December 7, 2009, 9:40 PM CT

Super cool atom thermometer

As physicists strive to cool atoms down to ever more frigid temperatures, they face the daunting task of developing new, reliable ways of measuring these extreme lows. Now a team of physicists has devised a thermometer that can potentially measure temperatures as low as tens of trillionths of a degree above absolute zero. Their experiment is published in the current issue of Physical Review Letters and highlighted with a Viewpoint in the December 7 issue of Physics (http://physics.aps.org.).

Physicists can currently cool atoms to a few billionths of a degree, but even this is too hot for certain applications. For example, Richard Feynman dreamed of using ultracold atoms to simulate the complex quantum mechanical behavior of electrons in certain materials. This would require the atoms to be lowered to temperatures at least a hundred times colder than what has ever been achieved. Unfortunately, thermometers that can measure temperatures of a few billionths of a degree rely on physics that doesn't apply at these extremely low temperatures.

Now a team at the MIT-Harvard Center for Ultra-Cold Atoms has developed a thermometer that can work in this unprecedentedly cold regime. The trick is to place the system in a magnetic field, and then measure the atoms' average magnetization. By determining a handful of easily-measured properties, the physicists extracted the temperature of the system from the magnetization. While they demonstrated the method on atoms cooled to one billionth of a degree, they also showed that it should work for atoms hundreds of times cooler, meaning the thermometer will be an invaluable tool for physicists pushing the cold frontier......... Posted by: Sarah      Read more         Source

December 7, 2009, 9:35 PM CT

World's smallest semiconductor laser

Air Force Office of Scientific Research and National Science Foundation-funded professor, Dr. Xiang Zhang has demonstrated at the University of California, Berkeley the world's smallest semiconductor laser, which may have applications to the Air Force in communications, computing and bio-hazard detection.

The semiconductor, called a plasmon, can focus light the size of a single protein in a space that is smaller than half its wavelength while maintaining laser-like qualities that allow it to not dissipate over time.

"Proposed almost seven years ago, scientists had been unable to demonstrate a working plasmonic laser until our experiment," said Zhang. "It is an important discovery because it has the potential to eliminate optical loss and make plasmonic-based technologies viable for a broad spectrum of applications."

"Perhaps the biggest gap in our knowledge and the reason it took so long to demonstrate this technology was our challenge of devising a realistic plasmonic laser design," he said. "We developed a strategy to get around this problem by combining semi-conductor nanowires one-thousand times thinner than a human hair with a metal surface separated by an insulating gap of only five nanometers, the size of a single protein molecule".

Because of their ultra small size, Zhang admits that an even more challenging aspect of his research has been in demonstrating how the plasmonic lasers bridge electronics, optics and photonics on the nanometer scale......... Posted by: Kevin      Read more         Source

November 30, 2009, 7:58 AM CT

Indoor radon to below current guidelines

Radon is a colorless and odorless radioactive gas that is produced by the radioactive decay of radium. Radium is a product of uranium decay and is found in trace amounts naturally in nearly all rocks, soils, and groundwater as well as building materials, plants, animals, and the human body.

Radon concentration is expressed as the amount of radiation that would be emitted by radon and its decay products in a liter of air; thus the units are picocuries per liter (pCi/L). The American Cancer Society, on its Web site, states that the estimates for lung cancer deaths caused by radon each year is between 15,400 and 21,800.

The Health Physics Society (HPS) offers the following recommendations to assist members of the public in addressing the potential risks from exposure to radon in the indoor environment:

1. The radon concentration in a dwelling can only be determined by testing; therefore, the HPS recommends that homes be tested. Approved, "do-it-yourself," short- or long-term radon test kits can be purchased directly from radon laboratories or from retail outlets. Appropriate radon test devices and qualified radon measurement specialists are those that have been approved by the National Environmental Health Association, the National Radon Safety Board, or a state radon program. Because radon concentrations undergo daily and seasonal variation, long-term radon tests (those detectors exposed in the home for more than 90 days) provide a better estimate of the annual average radon concentration.........
   
   
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November 29, 2009, 11:21 PM CT

Nanowires key to future transistors, electronics

A new generation of ultrasmall transistors and more powerful computer chips using tiny structures called semiconducting nanowires are closer to reality after a key discovery by scientists at IBM, Purdue University and the University of California at Los Angeles.

The scientists have learned how to create nanowires with layers of different materials that are sharply defined at the atomic level, which is a critical requirement for making efficient transistors out of the structures.

"Having sharply defined layers of materials enables you to improve and control the flow of electrons and to switch this flow on and off," said Eric Stach, an associate professor of materials engineering at Purdue.

