Sunday, 29 December 2013
Jan. 8, 2013 — Newly released NASA Hubble Space Telescope images of a vast debris disk encircling the nearby star Fomalhaut and a mysterious planet circling it may provide forensic evidence of a titanic planetary disruption in the system.Astronomers are surprised to find the debris belt is wider than previously known, spanning a section of space from 14 to nearly 20 billion miles from the star. Even more surprisingly, the latest Hubble images have allowed a team of astronomers to calculate the planet follows an unusual elliptical orbit that carries it on a potentially destructive path through the vast dust ring.
The planet, called Fomalhaut b, swings as close to its star as 4.6 billion miles, and the outermost point of its orbit is 27 billion miles away from the star. The orbit was recalculated from the newest Hubble observation made last year.
"We are shocked. This is not what we expected," said Paul Kalas of the University of California at Berkeley and the SETI Institute in Mountain View, Calif.
The Fomalhaut team led by Kalas considers this circumstantial evidence there may be other planet-like bodies in the system that gravitationally disturbed Fomalhaut b to place it in such a highly eccentric orbit. The team presented its finding Tuesday at the 221st meeting of the American Astronomical Society in Long Beach, Calif.
Among several scenarios to explain Fomalhaut b's 2,000-year-long orbit is the hypothesis that an as yet undiscovered planet gravitationally ejected Fomalhaut b from a position closer to the star, and sent it flying in an orbit that extends beyond the dust belt.
"Hot Jupiters get tossed through scattering events, where one planet goes in and one gets thrown out," said co-investigator Mark Clampin of NASA's Goddard Space Flight Center in Greenbelt, Md. "This could be the planet that gets thrown out."
Hubble also found the dust and ice belt encircling the star Fomalhaut has an apparent gap slicing across the belt. This might have been carved by another undetected planet. Hubble's exquisite view of the dust belt shows irregularities that strongly motivate a search for other planets in the system.
If its orbit lies in the same plane with the dust belt, then Fomalhaut b will intersect the belt around 2032 on the outbound leg of its orbit. During the crossing, icy and rocky debris in the belt could crash into the planet's atmosphere and create the type of cosmic fireworks seen when Comet Shoemaker-Levy 9 crashed into Jupiter. Most of the fireworks from collisions will be seen in infrared light. However, if Fomalhaut b is not co-planar with the belt, the only thing to be seen will be a gradual dimming of Fomalhaut b as it travels farther from the star.
Kalas hypothesized that Fomalhaut b's extreme orbit is a major clue in explaining why the planet is unusually bright in visible light, but very dim in infrared light. It is possible the planet's optical brightness originates from a ring or shroud of dust around the planet, which reflects starlight. The dust would be rapidly produced by satellites orbiting the planet, which would suffer extreme erosion by impacts and gravitational stirring when Fomalhaut b enters into the planetary system after a millennium of deep freeze beyond the main belt. An analogy can be found by looking at Saturn, which has a tenuous, but very large dust ring produced when meteoroids hit the outer moon Phoebe.
The team has also considered a different scenario where a hypothetical second dwarf planet suffered a catastrophic collision with Fomalhaut b. The collision scenario would explain why the star Fomalhaut has a narrow outer belt linked to an extreme planet. But in this case the belt is young, less than 10,000 years old, and it is difficult to produce energetic collisions far from the star in such young systems.
Fomalhaut is a special system because it looks like scientists may have a snapshot of what our solar system was doing 4 billion years ago. The planetary architecture is being redrawn, the comet belts are evolving, and planets may be gaining and losing their moons. Astronomers will continue monitoring Fomalhaut b for decades to come because they may have a chance to observe a planet entering an icy debris belt that is like the Kuiper Belt at the fringe of our own solar system
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Dec. 18, 2013 — The nearby star Fomalhaut A hosts the most famous planetary system outside our own Solar System, containing both an exoplanet and a spectacular ring of comets. Today, an international team of astronomers announced a new discovery with the Herschel Space Observatory that has made this system even more intriguing; the least massive star of the three in the Fomalhaut system, Fomalhaut C, has now been found to host its own comet belt. The researchers published their results today in a letter to the journal Monthly Notices of the Royal Astronomical Society.Fomalhaut A is one of the brightest stars in the sky. Located 25 light years away in the constellation of Piscis Austrinus, it shines with a blue-white colour and is prominent from the southern hemisphere. From northern latitudes it appears low down in the south during autumn evenings. In contrast, Fomalhaut C, also named LP 876-10, is a dim red dwarf star invisible without a telescope, and was only found to be part of the Fomalhaut system in October this year.
Fomalhaut A's prominence made it a key target for the Hubble Space Telescope, which astronomers used to find the ring of comets, hints of and then a direct image of the planet, Fomalhaut b, in 2008 (astronomers use uppercase letters for stars, and lowercase letters are used for planets, so 'Fomalhaut b' is a planet, and 'Fomalhaut B' is the second star in the system).
The new discovery might hold the key to some of the mysteries of the Fomalhaut system. The lead author Grant Kennedy, an astronomer at the Institute of Astronomy at the University of Cambridge, said, "It's very rare to find two comet belts in one system, and with the two stars 2.5 light years apart this is one of the most widely separated star systems we know of. It made us wonder why both Fomalhaut A and C have comet belts, and whether the belts are related in some way." To get a feeling for how far 2.5 light years is, light from the Sun takes only 8 minutes to get to the Earth, and 5.5 hours to get to Pluto, and the nearest star to the Sun, Proxima Centauri, is only 4 light years away.
This discovery may help solve the major mystery in the Fomalhaut system: the orbits of the comet ring and planet around Fomalhaut A are elliptical (which simply means that the orbits aren't circular). The elliptical orbits are thought to be the result of close encounters with something else in the system, perhaps with another as yet undetected planet or perhaps with one of the two other stars, B or C.
The discovery of the comet belt around C is important because such encounters can not only make the comet belts elliptical, they can also make them brighter by causing the comets to collide more often, releasing massive amounts of dust and ice. Stars are rarely seen to have such bright comet belts, so their detection around both A and C suggests that they may have had their brightnesses enhanced by a previous close encounter between the two.
Paul Kalas of the University of California discovered the orbits are elliptical and is involved in the new work. He said, "We thought that the Fomalhaut A system was disturbed by a planet on the inside -- but now it looks like a small star from the outside could also influence the system. A good test of this hypothesis is to measure the red dwarf's exact orbit over the next few years."
The stellar interaction scenario isn't as unusual as it sounds. Comet ISON, which disintegrated following a close encounter with our Sun at the end of November, may have been put on a Sun-grazing orbit by a star that passed near to the Solar System in the past. Similarly, the proposed encounters between the stars in the Fomalhaut system may have sent a few comets onto star-grazing orbits. You might imagine that if there were any habitable planets around Fomalhaut A or C, their inhabitants might be luckier than us and see truly spectacular comet shows in their night sky.
The Herschel Observatory, which observed the Universe in infrared light ran out of helium coolant and stopped observing in April this year. This was seven months before Fomalhaut C was identified as part of the triple star system, but fortunately the telescope had imaged it back in 2011, so the astronomers have plenty of data on it already.
Kennedy has actually known about the comet belt for several years; "Over the last few years we used Herschel to look for comet belts around many stars within a few hundred light years of the Sun. At that stage Fomalhaut C was just called LP 876-10 and we thought it was a lone red dwarf with a comet belt. It was interesting because such discoveries are very rare, but didn't tell us why it was there. After the discovery that this star was part of the Fomalhaut system, the existence of its comet belt made us think harder about connections between the two stars, and it may be that it helps solve the mystery of the elliptical comet belt around Fomalhaut A."
