Oct 4, 2014
Engraved on a glass plate (called a paten) which dates back to the 4th century A.D., Jesus is depicted beardless and with short, curly hair. He wears what appears to be a philosopher’s toga and is flanked by two equally beardless male characters, thought to be the apostles Peter and Paul. All men have halos over their heads.
The plate, which measures 8.6 inches in diameter, is believed to have held Eucharistic bread in early Christian rituals. It was unearthed, broken in several fragments, inside a religious building in the ancient town of Cástulo in Andalusia.
According to Marcelo Castro, head of the FORVM MMX excavation project, the building was erected in the second half of the fourth century A.D. and abandoned about a century later.
“We know it dates back to the 4th century, in part because popes in the following centuries ordered all patens to be made out of silver,” Castro told The Local.
The dating coincides with the rule of Roman emperor Constantine, who ended the persecutions of Christians.
Representing the earliest depiction of Jesus found in Spain, the glass plate features greenish hues and is in an excellent state of preservation. Archaeologists managed to piece together 81 percent of its original area.
According to Castro, the plate is in line with the Christ in Majesty iconography. Copying Roman and Byzantine styles, the early Christian artists always portrayed Jesus in the center of the composition, often flanked by other sacred characters.
In the glass paten, Jesus holds the Cross in one hand — a symbol of the resurrection — and the Holy Scriptures in the other. Both the figures on his sides, possibly the apostles Peter and Paul, carry a roll in their hands.
Read more at Discovery News
It’s part of a basic human urge to communicate, said Harold G. Koenig, director of the Center for Spirituality, Theology and Health at Duke University and a professor of psychiatry. And people may be even more likely to stereotype when it comes to religion, Koenig said, because of the intense passion around the subject.
It’s also part of human nature to categorize, said Stephanie Madon, a professor of psychology at Iowa State. In fact, it’s an essential component to learning from experience.
“I have here on my desk a pencil,” she said. “The minute I see it, I recognize that, 'A ha! It is a pencil!' based on certain features I recognize. Now, I’ve been exposed to a whole host of knowledge about pencils -- I can sharpen them, they probably have an eraser -- so there are inferences I can make after I’ve categorized it as a pencil. The alternative is I see it lying there and I don’t know what it is, so I have to look at it and study it and figure out what it will offer me. You can see how inefficient it would be to get through a day.”
Take an early human who consumed a poisonous berry plant and got sick. The person may generalize that experience and avoid similar plants in the future. Of course, not all berries are poisonous.
Still, that "overuse of a rule was probably pretty good," Madon said. "It’s more beneficial than harmful to the berry eater because if you make a mistake and it’s not poisonous, well, no harm, no foul. But if you don’t apply the rule, you might get very sick or die."
In the modern world, people are able to make the subtle distinction between categorization and stereotyping.
So while it made good sense for ancient humans not to eat that berry, it doesn’t make sense for an employer to hire a man instead of a woman because he thinks men are better leaders, Madon said. In fact, categorization and stereotyping gets a lot dicier when moving from objects to people.
“There’s a tremendous variability between people of any group,” Koenig said. “To pin a label on a certain person when someone else of that race or ethnicity or religion does something stupid is just not accurate. Equating ISIS with all Muslims is just flat out wrong. It’s far beyond being even remotely sensible for anyone who knows anything about the Muslim religion and what is in the Koran.”
Controlling that urge to generalize and stereotype in today’s society is critical to living together peacefully, Koenig said.
“Statements (like Maher’s) can incite people to do harm to others,” Koenig said.
Even making an accurate assumption based on a stereotype can be offensive, Madon said.
Read more at Discovery News
Oct 3, 2014
The procedure was apparently done when a mother's life was in danger or the fetus had already died.
The investigators found the mummy after a devastating magnitude-6.3 earthquake occurred in L'Aquila in central Italy on April 6, 2009. The earthquake resulted in more than 300 deaths and damaged many buildings in the nearby area, including the historical St. John the Evangelist church in the village of Casentino. The floor of the church partially collapsed, exposing underground rooms holding mummified human bodies, which included the newfound fetus that dates back to 1840, according to the researchers' estimates.
When the researchers examined the fetus mummy using a radiograph, they saw a fetal skeleton that was not fully connected or articulated, which means that some of the bones were not in the exact same position to each other as they likely were when the fetus was alive. They were not able to establish the sex of the fetus, as they could not determine the morphology of its pelvic and jaw bones, which scientists use to identify sexual characteristics of skeletons. The researchers did estimate the fetus was at 29 weeks of development inside its mother's womb.
A few features of the mummy suggested that an operation had taken place. The fetus' skull had been dissected in several places and disconnected from the spine, while its arms had been separated from the rest of the body at the joints, none of which typically occurs in the process of post-mortem examinations. All of these characteristics "strongly suggest a case of embryotomy," which was a procedure that occurred before removing the fetus from the womb, study author Ruggero D'Anastasio of University Museum at University of Chieti, Italy, told Live Science.
This likely case of embryotomy "is the only anthropological proof of this surgical practice up to now in this geographical region," he added.
Embryotomy was a common practice in ancient times, D'Anastasio said. The procedure was practiced in Alexandria and then in Rome during the first and second centuries, the researchers wrote in the study. Physicians typically performed it when a mother's life was threatened due to delivery complications or when the fetus was already thought to be dead in the womb.
According to some reports, however, "embryotomy was the most extreme method of abortion during the medieval period," they wrote.
The remains of this fetus had been reassembled to match its anatomic shape, including the fragments of the skull being placed at the top of the mummy inside a headgear. The careful reassembly and dressing of the fetus indicates a high sense of compassion for the death of unborn children within the local community at the time, the researchers said.
The other human remains found at the site likely date back to the 19th century or earlier, as confirmed by a scientific method of age determination called radiocarbon dating and information gathered from personal objects. Those items include rings and rosary beads, shoes and clothes, as well as the textiles and shrouds used for wrapping the mummified bodies.
Read more at Discovery News
With the first case of Ebola diagnosed in the country confirmed earlier this week, people are getting nervous. But Ebola is very unlikely to be a problem or cause a major outbreak here. One of the main reasons is that it is not as easily transmitted as other diseases. It does not travel through the air like influenza—to be infected you must come into contact with fluids from an infected person.
Even more importantly, until a person is showing signs of being sick—with symptoms like fever and nausea—they are NOT contagious.
Still, some are worried about the plane the infected man traveled on before he became symptomatic, and others are worried about coming into contact with his relatives in Dallas who’ve been in the same house as he has, but don’t yet appear to be sick.
To help explain why these fears are unnecessary, we’ve taken a closer look at what the virus does in the human body, from transmission to infection to illness and death.
