lunes, 29 de noviembre de 2010
Everyone's abuzz these days about the Large Hadron Collider finally being up and running and collecting data like crazy, storing interesting "events" for future analysis. But did you miss the big news coming out of Fermilab last week? It seems that the D-Zero collaboration -- co-discovers of the top quark back in the 1990s -- analyzed data from a bunch of proton-anti-proton collisions and found a slight asymmetry in the number of muons produced compared to anti-muons: about 1% more.
While that might not sound like much, it a hint of greater things to come, should experiments at the LHC confirm these initial results. It's genuine "new physics," since the most likely culprit for this strange asymmetry is a new particle not predicted by the Standard Model (kind of the periodic table of elementary particle physics). Which is why the New York Times article on the result ends with this classic quote from Fermilab's Joe Lykken: "I would not say that this announcement is the equivalent of seeing the face of god, but it might turn out to be the toe of god."
A quick refresher course for those unfamiliar with the conundrum of matter/antimatter asymmetry in our universe. A long time ago, when our universe was still in its earliest birthing throes, matter and antimatter were colliding and annihilating each other out of existence constantly. This process slowed down as our universe gradually cooled, but there should have been equal parts matter and antimatter -- and there weren't. Instead, there were slightly more matter particles than antimatter.
We know this because we can see the remnants of the survivors of that cosmological Octagon all around us: every bit of matter in our observable universe, from galaxies to dust mites and everything in between, exists because matter won that long-ago war of attrition. And physicists have no idea why that asymmetry should have existed in the first place. It's one of the Big Questions they hope the LHC can help answer.
Technically, it's known as CP (charge-parity) violation, an effect first proposed by Russian physicist Andrei Sakharov, in which "when the charges and spins of particles are reversed, they should behave slightly differently." This isn't the first glimpse of CP violation in the subatomic realm, but prior observed asymmetries haven't been large enough to explain how our material world could exist. According to the New York Times' Dennis Overbye:
"The new effect hinges on the behavior of particularly strange particles called neutral B-mesons, which are famous for not being able to make up their minds. They oscillate back and forth trillions of times a second between their regular state and their antimatter state. As it happens, the meson,s created in the proton-anti-proton collisions, seem to go from their antimatter state to their matter state more rapidly than they go the other way around, leading to an eventual preponderance of matter over antimatter of about 1 percent, when they decay to muons."
Curiouser and curiouser! And not bad for a world-class accelerator that perhaps some perceive as being past its prime. We'll just have to wait and see if experimental results from the LHC give further evidence for this potential first glimpse of exciting new physics beyond the Standard Model.
After colliding lead ions at close to the speed of light, physicists at the Large Hadron Collider (LHC) using the ALICE detector have discovered the Universe acted like a fluid in the moments immediately after the Big Bang. Also, the ATLAS and CMS detectors have observed a phenomenon known as "jet quenching" for the first time.
Until recently, the LHC only accelerated protons and collided them inside the particle accelerator mainly to search for the infamous Higgs boson and other exotic particles. But earlier this month, heavier lead ions were injected into the LHC. This is when the quantum party really got started.
For three weeks, lead ions have raced around the accelerator ring at relativistic speeds, crashing head-on with other lead ions traveling in the opposite direction.
Lead ions are significantly bigger than protons, so they carry more energy. When they collide, they release so much energy that physicists often refer to the lead-lead collisions as "micro-Big Bangs."
Each ion collision can, quite literally, recreate the conditions just after the Big Bang, some 13.75 billion years ago.
For a brief moment, these mini-Big Bangs flashed up to an estimated temperature of 10 trillion degrees Kelvin (that's more than 500,000 times hotter than the center of the sun), giving the ALICE detector a peek into how matter would have acted right at the Universe's superheated birth.
Quarks and Gluons, That's All
It is already known that high-energy collisions in particle accelerators can produce a strange, primordial state of matter. A "quark-gluon plasma" can be created if the collisions are energetic enough, a state of matter that existed during the high-energy conditions just after the Big Bang.
During this time, the Universe would have been so hot and energetic that the particles making up the elements we know today were unable to form, leaving the constituents to float "free" as a primordial soup.
Quarks and gluons were only able to condense into larger particles when universal energy conditions were low enough. Hadrons (i.e. particles made from quarks; including baryons like neutrons and protons) were only allowed to form 10-6 seconds after the Big Bang.
But what was the nature of this quark-gluon primordial soup? Was it a gas or a liquid? What was the Universe actually like 10-6 seconds after the Big Bang (apart from being really, really hot)?
The ALICE experiment has confirmed the quark-gluon plasma is a ultra-low viscosity liquid at these energies. From this finding, physicists now know the newborn Universe acted as a perfect fluid.
Although the U.S. Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory has already carried out similar experiments to arrive at similar conclusions, the LHC has done it at much higher energies.
This result has surprised many scientists who predicted the LHC would generate a plasma that acted more like a gas than a liquid, but the results recently published show strong interactions within this primordial soup that resemble a perfect fluid.
The "Big Bang Machine"
Although it's only been three weeks, the lead-lead collision experiments in the LHC have already ruled out some theories about how the early Universe behaved.
"With nuclear collisions, the LHC has become a fantastic 'Big Bang' machine," said ALICE spokesperson Jürgen Schukraft. "In some respects, the quark-gluon matter looks familiar, still the ideal liquid seen at RHIC, but we’re also starting to see glimpses of something new."
Other observations in the CMS and ATLAS detectors have provided a fascinating look at how this primordial matter interacts with itself.
Immediately after lead ions collided, jets were created by the quarks and gluons blasting away from the micro-Big Bangs. By monitoring how these jets formed, physicists were able to see how the intensely chaotic turmoil evolved.
During proton-proton collisions, these jets are very basic and often form in pairs. In ion-ion collisions, many more particles are generated, producing a huge number of jets. As they tangle together, jets lose energy through interactions scientists are only just beginning to understand. This loss of energy is known as "jet quenching."
I think we are only just witnessing the tip of the iceberg insofar as LHC discoveries, but as we collide particles at higher and higher energies, we peel back the history of the Universe one microsecond at a time.
At the opening of his legendary 1960s TV anthology "The Twilight Zone," writer Rod Serling spoke of an eerie place between "light and shadow." The dim outer periphery of our solar system is a gravitational twilight zone when drifters from other stars mingle with lost solar system debris, according to a recent study.
At a distance of roughly six trillion miles from the sun an unknown number of ancient comet nuclei -- each just a few miles across -- drift at temperatures near absolute zero. When gravitationally perturbed they fall toward the inner solar system like apples shaken from a tree. At least we think they are there, based on the random direction and frequency at which comets dive-bomb the inner solar system.
This hypothetical region is named the Oort cloud after mid-20th century Dutch astronomer Jan Oort, who first proposed such a twilight region to explain what seemed to be a hidden reservoir of comets.
But a sexier name would be the "Alien Comet Zone." Did I say alien? Yes, because this primeval deep freezer may contain comets that were gravitationally snatched from other stars.