Kennedy and his team are now trying to check the stellar encounter idea with computer simulations and more detailed observations of the Fomalhaut C belt. The apparent absence of a belt around Fomalhaut B remains a mystery. But if the simulations are in line with what the astronomers see, then this would be a 'smoking gun' for a stellar interaction and proof that other stars can affect how planetary systems form and evolve
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Dec. 20, 2013 — Massive stars -- those at least 8 times the mass of our Sun -- present an intriguing mystery: how do they grow so large when the vast majority of stars in the Milky Way are considerably smaller?To find the answer, astronomers used the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to survey the cores of some of the darkest, coldest, and densest clouds in our Galaxy to search for the telltale signs of star formation.
These objects, known as Infrared Dark Clouds, were observed approximately 10,000 light-years away in the direction of the constellations of Aquila and Scutum.
Since these cloud cores are so massive and dense, gravity should have already overwhelmed their supporting gas pressure, allowing them to collapse to form new, Sun-mass stars. If a star had not yet begun to shine, that would be a hint that something extra was supporting the cloud.
"A starless core would indicate that some force was balancing out the pull of gravity, regulating star formation, and allowing vast amounts of material to accumulate in a scaled-up version of the way our own Sun formed," remarked Jonathan Tan, an astrophysicist at the University of Florida, Gainesville, and lead author of a paper published today in the Astrophysical Journal."This suggests that massive stars and Sun-like stars follow a universal mechanism for star formation. The only difference is the size of their parent clouds."
Average stars like our Sun begin life as dense, but relatively low-mass concentrations of hydrogen, helium, and other trace elements inside large molecular clouds. After the initial kernel emerges from the surrounding gas, material collapses under gravity into the central region in a relatively ordered fashion via a swirling accretion disk, where eventually planets can form. After enough mass accumulates, nuclear fusion begins at the core and a star is born.
While this model of star formation can account for the vast majority of stars in our Milky Way, something extra is needed to explain the formation of more massive stars. "Some additional force is needed to balance out the normal process of collapse, otherwise our Galaxy would have a fairly uniform stellar population," said Tan. "Alternatively, there has been speculation that two separate models of star formation are needed: one for Sun-like stars and one for these massive stars."
The key to teasing out the answer is to find examples of massive starless cores -- to witness the very beginnings of massive star birth.
The team of astronomers from the United States, the United Kingdom, and Italy used ALMA to look inside these cores for a unique chemical signature involving the isotope deuterium to essentially take the temperatures of these clouds to see if stars had formed. Deuterium is important because it tends to bond with certain molecules in cold conditions. Once stars turn on and heat the surrounding gas, the deuterium is quickly lost and replaced with the more common isotope of hydrogen.
The ALMA observations detected copious amounts of deuterium, suggesting that the cloud is cold and starless. This would indicate that some counter force is forestalling core collapse and buying enough time to form a massive star. The researchers speculate that strong magnetic fields may be propping up the cloud, preventing it from collapsing quickly.
"These new ALMA observations reveal objects that are quite similar to the nurseries of Sun-like stars, but simply scaled-up by tens or a hundred times. This may mean that nature is more important than nurture when it comes to determining a star's size," concludes Tan.
These observations were conducted during ALMA's early science campaign. Future studies with ALMA's full array of 66 antennas will uncover even more details about these star-forming regions.
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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Dec. 19, 2013 — Cranial surgery is tricky business, even under 21st-century conditions (think aseptic environment, specialized surgical instruments and copious amounts of pain medication both during and afterward).However, evidence shows that healers in Peru practiced trepanation -- a surgical procedure that involves removing a section of the cranial vault using a hand drill or a scraping tool -- more than 1,000 years ago to treat a variety of ailments, from head injuries to heartsickness. And they did so without the benefit of the aforementioned medical advances.
Excavating burial caves in the south-central Andean province of Andahuaylas in Peru, UC Santa Barbara bioarchaeologist Danielle Kurin and her research team unearthed the remains of 32 individuals that date back to the Late Intermediate Period (ca. AD 1000-1250). Among them, 45 separate trepanation procedures were in evidence. Kurin's findings appear in the current issue of the American Journal of Physical Anthropology.
"When you get a knock on the head that causes your brain to swell dangerously, or you have some kind of neurological, spiritual or psychosomatic illness, drilling a hole in the head becomes a reasonable thing to do," said Kurin, a visiting assistant professor in the Department of Anthropology at UCSB and a specialist in forensic anthropology.
According to Kurin, trepanations first appeared in the south-central Andean highlands during the Early Intermediate Period (ca. AD 200-600), although the technique was not universally practiced. Still, it was considered a viable medical procedure until the Spanish put the kibosh on the practice in the early 16th century.
But Kurin wanted to know how trepanation came to exist in the first place. And she looked to a failed empire to find some answers.
"For about 400 years, from 600 to 1000 AD, the area where I work -- the Andahuaylas -- was living as a prosperous province within an enigmatic empire known as the Wari," she said. "For reasons still unknown, the empire suddenly collapsed." And the collapse of civilization, she noted, brings a lot of problems.
"But it is precisely during times of collapse that we see people's resilience and moxie coming to the fore," Kurin continued. "In the same way that new types of bullet wounds from the Civil War resulted in the development of better glass eyes, the same way IED's are propelling research in prosthetics in the military today, so, too, did these people in Peru employ trepanation to cope with new challenges like violence, disease and deprivation 1,000 years ago."
Kurin's research shows various cutting practices and techniques being employed by practitioners around the same time. Some used scraping, others used cutting and still others made use of a hand drill. "It looks like they were trying different techniques, the same way we might try new medical procedures today," she said. "They're experimenting with different ways of cutting into the skull."
Sometimes they were successful and the patient recovered, and sometimes things didn't go so well. "We can tell a trepanation is healed because we see these finger-like projections of bone that are growing," Kurin explained. "We have several cases where someone suffered a head fracture and were treated with the surgery; in many cases, both the original wound and the trepanation healed." It could take several years for the bone to regrow, and in a subset of those, a trepanation hole in the patient's head might remain for the rest of his life, thereby conferring upon him a new "survivor" identity.
When a patient didn't survive, his skull (almost never hers, as the practice of trepanation on women and children was forbidden in this region) might have been donated to science, so to speak, and used for education purposes. "The idea with this surgery is to go all the way through the bone, but not touch the brain," said Kurin. "That takes incredible skill and practice.
"As bioarchaeologists, we can tell that they're experimenting on recently dead bodies because we can measure the location and depths of the holes they're drilling," she continued. "In one example, each hole is drilled a little deeper than the last. So you can imagine a guy in his prehistoric Peruvian medical school practicing with his hand drill to know how many times he needs to turn it to nimbly and accurately penetrate the thickness of a skull."
Some might consider drilling a hole in someone's head a form of torture, but Kurin doesn't perceive it as such. "We can see where the trepanations are. We can see that they're shaving the hair. We see the black smudge of an herbal remedy they put over the wound," she noted. "To me, those are signs that the intention was to save the life of the sick or injured individual."
The remains Kurin excavated from the caves in Andahuaylas comprise perhaps the largest well-contextualized collection in the world. Most of the trepanned crania already studied reside in museums such as the Smithsonian Institution, the Field Museum of Natural History or the Hearst Museum of Anthropology. "Most were collected by archaeologists a century ago and so we don't have good contextual information," she said.
But thanks to Kurin's careful archaeological excavation of intact tombs and methodical analysis of the human skeletons and mummies buried therein, she knows exactly where, when and how the remains she found were buried, as well as who and what was buried with them. She used radiocarbon dating and insect casings to determine how long the bodies were left out before they skeletonized or were mummified, and multi-isotopic testing to reconstruct what they ate and where they were born. "That gives us a lot more information," she said.
