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July 8, 2007, 10:22 PM CT

Electronic 'crowd behavior' revealed

Electronic 'crowd behavior' revealed
Like crowds of people, microscopic particles can act in concert under the right conditions. By exposing crowd behavior at the atomic scale, researchers discover new states and properties of matter. Now, ultrafast lasers have revealed a previously unseen type of collective electronic behavior in semiconductors, which may help in the design of optoelectronic devices. The work at JILA, a joint venture of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder, is described in a new paper in the Proceedings of the National Academy of Sciences.*.

Design of optoelectronic devices, like the semiconductor diode lasers used in telecommunications, currently involves a lot of trial and error. A designer trying to use basic theory to calculate the characteristics of a new diode laser will be off by a significant amount because of subtle interactions in the semiconductor that could not be detected until recently.

To shed light on these interactions, the JILA team used a highly sensitive and increasingly popular method of manipulating laser light energy and phase (the point in time when a single light wave begins) to reveal the collective behavior of electronic particles that shift the phase of any deflected light. Their work is an adaptation of a technique that was developed years ago by other scientists to probe correlations between spinning nuclei as an indicator of molecular structure (and led to a Nobel prize).........

Posted by: Nora      Read more         Source


July 5, 2007, 9:13 PM CT

Creates Transparent Transistors

Creates Transparent Transistors
The Viterbi School's Chongwu Zhou and a team of scientists have created the first prototype of a new design for semiconductors, devices in which transparent electronics are built on top of a flexible transparent base. These devices have the potential of serving as new kinds of displays, including "e-paper" and heads-up displays in automobile windshields or even eyeglasses.

The transistor nanowires also provide a way to embed reliable displays and computing power in thin "smart cards," as per Zhou, an associate professor in the Ming Hsieh Department of Electrical Engineering and in the USC College Department of Chemistry. Zhou was recently named the first holder of the Viterbi School's Jack Munushian Early Career Chair.

His research was published in the recent issue of Nature Nanotechnology.

The fabrication of the prototype nanowire transistors was done in Zhou's laboratory, working from designs co-created by David Janes of the Purdue University School of Electrical Engineering and Computer Engineering, who works in Purdue's Birck Nanotechnology Center; and by Tobin J. Marks, holder of the Vladimir N. Ipatieff chair of chemistry at Northwestern University, who has a joint appointment in Northwestern's Department of Materials Science and Engineering. (See Purdue's press announcement.).........

Posted by: John      Read more         Source


July 4, 2007, 5:05 AM CT

Stellar fireworks are ablaze in galaxy NGC 4449

Stellar fireworks are ablaze in galaxy NGC 4449
Credit: NASA, ESA, A. Aloisi (STScI/ESA), and The Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration
Hundreds of thousands of vibrant blue and red stars are visible in this new image of galaxy NGC 4449 taken by the NASA/ESA Hubble Space Telescope. Hot bluish white clusters of massive stars are scattered throughout the galaxy, interspersed with numerous dustier reddish regions of current star formation. Massive dark clouds of gas and dust are silhouetted against the flaming starlight.

NGC 4449 has been forming stars since several billion years ago, but currently it is experiencing a star formation event at a much higher rate than in the past. This unusual explosive and intense star formation activity qualifies as a starburst. At the current rate, the gas supply that feeds the stellar production would only last for another billion years or so.

Starbursts commonly occur in the central regions of galaxies, but NGC 4449 has a more widespread star formation activity, since the very youngest stars are observed both in the nucleus and in streams surrounding the galaxy.

A "global" starburst like NGC 4449 resembles primordial star forming galaxies which grew by merging with and accreting smaller stellar systems. Since NGC 4449 is close enough to be observed in great detail, it is the ideal laboratory for the investigation of what may have occurred during galactic formation and evolution in the early Universe.........

Posted by: Edwin      Read more         Source


June 25, 2007, 7:39 PM CT

Safety of Nanotechnology: Risk Vs Benefit

Safety of Nanotechnology: Risk Vs Benefit
There is no doubt that nanotechnology has the potential to make the world a better place, said Project on Emerging Nanotechnologies Chief Scientist Andrew Maynard. But if consumers and other stakeholders are not convinced that the benefits outweigh the risks, a number of applications will not see the light of day. Likewise, if the benefits are unclear and the risks uncertain, the products of nanotechnology will be a hard sell.

Dr. Maynards remark is in his presentation today before a public meeting of the Presidents Council of Advisors on Science and Technology (PCAST). He spoke as part of a panel devoted to addressing and managing the potential health, environmental and safety risks of nanotechnology.