Hal Levinson of the Southwest Research Institute (SWRI) in Boulder, Colorado reports that computer simulations show that the early sun could have stolen comets from neighboring newborn stars 4.5 billion years ago. Given the close proximity of young stars -- as we see in the nearby Orion Nebula -- "It's hard to imagine it not happening," says Levison.
Conventional wisdom has been that comets accompanied our own solar system's planetary formation and then got gravitationally booted out to huge distances, like storing junk in the attic. But this kind of mayhem was happing around neighboring star systems too. Therefore, interstellar space got cluttered with a snowstorm of comets orphaned from their birthing star.
Levinson’s model estimates that there should be 400 billion comets out there that are loosely bound to the sun. But in those simulations where the comets only originate in the newborn solar system, the predicted population is a paltry 6 billion -- one for nearly every person now living on Earth.
Levinson and his team say that the "alien comet" idea is bolstered by observations that find comets with very long orbital periods. These should have come from another star Levison maintains.
If this idea is correct, that comets could give us not just domestic chemistry of the primeval solar system, but imported chemical samples of the environment around those stars that where born along with the sun.
Rather than devising interstellar probes to collect such samples, all we have to do is sit back and wait for the samples to come to us.
This would also bolster the idea of exogenesis (a.k.a. panspermia), the hypothesis that the building blocks of life are carried between stars. This new model at least shows a mechanism where alien biochemistry could arrive here.Maybe our cousins live on Alpha Cenauri.
Centuries before Columbus, a Viking-Indian child may have been born in Iceland.
Five hundred years before Columbus sailed the ocean blue, a Native American woman may have voyaged to Europe with Vikings, according to a provocative new DNA study.
Analyzing a type of DNA passed only from mother to child, scientists found more than 80 living Icelanders with a genetic variation similar to one found mostly in Native Americans.
This signature probably entered Icelandic bloodlines around A.D. 1000, when the first Viking-American Indian child was born, the study authors theorize.
Historical accounts and archaeological evidence show that Icelandic Vikings reached Greenland just before 1000 and quickly pushed on to what is now Canada. Icelanders even established a village in Newfoundland, though it lasted only a decade or so
The idea that a Native American woman sailed from North America to Iceland during that period of settlement and exploration provides the best explanation for the Icelanders' variant, the research team says.
"We know that Vikings sailed to the Americas," said Agnar Helgason of deCODE Genetics and the University of Iceland, who co-wrote the study with his student Sigrídur Ebenesersdóttir and colleagues. "So all you have to do is assume … that they met some people and ended up taking at least one female back with them.
"Although it's maybe interesting and surprising, it's not all that incredible," Helgason added. "The alternative explanations to me are less likely"—for example the idea that the genetic trait might exist independently, undiscovered, in a few Europeans.
The study authors themselves admit the case is far from closed. But University of Illinois geneticist Ripan Malhi—an expert in ethnic DNA differences who wasn't part of the project—agreed that the report holds "strong genetic evidence for pre-Columbian contact of people in Iceland with Native Americans."
Dating the DNA Signature
Through genealogical research, the study team concluded that the Icelanders who carry the Native American variation are all from four specific lineages, descended from four women born in the early 1700s.
Those four lineages, in turn, likely descended from a single woman with Native American DNA who must have been born no later than 1700, according to study co-author Ebenesersdóttir.
The genealogical records for the four lineages are incomplete before about 1700, but history and genetics suggest the Native American DNA arrived on the European island centuries before then, study co-author Helgason said.
He pointed out that Iceland was very isolated from the outside world in the centuries leading up to 1700, so it's unlikely that a Native American got to the island during that period.
As further evidence, he noted that—though the Icelanders share a distinct version of the variation—at least one lineage's variation has mutated in a way that would likely have taken centuries to occur, the researchers say.
This unique signature suggests that, in Helgason's words, the Native American DNA arrived in Iceland at least "several hundred years" before 1700.
DNA Evidence Fragmented
Despite the evidence, for now it's nearly impossible to prove a direct, thousand-year-old genetic link between Native Americans and Icelanders.
For starters, no living Native American group carries the exact genetic variation found in the Icelandic families.
But of the many known scattered versions that are related to the Icelandic variant, 95 percent are found in Native Americans. Some East Asians, whose ancestors are thought to have been the first Americans, carry a similar genetic pattern, though.
The Inuit, often called Eskimos, carry no version of the variant—a crucial detail, given that Greenland has a native Inuit population.
Helgason speculates that the precise Icelandic variation may have come from a Native American people that died out after the arrival of Europeans.
It's possible, he added, that the DNA variation actually came from mainland Europe, which had infrequent contact with Iceland in the centuries preceding 1700. But this would depend on a European, past or present, carrying the variation, which so far has never been found.
History Not Much Help?
Complicating matters, the historical record contains no evidence that Icelandic Vikings might have taken a Native American woman back home to their European island, scholars say.
"It makes no sense to me," said archaeologist and historian Hans Gulløv of the Greenland Research Centre in Copenhagen.
For one thing, experts say, nothing in excavations or the Icelandic sagas—thought to be rooted in fact but not entirely reliable—suggests a personal alliance of the kind reported in the new study, published online November 10 in the American Journal of Physical Anthropology.
The Saga of Erik the Red does tell of four Skraeling boys—the Norse term for the American Indians—who were captured by an Icelandic expedition and taken back to Greenland, said Birgitta Wallace, an emeritus archaeologist for Parks Canada who has written extensively about the Norse.
But Icelanders spent little time in North America, and their relations with the people they found living there seem to have been mostly hostile, she said. The stories "talk in not very flattering terms about [Native Americans'] looks," Wallace said.
One saga, she added, tells of explorers "who found some sleeping natives—and they just killed them."
Time to Rewrite Viking History?
"What we have is a big mystery," study co-author Helgason admitted.
It won't be solved, he said, until the DNA pattern's origins are nailed down, perhaps through the study of ancient DNA—for example, if an ancient Native American bone is found with DNA closely matching the Icelandic variant.
But at least one skeptic suggests it's a mystery worth pursuing.
"I have no historical sources telling me" that Vikings took Native Americans home, said Gulløv, the historian. But often when new data is uncovered, he added, "we have to write history anew."
The first news reports from WikiLeaks’ long-expected disclosure of a quarter-million State Department diplomatic cables appeared on major newspaper websites on Sunday, though WikiLeaks’ own website was unavailable, purportedly due to a traffic-flooding cyberattack.
WikiLeaks’ media partners report that the secret-spilling organization gave them 251,287 diplomatic cables from America’s 270 embassies and consulates around the world, and another 8,000 diplomatic “directives” from Washington. About the half the documents are unclassified; the remainder are mostly at the relatively-low classification level “Confidential.” About 11,000 are classified “Secret.”
WikiLeaks is calling their latest blockbuster “Cablegate.” So far the news from the organization’s media partners suggests the leak is unlikely to topple the presidency, but there are some brewing scandals.
Most prominently, a series of secret directives from U.S. Secretary of State Hillary Clinton, and her predecessor Condoleezza Rice, instruct U.S. diplomats to gather intelligence on their foreign counterparts at the United Nations, including, according to one cable, “internet and intranet ‘handles’, internet email addresses, web site identification-URLs; credit card account numbers; frequent-flier account numbers; work schedules, and other relevant biographical information.” A directive sent to U.S. embassies in Africa instructs foreign service officers to collect DNA from local government officials, without specifying a method.
