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February 19, 2007, 7:56 PM CT

Using Nano-Magnets to Enhance Medical Imaging

Using Nano-Magnets to Enhance Medical Imaging NIST studies show that molecular nanomagnets create concentration-dependent contrast in magnetic resonance imaging (MRI).
Nanoscale magnets in the form of iron-containing molecules might be used to improve the contrast between healthy and diseased tissue in magnetic resonance imaging (MRI)-as long as the concentration of nanomagnets is carefully managed-as per a new report* by scientists at the National Institute of Standards and Technology (NIST) and collaborators. Molecular nanomagnets are a new class of MRI contrast agents that may offer significant advantages, such as versatility in design, over the compounds used today.

Contrast agents are used to highlight different tissues in the body or to help distinguish between healthy and diseased tissue. NIST is working with two universities and a hospital to design, produce and test nanomolecules that might make MRI imaging more powerful and easier to perform. The new paper resolves a debate in the literature by showing that iron-containing magnets just two nanometers wide, dissolved in water, do provide reasonable contrast in non-clinical MRI images-as long as the nanomagnet concentration is below a certain threshold. (A nanometer is one billionth of a meter.) Prior studies by other research groups had reached conflicting conclusions on the utility of molecular nanomagnets for MRI, but without accounting for concentration. NIST scientists, making novel magnetic measurements, were able to monitor the molecules' decomposition and magnetic properties as the composition was varied.........

Posted by: John      Read more         Source

February 19, 2007, 7:53 PM CT

High-Frequency Cryocooler Is Tiny

High-Frequency Cryocooler Is Tiny
new cryogenic refrigerator has been demonstrated at the National Institute of Standards and Technology (NIST) that operates at twice the usual frequency, achieving a long-sought combination of small size, rapid cooling, low temperatures and high efficiency. The cryocoooler could be used to chill instruments for space and military applications, and is a significant step toward even smaller, higher-frequency versions for integrated circuits and microelectromechanical (MEM) systems.

The new cryocooler, described in the current issue of Applied Physics Letters,* is a "pulse tube" design that uses oscillating helium gas to transport heat, achieving very cold temperatures (-223 degrees C or -370 degrees F) in a matter of minutes without any cold moving parts. With cold components about 70 by 10 millimeters in size, the device operates at 120 cycles per second (hertz), in comparison to the usual 60 Hz, which enables use of a much smaller oscillator to generate gas flow, as well as faster cool-down. Because changing the size of one component can negatively affect others, the scientists used a NIST-developed computer model to find the optimal combination of frequency, pressure and component geometry.

The new cryocooler is as efficient as the low-frequency version because it uses a higher average pressure and a finer screen mesh in the regenerator-a stainless steel tube packed with screening that provides a large surface area for transfer of heat between the gas and the steel. This is a key part of the cooling process. The helium gas is pre-cooled by the screen in the regenerator before entering the pulse tube, where the gas is expanded and chilled. The cold gas reverses its direction and carries heat away from the object to be cooled before it enters the regenerator again and picks up stored heat from the screen. Then it is compressed again for a new cycle. In comparison to a prototype NIST mini-cryocooler flown on a space shuttle in 2001, the new version is about the same size but gets much colder.........

Posted by: John      Read more         Source

February 19, 2007, 7:09 PM CT

Recast Usual View of Elusive Force

Recast Usual View of Elusive Force JILA scientists measured how temperature affects the Casimir-Polder force using an apparatus that holds four small squares of glass inside a vacuum chamber.
Physicists at JILA have demonstrated that the warmer a surface is, the stronger its subtle ability to attract nearby atoms, a finding that could affect the design of devices that rely on small-scale interactions, such as atom chips, nanomachines, and microelectromechanical systems (MEMS).

The research highlights an underappreciated aspect of the elusive Casimir-Polder force, one of the stranger effects of quantum mechanics. The force arises from the ever-present random fluctuation of microscopic electric fields in empty space. The fluctuations get stronger near a surface, and an isolated neutral atom nearby will feel them as a subtle pull-a flimsy, invisible rubber band between bulk objects and atoms that may be a source of friction, for example, in tiny devices. The JILA group previously made the most precise measurement ever of Casimir-Polder, measuring forces hundreds of times weaker than ever before and at greater distances (more than 5 micrometers). JILA is a joint institute of the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder.

Now, as reported in last week's Physical Review Letters*, the JILA team has made the first measurement of the temperature dependence of this force. By using a combination of temperatures at opposite extremes-making a glass surface very hot while keeping the environment neutral and using ultracold atoms as a measurement tool-the new research underscores the power of surfaces to influence the Casimir-Polder force. That is, electric fields within the glass mostly reflect inside the surface but also leak out a little bit to greatly strengthen the fluctuations in neighboring space. As a result, says group leader and NIST Fellow Eric Cornell, "warm glass is stickier than cold glass".........

