November 27, 2007, 10:10 PM CT

Thermoelectric materials are one key to energy savings

Breathing new life into an old idea, MIT Institute Professor Mildred S. Dresselhaus and co-workers are in the process of developing innovative materials for controlling temperatures that could lead to substantial energy savings by allowing more efficient car engines, photovoltaic cells and electronic devices.

Novel thermoelectric materials have already resulted in a new consumer product: a simple, efficient way of cooling car seats in hot climates. The devices, similar to the more-familiar car seat heaters, provide comfort directly to the individual rather than cooling the entire car, saving on air-conditioning and energy costs.

The research is based on the principle of thermoelectric cooling and heating, which was first discovered in the early 19th century and was advanced into some practical applications in the 1960s by MIT professor (and former president) Paul Gray, among others.

Dresselhaus and his colleagues are now applying nanotechnology and other cutting-edge technologies to the field. She'll describe her work toward better thermoelectric materials in an invited talk on Monday, Nov. 26 at the annual meeting of the Materials Research Society in Boston.

Thermoelectric devices are based on the fact that when certain materials are heated, they generate a significant electrical voltage. On the other hand, when a voltage is applied to them, they become hotter on one side, and colder on the other. The process works with a variety of materials, and particularly well with semiconductors -- the materials from which computer chips are made. But it always had one big drawback: it is very inefficient......... Posted by: Kevin      Read more         Source

November 21, 2007, 4:57 AM CT

Secrets in rare cartography

Whales were the economic drivers of the 1850s. So important was this resource that the founder of the U.S. Oceanographic Office, Matthew Fontaine Maury, created a map showing the worldwide distribution of sperm and right whales in 1851.

Whale oil then was like petroleum is today, says Christopher Baruth. This is a graphic device that showed where the whales were located by type and season.

Baruth is curator of the American Geographical Society (AGS) Library, where a copy of the whale map is one of thousands of rare cartographical materials and geographical photographs.

Quietly housed at the University of Wisconsin-Milwaukee (UWM) since 1978, the AGS Library contains more than a million items, half of which are maps and charts, some dating to 15th century, and some that arent available anywhere else, even at the Library of Congress.

The value of the items in the AGS collections is compounded by their connection to the society. AGS is the oldest national geographical society in the United States, founded in 1851 in New York City.

Explorer-members, such as Charles Lindbergh, Robert Peary and Theodore Roosevelt, are among those who donated items linked to their exploits to the society over the years. Materials in the collection have been consulted not only by scholars, but also by the U.S. government during and at the end of both world wars. Today, it attracts scholars from as far away as Uzbekistan......... Posted by: Kevin      Read more         Source

November 21, 2007, 4:50 AM CT

Surface Orbital "Roughness" in Manganites

Scientists at the U.S. Department of Energy's Brookhaven National Laboratory have shown that in a class of materials called manganites, the electronic behavior at the surface is considerably different from that found in the bulk. Their findings, which were published online in the November 18, 2007, issue of Nature Materials, could have implications for the next generation of electronic devices, which will involve increasingly smaller components.

As devices shrink, the proportion of surface area grows compared to the material's volume. Therefore, it's important to understand the characteristics of a material's surface in order to predict how those materials behave and how electrons will travel across an interface, said Brookhaven physicist John Hill.

Hill and his fellow scientists were especially interested in how the outer electrons of atoms in a so-called manganite material are arranged. Manganites - consisting of a rare-earth element such as lanthanum combined with manganese and oxygen - show a huge change in electrical resistance when a magnetic field is applied. Taking advantage of this "colossal magnetoresistance effect" could be the key to developing advanced magnetic memory devices, magnetic field sensors, or transistors.

The research team, which also includes researchers from KEK (Japan), CNRS (France), Ames Laboratory, and Argonne National Laboratory, used x-ray scattering at Brookhaven's National Synchrotron Light Source and Argonne's Advanced Photon Source to study the orbital order - the arrangement of electrons in the outermost shell - of the material at the surface and in its bulk......... Posted by: Kevin      Read more         Source

November 19, 2007, 8:20 PM CT

Understanding Smog Formation

Researchers at the U.S. Department of Energy's Brookhaven National Laboratory have developed a new tool for quantitatively measuring elusive atmospheric chemicals that play a key role in the formation of photochemical smog. Better measurements will improve scientists' understanding of the mechanisms of smog formation and their ability to select and predict the effectiveness of various mitigation strategies. The Brookhaven researchers have been issued a U.S. patent for their apparatus, which is available for licensing.

