Wednesday, 30 October 2013
Oct. 27, 2013 — When you look at the hands of a clock or the streets on a map, your brain is effortlessly performing computations that tell you about the orientation of these objects. New research by UCL scientists has shown that these computations can be carried out by the microscopic branches of neurons known as dendrites, which are the receiving elements of neurons.The study, published today (Sunday) inNature and carried out by researchers based at the Wolfson Institute for Biomedical Research at UCL, the MRC Laboratory for Molecular Biology in Cambridge and the University of North Carolina at Chapel Hill, examined neurons in areas of the mouse brain which are responsible for processing visual input from the eyes. The scientists achieved an important breakthrough: they succeeded in making incredibly challenging electrical and optical recordings directly from the tiny dendrites of neurons in the intact brain while the brain was processing visual information.
These recordings revealed that visual stimulation produces specific electrical signals in the dendrites -- bursts of spikes -- which are tuned to the properties of the visual stimulus.
The results challenge the widely held view that this kind of computation is achieved only by large numbers of neurons working together, and demonstrate how the basic components of the brain are exceptionally powerful computing devices in their own right.
Senior author Professor Michael Hausser commented: "This work shows that dendrites, long thought to simply 'funnel' incoming signals towards the soma, instead play a key role in sorting and interpreting the enormous barrage of inputs received by the neuron. Dendrites thus act as miniature computing devices for detecting and amplifying specific types of input.
"This new property of dendrites adds an important new element to the "toolkit" for computation in the brain. This kind of dendritic processing is likely to be widespread across many brain areas and indeed many different animal species, including humans."
Funding for this study was provided by the Gatsby Charitable Foundation, the Wellcome Trust, and the European Research Council, as well as the Human Frontier Science Program, the Klingenstein Foundation, Helen Lyng White, the Royal Society, and the Medical Research Council
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Sunday, 27 October 2013
Oct. 25, 2013 — This genetic test is the result of a joint research of Computational Intelligence Group of the Department of Artificial Intelligence of the UPM with the Molecular Oncology Unit of the CIEMAT. This test would enhance patients' quality of life for those who have a good prognosis by avoiding chemotherapy as well as being a cost saving for hospitals.It is a genomic-clinical method able to determinate the prognosis of a patient with lung adenocarcinoma by studying the expression levels of 30 genes and combining the results with other indicators such as age, gender or the stage of the tumor. From this study, patients are classified into phases and from this classification depends their prognosis and treatment.
Although, there are clinical-pathological features that predict with accuracy the survival in patients, there are tumors with specific features that have diverse behaviors and, in these cases, the new method increases the predictions of the prognosis more significantly.
Lung cancer causes the most cancer deaths in males and females globally. The most common subtype is the adenocarcinoma cancer which represents the 40% of the total. In this way, the patented method could be useful for Oncology Services in hospitals. Therefore, the method will allow us to know with accuracy the survival probability after suffering an adenocarcionma and then, to apply the best treatment what would enhance the survival and patients' quality of life
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Oct. 24, 2013 — For most people, a bee sting causes temporary pain and discomfort, but for those with a bee venom allergy, the consequences can be devastating: They experience anaphylactic shock, including a drop in blood pressure, itchy hives and breathing problems, and may die if not promptly treated.New findings by Stanford University School of Medicine scientists may provide an evolutionary explanation for severe allergic reactions. In a paper to be published online Oct. 24 in Immunity, the researchers show that mice injected with a small dose of bee venom were later resistant to a potentially lethal dose of the same venom. The study is the first experimental evidence that the same immune response involved in allergies may have evolved to serve a protective role against toxins.
The study builds on earlier work by the researchers, characterizing the innate immune response to snake venom and honeybee venom. Innate immune responses occur in subjects exposed to a foreign substance, such as a pathogen or a toxic material like venom, for the first time. Immune cells called mast cells, which reside in most of the body's tissues, are poised to unleash signals that turn on defense responses when a pathogen or toxin intrudes. In a previous study, the researchers found that mast cells produce enzymes that can detoxify components of snake venom, and that mast cells can also enhance innate resistance to honeybee venom.
Such innate immune responses do not require prior immunization or the development of specific antibodies. By contrast, during an adaptive immune response, the immune system generates antibodies that recognize the invading pathogen or toxin; this process makes it possible to vaccinate against infectious diseases. Adaptive immunity is usually a faster, more specific and more effective form of defense than innate immunity.
In allergic reactions, a type of antibody called IgE binds to the surface of mast cells and prompts them to initiate an adaptive immune response when exposed to the antigen recognized by that IgE. "The functions of IgE and mast cells are mostly known in the context of allergies," said Thomas Marichal, DVM, PhD, a postdoctoral scholar and co-lead author of the study.
"It was kind of a dogma that most IgE-related responses are detrimental," said postdoctoral scholar Philipp Starkl, PhD, the other lead author. "We and others speculated that there should be some very positive evolutionary pressure to keep these cells and these antibodies, because if they were just bad and deleterious, they would have been eliminated."
The researchers hypothesized that IgE might be required for protection against a lethal sting, and that allergies are an extreme, and maladaptive, example of this type of defense. This idea, known as the toxin hypothesis of allergy, was first proposed by Margie Profet in 1991, but was largely ignored by immunologists until recently.
To find out whether adaptive immune responses could help mice resist bee venom, Marichal and Starkl first injected mice with a low dose of venom equivalent to one or two stings. The mice developed more venom-specific immune cells, and higher levels of IgE antibodies against the venom, than control mice injected with a salt solution.
Three weeks later, they injected both groups of mice with a potentially lethal dose of venom, similar to five bee stings. The immunized mice had less hypothermia and were three times more likely to survive than the control mice. Moreover, they did not develop the anaphylactic reactions characteristic of severe allergies.
To determine whether IgE antibodies were required for this protection, the team tested mice with three types of mutations: mice without IgE, mice without functional IgE receptors on their mast cells, and mice without mast cells. The IgE-deficient mutant mice were previously developed by Hans Oettgen, MD, PhD, associate professor of pediatric immunology at Harvard Medical School and a co-author of the study.
In all three groups of mutant mice, pre-immunization with a low dose of bee venom did not confer protection against a lethal dose, suggesting that the protection depends on IgE signaling and mast cell activation. "That was pretty exciting for us," said Marichal. "It was the first time we could see a beneficial function for these IgE antibodies."
Pre-immunization with a low dose of venom from the Russell's viper also protected mice from a higher dose of venom from this snake, which is one of the "big four" species responsible for most snakebite deaths in India. So the researchers believe the response could be generalized to different types of toxic venoms.
"Our findings support the hypothesis that this kind of venom-specific, IgE-associated, adaptive immune response developed, at least in evolutionary terms, to protect the host against potentially toxic amounts of venom, such as would happen if the animal encountered a whole nest of bees, or in the event of a snakebite," said Stephen Galli, MD, professor and chair of pathology and the co-senior author of the study. "Anaphylaxis probably represents the extreme end of a spectrum of IgE-associated reactivity, which in some unfortunate individuals is either poorly regulated or excessively robust, so the reaction itself can become dangerous to them."
Galli cautioned that it's not yet known whether IgE responses also protect humans from the toxic effects of arthropod or reptile venom, but it would be unthinkable to test lethal doses of venom in humans. Reptile and arthropod venoms are complex chemical cocktails. Some venom components have evolved to mimic chemicals made by the human body, such as endothelin-1, which causes blood vessels to constrict during bacterial infections. At the same time, mammals have evolved immune responses to venom, which in some cases escalate into maladaptive allergic reactions.