Posted by: John      Read more         Source

February 15, 2007, 6:18 AM CT

Trackstick Pro GPS

Trackstick Pro GPS
Katherine reviewed the original TrackStick GPS, but now the company has come out with the improved Pro, with 4 times the memory.

What is it? A tiny GPS recorder which, unlike real time tracking devices, records histories; it doesn't tell you where you are but where you've been. For example, it could tell you where your kids have been, verify employee driving routes, and watch large shipment routes.

How does it work? The Track Stick receives signals from twenty-four satellites orbiting the earth. With this information, the Track Stick can precisely calculate its own position anywhere on the planet to within fifteen meters. That's comforting.

When I asked the inventor, Richard Haberkern, why he came up with the Trackstick, he explained that he was intrigued with the new GPS systems years ago and came up with Trackstick as a low cost alternative for individuals and was surprised when it was snapped up by the FBI, CIA and Homeland Security.

Since it's designed to work with Google Earth, it ended up being a very useful tool in Katrina, used for evacuation route planning, and is now being added to most search and rescue teams for mapping purposes.

It's powered by a cigarette lighter, or hard wired, or how shall we say -- covertly installed.........

Posted by: John      Read more         Source

February 13, 2007, 9:09 PM CT

Water Through Nanotube Membranes

Water Through Nanotube Membranes Precise control of water transport through a nanotube membrane is demonstrated by a novel electro-chemical approach
Credit: Rensselaer Polytechnic Institute
Troy, N.Y. By fusing wet and dry nanotechnologies, scientists at Rensselaer Polytechnic Institute have found a way to control the flow of water through carbon nanotube membranes with an unprecedented level of precision. The research, which will be described in the March 14, 2007 issue of the journal Nano Letters, could inspire technologies designed to transform salt water into pure drinking water almost instantly, or to immediately separate a specific strand of DNA from the biological jumble.

Nanotube membranes have fascinated scientists with their combination of high flow rates and high selectivity, allowing them to filter out very small impurities and other organic materials like DNA and proteins from materials with high water content. The problem is that nanotube arrays are hydrophobic, strongly repelling water.

We have, at a very fundamental level, discovered that there is a new mechanism to control water transport, said Nikhil Koratkar, associate professor of mechanical engineering at Rensselaer and lead author of the paper. This is the first time that electrochemical means can be used to control the way that the water interacts with the surface of the nanotube.

A group of Rensselaer scientists led by Koratkar has found a way to use low-voltage electricity to manipulate the flow of water through nanotubes. Control of waters movement through a nanotube with this level of precision has never been demonstrated before.........

Posted by: John      Read more         Source

February 12, 2007, 9:28 PM CT

Glaciers not on simple, upward trend of melting

Glaciers not on simple, upward trend of melting
Two of Greenland's largest glaciers shrank dramatically and dumped twice as much ice into the sea during a period of less than a year between 2004 and 2005. And then, less than two years later, they returned to near their previous rates of discharge.

The variability over such a short time, reported online Feb. 9 on Science magazine's Science Express, underlines the problem in assuming that glacial melting and sea level rise will necessarily occur at a steady upward trajectory, according to lead author Ian Howat, a post-doctoral researcher with the University of Washington's Applied Physics Laboratory and the University of Colorado's National Snow and Ice Data Center. The paper comes a year after a study in the journal Science revealed that discharge from Greenland's glaciers had doubled between 2000 and 2005, leading some scientists to speculate such changes were on a steady, upward climb.

"While the rates of shrinking of these two glaciers have stabilized, we don't know whether they will remain stable, grow or continue to collapse in the near future," Howat says. That's because the glaciers' shape changed greatly, becoming stretched and thinned.

"Our main point is that the behavior of these glaciers can change a lot from year to year, so we can't assume to know the future behavior from short records of recent changes," he says. "Future warming may lead to rapid pulses of retreat and increased discharge rather than a long, steady drawdown".........

Posted by: Nora      Read more         Source

February 11, 2007, 9:42 PM CT

Future Superconducting Magnet

Future Superconducting Magnet MRI machine
A research team led by a Northwestern University physicist has identified a high-temperature superconductor -- Bi-2212, a compound containing bismuth -- as a material that might be suitable for the new wires needed to one day build the most powerful superconducting magnet in the world, a 30 Tesla magnet.

