoms acting like waves and appearing in two places at once, for starters-and demonstrate a new technique that could be useful in quantum computing with neutral atoms and further studies of atomic hijinks.

The NIST experiments, described in Physical Review Letters,* recreate the historic "double-slit" experiment in which light is directed through two separate openings and the two resulting beams interfere with each other, creating a striped pattern. That experiment is a classic demonstration of light behaving like a wave, and the general technique, called interferometry, is used as a measurement tool in a number of fields. The NIST team used atoms, which, like light, can behave like particles or waves, and made the wave patterns interfere, or, in one curious situation, not.

Atom interferometers have been made before, but the NIST technique introduces some new twists. The scientists trap about 20,000 ultracold rubidium atoms with optical lattices, a lacework of light formed by three pairs of infrared laser beams that sets up an array of energy "wells," shaped like an egg carton, that trap the atoms. The lasers are arranged to create two horizontal lattices overlapping like two mesh screens, one twice as fine as the other in one dimension. If one atom is placed in each site of the wider lattice, and those lasers are turned off while the finer lattice is activated, then each site is split into two wells, about 400 nanometers apart. Under the rules of the quantum world, the atom doesn't choose between the two sites but rather assumes a "superposition," located in both places simultaneously. Images reveal a characteristic pattern as the two parts of the single superpositioned atom interfere with each other. (The effect is strong enough to image because this is happening to thousands of atoms simultaneously-see image.)......... Posted by: Sarah      Read more         Source

May 23, 2007, 7:59 PM CT

Follow the 'green' brick road?

Scientists have observed that bricks made from fly ash--fine ash particles captured as waste by coal-fired power plants--may be even safer than predicted. Instead of leaching minute amounts of mercury as some scientists had predicted, the bricks apparently do the reverse, pulling minute amounts of the toxic metal out of ambient air.

Each year, roughly 25 million tons of fly ash from coal-fired power plants are recycled, generally as additives in building materials such as concrete, but 45 million tons go to waste. Fly ash bricks both find a use for some of that waste and counter the environmental impact from the manufacture of standard bricks.

"Manufacturing clay brick requires kilns fired to high temperatures," said Henry Liu, a longtime National Science Foundation (NSF) awardee and the president of Freight Pipeline Company (FPC), which developed the bricks. "That wastes energy, pollutes air and generates greenhouse gases that contribute to global warming. In contrast, fly ash bricks are manufactured at room temperature. They conserve energy, cost less to manufacture, and don't contribute to air pollution or global warming".

Once colored and shaped, the FPC bricks are similar to their clay counterparts, both in appearance and in meeting or exceeding construction-material standards......... Posted by: Tyler      Read more         Source

May 23, 2007, 7:50 PM CT

IceTop at the bottom of the world

The University of Delaware is helping to build a huge "IceCube" at the South Pole, and it has nothing to do with cooling beverages.

"IceCube" is a gigantic scientific instrument--a telescope for detecting illusive particles called neutrinos that can travel millions of miles through space, passing right through planets.

A poet might refer to them as stardust or ghosts from outer space. But to astrophysicists, neutrinos are the high-energy messengers from the universe, formed during such cataclysmic cosmic events as exploding stars and colliding galaxies.

When the novel telescope is completed in the next several years, a cubic kilometer of ice at the "bottom of the world" will provide a new eye into the heavens and some of the most distant and violent events in the cosmos.

The telescope, its third year of construction recently concluded, is an international effort involving more than 20 institutions. The project is funded primarily by the National Science Foundation, with additional contributions from Belgium, Gera number of, Japan and Sweden, as well as the U.S. Department of Energy and the Wisconsin Alumni Research Foundation.

The lead institution for the IceCube project is the University of Wisconsin, which is working in collaboration with UD and several other universities across the nation......... Posted by: Tyler      Read more         Source

May 17, 2007, 7:28 PM CT

Colorado River streamflow history

An epic drought during the mid-1100s dwarfs any drought previously documented for a region that includes areas of Arizona, Colorado, New Mexico, Utah and Wyoming.

