June 10, 2009, 8:42 PM CT

Maybe it's raining less than we thought

It's conventional wisdom in atmospheric science circles: large raindrops fall faster than smaller drops, because they're bigger and heavier. And no raindrop can fall faster than its "terminal speed"its speed when the downward force of gravity is exactly the same as the upward air resistance.

Now two physicists from Michigan Technological University and his colleagues at the Universidad Nacional Autnoma de Mxico (National University of Mexico) have discovered that it ain't necessarily so.

Some smaller raindrops can fall faster than bigger ones. In fact, they can fall faster than their terminal speed. In other words, they can fall faster than drops that size and weight are supposed to be able to fall.

And that could mean that the weatherman has been overestimating how much it rains.

The findings of Michigan Tech physics professors Alexander Kostinski and Raymond Shawco-authors with Guillermo Montero-Martinez and Fernando Garcia-Garcia on a paper scheduled for publication online June 13, 2009, in the American Geophysical Union's journal Geophysical Research Letterscould improve the accuracy of weather measurement and prediction.

The scientists gathered data during natural rainfalls at the Mexico City campus of the National University of Mexico. They studied approximately 64,000 raindrops over three years, using optical array spectrometer probes and a particle analysis and collecting system. They also modified an algorithm or computational formula to analyze the raindrop sizes......... Posted by: Tyler      Read more         Source

June 5, 2009, 5:00 AM CT

Graphene May Have Advantages Over Copper

The unique properties of thin layers of graphite-known as graphene-make the material attractive for a wide range of potential electronic devices. Scientists have now experimentally demonstrated the potential for another graphene application: replacing copper for interconnects in future generations of integrated circuits.

In a paper reported in the June 2009 issue of the IEEE journal Electron Device Letters, scientists at the Georgia Institute of Technology report detailed analysis of resistivity in graphene nanoribbon interconnects as narrow as 18 nanometers.

The results suggest that graphene could out-perform copper for use as on-chip interconnects-tiny wires that are used to connect transistors and other devices on integrated circuits. Use of graphene for these interconnects could help extend the long run of performance improvements for silicon-based integrated circuit technology.

"As you make copper interconnects narrower and narrower, the resistivity increases as the true nanoscale properties of the material become apparent," said Raghunath Murali, a research engineer in Georgia Tech's Microelectronics Research Center and the School of Electrical and Computer Engineering. "Our experimental demonstration of graphene nanowire interconnects on the scale of 20 nanometers shows that their performance is comparable to even the most optimistic projections for copper interconnects at that scale. Under real-world conditions, our graphene interconnects probably already out-perform copper at this size scale."........ Posted by: Kevin      Read more         Source

June 5, 2009, 4:56 AM CT

Nanoscale zipper cavity

Physicists at the California Institute of Technology (Caltech) have developed a nanoscale device that can be used for force detection, optical communication, and more. The device exploits the mechanical properties of light to create an optomechanical cavity in which interactions between light and motion are greatly strengthened and enhanced. These interactions, notes Oskar Painter, associate professor of applied physics at Caltech, and the principal investigator on the research, are the largest demonstrated to date.

The device and the work that led to it are described in a recent issue of the journal Nature

The fact that photons of light, despite having no mass, nonetheless carry momentum and can interact with mechanical objects is an idea that dates back to Kepler and Newton. The mechanical properties of light are also known to limit the precision with which one can measure an object's position, since simply by using light to do the measurement, you apply a force and disturb the object.

It was important to consider these so-called back-action effects in the design of devices to measure weak, classical forces. Such considerations were part of the development of gravity-wave detectors like the Laser Interferometer Gravitational-Wave Observatory (LIGO). These sorts of interferometer-based detectors have also been used at much smaller scales, in scanning probe instruments used to detect or image atomic surfaces or even single electron spins......... Posted by: Kevin      Read more         Source

June 3, 2009, 5:10 AM CT

Control heat in large data centers

Approximately a third of the electricity consumed by large data centers doesn't power the computer servers that conduct online transactions, serve Web pages or store information. Instead, that electricity must be used for cooling the servers, a demand that continues to increase as computer processing power grows.

And the trend toward cloud computing will expand the need for both servers and cooling.