“The virus doesn’t easily go from one person to the next. It seems like it does, maybe, because Ebola is scary. It is unknown and has a high fatality rate and requires isolation or quarantine and has no known cure,” said biochemist Sharon Crary, of DePauw University. Crary studies the Ebola virus and worked with the CDC’s Viral Special Pathogens Branch, where she was part of the response team for the 2000 Ebola outbreak in Gulu, Uganda.
Ebola isn’t anywhere near as contagious as the flu, for example. Or measles, which is much more of a threat in the United States now that people are no longer routinely vaccinating their children. Scientists estimate that one person infected with measles can transmit the disease to as many as 18 others; for Ebola, that number is around two.
This is because unlike influenza or measles, Ebola isn’t very stealthy. It can’t spread through the air, and it isn’t contagious before symptoms first show up, when a person might unknowingly be a walking disease distributor. Rather, the Ebola virus spreads through infected bodily fluids—such as blood, vomit, saliva, semen and feces—which need to come into direct contact with a mucous membrane (such as the inside of your eyelids, mouth, or nose) or a bit of broken skin.
Still, if you’re a health care worker in West Africa, this is a serious concern, especially because tiny, unnoticed abrasions on the skin can be a portal for viral particles (hence the need for gloves and moon suits). In regions without the necessary supplies, education or infrastructure to halt the spread of the disease, outbreaks can be catastrophic. This is what’s happening in the West African countries of Liberia, Guinea, and Sierra Leone, where more than 3,300 people have died since December.
Though it is not that easily transmitted between people, the Ebola virus (Zaire ebolavirus) is frighteningly deadly: The average fatality rate is around 50 percent, but some strains kill as many as 90 percent of the people infected. There’s no specific treatment for Ebola, either. As the virus gradually claims control of a victim, it ignites a hemorrhagic fever that sometimes comes with horrific symptoms, including bloody diarrhea and vomit.
Ebola virus particles are long and skinny, and look like lethal microscopic noodles. When they get inside a person, the particles attack the immune system, liver, kidneys, and the cells that line blood vessels.
Once inside a cell, the virus begins to wage war. First, it makes many copies of its genome. Then, it hijacks the machinery that would normally help the host cell make its own proteins, and turns that into a viral protein production factory. These proteins then self-assemble into mature virus particles, which slip through the cell’s membrane and head off in search of more cells to infect.
“This cycle continues so the number of infected cells in a human increases exponentially, ” Crary said.
And it isn’t until these symptoms show up that a person becomes infectious. Scientists aren’t quite sure why this is, but studies in primates have shown that there are no viral particles in blood plasma before the onset of symptoms (in monkeys infected with Ebola, this tends to happen around three days post-exposure). Early, pre-symptomatic viral loads were the highest in the spleen and lymph nodes—things that would be very, very tricky to come into contact with.
“It seems to take a lot of virus particles to exist inside a patient before that virus starts entering the bodily fluids to be accessible to another person,” Crary said. “And this high virus [concentration] doesn’t happen until later in infection, when symptoms are already starting to show.”
This is the simple reason you can’t catch Ebola by sharing an airplane, or a dinner table, or a house, with someone who isn’t showing signs of the disease. However, it appears that some people are worried about riding in the same airplanes that carried the first U.S. Ebola patient from Liberia to Texas, despite the fact that the patient was not sick while he was traveling.
“Even though health officials maintain there is no risk to passengers, if you were a passenger on a plane that had carried an Ebola victim, it might be something you would want to know,” claims a story from ABC News
In reality, the information is completely inconsequential.
“The man was not symptomatic,” Crary said. “He didn’t have enough virus in his body to be able to be shedding any virus from his body. So there is simply no way that there is any virus on that plane that he was on.”
Sickness and Death
It wasn’t until the patient had been in Texas for several days that he began showing symptoms—about nine days after doctors suspect he was infected. Normal incubation periods range from two days to three weeks, with the majority of patients showing signs of illness between seven and 10 days after exposure, says mathematical epidemiologist Gerardo Chowell-Puente of Arizona State University.
Though these early symptoms can mimic the onset of the flu, what’s going on inside a patient’s body is very different from what happens with an influenza virus. At this point, an Ebola patient’s liver is being attacked, producing severe abdominal pain. Their blood vessels are gradually being broken down, which can lead to massive amounts of both internal and external bleeding. Organ failure might be setting in. As fluids leak from blood vessels and organs and accumulate in the body, blood pressure drops. Usually, it’s a deadly combination of abyssal blood pressure, electrolyte imbalance, and organ failure that delivers the final blow.
Nobody knows for sure how long the Ebola virus can survive outside a host. But 2007 study suggests that viral particles can survive for at least six hours at sub-Saharan Africa room temperatures—only in fluids like blood. But what we do know is that the dead are potent viral incubators that remain infectious for days, and disease transmission during traditional funeral rites is one of the ways this West Africa outbreak has persisted.
Read more at Wired Science
|Different strains of yeast grown under identical conditions develop different mutations but ultimately arrive at similar evolutionary endpoints.|
Many biologists argue that it would not, that chance mutations early in the evolutionary journey of a species will profoundly influence its fate. “If you replay the tape of life, you might have one initial mutation that takes you in a totally different direction,” Desai said, paraphrasing an idea first put forth by the biologist Stephen Jay Gould in the 1980s.
Desai’s yeast cells call this belief into question. According to results published
in Science in June, all of Desai’s yeast varieties arrived at roughly the same evolutionary endpoint (as measured by their ability to grow under specific lab conditions) regardless of which precise genetic path each strain took. It’s as if 100 New York City taxis agreed to take separate highways in a race to the Pacific Ocean, and 50 hours later they all converged at the Santa Monica pier.
The findings also suggest a disconnect between evolution at the genetic level and at the level of the whole organism. Genetic mutations occur mostly at random, yet the sum of these aimless changes somehow creates a predictable pattern. The distinction could prove valuable, as much genetics research has focused on the impact of mutations in individual genes. For example, researchers often ask how a single mutation might affect a microbe’s tolerance for toxins, or a human’s risk for a disease. But if Desai’s findings hold true in other organisms, they could suggest that it’s equally important to examine how large numbers of individual genetic changes work in concert over time.
|Michael Desai, a biologist at Harvard University, uses statistical methods to study basic questions in evolution.|
The key strength in Desai’s experiment is its unprecedented size, which has been described by others in the field as “audacious.” The experiment’s design is rooted in its creator’s background; Desai trained as a physicist, and from the time he launched his lab four years ago, he applied a statistical perspective to biology. He devised ways to use robots to precisely manipulate hundreds of lines of yeast so that he could run large-scale evolutionary experiments in a quantitative way. Scientists have long studied the genetic evolution of microbes, but until recently, it was possible to examine only a few strains at a time. Desai’s team, in contrast, analyzed 640 lines of yeast that had all evolved from a single parent cell. The approach allowed the team to statistically analyze evolution.
