August 21, 2007, 5:16 PM CT

High-speed Pulses Of Laser Light On Silicon

In the Sept. 3 issue of Optical Society of America's Optics Express, published online today, scientists announce that they have built the world's first "mode-locked silicon evanescent laser." Mode-locked evanescent lasers can deliver stable short pulses of laser light that are useful for a number of optical applications, including high-speed data transmission, multiple wavelength generation, remote sensing (LIDAR) and highly accurate optical clocks. This new work is a significant step toward the goal of combining lasers and other key optical components on silicon, providing a way to integrate optical and electronic functions on a single chip and enabling new types of integrated circuits. It introduces a more practical technology with lower cost, lower power consumption and more compact devices.Summary


Present-day computer technology depends on weak electrical currents for data communication within the silicon-based microprocessor. By causing silicon to emit light and exhibit other potentially useful optical properties, integration of photonic devices on silicon becomes possible. The problem in the past it is extremely difficult, nearly impossible, to create a laser in silicon.

Less than one year ago, a research team led by John Bowers at the University of California, Santa Barbara and Intel successfully created laser light from electrical current on silicon by placing a layer of indium phosphide (InP), an important technology in high-speed communication, above the silicon. In this new study, electrically-pumped lasers emitting 40 billion pulses of light per second were demonstrated, built on the hybrid silicon platform developed the year prior. This is the first-ever achievement of such a rate in silicon and one that matches the rates produced by other media in standard use today. These short pulses are composed of a number of evenly spaced colors of laser light, which could be separated and each used to transmit different high-speed information, replacing the need for hundreds of lasers with just one......... Posted by: Kevin      Read more         Source

August 21, 2007, 5:13 PM CT

Do higher corn prices mean less adherence to ecological principles?

Expectations of higher corn prices are leading some farmers to neglect or ignore integrated pest management strategies, and their behavior could undermine the very technologies that sustain them, University of Illinois scientists report today at the American Chemical Society meeting in Boston.

Integrated pest management (IPM) is a set of principles developed to minimize the ecological impacts of pesticides, transgenic crops and other pest management technologies. A primary goal is to slow the emergence of "resistant" insects that have adapted or evolved to evade management strategies that work. Traditional approaches for slowing the development of insect resistance include crop rotation and scouting for pests to determine whether and when to use chemicals to limit damage. Newer strategies include planting non-transgenic corn "refuges" alongside crops of transgenic corn.

(Transgenic corn hybrids, such as Bt corn, are engineered to produce toxins that target specific insect pests. Planting refuges of non-Bt corn near Bt crops slows the development of Bt-resistance in insects.).

The use of corn for biofuels production has pushed corn prices higher this year than they have been for a long time, said Kevin Steffey, a U. of I. Extension specialist in entomology and professor of crop sciences. Steffey is one of three scientists at Illinois to present at the ACS meeting......... Posted by: Jessica      Read more         Source

August 20, 2007, 7:41 AM CT

Truly sick or simply scared?

Researchers at Pacific Northwest National Laboratory have discovered a way to increase the sensitivity of test strips that will enable creation of a portable biosensor that can address a major concern linked to incidents involving chemical or nerve agents - the need to quickly distinguish between individuals who have been exposed and the "worried well".

The sensor components resemble a pregnancy test strip and a small glucose testing meter. Its development will be discussed by principal investigator Yuehe Lin at the national meeting of the American Chemical Society.

Every disease has biomarkers, a change in the proteins that announces something is wrong. Lin and his team are creating a nanoparticle "label" that can increase the ability of a sensor to detect and interpret the message of biomarkers.

"Current test strip based-immunoassay technology has very good selectivity, but it can only give a positive or negative response," Lin said.

The scientists are working with an "electrochemical immunoassay approach." This involves using the antibody of a specific disease - a protein produced in response to an invading bacterium or other foreign substance - to attract the biomarker. Lin observed that labeling a second antibody with a nanoparticle amplifies the biomarker's signal. Greater amplification means more precise readings......... Posted by: Kevin      Read more         Source

August 20, 2007, 7:39 AM CT

What Are Those Actinides Doing?

Scientists at Pacific Northwest National Laboratory are uniting theory, computation and experiment to discover exactly how heavy elements, such as uranium and technetium, interact in their environment.