The device measures atmospheric hydroperoxyl radicals - short-lived, highly reactive intermediates involved in the formation of ozone, a component of photochemical smog - in the lowest layer of Earth's atmosphere. The levels of these radicals can indicate which of a variety of chemical pathways is predominant in converting basic starting ingredients - hydrocarbons, nitrogen oxides, and water vapor - into smog in the presence of sunlight.

"Understanding the relative importance of the various pathways can help you tailor your mitigation strategies," said Brookhaven atmospheric chemist Stephen Springston, one of the inventors. "For example, are you better off spending your money reducing hydrocarbon emissions or nitrogen oxide emissions?".

"Our measurements will help predict which strategy would be most successful for a particular set of atmospheric conditions - and make modifications to the strategy as those conditions change," said co-inventor Judy Lloyd of the State University of New York at Old Westbury, who holds a guest appointment at Brookhaven Lab......... Posted by: Tyler      Read more         Source

November 18, 2007, 9:13 PM CT

New control techniques for preventing aircraft crashes

TU Delft will demonstrate how improved control techniques can reduce the risk of aircraft crashes. The demonstration involves reconstructing troubled flights such as the El Al flight which crashed in the Bijlmer area of Amsterdam in 1992 in a flight simulator and adding the newly developed technology.

The presentation in Delft forms the final phase of a research project involving the GARTEUR international research partnership (participants include TU Delft and the National Aerospace Laboratory NLR) into Fault Tolerant Control. This involves techniques for keeping damaged aircraft in the air for longer and enabling continuing flight control. The key to this is to improve control techniques which enable the aircraft to continue to be controlled. The implemented improvements are based on the analysis of flight data from aviation accidents by the NLR. This has led to improved interpretation of the (defective) condition of the aircraft.

On Wednesday 21 November, these improved techniques will be demonstrated to the general public at TU Delft. Many realistic accident scenarios will be taken as examples, including the Bijlmer crash. These will be reconstructed using TU Delfts Simona flight simulator, but this time also using the newly-developed control techniques. Simulator experiments have shown that the new techniques make it easier for the pilot to land seriously-damaged aircraft safely......... Posted by: Jim      Read more         Source

November 18, 2007, 9:03 PM CT

A New Way To Manipulate Light

Using a special hollow-core photonic crystal fibre, a team at the University of Bath, UK, has opened the door to what could prove to be a new sub-branch of photonics, the science of light guidance and trapping.

The team, led by Dr Fetah Benabid, reports on the discovery, which relates to the emerging attotechnology, the ability to send out pulses of light that last only an attosecond, a billion billionth of a second.

These pulses are so brief that they allow scientists to more accurately measure the movement of sub-atomic particles such as the electron, the tiny negatively-charged entity which moves outside the nucleus of an atom. Attosecond technology may throw light, literally, upon the strange quantum world where such particles have no definite position,only probable locations.

To make attosecond pulses, scientists create a broad spectrum of light from visible wavelengths to x-rays through an inert gas. This normally requires a gigawatt of power, which puts the technique beyond any commercial or industrial use.

But Dr Benabid's team used a photonic crystal fibre (pcf), the width of a human hair, which traps light and the gas together in an efficient way. Until now the spectrum produced by photonic crystal fibre has been too narrow for use in attosecond technology, but the team have now produced a broad spectrum, using what is called a Kagome lattice, using about a millionth of the power used by non-pcf methods......... Posted by: Kevin      Read more         Source

November 14, 2007, 9:41 PM CT

Pushing transmission rate of copper cables

You may not be able to get blood out of a turnip, but as per Penn State engineers, you can increase the data transmission of Category-7 copper cables used to connect computers to each other and the Internet.

"Working with NEXANS, the company that manufactures the cable, we have examined the possibility of sending digital data at a rate of 100 gigabits per second over 100 meters of Category-7 copper cable," says Mohsen Kavehrad, the W.L. Weiss Endowed Chair professor of electrical engineering. "These are the current, new generation of Ethernet cables".

These cables are used to connect computers within a room or a building or to create parallel computing systems.

While the long distance lines of most Internet systems are glass fiber optic cables, which are very fast, copper cable is generally used for short distances.

"In home networks, for example, it is expensive to use fiber optic cabling," says Ali Enteshari, graduate student in electrical engineering who presented the team's methods to the IEEE High Speed Study Group today (Nov. 14) in Atlanta.