"We experience allergies in a much cleaner world, where we don't have the same threats of venomous creatures and potentially toxic food that existed for much of our evolutionary history," said Galli. "And so we're left with this residual type of reactivity that seems completely mysterious and pointless and harmful. This is the first evidence, that we know of, indicating that IgE-associated 'allergic-type' immune responses can actually reduce the toxicity of naturally occurring venoms.
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Oct. 25, 2013 — After taking an in-depth look at the basic biology of a fungus that is decimating bat colonies as it spreads across the U.S., researchers report that they can find little that might stop the organism from spreading further and persisting indefinitely in bat caves.
Their report appears in the journal PLOS ONE.
The aptly named fungusPseudogymnoascus (Geomyces) destructans causes white-nose syndrome in bats. The infection strikes bats during their winter hibernation, leaving them weakened and susceptible to starvation and secondary infections. The fungus, believed to have originated in Europe, was first seen in New York in the winter of 2006-2007, and now afflicts bats in more than two dozen states. According to the U.S. Fish and Wildlife Service, P. destructans has killed more than 5.5 million bats in the U.S. and Canada.
The fungus thrives at low temperatures, and spreads to bats whose body temperature drops below 20 degrees Celsius (68 degrees Fahrenheit) when they are hibernating in infected caves. Previous research has shown that the fungus persists in caves even after the bats are gone.
The new study, from researchers at the Illinois Natural History Survey at the University of Illinois, found that the fungus can make a meal out of just about any carbon source likely to be found in caves, said graduate student Daniel Raudabaugh, who led the research under the direction of survey mycologist Andrew Miller.
"It can basically live on any complex carbon source, which encompasses insects, undigested insect parts in guano, wood, dead fungi and cave fish," Raudabaugh said. "We looked at all the different nitrogen sources and found that basically it can grow on all of them. It can grow over a very wide range of pH; it doesn't have trouble in any pH unless it's extremely acidic."
"P. destructans appears to create an environment that should degrade the structure of keratin, the main protein in skin," Raudabaugh said. It has enzymes that break down urea and proteins that produce a highly alkaline environment that could burn the skin, he said. Infected bats often have holes in their skin, which can increase their susceptibility to other infections.
The fungus can subsist on other proteins and lipids on the bats' skin, as well as glandular secretions, the researchers said.
"P. destructans can tolerate naturally occurring inhibitory sulfur compounds, and elevated levels of calcium have no effect on fungal growth," Raudabaugh said.
The only significant limitation of the fungus besides temperatures above 20 degrees Celsius has to do with its ability to take up water, Raudabaugh said. Its cells are leaky, making it hard for the fungus to absorb water from surfaces, such as dry wood, that have a tendency to cling to moisture. But in the presence of degraded fats or free fatty acids, like those found on the skin of living or dead animals, the fungus can draw up water more easily, he said.
"All in all the news for hibernating bats in the U.S. is pretty grim," Miller said.
"When the fungus first showed up here in Illinois earlier this year we went from zero to 80 percent coverage in a little more than a month," he said. The team led by U. of I. researchers that discovered the fungus in the state found a single infected bat in one northern Illinois cave, he said. Several weeks later most of the bats in that cave were infected.
Although many studies have been done on the fungal genome and on the bats, Miller said, Raudabaugh is the first to take an in-depth look at the basic biology of the fungus.
"Dan found that P. destructans can live perfectly happily off the remains of most organisms that co-inhabit the caves with the bats," Miller said. "This means that whether the bats are there or not, it's going to be in the caves for a very long time."
The Illinois Natural History Survey is a division of the Prairie Research Institute at the U. of I.
This study was funded through awards given by the Illinois Department of Natural Resources State Wildlife Grants Program (project number T-78-R-1) and the Section 6 Endangered and Threatened Species Program (project number E-54-R-1) to the Illinois Natural History Survey.
Oct. 25, 2013 — At least 441 new species of animals and plants have been discovered over a four year period in the vast, underexplored rainforest of the Amazon, including a monkey that purrs like a cat.
Found between 2010 and 2013, the species include a flame-patterned lizard, a thumbnail-sized frog, a vegetarian piranha, a brightly coloured snake, and a beautiful pink orchid, according to World Wildlife Fund (WWF).
Discovered by a group of scientists and compiled by WWF, the new species number 258 plants, 84 fish, 58 amphibians, 22 reptiles, 18 birds and one mammal. This total does not include countless discoveries of insects and other invertebrates.
"These species form a unique natural heritage that we need to conserve. This means protecting their home -- the amazing Amazon rainforest -- which is under threat from deforestation and dam development," said Claudio Maretti, Leader of Living Amazon Initiative, WWF.
Some of the most remarkable species outlined in the report include:
• Flame-patterned lizard: This beautiful lizard was found from the hatchlings of eggs collected by scientists in the Colombian Amazon. An elusive species, Cercosaura hypnoides, has not been seen in the wild since the original eggs were collected, raising the prospect that it could potentially be endangered.
• Thumbnail-sized frog: This amphibian is already believed to be highly endangered. In fact, its Latin name, Allobates amissibilis, meaning "that may be lost," alludes to this as the area where it thrives could soon be opened to tourism. This is now the third Allobates species found in Guyana.
• Vegetarian Piranha: This new species of piranha, Tometes camunani, can span 20 inches wide and weigh up to 9 pounds, and is strictly herbivorous. The freshwater fish inhabits rocky rapids associated with seedlings of plants that grow among the rocks, its main source of food. Tometes is described from the upper drainages of the Trombetas River basin, Para, Brazilian Amazon.
• A brightly coloured snake from the "Lost World": Found in the mountains of Guyana, this brightly-colored snake species was named Chironius challenger after Arthur C. Doyle's fictional character Professor George Edward Challenger in the novel, The Lost World.
• A beautiful pink orchid: Among the new plant species are a large number of new orchid species, including this splendid pink species, Sobralia imavieirae, officially described by scientists from Roraima in the Brazilian Amazon.
• Caqueta titi monkey: This new species, Callicebus caquetensis, is one of about 20 species of titi monkey, which all live in the Amazon basin. The babies have an endearing trait, "When they feel very content they purr towards each other," explained scientist Thomas Defler.
Many of the new discoveries are believed to be endemic to the Amazon rainforest and are found nowhere else in the world. This makes them even more vulnerable to rainforest destruction that occurs every minute across the Amazon.
"Compiling and updating data on new species discovered in the vast extension of the Amazon over the last four years has shown us just how important the region is for humanity and how fundamentally important it is to research it, understand it and conserve it. The destruction of these ecosystems is threatening biodiversity and the services it provides to societies and economies. We cannot allow this natural heritage to be lost forever," Maretti said
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Oct. 24, 2013 — At a cosmologically crisp one degree Kelvin (minus 458 degrees Fahrenheit), the Boomerang Nebula is the coldest known object in the Universe -- colder, in fact, than the faint afterglow of the Big Bang, which is the natural background temperature of space.Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope have taken a new look at this intriguing object to learn more about its frigid properties and determine its true shape, which has an eerily ghost-like appearance.
As originally observed with ground-based telescopes, this nebula appeared lopsided, which is how it got its name. Later observations with the Hubble Space Telescope revealed a bow-tie-like structure. The new ALMA data, however, reveal that the Hubble image tells only part of the story, and the twin lobes seen in that image may actually be a trick of the light as seen at visible wavelengths.
"This ultra-cold object is extremely intriguing and we're learning much more about its true nature with ALMA," said Raghvendra Sahai, a researcher and principal scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, and lead author of a paper published in the Astrophysical Journal. "What seemed like a double lobe, or 'boomerang' shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space."