Another cable appears to confirm that the Chinese hacker attacks against the Dalai Lama, Google and a host of U.S. companies detected that surfaced over the last two years was the work of the Chinese government. A Chinese source for the American embassy revealed that China’s Politburo directed the intrusions as part of a cyber-intelligence gathering program erected in 2002.
The White House condemned the latest WikiLeak on Sunday in an e-mailed statement to reporters. “[S]uch disclosures put at risk our diplomats, intelligence professionals, and people around the world who come to the United States for assistance in promoting democracy and open government,” wrote White House press secretary Robert Gibbs. “These documents also may include named individuals who in many cases live and work under oppressive regimes and who are trying to create more open and free societies.”
The New York Times reports that WikiLeaks plans to release the cables on its website in stages, covering select regions of the globe in each release. On Sunday, WikiLeaks’ name server was resolving the sub-domain cablegate.wikileaks.org, but that address, and the main WikiLeaks site, were unreachable. The organization wrote on Twitter: “We are currently under a mass distributed denial of service attack.
The news outlets that enjoyed embargoed access to the documents include New York Times, Der Spiegel, Le Monde and the Guardian. Curiously, the Times reported that it obtained the cables from an “anonymous source,” and not WikiLeaks directly. The paper was among the outlets given embargoed access to earlier WikiLeaks disclosures, but fell out of favor with the organization when it profiled its leader, Julian Assange.
Previous releases of classified material from the wars in Iraq and Afghanistan were also followed by standing-room-only press conferences in London. But it’s unclear if Assange will make a public appearance this time around. Last week a Swedish appeals court upheld an international arrest warrant for the former hacker in a rape investigation in Stockholm.
That investigation stems from encounters Assange had with two women during his visit to Sweden last August. According to local news reports, the woman told investigators the sexual encounters began as consensual, but turned non-consensual when Assange refused to stop despite condom mishaps. Assange has denied any wrongdoing and hinted the case is part of a U.S.-led “smear campaign” targeting WikiLeaks.
The “Cablegate” release has been anticipated since the arrest last spring, first reported by Threat Level, of Army intelligence analyst Bradley Manning. In online chats with the ex-hacker who ultimately turned him in, Manning, now 23, described providing WikiLeaks with a cache of 260,000 diplomatic cables, which he smuggled out of a secure facility on CD-RW labled “Lady Gaga.”
Manning said the cables documented years of secret foreign policy and “almost-criminal political back dealings.”
“Hillary Clinton and several thousand diplomats around the world are going to have a heart attack when they wake up one morning, and find an entire repository of classified foreign policy is available, in searchable format, to the public,” Manning told former-hacker Adrian Lamo.
Manning was charged on July 5 with downloading more than 150,000 cables onto an unclassified computer, and leaking at least 50 of them to an unnamed third party. Wikileaks’ founder Julian Assange has repeatedly denied receiving the cables, but the organization abandoned that position this week after the State Department confirmed it had begun warning foreign diplomats about the impending disclosure.
Manning described obtaining the cables by way of a U.S. information-sharing initiative called Net-Centric Diplomacy.
Established in the government’s post-September 11 drive to break down information barriers between agencies, Net-Centric Diplomacy makes a subset of State Department documents available on the Secret Internet Protocol Router Network, or SIPRNet, the Pentagon’s global, Secret-level wide area network. SIPRnet is accessible to cleared American military service members and civilian agencies around the world.
To put their cables on SIPRnet, foreign service officers add a special designator to the header: “SIPDIS,” for SIPRnet Distribution. Department rules preclude certain types of communications from being marked SIPDIS, such as sensitive cables between an ambassador and the U.S. Secretary of State or the White House. Cables containing personally identifying information, such as Social Security numbers, and cables describing department personnel issues would also be omitted.”
Manning’s chats showed that he expected the cable leak to have historic impact.
“Everywhere there’s a U.S. post, there’s a diplomatic scandal that will be revealed,” he wrote. “It’s open diplomacy. World-wide anarchy in CSV format. It’s Climategate with a global scope, and breathtaking depth. It’s beautiful, and horrifying.”
Update: 17:00 EST The WikiLeaks “Cablegate” site is now reachable. It currently hosts 219 cables. WikiLeaks appears to be redacting the names of at least some U.S. sources.
By discovering the first double star where a pulsating Cepheid variable and another star pass in front of one another, an international team of astronomers has solved a decades-old mystery. The rare alignment of the orbits of the two stars in the double star system has allowed a measurement of the Cepheid mass with unprecedented accuracy. The new result shows that the prediction from stellar pulsation theory is spot on, while the prediction from stellar evolution theory is at odds with the new observations.
The new results, from a team led by Grzegorz Pietrzyński (Universidad de Concepción, Chile, Obserwatorium Astronomiczne Uniwersytetu Warszawskiego, Poland), appear in the Nov. 25, 2010 edition of the journal Nature.
Grzegorz Pietrzyński introduces this remarkable result: "By using the HARPS instrument on the 3.6-metre telescope at ESO's La Silla Observatory in Chile, along with other telescopes, we have measured the mass of a Cepheid with an accuracy far greater than any earlier estimates. This new result allows us to immediately see which of the two competing theories predicting the masses of Cepheids is correct."
Classical Cepheid Variables, usually called just Cepheids, are unstable stars that are larger and much brighter than the Sun . They expand and contract in a regular way, taking anything from a few days to months to complete the cycle. The time taken to brighten and grow fainter again is longer for stars that are more luminous and shorter for the dimmer ones. This remarkably precise relationship makes the study of Cepheids one of the most effective ways to measure the distances to nearby galaxies and from there to map out the scale of the whole Universe .
Unfortunately, despite their importance, Cepheids are not fully understood. Predictions of their masses derived from the theory of pulsating stars are 20% less than predictions from the theory of the evolution of stars. This embarrassing discrepancy has been known since the 1960s.
To resolve this mystery, astronomers needed to find a double star containing a Cepheid where the orbit happened to be seen edge-on from Earth. In these cases, known as eclipsing binaries, the brightness of the two stars dims as one component passes in front of the other, and again when it passes behind the other star. In such pairs astronomers can determine the masses of the stars to high accuracy . Unfortunately neither Cepheids nor eclipsing binaries are common, so the chance of finding such an unusual pair seemed very low. None are known in the Milky Way.
Wolfgang Gieren, another member of the team, takes up the story: "Very recently we actually found the double star system we had hoped for among the stars of the Large Magellanic Cloud. It contains a Cepheid variable star pulsating every 3.8 days. The other star is slightly bigger and cooler, and the two stars orbit each other in 310 days. The true binary nature of the object was immediately confirmed when we observed it with the HARPS spectrograph on La Silla."
The observers carefully measured the brightness variations of this rare object, known as OGLE-LMC-CEP0227 , as the two stars orbited and passed in front of one another. They also used HARPS and other spectrographs to measure the motions of the stars towards and away from the Earth -- both the orbital motion of both stars and the in-and-out motion of the surface of the Cepheid as it swelled and contracted.