Nanotechnology is turning our world upside down.It also is shaking up our understanding of what makes something harmful and how we deal with that, as per Maynard. He described the current U.S. policy toward managing the possible health and safety risks of nanotechnologies as approaching 21st century technologies with a 20th century mindset.

Maynard called on the federal government to develop a goal-driven risk research strategy to provide decision-makersincluding regulators, industry and consumerswith the scientific information they need to help develop and use nanotechnologies as safely as possible. He suggested an international approach to this challenge based on a set of strategic research questions developed by thirteen top researchers last year which were reported in the journal Nature.........

Posted by: John      Read more         Source


Sun, 24 Jun 2007 15:06:06 GMT

Deep insight, simple representations

Deep insight, simple representations
At its best, the scientific method can reduce profound questions about our universe to their barest essence and answer them compellingly with simple observations. The greatest experiments achieve the most complete distillations because of the principles and theories that guide them and the knowledge that has already been well established. Once this context is internalized, even grainy images or barely visible spikes in a line of noise can become moving pieces of art.

Here’s the image that got me thinking about this most recently:

It’s a postcard that Walther Gerlach sent to Niels Bohr after Gerlach’s experiment seemed to confirm Bohr’s prediction about the magnetic moment of atoms. The caption says “Attached [is] the experimental proof of directional quantization. We congratulate [you] on the confirmation of your theory.” According to the Physics Today article where I found this figure, at the time these results were considered “among the most compelling evidence for quantum theory.” This is an amazing distillation. Magnetic field off, no splitting. Magnetic field on, splitting. Magnetic moment is quantized. For background, some complications, and to learn about how cigar smoking in the lab played a crucial role in this discovery you’ll have to read the article.

I don’t want to talk about the details of the experiment here though. Instead I want to ask for other great scientific distillations. There must be excellent examples of this from the early days of molecular biology. Something like: this spot is radioactive, this spot is not, so DNA is the molecule of inheritance. Let’s see your nominations. Include a link to an image if you have one.

How far can this go? In theoretical physics, people often discuss reducing all of physics to a single theory, maybe something you could fit on a t-shirt. But why must the universe on a t-shirt be represented by an equation? With such a theory in hand, could there be a simple representation of an elegant observation that, in context, encapsulates the nature of the universe?

Posted by: Andre      Read more     Source


June 20, 2007, 10:55 AM CT

Case researchers may have solved

Case researchers may have solved
"Nothing there," is what Case Western Reserve University physicists concluded about black holes after spending a year working on complex formulas to calculate the formation of new black holes. In nearly 13 printed pages with a host of calculations, the research may solve the information loss paradox that haccording toplexed physicists for the past 40 years.

Case physicists Tanmay Vachaspati, Dejan Stojkovic and Lawrence M. Krauss report in the article, "Observation of Incipient Black Holes and the Information Loss Problem, that has been accepted for publication by Physical Review D.

"It's complicated and very complex," noted the researchers, regarding both the general problem and their particular approach to try to solve it.

The question that the physicists set out to solve is: what happens once something collapses into a black hole" If all information about the collapsing matter is lost, it defies the laws of quantum physics. Yet, in current thinking, once the matter goes over the event horizon and forms a black hole, all information about it is lost.

"If you define the black hole as some place where you can lose objects, then there is no such thing because the black hole evaporates before anything is seen to fall in," said Vachaspati.........

Posted by: Edwin      Read more         Source


June 20, 2007, 9:32 AM CT

Don't overlook urban soil

Don't overlook urban soil
If you were looking for fertile soil, its doubtful youd begin your search in most U.S. cities. After all, urban soils are often viewed as drastically disturbed soils with low fertility. However, new research by a team of researchers working in Baltimore discovered that surface soil characteristics were not necessarily infertile and varied widely, making it difficult to define or describe a typical urban soil. Eventhough the more conspicuous effects of urban disturbances on soil have been considered by researchers, other factors linked to urban land transformations have received limited attention. These various effects create a mosaic of soil conditions, ranging from natural to highly disturbed soil profiles.

To examine the effects of land use and cover on soils, scientists from USDA Forest Service and the University of Maryland Baltimore County sampled and measured the physical and chemical properties of surface soils from 122 Baltimore plots. Scientists report their findings in the May-June 2007 issue of Soil Science Society of America Journal.

