Tiny Flame Shines Light On Supernovae Explosions

Starting from the behavior of small flames in the laboratory, a team of researchers has gained new insights into the titanic forces that drive Type Ia supernova explosions. These stellar explosions are important tools for studying the evolution of the universe, so a better understanding of how they behave would help answer some of the fundamental questions in astronomy.

Type Ia supernovae form when a white dwarf star -- the left-over cinder of a star like our Sun -- accumulates so much mass from a companion star that it reignites its collapsed stellar furnace and detonates, briefly outshining all other stars in its host galaxy. Because these stellar explosions have a characteristic brightness, astronomers use them to calculate cosmic distances. (It was by studying Type Ia supernovae that two independent research teams determined that the expansion of the Universe was accelerating, earning them the 2011 Nobel Prize in Physics).

To better understand the complex conditions driving this type of supernova, the researchers performed new 3-D calculations of the turbulence that is thought to push a slow-burning flame past its limits, causing a rapid detonation -- the so-called deflagration-to-detonation transition (DDT). How this transition might occur is hotly debated, and these calculations provide insights into what is happening at the moment when the white dwarf star makes this spectacular transition to supernova. "Turbulence properties inferred from these simulations provides insight into the DDT process, if it occurs," said Aaron Jackson, currently an NRC Research Associate working in the Laboratory for Computational Physics and Fluid Dynamics at the Naval Research Laboratory in Washington, D.C. At the time of this research, Jackson was a graduate student at Stony Brook University on Long Island, New York.

Jackson and his colleagues Dean Townsley from the University of Alabama at Tuscaloosa, and Alan Calder also of Stony Brook, presented their data at the American Physical Society's (APS) Division of Fluid Dynamics (DFD) meeting in Baltimore, Nov. 20-22, 2011.

While the deflagration-detonation transition mechanism is still not well understood, a prevailing hypothesis in the astrophysics community is that if turbulence is intense enough, DDT will occur. Extreme turbulent intensities inferred in the white dwarf from the researchers' simulations suggest DDT is likely, but the lack of knowledge about the process allows a large range of

outcomes from the explosion. Matching simulations to observed supernovae can identify likely conditions for DDT.

"There are a few options for how to simulate how they [supernovae] might work, each of which has different advantages and disadvantages," said Townsley. "Our goal is to provide a more realistic simulation of how a given supernova scenario will perform, but that is a long-term goal and involves many different improvements that are still in progress."

Read more at Science Daily

Predators Drive the Evolution of Poison Dart Frogs' Skin Patterns

Natural selection has played a role in the development of the many skins patterns of the tiny Ranitomeya imitator poison dart frog, according to a study that will be published in an upcoming edition of American Naturalist by University of Montreal biologist Mathieu Chouteau.

The researcher's methodology was rather unusual: on three occasions over three days, at two different sites, Chouteau investigated the number of attacks that had been made on fake frogs, by counting how many times that had been pecked. Those that were attacked the least looked like local frogs, while those that came from another area had obviously been targeted.

The brightly coloured frogs that we find in tropical forests are in fact sending a clear message to predators: "don't come near me, I'm poisonous!" But why would a single species need multiple patterns when one would do? It appears that when predators do not recognize a poisonous frog as being a member of the local group, it attacks in the hope that it has chanced upon edible prey. "When predators see that their targets are of a different species, they attack. Over the long term, that explains how patterns and colours become uniform in an area," said Bernard Angers, who directed Chouteau's doctoral research.

A total of 3,600 life-size plasticine models, each less than one centimetre long, were used in the study. The menagerie was divided between two carefully identified sites in the Amazon forest. "The trickiest part was transporting my models without arousing suspicion at the airport and customs controls," Chouteau said. He chose plasticine following a review of scientific literature. "Many scientists have successfully used plasticine to create models of snakes, salamanders and poison dart frogs." The Peruvian part of the forest proved to be ideal for this study, as two radically different looking groups of frogs are found there: one, living on a plain, has yellow stripes, and the other, living on a mountain, has green patches. The two colonies are ten kilometers apart. 900 fake frogs were placed in each area in carefully targeted positions. Various combinations of colours and patterns were used.

