Tuesday, April 13, 2010


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Physicists, including nine from UC Davis, working at the U.S. Department of Energy's Brookhaven National Laboratory recently created some strange matter not seen since just after the Big Bang -- an "antihypertriton" composed of antimatter and "strange" quarks. A paper describing the work was published online this month in the journal Science.

If researchers can create and study enough of these particles, they can start to address deep problems in physics, such as why the universe is made of matter at all, said Manuel Calderon de la Barca Sanchez, associate professor of physics at UC Davis and part of the project team.

A triton is the nucleus of the hydrogen isotope tritium: a proton and two neutrons. A neutron is made up of three quarks, two "down" and one "up." In a hypertriton, one of the neutrons is replaced by a particle called a lambda hyperon, with one "up," one "down" and one "strange" quark. A hypertriton was observed for a fleeting moment in a lab experiment about 50 years ago, Calderon said.

Calderon and his colleagues detected the antihypertriton when they used Brookhaven's Relativistic Heavy Ion Collider to slam gold atoms into each other at enormous speed. The energy released in these collisions creates new particles in a "quark-gluon plasma," similar to that which existed microseconds after the beginning of the universe.

The antihypertriton, as its name suggests, is a hypertriton in which the up, down and strange quarks are replaced with antimatter equivalents (anti-up, anti-down and anti-strange quarks).

The particle decayed so quickly that the Brookhaven experiment could only record its distinctive decay products. The researchers collected evidence of about 70 antihypertritons from 100 million collisions.

Being able to make these antinuclei opens up a new field of nuclear physics, Calderon said.

According to theory, equal amounts of matter and antimatter should have been created in the Big Bang. However, if that were the case, the two kinds of matter would have canceled each other out, leaving nothing at all. Instead, the Big Bang yielded an observable universe made mostly of matter -- with rare and fleeting particles of antimatter. Physicists call this problem CP violation, and it is one of the biggest unsolved problems in physics.

University of California, Davis


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Psychologists at Washington University in St. Louis have found an intriguing possibility that personality and brain aging during the golden years may be linked.

Studying MRI images of 79 volunteers between the ages of 44 and 88, who also had provided personality and demographic data, the researchers found lower volumes of gray matter in the frontal and medial temporal brain regions of volunteers who ranked high in neuroticism traits, compared with higher volumes of gray matter in those who ranked high in conscientious traits.

“This is a first step in seeing how personality might affect brain aging,” says Denise Head, PhD, assistant professor of psychology in Arts & Sciences at Washington University. “Our data clearly show an association between personality and brain volume, particularly in brain regions associated with emotional and social processing. This could be interpreted that personality may influence the rate of brain aging.”

She notes also that the results could be seen as “the tail wagging the dog.” That is, it is actually brain changes during aging that influence personality.

“Right now, we can’t disentangle those two, but we plan to in the future by conducting ongoing studies of the volunteers over time to note future structural changes,” Head says.

Head’s graduate student Jonathan Jackson, first author of a recently published paper on the research in Neurobiology in Aging, notes that he, and co-authors Head and David A. Balota, PhD, professor of psychology, tested the hypotheses that aging individuals high in neuroticism would show lower brain volume while those high in either conscientiousness or extroversion would have larger brain volume. The extroversion results were not clear, but the data validated the other two hypotheses.

“There are lots of nonhuman animal studies that suggest that chronic stress is associated with deleterious effects on the brain, and this helped us form the hypothesis that we’d see similar effects in older adults.” Jackson says. “We assumed that neuroticism would be negatively related to structural volume. We really focused on the prefrontal and medial temporal regions because they are the regions where you see the greatest age changes, and they are also seats of attention, emotion, and memory. We found that more neurotic individuals had smaller volumes in certain prefrontal and medial temporal parts of the brain than those who were less neurotic, and the opposite pattern was found with conscientiousness.”