The Boomerang Nebula, located about 5,000 light-years away in the constellation Centaurus, is a relatively young example of an object known as a planetary nebula. Planetary nebulae, contrary to their name, are actually the end-of-life phases of stars like our Sun that have sloughed off their outer layers. What remains at their centers are white dwarf stars, which emit intense ultraviolet radiation that causes the gas in the nebulae to glow and emit light in brilliant colors.
The Boomerang is a pre-planetary nebula, representing the stage in a star's life immediately preceding the planetary nebula phase, when the central star is not yet hot enough to emit sufficient ultraviolet radiation to produce the characteristic glow. At this stage, the nebula is seen by starlight reflecting off its dust grains.
The outflow of gas from this particular star is expanding rapidly and cooling itself in the process. This is similar in principle to the way refrigerators use expanding gas to produce cold temperatures. The researchers were able to take the temperature of the gas in the nebula by seeing how it absorbed the cosmic microwave background radiation, which has a very uniform temperature of 2.8 degrees Kelvin (minus 455 degrees Fahrenheit).
"When astronomers looked at this object in 2003 with Hubble, they saw a very classic 'hourglass' shape," commented Sahai. "Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant."
Observations with single-dish millimeter wavelength telescopes, however, did not detect the narrow waist seen by Hubble. Instead, they found a more uniform and nearly spherical outflow of material.
ALMA's unprecedented resolution allowed the researchers to reconcile this discrepancy. By observing the distribution of carbon monoxide molecules, which glow brightly at millimeter wavelengths, the astronomers were able to detect the double-lobe structure that is seen in the Hubble image, but only in the inner regions of the nebula. Further out, they actually observed a more elongated cloud of cold gas that is roughly round.
The researchers also discovered a dense lane of millimeter-sized dust grains surrounding the star, which explains why this outer cloud has an hourglass shape in visible light. These dust grains have created a mask that shades a portion of the central star and allows its light to leak out only in narrow but opposite directions into the cloud, giving it an hourglass appearance.
"This is important for the understanding of how stars die and become planetary nebulae," said Sahai. "Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star."
The new research also indicated that the outer fringes of the nebula are beginning to warm, even though they are still slightly colder than the cosmic microwave background. This warming may be due to the photoelectric effect -- an effect first proposed by Einstein in which light is absorbed by solid material, which then re-emits electrons.
Additional authors on this paper include Wouter Vlemmings, Chalmers University of Technology, Onsala, Sweden; Patrick Huggins, New York University, New York; Lars-Ake Nyman, Joint ALMA Observatory, Santiago de Chile; and Yiannis Gonidakis, CSIRO, Australia Telescope National Facility.
ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc
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Oct. 24, 2013 — Cosmochemists have solved a long standing mystery in the formation of the solar system: Oxygen, the most abundant element in Earth's crust, follows a strange, anomalous pattern in the oldest, most pristine rocks, one that must result from a different chemical process than the well-understood reactions that form minerals containing oxygen on Earth.
"Whatever the source of the anomaly must be a major process in the formation of the solar system, but it has remained a matter of contention," said Mark Thiemens, dean of the University of California, San Diego's division of physical sciences and professor of chemistry. "Our experiments essentially recreate the early solar system in that they take gas phase molecules and make a solid, a silicate that is essentially the building block of planets."
By re-creating conditions in the solar nebula, the swirl of gas that coalesced to form our star, the planets and the remnant rocky debris that circles the Sun as asteroids, the researchers demonstrated that a simple chemical reaction, governed by known physical principles, can generate silicate dust with oxygen anomalies that match those found in the oldest rocks in the solar system, they report in the early online edition of ScienceOctober 24.
Scientists first noted the discrepancy forty years ago in a stony meteorite that exploded over Pueblito de Allende, Mexico, and it has been confirmed in other meteorites as well. These stony meteorites, asteroids that fell to Earth, are some of the oldest objects in the solar system, believed to have formed nearly 4.6 billion years ago with the solar nebula's first million years. The mix between oxygen-16, the most abundant form with one neutron for each proton, and variants with an extra neutron or two, is strikingly different from that seen in terrestrial rocks from Earth, its moon and Mars.
"Oxygen isotopes in meteorites are hugely different from those of the terrestrial planets," said Subrata Chakraborty, a project scientist in chemistry at UC San Diego and the lead author of the report. "With oxygen being the third most abundant element in the universe and one of the major rock forming elements, this variation among different solar system bodies is a puzzle that must be solved to understand how the solar system formed and evolved."
Oxygen isotopes usually sort out according to mass: oxygen-17, with just one extra neutron, is incorporated into molecules half as often as oxygen-18, with two extra neutrons. In these stony meteorites though, the two heavier oxygen isotopes show up in equal proportions. The rates at which they are incorporated into minerals forming these earliest rocks was independent of their masses. Thiemens and John Heidenreich demonstrated such mass-independent fractionation of oxygen isotopes in the formation of ozone thirty years ago, but the mechanism for a similar process in forming the solid building blocks of rocks has not be demonstrated experimentally before now.
Indeed, several competing ideas have been put forth as potential explanations for the anomaly. Some have suggested that the mix of oxygen isotopes was different back when the earliest solid matter in the solar system formed, perhaps enriched by matter blasted in from a nearby supernova. Others had proposed a photochemical effect called self-shielding, which this team has previously ruled out. The last-standing idea was that a physical chemical principle called symmetry could account for the observed patterns of oxygen isotopes.
To test that idea, Chakraborty filled a hockey puck sized chamber with pure oxygen, varying amounts of pure hydrogen and a little black nugget of solid silicon monoxide. He used a laser to vaporize a plume of silicon monoxide gas into the mix. These are ingredients seen by radiotelescopes in instellar clouds, the starting point for our solar system.
The silicon monoxide gas reacted with the oxygen and hydrogen to form silicon dioxide, a solid that settled as dust in the chamber and is the basis of silicate minerals like quartz that are so prevalent in the crust of Earth. These reactions of gases formed the earliest solid materials in the solar system.
When Chakraborty and Petia Yanchulova, a physics student and co-author of the paper, collected and analyzed the dust, they saw a mix of oxygen isotopes that matched the anomalous pattern found in stony meteorites. The degree of the anomaly scaled with the percentage of the atmosphere that was hydrogen, an observation that points to a reaction governed by symmetry.
"No mattter what else happened early on in the nebula, this is the last step in making the first rocks from scratch," Thiemens said. "We've shown that you don't need a magic recipe to generate this oxygen anomaly. It's just a simple feature of physical chemistry."
Oct. 24, 2013 — For the first time ever, scientists have documented a widespread extinction of bees that occurred 65 million years ago, concurrent with the massive event that wiped out land dinosaurs and many flowering plants. Their findings, published this week in the journal PLOS ONE, could shed light on the current decline in bee species.
Lead author Sandra Rehan, an assistant professor of biological sciences at UNH, worked with colleagues Michael Schwarz at Australia's Flinders University and Remko Leys at the South Australia Museum to model a mass extinction in bee group Xylocopinae, or carpenter bees, at the end of the Cretaceous and beginning of the Paleogene eras, known as the K-T boundary.
Previous studies have suggested a widespread extinction among flowering plants at the K-T boundary, and it's long been assumed that the bees who depended upon those plants would have met the same fate. Yet unlike the dinosaurs, "there is a relatively poor fossil record of bees," says Rehan, making the confirmation of such an extinction difficult.
