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Written by Jo Smith
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Thursday, 02 September 2010 |
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Particle collision experiments reveal inadequacies in existing theory.
When protons collide, they produce roughly equal amounts of matter and antimatter - opposing materials that annihilate each other immediately. Crucially, however, there is a slight excess of matter. This asymmetry explains why matter prevails throughout the cosmos. Although these processes have long been recognized, the observable universe requires much larger amounts of matter to be left over than is possible under currently accepted laws of physics. Now, an international collaboration of scientists, working at the Fermilab Tevatron particle collider in Illinois, believe they are close to solving the puzzle. Their experiments have achieved a matter-antimatter disparity that could account for the amount of matter presently in existence. The findings, reported in the journals Physical Review Letters and Physical Review D, must now be replicated by other research groups working at Fermilab and the Large Hadron Collider in Europe. Already, though, the implication that something other than physics’ Standard Model is responsible for the disparity is sending waves throughout the scientific community. Roy Briere, of Carnegie Mellon University, Pittsburgh, said that the discovery could end up being one of the biggest milestones in high-energy physics. |
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Written by Sara Dietz
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Tuesday, 31 August 2010 |
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Researchers from the University of Cambridge have developed a major improvement for organic solar cells, reporting their results in the current issue of Applied Physics Letters. Organic solar cells have significant advantages over conventional solar cells: they have a low impact on the environment, manufacturing is cheap and because they based on flexible plastic sheets their applications outperform the current use of solar panels. Solar panels absorb energy from the sunlight and dissociate the charges to produce an electric current. Organic solar panels use conjugated polymers for light absorption. Until now, a technical difficulty had been that the charge dissociation of these materials is very poor and photo-induces energy that cannot be collected efficiently. Yana Vaynzof and his Cambridge team added an extra layer of material to overcome this problem: their system still relies on a organic polymer to catch the light, but works with an metal-oxide layer underneath it to increase the charge dissociation. This improved the efficiency of the solar panel from 30% for the unmodified devices to nearly 100% for panels with a metal-oxide layer.
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Written by Katy Wei
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Thursday, 26 August 2010 |
Research findings suggest new links between B vitamin deficiency and the degeneration of the ageing brain. The Californian Sacramento Area Latino Study on Aging (SALSA), involving nearly 1,800 Hispanic volunteers aged 60 to 101, has investigated the specific effect of B vitamins on brain degeneration since 1996. According to U.S. Department of Agriculture nutritionist Lindsay H. Allen, who also collaborated in the study, SALSA's research is necessary because many previous studies of B vitamins and brain function have given inconsistent or conflicting results. The B vitamin folate was found to be particularly significant in cognitive decline. An analysis of participants' blood samples and their respective performances in various tests indicated that lower levels of folate were associated with symptoms of dementia and poor brain function. In women, folate has also been linked to symptoms of depression, which is already linked to poorer neural performance. Female volunteers whose plasma folate levels were in the lowest third were more than twice as likely to have symptoms of depression as volunteers in the highest third. These findings were detected even though less than 1 percent of volunteers were actually deficient in folate. SALSA also determined that a protein known as holoTC, which is formed when vitamin B-12 is processed in the body, could form the basis of a new method to detect cognitive decline earlier and with greater accuracy than current techniques allow. These and other findings have been published by SALSA in various journals, including the American Journal of Clinical Nutrition, since 2003. |
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Written by Robert Jones
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Monday, 23 August 2010 |
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Princeton University geoscientists have discovered what they believe to be the earliest body-fossil evidence of animal life.
Fossils have been found in a rock formation in Southern Australia that are believed to be the calcified remains of millimetre- to centimetre-sized sponge-like marine creatures. Because the fossils were found below strata from the Marinoan glaciation, the sponges must have lived at least 635 million years ago, according to a report published in Nature Geoscience. The fossils pre-date the oldest known calcified fossils of this size by 90 million years, and are shaped like anvils, horseshoes, wishbones and perforated slabs. When constructed into three-dimensional models, they appear as ellipsoidal organisms with an asymmetric body plan. The sponge-grade metazoans likely lived as filter feeders in reefs at the bottom of shallow waters. Some specimens show evidence of stalks or holdfasts, and because they have a complex network of interior canals, these may not be the simplest or oldest sponges to have existed. As well as changing our perception of when the first animals appeared, this discovery firmly places early animal life in the second of two massive glaciations that punctuated the Neoproterozoic Era. Since animal life probably didn’t evolve twice, it appears that these sponges endured and survived the severe climatic event known as "Snowball Earth." During this episode the planet is believed to have been almost entirely covered in ice or slush, creating an extremely inhospitable environment. 100 million years later, in the Cambrian explosion, conditions allowed for a rapid diversification of life and the appearance of most major groups of complex animals. |
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Written by Robert Jones
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Sunday, 15 August 2010 |
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Research in the Panamanian rainforest shows that soil-dwelling organisms promote local species richness and keep the rare trees rare. A single hectare of the Amazonian rainforest may be home to several hundred species of tree, and because trees are at the centre of ecological communities, their diversity translates to variety in the organisms they support. The diversity of tree species is maintained by negative feedback processes in the local environment: seedlings growing close to members of their own species are kept in check by the accumulation of species-specific herbivores and pathogens that limit their survival. Although these patterns of negative feedback have been well documented, the biological mechanisms that control them have not been fully elucidated. Two recent studies of tropical tree communities in Panama have addressed this issue. By measuring survival close to trees of the same and different species, Comita and coworkers confirm in Science that seedlings were much more likely to die when they grow close to neighbouring trees of their own species. A second study, published by Mangan and colleagues in Nature showed that soil-dwelling organisms were responsible for the differences in mortality. Both studies found that the strength of the negative feedback constraints varied for different species, but unexpectedly, it was the rare species in the community that were most susceptible. This means that the relative abundances observed today are the result and not the cause of the negative feedback, with susceptibility to soil biota emerging as a major force in determining relative species abundance. Furthermore, the reports demonstrated that the strength of the feedback is sufficient to have a community-wide effect. This has important implications for conservation efforts, where an understanding of the mechanisms that control species abundances are essential, particularly because the rarest species have the least ability to regenerate.