|To efficiently analyze many strains of yeast simultaneously, scientists grow them on plates like this one, which has 96 individual wells.|
Desai’s plan was to track the yeast strains as they grew under identical conditions and then compare their final fitness levels, which were determined by how quickly they grew in comparison to their original ancestral strain. The team employed specially designed robot arms to transfer yeast colonies to a new home every 12 hours. The colonies that had grown the most in that period advanced to the next round, and the process repeated for 500 generations. Sergey Kryazhimskiy, a postdoctoral researcher in Desai’s lab, sometimes spent the night in the lab, analyzing the fitness of each of the 640 strains at three different points in time. The researchers could then compare how much fitness varied among strains, and find out whether a strain’s initial capabilities affected its final standing. They also sequenced the genomes of 104 of the strains to figure out whether early mutations changed the ultimate performance.
|Fluid-handling robots like this one make it possible to study hundreds of lines of yeast over many generations.|
But because of the small scale of such studies, it wasn’t clear to Desai whether these cases were the exception or the rule. “Do you typically get big differences in evolutionary potential that arise in the natural course of evolution, or for the most part is evolution predictable?” he said. “To answer this we needed the large scale of our experiment.”
As in previous studies, Desai found that early mutations influence future evolution, shaping the path the yeast takes. But in Desai’s experiment, that path didn’t affect the final destination. “This particular kind of contingency actually makes fitness evolution more predictable, not less,” Desai said.
Desai found that just as a single trip to the gym benefits a couch potato more than an athlete, microbes that started off growing slowly gained a lot more from beneficial mutations than their fitter counterparts that shot out of the gate. “If you lag behind at the beginning because of bad luck, you’ll tend to do better in the future,” Desai said. He compares this phenomenon to the economic principle of diminishing returns — after a certain point, each added unit of effort helps less and less.
Scientists don’t know why all genetic roads in yeast seem to arrive at the same endpoint, a question that Desai and others in the field find particularly intriguing. The yeast developed mutations in many different genes, and scientists found no obvious link among them, so it’s unclear how these genes interact in the cell, if they do at all. “Perhaps there is another layer of metabolism that no one has a handle on,” said Vaughn Cooper, a biologist at the University of New Hampshire who was not involved in the study.
Read more at Wired Science
|The steamer duck uses those specialized orange knobs on its wings to positively pummel anything unfortunate enough to cross it. Except these rocks. Steamer ducks are OK with rocks.|
From time to time the steamer would drag the shoveler under, then resurface and continue beating the tar out of it as the female watched. At one point he shuffled over to her, but after 30 seconds returned to his victim and punched the poor critter 15 to 20 more times. “He then released the limp body of the shoveler,” wrote Nuechterlein, “pecked at it, and released it again.” At last he returned to the female for good, calling to her while she stretched, and the two flew off together. The shoveler eventually regained consciousness, and though seriously crippled, struggled to shore. It died 15 minutes later.
This is the avian version of Bloodsport, only without all of the terrible yet somehow endearing acting. The four species of steamer duck (so named for their penchant for flapping and running along the surface, kicking up water like steamboats) in South America are famous—at least in ornithological circles—for their brutality, getting all up in the grills of not just other steamers, but also other species in scrums lasting as long as 20 minutes. Why exactly they’ve evolved to be so aggressive, no one is yet sure.
|If a flying steamer duck ever makes this face at you, don’t confuse it for friendliness. Steamer ducks ain’t got time for no friendliness.|
Now, had the ducks been guarding a nest, that’d be one thing, but McCracken couldn’t find one nearby. Indeed, Nuechterlein noted in his paper that there needn’t be eggs around to get the ducks riled up and defensive. They’re simply really, really ornery. And that may be because they can take the abuse—by being built like feathered tanks.
You see, their heads and necks are relatively massive for a duck, and they’re equipped with thickened skin to handle the abuse. Because they’re so hardy, they reduce the risk of injury that would normally keep birds from engaging in such vicious battle. (As a rule, in the animal kingdom you don’t want to fight if you don’t absolutely have to. Battling for the right to mate or eat is of course important, but it’s really no use if you end up dead. It’s why there’s all kinds of non-contact battling going on out there, with fancy displays or calls, or even the puffed chest and unimaginative obscenities of the North American dude bro.)
“They’re enormous birds,” said McCracken, adding that males can reach 10 pounds (the famous mallard you’ve no doubt seen around your local lake tops out at 3 pounds). “You don’t want one of these things going after you.”
|A white-headed steamer ducks staring down the ocean for looking at it funny.|
Accordingly, bird species unfortunate enough to share a habitat with the steamer duck seem to know their place. When Nuechterlein was making his observations back in the ’80s, he and his colleague noticed silvery grebes and hooded grebes would suddenly skitter or dive en masse. “We puzzled over the cause of these ‘mass spooks’ in the otherwise unmolested flocks of grebes, for there were few predators and no source of human disturbance on the lake.” Only later did they notice the problem: a pair of steamer ducks approaching in a “submerged sneak” posture, with only the tops of their heads and the tips of their tails poking above the surface. They had become, in essence, the Jaws of the Andean lake.
The aforementioned public beating of the shoveler also could suggest aggressive behavior is part of winning the affection of a mate. The female did, after all, grow quite excited as the male pummeled his victim. If true, it would add yet another strange dimension to the exceedingly weird world of duck sex. It’s been well reported, so we don’t need to go into much detail here, but male ducks are notoriously forceful with their choice of mates, and in response females have evolved corkscrew vaginas that in some species twist the opposite direction of the corkscrew penis, all to give themselves more control over the reproductive process. Choosing a male based on how well he assaults another duck, though, would seem to select for such unwanted aggressiveness.
The steamer ducks’ brazenness is all the more impressive when you consider three of the four species have grown so big they’ve lost the ability to fly. This would seem unfortunate and rather embarrassing, but we humans tend to romanticize flight. In the natural world, if you don’t use it, you lose it. There’s no point expending energy and resources developing something you aren’t going to use, much less burning vast amounts of energy to fly.
So the flightless species of steamer duck have apparently found it evolutionarily advantageous to stick to terra firma. This is partly due to the relative lack of mammalian predators to flee from (though recently the release of invasive minks, which are fond of bird eggs, has been threatening certain populations). “But they’re also hard to get at,” said McCracken. “If you’re an Andean fox,” which weighs just barely more than these birds, “going after a [10-pound] steamer duck, you’re not going to have much luck.”
|A Magellanic steamer duck, so named because one once attacked Ferdinand Magellan. Yeah, that’s probably not true. Never hurts to dream, though.|
Read more at Wired Science
Oct 2, 2014
Made from marble brought from the island of Thasso, like most of the features uncovered so far in the underground space, the door fragments were found as archaeologists removed dirt from the second chamber.
According to Katerina Peristeri, the excavation’s director, the discovery leaves no doubt the structure is indeed a tomb dating to the time of Alexander the Great of Macedonia.