Chouteau was particularly surprised by the "very small spatial scale at which the evolutionary process has taken place." Ten kilometers of separation sufficed for a clearly different adaptation to take place. "A second surprise was the learning abilities of the predator community, especially the speed at which the learning process takes place when a new and exotic defensive signal is introduced on a massive scale," Chouteau said.

Read more at Science Daily

Ancient Cave Lion Bones Reveal Big Cats’ Diet

A quarter larger than today’s lions, the European cave lion was one of the biggest cats around 12,000 years ago. Now, an unusually sophisticated analysis of its bones is revealing what these creatures ate—and why they may have disappeared.

Although they were certainly massive cats, the term “cave lion” is a bit of a misnomer. Unlike today’s lions, males probably didn’t have manes, and they appear to have been solitary hunters. What’s more, though their bones are best preserved in caves, they probably lived in the open. But they did have one thing in common with their modern relatives: they appear to have worried humans. The big cats show up in ice age cave paintings and in ivory figurines, suggesting that they were a major concern for our ancestors.

To figure out what these lions hunted, biogeologist Hervé Bocherens and colleagues at the University of Tübingen in Germany, analyzed bone samples from 14 cave lions—found in four caves in France and central Europe—that lived between 12,000 and 40,000 years ago. The team focused on the chemical content of the bone collagen, which is often well-preserved, even in bones tens of thousands of years old. By incinerating a tiny fragment of preserved bone—usually less than a milligram—researchers can identify the molecules inside it and determine an animal’s diet.

Scientists have perfected the technique over the years. It was used recently to look at the diet of Neandertals, but this is one of the first studies to use it to look at a nonhuman predator—and the analysis is now sensitive enough to look several steps down the food chain. This enabled Bocherens to determine not only what cave lions ate but also what their prey ate. And that made it possible to tell, for example, whether lions were targeting full-size cave bears or their more vulnerable cubs, because adults and babies eat different diets themselves. “There’s a difference between the [chemical] signal of adults and babies,” Bocherens says. “Babies drink the milk of the mother.”

As it turned out, this distinction was important. Bocherens’s analysis, reported in the 6 December issue of Quaternary International, revealed that the cave lions occasionally ate bear cubs but not adults. Their favorite food, however, was reindeer, which Bocherens and his team determined consumed massive quantities of lichen, much as their modern descendants did. The cave lion diet, Bocherens says, appears to have been much more finicky than that of today’s lions, which eat just about anything they can catch.

The results may provide new insights into why cave lions died out. When Europe’s climate began to warm about 19,000 years ago, the landscape gradually changed from chilly, open steppes to denser forests. That would have made an inhospitable habitat for reindeer and for the cave lions that depended on them for food. (Cave bears were also dying out at the same time.)

Experts say the ability to dissect ancient diets so thoroughly is a tantalizing tool but that this particular study is too geographically limited to be conclusive about cave lions. “It’s quite astonishing that you can quite convincingly demonstrate what predators were eating tens of thousands of years ago,” says Anthony Stuart, a biologist at Durham University in the United Kingdom. “One obvious thing to do is extend the study to a wider area” to see how diets might have varied geographically. Cave lions, he notes, “ranged from Spain across Europe and Siberia all the way to the northwestern part of North America.”

Read more at Wired Science

Blame Your Crooked Teeth on Early Farmers

When humans turned from hunting and gathering to farming some 10,000 years ago, they set our species on the road to civilization. Agricultural surpluses led to division of labor, the rise of cities, and technological innovation. But civilization has had both its blessings and its curses. One downside of farming, a new study demonstrates, was a shortening of the human jaw that has left precious little room for our teeth and sends many of us to an orthodontist’s chair.

Although all living humans belong to one species, Homo sapiens, there are recognizable differences in the shapes of our skulls and faces across the world. In recent years, anthropologists have concluded that most of this geographic variation in skull shape is due to chance, so-called genetic drift, rather than natural selection. But some features of our faces, including the shape of our lower jaws, don’t seem to follow this random pattern.

