January 10, 2008, 10:44 PM CT

Thermoelectric Breakthrough in Silicon Nanowires

Energy now lost as heat during the production of electricity could be harnessed through the use of silicon nanowires synthesized via a technique developed by scientists with the U.S. Department of Energy's (DOE) Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California (UC) at Berkeley. The far-ranging potential applications of this technology include DOE's hydrogen fuel cell-powered "Freedom CAR," and personal power-jackets that could use heat from the human body to recharge cell-phones and other electronic devices.

"This is the first demonstration of high performance thermoelectric capability in silicon, an abundant semiconductor for which there already exists a multibillion dollar infrastructure for low-cost and high-yield processing and packaging," said Arun Majumdar, a mechanical engineer and materials scientist with joint appointments at Berkeley Lab and UC Berkeley, who was one of the principal researchers behind this research.

"We've shown that it's possible to achieve a large enhancement of thermoelectric energy efficiency at room temperature in rough silicon nanowires that have been processed by wafer-scale electrochemical synthesis," said chemist Peidong Yang, the other principal investigator behind this research, who also holds a joint Berkeley Lab and UC Berkeley appointment......... Posted by: Kevin      Read more         Source

January 8, 2008, 9:32 PM CT

Ancient France Was A Jungle

Research on a treasure trove of amber has yielded evidence that France once was covered by a dense tropical rainforest with trees similar to those found in the modern-day Amazon. The 55-million-year-old pieces of amber was discovered in the Oise River area in northern France.

In the new study, Akino Jossang and his colleagues used laboratory instruments to analyze the fossilized tree sap in an effort to link specific samples of amber to specific kinds of trees. The amber remained intact over the ages, while the trees from which it oozed disappeared. Efforts to make such connections have been difficult because amber from different sites tended to have very similar chemical compositions.

The report describes discovery of a new organic compound in amber called "quesnoin," whose precursor exists only in sap produced by a tree currently growing only in Brazil's Amazon rainforest.

Scientists say that amber probably seeped out of a similar tree growing in a tropical forest that covered France millions of years ago before Earth's continents drifted into their current positions.

"The region corresponding to modern France could have been found in a geographically critical marshy zone belonging to Africa and a tropical zone 55 million years ago extending through North Africa to the Amazon," the report states......... Posted by: William      Read more         Source

January 8, 2008, 9:25 PM CT

Efficient solar energy conversion

In the race to make solar cells cheaper and more efficient, a number of scientists and start-up companies are betting on new designs that exploit nanostructures--materials engineered on the scale of a billionth of a meter. Using nanotechnology, scientists can experiment with and control how a material generates, captures, transports, and stores free electrons--properties that are important for the conversion of sunlight into electricity.

Two nanotech methods for engineering solar cell materials have shown particular promise. One uses thin films of metal oxide nanoparticles, such as titanium dioxide, doped with other elements, such as nitrogen. Another strategy employs quantum dots--nanosize crystals--that strongly absorb visible light. These tiny semiconductors inject electrons into a metal oxide film, or "sensitize" it, to increase solar energy conversion. Both doping and quantum dot sensitization extend the visible light absorption of the metal oxide materials.

Combining these two approaches appears to yield better solar cell materials than either one alone does, as per Jin Zhang, professor of chemistry at the University of California, Santa Cruz. Zhang led a team of scientists from California, Mexico, and China that created a thin film doped with nitrogen and sensitized with quantum dots. When tested, the new nanocomposite material performed better than predicted--as if the functioning of the whole material was greater than the sum of its two individual components......... Posted by: Kevin      Read more         Source

January 8, 2008, 8:25 PM CT

Hope Diamond's fiery red glow

A study released in the January 2008 edition of the journal Geology proves that a blue diamonds rare appeal goes far beyond its beauty. The study was conducted by Jeffrey Post, curator of the National Gem Collection and mineralogist, at the Smithsonians National Museum of Natural History. Post and six other scientists probed the mysterious phosphorescence of the Hope Diamond and other natural blue diamonds and discovered a way to fingerprint individual blue diamonds.

