Thursday, October 22, 2009

CLIMATE MODELS DON'T TELL THE FULL STORY

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Climate models that predict heavy rainfall don’t give the whole picture, according to the results of a study by NWO scientist Martin Ziegler. He examined climate changes that have taken place over the past 800,000 years, and discovered that the melting icebergs in the North Atlantic and changes in the El Niño Southern Oscillation have a great influence on the intensity of monsoon rains.

Ziegler analysed sedimentary deposits from around the world in order to work out which factors affect the strength of monsoons. The sedimentary deposits give a picture of the weather patterns of the last 800,000 years. Many climate models are based on gradual changes, for example the concentration of greenhouse gases in the earth’s atmosphere, or changes in the solar radiation that enters the atmosphere. According to Ziegler, this means that important factors may be overlooked.

Ziegler demonstrated that it’s not just the solar radiation that has a great influence, but also the melting of great expanses of ice as a consequence of the way that the earth wobbles on its axis. Changes in the El Niño Southern Oscillation, which is essentially a periodic temperature fluctuation in the water of the eastern Pacific, were shown to have a great influence on the intensity of the monsoon. Many current climate models take into account the long-term effects of the periodic fluctuations in the position of the earth's axis, but look only at the changes in the distribution of solar radiation that reaches earth over a one- year period.

The monsoon rains affect large areas of Asia and Africa each year. During some periods there is much more or less rain than usual, which can often lead to floods. The strength of the monsoon can therefore have serious consequences.

Martin Ziegler carried out his research within Lucas Lourens' Vidi project. In 2002 he received a Vidi as part of the NWO’s Innovational Research Incentives Scheme. Lourens hopes that his research will allow him to shed new light on slow climate changes, both now and in the future.

The Netherlands Organization for Scientific Research (NWO)

MU RESEARCHERS CREATE SMALLER AND MORE EFFICIENT NUCLEAR BATTERY

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Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are much larger and heavier than the devices themselves. University of Missouri researchers are developing a nuclear energy source that is smaller, lighter and more efficient.

“To provide enough power, we need certain methods with high energy density,” said Jae Kwon, assistant professor of electrical and computer engineering at MU. “The radioisotope battery can provide power density that is six orders of magnitude higher than chemical batteries.”

Kwon and his research team have been working on building a small nuclear battery, currently the size and thickness of a penny, intended to power various micro/nanoelectromechanical systems (M/NEMS). Although nuclear batteries can pose concerns, Kwon said they are safe.

“People hear the word ‘nuclear’ and think of something very dangerous,” he said. “However, nuclear power sources have already been safely powering a variety of devices, such as pace-makers, space satellites and underwater systems.”

His innovation is not only in the battery’s size, but also in its semiconductor. Kwon’s battery uses a liquid semiconductor rather than a solid semiconductor.

“The critical part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure of the solid semiconductor,” Kwon said. “By using a liquid semiconductor, we believe we can minimize that problem.”

Kwon has been collaborating with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, and is working to build and test the battery at the facility. In the future, they hope to increase the battery’s power, shrink its size and try with various other materials. Kwon said that the battery could be thinner than the thickness of human hair. They’ve also applied for a provisional patent.

University of Missouri

CHANCE TO USURP REPRODUCTIVE POWER OF ROYAL THRONE KEEPS WORKER TERMITES HOME

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A new study by researchers at the University of Maryland suggests termite offspring stay in their birth colony to help their queen and king parents rather than leave to try and start their own family because their chance of inheriting the 'reproductive throne' is higher than their chance of successfully dispersing, finding a mate, and surviving to produce fertile offspring on their own.

In research published in the Proceedings of the National Academy of Sciences Early Edition (October 5, 2009), Professor Barbara L. Thorne and colleagues reveal how unrelated termites originating from two different families or colonies join forces after the death of their kings and queens, and then cooperate in a larger, stronger group in which new "reproductives" can emerge from the worker ranks of either or both original colonies, thus enabling both lineages to thrive.

