December 21, 2009, 8:12 AM CT

Next generation lens

Duke University engineers have created a new generation of lens that could greatly improve the capabilities of telecommunications or radar systems to provide a wide field of view and greater detail.

But the lens they fashioned doesn't look anything like a lens. While traditional lenses are made of clear substances like glass or plastic with highly polished surfaces, the new lens looks more like a miniature set of tan Venetian blinds. Yet its ability to focus the direction of electromagnetic rays passing through it dramatically surpasses that of a conventional lens, the engineers say.

The latest advance was made possible by the ability to fabricate exotic composite materials known as metamaterials. The metamaterial in these experiments is not so much a single substance, but the entire man-made structure which can be engineered to exhibit properties not readily found in nature.

The prototype lens, which measures four inches by five inches and less than an inch high, is made up of more than 1,000 individual pieces of the same fiberglass material used in circuit boards and is etched with copper. It is the precise arrangement of these pieces in parallel rows, that directs the rays as they pass through.

"For hundreds of years, lens makers have ground the surfaces of a uniform material in such a way as to sculpt the rays as they pass through the surfaces," said Nathan Kundtz, post-doctoral associate in electrical and computer engineering at Duke's Pratt School of Engineering. "While these lenses can focus rays extremely efficiently, they have limitations based on what happens to the rays as they pass through the volume of the lens......... Posted by: Kevin      Read more         Source

December 21, 2009, 8:08 AM CT

Global temperatures could rise more than expected

The kinds of increases in atmospheric carbon dioxide taking place today could have a significantly larger effect on global temperatures than previously thought, as per a newly released study led by Yale University geologists. Their findings appear December 20 in the advanced online edition of Nature Geoscience.

The team demonstrated that only a relatively small rise in atmospheric carbon dioxide (CO2) was linked to a period of substantial warming in the mid- and early-Pliocene era, between three to five million years ago, when temperatures were approximately 3 to 4 degrees Celsius warmer than they are today.

Climate sensitivitythe mean global temperature response to a doubling of the concentration of atmospheric CO2is estimated to be 1.5 to 4.5 degrees Celsius, using current models.

"These models take into account only relatively fast feedbacks, such as changes in atmospheric water vapor and the distribution of sea ice, clouds and aerosols," said Mark Pagani, associate professor of geology and geophysics at Yale and main author of the paper. "We wanted to look at Earth-system climate sensitivity, which includes the effects of long-term feedbacks such as change in continental ice-sheets, terrestrial ecosystems and greenhouse gases other than CO2"......... Posted by: Tyler      Read more         Source

December 21, 2009, 8:02 AM CT

Into the heart of the climate debate

Chemical & Engineering News (C&EN), the weekly newsmagazine of the world's largest scientific society, today published a major analysis of the divisive issues at the heart of the debate over global warming and climate change. The article appears at the conclusion of the much-publicized United Nations Climate Change Conference in Copenhagen, which sought to seal a comprehensive international agreement on dealing with global warming. An embargoed text is available to journalists upon request.

C&EN's 8,900-word cover story notes that global warming believers and skeptics actually agree on a cluster of core points:

● Earth's atmospheric load of carbon dioxide the main greenhouse gas has increased since the Industrial Revolution began in the late 1700s.

● Carbon dioxide bloat results largely from burning of coal and other fossil fuels.

● Average global temperatures have risen since 1850, with most of the warming occurring since 1970.

"But here is where the cordial agreements stop," writes Stephen K. Ritter, a senior correspondent for C&EN, a publication of the 154,000-member American Chemical Society. "At the heart of the global warming debate is whether warming is directly the result of increasing anthropogenic CO2 levels, or if it is simply part of Earth's natural climatic variation"......... Posted by: Tyler      Read more         Source

December 21, 2009, 8:00 AM CT

Soundness of old iron bridge

An unusual bowstring truss iron bridge that carried traffic across Roaring Run in Bedford County, Va. for almost 100 years is now a picturesque footbridge at the I-81 Ironto, Va. rest stop. Built in 1878, it is the oldest standing metal bridge in Virginia. In early December, a Virginia Tech undergraduate conducted a load-bearing analysis of the structure.