“Based on our findings, we are absolutely sure about our dating to the last quarter of the 4th century B.C.,” Peristeri said.
She hinted their dating relies on strong yet unpublished findings.
“We give information out to provide a clear picture [of the excavation]. However, not all the material is coming out in press releases,” Peristeri said.
Leading to the tomb’s third chamber, the marble door features a double row of dots down its center. The dots imitate nail heads, a feature common on Macedonian tomb doors.
A hinge was also discovered on the western side of the door.
“What is particularly unusual here is that the door was in two sections and hinged,” Dorothy King, a classical archaeologist not involved in the excavation, wrote in her blog.
“It was designed to open rather than merely be a ‘fake’ door designed to look like one as seen in most other Macedonian tombs,” she said.
She noted that temples had doors that opened and closed, “but they tended to be either wood inlaid with ivory or wood covered in bronze,” King said.
Behind the two fully unearthed Caryatids (female statue) and in front of the door, Peristeri’s team also found bronze and iron nails. It’s not clear whether they belonged to the funerary carriage or something else.
As for the broken marble door, Peristeri believes it collapsed either as a result of the Bulgarian army’s bombing in 1913 or as the consequence of a severe earthquake that rumbled in Amphipolis in the 6th century A.D.
Read more at Discovery News
Exotic matter: A closer look at the perfect fluid sheds light on what happened microseconds after the Big Bang
The multi-institutional team known as the JET Collaboration, led by researchers at the U.S. Department of Energy's Lawrence Berkeley National Lab (Berkeley Lab), published their results in a recent issue of Physical Review C. The JET Collaboration is one of the Topical Collaborations in nuclear theory established by the DOE Office of Science in 2010. JET, which stands for Quantitative Jet and Electromagnetic Tomography, aims to study the probes used to investigate high-energy, heavy-ion collisions. The Collaboration currently has 12 participating institutions with Berkeley Lab as the leading institute.
"We have made, by far, the most precise extraction to date of a key property of the quark-gluon plasma, which reveals the microscopic structure of this almost perfect liquid," says Xin-Nian Wang, physicist in the Nuclear Science Division at Berkeley Lab and managing principal investigator of the JET Collaboration. Perfect liquids, Wang explains, have the lowest viscosity-to-density ratio allowed by quantum mechanics, which means they essentially flow without friction.
Hot Plasma Soup
To create and study the quark-gluon plasma, nuclear scientists used particle accelerators called the Relativistic Heavy-ion Collider (RHIC) at the Brookhaven National Laboratory in New York and the Large Hadron Collider (LHC) at CERN in Switzerland. By accelerating heavy atomic nuclei to high energies and blasting them into each other, scientists are able to recreate the hot temperature conditions of the early universe.
Inside protons and neutrons that make up the colliding atomic nuclei are elementary particles called quarks, which are bound together tightly by other elementary particles called gluons. Only under extreme conditions, such as collisions in which temperatures exceed by a million times those at the center of the sun, do quarks and gluons pull apart to become the ultra-hot, frictionless perfect fluid known as quark-gluon plasma.
"The temperature is so high that the boundaries between different nuclei disappear so everything becomes a hot-plasma soup of quarks and gluons," says Wang. This ultra-hot soup is contained within a chamber in the particle accelerator, but it is short-lived -- quickly cooling and expanding -- making it a challenge to measure. Experimentalists have developed sophisticated tools to overcome the challenge, but translating experimental observations into precise quantitative understanding of the quark-gluon plasma has been difficult to achieve until now, he says.
In this new work, Wang's team refined a probe that makes use of a phenomenon researchers at Berkeley Lab first theoretically outlined 20 years ago: energy loss of a high-energy particle, called a jet, inside the quark gluon plasma.
"When a hot quark-gluon plasma is generated, sometimes you also produce these very energetic particles with an energy a thousand times larger than that of the rest of the matter," says Wang. This jet propagates through the plasma, scatters, and loses energy on its way out.
Since the researchers know the energy of the jet when it is produced, and can measure its energy coming out, they can calculate its energy loss, which provides clues to the density of the plasma and the strength of its interaction with the jet. "It's like an x-ray going through a body so you can see inside," says Wang.
One difficulty in using a jet as an x-ray of the quark-gluon plasma is the fact that a quark-gluon plasma is a rapidly expanding ball of fire -- it doesn't sit still. "You create this hot fireball that expands very fast as it cools down quickly to ordinary matter," Wang says. So it's important to develop a model to accurately describe the expansion of plasma, he says. The model must rely on a branch of theory called relativistic hydrodynamics in which the motion of fluids is described by equations from Einstein's theory of special relativity.
Over the past few years, researchers from the JET Collaboration have developed such a model that can describe the process of expansion and the observed phenomena of an ultra-hot perfect fluid. "This allows us to understand how a jet propagates through this dynamic fireball," says Wang.
Employing this model for the quark-gluon plasma expansion and jet propagation, the researchers analyzed combined data from the PHENIX and STAR experiments at RHIC and the ALICE and CMS experiments at LHC since each accelerator created quark-gluon plasma at different initial temperatures. The team determined one particular property of the quark-gluon plasma, called the jet transport coefficient, which characterizes the strength of interaction between the jet and the ultra-hot matter. "The determined values of the jet transport coefficient can help to shed light on why the ultra-hot matter is the most ideal liquid the universe has ever seen," Wang says.
Read more at Science Daily
Developed using a scientific model that captures gravity measurements of the ocean seafloor, the new map extracts data from the European Space Agency's (ESA) CryoSat-2 satellite, which primarily captures polar ice data but also operates continuously over the oceans, and Jason-1, NASA's satellite that was redirected to map the gravity field during the last year of its 12-year mission.
Combined with existing data and drastically improved remote sensing instruments, the new map, described in the journal Science, has revealed details of thousands of undersea mountains, or seamounts, extending a kilometer or more from the ocean bottom. The new map also gives geophysicists new tools to investigate ocean spreading centers and little-studied remote ocean basins.
"The kinds of things you can see very clearly now are abyssal hills, which are the most common land form on the planet," said David Sandwell, lead scientist of the paper and a geophysics professor in the Cecil H. and Ida M. Green Institute of Geophysics and Planetary Physics (IGPP) at Scripps.
The authors of the study say the map provides a new window into the tectonics of the deep oceans. Previously unseen features in the map include newly exposed continental connections across South America and Africa, and new evidence for seafloor spreading ridges at the Gulf of Mexico that were active 150 million years ago and are now buried by mile-thick layers of sediment.
"One of the most important uses of this new marine gravity field will be to improve the estimates of seafloor depth in the 80 percent of the oceans that remains uncharted or is buried beneath thick sediment," the authors say in the report.