"When young dampwood termite colonies nest in the same piece of wood, their interactions result in assassination and cannibalism of one or both sets of queens and kings followed by fusion of the two families into a single colony," said Thorne.

These findings help unravel an evolutionary mystery that Charles Darwin himself recognized as a special problem to reconcile with fundamental concepts of natural selection. The majority of individuals in a termite (or ant, bee, or wasp) colony are "workers" who stay to help out in their parents' colony their entire lives, but never reproduce. Why would natural selection ("survival of the fittest") favor traits that reduce reproductive success? This research shows that unrelated families both benefit following colony encounters and that competition among families living within limited food and nesting resources played a prominent role in the evolution of the complex social structure in termites.

For this study, Thorne and her colleagues Philip Johns and Ken Howard, now at Bard College, and Nancy Breisch and Anahi Rivera at the University of Maryland, staged meetings between unrelated dampwood termite colonies (from the Termopsidae family) that mimicked natural meetings that occur under wood bark, and analyzed genetic markers. These termites are members of the genus Zootermopsis, and share social, developmental, and habitat characteristics with ancient ancestors. They thus serve as a model system to draw inferences regarding how highly social behavior evolved in these insects 140 million years ago.

Termite colonies begin as a nuclear family: the queen, the king, and their offspring (workers and soldiers). Although most termite workers never reproduce, if either or both of the original parents die, one or more of their offspring can become a 'replacement reproductive' to carry on (usually incestuous) reproduction and growth of the colony. When young dampwood termite colonies nest in the same piece of wood, the neighbors meet and the two families merge into a single colony after a violent process during which one or both sets of queens and kings may be killed and eaten. After the carnage, worker offspring may usurp the throne and the reproductive power and resources that go with it.

Despite the original colonies being unrelated, individuals within the merged colony cooperate. This cooperation is best explained by the key finding of this paper, revealed through analysis of genetic markers: offspring in both original colonies have opportunities to develop into new (replacement) reproductives within the larger, merged colony, and termites from the two families may even interbreed. Thus both lineages (i.e. both original, unrelated families or young colonies) can 'win' and propagate in this dynamic.

(Photo: U. Maryland)

University of Maryland

LEARNING TO SPEAK: TODDLERS DEVELOP INDIVIDUALIZED RULES FOR GRAMMAR

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Using advanced computer modeling and statistical analysis, a University of Texas at Austin linguistics professor has found that toddlers develop their own individual structures for using language that are very different from what we traditionally think of as grammar.

"Grammars have different forms in development," says Colin Bannard, assistant professor in the Department of Linguistics. "We shouldn't assume a child's grammar is anything like our traditional notion of what grammar is."

In a study released in the journal Proceedings of the National Academy of Sciences, Bannard and Elena Lieven and Michael Tomasello, two colleagues working at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, developed a computer program to analyze 60 hours worth of conversations that two English-speaking toddlers — Brian and Annie — had with their parents after turning two and again after turning three.

The computer model did not assume the children knew any of the basic rules of language, such as the use of nouns and verbs. Instead, it used the toddlers' early conversations after each birthday to predict the structure of their subsequent conversations.

Rather than adhering to the kinds of rules for English linguists have identified, the toddlers developed their own basic formulas for speaking with slots into which they could put particular kinds of words. At age two, those formulas — which were different for each child — were found to predict the children's subsequent speech better than a more traditional grammar.

Many researchers have long believed that even young children's earliest language derives from an understanding of an abstract grammar that includes categories like nouns and verbs and a set of rules for combining them to produce sentences.

"How exactly a child learned these was considered something of a mystery and so it was declared by some that they must be innate," Bannard says. "However there is increasing evidence that children's path to grammar is a gradual and piecemeal process."

The findings also show that, between the ages of two and three, children learn to better understand and apply the adult rules of grammar, particularly by using verbs more flexibly.

This is the first major study of children's language development that uses advanced computer modeling to analyze, understand and predict children's utterances based on daily recordings of their language use.

