Friday, September 10, 2010

A CASE FOR EXERCISING

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There is now another good reason to exercise. Besides burning calories, exercise restores the sensitivity of neurons involved in the control of satiety (feeling full), which in turn contributes to reduced food intake and consequently weight loss. This is the conclusion of a study led by Brazilian researchers at the University of Campinas, and the findings will be published in the online, open access journal PLoS Biology. This disclosure may bring hope to over 40% of the population that suffers from weight problems and obesity around the world.

The increase in obesity has become one of the most important clinical-epidemiological phenomena. Factors such as changing eating habits and a sedentary lifestyle both have a role in the pathogenesis of this disease. It is postulated that excessive consumption of fat creates failures in the signal transmitted by neurons controlling satiety in a region of the brain called the hypothalamus. These failures can lead to uncontrollable food intake and, consequently, obesity.

The group led by José Barreto C. Carvalheira demonstrated that exercising obese rodents showed signals of restored satiety in hypothalamic neurons and decreased food intake. "In obese animals, exercise increased IL-6 and IL-10 protein levels in the hypothalamus, and these molecules were crucial for increasing the sensitivity of the most important hormones, insulin and leptin, which control appetite," Carvalheira explained. Physical activity contributes to the prevention and treatment of obesity, not only by increasing energy expenditure but also by modulating the signals of satiety and reducing food intake.

Physical activity has always been considered a cornerstone in the treatment of obesity, however, only now have the effects of exercise on the control of body weight been understood. Thus, these findings, besides reinforcing the necessity for regular exercise also change the current paradigm established between physical activity and weight loss.

PLoS

MODERATE DRINKING: HEALTH BENEFITS OR NOT?

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While moderate drinking – one to less than three drinks per day – is linked to a decrease in mortality in middle-aged and older adults, there is also concern that the health benefits of moderate drinking have been overestimated. A new study of the association between drinking and mortality during a 20-year period, which controlled for confounding factors such as previous problem drinking, confirms an association of moderate drinking and reduced mortality among older adults.

Results will be published in the November 2010 issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.

"Although alcohol misuse is linked to many medical conditions, considerable epidemiological evidence indicates that moderate alcohol use is related to reduced total mortality," explained Charles J. Holahan, a professor in the department of psychology at The University of Texas at Austin and corresponding author for the study. "We expected that a substantial part of the health benefits associated with moderating drinking were due to confounding factors associated with alcohol abstention. For example, abstainers may include former problem drinkers with health problems and individuals who are atypical in terms of sociodemographic and social-behavioral factors that may increase health risk."

"None of the studies that have examined the association of drinking and mortality and cardiovascular disease have been experimental studies in which a group of people was randomly chosen to drink a particular amount of alcohol or to not drink alcohol," observed Alison A. Moore, professor of medicine and psychiatry in the David Geffen School of Medicine at the University of California, Los Angeles. "All have been observational studies, meaning those in which persons who consume varying amounts of alcohol are compared with those who don't. Because conditions in these observational studies are not controlled and the characteristics of persons who choose to drink varying amounts of alcohol or not differ quite a bit, it is impossible to prove that alcohol consumption causes reduced risks for coronary heart disease, diabetes or mortality."

For this study, using data gathered from a larger study of late-life patterns of drinking and related problems, researchers followed 1,824 older adults (1,142 men, 682 women) between the ages of 55 and 65 years of age – who were former or current drinkers – for 20 years. The information collected included: daily alcohol consumption, sociodemographic factors, former problem-drinking status, health factors, and social behavioral factors. Death was confirmed primarily by a death certificate.

"Controlling only for age and gender, mortality was highest among abstainers and heavy drinkers and lowest in moderate drinkers," said Holahan. "Controlling for former problem drinking status, existing health problems, and key sociodemographic and social-behavioral factors substantially reduced the mortality effect for abstainers compared to moderate drinkers. However, even after adjusting for all covariates, abstainers and heavy drinkers continued to show increased mortality risks of 49 percent and 42 percent, respectively, compared to moderate drinkers."

"In other words, the association of moderate drinking and reduced mortality among older adults is reduced but still present when taking into consideration factors that affect both alcohol consumption and mortality," said Moore. "For example, socioeconomic status has been a consistent factor in the link between alcohol consumption and mortality. That is, those with higher income and/or education are less likely to be abstainers and to die."