This research was part of the Baltimore Ecosystem Study (BES), an ongoing effort to understand urban ecosystems, which is funded by the National Science Foundation.

As per the authors of the study, Land use and cover may serve as an indicator of disturbance, site history, management, and the urban environment. By measuring the chemical and physical differences among various soil plots, researchers hoped to determine whether land use or cover was the cause of differences and what specific soil properties best differentiate the land-use and cover types.........

Posted by: Nora      Read more         Source


June 15, 2007, 12:48 AM CT

Researchers Help Find New Sub-atomic Particle

Researchers Help Find New Sub-atomic Particle
The Fermilab accelerator complex in Illinois accelerates sub-atomic particles close to the speed of light. Converting energy into mass, the Tevatron collider produces millions of proton-antiproton collisions per second, maximizing the chance for discovery of new particles.
The discovery was made by physicists of the DZero experiment at the U.S. Department of Energy's Fermi National Accelerator Laboratory in Batavia, Ill.

Discovery and measurement of the particle's mass will provide new understanding about the basic building blocks of matter.

Local participants in the experiment were physics faculty members Z.D. Greenwood, Lee Sawyer and Markus Wobisch; former post-doctoral researcher Julie Kalk; and current post-doctoral scientists Mike Arov and Joe Steele.

"We've never seen anything like this before," said Sawyer, who is academic director of Tech's physics and chemistry programs. "What is really neat about this is that we have models that predict these things' existence. Discovery is verification of the Standard Model of particle physics".

The Tech team built electronics for part of the DZero detector, which records the path, energy and charge of the particles released during the sub-atomic collisions that are necessary for the project.

"That was a big job," said Greenwood, an associate professor of physics. "It was designed and put together right here at Tech".

In describing Tech's contribution to this frontier of physics, Greenwood said, "Because we are dealing with fundamental particles and trying to understand and contribute to material that describes how the whole universe works, we're necessarily operating at the cutting edge".........

Posted by: John      Read more         Source


June 13, 2007, 9:58 AM CT

First buoy to monitor ocean acidification launched

First buoy to monitor ocean acidification launched
The first buoy to monitor ocean acidification has been launched in the Gulf of Alaska. Attached to the 10-foot-diameter buoy are sensors to measure climate indicators.

Acidification is a result of carbon dioxide absorbed by the seas.

"The instruments will measure the air-sea exchange of carbon dioxide, oxygen and nitrogen gas in addition to the pH, a measure of ocean acidity, of the surface waters," said Steven Emerson of the University of Washington, the project's lead scientist. "This is the first system specifically designed to monitor ocean acidification".

The buoy is anchored in water nearly 5,000 meters deep. Once it hit the water, the buoy immediately began to transmit data via satellite.

The buoy is part of a National Science Foundation (NSF) grant awarded to oceanographers at the University of Washington and Oregon State University, working in collaboration with researchers at NOAA's Pacific Marine Environmental Laboratory (PMEL), and at Fisheries and Oceans Canada and the Institute of Ocean Sciences in Sidney, B.C.

"Information from this buoy will lead to a better understanding of ocean acidification--a growing threat to the world's oceans--by helping researchers determine exactly how physical and biological processes affect carbon dioxide in the north Pacific Ocean," said Fred Lipschultz, program director in NSF's division of ocean sciences. The grant was funded through NSF's Biocomplexity in the Environment emphasis area on Carbon and Water in the Earth System.........

Posted by: Nora      Read more         Source


June 11, 2007, 4:27 PM CT

Viable Design for Spin-Based Electronics

Viable Design for Spin-Based Electronics
Physicists at the University of California, San Diego have proposed a design for a semiconductor computer circuit based on the spin of electrons. They say the device would be more scalable and have greater computational capacity than conventional silicon circuits.

The "spintronic"-or spin-based electronic-device, described this week in the journal Nature, would extend the scope of conventional electronics by encoding information with the magnetic-or spin-state of electrons, in addition to the charge of the electrons. The scientists used a novel geometry to overcome the weakness of the magnetic signal, the current limitation to developing spintronics in silicon semiconductors.

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"The breakthrough of our research is the device geometry, the way it is activated, and the way it could be integrated in electronic circuits," said Lu J. Sham, a professor of physics at UCSD and the senior author on the paper. "All of these features are novel and our results show for the first time a spin-based semiconductor circuit".

One advantage of spintronics is that it shrinks the size of the circuit that is needed to perform a given logic operation. The scientists say that their proposed device has other important advantages compared with conventional electronics.........

Posted by: John      Read more         Source


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