Electronic devices are often made of "heterostructures," meaning they contain sharply defined layers of different semiconducting materials, such as silicon and germanium. Until now, however, scientists have been unable to produce nanowires with sharply defined silicon and germanium layers. Instead, this transition from one layer to the next has been too gradual for the devices to perform optimally as transistors.

The new findings point to a method for creating nanowire transistors.

The findings are detailed in a research paper appearing Friday (Nov. 27) in the journal Science. The paper was written by Purdue postdoctoral researcher Cheng-Yen Wen, Stach, IBM materials researchers Frances Ross, Jerry Tersoff and Mark Reuter at the Thomas J. Watson Research Center in Yorktown Heights, N.Y, and Suneel Kodambaka, an assistant professor at UCLA's Department of Materials Science and Engineering......... Posted by: Kevin      Read more         Source

November 25, 2009, 8:13 AM CT

Oceans Absorbing Carbon Dioxide More Slowly

The world's oceans are absorbing less carbon dioxide (CO2), a Yale geophysicist has found after pooling data taken over the past 50 years. With the oceans currently absorbing over 40 percent of the CO2 emitted by human activity, this could quicken the pace of climate change, as per the study, which appears in the November 25 issue of Geophysical Research Letters.

Jeffrey Park, professor of geology and geophysics and director of the Yale Institute for Biospheric Studies, used data collected from atmospheric observing stations in Hawaii, Alaska and Antarctica to study the relationship between fluctuations in global temperatures and the global abundance of atmospheric CO2 on interannual (one to 10 years) time scales. A similar study from 20 years ago found a five-month lag between interannual temperature changes and the resulting changes in CO2 levels. Park has now observed that this lag has increased from five to at least 15 months.

"No one had updated the analysis from 20 years ago," Park said. "I expected to find some change in the lag time, but the shift was surprisingly large. This is a big change".

With a longer lag time, atmospheric CO2 can no longer adjust fully to cyclical temperature fluctuations before the next cycle begins, suggesting that the oceans have lost some of their ability to absorb CO2 from the atmosphere. Weaker CO2 absorption could be caused by a change in ocean circulation or just an overall increase in the surface temperature. "Think of the oceans like soda," Park said. "Warm cola holds less fizz," Park said. "The same thing happens as the oceans warm up"......... Posted by: Tyler      Read more         Source

November 25, 2009, 8:04 AM CT

Green gas emission continues

The annual rate of increase in carbon dioxide emissions from fossil fuels has more than tripled in this decade, in comparison to the 1990s, reports an international consortium of scientists, who paint a bleak picture of the Earth's future unless "CO2 emissions [are] drastically reduced".

These CO2 emissions increased at a rate of 3.4% per year from 2000 to 2008, in contrast to 1% each year in the prior decade, researchers from the Global Carbon Project report in the current issue of Nature Geoscience. The team comprises some 30 scientists from around the world, including Scott C. Doney, senior scientist at the Woods Hole Oceanographic Institution (WHOI) and Richard A. Houghton, senior scientist and acting director of the Woods Hole Research Center (WHRC).

Since 2000, the researchers documented an overall increase of 29% in global CO2 emissions. They attributed the rise to increasing production and trade of manufactured products, especially from emerging economies, the gradual shift from oil to coal and the planet's waning capacity to absorb CO2.

Doney led a team that developed ocean-model simulations for estimating the historical variations in air-sea CO2 fluxes.

"Over the last decade, CO2 emissions have continued to climb despite efforts to control emissions," Doney said. "Preliminary evidence suggests that the land and ocean appears to be becoming less effective at removing CO2 from the atmosphere, which could accelerate future climate change"......... Posted by: Tyler      Read more         Source

November 25, 2009, 7:50 AM CT

global movement to tackle climate change

Senior doctors from across the globe have come together to form the International Climate and Health Council. Their aim is to mobilise health professionals across the world to help tackle the health effects of climate change.

The Council will be officially launched on Wednesday 25 November 2009 to coincide with a series of papers being published by the Lancet on the public health impact of strategies to reduce greenhouse gas emissions, ahead of the UN Climate Change Conference in Copenhagen.

Founding members include Professor Ian Gilmore, President of the Royal College of Physicians, Sir Muir Gray, Director of the Campaign for Greener Health Care, Dr Hamish Meldrum, Chairman of Council at the British Medical Association, Dr Fiona Godlee, Editor in Chief of the British Medical Journal and Lancet Editor, Dr Richard Horton.

Together with colleagues from Australia, Africa, Asia, Europe and the Americas, they are calling for urgent government-led international action to reduce carbon emissions and promote the universal adoption of low carbon sustainable lifestyles.

Failure to agree radical reductions in emissions spells a global health catastrophe, they say.