It may have been the first such test on the bridge. "There was no documentation of a structural analysis from when the bridge was designed," said Elaine Huffman of Bowie, Md., a student in civil engineering. As part of her research project, she did a historical survey of the bridge through a literature review, developed a computer-based structural analysis, and recently verified the computer model with an actual load test.

The bowstring truss design was patented by Z. King in 1859 under the name "Tubular Arch Bridge," Huffman learned. When the bridge was bypassed by a pipe culvert in the 1970s, it began to fall into disrepair. "The Virginia Transportation Research Council recognized the importance of the bridge as a historical landmark and worked to preserve it by restoring it and putting it into use elsewhere," said Huffman. "Much work was put into determining the original paint scheme and recreating it once the bridge was relocated. The new site was selected to maintain the function of the bridge"......... Posted by: Kevin      Read more         Source

December 18, 2009, 6:35 PM CT

High-Q Microresonators on a Silicon Wafer

Nanotechnology has already made it to the shelves of your local pharmacy and grocery: nanoparticles are found in anti-odor socks, makeup, makeup remover, sunscreen, anti-graffiti paint, home pregnancy tests, plastic beer bottles, anti-bacterial doorknobs, plastic bags for storing vegetables, and more than 800 other products.

How safe are these products and the flood of new ones about to spill out of labs across the world? A group of scientists at Washington University is devising instruments and protocols to assess the impact of nanoparticles on the environment and human health before they are sent to market.

As part of this effort, a team led by Lan Yang, Ph.D., assistant professor of electrical and systems engineering, has devised a sensor on a chip that can not only detect but also measure single particles. They expect the sensor will be able to measure nanoparticles smaller than 100 nanometers in diameter (about the size of a virus particle) on the fly.

The new sensor, an improved version of a sensor called a whispering-gallery microresonator, is described in the December 13 edition of Nature Photonics's advanced online publication.

Whispering galleries

The sensor belongs to a class of devices charmingly called whispering-gallery-mode resonators......... Posted by: Kevin      Read more         Source

December 17, 2009, 8:04 AM CT

Global warming is giving a boost to Sonoran Desert plants

Global warming is giving a boost to Sonoran Desert plants that have an edge during cold weather, as per new research.

Eventhough the overall numbers of winter annuals have declined since 1982, species that germinate and grow better at low temperatures are becoming more common.

"It's an unexpected result -- that global warming has led to an increase in cold-adapted species," said main author Sarah Kimball, a research associate at the University of Arizona in Tucson. "Because the winter rains are arriving later, they are occurring under colder temperatures".

Climate change is shifting the winter storm track so the Sonoran Desert's winter rains now generally begin in late November or early December, rather than during the balmy days of late October.

Therefore seeds that require winter rains must sprout during the cooler days of December.

"Southern Arizona has been getting hotter and drier for the last 25 or 30 years, and as a result, the desert annuals we've been studying at Tumamoc Hill have been changing," said co-author D. Lawrence Venable, the UA's director of research at Tumamoc Hill.

The scientists focused on the nine most abundant species, which comprise 74 percent of all winter annuals found at the study area......... Posted by: Tyler      Read more         Source

December 15, 2009, 11:30 PM CT

What Lies Beneath Greenland Glaciers?

Researchers who study the melting of Greenland's glaciers are discovering that water flowing beneath the ice plays a much more complex role than they previously imagined.

Scientists previously thought that meltwater simply lubricated ice against the bedrock, speeding the flow of glaciers out to sea.

Now, new studies have revealed that the effect of meltwater on acceleration and ice loss -- through fast-moving outlet glaciers that connect the inland ice sheet to the ocean -- is much more complex. This is because a kind of plumbing system evolves over time at the base of the ice, expanding and shrinking with the volume of meltwater.

Scientists are now developing new low-cost technologies to track the flow of glaciers and get a glimpse of what lies beneath the ice.

As ice melts, water trickles down into the glacier through crevices large and small, and eventually forms vast rivers and lakes under the ice, explained Ian Howat, assistant professor of earth sciences at Ohio State University. Scientists once thought that this sub-glacial water was to blame for sudden speed-ups of outlet glaciers along the Greenland coasts.

