October 1, 2007, 10:08 PM CT

Amazon Forest Unexpectedly Resilient to Drought

The extensive forests of South America's Amazon are turning out to be tougher than expected when it comes to withstanding the onslaughts of a changing climate. A team of U.S. and Brazilian researchers using the insightful eyes of two NASA satellites has shown that one of the worst droughts in decades could not stop the undisturbed regions of the Amazon forest from "greening up."

The Amazon drought of 2005 reached its peak just as the region's annual dry season was beginning, from July through September. Eventhough the double whammy of the parched conditions might be expected to slow the growth of the forest's leafy canopy, in much of the drought-stricken areas the canopy became significantly greener -- an indication of increased photosynthetic activity.

"Instead of 'hunkering down' during a drought as you might expect, the forest responded positively to drought, at least in the short term," said study author Scott R. Saleska, an assistant professor of ecology and evolutionary biology at the University Of Arizona. "It's a very interesting and surprising response".

The new finding contradicts a prominent global climate model that predicts the Amazon forest would begin to "brown down" after just a month of drought. The model also predicts an eventual forest collapse, shifting the ecosystem permanently from a thick, evergreen, broad-leaved forest to a grassy savanna......... Posted by: Tyler      Read more         Source

October 1, 2007, 9:35 PM CT

Nanotube forests grown on silicon chips

Engineers have shown how to grow forests of tiny cylinders called carbon nanotubes onto the surfaces of computer chips to enhance the flow of heat at a critical point where the chips connect to cooling devices called heat sinks.

The carpetlike growth of nanotubes has been shown to outperform conventional "thermal interface materials." Like those materials, the nanotube layer does not require elaborate clean-room environments, representing a possible low-cost manufacturing approach to keep future chips from overheating and reduce the size of cooling systems, said Placidus B. Amama, a postdoctoral research associate at the Birck Nanotechnology Center in Purdue's Discovery Park.

Scientists are trying to develop new types of thermal interface materials that conduct heat more efficiently than conventional materials, improving overall performance and helping to meet cooling needs of future chips that will produce more heat than current microprocessors. The materials, which are sandwiched between silicon chips and the metal heat sinks, fill gaps and irregularities between the chip and metal surfaces to enhance heat flow between the two.

The method developed by the Purdue scientists enables them to create a nanotube interface that conforms to a heat sink's uneven surface, conducting heat with less resistance than comparable interface materials currently in use by industry, said doctoral student Baratunde A. Cola......... Posted by: Kevin      Read more         Source

October 1, 2007, 9:27 PM CT

Diminished ice leads to Northwest Passage opening

Arctic sea ice during the 2007 melt season plummeted to the lowest levels since satellite measurements began in 1979, as per scientists at the University of Colorado at Boulder's National Snow and Ice Data Center.

The average sea ice extent for the month of September was 1.65 million square miles (4.28 million square kilometers), the lowest September on record, shattering the prior record for the month by 23 percent, which was set in 2005. At the end of the melt season, September 2007 sea ice was 39 percent below the long-term average from 1979 to 2000.

If ship and aircraft records from before the satellite era are taken into account, sea ice may have fallen by as much as 50 percent from the 1950s. The September rate of sea ice decline since 1979 is now more than 10 percent per decade, said the CU-Boulder research team.

NSIDC is part of the Cooperative Institute for Research in Environmental Sciences, a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration.

Arctic sea ice has long been recognized as a sensitive climate indicator, said CU-Boulder Research Professor Mark Serreze of CIRES and NSIDC. "Computer projections have consistently shown that as global temperatures rise, the sea ice cover will begin to shrink," he said. "While many natural factors have certainly contributed to the overall decline in sea ice, the effects of greenhouse warming are now coming through loud and clear"......... Posted by: Tyler      Read more         Source

September 27, 2007, 10:08 PM CT

Nanotubes To Detect and Repair Cracks in Aircraft Wings

Adding even a small amount of carbon nanotubes can go a long way toward enhancing the strength, integrity, and safety of plastic materials widely used in engineering applications, as per a new study.

Scientists at Rensselaer Polytechnic Institute have developed a simple new technique for identifying and repairing small, potentially dangerous cracks in high-performance aircraft wings and a number of other structures made from polymer composites.