Rehan and colleagues overcame the lack of fossil evidence for bees with a technique called molecular phylogenetics. Analyzing DNA sequences of four "tribes" of 230 species of carpenter bees from every continent except Antarctica for insight into evolutionary relationships, the researchers began to see patterns consistent with a mass extinction. Combining fossil records with the DNA analysis, the researchers could introduce time into the equation, learning not only how the bees are related but also how old they are.
"The data told us something major was happening in four different groups of bees at the same time," says Rehan, of UNH's College of Life Sciences and Agriculture. "And it happened to be the same time as the dinosaurs went extinct."
While much of Rehan's work involves behavioral observation of bees native to the northeast of North America, this research taps the computer-heavy bioinformatics side of her research, assembling genomic data to elucidate similarities and differences among the various species over time. Marrying observations from the field with genomic data, she says, paints a fuller picture of these bees' behaviors over time.
"If you could tell their whole story, maybe people would care more about protecting them," she says. Indeed, the findings of this study have important implications for today's concern about the loss in diversity of bees, a pivotal species for agriculture and biodiversity.
"Understanding extinctions and the effects of declines in the past can help us understand the pollinator decline and the global crisis in pollinators today," Rehan says.
The article, "First evidence for a massive extinction event affecting bees close to the K-T boundary," was published in the Oct. 23, 2013 edition of PLOS ONE. Funding for the research was provided by Endeavour Research Fellowships (Rehan) and Australian Research Council Discovery Grants (Schwarz).
The University of New Hampshire, founded in 1866, is a world-class public research university with the feel of a New England liberal arts college. A land, sea, and space-grant university, UNH is the state's flagship public institution, enrolling 12,300 undergraduate and 2,200 graduate students.
Oct. 24, 2013 — The heat is on, at least in the Arctic. Average summer temperatures in the Eastern Canadian Arctic during the last 100 years are higher now than during any century in the past 44,000 years and perhaps as long ago as 120,000 years, says a new University of Colorado Boulder study.The study is the first direct evidence the present warmth in the Eastern Canadian Arctic exceeds the peak warmth there in the Early Holocene, when the amount of the sun's energy reaching the Northern Hemisphere in summer was roughly 9 percent greater than today, said CU-Boulder geological sciences Professor Gifford Miller, study leader. The Holocene is a geological epoch that began after Earth's last glacial period ended roughly 11,700 years ago and which continues today.
Miller and his colleagues used dead moss clumps emerging from receding ice caps on Baffin Island as tiny clocks. At four different ice caps, radiocarbon dates show the mosses had not been exposed to the elements since at least 44,000 to 51,000 years ago.
Since radiocarbon dating is only accurate to about 50,000 years and because Earth's geological record shows it was in a glaciation stage prior to that time, the indications are that Canadian Arctic temperatures today have not been matched or exceeded for roughly 120,000 years, Miller said.
"The key piece here is just how unprecedented the warming of Arctic Canada is," said Miller, also a fellow at CU-Boulder's Institute of Arctic and Alpine Research. "This study really says the warming we are seeing is outside any kind of known natural variability, and it has to be due to increased greenhouse gases in the atmosphere."
A paper on the subject appeared online Oct. 21 in Geophysical Research Letters, a journal published by the American Geophysical Union. Co-authors include CU-Boulder Senior Research Associate Scott Lehman, former CU-Boulder doctoral student and now Prescott College Professor Kurt Refsnider, University of California Irvine researcher John Southon and University of Wisconsin, Madison Research Associate Yafang Zhong. The National Science Foundation provided the primary funding for the study.
Miller and his colleagues compiled the age distribution of 145 radiocarbon-dated plants in the highlands of Baffin Island that were exposed by ice recession during the year they were collected by the researchers. All samples collected were within 1 meter of the ice caps, which are generally receding by 2 to 3 meters a year. "The oldest radiocarbon dates were a total shock to me," said Miller.
Located just east of Greenland, the 196,000-square-mile Baffin Island is the fifth largest island in the world. Most of it lies above the Arctic Circle. Many of the ice caps on the highlands of Baffin Island rest on relatively flat terrain, usually frozen to their beds. "Where the ice is cold and thin, it doesn't flow, so the ancient landscape on which they formed is preserved pretty much intact," said Miller.
To reconstruct the past climate of Baffin Island beyond the limit of radiocarbon dating, Miller and his team used data from ice cores previously retrieved by international teams from the nearby Greenland Ice Sheet.
The ice cores showed that the youngest time interval from which summer temperatures in the Arctic were plausibly as warm as today is about 120,000 years ago, near the end of the last interglacial period. "We suggest this is the most likely age of these samples," said Miller.
The new study also showed summer temperatures cooled in the Canadian Arctic by about 5 degrees Fahrenheit from roughly 5,000 years ago to about 100 years ago -- a period that included the Little Ice Age from 1275 to about 1900.
"Although the Arctic has been warming since about 1900, the most significant warming in the Baffin Island region didn't really start until the 1970s," said Miller. "And it is really in the past 20 years that the warming signal from that region has been just stunning. All of Baffin Island is melting, and we expect all of the ice caps to eventually disappear, even if there is no additional warming."
Temperatures across the Arctic have been rising substantially in recent decades as a result of the buildup of greenhouse gases in Earth's atmosphere. Studies by CU-Boulder researchers in Greenland indicate temperatures on the ice sheet have climbed 7 degrees Fahrenheit since 1991.
A 2012 study by Miller and colleagues using radiocarbon-dated mosses that emerged from under the Baffin Island ice caps and sediment cores from Iceland suggested that the trigger for the Little Ice Age was likely a combination of exploding tropical volcanoes -- which ejected tiny aerosols that reflected sunlight back into space -- and a decrease in solar radiation
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Oct. 24, 2013 — What sounds like a dream of the future has already been the subject of research for a few years: simply printing out tissue and organs. Now scientists have further refined the technology and are able to produce various tissue types.The recent organ transplant scandals have only made the problem worse. According to the German Organ Transplantation Foundation (DSO), the number of organ donors in the first half of 2013 has declined more than 18 percent in comparison to the same period the previous year. At the same time, one can assume that the demand in the next years will continuously rise, because we continue to age and field of transplantation medicine is continuously advancing. Many critical illnesses can already be successfully treated today by replacing cells, tissue, or organs. Government, industry, and the research establishment have therefore been working hard for some time to improve methods and procedures for artificially producing tissue. This is how the gap in supply is supposed to be closed.
Bio-ink made from living cells
One technology might assume a decisive role in this effort, one that we are all familiar with from the office, and that most of us would certainly not immediately connect with the production of artificial tissue: the inkjet printer. Scientists of the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB) in Stuttgart have succeeded in deve- loping suitable bio-inks for this printing technology. The transparent liquids consist of components from the natural tissue matrix and living cells. The substance is based on a well known biological material: gelatin. Gelatin is derived from collagen, the main constituent of native tissue. The researchers have chemically modified the gelling behavior of the gelatin to adapt the biological molecules for printing. Instead of gelling like unmodified gelatin, the bio-inks remain fluid during printing. Only after they are irradiated with UV light, they crosslink and cure to form hydrogels. These are polymers containing a huge amount of water (just like native tissue), but which are stable in aqueous environments and when being warmed up to physiological 37°C. The researchers can control the chemical modification of the biological molecules so that the resulting gels have differing strengths and swelling characteristics. The properties of natural tissue can therefore be imitated -- from solid cartilage to soft adipose tissue.
In Stuttgart synthetic raw materials are printed as well that can serve as substitutes for the extracellular matrix. For example a system that cures to a hydrogel devoid of by-products, and can be immediately populated with genuine cells. "We are concentrating at the moment on the 'natural' variant. That way we remain very close to the original material. Even if the potential for synthetic hydrogels is big, we still need to learn a fair amount about the interactions between the artificial substances and cells or natural tissue. Our biomolecule-based variants provide the cells with a natural environment instead, and therefore can promote the self-organizing behavior of the printed cells to form a functional tissue model," explains Dr. Kirsten Borchers in describing the approach at IGB.