"Climate change is already causing major health problems," say Professor Mike Gill and Dr Robin Stott, co-chairs of the UK Climate and Health Council. "This is the first step towards a global network of health professionals which by speaking out has the potential to protect and improve the health of people in both rich and poor worlds"......... Posted by: Tyler      Read more         Source

November 25, 2009, 7:49 AM CT

Cut pollutants to save millions of lives

Tackling climate change by reducing carbon dioxide and other greenhouse emissions will have major direct health benefits in addition to reducing the risk of climate change, particularly in low-income countries, as per a series of six papers appearing today (Wed., Nov. 25) in the British journal The Lancet

Two University of California, Berkeley, authors of the papers - Kirk R. Smith, professor of global environmental health, and Michael Jerrett, associate professor of environmental health sciences - will discuss the results today at an 11:30 a.m. EST press conference in Washington, D.C.

The press conference also will include Carol Browner, director of the White House Office of Energy and Climate Change Policy, and Linda Birnbaum, director of the National Institute of Environmental Health Sciences (NIEHS) and National Toxicology Program. United Kingdom coauthors will be patched in via satellite from London, where they also will be holding a press conference.

The studies, three of them coauthored by Smith and one coauthored by Jerrett, use case studies to demonstrate the co-benefits of tackling climate change in four sectors: electricity generation, household energy use, transportation, and food and agriculture.

"Policymakers need to know that if they exert their efforts in certain directions, they can obtain important public health benefits as well as climate benefits," said Smith, who was the principal investigator in the United States for the overall research effort. "Climate change threatens us all, but its impact will likely be greatest on the poorest communities in every country. Thus, it has been called the most regressive tax in human history. Carefully choosing how we reduce greenhouse gas emissions will have the added benefit of reducing global health inequities"......... Posted by: Tyler      Read more         Source

November 23, 2009, 8:13 AM CT

Novel hydrogen storage method

Researchers at the Carnegie Institution have found for the first time that high pressure can be used to make a unique hydrogen-storage material. The discovery paves the way for an entirely new way to approach the hydrogen-storage problem. The scientists observed that the normally unreactive, noble gas xenon combines with molecular hydrogen (H2) under pressure to form a previously unknown solid with unusual bonding chemistry. The experiments are the first time these elements have been combined to form a stable compound. The discovery debuts a new family of materials, which could boost new hydrogen technologies. The paper is reported in the November 22, 2009, advanced online publication of Nature Chemistry

Xenon has some intriguing properties, including its use as an anesthesia, its ability to preserve biological tissues, and its employment in lighting. Xenon is a noble gas, which means that it does not typically react with other elements.

As main author Maddury Somayazulu, research scientist at Carnegie's Geophysical Laboratory, explained: "Elements change their configuration when placed under pressure, sort of like passengers readjusting themselves as the elevator becomes full. We subjected a series of gas mixtures of xenon in combination with hydrogen to high pressures in a diamond anvil cell. At about 41,000 times the pressure at sea level (1 atmosphere), the atoms became arranged in a lattice structure dominated by hydrogen, but interspersed with layers of loosely bonded xenon pairs. When we increased pressure, like tuning a radio, the distances between the xenon pairs changedthe distances contracted to those observed in dense metallic xenon"......... Posted by: Sarah      Read more         Source

November 23, 2009, 8:06 AM CT

Do you have a green hous?

Preliminary results from 1500 respondents show that those who own their own home are more likely to separate their rubbish (83 per cent) than those in rented accommodation (59 per cent), whilst less than one in a hundred households have solar water heating (0.5 per cent) or solar energy panels (0.5 per cent). Initial findings also show that switching off the lights in unused rooms (82 per cent) and not leaving the television on standby (67 per cent) are significantly more popular than taking fewer flights (16 per cent), car sharing (15 per cent) and not buying items because they have too much packaging (8 per cent).

Green behaviours costing the least money and effort are currently the most popular with the British public, despite the fact that 59 per cent of people believe that if things continue on their current course we will soon experience a major environmental disaster.

A fuller picture of environmental and other behaviours and attitudes based on the first annual survey of 100,000 individuals from 40,000 households for Understanding Society will be published at a later date.

With Copenhagen Climate Change Conference just a couple of weeks away, the environment is likely to remain a hot topic amongst the British public, says Professor Nick Buck of the Institute for Social and Economic Research (ISER) at the University of Essex, which is leading the new research: "One of the unique features of Understanding Society is that we speak to the same people each year, which means we can see how people's behaviours and attitudes change over time. The information we collect about how "green" people are will play a key role in informing the ongoing debate about environmental issues"......... Posted by: Tyler      Read more         Source