The 45.52-carat blue Hope Diamond is the centerpiece of the National Gem Collection on display at the National Museum of Natural History and it attracts the attention of millions of visitors each year. One aspect of this famous diamond that most people do not get to see is its fiery red phosphorescence that results from exposure to ultraviolet light, which continues for more than a minute. The mysterious red phosphorescence, rarely seen in other blue diamonds, added to the Hope Diamonds mystique and allure. However, the mystery has now been solved.

Scientists at the Smithsonian and the U.S. Naval Research Laboratory measured the phosphorescence spectra of the Hope Diamond and 66 other natural blue diamonds, including the 30.82-carat Blue Heart Diamond in the Smithsonians National Gem Collection......... Posted by: Tyler      Read more         Source

January 7, 2008, 11:06 PM CT

Researchers bend light through waveguides

Scientists at the University of Illinois are the first to achieve optical waveguiding of near-infrared light through features embedded in self-assembled, three-dimensional photonic crystals. Applications for the optically active crystals include low-loss waveguides, low-threshold lasers and on-chip optical circuitry.

Key to the fabrication technique which uses multi-photon polymerization and a laser scanning confocal microscope is a self-assembled, colloidal material that exhibits a photonic band gap, said Paul Braun, a University Scholar and professor of materials science and engineering.

In prior work, reported in 2002, Brauns research group was the first to show that through multi-photon polymerization they could embed a polymer feature inside a silicon dioxide, self-assembled colloidal crystal.

Now, in a paper accepted for publication in Nature Photonics, and posted on the journals Web site, Braun and his team demonstrate actual optical activity in waveguides and cavities created in their colloidal crystals.

Taking our earlier work as a starting point, we built upon recent advances in theory and computation, improvements in materials growth techniques, and better colloidal crystallization capabilities to produce this new photonic material, said Braun, who also is affiliated with the universitys Beckman Institute, Frederick Seitz Materials Research Laboratory, and Micro and Nanotechnology Laboratory......... Posted by: Kevin      Read more         Source

January 7, 2008, 10:54 PM CT

'Electrospray' droplet research

Chemical engineers at Purdue University are the first to mathematically describe precisely how droplets form when liquids are exposed to electric fields, an advance that could have applications in areas ranging from manufacturing to medical diagnostics.

The technique of using small droplets created by subjecting liquids to electric fields is vital for a variety of applications, from a type of industrial painting called electrospraying, to a method for analyzing molecules in analytical chemistry, to manufacturing tiny micro- and nanoparticles for research and industry.

"Despite its importance, industry doesn't really understand exactly how the drops form," said Osman Basaran, the Reilly Professor of Fluid Mechanics in Purdue's School of Chemical Engineering.

New findings showed that a liquid's viscosity plays a vital role in drop formation and size, a discovery that contradicts conventional wisdom, Basaran said.

The scientists first created simulations to describe droplet formation mathematically, and then they performed experiments to support the computational work.

"Computational simulations are now making it possible to understand such phenomena," he said. "But you always want to back up simulations with experimental data if at all possible"......... Posted by: Kevin      Read more         Source

January 3, 2008, 10:05 PM CT

Insect attack may have finished off dinosaurs

Asteroid impacts or massive volcanic flows might have occurred around the time dinosaurs became extinct, but a new book argues that the mightiest creatures the world has ever known may have been brought down by a tiny, much less dramatic force biting, disease-carrying insects.

An important contributor to the demise of the dinosaurs, experts say, could have been the rise and evolution of insects, particularly the slow-but-overwhelming threat posed by new disease carriers. And the evidence for this emerging threat has been captured in almost lifelike-detail a number of types of insects preserved in amber that date to the time when dinosaurs disappeared.

There are serious problems with the sudden impact theories of dinosaur extinction, not the least of which is that dinosaurs declined and disappeared over a period of hundreds of thousands, or even millions of years, said George Poinar Jr., a courtesy professor of zoology at Oregon State University. That time frame is just not consistent with the effects of an asteroid impact. But competition with insects, emerging new diseases and the spread of flowering plants over very long periods of time is perfectly compatible with everything we know about dinosaur extinction.