As part of that effort, researchers have combined sensitive experimental measurements with fi rst principle electronic structure calculations to measure, and to really understand, the structural and bonding parameters of uranyl, the most common oxidation state of uranium in systems containing water.

The insights were achieved by PNNL scientist Bert de Jong and associates Gary Groenewold of Idaho National Laboratory and Michael Van Stipdonk of Wichita State University, employing the supercomputing resources of the William R. Wiley Environmental Molecular Sciences Laboratory (www.emsl.pnl.gov), a Department of Energy national scientifi c user facility located at PNNL.

The large number and behavior of electrons in heavy elements makes most of them extremely diffi cult to study. De Jong said that advancements in computing power and theory are enabling computational actinide chemistry to contribute significantly to the understanding and interpretation of experimental chemistry data, as well as to predicting the chemical and physical properties of heavy transition metal, lanthanide and actinide complexes......... Posted by: Sarah      Read more         Source

August 16, 2007, 9:43 PM CT

Light seems to defy its own speed limit

IT'S a speed record that is supposed to be impossible to break. Yet two physicists are now claiming they have propelled photons faster than the speed of light. This would be in direct violation of a key tenet of Einstein's special theory of relativity that states that nothing, under any circumstance, can exceed the speed of light.

Gnter Nimtz and Alfons Stahlhofen of the University of Koblenz, Gera number of, have been exploring a phenomenon in quantum optics called photon tunnelling, which occurs when a particle slips across an apparently uncrossable barrier. The pair say they have now tunnelled photons "instantaneously" across a barrier of various sizes, from a few millimetres up to a metre. Their conclusion is that the photons traverse the barrier much faster than the speed of light.

To see how far they could make photons tunnel, Nimtz and Stahlhofen sandwiched two glass prisms together to make a cube 40 centimetres on its sides. Since photons tunnel most readily over distances comparable with their wavelength, the physicists used microwaves with a wavelength of 33 cm - long enough for large tunnelling distances yet still short enough that the photons' paths can be bent by the prism.

As expected, the microwaves shone straight through the cube, and when the prisms were separated, the first prism reflected the microwaves (see Diagram). However, in accordance with theory, a few microwave photons also tunnelled across the gap separating the two prisms, continuing as if the prisms were still sandwiched together......... Posted by: Kevin      Read more         Source

August 16, 2007, 8:41 PM CT

Nanoscale blasting adjusts resistance

A new process for adjusting the resistance of semiconductor devices by carpeting a small area of the device with tiny pits, like a yard dug up by demented terriers, may be the key to a new class of magnetic sensors, enabling new, ultra-dense data storage devices. The technique demonstrated by scientists at the National Institute of Standards and Technology (NIST)* allows engineers to tailor the electrical resistance of individual layers in a device without changing any other part of the processing or design.

The tiny magnetic sensors in modern disk drives are a sandwich of two magnetic layers separated by a thin buffer layer. The layer closest to the disk surface is designed to switch its magnetic polarity quickly in response to the direction of the magnetic bit recorded on the disk under it. The sensor works by measuring the electrical resistance across the magnetic layers, which changes depending on whether the two layers have matching polarities.

As manufacturers strive to make disk storage devices smaller and more densely packed with data, the sensors need to shrink as well, but current designs are starting to hit the wall. To meet the size constraints, prototype sensors measure sensor resistance perpendicular to the thin layers, but depending on the buffer material in the sensor, two different types of sensors can be made. Giant magneto-resistance (GMR) sensors use a low-resistance metal buffer layer and are fast, but plagued by very low, difficult to detect, signals. Conversely, magnetic tunnel junction (MTJ) sensors use a relatively high-resistance insulating buffer that delivers a strong signal, but has a slower response time, too slow to keep up with a very high-speed, high-capacity drive......... Posted by: Kevin      Read more         Source

August 15, 2007, 9:21 PM CT

Ocean 'supergyre' link to climate regulator

The new research confirms the current sweeping out of the Tasman Sea past Tasmania and towards the South Atlantic is a previously undetected component of the world climate system's engine-room - the thermohaline circulation or 'global conveyor belt'.

Wealth from Oceans Flagship scientist Ken Ridgway says the current, called the Tasman Outflow, occurs at an average depth of 800-1,000 metres and may play an important role in the response of the conveyor belt to climate change.

Published this month in Geophysical Research Letters the findings confirm that the waters south of Tasmania form a 'choke-point' linking the major circulation cells in the Southern Hemisphere oceans.