"Although CryoSat-2's primary mission is in the cryosphere, we knew as soon as we selected its orbit that it would be invaluable for marine geodesy, and this work proves the point," said Richard Francis, a coauthor of the paper and project manager for the development of CryoSat-2 at the European Space Agency, and honorary professor in the Department of Earth Sciences at University College London.
The new map also provides the foundation for the upcoming new version of Google's ocean maps to fill large voids between shipboard depth profiles.
Read more at Science Daily
A team of researchers from the University of Pennsylvania and the University of California, Santa Barbara, has now shown how giant clams use these structures to thrive, operating as exceedingly efficient, living greenhouses that grow symbiotic algae as a source of food.
This understanding could have implications for alternative energy research, paving the way for new types of solar panels or improved reactors for growing biofuel.
The study was led by Alison Sweeney, assistant professor in the Department of Physics and Astronomy in Penn's School of Arts & Sciences, and Daniel Morse, professor emeritus in UCSB's Department of Molecular, Cellular and Developmental Biology and Director of its Marine Biotechnology Center. The team also includes lead author Amanda Holt, a postdoctoral researcher formerly at UCSB and now at Penn, as well as Sanaz Vahidinia of NASA's Ames Research Center and Yakir Luc Gagnon of Duke University.
It was published in the Journal of the Royal Society Interface.
"Many mollusks, like squid, octopuses, snails and cuttlefish," Sweeney said, "have iridescent structures, but almost all use them for camouflage or for signaling to mates. We knew giant clams weren't doing either of those things, so we wanted to know what they were using them for."
While the true purpose of these iridescent structures, cells known as iridocytes, was not known, the team had a strong hypothesis. Like neighboring coral, giant clams are home to symbiotic algae that grow within their flesh. These algae convert the abundant sunlight of the clams' equatorial home into a source of nutrition but are not particularly efficient in the intense sunlight found on tropical reefs; sunlight at the latitude where these clams live is so intense that it can disrupt the algae's photosynthesis, paradoxically reducing their ability to generate energy.
The team members began their study hypothesizing that the clams' iridocytes were being used to maximize the usefulness of the light that reaches the algae within their bodies. They were first confounded by the relationship between these iridescent structures and the single-celled plants, until they realized that they had an incomplete picture of their geometry. When they made more precise cross sections of the clams, they found that the algae were organized into pillars, with a layer of iridocytes at the top.
"When we saw the complete picture, we understood that the pillars are oriented exactly the wrong way if you want to catch sunlight," Sweeney said. "That's where the iridocytes come into play."
The team relied on Amanda Holt and Sanaz Vahidinia to model exactly what was happening to the light once it passed through the iridocytes; the degree of disorder within these cells bore a resemblance to structures Vahidinia studies at NASA: the dust of Saturn's rings.
Their analysis suggested that the iridocytes would scatter many wavelengths of light in a cone-like distribution pointing deeper into the clam. Red and blue wavelengths, the most useful to the algae, spread the widest, impacting the sides of the pillars in which the single-celled plants were stacked.
To test this model, the team constructed fiber optic probes with spherical tips the size of an individual alga. Threaded through a section of clam flesh alongside the native algae, this spherical probe was able to detect the angled light scattered by the iridocytes, whereas a flat-tipped probe, only able to sense light shining straight down, detected nothing.
"We see that, at any vertical position within the clam tissue, the light comes in at just about the highest rate at which these algae can make use of photons most efficiently," Sweeney said. "The entire system is scaled so the algae absorb light exactly at the rate where they are happiest."
"This provides a gentle, uniform illumination to the vertical pillars consisting of the millions of symbiotic algae that provide nutrients to their animal host by photosynthesis," said Morse. "The combined effect of the deeper penetration of sunlight -- reaching more algae that grow densely in the 3-dimensional volume of tissue -- and the "step-down" reduction in light intensity -- preventing the inhibition of photosynthesis from excessive irradiation -- enables the host to support a much larger population of active algae producing food than possible without the reflective cells."
Read more at Science Daily
Oct 1, 2014
The paper, published in PLOS ONE, explains how now-extinct sabertooth cats likely killed their prey. The process, as it turns out, mirrored how can openers work -- specifically, the type of can opener with a long lever handle and a pointed triangular tip. You probably have such a device in a kitchen drawer.
The new research negates a prior theory about how sabertooth cats, which went extinct about 10,000 years ago, bit into prey. The discovery could even lead to a name change for the prehistoric ferocious felines.
Prior studies likened the cat's impressive canine teeth to knives, hence the word "saber." The theory held that the canine teeth were used to stab or slash the prey. Leaping onto its victim, the cat would plunge its upper canines into the prey, either eviscerating the animal or causing massive blood loss.
Other scientists, however, questioned whether the upper canines would have enough force to penetrate the hide of the prey without an opposing force from the lower jaw. This led to a widely accepted model called "the canine shear-bite." In this scenario, the cat used both its upper and lower jaws to bite the prey, but employed a downward nodding motion of its head to power the bite.
The new research counters this popular view. Geometric analysis, based on available sabertooth cat skeletons, determined that a downward motion of the cat's head would not increase the force of its bite. Given the cat's massively enlarged upper canines, how could it even produce enough force to close its jaws?
This is where the can opener mechanism comes in. The author of the new paper, Jeffrey Brown, calls it "the Class 1 Lever Model."
Brown, an independent researcher, believes that instead of the jaw muscles contracting to close the jaws, the cat may have immobilized its lower jaw against the neck of the prey, like the lug of a can-opener. Then, pushing with its forelimbs against the ground, the cat could elevate the base of its neck, rotating its head and canine teeth forward into the prey.
The mechanism is similar to the way in which an upward force against the arm of a can opener rotates the tip into a can.
Brown explained, "In the canine shear-bite, the cat's forelimbs restrain the prey and the neck powers the bite. In the Class 1 Lever Model there is an alternative method for restraining the prey, freeing the forelimbs to power the bite."
Read more at Discovery News
The study, reported in the Journal PLOS Biology, shows how nine dinosaurian wrist bones were reduced over millions of years of evolution to just four wrist bones in modern day birds.
"This discovery clarifies how dinosaur arms became bird wings," said one of the study's authors, Dr Alexander Vargas of the University of Chile in Santiago.
"It shows that some bones fused, other bones disappeared, and one bone disappeared and then reappeared in evolution."
Skeletal similarities between theropod dinosaurs and birds provide some of the strongest evidence showing how birds developed from dinosaurs. But the evolution of straight dinosaur wrists into hyperflexible wrists allowing birds to fold their wings when not flying, has remained a point of contention between palaeontologists and some developmental biologists.
Among the structures in question is a half-moon shaped wrist bone called the semilunate which is found in dinosaurs and looks very similar to a wrist bone also found in birds.
The semilunate originated as two separate dinosaur bones which eventually fused into a single bone. However some developmental biologists claim it evolved as a single bone in birds, and so isn't the same bone as that found in dinosaurs.