Thus, the health benefits of moderate drinking are complicated because a number of underlying health risks are correlated with later life abstention, Holahan noted.

"Our findings demonstrate that abstainers were significantly more likely to have had prior drinking problems, to be obese, and to smoke cigarettes than moderate drinkers and scored significantly higher than moderate drinkers on health problems, depressive symptoms, and avoidance coping," he said. "In addition, abstainers were significantly lower than moderate drinkers on socioeconomic status, physical activity, number of close friends, and quality of friend support and significantly less likely to be married than moderate drinkers. Moreover, all of these factors that were associated with abstention significantly predicted mortality."

Both Holahan and Moore reiterated that any health benefits are linked to moderation. "Older persons drinking alcohol should remember that consuming more than two drinks a day exceeds recommended alcohol consumption guidelines in the U.S. and is associated with increased falls, a higher risk of alcohol use problems, and potential adverse interactions with medications," said Holahan. "Moreover, nondrinkers should not start drinking to try to enhance their health, and individuals who are or plan to become pregnant, or have alcohol problems or medical conditions that could be worsened by alcohol should not drink."

ATTC

CAN THE WORLD BE POWERED MAINLY BY SOLAR AND WIND ENERGY?

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Continuous research and development of alternative energy could soon lead to a new era in human history in which two renewable sources — solar and wind — will become Earth's dominant contributor of energy, a Nobel laureate said here at a special symposium at the American Chemical Society's 240th National Meeting.

Walter Kohn, Ph.D., who shared the 1998 Nobel Prize in Chemistry, noted that total oil and natural gas production, which today provides about 60 percent of global energy consumption, is expected to peak about 10 to 30 years from now, followed by a rapid decline. He is with the University of California, Santa Barbara.

"These trends have created two unprecedented global challenges", Kohn said. "One is the threatened global shortage of acceptable energy. The other is the unacceptable, imminent danger of global warming and its consequences."

Kohn noted that these challenges require a variety of responses. "The most obvious is continuing scientific and technical progress providing abundant and affordable alternative energies, safe, clean and carbon-free," he said.

Because the challenges are global in nature, the scientific and technical work should enjoy a maximum of international cooperation, which fortunately is beginning to evolve, he said.

The global photovoltaic energy production increased by a factor of about 90 and wind energy by a factor of about 10 over the last decade. He expects vigorous growth of these two effectively inexhaustible energies to continue during the next decade and beyond, thereby leading to a new era, the SOL/WIND era, in human history, in which solar and wind energy have become the earth's dominant energy sources.

Another important issue, incumbent primarily on developed countries, whose population has pretty much leveled off, is reduction in per capita energy consumption, Kohn said.

"A striking example is the U.S. per capita consumption of gasoline, approximately 5 times higher than the global average," he said. "The less developed world, understandably, aims to bring their standard of living to a level similar to that of the highly developed countries; in return they should stabilize their growing populations."

Kohn noted that he is impressed by students on his campus who spent their own collective funds to fully solarize an athletic building. "When it comes to providing leadership by young people in the area of energy conservation and energy efficiency and global warming — they are fantastic," he said. "It is a major social commitment for our times."

(Photo: Stephen Strathdee)

American Chemical Society

SELF-CLEANING TECHNOLOGY FROM MARS CAN KEEP TERRESTRIAL SOLAR PANELS DUST FREE

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Find dusting those tables and dressers a chore or a bore? Dread washing the windows? Imagine keeping dust and grime off objects spread out over an area of 25 to 50 football fields. That's the problem facing companies that deploy large-scale solar power installations, and scientists presented the development of one solution — self-dusting solar panels ― based on technology developed for space missions to Mars.

In a report at the 240th National Meeting of the American Chemical Society (ACS), they described how a self-cleaning coating on the surface of solar cells could increase the efficiency of producing electricity from sunlight and reduce maintenance costs for large-scale solar installations.

"We think our self-cleaning panels used in areas of high dust and particulate pollutant concentrations will highly benefit the systems' solar energy output," study leader Malay K. Mazumder, Ph.D. said. "Our technology can be used in both small- and large-scale photovoltaic systems. To our knowledge, this is the only technology for automatic dust cleaning that doesn't require water or mechanical movement."