"In each ocean, water flows around anticlockwise pathways or 'gyres' the size of ocean basins," Mr Ridgway says. "These gyres are the mechanism that distribute nutrients from the deep ocean to generate life on the continental shelves and slopes. They also drive the circulation of the world's oceans, creating currents and eddies and help balance the climate system by transferring ocean heat away from the tropics toward the polar region".

He says the conventional picture of the Southern Hemisphere mid-latitude circulation comprises basin-wide but quite distinct gyres contained within the Indian, Pacific and Atlantic Oceans. However model simulations had suggested that these gyres are connected......... Posted by: Tyler      Read more         Source

August 15, 2007, 9:05 PM CT

Heading for Antarctica

Its been more than 100 years since anyone has journeyed to this section of Antarcticas Amundsen Sea, but that is about to change. Next month five UTSA scientists and a Boerne High School science teacher will join a crew of 22 scientists from several countries to set sail on a two month expedition.

The trip, funded by a $533,000 National Science Foundation (NSF) research grant to UTSA, is designed to study the relationship of sea ice and the Antarctic environment. UTSAs research team will depart Sept. 1 from Punta Arenas, Chile.

The expedition, sponsored by the Arctic Research Consortium of the United States (ARCUS), is one of 20 annual trips planned involving a teacher accompanying a research expedition. ARCUS coordinates NSFs PolarTREC educational program, designed to bring educators and scientists together to explore, collaborate and experience life in the Polar Regions.

We hope that once these teachers get this hands-on experience they will be better equipped to teach science in the classroom and convey their sense of excitement to their students, particularly after going through this amazing experience, said Janet Warburton, PolarTREC program manager.

Leading UTSAs efforts is world-renowned sea ice expert Stephen Ackley, research associate professor of earth and environmental science, who has made more than a dozen trips to the Arctic and Antarctic regions. Ackleys outstanding contributions to sea ice research were recognized in 2004 when the Antarctic geographic feature, Ackley Point, was named after him by the U.S. Board of Geographical Names......... Posted by: Tyler      Read more         Source

August 15, 2007, 8:14 PM CT

Underwater Robot On Black Sea Expedition

Using a novel underwater robot, University of Delaware marine researchers will help reveal the mysteries of the Black Sea's geology and maritime history, including ages-old shipwrecks, during an international expedition that is now underway.

The Institute for Exploration and the Institute for Archaeological Oceanography at the University of Rhode Island's Graduate School of Oceanography are leading the mission, which will conduct geological and archaeological research in the Aegean and Black Seas--waterways that have served as major trade routes for centuries.

Robert Ballard, professor of oceanography at the University of Rhode Island, and president of the Institute for Exploration, is the principal investigator on the research cruise, which will include a multidisciplinary team of researchers from several nations.

"This is a truly exciting expedition that will shed light on important geological features in the Mediterranean while also uncovering vital information about ancient trade routes and the maritime history of the Black Sea," Ballard said.

Perhaps best known for locating the sunken ocean liner Titanic in 1985, Ballard has received numerous honors for scientific research and public education. He was awarded an honorary doctor of science degree by UD in 2001......... Posted by: Kevin      Read more         Source

August 10, 2007, 7:15 AM CT

Man-made soot contributed to warming

New research shows that industrial development in North America between 1850 and 1950 greatly increased the amount of black carbon--usually known as soot-- that fell on Greenland's glaciers and ice sheets. The soot impacted the ability of the snow and ice to reflect sunlight, which contributed to increased melting and higher temperatures in the region during those years. This discovery may help researchers better understand the impact of human activities on polar climates.

In an article published recently in the online edition of Science magazine, a team led by Joe McConnell and Ross Edwards from the Desert Research Institute (DRI) in Reno, Nev., report that these increased levels of soot deposits were the result of human activity and in some years were as much as eight times larger than naturally-occurring soot deposits measured in the years before 1850.

The research, funded by the National Science Foundation and NASA, indicates that these elevated levels of soot decreased the snow and ice pack's ability to reflect sunlight. This decreased level of reflectivity, or albedo, in scientific terms, allowed the surface to absorb more energy from the sun. These changes may have resulted in earlier snow melt and exposure of darker rocks, soil and sea ice, leading to warming throughout Greenland in the late 19th and early 20th century when soot levels were at their highest......... Posted by: Tyler      Read more         Source