The material currently used in magnetic resonance (MR) imaging machines in both hospitals and research laboratories -- a low-temperature superconducting alloy of the metallic element niobium -- has been pushed almost as far as it can go, to around 21 Tesla. (Tesla is used to define the intensity of the magnetic field.) There are no superconducting magnet wires currently available that can generate 30 Tesla.

"A new materials technology -- such as a technology based on high-temperature superconductivity -- is required to make the huge leap from 21 Tesla to 30 Tesla," said William P. Halperin, John Evans Professor of Physics and Astronomy in the Weinberg College of Arts and Sciences at Northwestern, who led the team. "We have shown that Bi-2212 could be operated at the same temperature as is presently the case for magnets made with niobium -- 4 degrees Kelvin -- and also achieve the stable state necessary for a 30 Tesla magnet".

The findings will be published online Feb. 11 by the journal Nature Physics.........

Posted by: John      Read more         Source

February 11, 2007, 9:38 PM CT

It's not easy being green

It's not easy being green
Being a green consumer is hard work, according to new research funded by the Economic and Social Research Council (ESRC). The study highlights a need for more practical help and incentives for green consumers, if we are to achieve a more sustainable society.

The University of Leeds-led study found that consumers who try to live a sustainable lifestyle have difficulty deciding which product to buy. "Consumers find that being green or ethical is a very hard, time consuming, and emotional experience," says Dr William Young. Apart from the usual issues such as price, reliability, and colour, they have the added complication of researching and weighing up all the environmental and ethical issues before purchasing a product, he explains.

Dr Young and his colleagues interviewed green consumers about their recent major purchasing decisions for goods such as fridges and computers as well as their more routine shopping habits.

These interviews, together with several focus groups, uncovered three different types of green consumer.

Selectors are probably the largest group of green consumers in the UK population. These consumers are only green in one aspect of their lives. A selector may be an avid recycler or pay a premium for green energy but sees no contradiction in leading an otherwise consumption orientated life.........

Posted by: Nora      Read more         Source

February 8, 2007, 10:03 PM CT

Animal Studies In The Land Of The Midnight Sun

Animal Studies In The Land Of The Midnight Sun nocturnal porcupines
The temperature hovers around freezing, but the sun is up for 24 hours each day. How do animals living in the continuous light of the Arctic summer know when to sleep and when to be active? Do they maintain a 24-hour cycle of rest and activity, or does living in continuous light alter their circadian rhythm?

Answering these questions may improve our understanding of biological clocks -- the internal, genetically programmed cycle of rest and activity that affects the behavior, metabolism and physiology of all animals, including humans. A better understanding may also help solve problems -- such as shift-work fatigue, jet lag and even seasonal affective disorder -- that are associated with disruptions of biological clocks.

One scientist who has spent a lifetime pursuing these questions and finding answers that have helped build the field of biological clock research is G. Edgar Folk, Ph.D., emeritus professor of molecular physiology and biophysics at the University of Iowa Roy J. and Lucille A. Carver College of Medicine.

Folk notes that humans have a natural circadian rhythm of close to, but not exactly, 24 hours. Importantly, all biological clocks are adjustable and respond to environmental cues such as sunrise or sunset, which continuously reset the clock and keep us on a regular 24-hour schedule.........

Posted by: Nora      Read more         Source

February 8, 2007, 9:57 PM CT

Effects Of Global Warming On Antarctic

Effects Of Global Warming On Antarctic Pictured left to right, UTSA Earth and Environmental Science Assistant Professor Hongjie Xie and doctoral student Burcu Cicek.
Credit: Valentine Kass, National Science Foundation Program Manage
The Intergovernmental Panel on Climate Change report citing the detrimental.

loss of sea ice sheets in the Arctic due to global warming echoes what many in the scientific community have been saying for years. Now researchers at The University of Texas at San Antonio's Department of Earth and Environmental Science are turning their attention to the South Pole to find out if global warming is having similar effects in the frigid Antarctic region.

UTSA Earth and Environmental Science Assistant Professor Hongjie Xie and doctoral student Burcu Cicek are analyzing data collected in December following a two-week trip to the region. The pair were part of.

an international expedition that included scientists and educators from the United States, Chile and Sweden.

The National Science Foundation (NSF) funded the 6,000 mile trip which was designed to allow.

scientists to collect data aboard the Swedish icebreaker Oden during transit from Punta Arenas, Chile to the United States' McMurdo Research Station on the Antarctic continent, south of New Zealand. The Oden was chartered by NSF to break through the ice and create a 25-mile long shipping channel that would allow for the delivery of annual supplies to NSF's McMurdo Research Station. On route to Antarctica, the ship passed through 1,700 miles of extensive sea ice cover that surrounds the continent annually.........

Posted by: Nora      Read more         Source

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