The printers at the labs in Stuttgart have a lot in common with conventional office printers: the ink reservoirs and jets are all the same. The differences are discovered only under close inspection. For example, the heater on the ink container with which the right temperature of the bio-inks is set. The number of jets and tanks is smaller than in the office counterpart as well. "We would like to increase the number of these in cooperation with industry and other Fraunhofer Institutes in order to simultaneously print using various inks with different cells and matrices. This way we can come closer to replicating complex structures and different types of tissue," says Borchers.
The big challenge at the moment is to produce vascularized tissue. This means tissue that has its own system of blood vessels through which the tissue can be provided with nutrients. IGB is working on this jointly with other partners under Project ArtiVasc 3D, supported by the European Union. The core of this project is a technology platform to generate fine blood vessels from synthetic materials and thereby create for the first time artificial skin with its subcutaneous adipose tissue. "This step is very important for printing tissue or entire organs in the future. Only once we are successful in producing tissue that can be nourished through a system of blood vessels can printing larger tissue structures become feasible," says Borchers in closing. She will be exhibiting the IGB bioinks at Biotechnica in Hanover, 8-10 October 2013 (Hall 9, Booth E09)
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Oct. 23, 2013 — University of California, Riverside astronomers Bahram Mobasher and Naveen Reddy are members of a team that has discovered the most distant galaxy ever found. The galaxy is seen as it was just 700 million years after the Big Bang, when the universe was only about 5 percent of its current age of 13.8 billion years.Results appears in the Oct. 24 issue of the journal Nature.
In collaboration with astronomers at the University of Texas at Austin, Texas A & M University, and the National Optical Astronomy Observatories, Mobasher and Reddy identified a very distant galaxy candidate using deep optical and infrared images taken by the Hubble Space Telescope. Follow-up observations of this galaxy by the Keck Telescope in Hawai'i confirmed its distance.
In searching for distant galaxies, the team selected several candidates, based on their colors, from the approximately 100,000 galaxies identified in the Hubble Space Telescope images taken as a part of the CANDELS survey, the largest project ever performed by the Hubble Space Telescope, with a total allocated time of roughly 900 hours. However, using colors to sort galaxies is tricky because some nearby objects can masquerade as distant galaxies.
Therefore, to measure the distance to these galaxies in a definitive way, astronomers use spectroscopy -- specifically, how much the wavelength of a galaxy's light has shifted towards the red-end of the spectrum as it travels from the galaxy to Earth, due to the expansion of the universe. This phenomenon is called "redshift." Since the expansion velocity (redshift) and distances of galaxies are proportional, the redshift gives astronomers a measure of the distance to galaxies.
"What makes this galaxy unique, compared to other such discoveries, is the spectroscopic confirmation of its distance," said Mobasher, a professor of physics and observational astronomy.
Mobasher explained that because light travels at about 186,000 miles per second, when we look at distant objects, we see them as they appeared in the past. The more distant we push these observations, the farther into the past we can see.
"By observing a galaxy that far back in time, we can study the earliest formation of galaxies," he said. "By comparing properties of galaxies at different distances, we can explore the evolution of galaxies throughout the age of the universe."
The discovery was made possible by a new instrument, MOSFIRE, commissioned on the Keck Telescope. Not only is the instrument extremely sensitive, but it is designed to detect infrared light -- a region of the spectrum to where the wavelength of light emitted from distant galaxies is shifted -- and could target multiple objects at a time. It was the latter feature that allowed the researchers to observe 43 galaxy candidates in only two nights at Keck, and obtain higher quality observations than previous studies.
By performing spectroscopy on these objects, researchers are able to accurately gauge the distances of galaxies by measuring a feature from the ubiquitous element hydrogen called the Lyman alpha transition. It is detected in most galaxies that are seen from a time more than one billion years from the Big Bang, but as astronomers probe earlier in time, the hydrogen emission line, for some reason, becomes increasingly difficult to see.
Of the 43 galaxies observed with MOSFIRE, the research team detected this Lyman alpha feature from only one galaxy, z8-GND-5296, shifted to a redshift of 7.5. The researchers suspect they may have zeroed in on the era when the universe made its transition from an opaque state in which most of the hydrogen is neutral to a translucent state in which most of the hydrogen is ionized (called the Era of Re-ionization).
"The difficulty of detecting the hydrogen emission line does not mean that the galaxies are absent," said Reddy, an assistant professor of astronomy. "It could be that they are hidden from detection behind a wall of neutral hydrogen."
The team's observations showed that z8-GND-5296 is forming stars extremely rapidly -- producing each year ~300 times the mass of our sun. By comparison, the Milky Way forms only two to three stars per year. The new distance record-holder lies in the same part of the sky as the previous record-holder (redshift 7.2), which also happens to have a very high rate of star-formation.
"So we're learning something about the distant universe," said Steven Finkelstein at the University of Texas at Austin, who led the project. "There are way more regions of very high star formation than we previously thought. There must be a decent number of them if we happen to find two in the same area of the sky."
"With the construction and commissioning of larger ground-based telescopes -- the Thirty Meter Telescope in Hawai'i and Giant Magellan Telescope in Chile -- and the 6.5 meter James Webb Space Telescope in space, by the end of this decade we should expect to find many more such galaxies at even larger distances, allowing us to witness the process of galaxy formation as it happens," Mobasher said
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Oct. 23, 2013 — Eucalyptus trees in the Kalgoorlie region of Western Australia are drawing up gold particles from Earth via their root system and depositing it their leaves and branches.Scientists from CSIRO made the discovery and have published their findings in the journal Nature Communications.
"The eucalypt acts as a hydraulic pump -- its roots extend tens of metres into the ground and draw up water containing the gold. As the gold is likely to be toxic to the plant, it's moved to the leaves and branches where it can be released or shed to the ground," CSIRO geochemist Dr Mel Lintern said.
The discovery is unlikely to start an old-time gold rush -- the "nuggets" are about one-fifth the diameter of a human hair. However, it could provide a golden opportunity for mineral exploration, as the leaves or soil underneath the trees could indicate gold ore deposits buried up to tens of metres underground and under sediments that are up to 60 million years old.
"The leaves could be used in combination with other tools as a more cost effective and environmentally friendly exploration technique," Dr Lintern said.
"By sampling and analysing vegetation for traces of minerals, we may get an idea of what's happening below the surface without the need to drill. It's a more targeted way of searching for minerals that reduces costs and impact on the environment.
"Eucalyptus trees are so common that this technique could be widely applied across Australia. It could also be used to find other metals such as zinc and copper."
Using CSIRO's Maia detector for x-ray elemental imaging at the Australian Synchrotron, the research team was able to locate and see the gold in the leaves. The Synchrotron produced images depicting the gold, which would otherwise have been untraceable.
"Our advanced x-ray imaging enabled the researchers to examine the leaves and produce clear images of the traces of gold and other metals, nestled within their structure," principal scientist at the Australian Synchrotron Dr David Paterson said.
"Before enthusiasts rush to prospect this gold from the trees or even the leaf litter, you need to know that these are tiny nuggets, which are about one-fifth the diameter of a human hair and generally invisible by other techniques and equipment."