A number of researchers have hypothesized that the advent of agriculture, which led to diets consisting of softer foods that required less chewing, led to modifications in the lower jaw, either through natural selection or from developmental changes caused by the way we use our jaws beginning in infancy. But evidence from ancient skeletons has been limited. To test the hypothesis, Noreen von Cramon-Taubadel, an anthropologist at the University of Kent in the United Kingdom, looked at skull and jaw shape in 11 populations, six of which live by farming and five of which are hunter-gatherers. The populations included people from Africa, Asia, Australia, Europe, and the Americas.

In the first part of her study, von Cramon-Taubadel measured the shapes of 322 crania and 295 jaws from museums, representing the 11 populations. She found a significant correlation between jaw shape and how each population made its living. Thus hunter-gatherers tended to have longer (more jutting) and narrower lower jaws, whereas those of farmers were relatively shorter and wider. But the form of the crania did not show this correlation, with one exception: The shape of the palate of the upper jaw, which is closely associated with the lower jaw and involved in chewing, also varied to some degree between farmers and hunter-gatherers.

To see whether this dichotomy in jaw shape between farmers and hunter-gatherers could be due to other factors, von Cramon-Taubadel searched for possible correlations with geographic location, genetic history, and climate variation but found little or none. In her report published online this week in the Proceedings of the National Academy of Sciences, she concludes that the transition to farming — which involved the domestication of plants and animals, a major increase in food processing, and thus consumption of easier to chew food — altered the shape of the human jaw, making it shorter and less robust. And this shortening of the jaw, she suggests, led to greater crowding of the teeth and the orthodontist bills that plague many modern families.

As for whether these changes in jaw shape are due to natural selection over many generations or simply changes that arise anew in each growing infant, von Cramon-Taubadel cites experimental studies showing that animals raised on softer, more processed foods grow smaller jaws than those fed fresh, unprocessed food. But even if the jaw alterations were due to natural selection, she concludes, they would have taken place over a relatively short period of evolutionary time.

Read more at Wired Science

Hula Painted Frog Bounces Back From Extinction

A species of frog that was thought to have been made extinct during the notorious drainage of the Hula marshlands in Israel, has appeared again after more than 50 years of hiding.

The Palestinian or Hula painted frog (Discoglossus nigriventer) originally went missing when the Jewish National Fund drained the marshlands around the Hula Valley in the 1950s. The swamp was a breeding ground for malaria, and the disease was killing off the population.

The JNF removed the water from the swamp and redirected the flow of water to the river Jordan with artificial estuaries. But the operation led to numerous knock-on effects — the reclaimed land was useless for agriculture, toxins invaded the river and dumped peat routinely caught fire.

The disastrous operation also led to huge destruction of ecosystems, wiping out water plants, tropical aquatic ferns, the ray-finned fish Acanthobrama hulensis and the cichlid fish Tristramella intermedia. Until this week, it was thought that the hula painted frog was among the lost species.

But a routine patrol at the Ha’Hula lake by Israel’s Nature and Parks Authority turned up a mysterious, unknown female frog and took it back to the lab for testing. It was soon confirmed that it was a Hula painted frog, and the rare species had hung on amongst the devastation of its habitat.

Read more at Wired Science

New York City Buzzing With New Bee Species

The American Museum of Natural History has announced the discovery of eleven new species of bees, including four from New York City and its suburbs.

The bees, described in the journal Zootaxa, include small-to-medium-sized sweat bees, so named because of their attraction to the salt in human sweat. A team of scientists identified the bees with the help of the vast digital and physical bee collections at the AMNH.

A standout bee among the 11 is Lasioglossum gotham, aka the Gotham Bee. It was spotted in the New York Botanical Garden, in the Bronx, and in the Brooklyn Botanic Garden.

“Declines in honey bees and other bees have received a lot of attention in recent years, but it is not generally appreciated that bee species entirely new to science are still being discovered even within our largest cities," co-author John Ascher, a research scientist in the museum’s Division of Invertebrate Zoology, was quoted as saying in a press release. "New York City has a surprising diversity of bees, with more than 250 described species recorded."

