March 27, 2007, 10:05 PM CT

Physicists shine a light, produce startling liquid jet

It is possible to manipulate small quantities of liquid using only the force of light, report University of Chicago and French researchers in the March 30 issue of Physical Review Letters.

"In prior work, people figured out that you can move individual particles with lasers," said Robert Schroll, graduate student in physics at the University of Chicago and lead author of the PRL article. Now it appears that lasers can also be used to generate bulk flow in fluids. "As far as we know, we're the first to show this particular effect," Schroll said.

Schroll and Wendy Zhang, Assistant Professor in Physics at the University of Chicago, carried out the project with Rgis Wunenburger, Alexis Casner and Jean-Pierre Delville of the University of Bordeaux I. The technique might offer a new way to control the flow of fluids through extremely narrow channels for biomedical and biotechnological applications.

In their experiment, the Bordeaux researchers shined a laser beam through a soapy liquid. The laser produced a long jet of liquid that broke up into droplets after traversing a surprisingly long distance.

"I thought this was just so weird because I know when liquid is supposed to break up, and this one isn't doing it," Zhang said.

Physicists know that lasers can set liquid in motion through heating effects, but heat was not a factor in this case. The liquid used in the Bordeaux experiment is a type that absorbs very little light. Heating the liquid would require more light absorption. In this case, the Chicago team's theoretical calculations matched the Bordeaux team's experimental results: the mild force of the light itself drives the liquid motion......... Posted by: Kevin      Read more         Source

March 25, 2007, 7:26 PM CT

Linear arrays of nanotubes

Despite the attractive electrical properties and physical features of single-walled carbon nanotubes, incorporating them into scalable integrated circuits has proven to be a challenge because of difficulties in manipulating and positioning these molecular scale objects and in achieving sufficient current outputs.

Now, scientists at the University of Illinois, Lehigh University and Purdue University have developed an approach that uses dense arrays of aligned and linear nanotubes as a thin-film semiconductor material suitable for integration into electronic devices.

The nanotube arrays can be transferred to plastic and other unusual substrates for applications such as flexible displays, structural health monitors and heads-up displays. The arrays also can be used to enhance the performance of devices built with conventional silicon-based chip technology.

"The aligned arrays represent an important step toward large-scale integrated nanotube electronics," said John A. Rogers, a Founder Professor of Materials Science and Engineering at Illinois, and corresponding author of a paper accepted for publication in the journal Nature Nanotechnology, and posted on its Web site.

To create nanotube arrays, the scientists begin with a wafer of single-crystal quartz, on which they deposit thin strips of iron nanoparticles. The iron acts as a catalyst for the growth of carbon nanotubes by chemical vapor deposition. As the nanotubes grow past the iron strips, they lock onto the quartz crystal, which then aligns their growth......... Posted by: Kevin      Read more         Source

March 19, 2007, 10:31 PM CT

Pinpointing Traffic Accident "Hotspots"

Ohio State University researchers have created software that can identify traffic accident hotspots on state roadways.

The software is publicly available and can be adapted for use by any state, said Christopher Holloman, associate director of the Statistical Consulting Service in Ohio State's Department of Statistics. Currently, the Ohio State Highway Patrol is using it to help position its cruisers during major holidays.

"We can make predictions for every major roadway in Ohio, under all possible road conditions, for every hour of the day, for every day of the week," Holloman said.

The software relies on reports of injuries and fatalities from the highway patrol, and incorporates statistics about what makes accidents happen.

Common accident causes such as speeding or alcohol consumption are fairly easy to model using computers, Holloman explained. Others -- such as when a driver will be distracted by a cell phone -- are impossible. So the software makes general forecasts.

"Everyone would love to be able to predict exactly where and when the next crash would be, but there are just too a number of factors involved, and too much randomness to do that," he said. "We can confidently make broad statements, like whether a particular piece of roadway is riskier at a particular time"......... Posted by: Jim      Read more         Source

March 19, 2007, 9:45 PM CT

How Computers and Electronics Work

Scientists have made an important advance in the emerging field of 'spintronics' that may one day usher in a new generation of smaller, smarter, faster computers, sensors and other devices, as per findings reported in today's issue of the journal Nature Nanotechnology.

