Welcome to the Saturday Science Edition of Overnight News Digest.
Astronomy
Black Hole Chokes On A Swallowed Star [...] On January 21, 2009, the ROTSE IIIb telescope at McDonald caught the flash of an extremely bright event. The telescope’s wide field of view takes pictures of large swathes of sky every night, looking for newly exploding stars as part of the ROTSE Supernova Verification Project (RSVP). Software then compares successive photos to find bright “new” objects in the sky — transient events like the explosion of a star or a gamma-ray burst. With a magnitude of –22.5, this 2009 event was as bright as the “superluminous supernovae” — a new category of the brightest stellar explosions known — that the ROTSE team discovered at McDonald in recent years. The team nicknamed the 2009 event “Dougie,” after a character in the cartoon South Park — its technical name is ROTSE3 J120847.9+430121. The team thought Dougie might be a supernova and set about looking for its host galaxy, which would be much too faint for ROTSE to see. They found that the Sloan Digital Sky Survey had mapped a faint red galaxy at Dougie’s location. The team followed that up with new observations of the galaxy with one of the giant Keck telescopes in Hawaii, pinpointing the galaxy’s distance at 3 billion light-years. These deductions meant Dougie had a home — but just what was he? Team members had four possibilities: a superluminous supernova; a merger of two neutron stars; a gamma-ray burst; or a “tidal disruption event” — a star being pulled apart as it neared its host galaxy’s central black hole. To narrow it down, they studied Dougie in various ways. They made ultraviolet observations with the orbiting Swift telescope and took many spectra from the ground with the 9.2-meter Hobby-Eberly Telescope at McDonald. Finally, they used computer models of how the light from different possible physical processes that might explain how Dougie would behave — how it varies in brightness over time and what chemical signatures it might show — and compared them to Dougie’s actual behavior. In detail, Dougie did not look like a supernova. The neutron star merger and gamma-ray burst possibilities were similarly eliminated. “When we discovered this new object, it looked similar to supernovae we had known already,” said lead author Jozsef Vinko of the University of Szeged in Hungary. “But when we kept monitoring its light variation, we realized that this was something nobody really saw before. Finding out that it was probably a supermassive black hole eating a star was a fascinating experience.” astronomy
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Planck: Gravitational Waves Remain Elusive Despite earlier reports of a possible detection, a joint analysis of data from ESA’s Planck satellite and the ground-based BICEP2 and Keck Array experiments has found no conclusive evidence of primordial gravitational waves. The Universe began about 13.8 billion years ago and evolved from an extremely hot, dense and uniform state to the rich and complex cosmos of galaxies, stars and planets we see today. An extraordinary source of information about the Universe’s history is the Cosmic Microwave Background, or CMB, the legacy of light emitted only 380 000 years after the Big Bang. ESA’s Planck satellite observed this background across the whole sky with unprecedented accuracy, and a broad variety of new findings about the early Universe has already been revealed over the past two years. But astronomers are still digging ever deeper in the hope of exploring even further back in time: they are searching for a particular signature of cosmic ‘inflation’ – a very brief accelerated expansion that, according to current theory, the Universe experienced when it was only the tiniest fraction of a second old. [...] The BICEP2 team presented evidence favouring the interpretation that this signal originated in primordial gravitational waves, sparking an enormous response in the academic community and general public. However, there is another contender in this game that can produce a similar effect: interstellar dust in our Galaxy, the Milky Way. europeanspaceagency
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Meteorite May Represent ‘Bulk Background’ Of Mars’ Battered Crust NWA 7034, a meteorite found a few years ago in the Moroccan desert, is like no other rock ever found on Earth. It’s been shown to be a 4.4 billion-year-old chunk of the Martian crust, and according to a new analysis, rocks just like it may cover vast swaths of Mars. In a new paper, scientists report that spectroscopic measurements of the meteorite are a spot-on match with orbital measurements of the Martian dark plains, areas where the planet’s coating of red dust is thin and the rocks beneath are exposed. The findings suggest that the meteorite, nicknamed Black Beauty, is representative of the “bulk background” of rocks on the Martian surface, says Kevin Cannon, a Brown University graduate student and lead author of the new paper. [...] When scientists started analyzing Black Beauty in 2011, they knew they had something special. Its chemical makeup confirmed that it was a castaway from Mars, but it was unlike any Martian meteorite ever found. Before Black Beauty, all the Martian rocks found on Earth were classified as SNC meteorites (shergottites, nakhlites, or chassignites). They’re mainly igneous rocks made of cooled volcanic material. But Black Beauty is a breccia, a mashup of different rock types welded together in a basaltic matrix. It contains sedimentary components that match the chemical makeup of rocks analyzed by the Mars rovers. Scientists concluded that it is a piece of Martian crust — the first such sample to make it to Earth. [...] “This is showing that if you went to Mars and picked up a chunk of crust, you’d expect it to be heavily beat up, battered, broken apart and put back together,” Cannon said. [...] “Mars is punctured by over 400,000 impact craters greater than 1 km in diameter ...,” they write. “Because brecciation is a natural consequence of impacts, it is expected that material similar to NWA 7034 has accumulated on Mars over time.” brown.edu
Biology