CSIRO research using natural materials, such as calcrete and laterite in soils, for mineral exploration has led to many successful ore deposit discoveries in regional Australia. The outcomes of the research provide a direct boost to the national economy
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Oct. 23, 2013 — A paper in a recent issue of the journal Science [18 October] pits the front-running ideas about the growth of supermassive black holes against observational data -- a limit on the strength of gravitational waves from pairs of black holes, obtained with CSIRO's 64-m Parkes radio telescope in eastern Australia. The study was jointly led by Dr Ryan Shannon, a Postdoctoral Fellow with CSIRO, and Mr Vikram Ravi, a PhD student co-supervised by the University of Melbourne (Australia) and CSIRO.
"For the first time, we've used information about gravitational waves as a tool in astrophysics," said Dr Shannon.
"It's a powerful new tool. These black holes are very hard to observe directly, so this is a new chapter in astronomy."
"One model for black-hole growth has failed our test and we're painting the others into a corner. They may not break, but they'll have to bend," said Mr Ravi.
Einstein predicted gravitational waves -- ripples in space-time, generated by bodies changing speed or direction. Bodies, for instance, such as pairs of black holes orbiting each other.
When galaxies merge, their resident central black holes are doomed to meet. They first waltz together then enter a desperate embrace and merge.
"Theorists predict that towards the end of this dance they're growling out gravitational waves at a frequency we're set up to detect," Dr Shannon said.
Played out again and again across the Universe, such encounters create a background of gravitational waves, like the noise from a restless crowd.
Astronomers have been searching for gravitational waves with the Parkes radio telescope and a set of 20 small, spinning stars called pulsars.
Pulsars act as extremely precise clocks in space. We measure when their pulses arrive on Earth to within a tenth of a microsecond.
As gravitational waves roll through an area of space-time, they temporarily swell or shrink the distances between objects in that region. "That can alter the arrival time of the pulses on Earth," said Dr Michael Keith of the University of Manchester in the UK.
The Parkes Pulsar Timing Array (PPTA) project and an earlier collaboration between CSIRO and Swinburne University together provide nearly 20 years' worth of timing data.
"We haven't yet detected gravitational waves outright, but we're now into the right ballpark to do so," said the project leader, CSIRO's Dr George Hobbs.
Combining pulsar-timing data from Parkes with that from other telescopes in Europe and the USA -- a total of about 50 pulsars -- should give us the accuracy to detect gravitational waves "within ten years," he said.
Meanwhile, the PPTA results are showing us how low the background rate of gravitational waves is.
The strength of the gravitational wave background depends on how often supermassive black holes spiral together and merge, how massive they are, and how far away they are. So if the background is low, that puts a limit on one or more of those factors.
Armed with the PPTA data, the researchers tested four models of black-hole growth. They effectively ruled out black holes gaining mass only through mergers, but the other three models "are still in the game," said Dr Sarah Burke-Spolaor of California Institute of Technology (Caltech)
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Thursday, 24 October 2013
Oct. 20, 2013 — Everyone grows older, but scientists don't really understand why. Now a UCLA study has uncovered a biological clock embedded in our genomes that may shed light on why our bodies age and how we can slow the process. Published in the Oct. 21 edition of Genome Biology, the findings could offer valuable insights into cancer and stem cell research.While earlier clocks have been linked to saliva, hormones and telomeres, the new research is the first to identify an internal timepiece able to accurately gauge the age of diverse human organs, tissues and cell types. Unexpectedly, the clock also found that some parts of the anatomy, like a woman's breast tissue, age faster than the rest of the body.
"To fight aging, we first need an objective way of measuring it. Pinpointing a set of biomarkers that keeps time throughout the body has been a four-year challenge," explained Steve Horvath, a professor of human genetics at the David Geffen School of Medicine at UCLA and of biostatistics at the UCLA Fielding School of Public Health. "My goal in inventing this clock is to help scientists improve their understanding of what speeds up and slows down the human aging process."
To create the clock, Horvath focused on methylation, a naturally occurring process that chemically alters DNA. Horvath sifted through 121 sets of data collected previously by researchers who had studied methylation in both healthy and cancerous human tissue.
Gleaning information from nearly 8,000 samples of 51 types of tissue and cells taken from throughout the body, Horvath charted how age affects DNA methylation levels from pre-birth through 101 years. To create the clock, he zeroed in on 353 markers that change with age and are present throughout the body.
Horvath tested the clock's effectiveness by comparing a tissue's biological age to its chronological age. When the clock repeatedly proved accurate, he was thrilled -- and a little stunned.
"It's surprising that one could develop a clock that reliably keeps time across the human anatomy," he admitted. "My approach really compared apples and oranges, or in this case, very different parts of the body: the brain, heart, lungs, liver, kidney and cartilage."
While most samples' biological ages matched their chronological ages, others diverged significantly. For example, Horvath discovered that a woman's breast tissue ages faster than the rest of her body.
"Healthy breast tissue is about two to three years older than the rest of a woman's body," said Horvath. "If a woman has breast cancer, the healthy tissue next to the tumor is an average of 12 years older than the rest of her body."
The results may explain why breast cancer is the most common cancer in women. Given that the clock ranked tumor tissue an average of 36 years older than healthy tissue, it could also explain why age is a major risk factor for many cancers in both genders.
Horvath next looked at pluripotent stem cells, adult cells that have been reprogrammed to an embryonic stem cell-like state, enabling them to form any type of cell in the body and continue dividing indefinitely.
"My research shows that all stem cells are newborns," he said. "More importantly, the process of transforming a person's cells into pluripotent stem cells resets the cells' clock to zero."
In principle, the discovery proves that scientists can rewind the body's biological clock and restore it to zero.
"The big question is whether the biological clock controls a process that leads to aging," Horvath said. "If so, the clock will become an important biomarker for studying new therapeutic approaches to keeping us young."
Finally, Horvath discovered that the clock's rate speeds up or slows down depending on a person's age.
"The clock's ticking rate isn't constant," he explained. "It ticks much faster when we're born and growing from children into teenagers, then slows to a constant rate when we reach 20."
In an unexpected finding, the cells of children with progeria, a genetic disorder that causes premature aging, appeared normal and reflected their true chronological age.
UCLA has filed a provisional patent on Horvath's clock. His next studies will examine whether stopping the body's aging clock halts the aging process--or increases cancer risk. He'll also explore whether a similar clock exists in mice
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Oct. 17, 2013 — Supermassive black holes: every large galaxy's got one. But here's a real conundrum: how did they grow so big?A paper in today's issue of Science pits the front-running ideas about the growth of supermassive black holes against observational data -- a limit on the strength of gravitational waves, obtained with CSIRO's Parkes radio telescope in eastern Australia.
"This is the first time we've been able to use information about gravitational waves to study another aspect of the Universe -- the growth of massive black holes," co-author Dr Ramesh Bhat from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) said.
"Black holes are almost impossible to observe directly, but armed with this powerful new tool we're in for some exciting times in astronomy. One model for how black holes grow has already been discounted, and now we're going to start looking at the others."
The study was jointly led by Dr Ryan Shannon, a Postdoctoral Fellow with CSIRO, and Mr Vikram Ravi, a PhD student co-supervised by the University of Melbourne and CSIRO.
Einstein predicted gravitational waves -- ripples in space-time, generated by massive bodies changing speed or direction, bodies like pairs of black holes orbiting each other.
When galaxies merge, their central black holes are doomed to meet. They first waltz together then enter a desperate embrace and merge.
"When the black holes get close to meeting they emit gravitational waves at just the frequency that we should be able to detect," Dr Bhat said.
Played out again and again across the Universe, such encounters create a background of gravitational waves, like the noise from a restless crowd.
Astronomers have been searching for gravitational waves with the Parkes radio telescope and a set of 20 small, spinning stars called pulsars.