"We've come to realize that sub-glacial meltwater is not responsible for the big accelerations that we've seen for the last ten years," Howat said. "Changes in the glacial fronts, where the ice meets the ocean, are the real key"......... Posted by: Tyler      Read more         Source

December 10, 2009, 10:27 PM CT

Climate Projections Underestimate CO2 Impact

The climate appears to be 30-50 percent more sensitive to atmospheric carbon dioxide in the long term than previously thought, as per a research studypublished in Nature Geoscience yesterday.

Projections over the next hundreds of years of climate conditions, including global temperatures, may need to be adjusted to reflect this higher sensitivity.

"Climate change is affecting water supplies for cities and farms; leading to more severe droughts, hurricanes, and floods; contributing to more intense forest fires; and putting coastal communities at risk," said Secretary of the Interior Ken Salazar, who is on his way to the global climate change conference convening this week in Copenhagen. "This study and the ongoing work of our USGS researchers will help us continue to build more precise long-term projections and to prepare for the impacts of climate change on our world."

A team of scientists, led by the University of Bristol and including the U.S. Geological Survey, studied global temperatures 3.3 to 3 million years ago, finding that the averages were significantly higher than expected from the atmospheric carbon dioxide levels at the time.

These underestimates occurred because the long-term sensitivity of the Earth system was not accurately taken into account. In these earlier periods, Earth had more time to adjust to some of the slower impacts of climate change. For example, as the climate warms and ice sheets melt, Earth will absorb more sunlight and continue to warm in the future since less ice is present to reflect the sun......... Posted by: Tyler      Read more         Source

December 10, 2009, 7:46 AM CT

Breaking the Tetrahedra Packing Record

Two Kent State University professors are part of a team of scientists who recently uncovered a way to pack tetrahedra, considered to be the simplest shaped regular solids with its four triangular sides, more densely than ever before. Peter Palffy-Muhoray, professor of chemical physics and associate director of the Liquid Crystal Institute at Kent State, and Xiaoyu Zheng, assistant professor in Kent State's Department of Mathematical Sciences, along with four colleagues at the University of Michigan and one at Case Western Reserve University, have broken a world record for packing the most tetrahedra into a given volume.

Their findings will be featured in the Dec. 10 issue of Nature, one of the leading international scientific journals, in an article co-authored by the seven researchers. The article is titled "Disordered, quasicrystalline and crystalline phases of densely packed tetrahedra".

The scientists were able to obtain the highest packing fraction of 85.03, meaning tetrahedra fill 85.03 percent of the volume of the container. This shattered the prior record of 78.2 percent set by two Princeton University scientists in August 2009.

"The question of how best to pack shapes into a volume is an age-old question," Palffy-Muhoray said. "Johannes Kepler asked how to pack spheres in the early 1600s, and it was only recently proven in 2005 that the best way is to stack them like cannonballs. It is easy to understand how cubes can entirely fill space with no voids, but the packing problem is still unsolved for the simple tetrahedron. Though it's a simple object, it can't fill space like cubes, so we wondered how hard tetrahedra would pack when you squeezed them together"......... Posted by: Sarah      Read more         Source

December 7, 2009, 10:20 PM CT

Learning from Snowflake chemistry

There is more to the snowflake than its ability to delight schoolchildren and snarl traffic.

The structure of the frosty flakes also fascinate ice chemists like Purdue University's Travis Knepp, a doctoral candidate in analytical chemistry who studies the basics of snowflake structure to gain more insight into the dynamics of ground-level, or "tropospheric," ozone depletion in the Arctic.

"A lot of chemistry occurs on ice surfaces," Knepp said. "By better understanding the physical structure of the snow crystal - how it grows and why it takes a certain shape - we can get a better idea of the chemistry that occurs on that surface."

His work on snowflake shape and how temperature and humidity affect it takes place in a special laboratory chamber no larger than a small refrigerator. Knepp can "grow" snow crystals year-round on a string inside this chamber. The chamber's temperature ranges from 100-110 degrees Fahrenheit down to minus 50 degrees Fahrenheit.

Knepp, under the direction of Paul Shepson, professor and head of Purdue's Department of Chemistry, is studying snow crystals and why sharp transitions in shape occur at different temperatures. The differences he sees not only explain why no two snowflakes are identical, but also hold implications for his ozone research in the Arctic Ocean region......... Posted by: Sarah      Read more         Source