By infusing a polymer with electrically conductive carbon nanotubes, and then monitoring the structure's electrical resistance, the scientists were able to pinpoint the location and length of a stress-induced crack in a composite structure. Once a crack is located, engineers can then send a short electrical charge to the area in order to heat up the carbon nanotubes and in turn melt an embedded healing agent that will flow into and seal the crack with a 70 percent recovery in strength.

Real-time detection and repair of fatigue-induced damage will greatly enhance the performance, reliability, and safety of structural components in a variety of engineering systems, as per principal investigator Nikhil A. Koratkar, an associate professor in Rensselaer's Department of Mechanical, Aerospace and Nuclear Engineering......... Posted by: Kevin      Read more         Source

September 27, 2007, 9:43 PM CT

Solving A Dragonfly Flight Mystery

Dragonflies adjust their wing motion while hovering to conserve energy, as per a Cornell University study of the insect's flight mechanics. The revelation contradicts prior speculation that the change in wing motion served to enhance vertical lift.

The Cornell physicists came to their conclusions after analyzing high speed images of dragonflies in action. The insects have two pairs of wings, which sometimes move up and down in harmony. At other times the front set of wings flap out of sync with the back set.

The physicists observed that dragonflies maximized their lift, when accelerating or taking off from a perch, by flapping both sets of wings together. When they hover, however, the rear wings flap at the same rate as the front, but with a different phase (imagine two people clapping at the same speed, but with one person's clap delayed relative to the other).

The physicists' analysis of the out-of-sync motion showed that while it didn't help with lift, it minimized the amount of power they had to expend to stay airborne, allowing them to conserve energy while hovering in place.

The research will be detailed in a forthcoming issue of Physical Review Letters. The authors are Z. Jane Wang and David Russell......... Posted by: Ashley      Read more         Source

September 26, 2007, 8:42 PM CT

North America's northernmost lake affected by global warming

Analyses conducted by scientists from Universit Lavals Center for Northern Studies reveal that the continents northernmost lake is affected by climate change. In an article would be reported in the September 28 edition of Geophysical Research Letters, the international research team led by Universit Laval researchers Warwick Vincent and Reinhard Pienitz reports that aquatic life in Ward Hunt Lake, a body of water located on a small island north of Ellesmere Island in the Canadian Arctic, has undergone major transformations within the last two centuries. The speed and range of these transformationsunprecedented in the lakes last 8,000 yearssuggest that climate change correlation to human activity could be at the source of this phenomenon.

The scientists conclusions are based on the analysis of a sediment core extracted in the center of Ward Hunt Lake in August 2003. This 18 centimeter long sediment core containing algae pigments and diatom remnants was used by the scientists as a biological archive in order to determine the diversity and abundance of aquatic life-forms in the lake over the last 8,450 years.

Analysis of the deepest layers of sediment revealed a very small number of algae as well as only minor variations in concentration. However, the top two centimeters of the core, which correspond to the last 200 years, showed abrupt changes in the lakes algae population: during that period, chlorophyll a concentration, a pigment found in every species in the lake, increased by a factor of 500. A type of diatom typical of very cold environments also made its first appearance during the same period. The absence of diatoms and the low pigment concentration below the top 2.5 centimeters of the core suggest that the lake waccording tomanently frozen in the past, explains lead author and Center for Northern Studies researcher Dermot Antoniades......... Posted by: Tyler      Read more         Source

September 26, 2007, 8:31 PM CT

Pinning Down Spin of Surface Atoms

Researchers who dream of shrinking computers to the nanoscale look to atomic spin as one possible building block for both processor and memory, yet setting the spin of an atom, let alone measuring it, has been a challenge.

Now, University of California, Berkeley, physicists have succeeded in measuring the spin of a single atom, moving one step closer to quantum computers and "spintronic" devices built from nanoscale transistors based on atomic spin.

"From a technical point of view, this demonstrates a new ability to engineer, fabricate and measure spin-polarized nanostructures at the single atom level," said Michael F. Crommie, UC Berkeley professor of physics. "Now that I can see an atom's spin, I can ask, 'What can I do with that atomic spin? Can I manipulate it? Can I use it, change it?' This means we can now start incorporating it into other structures."