Feather-Legged Lace Weaver Gives Unique Insights Into How To Spin Nano-Fibers Instead of using sticky blobs of glue on their threads to capture prey, Uloborus plumipes (also known as the feather-legged lace weaver) spiders use a more ancient technique – dry capture threads made of thousands of nano-scale filaments that it is thought to electrically charge to create these fluffed-up catching ropes. To discover the secrets of Uloborus plumipes’ nano-fibers, Oxford University scientists Dr Katrin Kronenberger and Prof Fritz Vollrath collected adult female from garden centers in Hampshire, UK. They then took photographs and videos of the spiders’ spinning action and used three different microscopy techniques to examine the spiders’ silk-generating organs. Of particular interest was the cribellum, an ancient spinning organ not found in many spiders and consisting of one or two plates densely covered in tiny silk outlet nozzles.
“Uloborus plumipes has unique cribellar glands, amongst the smallest silk glands of any spider, and it’s these that yield the ultra-fine catching wool of its prey capture thread,” said Dr Kronenberger, the first author of a paper published in the journal Biology Letters. “The raw material, silk dope, is funneled through exceptionally narrow and long ducts into tiny spinning nozzles or spigots. Importantly, the silk seems to form only just before it emerges at the uniquely-shaped spigots of this spider.”
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“The swathe of gossamer, made of thousands of filaments, emerging from these spigots is actively combed out by the spider onto the capture thread’s core fibers using specialist hairs on its hind legs,” Prof Vollrath said. “This combing and hackling – violently pulling the thread – charges the fibers and the electrostatic interaction of this combination spinning process leads to regularly spaced, wool-like puffs covering the capture threads.”
sci-news
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The Neuroscience of Lucid Dreams Lucid dreams are perhaps the most bizarre perceptual experience one can have. You are asleep and dreaming, but suddenly you realize that it’s all just a dream. At that point, you can choose to wake up (I usually do… I don’t think I’ve ever had a lucid dream that wasn’t a nightmare) or you can continue to dream on, with one important advantage. You’re now aware that the world around you is completely made up by your brain. As with the post-awakening of Neo in the movie “The Matrix”, you can bend the physical laws to your liking. You can fly, stop bullets with your bare hands, or even deliver magical punches to the bad guys to make them shrink in size (yeah, I have weird dreams). There is no spoon. [...] A recent study, published earlier this month in the Journal of Neuroscience, set out to determine if people with high and low dream lucidity were also dissimilar in their metacognitive ability, that is, the ability to reflect on, and report, one’s mental states. The study participants completed questionnaires that assessed their lucid dreaming frequency, intensity, and degree of control, and also their metacognitive skills, including their self-reflection and self-consciousness. The experimental subjects moreover underwent brain imaging while conducting a thought monitoring task. This consisted of two 11-minute runs during which the subjects had to evaluate the each and every thought that entered their heads on an externally-internally oriented scale. Externally oriented thoughts meant thoughts related to the external environment, such as the visual surroundings, or the noise from the scanner. Internally oriented thoughts were not related to the immediate environment, such as remembering past events or planning for the day ahead. The research showed that the brains of people with high and low dream lucidity were different. Subjects with high lucidity had greater gray matter volume in the frontopolar cortex, compared to those with low lucidity. This brain region also showed higher activity during thought monitoring in both high- and low-lucidity subjects, with stronger increases in the high-lucidity group. The scientists concluded that lucid dreaming and metacognition share some underlying mechanisms, particularly with regards to thought monitoring. This relationship had been previously suspected, but never before explored at the neural level. Future research may tell us if it’s possible to control the frequency and contents of our lucid dreaming by training ourselves to monitor our thoughts while we’re awake. I, for one, would love some lucid dreams that don’t involve Freddy Krueger every now and then. scientificamerican
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HIV Testing Yields Diagnoses In Kenya But Few Seek Care Between December 2009 and February 2011, health workers with the AMPATH Consortium sought to test and counsel every adult resident in the Bunyala subcounty of Kenya for HIV. A study in the journal Lancet HIV reports that the campaign yielded more than 1,300 new positive diagnoses, but few of those new patients sought health care. "Home-based counseling and testing (HBCT) provided a diagnosis to nearly 40 percent of people living with HIV in this subcounty who otherwise most likely would not have gone for HIV testing," said study lead author Becky Genberg, assistant professor (research) of health services, policy and practice in the Brown University School of Public Health. "They therefore would not have known about their HIV infection and not had the opportunity to change their behavior to protect others." AMPATH's HBCT program is part of a strategy to identify all individuals living with HIV in the catchment area, start them on antiretroviral medication as soon as possible, and help them stay on their medications. Antiretroviral medication not only suppresses HIV infections for most patients but also reduces their ability to transmit the virus. [...] A major finding of the study is that three years later only 15 percent of the newly diagnosed people had engaged in care for their infection. A likely reason why, Genberg said, is that newly diagnosed people typically don't yet feel sick.