Mazumder, who is with Boston University, said the need for that technology is growing with the popularity of solar energy. Use of solar, or photovoltaic, panels increased by 50 percent from 2003 to 2008, and forecasts suggest a growth rate of at least 25 percent annually into the future. Fostering the growth, he said, is emphasis on alternative energy sources and society-wide concerns about sustainability (using resources today in ways that do not jeopardize the ability of future generations to meet their needs).

Large-scale solar installations already exist in the United States, Spain, Germany, the Middle East, Australia, and India. These installations usually are located in sun-drenched desert areas where dry weather and winds sweep dust into the air and deposit it onto the surface of solar panel. Just like grime on a household window, that dust reduces the amount of light that can enter the business part of the solar panel, decreasing the amount of electricity produced. Clean water tends to be scarce in these areas, making it expensive to clean the solar panels.

"A dust layer of one-seventh of an ounce per square yard decreases solar power conversion by 40 percent," Mazumder explains. "In Arizona, dust is deposited each month at about 4 times that amount. Deposition rates are even higher in the Middle East, Australia, and India."

Working with NASA, Mazumder and colleagues initially developed the self-cleaning solar panel technology for use in lunar and Mars missions. "Mars of course is a dusty and dry environment," Mazumder said, "and solar panels powering rovers and future manned and robotic missions must not succumb to dust deposition. But neither should the solar panels here on Earth."

The self-cleaning technology involves deposition of a transparent, electrically sensitive material deposited on glass or a transparent plastic sheet covering the panels. Sensors monitor dust levels on the surface of the panel and energize the material when dust concentration reaches a critical level. The electric charge sends a dust-repelling wave cascading over the surface of the material, lifting away the dust and transporting it off of the screen's edges.

Mazumder said that within two minutes, the process removes about 90 percent of the dust deposited on a solar panel and requires only a small amount of the electricity generated by the panel for cleaning operations.

The current market size for solar panels is about $24 billion, Mazumder said. "Less than 0.04 percent of global energy production is derived from solar panels, but if only four percent of the world's deserts were dedicated to solar power harvesting, our energy needs could be completely met worldwide. This self-cleaning technology can play an important role."

(Photo: US Air Force)

American Chemical Society

PAVING SLABS THAT CLEAN THE AIR

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The concentrations of toxic nitrogen oxide that are present in German cities regularly exceed the maximum permitted levels. That’s now about to change, as innovative paving slabs that will help protect the environment are being introduced. Coated in titanium dioxide nanoparticles, they reduce the amount of nitrogen oxide in the air.

In Germany, ambient air quality is not always as good as it might be – data from the federal environment ministry makes this all too clear. In 2009, the amounts of toxic nitrogen oxide in the atmosphere exceeded the maximum permitted levels at no fewer than 55 percent of air monitoring stations in urban areas. The ministry reports that road traffic is one of the primary sources of these emissions. In light of this fact, the Baroque city of Fulda is currently embarking on new ways to combat air pollution. Special paving slabs that will clean the air are to be laid the length of Petersberger Straße, where recorded pollution levels topped the annual mean limit of 40 micrograms per cubic meter (μg/m3) last year. These paving slabs are coated with titanium dioxide (TiO2), which converts harmful substances such as nitrogen oxides into nitrates. Titanium dioxide is a photocatalyst; it uses sunlight to accelerate a naturally occurring chemical reaction, the speed of which changes with exposure to light. The “Air Clean” nitrogen oxide-reducing paving slabs were developed by F. C. Nüdling Betonelemente. Proof of their effectiveness has subsequently been provided by the Fraunhofer Institute for Molecular Biology and Applied Ecology IME in Schmallenberg, where researchers also determined the risk to the environment posed by the resulting nitrates. Their work was funded by the German Environment Foundation.

Dr. Monika Herrchen, a scientist at the IME, says: “Experiments in Italian cities had already shown that photocatalytic paving slabs can improve the air quality. We wanted to see if they would also be effective here in Germany, where we have lower levels of light intensity and fewer hours of sunshine. Of course, the more intense the sunshine, the quicker the degradation of harmful substances, so our aim was to identify the formula with the highest photocatalytic efficiency rating.”