"These ancient people can't speak to us directly, but they do give us information that allows us to reconstruct some aspect of their lives and their deaths and even what happened after they died," she continued. "Importantly, we shouldn't look at a state of collapse as the beginning of a 'dark age,' but rather view it as an era that breeds resilience and foments stunning innovation within the population.
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Dec. 19, 2013 — The newly sequenced genome of theAmborella plant addresses Darwin's "abominable mystery" -- the question of why flowers suddenly proliferated on Earth millions of years ago. The genome sequence sheds new light on a major event in the history of life on Earth: the origin of flowering plants, including all major food crop species. On 20 December 2013, a paper by the Amborella Genome Sequencing Project that includes a full description of the analyses performed by the project, as well as implications for flowering plant research, will be published in the journal Science. The paper is among three on different research areas related to theAmborella genome that will be published in the same issue of the journal.Amborella (Amborella trichopoda) is unique as the sole survivor of an ancient evolutionary lineage that traces back to the last common ancestor of all flowering plants. The plant is a small understory tree found only on the main island of New Caledonia in the South Pacific. An effort to decipher theAmborella genome -- led by scientists at Penn State University, the University at Buffalo, the University of Florida, the University of Georgia, and the University of California-Riverside -- is uncovering evidence for the evolutionary processes that paved the way for the amazing diversity of the more than 300,000 flowering plant species we enjoy today.
This unique heritage gives Amborella a special role in the study of flowering plants. "In the same way that the genome sequence of the platypus -- a survivor of an ancient lineage -- can help us study the evolution of all mammals, the genome sequence ofAmborella can help us learn about the evolution of all flowers," said Victor Albert of the University at Buffalo.
Scientists who sequenced the Amborella genome say that it provides conclusive evidence that the ancestor of all flowering plants, including Amborella, evolved following a "genome doubling event" that occurred about 200 million years ago. Some duplicated genes were lost over time but others took on new functions, including contributions to the development of floral organs.
"Genome doubling may, therefore, offer an explanation to Darwin's "abominable mystery" -- the apparently abrupt proliferation of new species of flowering plants in fossil records dating to the Cretaceous period," said Claude dePamphilis of Penn State University. "Generations of scientists have worked to solve this puzzle," he added.
Comparative analyses of the Amborella genome are already providing scientists with a new perspective on the genetic origins of important traits in all flowering plants -- including all major food crop species. "Because of Amborella's pivotal phylogenetic position, it is an evolutionary reference genome that allows us to better understand genome changes in those flowering plants that evolved later, including genome evolution of our many crop plants -- hence, it will be essential for crop improvement," stressed Doug Soltis of the University of Florida.
As another example of the value of the Amborella genome, Joshua Der at Penn State noted "We estimate that at least 14,000 protein-coding genes existed in the last common ancestor of all flowering plants. Many of these genes are unique to flowering plants, and many are known to be important for producing the flower as well as other structures and other processes specific to flowering plants."
"This work provides the first global insight as to how flowering plants are genetically different from all other plants on Earth," Brad Barbazuk of the University of Florida said, "and it provides new clues as to how seed plants are genetically different from non-seed plants."
Jim Leebens-Mack from UGA noted that "The Amborella genome sequence facilitated reconstruction of the ancestral gene order in the 'core eudicots,' a huge group that comprises about 75 percent of all angiosperms. This group includes tomato, apple and legumes, as well as timber trees such as oak and poplar." As an evolutionary outsider to this diverse group, the Amborellagenome allowed the researchers to estimate the linear order of genes in an ancestral eudicot genome and to infer lineage-specific changes that occurred over 120 million years of evolution in the core eudicot.
At the same time, Amborella seems to have acquired some unusual genomic characteristics since it split from the rest of the flowering plant tree of life. For example, DNA sequences that can change locations or multiply within the genome (transposable elements) seem to have stabilized in the Amborella genome. Most plants show evidence of recent bursts of this mobile DNA activity, "But Amborella is unique in that it does not seem to have acquired many new mobile sequences in the past several million years," stated Sue Wessler of the University of California-Riverside. "Insertion of some transposable elements can affect the expression and function of protein-coding genes, so the cessation of mobile DNA activity may have slowed the rate of evolution of both genome structure and gene function."
In addition to its utility in retrospective studies of the evolution of flowering plants, the Amborella genome sequence offers insights into the history and conservation of Amborella populations. There are only 18 known populations of this very special angiosperm in mountainous regions New Caledonia.
"Resequencing of individual Amborella plants across the species' range reveals geographic structure with conservation implications plus evidence of a recent, major genetic bottleneck," noted Pam Soltis of the University of Florida. A similar narrowing of genetic variation occurred when humans migrated from Africa to found modern-day Eurasian populations
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Wednesday, 25 December 2013
Dec. 19, 2013 — All good research breaks new ground, but rarely does the research unearth truths that challenge the foundation of a science. That's what Artem R. Oganov has done, and the professor of theoretical crystallography in the Department of Geosciences will have his work published in the Dec. 20, 2013 issue of the journal Science.The paper, titled "Unexpected stable stoichiometries of sodium chlorides," documents his predictions about, and experiments in, compressing sodium chloride -- rock salt -- to form new compounds. These compounds validate his methodology for predicting the properties of objects -- a methodology now used worldwide for computational material discovery -- and hold the promise of novel materials and applications.
"I think this work is the beginning of a revolution in chemistry," Oganov says. "We found, at low pressures achievable in the lab, perfectly stable compounds that contradict the classical rules of chemistry. If you apply the rather modest pressure of 200,000 atmospheres -- for comparison purposes, the pressure at the center of the Earth is 3.6 million atmospheres -- everything we know from chemistry textbooks falls apart."
Standard chemistry textbooks say that sodium and chlorine have very different electronegativities, and thus must form an ionic compound with a well-defined composition. Sodium's charge is +1, chlorine's charge is -1; sodium will give away an electron, chlorine wants to take an electron. According to chemistry texts and common sense, the only possible combination of these atoms in a compound is 1:1 -- rock salt, or NaCl.
"We found crazy compounds that violate textbook rules -- NaCl3, NaCl7, Na3Cl2, Na2Cl, and Na3Cl," says Weiwei Zhang, the lead author and visiting scholar at the Oganov lab and Stony Brook's Center for Materials by Design, directed by Oganov. "These compounds are thermodynamically stable and, once made, remain indefinitely; nothing will make them fall apart. Classical chemistry forbids their very existence. Classical chemistry also says atoms try to fulfill the octet rule -- elements gain or lose electrons to attain an electron configuration of the nearest noble gas, with complete outer electron shells that make them very stable. Well, here that rule is not satisfied."
This opens all kinds of possibilities. Oganov posited that, if you mix NaCl with metallic sodium, compress in a diamond anvil cell, and heat, you will get sodium-rich compounds like Na3Cl. He likewise theorized that, if you take NaCl, mix it with pure chlorine, and compress and heat, you will get chlorine-rich compounds such as NaCl3. This is exactly what was seen in the experiments, which were performed by the team of Alexander F. Goncharov of Carnegie Institution of Washington, confirming Oganov's predictions. "When you change the theoretical underpinnings of chemistry, that's a big deal," Goncharov says. "But what it also means is that we can make new materials with exotic properties."
Among the compounds Oganov and his team created are two-dimensional metals, where electricity is conducted along the layers of the structure. "One of these materials -- Na3Cl -- has a fascinating structure," he says. "It is [composed of] layers of NaCl and layers of pure sodium. The NaCl layers act as insulators; the pure sodium layers conduct electricity. Systems with two-dimensional electrical conductivity have attracted a lot of interest."
Like much of science, Oganov's pursuit began with curiosity -- and obstinacy.