Ascher helped to collect and curate specimens of some of the new species. He leads the Digital Bee Collections Network, a collaborative project that serves as the online clearinghouse for information about the world’s bee species.

The 11 new bees also include Lasioglossum ascheri, which was classified from just two specimens found in Westchester and Suffolk counties; L. katherinae from Brooklyn and Nassau County; Lasioglossum rozeni from Suffolk County; and L. georgeickworti from Queens and Nassau and Suffolk counties.

“It's remarkable that so many bees are able to live in such a major urban area,” co-author Jason Gibbs, a Cornell Univeristy researcher, was quoted as saying. “Natural areas like urban parks and rooftop and botanical gardens provide the nesting sites and floral diversity that bees need. This little bee (Gotham Bee) has been quietly living in the city, pollinating flowers in people’s gardens for years. It’s a pleasure to help give it some well-deserved recognition.”

Over the past decade there's been renewed interest in bees, partly because of a complex problem called Colony Collapse Disorder, which has killed countless bees in recent years. These buzzing insects are the most important pollinators in the Northeastern United States, fertilizing plants as they fly from flower to flower on pollen-collecting missions.

The discovery of new bee species in New York City and the vicinity highlights the need for additional study of native bee diversity across the country, Gibbs believes.

Read more at Discovery News

Ice Mummy May Have Smashed Eye in Fall

A sharp incision in his right eye may have contributed to the rapid demise of Ötzi the Iceman, the famous mummy who died in the Italian Alps more than 5,000 years ago.

Twenty years after two hikers stumbled upon the Iceman in a melting glacier, new analyses have revealed that a deep cut likely led to heavy bleeding in the man's eye. In the cold, high-altitude conditions where he was found, that kind of injury would have been tough to recover from.

The official opinion remains that an arrow in his left shoulder was the cause of death for Ötzi. But the new study raises the possibility -- for some, at least -- that he fell over after being shot by an arrow. And, at higher than 10,000 feet in elevation, his alpine fall may have made the situation much worse.

"Maybe he fell down or maybe he had a fight up there, nobody knows," said Wolfgang Recheis, a physicist in the radiology department at the University of Innsbruck in Austria. "With this cut alone, at 3,250 meters, it would have been a deadly wound up there. Bleeding to death in the late afternoon when it was getting cold up there, this could be really dangerous."

Ever since his discovery in 1991, Ötzi has been measured, photographed, X-rayed, CT-scanned and endlessly speculated about. The Iceman Photoscan website allows anyone to scrutinize every inch of the body, which belonged to a 5'3", 110-pound, 45-year old man.

Ten years ago, researchers found a flint arrowhead buried in Ötzi's left shoulder blade inside a two-centimeter (0.8-inch) wide hole. They concluded that the arrow pierced a major artery and killed him within minutes. At a conference in September, experts reaffirmed that assessment.

But in one of the latest studies, Recheis used the most advanced CT-scanning technology available to take a closer look at Ötzi's right eye. Earlier examinations had shown a crack in the skull in that spot. The new work revealed a deep incision in the same place.

Scans also revealed iron crystals around the right eye and forehead, which produce a bluish hue. And since the region's rocks are naturally low in iron, Recheis and colleagues suspect the iron is a sign of a hematoma, or massive bleeding outside of the blood vessels. A biopsy is needed for confirmation.

Despite the officially stated opinion on Ötzi's cause of death, Recheis is not convinced that the arrow wound was deadly on its own.

"My South Tyrolean colleagues say the arrow most probably hit the sub-clavicular artery or other vital vessel and thus the Iceman died," Recheis said. "But there are doubts. It's justified that the arrow did not hit any vital vessels or nerves as far as we can say from the data we have."

"This could be the first thing," he added. "He was up there and shot by an arrow. And then he fell down, cut his eye and bled to death."

Albert Zink, head of the EURAC Institute for Mummies and the Iceman in Bolzano, Italy, was surprised and perplexed to hear of these new claims. At a conference this fall, he said, a whole table-full of experts discussed the evidence and unanimously agreed that the arrow killed the Iceman.