"That so few linked to care following HBCT is a call for innovative and creative strategies to work alongside HBCT to support the mostly healthy, asymptomatic newly diagnosed to engage with care in a way that is meaningful for them," Genberg said. [...] "Unless paired with interventions targeted at hard-to-reach populations, the diagnosing of undiagnosed individuals in many settings will not be cost-effective and will have little effect on individual and population viral suppression," she and colleagues wrote.
biologynews
Chemistry
New Tracers Can Identify Coal Ash Contamination In Water "These new tools can be used by federal and state regulatory agencies to monitor the environmental effects of coal ash and determine whether it has or hasn't impacted the environment," said Avner Vengosh, professor of geochemistry and water quality at Duke's Nicholas School of the Environment. "They can be used to trace the coal ash effluents to their source, even in watersheds where there are multiple possible sources of contamination." Previous methods to identify coal ash contaminants in the environment were based solely on the contaminants' chemical variations, he said. The newly developed tracers provide additional forensic fingerprints that give regulators a more accurate and systematic tool. The tracers, which have been tested both in the laboratory and the field, are based on the distinctive isotopic and geochemical signatures of two elements, boron and strontium, found in coal ash effluent. "The isotopic signature of boron coming from coal ash is always different from naturally occurring boron or boron from other sources," said Laura S. Ruhl, assistant professor of earth sciences at the University of Arkansas at Little Rock. "The signature of strontium is not always distinct, but when used together, the two tracers provide definitive evidence if the contamination is coming from coal ash or another source." chemistrytimes
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Why This Popular Chemistry Experiment Is A Blast Explosions are fun—ask any budding chemistry student. That’s why dropping a chunk of pure sodium into water is a classic classroom demonstration. The resulting violent reaction can produce impressive flames and a loud bang. Although the basic chemistry of the popular experiment has long been understood, the details were not. Now, scientists have captured the action using high-speed video cameras and discovered an unexpected trigger. Less than a millisecond after sodium and water meet, the sodium contorts into a sea urchin–like shape, growing spikes that shoot out into the water and initiate a runaway reaction. Sodium is one of the alkali metals, a group of famously reactive elements. Because sodium is so reactive, it is rare in its pure form, which is solid at room temperature but soft enough to cut with a knife. The sodium we’re most familiar with, in table salt, is stable because it’s bound to chloride. Pure alkali metals are a different story: When they get together with water, they erupt furiously. A flurry of electrons abandons the metal, interacting with the water to form hydrogen gas and other byproducts. The reaction generates heat, which melts the sodium, and because hydrogen gas is flammable, it ignites. Or so the story goes. But scientists led by chemist Pavel Jungwirth of the Academy of Sciences of the Czech Republic in Prague weren’t satisfied. “There was a missing piece in this explanation,” Jungwirth says. To produce an explosion, the chemicals involved need to be well mixed so that the reaction snowballs instead of sputtering out. But because only the surface of the sodium chunk contacts water, only atoms in its outer layer can react. Moreover, the production of hydrogen gas creates a layer that separates the sodium and the water, which should further slow the reaction, resulting in slow bubbling rather than a kaboom. To study the details of the detonation, Jungwirth and colleagues first had to tame the reaction. The results of the demonstration are unpredictable—sometimes it flashes and sometimes it fizzles, depending on small variations in the size and shape of the chunks of sodium used. So the scientists used a liquid mixture of sodium and another alkali metal, potassium, which they could slowly drip into water in drops of a uniform size and shape. They arranged high-speed video cameras to capture the reaction at thousands of frames per second. Then they donned protective gear and stood back. The cameras captured a never-before-seen effect. Less than a millisecond after the reaction begins, tens to hundreds of spiky metal protrusions pierce the water, the researchers report online today in Nature Chemistry. The spikes appear, the researchers deduced, because when electrons flee the metal for water, an intense positive charge builds up. The mutual repulsion of those positive charges rips the metal apart, and it blasts outward in tiny needles. This increases the surface area of the metal in contact with water, generating a vigorous reaction. Computer simulations performed by the researchers confirmed this effect, although for much smaller quantities of sodium due to the limits of computing power. sciencemag