"For a long time, this idea was haunting me -- when a chemistry textbook says that a certain compound is impossible, what does it really mean, impossible? Because I can, on the computer, place atoms in certain positions and in certain proportions. Then I can compute the energy. 'Impossible' really means that the energy is going to be high. So how high is it going to be? And is there any way to bring that energy down, and make these compounds stable?"
To Oganov, impossible didn't mean something absolute. "The rules of chemistry are not like mathematical theorems, which cannot be broken," he says. "The rules of chemistry can be broken, because impossible only means 'softly' impossible! You just need to find conditions where these rules no longer hold."
Oganov's team harnessed their own energy to bring the research to fruition. "We have a fantastic team," he says. "The theoretical work was done here at Stony Brook; the experimental work took place at the Geophysical Laboratory in the Carnegie Institution of Washington."
Additionally, Oganov's team utilized the NSF-funded Extreme Science and Engineering Discovery Environment (XSEDE) by running USPEX code -- the world-leading code for crystal structure prediction -- on Stampede, a supercomputer at the Texas Advanced Computing Center at the University of Texas at Austin. USPEX was developed by Oganov's lab and he estimates over 1,500 researchers use it worldwide.
His discovery may have application in the planetary sciences, where high-pressure phenomena abound. It may explain results of other experiments, where researchers compressed materials and got puzzling results. His computational methodology and structure-prediction algorithms will help researchers predict material combinations and structures that exhibit desired properties and levels of stability.
"We have learned an important lesson -- that even in well-defined systems, like sodium chloride, you can find totally new chemistry, and totally new and very exciting materials," Oganov says. "It's like discovering a new continent; now we need to map the land. Current rules cannot cope with this new chemistry. We need to invent something that will.
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Dec. 19, 2013 — Researchers have discovered a cause of aging in mammals that may be reversible.
The essence of this finding is a series of molecular events that enable communication inside cells between the nucleus and mitochondria. As communication breaks down, aging accelerates. By administering a molecule naturally produced by the human body, scientists restored the communication network in older mice. Subsequent tissue samples showed key biological hallmarks that were comparable to those of much younger animals.
"The aging process we discovered is like a married couple -- when they are young, they communicate well, but over time, living in close quarters for many years, communication breaks down," said Harvard Medical School Professor of Genetics David Sinclair, senior author on the study. "And just like with a couple, restoring communication solved the problem."
This study was a joint project between Harvard Medical School, the National Institute on Aging, and the University of New South Wales, Sydney, Australia, where Sinclair also holds a position.
The findings are published Dec. 19 in Cell.
Communication breakdown
Mitochondria are often referred to as the cell's "powerhouse," generating chemical energy to carry out essential biological functions. These self-contained organelles, which live inside our cells and house their own small genomes, have long been identified as key biological players in aging. As they become increasingly dysfunctional over time, many age-related conditions such as Alzheimer's disease and diabetes gradually set in.
Researchers have generally been skeptical of the idea that aging can be reversed, due mainly to the prevailing theory that age-related ills are the result of mutations in mitochondrial DNA -- and mutations cannot be reversed.
Sinclair and his group have been studying the fundamental science of aging -- which is broadly defined as the gradual decline in function with time -- for many years, primarily focusing on a group of genes called sirtuins. Previous studies from his lab showed that one of these genes, SIRT1, was activated by the compound resveratrol, which is found in grapes, red wine and certain nuts.
Ana Gomes, a postdoctoral scientist in the Sinclair lab, had been studying mice in which this SIRT1 gene had been removed. While they accurately predicted that these mice would show signs of aging, including mitochondrial dysfunction, the researchers were surprised to find that most mitochondrial proteins coming from the cell's nucleus were at normal levels; only those encoded by the mitochondrial genome were reduced.
"This was at odds with what the literature suggested," said Gomes.
As Gomes and her colleagues investigated potential causes for this, they discovered an intricate cascade of events that begins with a chemical called NAD and concludes with a key molecule that shuttles information and coordinates activities between the cell's nuclear genome and the mitochondrial genome. Cells stay healthy as long as coordination between the genomes remains fluid. SIRT1's role is intermediary, akin to a security guard; it assures that a meddlesome molecule called HIF-1 does not interfere with communication.
For reasons still unclear, as we age, levels of the initial chemical NAD decline. Without sufficient NAD, SIRT1 loses its ability to keep tabs on HIF-1. Levels of HIF-1 escalate and begin wreaking havoc on the otherwise smooth cross-genome communication. Over time, the research team found, this loss of communication reduces the cell's ability to make energy, and signs of aging and disease become apparent.
"This particular component of the aging process had never before been described," said Gomes.
While the breakdown of this process causes a rapid decline in mitochondrial function, other signs of aging take longer to occur. Gomes found that by administering an endogenous compound that cells transform into NAD, she could repair the broken network and rapidly restore communication and mitochondrial function. If the compound was given early enough -- prior to excessive mutation accumulation -- within days, some aspects of the aging process could be reversed.
Cancer connection
Examining muscle from two-year-old mice that had been given the NAD-producing compound for just one week, the researchers looked for indicators of insulin resistance, inflammation and muscle wasting. In all three instances, tissue from the mice resembled that of six-month-old mice. In human years, this would be like a 60-year-old converting to a 20-year-old in these specific areas.
One particularly important aspect of this finding involves HIF-1. More than just an intrusive molecule that foils communication, HIF-1 normally switches on when the body is deprived of oxygen. Otherwise, it remains silent. Cancer, however, is known to activate and hijack HIF-1. Researchers have been investigating the precise role HIF-1 plays in cancer growth.
"It's certainly significant to find that a molecule that switches on in many cancers also switches on during aging," said Gomes. "We're starting to see now that the physiology of cancer is in certain ways similar to the physiology of aging. Perhaps this can explain why the greatest risk of cancer is age. "
"There's clearly much more work to be done here, but if these results stand, then many aspects of aging may be reversible if caught early," said Sinclair.
The researchers are now looking at the longer-term outcomes of the NAD-producing compound in mice and how it affects the mouse as a whole. They are also exploring whether the compound can be used to safely treat rare mitochondrial diseases or more common diseases such as Type 1 and Type 2 diabetes. Longer term, Sinclair plans to test if the compound will give mice a healthier, longer life
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Dec. 18, 2013 — Astronomers affiliated with the Supernova Legacy Survey (SNLS) have discovered two of the brightest and most distant supernovae ever recorded, 10 billion light-years away and a hundred times more luminous than a normal supernova. Their findings appear in the Dec. 20 issue of theAstrophysical Journal.These newly discovered supernovae are especially puzzling because the mechanism that powers most of them -- the collapse of a giant star to a black hole or normal neutron star -- cannot explain their extreme luminosity. Discovered in 2006 and 2007, the supernovae were so unusual that astronomers initially could not figure out what they were or even determine their distances from Earth.
"At first, we had no idea what these things were, even whether they were supernovae or whether they were in our galaxy or a distant one," said lead author D. Andrew Howell, a staff scientist at Las Cumbres Observatory Global Telescope Network (LCOGT) and adjunct faculty at UC Santa Barbara. "I showed the observations at a conference, and everyone was baffled. Nobody guessed they were distant supernovae because it would have made the energies mind-bogglingly large. We thought it was impossible."
One of the newly discovered supernovae, named SNLS-06D4eu, is the most distant and possibly the most luminous member of an emerging class of explosions called superluminous supernovae. These new discoveries belong to a special subclass of superluminous supernovae that have no hydrogen.
The new study finds that the supernovae are likely powered by the creation of a magnetar, an extraordinarily magnetized neutron star spinning hundreds of times per second. Magnetars have the mass of the sun packed into a star the size of a city and have magnetic fields a hundred trillion times that of Earth. While a handful of these superluminous supernovae have been seen since they were first announced in 2009, and the creation of a magnetar had been postulated as a possible energy source, the work of Howell and his colleagues is the first to match detailed observations to models of what such an explosion might look like.