Pulsars act as extremely precise clocks in space. The arrival time of their pulses on Earth are measured with exquisite precision, to within a tenth of a microsecond.
When the waves roll through an area of space-time, they temporarily swell or shrink the distances between objects in that region, altering the arrival time of the pulses on Earth.
The Parkes Pulsar Timing Array (PPTA), and an earlier collaboration between CSIRO and Swinburne University, together provide nearly 20 years worth of timing data. This isn't long enough to detect gravitational waves outright, but the team say they're now in the right ballpark.
"The PPTA results are showing us how low the background rate of gravitational waves is," said Dr Bhat.
"The strength of the gravitational wave background depends on how often supermassive black holes spiral together and merge, how massive they are, and how far away they are. So if the background is low, that puts a limit on one or more of those factors."
Armed with the PPTA data, the researchers tested four models of black-hole growth. They effectively ruled out black holes gaining mass only through mergers, but the other three models are still a possibility.
Dr Bhat also said the Curtin University-led Murchison Widefield Array (MWA) radio telescope will be used to support the PPTA project in the future.
"The MWA's large view of the sky can be exploited to observe many pulsars at once, adding valuable data to the PPTA project as well as collecting interesting information on pulsars and their properties," Dr Bhat said
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Thursday, 17 October 2013
Oct. 16, 2013 — Earth's most eminent emissary to Mars has just proven that those rare Martian visitors that sometimes drop in on Earth -- a.k.a. Martian meteorites -- really are from the Red Planet. A key new measurement of Mars' atmosphere by NASA's Curiosity rover provides the most definitive evidence yet of the origins of Mars meteorites while at the same time providing a way to rule out Martian origins of other meteorites.
The new measurement is a high-precision count of two forms of argon gas -- Argon-36 and Argon-38-accomplished by the Sample Analysis at Mars (SAM) instrument on Curiosity. These lighter and heavier forms, or isotopes, of argon exist naturally throughout the solar system. But on Mars the ratio of light to heavy argon is skewed because a lot of that planet's original atmosphere was lost to space, with the lighter form of argon being taken away more readily because it rises to the top of the atmosphere more easily and requires less energy to escape. That's left the Martian atmosphere relatively enriched in the heavier Argon-38.
Years of past analyses by Earth-bound scientists of gas bubbles trapped inside Martian meteorites had already narrowed the Martian argon ratio to between 3.6 and 4.5 (that is 3.6 to 4.5 atoms of Argon-36 to every one Argon-38) with the supposed Martian "atmospheric" value near four. Measurements by NASA's Viking landers in the 1970's put the Martian atmospheric ratio in the range of four to seven. The new SAM direct measurement on Mars now pins down the correct argon ratio at 4.2.
"We really nailed it," said Sushil Atreya of the University of Michigan, Ann Arbor, the lead author of a paper reporting the finding today inGeophysical Research Letters, a journal of the American Geophysical Union. "This direct reading from Mars settles the case with all Martian meteorites," he said.
One of the reasons scientists have been so interested in the argon ratio in Martian meteorites is that it was -- before Curiosity -- the best measure of how much atmosphere Mars has lost since the planet's earlier, wetter, warmer days billions of years ago. Figuring out the planet's atmospheric loss would enable scientists to better understand how Mars transformed from a once water-rich planet more like our own to the today's drier, colder and less hospitable world.
Had Mars held onto its entire atmosphere and its original argon, Atreya explained, its ratio of the gas would be the same as that of the Sun and Jupiter. They have so much gravity that isotopes can't preferentially escape, so their argon ratio -- which is 5.5 -- represents that of the primordial solar system.
While argon comprises only a tiny fraction of the gases lost to space from Mars, it is special because it's a noble gas. That means the gas is inert, not reacting with other elements or compounds, and therefore a more straightforward tracer of the history of the Martian atmosphere.
"Other isotopes measured by SAM on Curiosity also support the loss of atmosphere, but none so directly as argon," said Atreya. "Argon is the clearest signature of atmospheric loss because it's chemically inert and does not interact or exchange with the Martian surface or the interior. This was a key measurement that we wanted to carry out on SAM."
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Curiosity mission for NASA's Science Mission Directorate, Washington. The SAM investigation on the rover is managed by NASA Goddard Space Flight Center, Greenbelt, Md.
Oct. 16, 2013 — Researchers have discovered the earliest known complete nervous system exquisitely preserved in the fossilized remains of a never-before described creature that crawled or swam in the ocean 520 million years ago.Research led by University of Arizona Regents' Professor Nick Strausfeld and London Natural History Museum's Greg Edgecombe has revealed that the ancestors of chelicerates (spiders, scorpions and their kin) branched off from the family tree of other arthropods -- including insects, crustaceans and millipedes -- more than half a billion years ago.
The team discovered the earliest known complete nervous system exquisitely preserved in the fossilized remains of a never-before described creature that crawled or swam in the ocean 520 million years ago.
Described in the current issue of the journal Nature, the find belongs to an extinct group of marine arthropods known as megacheirans (Greek for "large claws") and solves the long-standing mystery of where this group fits in the tree of life.
"We now know that the megacheirans had central nervous systems very similar to today's horseshoe crabs and scorpions," said the senior author of the study, Nicholas Strausfeld, a Regents' Professor in the University of Arizona's department of neuroscience. "This means the ancestors of spiders and their kin lived side by side with the ancestors of crustaceans in the Lower Cambrian."
The scientists identified the 3-centimeter-long creature (a little over an inch) unearthed from the famous Chengjiang formation near Kunming in southwest China, as a representative of the extinct genus Alalcomenaeus. Animals in this group had an elongated, segmented body equipped with about a dozen pairs of body appendages enabling the animal to swim or crawl or both. All featured a pair of long, scissor-like appendages attached to the head, most likely for grasping or sensory purposes, which gave them their collective name, megacheirans.
Co-author Greg Edgecombe said that some paleontologists had used the external appearance of the so-called great appendage to infer that the megacheirans were related to chelicerates, based on the fact that the great appendage and the fangs of a spider or scorpion both have an "elbow joint" between their basal part and their pincer-like tip.
"However, this wasn't rock solid because others lined up the great appendage either a segment in front of spider fangs or one segment behind them," Edgecombe said. "We have now managed to add direct evidence from which segment the brain sends nerves into the great appendage. It's the second one, the same as in the fangs, or chelicerae. For the first time we can analyze how the segments of these fossil arthropods line up with each other the same way as we do with living species -- using their nervous systems."
The team analyzed the fossil by applying different imaging and image processing techniques, taking advantage of iron deposits that had selectively accumulated in the nervous system during fossilization.
To make the neural structures visible, the researchers used computed tomography (CT), a technique that reconstructs 3-D features within in the specimen. However, "the CT scan didn't show the outline of the nervous systems unambiguously enough," Strausfeld said, "while a scanning laser technique mapping the distribution of chemical elements showed iron deposits outlining the nervous system almost as convincingly but with minor differences."
Next, the group applied advanced imaging techniques to the scans, first overlaying the magenta color of the iron deposit scan with the green color of the CT scan, then subtracting the two.
"We discarded any image data that were not present in both scans," Strausfeld explained. "Where the two overlapped, the magenta and the green added to each other, revealing the preserved nervous system as a white structure, which we then inverted."
This resulted in what resembled a negative X-ray photograph of the fossil.
"The white structures now showed up as black," Strausfeld said, "and out popped this beautiful nervous system in startling detail."
Comparing the outline of the fossil nervous system to nervous systems of horseshoe crabs and scorpions left no doubt that 520-million year-old Alalcomenaeus was a member of the chelicerates.