To begin with, concrete manufacturer F.C. Nüdling produced a range of sample slabs incorporating different surfaces, colors, types of cement and TiO2 contents. Since the nitrogen oxide degradation rates achieved using standard commercial photocatalytic cement (i.e. cement that reacts to solar radiation) proved unsatisfactory, the company ultimately had to develop its own, more effective formula. “We were able to verify the effectiveness of the optimized slabs in a variety of tests,” confirms Herrchen. During an extended time field test, the scientist and her team recorded nitrogen oxide degradation rates of 20 to 30 percent in specially-created street canyons. The measurements were taken at a height of three meters above the photocatalytic slabs, in variable wind and light conditions. When the wind was still, the experts recorded degradation rates as high as 70 percent for both nitrogen monoxide (NO) and nitrogen dioxide (NO2). Measurements likewise taken at a height of three meters above the Gothaer Platz in Erfurt, which is already paved with Air Clean paving slabs, revealed an average degradation rate of 20 percent for NO2 and 38 percent for NO.

Herrchen points out an additional benefit of these paving slabs: “They also remain stable over the long term. Measurements recorded from 14 to 23 months after they were laid revealed no change from the initial degradation capability.” Furthermore, the nitrate that is generated during the conversion process poses absolutely no risk to the environment. It runs off into the drainage system, then into a wastewater treatment plant, before finally ending up on a farmer’s field or in the groundwater. The maximum possible nitrate concentration traceable back to photocatalytic reactions is around five milligrams per liter (mg/l), while the maximum permitted concentration of nitrate in groundwater is 50 mg/l. Herrchen sums up: “All in all, it’s possible to say that Air Clean significantly improves the air quality within a short space of time, and thus helps protect the environment.”

(Photo: © Fraunhofer IME)

Fraunhofer

FOSSIL REVEALS 48-MILLION-YEAR HISTORY OF ZOMBIE ANTS

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A 48-million-year-old fossilised leaf has revealed the oldest known evidence of a macabre part of nature – parasites taking control of their hosts to turn them into zombies.

The discovery has been made by a research team led by Dr David P Hughes, from the University of Exeter, who studies parasites that can take over the minds of their hosts.

All manner of animals are susceptible to the often deadly body invasion, but scientists have been trying to track down when and where such parasites evolved.

Dr Hughes, from the University's School of Biosciences, said: "There are various techniques, called a molecular clock approach, which we can use to estimate where and when they developed and fossils are an important source of information to calibrate such clocks.

"This leaf shows clear signs of one well documented form of zombie-parasite, a fungus which infects ants and then manipulates their behaviour."

The fungus, called Ophiocordyceps unilateralis, causes ants to leave their colonies and head for a leaf which provides the ideal conditions for the host to reproduce.

When it gets there the ant goes into a 'death grip'– biting down very hard on the major vein of a leaf. This means that when the ant dies, its body stays put so the fungus has time to grow and release its spores to infect other ants.

The death grip bite leaves a very distinct scar on the leaves. This prompted Dr Hughes, together with research partners Conrad Labandeira from the Smithsonian Institution in the USA and Torsten Wappler, from the Steinmann Institute in Germany, to search for potential evidence of the fungus at work by studying the fossilised remains of leaves.

After studying leaf fossils from the Messel Pit, a site on the eastern side of the Rhine Rift Valley in Hesse, Germany, they found clear evidence of the death grip bite in a 48-million-year-old leaf specimen.

Dr Hughes said: "The evidence we found mirrors very closely the type of leaf scars that we find today, showing that the parasite has been working in the same way for a very long time.

"This is, as far as we know, the oldest evidence of parasites manipulating the behaviour of their hosts and it shows this parasitic association with ants is relatively ancient and not a recent development.

"Hopefully we can now find more fossilised evidence of parasitic manipulation. This will help us shed further light on the origins of this association so we can get a better idea of how it has evolved and spread."

(Photo: David P. Hughes)

University of Exeter

ARTIFICIAL ENZYME REMOVES NATURAL POISON

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For the first time ever, a completely man-made chemical enzyme has been successfully used to neutralise a toxin found naturally in fruits and vegetables.

Chemzymes are designed molecules emulating the targeting and efficiency of naturally occurring enzymes and the recently graduated Dr. Bjerre is pleased about her results.

"Showing that these molecules are capable of decomposing toxins required vast amounts of work and time. But it's been worth every minute because it proves the general point that it's possible to design artificial enzymes for this class of task", explains Bjerre.

Most people know enzymes as an ingredient in detergents. In our bodies enzymes are in charge of decomposing everything we eat, so that our bodies can absorb the nutrients. But they also decompose ingested toxins, ensuring that our bodies survive the encounter.