At the Georgia Institute of Technology, scientists are using a 1,100-square-foot simulated data center to optimize cooling strategies and develop new heat transfer models that can be used by the designers of future facilities and equipment. The goal is to reduce the portion of electricity used to cool data center equipment by as much as 15 percent.

"Computers convert electricity to heat as they operate," said Yogendra Joshi, a professor in Georgia Tech's Woodruff School of Mechanical Engineering. "As they switch on and off, transistors produce heat, and all of that heat must be ultimately transferred to the environment. If you are looking at a few computers, the heat produced is not that much. But data centers generate heat at the rate of tens of megawatts that must be removed".

Summaries of the research have been reported in the Journal of Electronic Packaging and International Journal of Heat and Mass Transfer and presented at the Second International Conference on Thermal Issues in Emerging Technologies, Theory and Applications. The research has been sponsored by the U.S. Office of Naval Research, and by the Consortium for Energy Efficient Thermal Management......... Posted by: Kevin      Read more         Source

June 3, 2009, 5:01 AM CT

Memory with a twist

Electronic memory chips may soon gain the ability to bend and twist as a result of work by engineers at the National Institute of Standards and Technology (NIST). As published in the July 2009 issue of IEEE Electron Device Letters,* the engineers have found a way to build a flexible memory component out of inexpensive, readily available materials.

Though still not ready for the marketplace, the new device is promising not only because of its potential applications in medicine and other fields, but because it also appears to possess the characteristics of a memristor, a fundamentally new component for electronic circuits that industry researchers developed in 2008.** NIST has filed for a patent on the flexible memory device (application #12/341.059).

Electronic components that can flex without breaking are coveted by portable device manufacturers for a number of reasonsand not just because people have a tendency to drop their mp3 players. Small medical sensors that can be worn on the skin to monitor vital signs such as heart rate or blood sugar could benefit patients with conditions that require constant maintenance, for example. Though some flexible components exist, creating flexible memory has been a technical barrier, as per NIST researchers.

Hunting for a solution, the scientists took polymer sheetsthe sort that transparencies for overhead projectors are made fromand experimented with depositing a thin film of titanium dioxide, an ingredient in sunscreen, on their surfaces. Instead of using expensive equipment to deposit the titanium dioxide as is traditionally done, the material was deposited by a sol gel process, which consists of spinning the material in liquid form and letting it set, like making gelatin. By adding electrical contacts, the team created a flexible memory switch that operates on less than 10 volts, maintains its memory when power is lost, and still functions after being flexed more than 4,000 times......... Posted by: Kevin      Read more         Source

June 1, 2009, 6:56 PM CT

Nanosecond pressure jump

A new method to induce protein folding by taking the pressure off of proteins is up to 100 times faster than prior methods, and could help guide more accurate computer simulations for how complex proteins fold, as per research by a team of University of Illinois researchers accepted for publication in the journal Nature Methods and posted on the journal's Web site May 31.

Martin Gruebele, the James R. Eiszner Professor of Chemistry at the U. of I. and corresponding author of the paper, says that prodding proteins to fold by suddenly removing high pressure (a technique also known as "pressure jumping") through electrical bursting makes for a "kindler, gentler way" of inducing proteins to fold.

"When you're increasing the pressure on something, you're squeezing the atoms and making them come closer to one another," Gruebele said, "but you're not necessarily causing the very complicated changes to the microscopic motion that occur when you change the temperature. Pressure is a simpler variable than temperature".

In order to carry out their biomolecular functions, proteins fold from a chaotic, random coil that looks like spaghetti strands floating in boiling water to their native state as an orderly, well-defined but compact structure.

From the point-of-view of the protein, Gruebele said, pressurizing it to about 2,500 atmospheres is much less disruptive than, say, cranking up the temperature by 30 degrees......... Posted by: Kevin      Read more         Source

June 1, 2009, 4:58 AM CT

Population responses to climate change

Biologists have for several years modeled how different species are likely to respond to climate change. Most such studies ignore differences between populations within a species and the interactions between species, in the interest of simplicity. An article in the recent issue of BioScience, by Eric Post of Pennsylvania State University and five colleagues, shows how these limitations can be avoided. Their approach, which relies on multi-stage analyses of how populations fluctuate over time, could allow biologists to model responses to climate change with improved accuracy. In particular, the approach could help identify regions where local populations are vulnerable to climate change, and it could elucidate species interactions that may not be obvious.