The six-decade-long drought was remarkable for the absence of very wet years. At the core of the drought was a period of 25 years in which Colorado River flow averaged 15 percent below normal.

The new tree-ring-based reconstruction documents the year-by-year natural variability of streamflows in the upper Colorado River basin back to A. D. 762, said the tree-ring researchers from The University of Arizona in Tucson who led the research team.

The work extends the continuous tree-ring record of upper Colorado streamflows back seven centuries earlier than prior reconstructions.

"The biggest drought we find in the entire record was in the mid-1100s," said team leader David M. Meko, an associate research professor at UA's Laboratory of Tree-Ring Research. "I was surprised that the drought was as deep and as long as it was.

Colorado River flow was below normal for 13 consecutive years in one interval of the megadrought, which spanned 1118 to 1179.

Meko contrasted that with the last 100 years, during which tree-ring reconstructed flows for the upper basin show a maximum of five consecutive years of below-normal flows......... Posted by: Tyler      Read more         Source

May 17, 2007, 7:11 PM CT

Ski Area And Mountain Watershed

Historically, people lived in lowlands. Except for logging and some agricultural uses, mountains were mostly left to the birds. But in recent decades, mountain regions in a number of parts of the world-including Vermont-have faced growing development pressures from recreation and tourism uses such as vacation homes and ski areas.

Despite these new uses, most scientific studies of soil and water in high-elevation areas have focused on the effects of traditional resource extraction, like logging. How ski resort developments impact watersheds is little understood.

In the first study to document the effects of existing ski resort development on water flows and water quality in the northeastern US, Beverley Wemple, associate professor of geography at the University of Vermont, and her colleagues, have studied two side-by-side mountain watersheds on the eastern slopes of Mount Mansfield in Vermont. The nearly pristine Ranch Brook watershed served as a control, while the adjacent West Branch watershed contains the Stowe Mountain Resort.

Their results, forthcoming in the print edition of the journal Hydrological Processes (and published online April 24, 2007," show "surprising" differences, Wemple said, between the two watersheds, including greater water volume, chloride (probably from parking lot salt runoff) and sediment (probably from land clearing) flowing out of the developed watershed......... Posted by: Tyler      Read more         Source

May 16, 2007, 10:33 PM CT

Working with Inuit Community

Research on global warming is drawing researchers in increasing numbers to the world's polar regions. But as researchers make more journeys northward, some of them find that their mission now extends beyond the ice or sediment samples they will bring back to their labs to analyze.

When Elizabeth Thomas, a graduate student in the University at Buffalo Department of Geology, travels this month to Baffin Island in the northeast Canadian Arctic, she not only will be sampling sediments from the bottom of frozen lakes, she also will be educating a native Inuit class about global warming, taking local schoolchildren on a sediment-coring field trip and may participate in a call-in radio show with translators that will be broadcast in Inuktitut, the local language.

"We go up there to do research and the local community gives us so much logistical support, I thought we should really give something back to them," said Thomas who leaves Thursday for Baffin Island in the Nunavut territory of Canada.

Thomas is traveling with a team funded by the National Science Foundation and led by Jason Briner, Ph.D., assistant professor of geology in the UB College of Arts and Sciences, who has been conducting research on Baffin Island for seven years.

Briner and his students travel to the region in the spring to sample Arctic lake sediments and analyze them to reconstruct past climates. Arctic regions show strong seasonality, so it's relatively easy to correlate changes with very fine layers in sediments......... Posted by: Tyler      Read more         Source

May 14, 2007, 8:58 PM CT

Air Quality And Weather Changes By 2050

In a first of its kind study, a research team based at Columbias Mailman School of Public Health observed that changes in urban sprawl and climate that are projected to occur in the New York City metropolitan area by the 2050s could significantly affect air quality and health in the region. Findings suggest that urban sprawl alone could result in a 1F rise in average summer temperatures and a 16 percent increase in unhealthy levels of ozone during episodes.