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Written by Tim Middleton
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Tuesday, 10 August 2010 |
Scientists writing in Earth and Planetary Science Letters have reported new evidence for the existence of carbonate rocks on Mars. These carbonates provide a possible link to the presence of living organisms on Mars around 4 billion years ago. Researchers analysed images of the Martian surface that were recorded by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). These images are of the Nili Fossae region, one of the oldest sections of the Martian surface that formed in the Noachian Period (between 4.6 and 3.5 billion years ago). This portion of the Martian surface is composed primarily of a magnesium-rich igneous rock called komatiite. The researchers compared the spectra with airborne observations made in the Pilbara region of Western Australia. Different minerals are known to absorb at different frequencies in the infrared and visible parts of the electromagnetic spectrum. By matching peaks in both sets of spectra they deduced the presence of magnesium carbonate in the Nili Fossae region. They were also able to map the extent of the carbonates by setting a threshold absorption level. Furthermore, the team proposed that the carbonates are underlain not by saponite, as previously supposed, but talc, a hydrated magnesium silicate mineral. Former explanations for the existence of carbonate rocks on Mars have invoked evaporation in warm oceans under a carbon dioxide rich atmosphere. However, this research suggests that the various minerals present are likely to have formed via a series of chemical reactions as hot fluids moved through the originally igneous rock. This hydrothermal alteration is likely to have occurred in association with volcanic activity. On Earth, sites of hydrothermal activity such as this are prime locations for the creation and preservation of microfossils. Could the same be true on Mars? |
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Written by Katy Wei
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Monday, 09 August 2010 |
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Psychological
scientists have reported growing evidence that different cultures can
have a marked effect on fundamental brain function and structure.
Denise
C. Park and Chih-Mao Huang have reported growing evidence that
cultural difference between Westerners and East Asians has led to
differences in attention, categorisation and reasoning through effect
on neural function and neuroanatomy. East Asians, with a collectivist
culture, tend to process information in a global manner, whereas more
individualistic Westerners tend to focus on specific features and
objects.
Experiments
tracking volunteers' eye movements indicate that Westerners generally
spend more time looking at focal objects, while East Asians look more
at the contextual background. Facial information also seems to be
processed differently: when shown human faces, East Asians focussed
more on the central region of the faces while Westerners looked more
broadly, focusing on both the eyes and the mouth.
A
recent MRI study also suggests cultural values affect brain
structure. Westerners appear to have a thicker frontal cortex (areas
involved in reasoning) whereas East Asians had a thicker cortex in
perceptual areas. The evidence is limited, however, as the data is collected from two groups who differ in many systematic ways beyond cultural values.
"This research is an
important domain for understanding the malleability of the human
brain," Park and Huang conclude, "and how differences in values and social milieus sculpt the
brain's structure and function."
The study is published in the July edition of Perspectives
on Psychological Science.
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Written by Natalie Vokes
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Monday, 09 August 2010 |
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Researchers at Harvard and Boston University have found that the different pathways of the human metabolic network interact and induce deep epistasis, the suppression of a
mutation by one or more seemingly unrelated genes. Genome sequences alone apparently don't say much. While the Human Genome Project revealed the order of letters that make up the genetic code, we still do not understand how that code gets translated into the complex behaviors and traits that make us each functioning, unique human beings. Scientists have tackled the challenge of mapping genome sequence (genotype) to observable properties (phenotype) by studying how changing an individual gene affects the phenotype of interest. This approach is limited, however, because of a phenomenon called epistasis: different genes can interact in unpredictable and complicated ways such that the effects of gene A may vary depending on the state of gene B.
In a study recently published in the journal Chaos, Marcin Imielinski and Calin Belta addressed the challenge of understanding the epistasis in human metabolic networks, one of the most important and complex biological networks. Each cell in the human body must perform a complicated series of reactions to extract energy and construct essential building blocks. Scientists have long known that there are numerous pathways and enzymes involved in performing these tasks, but the complexity of the relationships between different metabolic pathways makes it hard to know how genetic differences affect these different reactions. In their study, Imielinski and Belta addressed this challenge by developing a mathematical construct to represent epistasis in cellular metabolism. Using the concept of a minimal cut set, that is, a set of reactions that together are necessary for a phenotype but individually are not, Imielinski and Belta revealed that many human metabolic pathways act in parallel with each other. This parallelism leads to what Imielinski and Belta call 'deep epistasis', by which individual metabolic pathways can buffer each other and thereby minimize the effects of individual genes.
In addition to providing a framework for analyzing the relationship between genetic variation and metabolic disease, this analysis is important for what it reveals about specific metabolic pathways. In particular, this analysis may be of use for cancer researchers. In the last decade, scientists have begun to pay more attention to the observation that cancer cells display a different metabolism than normal cells. This observation is exciting because it may not only help us better understand cancer, it may also help identify important and novel drug targets. Imielinski and Belta's analysis may help direct researchers toward genes whose suppression might inhibit pathways important to the growth and survival of cancer cells.
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