This very complete and detailed data allowed the observers to determine the orbital motion, sizes and masses of the two stars with very high accuracy -- far surpassing what had been done before for a Cepheid. The mass of the Cepheid is now known to about 1% and agrees exactly with predictions from the theory of stellar pulsation. However, the larger mass predicted by stellar evolution theory was shown to be significantly in error.
The much-improved mass estimate is only one outcome of this work, and the team hopes to find other examples of these remarkably useful pairs of stars to exploit the method further. They also believe that from such binary systems they will eventually be able to pin down the distance to the Large Magellanic Cloud to 1%, which would mean an extremely important improvement of the cosmic distance scale.
 The first Cepheid variables were spotted in the 18th century and the brightest ones can easily be seen to vary from night to night with the unaided eye. They take their name from the star Delta Cephei in the constellation of Cepheus (the King), which was first seen to vary by John Goodricke in England in 1784. Remarkably, Goodricke was also the first to explain the light variations of another kind of variable star, eclipsing binaries. In this case two stars are in orbit around each other and pass in front of each other for part of their orbits and so the total brightness of the pair drops. The very rare object studied by the current team is both a Cepheid and an eclipsing binary. Classical Cepheids are massive stars, distinct from similar pulsating stars of lower mass that do not share the same evolutionary history.
 The period luminosity relation for Cepheids, discovered by Henrietta Leavitt in 1908, was used by Edwin Hubble to make the first estimates of the distance to what we now know to be galaxies. More recently Cepheids have been observed with the Hubble Space Telescope and with the ESO VLT on Paranal to make highly accurate distance estimates to many nearby galaxies.
 In particular, astronomers can determine the masses of the stars to high accuracy if both stars happen to have a similar brightness and therefore the spectral lines belonging to each of the two stars can be seen in the observed spectrum of the two stars together, as is the case for this object. This allows the accurate measurement of the motions of both stars towards and away from Earth as they orbit, using the Doppler effect.
 The name OGLE-LMC-CEP0227 arises because the star was first discovered to be a variable during the OGLE search for gravitational microlensing. More details about OGLE are available at: http://ogle.astrouw.edu.pl/.
Researchers have demonstrated that the extinction of dinosaurs 65 million years ago paved the way for mammals to get bigger -- about a thousand times bigger than they had been. The study titled, "The Evolution of Maximum Body Size of Terrestrial Mammals," released in the journal Science, is the first to quantitatively explore the patterns of body size of mammals after the demise of the dinosaurs.
The research, funded by a National Science Foundation Research Coordination Network grant and led by University of New Mexico Biology Associate Professor Felisa Smith, brought together an international team of paleontologists, evolutionary biologists and macroecologists from universities around the world.
The goal of the research was to revisit key questions about size, specifically in mammals. "Size impacts all aspects of biology, from reproduction to extinction," said Smith. "Understanding the constraints operating on size is crucial to understanding how ecosystems work."
In order to document what happened to mammals after the extinction of dinosaurs, researchers collected data on the maximum size for major groups of land mammals on each continent, including Perissodactyla, odd-toed ungulates such as horses and rhinos; Proboscidea, which includes elephants, mammoth and mastodon; Xenarthra, the anteaters, tree sloths, and armadillos; as well as a number of other extinct groups. The researchers spent three years assembling the data.
"The database is unique," said Smith "because it's comprehensive, including mammals from all continents since the extinction of the dinosaurs. We estimated body size from fossil teeth, which are the most commonly preserved parts of mammals."
Mammals grew from a maximum of about 10 kilograms when they were sharing the earth with dinosaurs to a maximum of 17 tons afterwards. The researchers found that the pattern was surprisingly consistent, not only globally but also across time and across trophic groups and lineages -- that is, animals with differing diets and descended from different ancestors -- as well.
The maximum size of mammals began to increase sharply about 65 million years ago, peaking in the Oligocene Epoch (about 34 million years ago) in Eurasia, and again in the Miocene Epoch (about 10 million years ago) in Eurasia and Africa. The largest mammal that ever walked the earth -- Indricotherium transouralicum, a hornless rhinoceros-like herbivore that weighed approximately 17 tons and stood about 18 feet high at the shoulder -- lived in Eurasia almost 34 million years ago.
"The remarkable similarity in the evolution of maximum size on the different continents suggests that there were similar ecological roles to be filled by giant mammals across the globe," said Smith. "This strongly implies that mammals were responding to the same ecological constraints."
The results give clues as to what sets the limits on maximum body size on land; the amount of space available to each animal and the climate they live in. The colder the climate, the bigger the mammals seem to get, as bigger animals conserve heat better. It also shows that no one group of mammals dominates the largest size class -- the absolute largest mammal belongs to different groups over time and space.
"The results were striking. Global temperature and terrestrial land area set constraints on the upper limit of mammal body size," said Smith, "with larger mammals evolving when the earth was cooler and the terrestrial land area greater. Our analysis reflected processes operating consistently across trophic and taxonomic groups, and independent of the physiographic history of each continent."
The interest in the size of mammals for Smith began years ago when she was a graduate student at the University of California. "I worked on a number of islands off the coast of Baja, California where rodents had evolved into gigantic body sizes. I've been interested in size ever since."
Smith's colleagues in the project include from UNM Distinguished Professor of Biology Jim Brown, Marcus Hamilton and Jordan Okie. Other coauthors are: Alison Boyer, Daniel Costa, Tamar Dayan, Morgan Ernest, Alistair Evans, Mikael Fortelius, John Gittleman, Larisa Harding, Kari Lintulaakso, Kathleen Lyons, Christy McCain, Juha J. Saarinen, Richard Sibly, Patrick Stephens, Jessica Theodor and Mark Uhen.
A common group of bacteria found in acid bogs and sewage treatment plants has provided scientists with evidence of a 'missing link' in one of the most important steps in the evolution of life on Earth -- the emergence of cells with a nucleus containing DNA (eukaryotic cells).
For billions of years, bacteria (single celled organisms without a nucleus) were the only cellular life form on Earth. Then, about 1.6 to 2.1 billion years ago, eukaryotic cells emerged. These cells (with a nucleus) heralded the evolution of multi-cellular life on Earth including: plants, insects, animals and humans.
Until now scientists have been unable to identify an 'ancestral cell' linking the early prokaryotes with the later eukaryotes, so fusion theory -- where two cells merge to form a new cell -- is often put forward to explain the appearance of these new cell types.
But new findings by scientists from University College Dublin, Ireland, and the European Molecular Biology Laboratory in Heidelberg, Germany, published in Science (Nov. 26, 2010), have put paid to the fusion theory explanation, and suggest that an intermediate or 'missing link' cell did exist all those billions of years ago.
"Our discovery means that the appearance of eukaryotic cells on Earth can be explained by Darwinian evolution over billions of years rather than a 'big bang' fusion theory," says cell biologist Dr Emmanuel Reynaud from University College Dublin, one of the co-authors of the scientific paper.