“A unique thing that we’ve done is to reliably measure personality differences and associate them with age-related effects on brain structures in healthy middle-aged and older adults” Head says. “Specifically, we found that neuroticism was associated with greater age-related decline in brain volume whereas conscientiousness was associated with less age-related decline.”

The researchers were interested in healthy aging brains because down the road the findings might serve as a useful marker for later diagnosis of dementia. The volunteers they studied are normal control participants at Washington University’s Alzheimer’s Disease Research Center (ADRC), led by John C. Morris, MD, the Friedman Distinguished Professor of Neurology and director of the ADRC.

One of the first changes in Alzheimer's disease may be in personality. There is accumulating research from the ADRC and other institutions that suggest that people tend to become more neurotic and less conscientious in early stage Alzheimer's.

“It might be that changes in personality track onto those people more likely to develop Alzheimer's,” Jackson says. “It’s why we looked at older healthy adults because it’s important to track these relationships in healthy populations before you look at pathological ones.

"We know that there are degenerative processes going on before the diagnosis of Alzheimer's. We want to be able to see if the subtle personality changes might be particular to an early clinical picture and possibly see if one can predict who will become demented based on personality changes,” Jackson says.

Another way of looking at the findings, Head says, is that neuroticism might add an increasing vulnerability to the pathological processes that go on in aging, particularly in Alzheimer's.

“We will continue to pursue the relationship between personality and brain structure as one of the earlier processes in AD and hence a possible risk factor,” Head says.

(Photo: WUSTL)

Washington University in St. Louis


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Throughout written history there have been many abrupt ends to empires and civilizations that have little explanation. Political climates deteriorate, passions rise, revolts happen and the next thing you know--the culture is a thing of the past relegated to a short chapter in a textbook.

The natural world leaves a record in the form of tree rings, which can be read like a very detailed book, covering a long period of human history. Now a team of researchers has correlated the demise of Angkor, the capitol of the Khmer Empire in Cambodia, with a decades-long drought interspersed with intense monsoons in the 14th and 15th centuries.

Brendan Buckley of Lamont-Doherty Earth Observatory of Columbia University and his colleagues have put together a high-resolution record of periods of drought and moisture in Southeast Asia that is over three quarters of a millennium long from 1250 to 2008 AD. Their research was funded by the National Science Foundation's Paleoclimate Program, which is part of the directorate for geosciences.

Just as satellite photos do--large sets of information like this tree ring data bring into focus patterns and phenomena that are larger than one lifetime. In fact they are on the scale of civilizations.

A look at tree ring data, and an analysis of rain, drought and temperature can show a remarkable link from climate in the environment to climate in the king's court. And this has been shown to be true for the enigmatic demise of Angkor, an empire that stood strong from the 9th to 13th centuries.

Angkor was a city that relied heavily on water. The National Science Foundation-funded work of Buckley and his colleagues reveals that the mid- to late 1300's experienced persistently dry conditions that spanned decades, followed by several years of severe wetness that may have caused damage to the city's infrastructure. Afterwards, a shorter but more severe drought in the early 1400's may have been more than this urban complex could handle.

Bringing insights such as these into focus in the 21st century, there is a sense of urgency in interpreting what the natural world is telling us. The very cypress trees (Fokienia hodginsii) that allow the long-range glimpse backwards are becoming more and more rare as their wood is harvested for the illicit timber trade. The highlands of Vietnam and Laos are home to some of the region's most diverse biota, and are under threat of over-exploitation.

(Photo: Zina Deretsky, National Science Foundation)

National Science Foundation


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Argonne biochemist Daniel Schabacker could be considered a Sherlock Holmes of bioterrorism. Although he doesn’t carry around a pipe and magnifying glass as he attempts to nab the culprit, he has a far more powerful deductive tool: the biochip.