This is the first successful attempt to simulate both weather and air quality due to climate and land use changes at a scale that is relevant to local and regional policy makers. Using a unique modeling system, the scientists were able to link climate change, land use change, and air quality, to predict sprawling development over this region in the year 2050 in comparison to present-day conditions. This new system makes it possible for the first time to examine the separate and joint influences of land use, climate and emissions changes on future environmental conditions and resulting health implications such as asthma attacks and difficulty in breathing, ER visits and hospitalizations, and even increased risk of death for vulnerable persons.

With a population exceeding 21 million people in the greater NYC metropolitan area, ongoing urbanization puts a significant strain on natural resources and impacts air pollution levels and regional climate. The study highlights the value of modeling systems that quantitatively assess the potential impacts of changes in climate, emissions and land use on environmental health in the region......... Posted by: Tyler      Read more         Source

May 11, 2007, 5:11 PM CT

Climate swings and CO2 pulses up from the deep sea

May 10, 2007, The Earth Institute at Columbia UniversityA study released recently provides some of the first solid evidence that warming-induced changes in ocean circulation at the end of the last Ice Age caused vast quantities of ancient carbon dioxide to belch from the deep sea into the atmosphere. Researchers believe the carbon dioxide (CO2) releases helped propel the world into further warming. The study, done by scientists at the University of Colorado, Kent State University and Columbia University's Lamont-Doherty Earth Observatory, appears in the May 10 advance online version of the leading journal Science.

Atmospheric CO2, also produced by burning of fossil fuels, is believed to be largely responsible for current warming. However, researchers have known for some time that the gas also goes through natural cycles. By far most of the world's mobile carbon is stored in the oceans40 trillion metric tons, or 15 times more than in air, soil and water combined. But how this vast marine reservoir interacts with the atmosphere has been a subject of debate for the last 25 years. The study indicates what a number of researchers have long suspected, but could not prove: sometimes the oceans can release massive amounts of CO2 into the air as they overturn. "The lesson is that abrupt changes in ocean circulation in the past have affected the oceans' ability to keep carbon dioxide out of the atmosphere," said geologist Thomas Marchitto of the University of Colorado, a co-lead author. "This could help us understand how that ability might be affected by future global warming"......... Posted by: Tyler      Read more         Source

May 10, 2007, 10:42 PM CT

Seismic Monitor Installed on Underwater Volcano

Kick'em Jenny is its name, and for oceanographers working in the southeastern Caribbean Sea, this undersea volcano has been a handful.

Now, a team of marine researchers funded by the National Science Foundation (NSF) and affiliated with the Woods Hole Oceanographic Institution (WHOI) may have figured out how to tame it. This week, the scientists will begin using radio telemetry to monitor the rumblings of Kick'em Jenny from a real-time seismic monitoring device installed on the volcano.

The new technology will improve the ability of natural hazards managers to protect residents from volcanic eruptions and tsunamis, said Alex Isern, program director in NSF's Division of Ocean Sciences. "Basic oceanographic research leads to technological advances that directly benefit society--like detecting hazards--in time to make a difference," said Isern.

Located just off the north coast of the island nation of Grenada, Kick 'em Jenny is a "natural laboratory"--a submarine volcano that will eventually emerge from beneath the sea to form a new volcanic island. It is the only "live" submarine volcano in the West Indies, and has erupted at least 12 times since 1939. The last major eruption occurred in 2001.

Part of a project to develop new technology for earthquake monitoring in coastal areas, the seismic station, called a Real Time Offshore Seismic Station (RTOSS), uses an ocean-bottom seismometer deployed directly on the volcano. RTOSS allows seismic data to be transmitted by high-frequency radio to a land-based observatory in a nearby village. The data will reach the shore within milliseconds of being collected......... Posted by: Tyler      Read more         Source