Co-author Daniel Kasen from UC Berkeley and Lawrence Berkeley National Lab created models of the supernova that explained the data as the explosion of a star only a few times the size of the sun and rich in carbon and oxygen. The star likely was initially much bigger but apparently shed its outer layers long before exploding, leaving only a smallish, naked core.
"What may have made this star special was an extremely rapid rotation," Kasen said. "When it ultimately died, the collapsing core could have spun up a magnetar like a giant top. That enormous spin energy would then be unleashed in a magnetic fury."
Discovered as part of the SNLS -- a five-year program based on observations at the Canada-France-Hawaii Telescope, the Very Large Telescope (VLT) and the Gemini and Keck telescopes to study thousands of supernovae -- the two supernovae could not initially be properly identified nor could their exact locations be determined. It took subsequent observations of the faint host galaxy with the VLT in Chile for astronomers to determine the distance and energy of the explosions. Years of subsequent theoretical work were required to figure out how such an astounding energy could be produced.
The supernovae are so far away that the ultraviolet (UV) light emitted in the explosion was stretched out by the expansion of the universe until it was redshifted (increased in wavelength) into the part of the spectrum our eyes and telescopes on Earth can see. This explains why the astronomers were initially baffled by the observations; they had never seen a supernova so far into the UV before. This gave them a rare glimpse into the inner workings of these supernovae. Superluminous supernovae are so hot that the peak of their light output is in the UV part of the spectrum. But because UV light is blocked by Earth's atmosphere, it had never been fully observed before.
The supernovae exploded when the universe was only 4 billion years old. "This happened before the sun even existed," Howell explained. "There was another star here that died and whose gas cloud formed the sun and Earth. Life evolved, the dinosaurs evolved and humans evolved and invented telescopes, which we were lucky to be pointing in the right place when the photons hit Earth after their 10-billion-year journey."
Such superluminous supernovae are rare, occurring perhaps once for every 10,000 normal supernovae. They seem to explode preferentially in more primitive galaxies -- those with smaller quantities of elements heavier than hydrogen or helium -- which were more common in the early universe.
"These are the dinosaurs of supernovae," Howell said. "They are all but extinct today, but they were more common in the early universe. Luckily we can use our telescopes to look back in time and study their fossil light. We hope to find many more of these kinds of supernovae with ongoing and future surveys.
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Tuesday, 24 December 2013
Dec. 18, 2013 — New research published in the journal Nature resolves decades of scientific controversy over the origin of the extremely energetic particles known as ultra-relativistic electrons in Earth's near-space environment and is likely to influence our understanding of planetary magnetospheres throughout the universe.Discovering the processes that control the formation and ultimate loss of these electrons in the Van Allen radiation belts -- the rings of highly charged particles that encircle Earth at a range of about 1,000 to 50,000 kilometers above the planet's surface -- is a primary science objective of the recently launched NASA Van Allen Probes mission. Understanding these mechanisms has important practical applications, because the enormous amounts of radiation trapped within the belts can pose a significant hazard to satellites and spacecraft, as well astronauts performing activities outside a craft.
Ultra-relativistic electrons in Earth's outer radiation belt can exhibit pronounced variability in response to activity on the sun and changes in the solar wind, but the dominant physical mechanism responsible for radiation-belt electron acceleration has remained unresolved for decades. Two primary candidates for this acceleration have been "inward radial diffusive transport" and "local stochastic acceleration" by very low-frequency plasma waves.
In research published Dec. 19 in Nature, lead author Richard Thorne, a distinguished professor of atmospheric and oceanic sciences in the UCLA College of Letters and Science, and his colleagues report on high-resolution satellite measurements of high-energy electrons during a geomagnetic storm on Oct. 9, 2012, which they have numerically modeled using a newly developed data-driven global wave model.
Their analysis reveals that scattering by intense, natural very low-frequency radio waves known as "chorus" in Earth's upper atmosphere is primarily responsible for the observed relativistic electron build-up.
The team's detailed modeling, together with previous observations of peaks in electron phase space density reported earlier this year by Geoff Reeves and colleagues in the journalScience, demonstrates the remarkable efficiency of natural wave acceleration in Earth's near-space environment and shows that radial diffusion was not responsible for the observed acceleration during this storm, Thorne said.
Co-authors of the new research include Qianli Ma, a graduate student who works in Thorne's lab; Wen Li, Binbin Ni and Jacob Bortnik, researchers in Thorne's lab; and members of the science teams on the Van Allen Probes, including Harlan Spence of the University of New Hampshire (principal investigator for RBSP-ECT) and Craig Kletzing of the University of Iowa (principal investigator for EMFISIS).
The local wave-acceleration process is a "universal physical process" and should also be effective in the magnetospheres of Jupiter, Saturn and other magnetized plasma environments in the cosmos, Thorne said. He thinks the new results from the detailed analysis of Earth will influence future modeling of other planetary magnetospheres.
The Van Allen radiation belts were discovered in Earth's upper atmosphere in 1958 by a team led by space scientist James Van Allen.
The new research was funded by the NASA, which launched the twin Van Allen probes in the summer of 2012
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Dec. 18, 2013 — African crocodiles, long thought of as just three known species, are among the most iconic creatures on that continent. But recent University of Florida research now finds that there are at least seven distinct African crocodile species.The UF team's latest discovery, led by then-doctoral candidate Matthew H. Shirley, is that what had been believed to be a single species of slender-snouted crocodile, is actually two.
The findings, which have major implications for policy-makers and conservationists, are outlined in a paper published online last week byProceedings of the Royal Society B.
The results emphasize how little is known about crocodile biogeography, or how species are distributed geographically over time, in Western and Central Africa, said Jim Austin, a co-author on the paper and Shirley's doctoral adviser at UF.
In the paper, Shirley and his team describe that West African populations of the slender-snouted crocodile do not share the same genetic or specific physical features as those populations in Central Africa -- and they estimate the two populations have been separated from each other geographically for at least 7 million years.
Biologists and conservation agencies need to know the precise taxonomy of animals and plants to avoid allocating precious conservation funding and effort working to protect species that may be more plentiful than believed, or -- as in this case -- ensuring that those resources can be directed toward species whose numbers are lower than believed.
Now that researchers know the West African slender-snouted crocodile is not the same species as its Central African cousin, Shirley said, that changes its standing.
"The West African slender-snouted crocodile is actually among the three or four most endangered crocodiles in the world," Shirley wrote in an email last week. "By finally recognizing that it is a unique species, we are in a much better position to advance its conservation and ensure its future."
Shirley likened the plight of the West African slender-snouted croc to the American alligator, which was on the cusp of extinction in the 1960s, but because it was protected, can now be easily observed in nature, be legally harvested at times, and helps drive Florida's tourism economy.
In Africa, crocodiles are traded and consumed as bush meat, making them a significant protein source for residents. They also play a major role at the top of the food pyramid, with significant influence on fish and crustraceans, much as lions control antelope populations.
"If we remove them from the ecosystem, then there may be profound effects on fisheries resources in the future," he wrote.
Crocodile species are often difficult to identify by physical characteristics alone. Most non-scientists can barely tell the difference between an alligator and a crocodile, in fact. So to bolster their genetic sleuthing, the UF team also looked at skull characteristics of slender-snouted crocodiles from museum collections and were able to find consistent differences between the species, Austin said.
Austin is a faculty member in UF's Department of Wildlife Ecology and Conservation, part of the Institute of Food and Agricultural Sciences. The other team members were Kent Vliet, laboratories coordinator with UF's biology department, and Amanda Carr, an undergraduate in Wildlife Ecology and Conservation.