"One thing that is very important about this work is Dr. Bannard's sophisticated use of computational and statistical techniques to analyze child language data," says Richard P. Meier, chair of the Linguistics Department.

Bannard hopes to use such methods more extensively.

"Here we have a technique for modeling grammar I'd like to apply to more children, to look at them more continuously from age two to age three, to apply rigorous statistics to learn what a child knows," Bannard says.

University of Texas

DO DUST PARTICLES CURB CLIMATE CHANGE?

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A knowledge gap exists in the area of climate research: for decades, scientists have been asking themselves whether, and to what extent man-made aerosols, that is, dust particles suspended in the atmosphere, enlarge the cloud cover and thus curb climate warming. Research has made little or no progress on this issue. Two scientists from the Max Planck Institute for Meteorology in Hamburg (MPI-M) and the American National Oceanic and Atmospheric Administration (NOAA) report in the journal Nature that the interaction between aerosols, clouds and precipitation is strongly dependent on factors that have not been adequately researched up to now. They urge the adoption of a research concept that will close this gap in the knowledge.

Greenhouse gases that heat up the earth’s atmosphere have their adversaries: dust particles suspended in the atmosphere which are known as aerosols. They arise naturally, for example when wind blows up desert dust, and through human activities. A large proportion of the man-made aerosols arise from sulfur dioxides that are generated, in turn, by the combustion of fossil fuels.

The aerosols are viewed as climate coolers, which compensate in part for the heating up of the earth by greenhouse gases. Climate researchers imagine the workings of this cooling mechanism in very simple terms: when aerosols penetrate clouds, they attract water molecules and therefore act as condensation seeds for drops of water. The more aerosol particles suspended in the cloud, the more drops of water are formed. When man-made dust particles join the natural ones, the number of drops increases. As a result, the average size of the drops decreases. Because smaller drops do not fall to the ground, the aerosols prevent the cloud from raining out and extend its lifetime. Consequently, the cloud cover over the earth’s surface increases. Because clouds reflect the solar radiation and throw it back into space, less heat collects in the atmosphere than when the sky is clear. Climate researchers refer to this mechanism as the "cloud lifetime effect".

To date, however, it has not been possible to quantify the influence of the cloud lifetime effect on climate. The estimates vary hugely and range from no influence whatsoever to a cooling effect that is sufficient to more than compensate for the heating effect of carbon dioxide.

According to Bjorn Stevens from the MPI-M and Graham Feingold from the Earth System Research Laboratory at NOAA in Washington D.C the enormous uncertainty surrounding this phenomenon is indicative of the fact that the explanation of the cooling mechanism generated by aerosols is oversimplified. The two cloud researchers have analyzed the specialist literature published on this topic since the 1970s. In their survey of the literature they encountered observations that disagree with the cloud lifetime effect: for example, a field study carried out a few years ago found that clouds in the Trade Wind region rain out more quickly rather than more slowly in the presence of virtually opaque aerosols.

On the completion of their analysis of the literature, Stevens and Feingold came to the following conclusion: "Clouds react to aerosols in a very complex way and the reaction is strongly dependent on the type and state of the cloud," says Stevens. Therefore the aerosol problem is a cloud problem. "We climate researchers must focus more on cloud systems and understand them better," he stresses.

As the researchers write, processes in the clouds that counteract or even negate the influence of the aerosol particles have not been taken into account up to now. One example: when a cumulus cloud comes into contact with aerosols, it does not rain out. However, this has certain consequences: the fluid rises and evaporates above the cloud. The air that lies above the cloud cools down and becomes susceptible to the upward extension of the cumulus cloud. Higher cumulus clouds rain out more easily than lower ones. This is what causes precipitation. Therefore, in such situations the aerosol does not prevent the cloud from raining out.