The research field of 'spintronics' is concerned with using the 'spin' of an electron for storing, processing and communicating information.

The research team of electrical and computer engineers from the Virginia Commonwealth University's School of Engineering and the University of Cincinnati examined the 'spin' of electrons in organic nanowires, which are ultra-small structures made from organic materials. These structures have a diameter of 50 nanometers, which is 2,000 times smaller than the width of a human hair. The spin of an electron is a property that makes the electron act like a tiny magnet. This property can be used to encode information in electronic circuits, computers, and virtually every other electronic gadget.

"In order to store and process information, the spin of an electron must be relatively robust. The most important property that determines the robustness of spin is the so-called 'spin relaxation time,' which is the time it takes for the spin to 'relax.' When spin relaxes, the information encoded in it is lost. Therefore, we want the spin relaxation time to be as long as possible," said corresponding author Supriyo Bandyopadhyay, Ph.D., a professor in the Department of Electrical and Computer Engineering at the VCU School of Engineering......... Posted by: Kevin      Read more         Source

March 15, 2007, 6:09 PM CT

Ice created in nanoseconds

Sandias huge Z machine, which generates termperatures hottter than the sun, has turned water to ice in nanoseconds.

However, dont expect anything commercial just yet: the ice is hotter than the boiling point of water.

"The three phases of water as we know them cold ice, room temperature liquid, and hot vapor are actually only a small part of waters repertory of states," says Sandia researcher Daniel Dolan. "Compressing water customarily heats it. But under extreme compression, it is easier for dense water to enter its solid phase [ice] than maintain the more energetic liquid phase [water]".

Sandia is a National Nuclear Security Administration (NNSA) laboratory.

In the Z experiment, the volume of water shrank abruptly and discontinuously, consistent with the formation of almost every known form of ice except the ordinary kind, which expands. (One might wonder why this ice shrank instead of expanding, given the common experience of frozen water expanding to wreck garden hoses left out over winter. The answer is that only "ordinary" ice expands when water freezes. There are at least 11 other known forms of ice occurring at a variety of temperatures and pressures.).

"This work," says Dolan, "is a basic science study that helps us understand materials at extreme conditions"......... Posted by: Kevin      Read more         Source

March 14, 2007, 10:32 PM CT

A Boost for Hydrogen Fuel Cell Research

The development of hydrogen fuel cells for vehicles, the ultimate green dream in transportation energy, is another step closer. Scientists with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and Argonne National Laboratory (ANL) have identified a new variation of a familiar platinum-nickel alloy that is far and away the most active oxygen-reducing catalyst ever reported.

The slow rate of oxygen-reduction catalysis on the cathode - a fuel cell's positively charged electrode - has been a primary factor hindering development of the polymer electrolyte membrane (PEM) fuel cells favored for use in vehicles powered by hydrogen.

"The existing limitations facing PEM fuel cell technology applications in the transportation sector could be eliminated with the development of stable cathode catalysts with several orders of magnitude increase in activity over today's state-of-the-art catalysts, and that is what our discovery has the potential to provide," said Vojislav Stamenkovic, a scientist with dual appointments in the Materials Sciences Division of both Berkeley Lab and Argonne.

Stamenkovic and Argonne senior scientist Nenad Markovic are the corresponding authors of a study whose results are now available online from the journal Science. The paper, entitled Improved Oxygen Reduction Activity on Pt3Ni(111) via Increased Surface Site Availability, reports a platinum-nickel alloy that increased the catalytic activity of a fuel cell cathode by an astonishing 90-fold over the platinum-carbon cathode catalysts used today......... Posted by: Sarah      Read more         Source

March 11, 2007, 8:43 PM CT

Magnetic Field In A Turbulent Fluid

Understanding the origin and behavior of the magnetic fields of planets and stars is the goal of research being carried out by a number of teams from all over the world. The VKS1 collaboration (CEA2, CNRS3,4, Ecole normale suprieure in Lyon3, Ecole normale suprieure in Paris4) has succeeded in creating in the laboratory a magnetic field in a highly turbulent flow of liquid sodium. Eventhough the extreme conditions specific to astrophysical and geophysical environments cannot all be reproduced in the laboratory, the magnetic field observed shows remarkable similarities with magnetic fields observed in the cosmos. The findings represent a significant advance in the understanding of the mechanisms at work in the formation of natural magnetic fields. They are published in Physical Review Letters dated 26 January 2007.