In several important aspects artificial enzymes function in the same way as naturally occurring ones. But where natural enzymes are big and complex, the artificial ones have been pared down to the basics.

One consequence of this simplicity is that designing chemzymes for targeted tasks ought to be easier. With fewer parts, there's less to go wrong when changing the structure of chemzymes. And for enzymes as well as for their artificial counterparts even small changes in structure will have massive consequences for functionality.

In this, enzymes are very much like hand-tools, where scissors and flat nosed pliers, though almost identical, have very different duties.

Even though naturally occurring enzymes are several orders of magnitude smaller than flat-nosed pliers, they are still unrivalled tools. Some of the fastest chemical reactions blast off when enzymes are added to the broth.

Several known enzymes in the body catalyze more than one million reactions per second when they decompose compounds. There's just one drawback to enzymes. They are extremely fragile.

If an enzyme in our body was to be warmed above sixtyfive degrees centigrade or subjected to organic solvents, they would immediately denature. They would unravel and stop functioning.

So far no one has succeeded in designing chemzymes that are anywhere near as fast as their naturally occurring cousins. But they are far more resilient.

Manmade enzymes take on heat and solvents without batting a molecular eyelid. One of the consequences of this is that chemzymes can be mass-produced using industrial chemical processes. This is a huge advantage when you need a lot of product in a hurry.

Producing natural enzymes in industrial settings is considerably more time-consuming because they have to be grown. Rather like one grows apples or grain.

So the robust and designable compounds may turn out to be just what's needed for a wide variety of jobs. Not least in the pharmaceutical industries, where the need is massive for chemical compounds which can solve problems that no amount of designing could ever tweak the natural ones to work on, which are unaffected by industrial processes, and to top it of, cheap to produce.

(Photo: U. Copenhagen)

University of Copenhagen

WHY FISH DON'T FREEZE IN THE ARCTIC OCEAN

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Together with cooperation partners from the U.S., the researchers surrounding Prof. Dr. Martina Havenith (Physical Chemistry II of the RUB) describe their discovery in a so-termed Rapid Communication in the prestigious American chemistry journal, the Journal of the American Chemical Society (JACS).

Temperatures of minus 1.8 ° C should really be enough to freeze any fish: the freezing point of fish blood is about minus 0.9 ° C. How Antarctic fish are able to keep moving at these temperatures has interested researchers for a long time. As long as 50 years ago, special frost protection proteins were found in the blood of these fish. These so-called anti-freeze proteins work better than any household antifreeze. How they work, however, was still unclear. The Bochum researchers used a special technique, terahertz spectroscopy, to unravel the underlying mechanism. With the aid of terahertz radiation, the collective motion of water molecules and proteins can be recorded. Thus, the working group has already been able to show that water molecules, which usually perform a permanent dance in liquid water, and constantly enter new bonds, dance a more ordered dance in the presence of proteins – "the disco dance becomes a minuet" says Prof. Havenith.

The subject of the current investigations was the anti-freeze glycoproteins of the Antarctic toothfish Dissostichus mawsoni, which one of the American partners, Arthur L. Devries, had fished himself on an Antarctic expedition. "We could see that the protein has an especially long-range effect on the water molecules around it. We speak of an extended dynamical hydration shell", says co-author Konrad Meister. "This effect, which prevents ice crystallization, is even more pronounced at low temperatures than at room temperature", adds Prof. Havenith. Nevertheless, to freeze the water, lower temperatures would be necessary. Complexation of the AFP by borate strongly reduces the antifreeze activity. In this case, the researchers also found no change in the terahertz dance. The researchers' results provide evidence for a new model of how AFGPs prevent water from freezing: Antifreeze activity is not achieved by a single molecular binding between the protein and the water, but instead AFP perturbs the aqueous solvent over long distances. The investigation demonstrated for the first time a direct link between the function of a protein and its signature in the terahertz range. The studies were funded by the Volkswagen Foundation.

(Photo: Konrad Meister)

RUB

ELECTRICITY COLLECTED FROM THE AIR COULD BECOME THE NEWEST ALTERNATIVE ENERGY SOURCE

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Imagine devices that capture electricity from the air ― much like solar cells capture sunlight ― and using them to light a house or recharge an electric car. Imagine using similar panels on the rooftops of buildings to prevent lightning before it forms. Strange as it may sound, scientists already are in the early stages of developing such devices, according to a report presented at the 240th National Meeting of the American Chemical Society (ACS).