"Our analysis shows that PVC [Planctomycetes, Verrucomicrobiae, Chlamydiae] bacteria, members of which are commonly found in today's sewage treatment plants or acid bogs, represent an intermediate type of cell structure. They are slightly bigger than other known bacteria, and they also divide more slowly."
"The structure of PVC suggests that it is an ancestor of a 'missing link' cell which connected prokaryotic to eukaryotic cells along an evolutionary path all those billions of years ago," says Dr Damien P Devos from the European Molecular Biology Laboratory, Heidelberg, Germany, who co-authored the scientific paper.
Koalas may be the pickiest marsupials around: They evolved to feed almost exclusively on the leaves of Eucalyptus trees, and they are highly selective when it comes to which species and even which individual trees they visit. When the furry leaf-eater settles on a particular tree, it relies on a number of factors, including taste, to make its selection. In a study published in the November issue of Ecology, a journal of the Ecological Society of America (ESA), researchers used koala feeding preferences to design a new method that could help ecologists and conservationists map habitats.
Ben Moore and colleagues from the Australian National University and the Macaulay Land Use Research Institute in Scotland collected and analyzed leaves from all the trees available to koalas in a Eucalyptus woodland using a near-infrared spectroscopic model. To define "palatability" in koala terms, the researchers tested leaves on captive koalas and recorded how much they ate: They found that the koalas ate less foliage when it contained lots of lipid-soluble phenolic chemicals known as formylated phloroglucinol compounds (FPCs). The researchers then tracked koala tree visits in a Eucalyptus woodland to show that tree preferences of wild koalas could be predicted using the taste preferences of the captive koalas. The researchers also determined the chemical composition of the trees' leaves and other factors such as tree size and neighborhood quality, or how attractive each tree's neighbors were to koalas.
Specifically, koalas spend more time in large trees; however, the individual trees they prefer depend on the taste of the leaves and the "neighborhood" in which the tree is growing. Although tree size and taste are most important to the koalas, the researchers found that trees were visited more often if they were surrounded by smaller, less palatable trees or by larger, more palatable trees. Moore and colleagues explained that trees surrounded by smaller, unpalatable trees were probably more attractive by comparison. At the other extreme, trees surrounded by other large, palatable trees were visited more frequently because koalas were attracted to these high-quality areas.
"This method uses a new technique to combine our understanding of animal behavior with the chemical, spatial and physical aspects of the environment to make a map of koala habitat, as koalas see it," said Moore. "Our approach can aid ecologists in tracking and examining the presence or absence of animal populations in different areas -- and it can measure plants' susceptibility to herbivory -- by determining the quality and value of a habitat from the herbivore's point of view."
Astronomers using NASA's Spitzer Space Telescope have found a stunning burst of star formation that beams out as much infrared light as an entire galaxy. The collision of two spiral galaxies has triggered this explosion, which is cloaked by dust that renders its stars nearly invisible in other wavelengths of light.
The starburst newly revealed by Spitzer stands as the most luminous ever seen taking place away from the centers, or nuclei, of merging parent galaxies. It blazes ten times brighter than the nearby Universe's previous most famous "off-nuclear starburst" that gleams in another galactic smashup known as the Antennae Galaxy.
The new findings show that galaxy mergers can pack a real star-making wallop far from the respective galactic centers, where star-forming dust and gases typically pool.
"This discovery proves that merging galaxies can generate powerful starbursts outside of the centers of the parent galaxies," says Hanae Inami, first author of a paper detailing the results in the July issue of The Astronomical Journal. Inami is a graduate student at The Graduate University for Advanced Studies in Japan and the Spitzer Science Center at the California Institute of Technology. She adds: "The infrared light emission of the starburst dominates its host galaxy and rivals that of the most luminous galaxies we see that are relatively close to our home, the Milky Way."
"No matter how you slice it, this starburst is one of the most luminous objects in the local Universe," agrees Lee Armus, second author of the paper and a senior research astronomer also at the Spitzer Science Center.
A dazzling galactic dust-up
Inami, Armus and their colleagues spotted the buried starburst with Spitzer in the interacting galaxies known as II Zw 096. This galactic train wreck -- located around 500 million light years away in the constellation Delphinus (the Dolphin) -- will continue to unfold for a few hundred million years. Gravitational forces have already dissolved the once-pinwheel shape of one of II Zw 096's pair of merging galaxies.
The ultra-bright starburst region spans 700 light-years or so -- just a tiny portion of II Zw 096, which streams across some 50,000 to 60,000 light-years -- yet it blasts out 80 percent of the infrared light from this galactic tumult. Based on Spitzer data, researchers estimate the starburst is cranking out stars at the breakneck pace of around 100 solar masses, or masses of our Sun, per year.
The prodigious energy output of this starburst in a decentralized location as revealed in the infrared has surprised the Spitzer researchers. The new observations go to show how the notion of a cosmic object's nature can change tremendously when viewed at different wavelengths of light. In this way, the shapes and dynamics of distant, harder-to-study galactic mergers could turn out to be a good deal more complex than current observations over a narrow range of wavelengths imply.
"Most of the far-infrared emission in II Zw 096, and hence most of the power, is coming from a region that is not associated with the centers of the merging galaxies," Inami explains. "This suggests that the appearances and interactions of distant, early galaxies during epochs when mergers were much more common than today in the Universe might be more complicated than we think."
A fleeting, perhaps prophetic vista?
In galaxy mergers, individual stars rarely slam into one another because of the vast distances separating them; even in the comparatively crowded central hubs of spiral galaxies, trillions of kilometers still often yawn between the stars.
But giant, diffuse clouds of gas and dust in galaxies do crash together -- passing through each other somewhat like ocean waves -- and in turn spur the gravitational collapse of dense pockets of matter into new stars. These young, hot stars shine intensely in the energetic ultraviolet part of the spectrum. In the case of II Zw 096, however, a thick shroud of gas and dust still surrounds this stellar brood. The blanket of material absorbs the stars' light and re-radiates it in the lower-energy, infrared wavelengths that gleam clear through the dust to Spitzer's camera.
Astronomers were lucky to capture this transient phase in the evolution of the starburst and of the daughter galaxy that will eventually coalesce out of the collision. "Spitzer has allowed us to see the fireworks before all the gas and dust has cleared away, giving us a preview of the exciting new galaxy being built under the blanket," Inami says.
Merging galaxies such as II Zw 096 also offer a sneak peek at the fate of our Milky Way in some 4.5 billion years when it is expected to plow into its nearest large galactic neighbor, the Andromeda Galaxy. Off-nuclear starbursts such as that in II Zw 096 and the Antennae Galaxy could occur in the vicinity of our Solar System, perhaps, which is located about two-thirds of the way out from the Milky Way's glowing, bulging center.
"This kind of dramatic thing happening in II Zw 096 could happen to the Milky Way and Andromeda when they meet in the far future," says Inami.
A unique queen's crown with ancient symbols combined with a new method of studying status in Egyptian reliefs forms the basis for a re-interpretation of historical developments in Egypt in the period following the death of Alexander the Great. A thesis from the University of Gothenburg (Sweden) argues that Queen Arsinoë II ruled ancient Egypt as a female pharaoh, predating Cleopatra by 200 years.