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New Method Allows For Greater Variation In Band Gap Tunability If you can't find the ideal material, then design a new one. Northwestern University's James Rondinelli uses quantum mechanical calculations to predict and design the properties of new materials by working at the atom-level. His group's latest achievement is the discovery of a novel way to control the electronic band gap in complex oxide materials without changing the material's overall composition. The finding could potentially lead to better electro-optical devices, such as lasers, and new energy-generation and conversion materials, including more absorbent solar cells and the improved conversion of sunlight into chemical fuels through photoelectrocatalysis. "There really aren't any perfect materials to collect the sun's light," said Rondinelli, assistant professor of materials science and engineering in the McCormick School of Engineering. "So, as materials scientists, we're trying to engineer one from the bottom up. We try to understand the structure of a material, the manner in which the atoms are arranged, and how that 'genome' supports a material's properties and functionality." The electronic band gap is a fundamental material parameter required for controlling light harvesting, conversion, and transport technologies. Via band-gap engineering, scientists can change what portion of the solar spectrum can be absorbed by a solar cell, which requires changing the structure or chemistry of the material. Current tuning methods in non-oxide semiconductors are only able to change the band gap by approximately one electronvolt, which still requires the material's chemical composition to become altered. Rondinelli's method can change the band gap by up to 200 percent without modifying the material's chemistry. The naturally occurring layers contained in complex oxide materials inspired his team to investigate how to control the layers. They found that by controlling the interactions between neutral and electrically charged planes of atoms in the oxide, they could achieve much greater variation in electronic band gap tunability. "You could actually cleave the crystal and, at the nanometer scale, see well-defined layers that comprise the structure," he said. "The way in which you order the cations on these layers in the structure at the atomic level is what gives you a new control parameter that doesn't exist normally in traditional semiconductor materials." sciencedaily
Earth Science
EPA Chief Meets With Vatican Officials Ahead Of Papal Encyclical The head of the U.S. Environmental Protection Agency met Friday with Vatican officials who helped draft Pope Francis' upcoming encyclical on ecology, evidence that the Obama administration is seeking to hitch its climate-change message onto that of the popular pope. EPA Administrator Gina McCarthy told reporters that her aim in visiting was to show the Vatican how aligned President Barack Obama and Francis are on climate change. "I think the most important thing that we can do, working with the pope, is to try to remind ourselves that this is really about protecting natural resources that human beings rely on, and that those folks that are most vulnerable — that the church has always been focused on, those in poverty and low income — are the first that are going to be hit and impacted by a changing climate," she said. While Pope Benedict XVI introduced solar energy to the Vatican and joined a reforestation project aimed at offsetting the Vatican's CO2 emissions, Francis has caught the world's attention for environmentalism, and his upcoming encyclical has drawn more speculation than any papal document in memory. During his recent Asia trip, Francis asserted that climate change is real and that human activity is "mostly" to blame. nbcnews
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Decline Of England's Natural Environment 'Hits Economy' England's natural environment is in decline and its deterioration is harming the economy, an independent advisory group has told the government. The Natural Capital Committee says pressures will rise with population growth and has called for a 25-year investment plan. [...] The report said air pollution reduces productivity and also causes some 40,000 premature deaths each year. It also called for investment in urban green areas to improve physical and mental health for those living in cities. The report calculates that health costs can be reduced by cleaning up dirty air; floods can be tempered by creating new wetlands; and better green spaces in cities can tempt people outdoors to improve their physical and mental well-being. The NCC puts numbers on the benefits of environmental investment. It says planting woods near cities of up to 250,000 additional hectares can generate a benefit to society of £500m per annum as people exercise and enjoy nature. bbc