Most of the astrophysical objects which surround us (planets, stars and galaxies) have a magnetic field, whose origin is poorly understood. Such magnetic fields can play a major role in the evolution of various structures throughout the Universe. The Earth's magnetic field, which is very probably caused by the movement of liquid iron in the core, not only makes compass needles point north, but also protects us from the harmful effects of cosmic rays and the solar wind......... Posted by: Kevin      Read more         Source

March 5, 2007, 4:59 PM CT

Life Can Be a Strain

Powered by mere vibrations or the movement of magnets, novel sensors and transmitters developed by a small company in Vermont are changing the way engineers are looking at fatigue.

Communicating wirelessly via the Internet to engineers halfway across the world, the embedded sensors developed by MicroStrain--a small business based in Williston, Vt., and supported by the National Science Foundation (NSF)--are revealing how objects as diverse as the Liberty Bell, enormous mining trucks and even human knees respond to daily use.

By monitoring strain levels and tracking the cumulative effects of fatigue, the researchers' ultimate goal is to supplant the nearly universal system of "replace by this date" with a smarter approach of replacing components based upon the actual operating loads components experience.

"By calculating the amount of fatigue that a component has been exposed to, it is possible to repair or replace the component only when required," said engineer Steve Arms, president of MicroStrain. "Properly implemented, this can significantly reduce costs".

MicroStrain has received several NSF Small Business Innovation Research Program awards to support the development of cutting-edge sensors and compatible wireless transmitters that can carry their information to monitors around the globe......... Posted by: Kevin      Read more         Source

March 5, 2007, 4:15 PM CT

Designer Molecule to Clean Up Fluorocarbons

The chemical bond between carbon and fluorine is one of the strongest in nature, and has been both a blessing and a curse in the complex history of fluorocarbons. Now, in a powerful demonstration of the relatively new field of "computational chemistry," scientists at the National Institute of Standards and Technology (NIST) and the Interdisciplinary Network of Emerging Science and Technology group (INEST, sponsored by Philip Morris USA) have designed-in a computer-a wholly theoretical molecule to pull the fluorine out of fluorocarbons.*.

At sea level, the strong C-F bond makes fluorocarbons thermally and chemically stable. As a result, fluorocarbons have been used in a number of commercial applications including refrigerants, pesticides and non-stick coatings. In the upper atmosphere, however, high-energy photons and highly reactive ozone molecules can break apart fluorocarbons, with the well-known consequence of a depleted ozone layer and increased ultraviolet radiation at ground level. A determined chemist can break down fluorocarbons at ground level with certain organometallic compounds, but the reactions take a long time at very high temperatures. Other known reagents are both highly toxic and inefficient, so chemists have been searching for an economical and environmentally friendly method to dispose of fluorocarbons......... Posted by: Sarah      Read more         Source

March 5, 2007, 4:06 PM CT

Measuring Cell Mechanical Properties

Scientists at the National Institute of Standards and Technology (NIST) have developed a microelectromechanical system (MEMS) cell-stretcher that can measure the mechanical properties of a living cell, such as its ability to stick to a surface. The new device is expected to enable novel studies of cell mechanics, which influence basic cell functions such as growth and division, and diseases such as sickle cell anemia and asthma.

The prototype device, described in a new paper,* is thought to bethe only technique for studying bulk mechanical properties of a single, whole cell while it is spreading out and sticking to a substrate as it would in the body, says the designer, NIST bioengineer David Serrell. Other biomechanical test methods focus on individual cell components or entire tissues.

The heart of the NIST device is a circular cell platform 200 micrometers wide, a tiny fleck just barely visible to the naked eye. The two halves of the circle can be pulled as far as 100 micrometers apart under computer control, while the force needed to separate them is measured by sensors. In a demonstration using a connective tissue cell, the cell is placed on the center of the platform, allowed to spread and adhere for several hours, and then pulled slowly apart until it detaches. In NIST experiments, the cells let go of the substrate at a force of about 1500 nanonewtons. (One nanonewton is the approximate amount of force mandatory to break a single chemical bond between two atoms.)......... Posted by: Kevin      Read more         Source