The biochip offers Schabacker and his colleagues at Loyola University (Ill.) a chance to determine the “signatures” of biological agents that can be used for bioterrorism, most notably the bacterium that causes anthrax, Bacillus anthracis. While some scientists have used DNA analysis to identify particular strains of the anthrax bacterium, the biochips help scientists and government officials to learn how anthrax bacteria are grown, narrowing the pool of potential suspects. This project, started only within the past couple of years, exemplifies the burgeoning field of microbial forensics.

"Microbial forensics is one of the biggest topics in counterterrorism today, and one of the biggest challenges in dealing with bioterrorism,” Schabacker said. "The proteomic analysis that we’re able to perform with our biochips provides a new and different set of information about biological agents than we’d been able to see before; it can provide us with a complete fingerprint of the organism that we can then use to more precisely identify its origin.”

According to Schabacker, most efforts in microbial forensics today rely on DNA analysis for their findings. But on its own, Schabacker said, DNA analysis may not be sufficient to give investigators all the information they need about a particular bioagent. “The problem with only using conventional DNA analysis is that it only tells you what strain you are dealing with, and strains used by the good guys can be obtained by our enemies. There can be dozens of labs that all share the same strain,” he said. “Our approach attacks the problem in a completely different way. We take advantage of the fact that unlike cellular DNA, bacterial proteins change dramatically when the growth or preparation of the bacterial culture is altered — and that information is incredibly important.”

Because the anthrax bacterium’s proteins hold a unique and detailed record of how the cells were generated and handled, Schabacker believes that pursuing DNA and protein analyses in concert could yield a comprehensive database that identifies the conditions used to prepare almost any B. anthracis culture.

“The ultimate goal of this project is to build a library of ‘signatures’ of B. anthracis grown and prepared under various conditions, which can be used to identify an unknown sample from a possible terrorist attack,” Schabacker said. “This will be a major help to investigators who seek to attribute the agent to a particular perpetrator.”

Schabacker plans to leverage basic studies on the anthrax bacterium from the laboratory of Loyola professor Adam Driks to make biochips into a powerful tool for investigators and other scientists.

Developed in the early part of the decade originally as a diagnostic tool, a biochip consists of a one-centimeter by one-centimeter array that contains anywhere between several dozen and several hundred "dots," or small drops. Each of these drops contains a unique protein, antibody or nucleic acid that will attach to a particular reagent.

Scientists obtain the anthrax proteins to create the biochip through a process called fractionation. Essentially, the scientists use chemicals to break open the anthrax bacterium and collect its cellular proteins. They then use another process to separate the individual proteins by their physiochemical properties.

This process creates hundreds of separate protein fractions, which are then deposited onto a single biochip. Scientists then use different chemicals, or reagents, to characterize the resulting biochips just as a detective would dust for fingerprints. Just like a police interview with a suspect, this chemical process is known as “interrogation.” When a reagent interacts with a particular protein fraction, that spot will “light up,” creating part of the protein signature.

Although the biochip technology has the potential to develop protein signatures of just about any biological agent, Schabacker and Driks have devoted their initial focus initially to B. anthracis. The spores produced by this bacterium, which cause anthrax, are relatively easily manufactured and dispersed, making the anthrax bacterium a relatively easily produced biological weapon.

“B. anthracis is a pretty forgiving species – it will grow in a bunch of different conditions,” Schabacker said. “It’s probably the single most attractive pathogen of choice to terrorists who don’t have a lot of really expensive equipment or expertise, and the spores are the perfect package for dispersion.”

An expert on anthrax, Driks and his laboratory pioneered the forensic analysis of the spore coat of the bacterium. Schabacker combined the biochip technology with fractionation technology developed by Eprogen, Inc., providing a nexus that connects government research, academia and industry.

Helping scientists track down terrorists isn’t the biochip’s only use. Biochips have already shown promise in diagnostic medicine. After developing the biochip technology, Schabacker licensed it to several companies, including Safeguard Biosciences in Toronto, Canada and Akonni Biosystems in Frederick, Maryland.