This concept is outlined in detail in What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous, a book by George and Roberta Poinar, just published by Princeton University Press......... Posted by: William      Read more         Source

January 3, 2008, 10:00 PM CT

Explosive evolutionary events shaped early history

Researchers have known for some time that most major groups of complex animals appeared in the fossils record during the Cambrian Explosion, a seemingly rapid evolutionary event that occurred 542 million years ago. Now Virginia Tech paleontologists, using rigorous analytical methods, have identified another explosive evolutionary event that occurred about 33 million years earlier among macroscopic life forms uncorrelation to the Cambrian animals. They dubbed this earlier event the "Avalon Explosion".

The discovery, published in the January 4 issue of Science, suggests that more than one explosive evolutionary event may have taken place during the early evolution of animals.

The Cambrian explosion event refers to the sudden appearance of most animal groups in a geologically short time period between 542 and 520 million years ago, in the early Cambrian Period. Eventhough there were not as a number of animal species as in modern oceans, most (if not all) living animal groups were represented in the Cambrian oceans. "The explosive evolutionary pattern was a concern to Charles Darwin, because he expected that evolution happens at a slow and constant pace," said Shuhai Xiao, associate professor of geobiology at Virginia Tech. Darwins perception could be represented by an inverted cone with ever expanding morphological range, but the fossil record of the Cambrian Explosion and since is better represented by a cylinder with a morphological radiation at the base and morphological constraint afterwards......... Posted by: William      Read more         Source

January 3, 2008, 9:47 PM CT

Plate tectonics may take a break

Plate tectonics, the geologic process responsible for creating the Earths continents, mountain ranges, and ocean basins, may be an on-again, off-again affair. Researchers have assumed that the shifting of crustal plates has been slow but continuous over most of the Earths history, but a new study from scientists at the Carnegie Institution suggests that plate tectonics may have ground to a halt at least once in our planets historyand may do so again.

A key aspect of plate tectonic theory is that on geologic time scales ocean basins are transient features, opening and closing as plates shift. Basins are consumed by a process called subduction, where oceanic plates descend into the Earths mantle. Subduction zones are the sites of oceanic trenches, high earthquake activity, and most of the worlds major volcanoes.

Writing in the January 4 issue of Science, Paul Silver of the Carnegie Institutions Department of Terrestrial Magnetism and former postdoctoral fellow Mark Behn (now at Woods Hole Oceanographic Institution) point out that most of todays subduction zones are located in the Pacific Ocean basin. If the Pacific basin were to close, as it is predicted to do about in 350 million years when the westward-moving Americas collide with Eurasia, then most of the planets subduction zones would disappear with it......... Posted by: Tyler      Read more         Source

January 3, 2008, 9:41 PM CT

Life at the jolt

Scientists at the Biodesign Institute are using the tiniest organisms on the planet 'bacteria' as a viable option to make electricity. In a new study featured in the journal Biotechnology and Bioengineering, lead author Andrew Kato Marcus and his colleagues Cesar Torres and Bruce Rittmann have gained critical insights that may lead to commercialization of a promising microbial fuel cell (MFC) technology.

"We can use any kind of waste, such as sewage or pig manure, and the microbial fuel cell will generate electrical energy," said Marcus, a Civil and Environmental Engineering graduate student and a member of the institute's Center for Environmental Biotechnology. Unlike conventional fuel cells that rely on hydrogen gas as a fuel source, the microbial fuel cell can handle a variety of water-based organic fuels.

"There is a lot of biomass out there that we look at simply as energy stored in the wrong place," said Bruce Rittmann, director of the center. "We can take this waste, keeping it in its normal liquid form, but allowing the bacteria to convert the energy value to our society's most useful form, electricity. They get food while we get electricity."



Waste not

Bacteria have such a rich diversity that scientists can find a bacterium that can handle almost any waste compound in their daily diet. By linking bacterial metabolism directly with electricity production, the MFC eliminates the extra steps necessary in other fuel cell technologies. "We like to work with bacteria, because bacteria provide a cheap source of electricity," said Marcus......... Posted by: Kevin      Read more         Source