Austin said the team's work is leading to helpful information for American zoos and aquariums by decoding the correct identification and taxonomy of African crocodiles housed in these facilities. Without the correct species identification, zookeepers could interbreed these hard-to-distinguish species, rendering them ineffective as founder animals for conservation purposes. And captive breeding efforts may be wasted when individuals of different species simply won't breed.
"We're doing the work to see which species they actually have," Austin said
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Dec. 18, 2013 — A group of researchers from the UK have used inkjet printing technology to successfully print cells taken from the eye for the very first time.The breakthrough, which has been detailed in a paper published today, 18 December, in IOP Publishing's journalBiofabrication, could lead to the production of artificial tissue grafts made from the variety of cells found in the human retina and may aid in the search to cure blindness.
At the moment the results are preliminary and provide proof-of-principle that an inkjet printer can be used to print two types of cells from the retina of adult rats―ganglion cells and glial cells. This is the first time the technology has been used successfully to print mature central nervous system cells and the results showed that printed cells remained healthy and retained their ability to survive and grow in culture.
Co-authors of the study Professor Keith Martin and Dr Barbara Lorber, from the John van Geest Centre for Brain Repair, University of Cambridge, said: "The loss of nerve cells in the retina is a feature of many blinding eye diseases. The retina is an exquisitely organised structure where the precise arrangement of cells in relation to one another is critical for effective visual function."
"Our study has shown, for the first time, that cells derived from the mature central nervous system, the eye, can be printed using a piezoelectric inkjet printer. Although our results are preliminary and much more work is still required, the aim is to develop this technology for use in retinal repair in the future."
The ability to arrange cells into highly defined patterns and structures has recently elevated the use of 3D printing in the biomedical sciences to create cell-based structures for use in regenerative medicine.
In their study, the researchers used a piezoelectric inkjet printer device that ejected the cells through a sub-millimetre diameter nozzle when a specific electrical pulse was applied. They also used high speed video technology to record the printing process with high resolution and optimised their procedures accordingly.
"In order for a fluid to print well from an inkjet print head, its properties, such as viscosity and surface tension, need to conform to a fairly narrow range of values. Adding cells to the fluid complicates its properties significantly," commented Dr Wen-Kai Hsiao, another member of the team based at the Inkjet Research Centre in Cambridge.
Once printed, a number of tests were performed on each type of cell to see how many of the cells survived the process and how it affected their ability to survive and grow.
The cells derived from the retina of the rats were retinal ganglion cells, which transmit information from the eye to certain parts of the brain, and glial cells, which provide support and protection for neurons.
"We plan to extend this study to print other cells of the retina and to investigate if light-sensitive photoreceptors can be successfully printed using inkjet technology. In addition, we would like to further develop our printing process to be suitable for commercial, multi-nozzle print heads," Professor Martin concluded
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Wednesday, 18 December 2013
Dec. 17, 2013 — A 12-year study of massive stars has reaffirmed that our Galaxy has four spiral arms, following years of debate sparked by images taken by NASA's Spitzer Space Telescope that only showed two arms.The new research, which is published online in the Monthly Notices of the Royal Astronomical Society, is part of the RMS Survey, which was launched by academics at the University of Leeds.
Astronomers cannot see what our Galaxy, which is called the Milky Way, looks like because we are on the inside looking out. But they can deduce its shape by careful observation of its stars and their distances from us.
"The Milky Way is our galactic home and studying its structure gives us a unique opportunity to understand how a very typical spiral galaxy works in terms of where stars are born and why," said Professor Melvin Hoare, a member of the RMS Survey Team in the School of Physics & Astronomy at the University of Leeds and a co-author of the research paper.
In the 1950s astronomers used radio telescopes to map our Galaxy. Their observations focussed on clouds of gas in the Milky Way in which new stars are born, revealing four major arms. NASA's Spitzer Space Telescope, on the other hand, scoured the Galaxy for infrared light emitted by stars. It was announced in 2008 that Spitzer had detected about 110 million stars, but only found evidence of two spiral arms.
The astronomers behind the new study used several radio telescopes in Australia, USA and China to individually observe about 1650 massive stars that had been identified by the RMS Survey. From their observations, the distances and luminosities of the massive stars were calculated, revealing a distribution across four spiral arms.
"It isn't a case of our results being right and those from Spitzer's data being wrong -- both surveys were looking for different things," said Professor Hoare. "Spitzer only sees much cooler, lower mass stars -- stars like our Sun -- which are much more numerous than the massive stars that we were targeting."
Massive stars are much less common than their lower mass counterparts because they only live for a short time -- about 10 million years. The shorter lifetimes of massive stars means that they are only found in the arms in which they formed, which could explain the discrepancy in the number of galactic arms that different research teams have claimed.
"Lower mass stars live much longer than massive stars and rotate around our Galaxy many times, spreading out in the disc. The gravitational pull in the two stellar arms that Spitzer revealed is enough to pile up the majority of stars in those arms, but not in the other two," explains Professor Hoare. "However, the gas is compressed enough in all four arms to lead to massive star formation."
Dr James Urquhart from the Max Planck Institute for Radio Astronomy in Bonn, Germany, and lead author of the paper, said: "It's exciting that we are able to use the distribution of young massive stars to probe the structure of the Milky Way and match the most intense region of star formation with a model with four spiral arms."
Professor Hoare concludes, "Star formation researchers, like me, grew up with the idea that our Galaxy has four spiral arms. It's great that we have been able to reaffirm that picture.
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Dec. 16, 2013 — Five-thousand years before it was immortalized in a British nursery rhyme, the cat that caught the rat that ate the malt was doing just fine living alongside farmers in the ancient Chinese village of Quanhucun, a forthcoming study in the Proceedings of the National Academy of Sciences has confirmed.
"At least three different lines of scientific inquiry allow us to tell a story about cat domestication that is reminiscent of the old 'house that Jack built' nursery rhyme," said study co-author Fiona Marshall, PhD, a professor of archaeology in Arts & Sciences at Washington University in St. Louis.
"Our data suggest that cats were attracted to ancient farming villages by small animals, such as rodents that were living on the grain that the farmers grew, ate and stored."
Set for early online publication in PNAS during the week of Dec. 16, the study provides the first direct evidence for the processes of cat domestication.
"Results of this study show that the village of Quanhucun was a source of food for the cats 5,300 years ago, and the relationship between humans and cats was commensal, or advantageous for the cats," Marshall said. "Even if these cats were not yet domesticated, our evidence confirms that they lived in close proximity to farmers, and that the relationship had mutual benefits."
Cat remains rarely are found in ancient archaeological sites, and little is known about how they were domesticated. Cats were thought to have first been domesticated in ancient Egypt, where they were kept some 4,000 years ago, but more recent research suggests close relations with humans may have occurred much earlier, including the discovery of a wild cat buried with a human nearly 10,000 years ago in Cyprus.
While it often has been argued that cats were attracted to rodents and other food in early farming villages and domesticated themselves, there has been little evidence for this theory.
The evidence for this study is derived from research in China led by Yaowu Hu and colleagues at the Chinese Academy of Sciences. Hu and his team analyzed eight bones from at least two cats excavated from the site.
Using radiocarbon dating and isotopic analyses of carbon and nitrogen traces in the bones of cats, dogs, deer and other wildlife unearthed near Quanhucan, the research team demonstrated how a breed of once-wild cats carved a niche for themselves in a society that thrived on the widespread cultivation of the grain millet.
Carbon isotopes indicate that rodents, domestic dogs and pigs from the ancient village were eating millet, but deer were not. Carbon and nitrogen isotopes show that cats were preying on animals that lived on farmed millet, probably rodents. At the same time, an ancient rodent burrow into a storage pit and the rodent-proof design of grain storage pots indicate that farmers had problems with rodents in the grain stores.