All transmission cables are limited by the distance they can transmit data without degradation of the signal. Before errors and interference make the signals non-recoverable, cable systems use repeaters which are similar to computer modems to capture, correct or recover data, and resend it. The distance between repeaters depends on the cable and the approach used by the modem to correct errors......... Posted by: Kevin      Read more         Source

November 12, 2007, 9:02 PM CT

Smart dust, gassy antennas, and warp speed calculations

Tiny probes packed with instrumentation have been turned loose in a laboratory in France. The marble-sized devices are an important step on the road to long-anticipated miniaturized machines known as smart dust (picture the artificial swarm in Michael Creighton's "Prey," only without the bloodlust). The small and simple machines are being developed to be released in large numbers to collect data about the motion of fluid systems such as ocean currents and atmospheric winds.

The two centimeter probes are on the large side for smart dust (typically, miniature machines must fill a volume of a cubic centimeter or less to make the cut), still the probes' abilities are impressive for their size. They float freely underwater, measure local temperatures down to a millionth of a degree Kelvin, and send it all back wirelessly. Prior devices used for similar measurements had to remain above water or stay in one place.

The team of physicists that made the smart particles at the Université de Lyon used them to track the paths of tiny heat packets that travel through fluids, showing that the packets follow a regular pattern. The scientists are hopeful that the device will teach them more about the motion of particles in turbulent systems, including hurricanes and mixtures of reactive chemicals. - CC......... Posted by: Kevin      Read more         Source

November 8, 2007, 10:05 PM CT

Smile, protons, you're on camera

Radioactivity, discovered more than 100 years ago and studied by physicists ever since, would seem to be a relatively closed subject in science. However, since the 1960s, the pursuit of at least one open question about how nuclei spontaneously eject various particles has continued to nag experimentalists, largely because of an inability to make precise measurements of fleeting, exotic nuclei.

In a paper published this week in Physical Review Letters, an international collaboration of researchers, led by Marek Pfutzner, a physicist from Warsaw University in Poland, takes several steps toward an answer. The researchers describe a first-ever success in peering closely at radioactive decay of a rare iron isotope at the ragged edge of the known nuclear map. The tools used to achieve this result include a novel combination of advanced physics equipment and imaging technology that is found in most off-the-shelf digital cameras.

"We have proved in a direct and clear way that this extremely neutron-deficient nucleus disintegrates by the simultaneous emission of two protons," write the authors.

Pfutzner and his collaborators set out to better understand an exotic form of radioactivity -- two-proton emissions from iron-45, a nucleus with 26 protons and 19 neutrons. The stable form of iron that is most abundant on Earth has 26 protons and 30 neutrons. One possibility was that the iron-45 isotope might occasionally release an energetically linked two-proton pair, known as a diproton. Other possibilities were that the protons, whether emitted in quick succession or simultaneously, were unlinked......... Posted by: Sarah      Read more         Source

November 8, 2007, 10:02 PM CT

Mini Magnetic Sensor May Have Biomedical Applications

A tiny sensor that can detect magnetic field changes as small as 70 femtoteslas-equivalent to the brain waves of a person daydreaming-has been demonstrated at the National Institute of Standards and Technology (NIST). The sensor could be battery-operated and could reduce the costs of noninvasive biomagnetic measurements such as fetal heart monitoring. The device also may have applications in homeland security screening for explosives.

Described in the recent issue of Nature Photonics,* the prototype device is almost 1,000 times more sensitive than NIST's original chip-scale magnetometer demonstrated in 2004 ("Tiny, Atom-based Detector Senses Weak Magnetic Fields") and is based on a different operating principle. Its performance puts it within reach of matching the current gold standard for magnetic sensors, so-called superconducting quantum interference devices or SQUIDs. These devices can sense changes in the 3- to 40-femtotesla range but must be cooled to very low (cryogenic) temperatures, making them much larger, power hungry, and more expensive.

The NIST prototype consists of a single low-power (milliwatt) infrared laser and a rice-grain-sized container with dimensions of 3 by 2 by 1 millimeters. The container holds about 100 billion rubidium atoms in gas form. As the laser beam passes through the atomic vapor, researchers measure the transmitted optical power while varying the strength of a magnetic field applied perpendicular to the beam. The amount of laser light absorbed by the atoms varies predictably with the magnetic field, providing a reference scale for measuring the field. The stronger the magnetic field, the more light is absorbed......... Posted by: Kevin      Read more         Source