Researchers are largely agreed on Queen Arsinoë II's importance from the day that she was deified. She was put on a level with the ancient goddesses Isis and Hathor, and was still respected and honoured 200 years after her death when her better-known descendant Cleopatra wore the same crown. But the reasons behind Arsinoë's huge influence have been interpreted in many different ways.
Maria Nilsson has studied her historical importance by interpreting her personal crown and its ancient symbols. The crown, which has never been found but is depicted on statues and Egyptian reliefs, was created with the help of the powerful Egyptian priesthood to symbolise the qualities of the queen. The thesis questions the traditional royal line which excludes female regents, and defies some researchers' attempts to minimise Arsinoë's importance while she was still alive.
"My conclusion instead is that Arsinoë was a female pharaoh and high priestess who was equal to and ruled jointly with her brother and husband, and that she was deified during her actual lifetime," says Nilsson. "It was this combination of religion and politics that was behind her long-lived influence."
But it was not only Cleopatra who wanted to re-use Arsinoë's important and symbolic crown. Male descendants -- all named Ptolemy -- used her crown as a template when creating a new crown which they gave to the goddess Hathor to honour the domestic priesthood and so win its support when Egypt was gripped by civil war.
The thesis is clearly structured around the crown and includes its wider context in the reliefs. Nilsson paints an all-round picture of the queen, how she dressed, the gods she was depicted with, the titles she was given, and so on.
The source material comes from Egypt and can be used as a basis for understanding the country's political and religious development. At the same time, Nilsson paves the way for future studies of Egyptian crowns as symbols of power and status, and of the development of art in a more general sense.
"The creation of Queen Arsinoë's crown was just the beginning," she says.
miércoles, 24 de noviembre de 2010
Afraid to share your dreams with others because you think you are alone? Chances are, if you have dreamed it, others have too. But do you have these dreams regularly?
This is what Calvin Kai-Ching Yu wanted to explore in a new study published in the November issue of Dreaming. He set out to analyze not only what dreams are most common, but what dreams recur regularly.
Yu reviews interesting findings from past studies and performs his own study to measure dream prevalence (what percent of people have ever had a dream), dream recurrence (what percent have had the dream more than three times in their life), and dream regularity (what percent have had the dream at least several times a year).
First up: the broad basics of dreams.
Dreams can transcend cultural differences. Past researchers have found that the most common dream themes were the same across different ethnic groups.
The most common? Being chased. Teeth falling out, losing control of a vehicle, flying and not being able to find a toilet make up about half of the most commonly recurring dream themes.
But dreams also have a darker side.
Yu cites a prior study that compared dream themes to psychosis. Traits common in psychotic and schizophrenic patients, such as delusions of grandiosity, persecution and religion, are very common in dreams. In fact, delusions such as "being tracked" and "becoming a celebrity" occurred more prevalently than common dream motifs such as "teeth falling out" and the classic "being nude."
Next, Yu designed his own study on a slightly different aspect of dreams: regularity. What type of dreams do we repeatedly have night after night?
Over 600 participants joined the study, conducted in Hong Kong. They were given a questionnaire which included 78 dream themes. Respondents then answered if they had never dreamed of the subject or if they had dreamed of it only once or twice, three times or more, several times a year or once a month or more.
So what dreams did participants revisit the most often?
The age old school/teacher/studying trope ranked number one. Not only had over 80 percent ever had a dream on that subject, but also over 50 percent said they dreamed about it regularly. Over half of the sample also repeatedly dreamed of "searching for a certain place" and "falling."
Some of the more surprising findings? "Eating delicious foods" was the fifth most regularly dreamed theme, higher ranked than flying or being chased. Perhaps dieters are seeking out their shunned treats in regular nightly escapes.
Most interestingly, the study found that dream prevalence, recurrence and regularity do not always correspond. For example, 68 percent of respondents dreamed "of being a child again," but hardly any have that dream repeatedly.
On the contrary, most had never dreamed of being physically attacked, but those who had were regularly dreaming of it. Likewise, "teeth falling out" rated significantly higher on regularity than on prevalence or recurrence. Ouch.
Back to the delusions. While most people wouldn't want to admit experiencing delusions in their waking lives, delusions in dreams were very common. Yu's study found six of the top 20 regular dream themes were delusions. Erotomania, or believing a famous person is in love with you, was one of the most common. One half of participants had dreamt of having a love affair with a celebrity. Romance trumps sex here, because only 22 percent dreamed of having a sexual relationship with a celebrity.
* Gold, sea-urchin-shaped nanoparticles make plant leaves glow.
* Treated trees could replace electric lights to illuminate city streets.
* Tree-lit streets likely years away.
The golden glow of street lights could soon be replaced by the green fluorescence of tree leaves. Scientists from the Academia Sinica and the National Cheng Kung University in Taipei and Tainan have implanted glowing, sea urchin shaped gold nanoparticles, known as bio light emitting diodes, or bio LEDs, inside the leaves of a plant.
The new nanoparticles could replace the electricity powered street light with biologically powered light that removes CO2 from the atmosphere 24 hours a days.
"In the future, bio-LED could be used to make roadside trees luminescent at night," said Yen-Hsun Su in an interview with Chemistry World. "This will save energy and absorb CO2 as the bio-LED luminescence will cause the chloroplast to conduct photosynthesis."
The gold, sea urchin shaped nanoparticles are the key to turning a material that normal absorbs light into one that emits it.
Chlorophyll, the photosynthetic pigment that gives leaves their characteristic green color, is widely known for its ability to absorb certain wavelengths of light. However, under certain circumstances, such as being exposed to violet light, chlorophyll can also produce a light of its own. When exposed to light with a wavelengths of about 400 nanometers the normally green colored chlorophyll glows red.
Violet light is hard to come by though, especially at night, when glowing leaves would be useful to drivers and pedestrians. The scientists needed a source of violet light, and found it in the gold nanoparticles.
When shorter wavelengths of light, invisible to the human eye, hit the gold nanoparticles, they get excited and start to glow violet. That violet light strikes the nearby chlorophyll molecules, excites them, and the chlorophyll then produces the red light.
The scientists, who published their work on bio LEDs in the journal Nanoscale, hope that that trees treated with the gold nanoparticles would produce enough light that they could replace electric or gas street lights.
For now however, the effect is limited to the scientist's test subject, an aquatic plant known as Bacopa caroliniana. Expanding to terrestrial plants, the kind that line streets, should be possible, said Krishanu Ray, a scientist at the University of Maryland, with some additional work.
"They certainly could be used as street lights," said Ray. "But that's a long way away."
Whatever impulse drives soldiers, sailors, airmen and marines to commemorate their units with insanely random, over-the-top, or awesomely bad patches, we say: Cultivate it.
Trevor Paglen, a bi-coastal artist and author based in Oakland and New York City, brought bad military patches to new heights of glory with his 2007 book I Could Tell You But Then You Would Have to Be Destroyed by Me. It's a collection of more than 100 insignias from the most secret of military units. The following are some of the best patches from a new edition of his book coming out.
Paglen's first book got coverage in a lot of newspapers and on The Colbert Report. So, any satellite operator or drone pilot wanting to immortalize their units would send along a patch for the next edition.