Other clues gleaned from the Quanhucun food web suggest the relationship between cats and humans had begun to grow closer. One of the cats was aged, showing that it survived well in the village. Another ate fewer animals and more millet than expected, suggesting that it scavenged human food or was fed.
Recent DNA studies suggest that most of the estimated 600 million domestic cats now living around the globe are descendants most directly of the Near Eastern Wildcat, one of the five Felis sylvestris lybica wildcat subspecies still found around the Old World.
Marshall, an expert on animal domestication, said there currently is no DNA evidence to show whether the cats found at Quanhucun are descendants of the Near Eastern Wildcat, a subspecies not native to the area. If the Quanhucun cats turn out to be close descendents of the Near Eastern strain, it would suggest they were domesticated elsewhere and later introduced to the region.
"We do not yet know whether these cats came to China from the Near East, whether they interbred with Chinese wild-cat species, or even whether cats from China played a previously unsuspected role in domestication," Marshall said.
This question is now being pursued by researchers based in China and in France
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Dec. 16, 2013 — Humans have a distinctive hand anatomy that allows them to make and use tools. Apes and other nonhuman primates do not have these distinctive anatomical features in their hands, and the point in time at which these features first appeared in human evolution is unknown. Now, a University of Missouri researcher and her international team of colleagues have found a new hand bone from a human ancestor who roamed the earth in East Africa approximately 1.42 million years ago. They suspect the bone belonged to the early human species, Homo erectus. The discovery of this bone is the earliest evidence of a modern human-like hand, indicating that this anatomical feature existed more than half a million years earlier than previously known.
"This bone is the third metacarpal in the hand, which connects to the middle finger. It was discovered at the 'Kaitio' site in West Turkana, Kenya," said Carol Ward, professor of pathology and anatomical sciences at MU. The discovery was made by a West Turkana Paleo Project team, led by Ward's colleague and co-author Fredrick Manthi of the National Museums of Kenya. "What makes this bone so distinct is that the presence of a styloid process, or projection of bone, at the end that connects to the wrist. Until now, this styloid process has been found only in us, Neandertals and other archaic humans."
The styloid process helps the hand bone lock into the wrist bones, allowing for greater amounts of pressure to be applied to the wrist and hand from a grasping thumb and fingers. Ward and her colleagues note that a lack of the styloid process created challenges for apes and earlier humans when they attempted to make and use tools. This lack of a styloid process may have increased the chances of having arthritis earlier, Ward said.
The bone was found near sites where the earliest Acheulian tools have appeared. Acheulian tools are ancient, shaped stone tools that include stone hand axes more than 1.6 million years old. Being able to make such precise tools indicates that these early humans were almost certainly using their hands for many other complex tasks as well, Ward said.
"The styloid process reflects an increased dexterity that allowed early human species to use powerful yet precise grips when manipulating objects. This was something that their predecessors couldn't do as well due to the lack of this styloid process and its associated anatomy," Ward said. "With this discovery, we are closing the gap on the evolutionary history of the human hand. This may not be the first appearance of the modern human hand, but we believe that it is close to the origin, given that we do not see this anatomy in any human fossils older than 1.8 million years. Our specialized, dexterous hands have been with us for most of the evolutionary history of our genus, Homo. They are -- and have been for almost 1.5 million years -- fundamental to our survival."
The study was published in the Proceedings of the National Academy of Sciences this week. Members of Ward's team who helped discover and analyze the bone include: Matthew Tocheri, National Museum of Natural History in the Smithsonian Institution; J. Michael Plavcan, University of Arkansas; Francis Brown, University of Utah; and Fredrick Manthi, National Museums of Kenya.
Dec. 16, 2013 — W49A might be one of the best-kept secrets in our galaxy. This star-forming region shines 100 times brighter than the Orion nebula, but is so obscured by dust that very little visible or infrared light escapes.
The Smithsonian's Submillimeter Array (SMA) has peered through the dusty fog to provide the first clear view of this stellar nursery. The SMA revealed an active site of star formation being fed by streamers of infalling gas.
"We were amazed by all the features we saw in the SMA images," says lead author Roberto Galván-Madrid, who conducted this research at the Harvard-Smithsonian Center for Astrophysics (CfA) and the European Southern Observatory (ESO).
W49A is located about 36,000 light-years from Earth, on the opposite side of the Milky Way. It represents a nearby example of the sort of vigorous star formation seen in so-called "starburst" galaxies, where stars form 100 times faster than in our galaxy.
The heart of W49A holds a giant yet surprisingly compact star cluster. About 100,000 stars already exist within a space only 10 light-years on a side. In contrast, fewer than 10 stars lie within 10 light-years of our Sun. In a few million years, the giant star cluster in W49A will be almost as crowded as a globular cluster.
The SMA also revealed an intricate network of filaments feeding gas into the center, much like tributaries feed water into mighty rivers on Earth. The gaseous filaments in W49A form three big streamers, which funnel star-building material inward at speeds of about 4,500 miles per hour (2 km/sec).
"Move over, Mississippi!" quips co-author Qizhou Zhang of the CfA.
Being denser than average will help the W49A star cluster to survive. Most star clusters in the galactic disk dissolve rapidly, their stars migrating away from each other under the influence of gravitational tides. This is why none of the Sun's sibling stars remain nearby. Since it is so compact, the cluster in W49A might remain intact for billions of years.
The Submillimeter Array mapped the molecular gas within W49A in exquisite detail. It showed that central 30 light-years of W49A is several hundred times denser than the average molecular cloud in the Milky Way. In total, the nebula contains about 1 million suns' worth of gas, mostly molecular hydrogen.
"We suspect that the organized architecture seen in W49A is rather common in massive stellar cluster-formation," adds co-author Hauyu Baobab Liu of the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) in Taiwan.
The team expects to continue analyzing the SMA data for some time to come.
"It's a mine of information," says Galván-Madrid.
Their research was published in the December 2013Astrophysical Journal
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Dec. 13, 2013 — South Pole Telescope scientists have detected for the first time a subtle distortion in the oldest light in the universe, which may help reveal secrets about the earliest moments in the universe's formation.
The scientists observed twisting patterns in the polarization of the cosmic microwave background -- light that last interacted with matter very early in the history of the universe, less than 400,000 years after the big bang. These patterns, known as "B modes," are caused by gravitational lensing, a phenomenon that occurs when the trajectory of light is bent by massive objects, much like a lens focuses light.
A multi-institutional collaboration of researchers led by John Carlstrom, the S. Chandrasekhar Distinguished Service Professor in Astronomy & Astrophysics at the University of Chicago, made the discovery. They announced their findings in a paper published Sept. 30, 2013, in the journalPhysical Review Letters -- using the first data from SPTpol, a polarization-sensitive camera installed on the telescope in January 2012.
"The detection of B-mode polarization by South Pole Telescope is a major milestone, a technical achievement that indicates exciting physics to come," Carlstrom said.
The cosmic microwave background is a sea of photons (light particles) left over from the big bang that pervades all of space, at a temperature of minus 270 degrees Celsius -- a mere 3 degrees above absolute zero. Measurements of this ancient light have already given physicists a wealth of knowledge about the properties of the universe. Tiny variations in temperature of the light have been painstakingly mapped across the sky by multiple experiments, and scientists are gleaning even more information from polarized light.
Light is polarized when its electromagnetic waves are preferentially oriented in a particular direction. Light from the cosmic microwave background is polarized mainly due to the scattering of photons off of electrons in the early universe, through the same process by which light is polarized as it reflects off the surface of a lake or the hood of a car. The polarization patterns that result are of a swirl-free type, known as "E modes," which have proven easier to detect than the fainter B modes, and were first measured a decade ago, by a collaboration of researchers using the Degree Angular Scale Interferometer, another UChicago-led experiment.