Instead of looking at anthrax, Eprogen has put biochips to use to look for common cancer biomarkers. That research could open the door for doctors to create “antibody profiles” that could help them design individualized drugs or treatment programs for patients.

The work Akonni has done focuses on identifying other pathogens – those not normally associated with terrorist activity. Soon, biochips may begin showing up in greater numbers in doctor’s offices around the country, as they provide accurate and speedy diagnoses of a wide variety of infections, such as those caused by Multidrug-Resistant Tuberculosis (MDR-TB) and the often deadly Methicillin-resistant Staphylococcus aureus (MRSA).

(Photo: ANL)

Argonne National Laboratory


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A newly discovered path for the conversion of sunlight to electricity could brighten the future for photovoltaic technology. Researchers with Lawrence Berkeley National Laboratory (Berkeley Lab) have found a new mechanism by which the photovoltaic effect can take place in semiconductor thin-films. This new route to energy production overcomes the bandgap voltage limitation that continues to plague conventional solid-state solar cells.

Working with bismuth ferrite, a ceramic made from bismuth, iron and oxygen that is multiferroic – meaning it simultaneously displays both ferroelectric and ferromagnetic properties – the researchers discovered that the photovoltaic effect can spontaneously arise at the nanoscale as a result of the ceramic’s rhombohedrally distorted crystal structure. Furthermore, they demonstrated that the application of an electric field makes it possible to manipulate this crystal structure and thereby control photovoltaic properties.

“We’re excited to find functionality that has not been seen before at the nanoscale in a multiferroic material,” said Jan Seidel, a physicist who holds joint appointments with Berkeley Lab’s Materials Sciences Division and the UC Berkeley Physics Department. “We’re now working on transferring this concept to higher efficiency energy-research related devices.”

Seidel is one of the lead authors of a paper in the journal Nature Nanotechnology that describes this work titled, “Above-bandgap voltages from ferroelectric photovoltaic devices.” Co-authoring this paper with Seidel were Seung-Yeul Yang, Steven Byrnes, Padraic Shafer,Chan-Ho Yang, Marta Rossell, Pu Yu, Ying-Hao Chu, James Scott, Joel Ager, Lane Martin and Ramamoorthy Ramesh.

At the heart of conventional solid-state solar cells is a p-n junction, the interface between a semiconductor layer with an abundance of positively-charged “holes,” and a layer with an abundance of negatively charged electrons. When photons from the sun are absorbed, their energy creates electron-hole pairs that can be separated within a “depletion zone,” a microscopic region at the p-n junction measuring only a couple of micrometers across, then collected as electricity. For this process to take place, however, the photons have to penetrate the material to the depletion zone and their energy has to precisely match the energy of the semiconductor’s electronic bandgap – the gap between its valence and conduction energy bands where no electron states can exist.

“The maximum voltage conventional solid-state photovoltaic devices can produce is equal to the energy of their electronic bandgap,” Seidel says. “Even for so called tandem-cells, in which several semiconductor p-n junctions are stacked, photovoltages are still limited because of the finite penetration depth of light into the material.”

Working through Berkeley Lab’s Helios Solar Energy Research Center, Seidel and his collaborators discovered that by applying white light to bismuth ferrite, a material that is both ferroelectric and antiferromagnetic, they could generate photovoltages within submicroscopic areas between one and two nanometers across. These photovoltages were significantly higher than bismuth ferrite’s electronic bandgap.

“The bandgap energy of the bismuth ferrite is equivalent to 2.7 volts. From our measurements we know that with our mechanism we can get approximately 16 volts over a distance of 200 microns. Furthermore, this voltage is in principle linear scalable, which means that larger distances should lead to higher voltages.”

Behind this new mechanism for photovoltage generation are domain walls – two-dimensional sheets that run through a multiferroic and serve as transition zones, separating regions of different ferromagnetic or ferroelectric properties. In their study, Seidel and his collaborators found that these domain walls can serve the same electron-hole separation purpose as depletion zones only with distinct advantages.