The shoulder wound, he said, was clearly fresh and bleeding heavily when Ötzi died.

Read more at Discovery News

Who REALLY Discovered the Expanding Universe?

Astronomer Edwin Hubble's landmark paper on the rate of expansion of the universe was published in 1929, overturning the long-held belief among scientists that the universe was static and unchanging.

That's why the Hubble Constant (the number that describes the rate of expansion) is named after him, not to mention the Hubble Space Telescope.

Less well known is that Hubble might not have been the first the person to make this momentous discovery.

A Belgian priest and cosmologist named Georges Lemaitre published a paper reaching very similar conclusions two years earlier. It's a contentious issue among cosmologists, needless to say.

The problem was, Lemaitre's paper was in French, and appeared in a rather obscure journal: Annals of the Brussels Scientific Society. This limited its distribution throughout the scientific community (at least initially).

Yet even when his paper was finally translated and broadly disseminated, certain key elements went missing, sparking rumors that prominent scientists -- Sir Arthur Eddington, perhaps, or even Hubble himself -- had deliberately "censored" Lemaitre's paper to ensure Hubble's scientific legacy.

What happened? The answer might lie in a new article in Nature by cosmologist and author Mario Livio.

It's a long, complicated story, but here's the CliffsNotes version...

In the late 1920s, astronomer Edwin Hubble was studying distant galaxies at the Carnegie Observatories in Pasadena, home of the spanking new 100-inch Hooker telescope on Mount Wilson.

He measured the brightness of so-called Cepheid variable stars -- a type of periodically pulsing star -- based on the "Period-Luminosity Relation" discovered by Henrietta Swan Leavitt. Basically, if you know how long it takes for the star to go from bright to dim, this will tell you how bright it actually is. And once you know that, you have a means of measuring distance.

So Hubble was able to deduce the relative distance of the galaxies. He combined those observations with data collected in 1912 by Vesto Slipher. Slipher is usually credited with being the first to notice that the light the galaxies emitted had a pronounced “shift” toward the red end of the electromagnetic spectrum, indicating that they were moving away from earth.

Next Hubble plotted the velocity (indicated by the redshift) against relative distance, to get the graph at the top of this post. To a casual observer, it might seem like a random number of points scattered about, with some clustering hinting at a possible pattern.

But Hubble wasn't a casual observer, he was a frickin' genius. He looked at that graph and drew a straight line through all those data points. As telescope resolutions improved over the ensuing decades, Hubble's half-intuitive leap proved correct. Plot the same data today, and the points will fall neatly along the line Hubble drew.

In mathematical terms, that straight line indicates a linear function. That is, the redshift of distant galaxies increased as a linear function of their distance. Hubble reasoned (correctly) that the longer the light has been traveling, the more time there has been for space to expand, and hence the greater the red shift of the light’s wavelength.

So he proposed a law: the greater the distance between any two galaxies, the greater their relative speed of separation. Based on that law, he arrived at an inescapable conclusion: the cosmos was still expanding. And that, of course, changed everything in the field of cosmology.

Now back to Lemaitre.

The academic quibbling usually hinges on whether Lemaitre fully derived Hubble's law on his own from actual observational data, or limited his analysis to theoretical predictions. Lemaitre did rely on data, it turns out -- the same redshift data from Slipher's observations, combined with estimates of galaxy distances inferred from Hubble's own observations, published in 1926. And he also correctly concluded that this meant the universe was expanding, not static.

Sean Carroll wrote about this over at Cosmic Variance back in 2007:

    Lemaitre didn’t have very good data (and what he did was partly from Hubble, I gather). And for whatever reason, he did not plot velocity vs. distance. Instead, he seems to have taken the average velocity (which was known since the work of Vesto Slipher to be nonzero) and divided by some estimated average distance! If Hubble’s Law — the linear relation between velocity and distance — is true, that will correctly get you Hubble’s constant, but it’s definitely not enough to establish Hubble’s Law. If you have derived the law theoretically from the principles of general relativity applied to an expanding universe, and are convinced you are correct, maybe all you care about is fixing the value of the one free parameter in your model. But I think it’s still correct to say that credit for Hubble’s Law goes to Hubble — although it’s equally correct to remind people of the crucial role that Lemaitre played in the development of modern cosmology.