B modes can't be generated by simple scattering, instead pointing to a more complex process -- hence scientists' interest in measuring them. Gravitational lensing, it has long been predicted, can twist E modes into B modes as photons pass by galaxies and other massive objects on their way toward earth. This expectation has now been confirmed.
To tease out the B modes in their data, the scientists used a previously measured map of the distribution of mass in the universe to determine where the gravitational lensing should occur. They combined their measurement of E modes with the mass distribution to provide a template of the expected twisting into B modes. The scientists are currently working with another year of data to further refine their measurement of B modes.
The careful study of such B modes will help physicists better understand the universe. The patterns can be used to map out the distribution of mass, thereby more accurately defining cosmologically important properties like the masses of neutrinos, tiny elementary particles prevalent throughout the cosmos.
Similar, more elusive B modes would provide dramatic evidence of inflation, the theorized turbulent period in the moments after the big bang when the universe expanded extremely rapidly. Inflation is a well-regarded theory among cosmologists because its predictions agree with observations, but thus far there is not a definitive confirmation of the theory. Measuring B modes generated by inflation is a possible way to alleviate lingering doubt.
"The detection of a primordial B-mode polarization signal in the microwave background would amount to finding the first tremors of the Big Bang," said the study's lead author, Duncan Hanson, a postdoctoral scientist at McGill University in Canada.
B modes from inflation are caused by gravitational waves. These ripples in space-time are generated by intense gravitational turmoil, conditions that would have existed during inflation. These waves, stretching and squeezing the fabric of the universe, would give rise to the telltale twisted polarization patterns of B modes. Measuring the resulting polarization would not only confirm the theory of inflation -- a huge scientific achievement in itself -- but would also give scientists information about physics at very high energies -- much higher than can be achieved with particle accelerators.
The measurement of B modes from gravitational lensing is an important first step in the quest to measure inflationary B modes. In inflationary B mode searches, lensing B modes show up as noise. "The new result shows that this noise can be accounted for and subtracted off so that scientists can search for and hopefully measure the inflationary B modes underneath," Hanson said. "The lensing signal itself can also be used by itself to learn about the distribution of mass in the universe.
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Dec. 11, 2013 — It's official: East Antarctica is pushing West Antarctica around.Now that West Antarctica is losing weight--that is, billions of tons of ice per year--its softer mantle rock is being nudged westward by the harder mantle beneath East Antarctica.
The discovery comes from researchers led by The Ohio State University, who have recorded GPS measurements that show West Antarctic bedrock is being pushed sideways at rates up to about twelve millimeters--about half an inch--per year. This movement is important for understanding current ice loss on the continent, and predicting future ice loss.
They reported the results on Thursday, Dec. 12 at the American Geophysical Union meeting in San Francisco.
Half an inch doesn't sound like a lot, but it's actually quite dramatic compared to other areas of the planet, explained Terry Wilson, professor of earth sciences at Ohio State. Wilson leads POLENET, an international collaboration that has planted GPS and seismic sensors all over the West Antarctic Ice Sheet.
She and her team weren't surprised to detect the horizontal motion. After all, they've been using GPS to observe vertical motion on the continent since the 1990's.
They were surprised, she said, to find the bedrock moving towards regions of greatest ice loss.
"From computer models, we knew that the bedrock should rebound as the weight of ice on top of it goes away," Wilson said. "But the rock should spread out from the site where the ice used to be. Instead, we see movement toward places where there was the most ice loss."
The seismic sensors explained why. By timing how fast seismic waves pass through Earth under Antarctica, the researchers were able to determine that the mantle regions beneath east and west are very different. West Antarctica contains warmer, softer rock, and East Antarctica has colder, harder rock.
Stephanie Konfal, a research associate with POLENET, pointed out that where the transition is most pronounced, the sideways movement runs perpendicular to the boundary between the two types of mantle.
She likened the mantle interface to a pot of honey.
"If you imagine that you have warm spots and cold spots in the honey, so that some of it is soft and some is hard," Konfal said, "and if you press down on the surface of the honey with a spoon, the honey will move away from the spoon, but the movement won't be uniform. The hard spots will push into the soft spots. And when you take the spoon away, the soft honey won't uniformly flow back up to fill the void, because the hard honey is still pushing on it."
Or, put another way, ice compressed West Antarctica's soft mantle. Some ice has melted away, but the soft mantle isn't filling back in uniformly, because East Antarctica's harder mantle is pushing it sideways. The crust is just along for the ride.
This finding is significant, Konfal said, because we use these crustal motions to understand ice loss.
"We're witnessing expected movements being reversed, so we know we really need computer models that can take lateral changes in mantle properties into account."
Wilson said that such extreme differences in mantle properties are not seen elsewhere on the planet where glacial rebound is occurring.
"We figured Antarctica would be different," she said. "We just didn't know how different."
Ohio State's POLENET academic partners in the United States are Pennsylvania State University, Washington University, New Mexico Tech, Central Washington University, the University of Texas Institute for Geophysics and the University of Memphis. A host of international partners are part of the effort as well. The project is supported by the UNAVCO and IRIS-PASSCAL geodetic and seismic facilities
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Dec. 13, 2013 — If you have ever said or done the wrong thing at the wrong time, you should read this. Neuroscientists at The University of Texas Health Science Center at Houston (UTHealth) and the University of California, San Diego, have successfully demonstrated a technique to enhance a form of self-control through a novel form of brain stimulation.Study participants were asked to perform a simple behavioral task that required the braking/slowing of action -- inhibition -- in the brain. In each participant, the researchers first identified the specific location for this brake in the prefrontal region of the brain. Next, they increased activity in this brain region using stimulation with brief and imperceptible electrical charges. This led to increased braking -- a form of enhanced self-control.
This proof-of-principle study appears in the Dec. 11 issue of The Journal of Neuroscience and its methods may one day be useful for treating attention deficit hyperactivity disorder (ADHD), Tourette's syndrome and other severe disorders of self-control.
"There is a circuit in the brain for inhibiting or braking responses," said Nitin Tandon, M.D., the study's senior author and associate professor in The Vivian L. Smith Department of Neurosurgery at the UTHealth Medical School. "We believe we are the first to show that we can enhance this braking system with brain stimulation."
A computer stimulated the prefrontal cortex exactly when braking was needed. This was done using electrodes implanted directly on the brain surface.
When the test was repeated with stimulation of a brain region outside the prefrontal cortex, there was no effect on behavior, showing the effect to be specific to the prefrontal braking system.
This was a double-blind study, meaning that participants and scientists did not know when or where the charges were being administered.
The method of electrical stimulation was novel in that it apparently enhanced prefrontal function, whereas other human brain stimulation studies mostly disrupt normal brain activity. This is the first published human study to enhance prefrontal lobe function using direct electrical stimulation, the researchers report.
The study involved four volunteers with epilepsy who agreed to participate while being monitored for seizures at the Mischer Neuroscience Institute at Memorial Hermann-Texas Medical Center (TMC). Stimulation enhanced braking in all four participants.
Tandon has been working on self-control research with researchers at the University of California, San Diego, for five years. "Our daily life is full of occasions when one must inhibit responses. For example, one must stop speaking when it's inappropriate to the social context and stop oneself from reaching for extra candy," said Tandon, who is a neurosurgeon with the Mischer Neuroscience Institute at Memorial Hermann-TMC.
The researchers are quick to point out that while their results are promising, they do not yet point to the ability to improve self-control in general. In particular, this study does not show that direct electrical stimulation is a realistic option for treating human self-control disorders such as obsessive-compulsive disorder, Tourette's syndrome and borderline personality disorder. Notably, direct electrical stimulation requires an invasive surgical procedure, which is now used only for the localization and treatment of severe epilepsy
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