That didn't always thrill higher-ups. "I heard that one commander started a little witch hunt to find out who'd leaked a space-related patch to me," Paglen says. "None of these patches are 'classified' per se, but some were produced with an informal understanding that they wouldn’t be made public. I hope nobody got into trouble."
Paglen knows about some white-whale patches that he hasn't gotten his hands on yet. Know anything about Ibis Dawn, Scarecrow, Sundowner, or something that says Invisus cum libertas et iustitia omnibus? "If you have one of these," Paglen says, "I'd love to trade something cool for it, or even get a nice scan." Until he puts out yet another edition, these 10 designs have to stand as a high-water mark in awesomely bad military patches.
Like a Space-Phoenix From Hell
The Latin phrase below the Phoenix translates to "The Devil You Know." That's the rationale behind the spy-satellite operators at the National Reconnaissance Office, who peer into the workings of foreign military arsenals from hundreds of miles into space.
This patch, from National Reconnaissance Office Launch 49, puts a bold face on a failure: the Future Imagery Architecture, a $10-billion disaster in the guise of a satellite able to peer through heavy cloud cover. The end of Future Imagery Architecture meant that NRO had to continue with its KH "Keyhole" satellite family, many of which the United States uses to spy on Russian nukes. Launch 49 of the KH-11 series supposedly used spare parts from Future Imagery Architecture -- hence the Phoenix design.
Image: Courtesy Trevor Paglen
Special Projects Flight Test Squadron
No one patch may cobble together as many symbols as this one does. "Rat 55" is the call sign for pilots flying the T-43A, a radar testbed ("Rat," get it?) with an Air Force serial number ending in 55.
The rat's holding a pair of radar devices, one stretched outward and one near its butt, "both of which recall the radome configuration" of the plane. Other flight-test operators for classified aircraft wear patches with wizardy features, so presumably that's what's up with the rat's hat.
Confirmed: The Air Force Totally Hides Aliens From Us
You don't know how many Freedom of Information Act requests we've filed in the hope of finding the Alien Technology Exploitation Division, the intrepid souls who'll soon announce a sources-sought contract to develop the Hyperspace Blaster. Alas, they don't exist.
A former officer at Air Force Space Command tells Paglen that he and his friends had the patches made at their own expense after getting endlessly ribbed for working in a secure vault "where they kept the alien bodies." They wore them on their flight suits for months before a one-star general asked where he could get one of his own.
Special Projects Flight-Test Squadron
Welcome to Area 51.
Out in the Nevada desert, in a place called Groom Lake, the Air Force's most secretive organization tests its advanced prototypes. Supposedly, Lockheed's F-117A Nighthawk stealth plane went through Groom Lake's test facilities -- one of many flown by the Special Projects Flight Test Squadron, whose patch this is.
The diamond shape in the center of the undated patch "may refer to early designs of stealth aircraft," Paglen writes. Those planes are parked next to the dismembered Martians.
Space Spies Are Ready to Breach Your Borders
Paglen won't be able to find the origins of every patch he comes across. But rarely is a mystery more appropriate than in the case of the Sensor Hunters, whoever they are. Illustrated by one of MAD Magazine's spies, their brief(cases) include spying on the entire world, with swaggering disregard for nations' claims to control their own internal affairs.
The twinkling stars probably suggest these guys have something to do with space, but all Paglen writes is that they "devoted to reconnaissance and intelligence operations."
I Want to Believe (in the Navy's Communications Network)
The Navy uses a system of Boeing-designed space satellites to keep mariners connected with each other and home base while they're out at sea. The system is known as the Ultra-High Frequency Follow-On program.
If you squint enough, that kinda-sorta-maybe abbreviates to UFO. Naturally, some wise-cracking sailor -- Paglen doesn't specify whom -- had the idea to make this X-Files-inspired patch.
The More Secretive the Drone, the More Psychedelic the Patch
Groom Lake doesn't just house cutting-edge piloted planes. It's also home to the Desert Prowler, a Lockheed-designed drone shrouded in mystery since its 2005 launch -- and, perhaps, related to a different secret drone, the RQ-170 Sentinel aloft over Kandahar.
And since its remote pilots and crew can't exactly flaunt their involvement with the program, their patches will have to suffice. The Roman numerals for 9 and 11 partially bound the badge -- subtle! -- and the rainbow-emanating eye has a lightning bolt through it, suggesting that the drone is armed and ready to rain vengeance for 9/11 on presumed Kandahari insurgents. Wild guess: The lightning-bolted Omega in the thought balloon indicates the drone is dreaming of a violent end to its targets.
An international team of astronomers have discovered a unique and exotic star system with a very cool methane-rich (or T-) dwarf star and a 'dying' white dwarf stellar remnant in orbit around each other. The system is a 'Rosetta Stone' for T-dwarf stars, giving scientists the first good handle on their mass and age.
The team, led by Dr Avril Day-Jones of the Universidad de Chile and including Dr David Pinfield of the University of Hertfordshire as well as astronomers from the University of Montreal, publish their results in the journal Monthly Notices of the Royal Astronomical Society.
The system is the first of its type to be found. The two stars are low in mass and have a weak mutual gravitational attraction as they are separated by about a quarter of a light year or 2.5 trillion km (to put this in context Neptune is only 4.5 billion km from the Sun). Despite the frailty of the system it has stayed together for billions of years, but its stars are cooling down to a dark demise.
Methane dwarfs are on the star / planet boundary and are about the size of the giant planet Jupiter. They have temperatures of less than 1000 degrees Celsius (in comparison the Sun's surface is at 5500 degrees Celsius). Methane is a fragile molecule destroyed at warmer temperatures, so is only seen in very cool stars and objects like Jupiter. Neither giant planets nor T-dwarf stars are hot enough for the hydrogen fusion that powers the Sun to take place, meaning that they simply cool and fade over time.
White dwarfs are the end state of stars similar to and including the Sun. Once such stars have exhausted the available nuclear fuel in their cores, they expel most of their outer layers into space forming a remnant planetary nebula and leaving behind a hot, but cooling core or white dwarf about the size of the Earth. For our Sun this process will begin about 5 billion years in the future.
In the newly-discovered binary, the remnant nebula has long since dissipated and all that is left is the cooling white dwarf and methane dwarf pair.
Dr Day-Jones puts this in context, commenting, "In about 6 billion years' time, when our Sun 'dies' and becomes a white dwarf itself, the stars in the newly-discovered system will have changed dramatically. The methane dwarf will have cooled to around room temperature, and the white dwarf will have cooled to 2700 Celsius or the temperature of the methane dwarf at the start of its life."
This binary is providing a crucial test of the physics of ultra-cool (temperatures less than 1000 degrees Celsius) stellar atmospheres because the white dwarf lets us establish the age of both objects. It calibrates properties of the methane dwarf such as its mass, making it a kind of 'Rosetta Stone' for similar stars with complex, hazy ultra-cool atmospheres.
The methane dwarf was identified in the UKIRT Infrared Deep Sky Survey (UKIDSS) as part of a project to identify the coolest objects in the galaxy. Its temperature and spectrum were measured by the Gemini North Telescope in Hawaii.