Eventually, of course, Lemaitre's crucial role was recognized: among others, Eddington published a long commentary on the work in 1930, calling it "brilliant." Thanks to Eddington, Lemaitre's original paper was translated and published again in 1931.

Oddly, however, some of his original calculations -- the ones that specifically related to the Hubble Constant -- were omitted. When this was discovered in 1982, speculation ran rampant, as science historians debated whether the omission had been deliberate, to preserve Hubble's claim to the discovery, or merely done in error.

Now Livio has weighed in on the controversy with the results of his own investigation in the matter in the Nov. 10th issue of Nature. He sifted through hundreds of letters preserved by the Royal Astronomical Society, along with minutes from the society's meetings and other archival materials.

Read more at Discovery News

We Are Hardwired to Walk

Watching a toddler take his first steps, it's obvious he's learned through observation and encouragement. But are our brains specially wired to learn this important behavior so early on?

Scientists are beginning to think so, according to one article published in the journal Science.

By looking at the body's neural circuitry in rats, humans and other animals, researchers pieced together that the process of learning to move around looks similar across species, despite most mammals moving on four legs and Homo sapiens stepping with two. The finding indicates that humans' innate ability to walk has a lengthy evolutionary history.

Previously, neuroscience experts thought pathways in the nervous system changed dramatically during human development, allowing new pathways to replace the deeply -rooted connections shared with other mammals. Not so, says lead researcher Francesco Lacquaniti, according to one article in The Atlantic. He provided an analogy comparing learning to walk with learning to drive a stick shift car. New drivers first learn the basic gears, but then add more with time. Yet even the most advanced drivers still need the first gear to drive. The same principle applies to learning to walk, with humans and animals sharing a common circuitry and gradually building on it in different ways.

Instead, toddlers continue to use these primitive connections in muscles, adding to them as they become more skilled at walking. In the study, Lacquaniti and colleagues looked at the electrical activity in muscles in newborns, toddlers, preschoolers and adults. They found the same connections were at play among cats, guineafowl, non-human primates and rats as well.

Read more at Discovery News

Earthquake-Proof Bridge Being Built In San Francisco

Within the next 30 years, a major earthquake with a magnitude of 6.7 or higher is expected to hit San Francisco. That's why the Bay Bridge, which connects San Francisco and Oakland, is undergoing major seismic renovations.

During 1989's Loma Prieta Earthquake, which registered 6.9 on the Richter scale, a section of the Bay Bridge collapsed, killing a motorist. Since then, major studies were conducted to determine if California's largest bridges were seismically safe.

Results of those studies showed the Bay Bridge -- which is bisected by Yerba Buena Island -- needed major improvements. A one-mile stretch on the west span needed three on- and off-ramps replaced, while the entire east span needed to be completely replaced.

Construction began in 2006 on a 2.2. mile stretch. Its main architectural feature will be a single-tower Self-Anchored Suspension span (SAS). When completed in late 2013, its 1,263-foot main span length will make it the longest, single-tower, self-anchored suspension bridge in the world.

Enhancing the bridge's form and function is the 525-foot single tower that is capable of withstanding a major earthquake. The steel tower is actually composed of four separate towers that are connected by shear link beams designed to move separately and act as shock absorbers in the event of a quake.

Also unique to new SAS is that one continuous main cable will help support the deck, as opposed to traditional suspension bridges that have two separate main cables.

This new design will include a nearly one-mile-long main cable anchored on the Oakland side of the bridge. It will then be carried over the single tower and, as it extends down, the cable will loop around two decks and their foundations on Yerba Buena Island, and back to the original anchor.

This compresses the entire span and allows for a level of cable tension to be sustained. In traditional suspension spans, any tension in the main cables is resisted by anchor points in the soil.

The estimated $6.281 billion project will also feature cantilevered bicycle and pedestrian paths and special lighting to accentuate the bridge's asymmetric design.

Read more at Discovery News