Stevens and Feingold believe that due to such buffer mechanisms the cooling effect of the aerosols is likely to be minimal. They admit, however, that the cloud lifetime effect is not unsuitable per se as a way of explaining the processes triggered by aerosols in the clouds. "All cloud types and states cannot, however, be lumped together," says Stevens. He calls for rethinking aerosol research and makes a comparison with cancer research: "People used to think that cancer was based on a single mechanism. Today, it is known that each type of cancer must be researched individually," says the scientist.

According to Stevens and Feingold, research must first identify the cloud systems on which aerosols have the greatest influence. They suggest starting with particularly common types of cloud, for example flat cumulus clouds over the oceans (Trade Wind cumuli), which cover 40 percent of the global seas.

A research project to be undertaken jointly by the Max Planck Institute for Meteorology and the Caribbean Institute for Meteorology and Hydrology in Miami will make a start on this. The two-year empirical field study will commence on the Caribbean island of Barbados, which is located in the Trade Wind region, in 2010. The researchers will install remote sensing instruments on the island’s windward side that will focus on the clouds coming from the open ocean. The land measurements will be complemented by measurements taken in the clouds themselves by HALO, the German research aircraft. The data from this measurement campaign should help the scientists to reach a better understanding of the relationships between cloud cover, precipitation, local meteorological conditions and aerosols.

(Photo: Max Planck Institute for Meteorology / Stevens)

Max Planck Institute

COCAINE VACCINE SHOWS PROMISE FOR TREATING ADDICTION

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Immunization with an experimental anti-cocaine vaccine resulted in a substantial reduction in cocaine use in 38 percent of vaccinated patients in a clinical trial supported by the National Institute on Drug Abuse (NIDA), a component of the National Institutes of Health. The study, published in the October issue of the Archives of General Psychiatry, is the first successful, placebo-controlled demonstration of a vaccine against an illicit drug of abuse.

"The results of this study represent a promising step toward an effective medical treatment for cocaine addiction," said NIDA Director Dr. Nora Volkow." Provided that larger follow-up studies confirm its safety and efficacy, this vaccine would offer a valuable new approach to treating cocaine addiction, for which no FDA-approved medication is currently available."

Like vaccines against infectious diseases such as measles and influenza, the anti-cocaine vaccine stimulates the immune system to produce antibodies. Unlike antibodies against infectious diseases, which destroy or deactivate the disease-causing agents, anti-cocaine antibodies attach themselves to cocaine molecules in the blood, preventing them from passing through the blood-brain barrier. By preventing the drug’s entry into the brain, the vaccine inhibits or blocks the cocaine-induced euphoria.

This study included 115 patients from a methadone maintenance program who were randomly assigned to receive the anti-cocaine vaccine or a placebo (inactive) vaccine. Participants were recruited from a methadone maintenance program because their retention rates are substantially better than programs focused primarily on treatment for cocaine abuse. Participants in both groups received five vaccinations over a 12-week period and were followed for an additional 12 weeks. All participants also took part in weekly relapse-prevention therapy sessions with a trained substance abuse counselor, had their blood tested for antibodies to cocaine, and had their urine tested three times a week for the presence of opioids and cocaine.

Participants differed in the levels of antibodies generated in response to vaccination. Thirty-eight percent attained blood levels of anti-cocaine antibodies thought to be sufficient to block cocaine's euphoric effects. During weeks 9 to 16 (when antibody levels peaked), these participants had significantly more cocaine-free urines than those who received the placebo or those with active vaccine but low levels of anti-cocaine antibodies. Participants with the highest antibody levels had the greatest reductions in cocaine use. No serious adverse effects were associated with vaccine treatment.

"Fifty-three percent of participants in the high-antibody group were abstinent from cocaine more than half the time during weeks 8 to 20, compared with only 23 percent of participants with lower levels of antibodies," said Thomas Kosten, M.D., of Baylor College of Medicine in Houston, the study's principal investigator.

"In this study immunization did not achieve complete abstinence from cocaine use," added Dr. Kosten. "Previous research has shown, however, that a reduction in use is associated with a significant improvement in cocaine abusers’ social functioning and thus is therapeutically meaningful."

National Institutes of Health

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