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Southern California's Water Supply Threatened By Next Major Quake Southern California gets the vast majority of its water from four aqueducts that flow from the north, but all of them cross the San Andreas Fault. That means millions of people are just one major earthquake away from drying out for a year or more. "It's a really concerning issue for the city of Los Angeles," says Craig Davis, an engineer with the LA Department of Water and Power, which oversees the LA aqueduct. Research shows that a magnitude 7.8 quake on the San Andreas Fault could sever all four aqueducts at once, cutting off more than 70 percent of the water sustaining Southern California. "Which is, depending on what counties you look at ... somewhere in the order of 18 and 22 million people," Davis says. "That's a very large number." npr
Physics
How To Twist Light Into A Möbius Strip Möbius strips can easily be made at home – just take a strip of paper, give it a half-twist and then join its ends together. Trivial as it may sound, this loop possesses the unusual property of having only one surface and one edge. They also appear very rarely in nature and had never before been seen in light. Now, an international group of physicists has created such shapes using the polarization of laser light, and the researchers say that these electromagnetic patterns could be used to build new kinds of small-scale structure such as metamaterials. The possibility of making an optical Möbius strip was suggested in 2005 by Isaac Freund of Bar-Ilan University in Israel. Freund calculated that a pair of laser beams could be manipulated such that the axis along which their combined electric fields oscillates – the polarization vector – would trace out a Möbius strip. He proposed using beams with different spin and orbital angular momenta, and making them interfere at specific angles to one another. The spin – or circular polarization – of an electromagnetic wave involves its polarization rotating clockwise or anticlockwise in a circle that is normal to the direction of propagation. Orbital angular momentum, on the other hand, comes from the twisting of a beam's wavefront around its propagation axis. Longitudinal challenge Normally, a light wave vibrates in a plane at right angles to its direction of travel; but crucial to creating a 3D optical pattern such as a Möbius strip is to ensure that it also has a longitudinal component along the propagation axis. It turns out that Freund's proposal for creating this longitudinal component is extremely challenging from an experimental point of view, so in this latest work Peter Banzer of the Max Planck Institute for the Science of Light in Erlangen and colleagues in Germany, Canada, Italy and the US have taken a different approach. Banzer and colleagues used a liquid-crystal device known as a q-plate. When exposed to a beam with a certain spin, a q-plate transforms that beam so that it has opposite spin and 2q units of orbital angular momentum, where q can be any half-integer value and is a property of the particular plate used. The team used a green laser beam that was a superposition of two waves with opposing spin. The result was a beam with a polarization that varied across its width. It was circularly polarized at its centre, but linearly polarized – and with varying orientations of the polarization vector – further out. physicsworld
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Underwater Acoustic Signatures Of Glacier Calving Abstract Climate-driven ice-water interactions in the contact zone between marine-terminating glaciers and the ocean surface show a dynamic and complex nature. Tidewater glaciers lose volume through the poorly-understood process of calving. A detailed description of the mechanisms controlling the course of calving is essential for the reliable estimation and prediction of mass loss from glaciers. Here we present the potential of hydroacoustic methods to investigate different modes of ice detachments. High-frequency underwater ambient noise recordings are combined with synchronized, high-resolution, time-lapse photography of the Hans Glacier cliff in Hornsund Fjord, Spitsbergen to identify three types of calving events: typical subaerial, sliding subaerial and submarine. A quantitative analysis of the data reveals a robust correlation between ice impact energy and acoustic emission at frequencies below 200 Hz for subaerial calving. We suggest that relatively inexpensive acoustic methods can be successfully used to provide quantitative descriptions of the various calving types. wiley
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Nobel Laureate Charles Townes, Laser Co-Creator, Dies At 99 Charles H. Townes, the Nobel Prize-winning physicist who helped create the laser that would revolutionize everything from medicine to manufacturing, has died. He was 99. Townes had been in poor health before his death on the way to an Oakland hospital Tuesday, officials at the University of California, Berkeley, said. "Charlie Townes had an enormous impact on physics and society in general," Steven Boggs, the chairman of the physics department at Berkeley, said Wednesday. The invention he's known for paved the way for other scientific discoveries, but also has a huge array of applications today: DVD players, gun sights, printers, computer networks, metal cutters, tattoo removal and vision correction are just some of the tools and technologies that rely on lasers. "I realized there would be many applications for the laser," Townes told Esquire magazine in 2001, "but it never occurred to me we'd get such power from it." phys.org