“The much smaller scale of these domain walls enables a great many of them to be stacked laterally (sideways) and still be reached by light,” Seidel says. “This in turn makes it possible to increase the photovoltage values well above the electronic bandgap of the material.”

The photovoltaic effect arises because at the domain walls the polarization direction of the bismuth ferrite changes, which leads to steps in the electrostatic potential. Through annealing treatments of the substrate upon which bismuth ferrite is grown, the material’s rhombohedral crystals can be induced to form domain walls that change the direction of electric field polarization by either 71, 109 or 180 degrees. Seidel and his collaborators measured the photovoltages created by the 71 and 109 degree domain walls.

“The 71 degree domain walls showed unidirectional in-plane polarization alignment and produced an aligned series of potential voltage steps,” Seidel says. “Although the potential step at the 109 degree domain was higher than the 71 degree domain, it showed two variants of the in-plane polarization which ran in opposite directions.”

Seidel and his colleagues were also able to use a 200 volt electric pulse to either reverse the polarity of the photovoltaic effect or turn it off altogether. Such controllability of the photovoltaic effect has never been reported in conventional photovoltaic systems, and it paves the way for new applications in nano-optics and nano-electronics.

“While we have not yet demonstrated these possible new applications and devices, we believe that our research will stimulate concepts and thoughts that are based on this new direction for the photovoltaic effect,” Seidel says.

(Photo: Seidel, et. al.)

Lawrence Berkeley National Laboratory


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Dutch researchers from the University of Nijmegen have discovered bacteria that oxidize the methane without oxygen. Instead, these bacteria used nitrite, commonly available in freshwater sediments in agricultural areas. Methane is a very stable molecule and its degradation was generally believed to be impossible without oxygen (or sulfate). Now an international team from the Netherlands, France and Germany has shown that the bacteria actually do use oxygen for methane oxidation. They produce this oxygen themselves, like plants - only without light. The oxygen is manufactured from the nitrite. Until now, scientists believed that the art of making oxygen was restricted to plants, algae and cyanobacteria. Now it looks as if the researchers are on the track of a mechanism which may have existed before green plants first appeared on earth.

The unravelling of the new oxygen producing pathway was difficult because the responsible microbe grows only very slowly and remained hidden inside a complex microbial community. For this reason, short DNA fragments were extracted from the community as a whole and sequenced with modern massive parallel sequencing technology. From these fragments the genome of the responsible bacterium could be stitched together. This demanding approach has been successful only a few times before. It was achieved by Denis Le Paslier and colleagues of Genoscope (Evry, France).

The genome showed very clearly that the known genes for N2O reduction were missing and that the organism was genetically dependent on oxygen. "The experimental and genetic data were clearly incompatible" says Marc Strous, who led the research effort in Nijmegen and has moved to the Max Planck Institute in Bremen in the meantime.

Given these circumstances, how was the organism able to obtain its energy from the oxidation of the relatively inert molecule methane (CH4) with nitrite (NO2-) as electron acceptor? That is like starting a fire under water. To solve this paradox, Marcel Kuypers and colleagues of the Max Planck Institute for Marine Microbiology were called to the rescue. Advanced microsensing and mass spectrometry confirmed that the paradox was real - both data were right and could only be explained by a new way of oxygen production. After one year of trying, Katharina Ettwig, who hopes to graduate on this work this year, was able to actually trap the oxygen and provide the experimental proof. She named the organism Methylomirabilis oxyfera (wonderful methane-eater making oxygen), as it uses two nitrogen monoxide molecules to produce nitrogen and oxygen which is then used to attack the inert methane molecule.

The scientists suggest that the newly discovered pathway of oxygen production may be a missing link that once, billions of years ago, made possible the evolution of oxygenic photosynthesis, now performed by plants. But it certainly forces a rethink of current understanding of the role of fertilizers in the methane cycle.

(Photo: Max Planck Institute for Marine Microbiology)

Max Planck Institute




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