The article concentrates on recent analyses by Post and others of yellow-billed cuckoos, caribou/wild reindeer, elk and red deer, and wolves and moose. Continent-wide and hemisphere-wide responses depended both on local weather and on broader climate patterns, and all species showed marked variation among populations. The pattern of responses, Post and his colleagues report, "suggests a strong role for species interactions in buffering responses to climate." For example, local populations near the northern edge of a species' range often seem to be more directly affected by climate than do populations near the southern edge, where biological interactions typically complicate responses to climate change......... Posted by: Tyler      Read more         Source

June 1, 2009, 4:57 AM CT

Who will pick up the bill?

Ocean acidification, a direct result of increased CO2 emission, is set to change the Earth's marine ecosystems forever and may have a direct impact on our economy, resulting in substantial revenue declines and job losses.

Intensive fossil-fuel burning and deforestation over the last two centuries have increased atmospheric CO2 levels by almost 40%, which has in turn fundamentally altered ocean chemistry by acidifying surface waters. Fish levels and other sea organisms such as planktons, crabs, lobsters, shrimp and corals are expected to suffer, which could leave fishing communities at the brink of economic disaster.

Published recently, Monday, 1 June, in IOP Publishing's Environmental Research Letters, the paper 'Anticipating ocean acidification's economic consequences on commercial fisheries' suggests a series of measures to manage the impact that declining fishing harvests and revenue loss will have on a wide range of businesses from commercial fishing to wholesale, retail and restaurants.

Ocean acidification and declining carbonate ion concentration in sea water could directly damage corals and mollusks which all depend on sufficient carbonate levels to form shells successfully. Subsequent losses of prey such as plankton and shellfish would also alter food webs and intensify competition among predators for nourishment......... Posted by: Tyler      Read more         Source

May 28, 2009, 5:19 AM CT

Sea-level rise may pose greatest threat

The melting of the Greenland Ice Sheet this century may drive more water than previously thought toward the already threatened coastlines of New York, Boston, Halifax and other cities in the northeastern United States and Canada, as per new research.

Results of the study are being published this week in Geophysical Research Letters They suggest that moderate to high rates of ice melt from Greenland may shift ocean circulation by about 2100, causing sea levels off the northeast coast of North America to rise by about 30 to 51 centimeters (12 to 20 inches) more than other coastal areas.

The research builds on recent reports that have observed that sea level rise could adversely affect North America, and its findings suggest that the situation is even more urgent than previously believed.

"If the Greenland melt continues to accelerate, we could see significant impacts this century on the northeast U.S. coast from the resulting sea level rise," says scientist Aixue Hu, the paper's main author. Hu is at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. "Major northeastern cities are directly in the path of the greatest rise".

A study in Nature Geoscience in March warned that warmer water temperatures could shift ocean currents in a way that would raise sea levels off the Northeast by about eight inches more than the average global sea level rise that is expected with global warming......... Posted by: Tyler      Read more         Source

May 24, 2009, 8:57 PM CT

Multiferroics

Multiferroics are materials in which unique combinations of electric and magnetic properties can simultaneously coexist. They are potential cornerstones in future magnetic data storage and spintronic devices provided a simple and fast way can be found to turn their electric and magnetic properties on and off. In a promising new development, scientists with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) working with a prototypical multiferroic have successfully demonstrated just such a switch -- electric fields.

"Using electric fields, we have been able to create, erase and invert pn junctions in a calcium-doped bismuth ferrite film," said Ramamoorthy Ramesh of Berkeley Lab's Materials Sciences Division (MSD), who led this research.

"Through the combination of electronic conduction with the electric and magnetic properties already present in the multiferroic bismuth ferrite, our demonstration opens the door to merging magnetoelectrics and magnetoelectronics at room temperature".

Ramesh, who is also a professor in the Department of Materials Science and Engineering and the Department of Physics at UC Berkeley, has published a paper on this research that is now available in the on-line edition of the journal Nature Materials The paper is titled: "Electric modulation of conduction in multiferroic......... Posted by: Kevin      Read more         Source