"Our research could pave the way for turning electricity from the atmosphere into an alternative energy source for the future," said study leader Fernando Galembeck, Ph.D. His research may help explain a 200-year-old scientific riddle about how electricity is produced and discharged in the atmosphere. "Just as solar energy could free some households from paying electric bills, this promising new energy source could have a similar effect," he maintained.

"If we know how electricity builds up and spreads in the atmosphere, we can also prevent death and damage caused by lightning strikes," Galembeck said, noting that lightning causes thousands of deaths and injuries worldwide and millions of dollars in property damage.

The notion of harnessing the power of electricity formed naturally has tantalized scientists for centuries. They noticed that sparks of static electricity formed as steam escaped from boilers. Workers who touched the steam even got painful electrical shocks. Famed inventor Nikola Tesla, for example, was among those who dreamed of capturing and using electricity from the air. It's the electricity formed, for instance, when water vapor collects on microscopic particles of dust and other material in the air. But until now, scientists lacked adequate knowledge about the processes involved in formation and release of electricity from water in the atmosphere, Galembeck said. He is with the University of Campinas in Campinas, SP, Brazil.

Scientists once believed that water droplets in the atmosphere were electrically neutral, and remained so even after coming into contact with the electrical charges on dust particles and droplets of other liquids. But new evidence suggested that water in the atmosphere really does pick up an electrical charge.

Galembeck and colleagues confirmed that idea, using laboratory experiments that simulated water's contact with dust particles in the air. They used tiny particles of silica and aluminum phosphate, both common airborne substances, showing that silica became more negatively charged in the presence of high humidity and aluminum phosphate became more positively charged. High humidity means high levels of water vapor in the air ― the vapor that condenses and becomes visible as "fog" on windows of air-conditioned cars and buildings on steamy summer days.

"This was clear evidence that water in the atmosphere can accumulate electrical charges and transfer them to other materials it comes into contact with," Galembeck explained. "We are calling this 'hygroelectricity,' meaning 'humidity electricity'."

In the future, he added, it may be possible to develop collectors, similar to the solar cells that collect the sunlight to produce electricity, to capture hygroelectricity and route it to homes and businesses. Just as solar cells work best in sunny areas of the world, hygroelectrical panels would work more efficiently in areas with high humidity, such as the northeastern and southeastern United States and the humid tropics.

Galembeck said that a similar approach might help prevent lightning from forming and striking. He envisioned placing hygroelectrical panels on top of buildings in regions that experience frequent thunderstorms. The panels would drain electricity out of the air, and prevent the building of electrical charge that is released in lightning. His research group already is testing metals to identify those with the greatest potential for use in capturing atmospheric electricity and preventing lightning strikes.

"These are fascinating ideas that new studies by ourselves and by other scientific teams suggest are now possible," Galembeck said. "We certainly have a long way to go. But the benefits in the long range of harnessing hygroelectricity could be substantial."

(Photo: Martin Fischer)

American Chemical Society

PURPLE LIGHT MEANS GO, ULTRAVIOLET LIGHT MEANS STOP

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A new membrane developed at the University of Rochester's Laboratory for Laser Energetics blocks gas from flowing through it when one color of light is shined on its surface, and permits gas to flow through when another color of light is used. It is the first time that scientists have developed a membrane that can be controlled in this way by light.

Eric Glowacki, a graduate student at the University's Laboratory for Laser Energetics, and Kenneth Marshall, his advisor, invented the membrane. Marshall will present their findings at the annual conference of the International Society for Optics and Photonics (SPIE) in San Diego on Aug. 1.

The membrane is a piece of hard plastic riddled with tiny holes that are filled with liquid crystals and a dye. When purple light illuminates the surface of the membrane, the dye molecules straighten out and the liquid crystals fall into line, which allows gas to easily flow through the holes. But when ultraviolet light illuminates the surface, the dye molecules bend into a banana shape and the liquid crystals scatter into random orientations, clogging the tunnel and blocking gas from penetrating.

Controlling a membrane's permeability with light is preferable to controlling it with heat or electricity – two readily used alternative methods – for several reasons, Glowacki said. For starters, light can operate remotely. Instead of attaching electrical lines to the membrane, a lamp or a laser can be directed at the membrane from a distance. This could allow engineers to make much smaller, simpler setups.