Crommie and colleagues at UC Berkeley and the Center for Computational Materials Science (CCMS) at the Naval Research Laboratory in Washington, D.C., recently reported their success in the journal Physical Review Letters.

At the core of today's digital computers are billions of tiny transistor circuits that, because they can exist in two states, are used to represent the binary digits, or "bits" 0 and 1, which are the basis of all computer manipulations......... Posted by: Sarah      Read more         Source

September 26, 2007, 8:23 PM CT

Ancient whale fall found from Ano Nuevo Island

A fossilized whale skeleton excavated 20 years ago amid the stench and noise of a seabird and elephant seal rookery on California's Ano Nuevo Island turns out to be the youngest example on the Pacific coast of a fossil whale fall and the first in California, as per University of California, Berkeley, paleontologists.

Whale falls, first recognized in the 1980s, are whale carcasses that fall to the deep-ocean floor where, like an oasis in the desert, they attract a specialized group of clams, crabs and worms that feed for up to decades on the oil-rich bones and tissues.

Some researchers think these random, deep-ocean oases are stepping stones for organisms moving from one ocean floor environment to another - whether a hot vent, a cold seep or a whale carcass - in search of sustenance from energy-rich chemicals.

"The fossil whale fall shows that these deep-sea communities didn't need particularly large whales as a source of nutrients - in fact, the fossil whale from Año Nuevo Island was no longer than a VW bug," said Nick Pyenson, a graduate student in UC Berkeley's Department of Integrative Biology.

Pyenson and museum scientist David M. Haasl, both of UC Berkeley's Museum of Paleontology, published their findings in this week's online edition of the journal Biology Letters......... Posted by: William      Read more         Source

September 26, 2007, 7:50 PM CT

Arctic heat wave stuns climate change researchers

Unprecedented warm temperatures in the High Arctic this past summer were so extreme that scientists with a Queen's University-led climate change project have begun revising their forecasts.

"Everything has changed dramatically in the watershed we observed," reports Geography professor Scott Lamoureux, the leader of an International Polar Year project announced yesterday in Nunavut by Indian and Northern Affairs Minister Chuck Strahl. "It's something we'd envisioned for the future - but to see it happening now is quite remarkable."

One of 44 Canadian research initiatives to receive a total of $100 million (IPY) research funding from the federal government, Dr. Lamoureux's new four-year project on remote Melville Island in the northwest Arctic brings together researchers and educators from three Canadian universities and the territory of Nunavut. They are studying how the amount of water will vary as climate changes, and how that affects the water quality and ecosystem sustainability of plants and animals that depend on it.

The information will be key to improving models for predicting future climate change in the High Arctic, which is critical to the everyday living conditions of people living there, particularly through the lakes and rivers where they obtain their drinking water......... Posted by: Tyler      Read more         Source

September 25, 2007, 8:57 PM CT

Greenland snow melting hit record high

A new NASA-supported study reports that 2007 marked an overall rise in the melting trend over the entire Greenland ice sheet and, remarkably, melting in high-altitude areas was greater than ever at 150 percent more than average. In fact, the amount of snow that has melted this year over Greenland could cover the surface size of the U.S. more than twice.

Marco Tedesco, a research scientist at the Joint Center for Earth Systems Technology, cooperatively managed by NASA's Goddard Space Flight Center in Greenbelt, Md., and the University of Maryland at Baltimore County, used satellite data to compare average snow melting from 1988-2006 with what has taken place this summer. He observed that in high altitude areas over 1.2 miles above sea level, the melting index -- an indicator of where melting is occurring and for how long - was significantly higher than average. Melting over those areas occurred 25-30 days longer this year than the observed average in the prior 19 years.

"When snow melts at those high altitudes and then refreezes, it can absorb up to four times more energy than fresh, unthawed snow," said Tedesco. "This can affect Earth's energy budget by changing how much radiation from the sun is absorbed by the Earth versus that reflected back into the atmosphere. Refrozen snow can also alter the snow density, thickness and snow-water content." Tedesco's findings were published Sept. 25 in the American Geophysical Union's Eos newspaper......... Posted by: Tyler      Read more         Source