Specifically, the fossil shows the typical hallmarks of the brains found in scorpions and spiders: Three clusters of nerve cells known as ganglia fused together as a brain also fused with some of the animal's body ganglia. This differs from crustaceans where ganglia are further apart and connected by long nerves, like the rungs of a rope ladder.
Other diagnostic features include the forward position of the gut opening in the brain and the arrangement of optic centers outside and inside the brain supplied by two pairs of eyes, just like in horseshoe crabs.
To make the analysis more robust, the researchers then added these features to an existing catalog of about 150 characteristics used in constructing evolutionary relationships among arthropods based on neuroanatomical features.
"Greg plugged these characteristics into a computer-based cladistic analysis to ask, 'where does this fossil appear in a relational tree?'" Strausfeld said. "Our fossil of Alalcomenaeus came out with the modern chelicerates."
But according to Strausfeld, the story doesn't end there.
"The prominent appendages that gave the megacheirans their name were clearly used for grasping and holding and probably for sensory inputs. The parts of the brain that provide the wiring for where these large appendages arise are very large in this fossil. Based on their location, we can now say that the biting mouthparts in spiders and their relatives evolved from these appendages."
Less than a year ago, the same research team published the discovery of a fossilized brain in the 520 million year-old fossilFuxianhuia protensa, showing unexpected similarity to the complex brain of a modern crustacean.
"Our new find is exciting because it shows that mandibulates (to which crustaceans belong) and chelicerates were already present as two distinct evolutionary trajectories 520 million years ago, which means their common ancestor must have existed much deeper in time," Strausfeld said. "We expect to find fossils of animals that have persisted from more ancient times, and I'm hopeful we will one day find the ancestral type of both the mandibulate and chelicerate nervous system ground patterns. They had to come from somewhere. Now the search is on."
For this research project, Strausfeld teamed up with Gengo Tanaka of the Japan Agency for Marine-Earth Science and Technology in Yokosuka, Japan; Xianguang Hou, director of the Yunnan Key Laboratory for Paleobiology at Yunnan University in Kunming, China, and his colleague Xiaoya Ma who is presently working with Gregory Edgecombe in the paleontology department of the Natural History Museum, London
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Oct. 16, 2013 — Astronomers at Queen's University Belfast have shed new light on the rarest and brightest exploding stars ever discovered in the universe.The research is published Oct. 17 inNature. It proposes that the brightest exploding stars, called super-luminous supernovae, are powered by magnetars -- small and incredibly dense neutron stars, with gigantic magnetic fields, that spin hundreds of times a second.
Scientists at Queen's Astrophysics Research Centre observed two super-luminous supernovae -- two of the Universe's brightest exploding stars -- for more than a year. Contrary to existing theories, which suggested that the brightest supernovae are caused by super-massive stars exploding, their findings suggest that their origins may be better explained by a type of explosion within the star's core which creates a smaller but extremely dense and rapidly spinning magnetic star.
Matt Nicholl, a research student at the Astrophysics Research Centre at Queen's School of Mathematics and Physics, is lead author of the study. He said: "Supernovae are several billions of times brighter than the Sun, and in fact are so bright that amateur astronomers regularly search for new ones in nearby galaxies. It has been known for decades that the heat and light from these supernovae come from powerful blast-waves and radioactive material.
"But recently some very unusual supernovae have been found, which are too bright to be explained in this way. They are hundreds of times brighter than those found over the last fifty years and the origin of their extreme properties is quite mysterious.
"Some theoretical physicists predicted these types of explosions came from the biggest stars in the universe destroying themselves in a manner quite like a giant thermonuclear bomb. But our data doesn't match up with this theory.
"In a supernova explosion, the star's outer layers are violently ejected, while its core collapses to form an extremely dense neutron star -- weighing as much as the Sun but only tens of kilometers across. We think that, in a small number of cases, the neutron star has a very strong magnetic field, and spins incredibly quickly -- about 300 times a second. As it slows down, it could transmit the spin energy into the supernova, via magnetism, making it much brighter than normal. The data we have seems to match that prediction almost exactly."
Queen's astronomers led an international team of scientists on the study, using some of the world's most powerful telescopes. Much of the data was collected using Pan-STARRS -- the Panoramic Survey Telescope and Rapid Response System. Based on Mount Haleakala in Hawaii, Pan-STARRS boasts the world's largest digital camera, and can cover an area 40 times the size of the full moon in one shot.
The study is one of the projects funded by a €2.3million grant from the European Research Council. The grant was awarded to Professor Stephen Smartt, Director of Queen's Astrophysics Research Centre, in 2012 to lead an international study to hunt for the Universe's earliest supernovae.
Professor Smartt said: "These are really special supernovae. Because they are so bright, we can use them as torches in the very distant Universe. Light travels through space at a fixed speed, as we look further away, we see snapshots of the increasingly distant past. By understanding the processes that result in these dazzling explosions, we can probe the Universe as it was shortly after its birth. Our goal is to find these supernovae in the early Universe, detecting some of the first stars ever to form and watch them produce the first chemical elements created in the Universe.
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Oct. 16, 2013 — Human fingertips have several types of sensory neurons that are responsible for relaying touch signals to the central nervous system. Scientists have long believed these neurons followed a linear path to the brain with a "labeled-lines" structure.But new research on mouse whiskers from Duke University reveals a surprise -- at the fine scale, the sensory system's wiring diagram doesn't have a set pattern. And it's probably the case that no two people's touch sensory systems are wired exactly the same at the detailed level, according to Fan Wang, Ph.D., an associate professor of neurobiology in the Duke Medical School.
The results, which appear online in Cell Reports, highlight a "one-to-many, many-to-one" nerve connectivity strategy. Single neurons send signals to multiple potential secondary neurons, just as signals from many neurons can converge onto a secondary neuron. Many such connections are likely formed by chance, Wang said. This connectivity scheme allows the touch system to have many possible combinations to encode a large repertoire of textures and forms.
"We take our sense of touch for granted," Wang said. "When you speak, you are not aware of the constant tactile feedback from your tongue and teeth. Without such feedback, you won't be able to say the words correctly. When you write with a pen, you're mostly unaware of the sensors telling you how to move it."
It's not feasible to visualize the touch pathways in the human brain at high resolutions. So, Wang and her collaborators from the University of Tsukuba in Japan and the Friedrich Miescher Institute for Biomedical Research in Switzerland used the whiskers of laboratory mice to map how distinct sensor neurons, presumably detecting different mechanical stimuli, are connected to signal the brain. When the sensory neurons are activated, they send the signal along an axon -- a long, slender nerve fiber than conducts electric impulses to the brain. The researchers traced signals running the long path from the mouse's whiskers to the brain.
Wang's group used a combination of genetic engineering and fluorescent tags delivered by viruses to color-code four different kinds of neurons and map their connections.
Earlier work by Wang and others had found that all of the 100 to 200 sensors associated with a single whisker project their axons to a large structure representing that whisker in the brain. Each whisker has its own neural representation structure.
"People have thought that within the large whisker-representing structure, there will be finer-scale, labeled lines," Wang said. "In other words, different touch sensors would send information through separate parallel pathways, into that large structure. But surprisingly, we did not find such organized pathways. Instead, we found a completely unorganized mosaic pattern of connections within the large structure. Information from different sensors is intermixed already at the first relay station inside the brain."
Wang said the next step will be to stimulate the labeled circuits in different ways to see how impulses travel the network.
"We want to figure out the exact functions and signals transmitted by different sensors during natural tactile behaviors and determine their exact roles on the perception of textures," she said
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