Another advantage is that the color of the light illuminating the membrane can be changed precisely and almost instantaneously. Other methods, like heating and cooling, take a relatively long time and repeated heating and cooling can damage the membrane.

Also, light does not have the potential to ignite a gas, which could be a crucial benefit when working with hydrocarbons or other flammable gases. Lastly, the amount of light energy needed to switch the membrane on and off is miniscule.

Creating the membrane is a multi-step process. First, a circular hard plastic chip is bombarded with a beam of neutrons to make the tiny, evenly spaced holes that are about one-hundredth of a millimeter in diameter. The chip is then dipped in a solution of liquid crystals and dye, and the mixture fills the holes through capillary action. The final product is spun in a centrifuge to remove the excess liquid crystals from the surface.

The membrane could be useful in controlled drug delivery and industrial processing tasks that require the ability to turn the flow of gas on and off as well as in research applications.

(Photo: University of Rochester)

University of Rochester

FOR THE FIRST TIME EVER, SCIENTISTS WATCH AN ATOM’S ELECTRONS MOVING IN REAL TIME

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An international team of scientists led by groups from the Max Planck Institute of Quantum Optics (MPQ) in Garching, Germany, and from the U.S. Department of Energy’s Lawrence Berkeley National Laboratory and the University of California at Berkeley has used ultrashort flashes of laser light to directly observe the movement of an atom’s outer electrons for the first time.

Through a process called attosecond absorption spectroscopy, researchers were able to time the oscillations between simultaneously produced quantum states of valence electrons with great precision. These oscillations drive electron motion.

“With a simple system of krypton atoms, we demonstrated, for the first time, that we can measure transient absorption dynamics with attosecond pulses,” says Stephen Leone of Berkeley Lab’s Chemical Sciences Division, who is also a professor of chemistry and physics at UC Berkeley. “This revealed details of a type of electronic motion – coherent superposition – that can control properties in many systems.”

Leone cites recent work by the Graham Fleming group at Berkeley on the crucial role of coherent dynamics in photosynthesis as an example of its importance, noting that “the method developed by our team for exploring coherent dynamics has never before been available to researchers. It’s truly general and can be applied to attosecond electronic dynamics problems in the physics and chemistry of liquids, solids, biological systems, everything.”

The team’s demonstration of attosecond absorption spectroscopy began by first ionizing krypton atoms, removing one or more outer valence electrons with pulses of near-infrared laser light that were typically measured on timescales of a few femtoseconds (a femtosecond is 10^-15 second, a quadrillionth of a second). Then, with far shorter pulses of extreme ultraviolet light on the 100-attosecond timescale (an attosecond is 10^-18 second, a quintillionth of a second), they were able to precisely measure the effects on the valence electron orbitals.

The results of the pioneering measurements performed at MPQ by the Leone and Krausz groups and their colleagues are reported in the August 5 issue of the journal Nature.

Valence electrons control how atoms bond with other atoms to form molecules or crystal structures, and how these bonds break and reform during chemical reactions. Changes in molecular structures occur on the scale of many femtoseconds and have often been observed with femtosecond spectroscopy, in which both Leone and Krausz are pioneers.

Femtosecond-scale pulses were fired to ionize krypton atoms (wide beam). Separately created attosecond-scale pulses (narrow beam) were absorbed by the krypton atoms. Spectroscopy mapped the precise timing of the oscillation between quantum states thus created.

Zhi-Heng Loh of Leone’s group at Berkeley Lab and UC Berkeley worked with Eleftherios Goulielmakis of Krausz’s group to perform the experiments at MPQ. By firing a femtosecond pulse of infrared laser light through a chamber filled with krypton gas, atoms in the path of the beam were ionized by the loss of one to three valence electrons from their outermost shells.

The experimenters separately generated extreme-ultraviolet attosecond pulses (using the technique called “high harmonic generation”) and sent the beam of attosecond probe pulses through the krypton gas on the same path as the near-infrared pump pulses.

By varying the time delay between the pump pulse and the probe pulse, the researchers found that subsequent states of increasing ionization were being produced at regular intervals, which turned out to be approximately equal to the time for a half cycle of the pump pulse. (The pulse is only a few cycles long; the time from crest to crest is a full cycle, and from crest to trough is a half cycle.)