To help settle the debate, Vargas and colleagues examined the wrist bones of dinosaur fossils in the collections from several museums, and compared them to new developmental data from seven different species of modern birds.
"We developed a new technique called whole-mount immunostaining, which allows us to observe skeleton development better than ever before, including the expression of proteins inside embryonic cartilage," said Vargas.
The technique allowed the authors to determine that the embryonic semilunate in birds evolves as two separate cartilages which fuse into a single bone, consistent with what palaeontologists had been saying.
"These findings eliminate persistent doubts that existed over exactly how the bones of the wrist evolved, and iron out arguments about wrist development being incompatible with birds originating from dinosaurs," said Vargas.
The study also produced an interesting surprise for the research team when they discovered a wrist bone called the pisiform, which was present in early sauropod (four-legged, long-tailed, long-necked) dinosaurs, but had disappeared in later theropod (two-legged, two-armed) dinosaurs.
The authors found the pisiform had reappeared in early birds, probably as an adaptation for flight, where it allows transmission of force on the downstroke while restricting flexibility on the upstroke.
"We think the pisiform was lost when dinosaurs became bipedal," said Vargas. "Quadrupedal animals used this bone because they walk with their forelimbs, but bipedal dinosaurs no longer walked with their forelimbs and lost the bone. However they regained it when they began using their forelimbs for locomotion in flight."
Read more at Discovery News
There has been some debate as to how this vast feature — called Oceanus Procellarum, which measures around 1,800 miles wide — was created. But after using gravity data from NASA’s twin GRAIL spacecraft, researchers have found compelling evidence that it was formed in the wake of a mega volcanic eruption and not the location of a massive asteroid strike.
The key issue with understanding how the Procellarum basin could have formed is that the moon is pockmarked with billions of years worth of impact craters. These craters have excavated the lunar surface, wiping out features that could have pointed to Procellarum’s origins.
In new research published today in the journal Nature, geophysicist Maria Zuber, of Massachusetts Institute of Technology (MIT), used data from GRAIL to find the basin is actually of a polygonal shape, rather than a smooth circle (or oval) that is commonly associated with impact craters. Its edges are composed of straight edges linked at 120 degree angles.
GRAIL — an acronym for Gravity Recovery and Interior Laboratory — consisted of two spacecraft, one chasing the other, above the moon’s surface. Their mission started in January 2012 and ended, spectacularly, in the following December when they were deliberately steered to crash into the moon’s terrain.
During their mission, as one spacecraft orbited over a region of dense rock, the gravitational field of the moon would slightly increase, speeding the leading probe up. Likewise, when traveling over a less dense region, the leading spacecraft would slow down. As a result, the distance between the two spacecraft would vary, providing NASA with very precise data about the distribution of lunar gravity and, therefore, a density map of the hidden rock beneath the surface.
After discovering the density of rock represented a massive lava flow rather than a massive asteroid strike, Zuber’s team set out to model how such a huge quantity of lava could have spilled onto the surface, creating the basin we see today.
By simulating volcanic intrusions below the surface and interpreting how that gravitational signal may have been recorded by GRAIL, the researchers found that GRAIL recorded a similar rock density structure below Procellarum. Therefore, shortly after the moon had formed and cooled, a huge plume of molten rock was pushed up from the moon’s interior. The steep temperature difference between the basin and the surrounding rock caused the surface to contract, fracturing the lunar crust, creating routes for molten material to escape to the surface.
Read more at Discovery News
|A medieval bestiary’s depiction of a beaver hunt/testicle collection.|
Perhaps a bit taken aback by this gesture, you let it scurry away sans gonads, because a medieval hunter like you is only after the precious oil, known as castoreum, those organs bear. The beaver has quite cleverly just saved its own life.
Or at least according to any number of medieval bestiaries, often gorgeously illustrated tomes that cataloged nature’s critters—the real, the totally imagined, or the slightly embellished. (Interestingly, bestiaries noted that when pursued the wolf similarly chews off a tuft of hair on its back that humans covet as an aphrodisiac.) And like many creatures in these bestiaries, the beaver carried a moral lesson: If a fella wants to be chaste, he has to cut off his vices and throw them at the devil, who will then leave him alone. Which goes to show that they just don’t make moral lessons like they used to.
This tale begins with the ancient Egyptians, who had a hieroglyphic depicting a beaver chewing off his testicles as a representation of the punishment for adultery among humans in their society. In the West, it was Aesop who first wrote of the myth in his famous fables: “When pursued, the beaver runs for some distance, but when he sees he cannot escape, he will bite off his own testicles and throw them to the hunter, and thus escape death.” Pliny the Elder, the first great naturalist (though also a fairly reliable peddler of untruths), echoed this in his encyclopedia Natural History, which for hundreds and hundreds of years served as a trusted scientific authority.
|A beaver’s default demeanor is deviousness.|
Then there’s the matter of hunting beaver for food, which according to Gerald tastes like fish. This is super convenient if you’re Catholic, and you’re banned from eating any meat other than fish on Fridays. So according to Gerald, “in Germany and the arctic regions, where beavers abound, great and religious persons, in times of fasting, eat the tails of this fish-like animal, as having both the taste and color of fish.” (It’s worth noting that the same trick was supposedly once applied to the capybara of South America, the world’s largest rodent, weighing in at up to 150 pounds. It spends its days largely wading through swamps, so many Venezuelans consider the critter to be more fish than mammal. Indeed, legend goes that clergy there in the 1700s asked the Vatican to officially classify it as such.)
|That vaguely beaverish thing is in fact a beaver. You can tell from its insistence on biting its testicles off.|
OK, the testicles. Along comes the 17th century and with it a polymath by the name of Sir Thomas Browne, who had somewhat of a nose for sniffing out nonsense and ripping it to pieces. He notes quite rightly that a beaver’s testicles do not hang outside the body as ours do—they’re situated internally. “And, therefore, it were not only a fruitless attempt, but an impossible act, to eunuchate or castrate themselves; and might be an [sic] hazardous practice of art, if at all attempted by others.”
|Sir Thomas Browne: the look of a man who’s sick and tired of your silly misconceptions.|
Read more at Wired Science
Sep 30, 2014
Skeletons crushed under a collapsed roof depicted a scenario of death and destruction caused by the earthquake that hit Israel and the region in 363 A.D.
The ancient city of Hippos, known as Sussita in Hebrew (both names mean “horse”) was among the most damaged centers. However, it was another powerful quake, on Jan. 18, 749, that razed the city, leaving it covered in debris, never to be resettled.
“While the evidence of the final destruction are clear and dramatic, those of the 363 are less known and not as evident in the ruins of Hippos,” said Michael Eisenberg, director of the Hippos-Sussita project, an international enterprise affiliated with the Zinman Institute of Archaeology at the University of Haifa.