“The femtosecond pulse produces a strong electromagnetic field, and ionization takes place with every half cycle of the pulse,” Leone says. “Therefore little bursts of ions are coming out every half cycle.”

Although expected from theory, these isolated bursts were not resolved in the experiment. The attosecond pulses, however, could precisely measure the production of the ionization, because ionization – the removal of one or more electrons – leaves gaps or “holes,” unfilled orbitals that the ultrashort pulses can probe.

The attosecond pulses do so by exciting electrons from lower energy orbitals to fill the gap in krypton’s outermost orbital – a direct result of the absorption of the transient attosecond pulses by the atoms. After the “long” femtosecond pump pulse liberates an electron from the outermost orbital (designated 4p), the short probe pulse boosts an electron from an inner orbital (designated 3d), leaving behind a hole in that orbital while sensing the dynamics of the outermost orbital.

In singly charged krypton ions, two electronic states are formed. A wave-packet of electronic motion is observed between these two states, indicating that the ionization process forms the two states in what’s known as quantum coherence.

In krypton’s single ionization state, quantum oscillations in the valence shell cycled in a little over six femtoseconds. Attosecond pulses probed the details (black dots), filling the gap in the outer orbital with an electron from an inner orbital, and sensing the changing degrees of coherence between the two quantum states thus formed (below).

Says Leone, “There is a continual ‘orbital flopping’ between the two states, which interfere with each other. A high degree of interference is called coherence.” Thus when the attosecond probe pulse clocks the outer valence orbitals, it is really clocking the high degree of coherence in the orbital motion caused by ionization.

“When the bursts of ions are made quickly enough, with just a few cycles of the ionization pulse, we observe a high degree of coherence,” Leone says. “Theoretically, however, with longer ionization pulses the production of the ions gets out of phase with the period of the electron wave-packet motion, as our work showed.”

So after just a few cycles of the pump pulse, the coherence is washed out. Thus, says Leone, “Without very short, attosecond-scale probe pulses, we could not have measured the degree of coherence that resulted from ionization.”

The physical demonstration of attosecond transient absorption by the combined efforts of the Leone and Krausz groups and their colleagues will, in Leone’s words, “allow us to unravel processes within and among atoms, molecules, and crystals on the electronic timescale” – processes that previously could only be hinted at with studies on the comparatively languorous femtosecond timescale.

(Photo: LBNL)

Lawrence Berkeley National Laboratory

SEARCH FOR THE LOST AMPHIBIANS

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Teams of scientists around the world have launched an unprecedented search in the hope of rediscovering 100 species of "lost" amphibians – animals considered potentially extinct but that may be holding on in a few remote places – Conservation International and the IUCN Amphibian Specialist Group announced.

This search, which is taking place in 14 countries on five continents, is the first ever coordinated effort to find such a large number of "lost" creatures and comes as global amphibian populations are suffering a shocking decline – with more than 30 per cent of all species threatened with extinction.

Many of the amphibians that the teams of scientists are looking for have not been seen in several decades, and establishing whether populations have survived or not is vital for scientists looking to understand the recent amphibian extinction crisis. Amphibians also provide many important services to humans such as controlling insects that spread disease and damage crops and helping to maintain healthy freshwater systems – the chemicals in amphibian skins have also been important in helping to create new drugs with the potential to save lives, including a painkiller 200 times more potent than morphine.

"Amphibians are particularly sensitive to changes in the environment, so they are often an indicator of damage that is being done to ecosystems," explains Conservation International's Dr Robin Moore, who has organized the search for IUCN's Amphibian Specialist Group.

"But this role as the global 'canary in a coal-mine' means that the rapid and profound change to the global environment that has taken place over the last fifty years or so – in particular climate change and habitat loss – has had a devastating impact on these incredible creatures. We've arranged this search for 'lost' species that we believe may have managed to hang on so that we can get some definite answers - and hopefully learn about what has allowed some tiny populations of certain species to survive when the rest of their species has been lost."

The problems amphibians face from habitat loss have been massively exacerbated by a pathogenic fungus, which causes chytridiomycosis, a disease that has wiped-out entire populations of amphibians and in some cases whole species.

Dr Moore and his team have drawn up a list of the "top 10" species of the 100 being searched for that he believes would be particularly exciting to find. He said: "While it's very challenging to rate the importance of one species against another we have created this top 10 list because we feel that these particular animals have a particular scientific or aesthetic value."

Conservation International

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