“The reason is rather simple. The city was rebuilt and some of the ruins cleared while others were buried as new building enterprises took place,” he added.
A mountaintop town overlooking the Sea of Galilee in northern Israel, Hippos was founded during the Hellenistic period, in the 2nd century B.C.
In Roman times it became known as one of the Decapolis, a group of 10 cities in Jordan, Israel and Syria which were regarded as centers of Greek and Roman culture. Hippos became a powerful city-state, allowed to mint its own coins, with the emblem of a horse on the back of each coin.
With its Graeco-Roman temples, its large marketplace and colonnaded streets, Hippos would have been for Jesus the “city set upon a hill” that “cannot be hidden.”
The city was prospering and was almost entirely Christian when the 363 quake violently struck its walls.
Eisenberg’s team found a number of skeletons crushed under a collapsed roof in the northern section of the Basilica, the largest structure in the city. Built at the end of the 1st century A.D. during the peak of Roman building in the city and the region, it served as marketplace and main seat of the judge.
Among the bones of the people killed in the collapse, the archaeologists found the skeleton of a woman with a golden pendant in the shape of a dove.
“Looking at the angle of the skeleton’s head we realized it was facing south towards the entrances to the basilica, about 140 feet away,” Eisenberg told Discovery News.
The skeletons could be dated to the 363 earthquake because of coins found trapped between the basilica floor and some architectural elements made of marble.
“The latest of those coins dated to 362 A.D. About three feet above the debris of the basilica we found Early Byzantine rooms dated by dozens of coins in the floors themselves to 383 A.D.,” Eisenberg said.
“It shows that major parts of the city were totally destroyed and neglected for a period of about 20 years,” he added.
Read more at Discovery News
The remote archipelagos of East Polynesia were among the last habitable places on Earth that humans were able to colonize. In New Zealand, human history only began around 1200-1300, when intrepid voyagers arrived by boat through several journeys over some generations.
A piece of that early heritage was recently revealed on a beach in New Zealand, when a 600-year-old canoe with a turtle carved on its hull emerged from a sand dune after a harsh storm. The researchers who examined the shipwreck say the vessel is more impressive than any other canoe previously linked to this period in New Zealand.
Separately, another group of scientists discovered a climate anomaly in the South Pacific during this era that would have eased sailing from central East Polynesia southwest to New Zealand. Both findings were detailed today (Sept. 29) in the journal Proceedings of the National Academy of Sciences.
The canoe was revealed near the sheltered Anaweka estuary, on the northwestern end of New Zealand's South Island.
"It kind of took my breath away, really, because it was so carefully constructed and so big," said Dilys Johns, a senior research fellow at the University of Auckland in New Zealand.
The hull measured about 20 feet (6.08 meters), long and it was made from matai, or black pine, found in New Zealand. The boat had carved interior ribs and clear evidence of repair and reuse. Carbon dating tests showed that the vessel was last caulked with wads of bark in 1400.
Johns and colleagues say it's likely that the hull once had a twin, and together, these vessels formed a double canoe (though the researchers haven't ruled out the possibility that the find could have been a single canoe with an outrigger). If the ship was a double canoe, it probably had a deck, a shelter and a sail that was pitched forward, much like the historic canoes of the Society Islands (a group that includes Bora Bora and Tahiti) and the Southern Cook Islands. These island chains have been identified as likely Polynesian homelands of the Maori, the group of indigenous people who settled New Zealand.
boat was surprisingly more sophisticated than the canoes described centuries later by the first Europeans to arrive in New Zealand, Johns told Live Science. At the time of European contact, the Maori were using dugout canoes, which were hollowed out from single, big trees with no internal frames. In the smaller islands of Polynesia, boat builders didn't have access to trees that were big enough to make an entire canoe; to build a vessel, therefore, they had to create an elaborate arrangement of smaller wooden planks.
The newly described canoe seems to represent a mix of that ancestral plank technology and an adaptation to the new resources on New Zealand, since the boat has some big, hollowed-out portions but also sophisticated internal ribs, Johns and colleagues wrote.
The turtle carving on the boat also seems to link back to the settlers' homeland. Turtle designs are rare in pre-European carvings in New Zealand, but widespread in Polynesia, where turtles were important in mythology and could represent humans or even gods in artwork. In many traditional Polynesian societies, only the elite were allowed to eat turtles, the study's authors noted.
A separate recent study examined the climate conditions that may have made possible the long journeys between the central East Polynesian islands and New Zealand. Scientists looked at the region's ice cores and tree rings, which can act like prehistoric weather stations, recording everything from precipitation to wind patterns to atmospheric pressure and circulation strength.
Because of today's wind patterns, scholars had assumed that early settlers of New Zealand would have had to sail thousands of miles from East Polynesia against the wind. But when the researchers reconstructed climate patterns in the South Pacific from the year 800 to 1600, they found several windows during the so-called Medieval Climate Anomaly when trade winds toward New Zealand were strengthened. (That anomaly occurred between the years 800 and 1300.)
Read more at Discovery News
The close-orbiting alien planet, known as WASP-18b, is apparently disrupting the magnetic field of its host star so much that the object is behaving like a much older star, researchers said.
"WASP-18b is an extreme exoplanet," study lead author Ignazio Pillitteri, of the Instituto Nazionale di Astrofisica (INAF)-Osservatorio Astronomico di Palermo in Italy, said in a statement. "It is one of the most massive hot Jupiters known and one of the closest to its host star, and these characteristics lead to unexpected behavior. The planet is causing its host star to act old before its time."
The star WASP-18, which lies about 330 light-years away, is about as massive as our own sun. The gas giant WASP-18b weighs in at more than 10 times the mass of Jupiter and completes one orbit around the star in less than 23 hours, leading scientists to classify it as a "hot Jupiter."
WASP-18b's tight orbit has led scientists to estimate that it may have only one million years of life or so remaining before it's destroyed by the parent star.
Pillitteri's team targeted WASP-18 with NASA's Chandra X-ray Observatory and found it to be relatively quiet — a characteristic of older stars. Young stars tend to be more active, with stronger magnetic fields, larger flares and more intense X-ray emission. Stellar activity is connected to rotation, a process that slows with age.
Observations of WASP-18 using Chandra revealed no X-ray emission. This by itself would suggest that the star has an age similar to the sun's 5 billion years, researchers said. However, Pillitteri and his team used other data as well as theoretical models to calculate that WASP-18 is actually just 500 million to 2 billion years old, and thus approximately 100 times less active than a star its age should be.
The difference, the researchers determined, is due to the planet.
"We think the planet is aging the star by wreaking havoc on its innards," said co-author Scott Wolk, of the Harvard-Smithsonian Center for Astrophysics in Massachusetts.
WASP-18b's strong gravitational pull may be disrupting the star's magnetic field, researchers said. The planet's tug exerts forces similar to those imposed on Earth's tides by the moon, but on a much larger scale.
The strength of a star's magnetic field depends on how much the hot gases within the star stir up its interior, a process known as convection. WASP-18 has a convection zone narrower than most stars, making it more vulnerable to the massive tidal forces exerted by WASP-18b, researchers said.
Read more at Discovery News
Gravity—yes, gravity—is the latest victim of climate change in Antarctica. That’s the stunning conclusion announced Friday by the European Space Agency.
“The loss of ice from West Antarctica between 2009 and 2012 caused a dip in the gravity field over the region,” writes the ESA, whose GOCE satellite measured the change. Apparently, melting billions of tons of ice year after year has implications that would make even Isaac Newton blanch. See the data visualized above.
To be fair, the change in gravity is very small. It’s not like you’ll float off into outer space on your next vacation to the Antarctic Peninsula.
The biggest implication is the new measurements confirm global warming is changing the Antarctic in fundamental ways. Earlier this year, a separate team of scientists announced that major West Antarctic glaciers have begun an “unstoppable” “collapse,” committing global sea levels to a rise of several meters over the next few hundred years.
Though we all learned in high-school physics that gravity is a constant, it actually varies slightly depending on where you are on the Earth’s surface and the density of the rock (or, in this case, ice) beneath your feet. During a four-year mission, the ESA satellite mapped these changes in unprecedented detail and was able to detect a significant decrease in the region of Antarctica where land ice is melting fastest.
Read more at Wired Science
Sep 29, 2014
Astrophysicists at the University of California, Santa Cruz (UCSC) and the University of Minnesota came to this conclusion after running a number of supercomputer simulations at the Department of Energy's (DOE's) National Energy Research Scientific Computing Center (NERSC) and Minnesota Supercomputing Institute at the University of Minnesota. They relied extensively on CASTRO, a compressible astrophysics code developed at DOE's Lawrence Berkeley National Laboratory's (Berkeley Lab's) Computational Research Division (CRD). Their findings were recently published in Astrophysical Journal (ApJ).
First-generation stars are especially interesting because they produced the first heavy elements, or chemical elements other than hydrogen and helium. In death, they sent their chemical creations into outer space, paving the way for subsequent generations of stars, solar systems and galaxies. With a greater understanding of how these first stars died, scientists hope to glean some insights about how the Universe, as we know it today, came to be.
"We found that there is a narrow window where supermassive stars could explode completely instead of becoming a supermassive black hole -- no one has ever found this mechanism before," says Ke-Jung Chen, a postdoctoral researcher at UCSC and lead author of the ApJ paper. "Without NERSC resources, it would have taken us a lot longer to reach this result. From a user perspective, the facility is run very efficiently and it is an extremely convenient place to do science."
The Simulations: What's Going On?
To model the life of a primordial supermassive star, Chen and his colleagues used a one-dimensional stellar evolution code called KEPLER. This code takes into account key processes like nuclear burning and stellar convection. And relevant for massive stars, photo-disintegration of elements, electron-positron pair production and special relativistic effects. The team also included general relativistic effects, which are important for stars above 1,000 solar masses.
They found that primordial stars between 55,000 to 56,000 solar masses live about 1.69 million years before becoming unstable due to general relativistic effects and then start to collapse. As the star collapses, it begins to rapidly synthesize heavy elements like oxygen, neon, magnesium and silicon starting with helium in its core. This process releases more energy than the binding energy of the star, halting the collapse and causing a massive explosion: a supernova.
To model the death mechanisms of these stars, Chen and his colleagues used CASTRO -- a multidimensional compressible astrophysics code developed at Berkeley Lab by scientists Ann Almgren and John Bell. These simulations show that once collapse is reversed, Rayleigh-Taylor instabilities mix heavy elements produced in the star's final moments throughout the star itself. The researchers say that this mixing should create a distinct observational signature that could be detected by upcoming near-infrared experiments such as the European Space Agency's Euclid and NASA's Wide-Field Infrared Survey Telescope.
Depending on the intensity of the supernovae, some supermassive stars could, when they explode, enrich their entire host galaxy and even some nearby galaxies with elements ranging from carbon to silicon. In some cases, supernova may even trigger a burst of star formation in its host galaxy, which would make it visually distinct from other young galaxies.
Read more at Science Daily
Salamanders are the only modern four-legged vertebrates, or animals that have backbones, able to fully regenerate their limbs into adulthood. But many other animals, including frogs, caecilians (amphibians that resemble earthworms) and some fish, also have some regenerative capabilities, suggesting the ability may have initially evolved a very long time ago. Yet, scientists have lacked fossil evidence for the ancient evolution of limb regeneration until now.
"In recent years, people have speculated about the evolution of regeneration, but the amount of data available has been limited," said David Gardiner, a developmental biologist at the University of California, Irvine, who studies limb regeneration but wasn't involved in the current research.
To observe limb regeneration in the fossil record, scientists need to find well-preserved specimens with abnormal limbs or limbs in the process of regenerating (a fully regenerated limb that has formed without defects is difficult to differentiate from an original limb). But in the majority of cases, researchers deal with fossils that are missing skeletal segments or entire body parts.
To better understand the early evolution of vertebrate limb regeneration, scientists at the Museum für Naturkunde (a natural history museum in Berlin) analyzed fossils of Micromelerpeton crederni, a primitive amphibian species and distant relative of modern amphibians that lived during the Upper Carboniferous to Lower Permian time periods, between about 310 million and 280 million years ago. The fossils were originally discovered in lake deposits in Central Europe, such as Lake Odernheim in southwest Germany — the oxygen-free environment at the bottom of the lakes helped preserve the animals' remains, including fine structures such as gills, stomach contents and scale patterns.
The team found that several of the Micromelerpeton fossils had abnormal limbs. For example, some of the limbs had certain bones fused together. Other limbs had additional toes that were narrower than normal toes. And some limbs had toes with too many or too few bones. Though odd, these types of abnormalities can also be seen in living animals.
"These same kinds of anomalies typically are observed in response to injury in modern salamanders that are capable of regeneration, both in the wild and in response to experimental amputations in the lab," Gardiner told Live Science, adding that the modern examples suggest Micromelerpeton was also capable of limb regeneration.
The study suggests limb regeneration was an ancient ability present in the amphibian lineage that led to modern amphibians — an ability that salamanders retained. The ability of modern frogs to regenerate limbs as tadpoles further supports the idea, the researchers wrote in their paper, published today (Sept. 23) in the journal Proceedings of the Royal Society B.
"The similarity between the variant patterns in the limbs of extant salamanders and Micromelerpeton caused by limb regeneration is striking," the authors wrote. It is "suggestive of shared molecular mechanisms that are still acting in modern salamanders as they did in their 300-million-year-old relative Micromelerpeton."
Read more at Discovery News