The team then found that the methane dwarf shares its motion across the sky with a nearby blue object catalogued as LSPM 1459+0857. They studied the blue object using the world's largest optical telescope, the European Southern Observatory's Very Large Telescope (VLT) in Chile. The new VLT observations revealed the blue object to be a cool white dwarf and companion to the methane dwarf. The objects were thus re-christened LSPM 1459+0857 A and B.
The two stars are today separated by at least 2.5 trillion km, but would have been closer in the past before the white dwarf was formed. Once the star that formed the white dwarf reached the end of its life and expelled its outer layers, the loss of mass weakened the gravitational pull between the stars, causing the methane dwarf to spiral outwards to create the gravitationally fragile system that we see today. But the current age of the white dwarf indicates that this system has survived for several billion years. So the new discovery shows that despite their fragility, such binaries are able to remain united even as they move through the maelstrom of the disc of our Galaxy.
"Binary systems like this provide vital information and allow us to better understand ultra-cool atmospheres and the very low-mass dwarfs and planets they enshroud" says Dr Pinfield. "The fact that these binaries survive intact for billions of years means that we could find many more lurking out there in the future."
Five related species of tree-dwelling snakes found in Southeast and South Asia may just be the worst nightmares of ophidiophobes (people who have abnormal fears of snakes). Not only are they snakes, but they can "fly" -- flinging themselves off their perches, flattening their bodies, and gliding from tree to tree or to the ground.
To Virginia Tech biologist Jake Socha, these curious reptiles are something of a biomechanical wonder. In order to understand how they do what they do, Socha and his colleagues recently studied Chrysopelea paradisi snakes as they launched themselves off a branch at the top of a 15-meter-tall tower.
Four cameras recorded the curious snakes as they glided. This allowed them to create and analyze 3-D reconstructions of the animals' body positions during flight -- work that Socha recently presented at the American Physical Society Division of Fluid Dynamics (DFD) meeting in Long Beach, CA.
The reconstructions were coupled with an analytical model of gliding dynamics and the forces acting on the snakes' bodies. The analyses revealed that the reptiles, despite traveling up to 24 meters from the launch platform, never achieved an "equilibrium gliding" state -- one in which the forces generated by their undulating bodies exactly counteract the force pulling the animals down, causing them to move with constant velocity, at a constant angle from the horizon. Nor did the snakes simply drop to the ground.
Instead, Socha says, "the snake is pushed upward -- even though it is moving downward -- because the upward component of the aerodynamic force is greater than the snake's weight."
"Hypothetically, this means that if the snake continued on like this, it would eventually be moving upward in the air -- quite an impressive feat for a snake," he says. But our modeling suggests that the effect is only temporary, and eventually "the snake hits the ground to end the glide."
The presentation, "Gliding flight in snakes: non-equilibrium trajectory dynamics and kinematics" was given on November 22, 2010
This research is being published in the journal Bioinspiration and Biomimetics.
In an experiment to collide lead nuclei together at CERN's Large Hadron Collider physicists from the ALICE detector team including researchers from the University of Birmingham have discovered that the very early Universe was not only very hot and dense but behaved like a hot liquid.
By accelerating and smashing together lead nuclei at the highest possible energies, the ALICE experiment has generated incredibly hot and dense sub-atomic fireballs, recreating the conditions that existed in the first few microseconds after the Big Bang. Scientists claim that these mini big bangs create temperatures of over ten trillion degrees.
At these temperatures normal matter is expected to melt into an exotic, primordial 'soup' known as quark-gluon plasma. These first results from lead collisions have already ruled out a number of theoretical physics models, including ones predicting that the quark-gluon plasma created at these energies would behave like a gas.
Although previous research in the USA at lower energies, indicated that the hot fire balls produced in nuclei collisions behaved like a liquid, many expected the quark-gluon plasma to behave like a gas at these much higher energies.
Scientists from the University of Birmingham's School of Physics and Astronomy are playing a key role in this new phase of the LHC's programme which comes after seven months of successfully colliding protons at high energies. Dr David Evans, from the University of Birmingham's School of Physics and Astronomy, and UK lead investigator at ALICE experiment, said: "Although it is very early days we are already learning more about the early Universe."
He continues: "These first results would seem to suggest that the Universe would have behaved like a super-hot liquid immediately after the Big Bang."
The team has also discovered that more sub-atomic particles are produced in these head-on collisions than some theoretical models previously suggested. The fireballs resulting from the collision only lasts a short time, but when the 'soup' cools down, the researchers are able to see thousands of particles radiating out from the fireball. It is in this debris that they are able to draw conclusions about the soup's behaviour.
Two papers detailing this research have been submitted for publication and posted on: http://xxx.lanl.gov/abs/1011.3914| and http://xxx.lanl.gov/abs/1011.3916|.
Astronomers find cosmic dust annoying when it blocks their view of the heavens, but without it the universe would be devoid of stars. Cosmic dust is the indispensable ingredient for making stars and for understanding how primordial diffuse gas clouds assemble themselves into full-blown galaxies.
"Formation of galaxies is one of the biggest remaining questions in astrophysics," said Andrey Kravtsov, associate professor in astronomy & astrophysics at the University of Chicago.
Astrophysicists are moving closer to answering that question, thanks to a combination of new observations and supercomputer simulations, including those conducted by Kravtsov and Nick Gnedin, a physicist at Fermi National Accelerator Laboratory.
Gnedin and Kravtsov published new results based on their simulations in the May 1, 2010 issue of The Astrophysical Journal, explaining why stars formed more slowly in the early history of the universe than they did much later. The paper quickly came to the attention of Robert C. Kennicutt Jr., director of the University of Cambridge's Institute of Astronomy and co-discoverer of one of the key observational findings about star formation in galaxies, known as the Kennicutt-Schmidt relation.
In the June 3, 2010 issue of Nature, Kennicutt noted that the recent spate of observations and theoretical simulations bodes well for the future of astrophysics. In their Astrophysical Journal paper, Kennicutt wrote, "Gnedin and Kravtsov take a significant step in unifying these observations and simulations, and provide a prime illustration of the recent progress in the subject as a whole."
Kennicutt's star-formation law relates the amount of gas in galaxies in a given area to the rate at which it turns into stars over the same area. The relation has been quite useful when applied to galaxies observed late in the history of the universe, but recent observations by Arthur Wolfe of the University of California, San Diego, and Hsiao-Wen Chen, assistant professor in astronomy and astrophysics at UChicago, indicate that the relation fails for galaxies observed during the first two billion years following the big bang.
Gnedin and Kravtsov's work successfully explains why. "What it shows is that at early stages of evolution, galaxies were much less efficient in converting their gas into stars," Kravtsov said.
Stellar evolution leads to increasing abundance of dust, as stars produce elements heavier than helium, including carbon, oxygen, and iron, which are key elements in dust particles.
"Early on, galaxies didn't have enough time to produce a lot of dust, and without dust it's very difficult to form these stellar nurseries," Kravtsov said. "They don't convert the gas as efficiently as galaxies today, which are already quite dusty."
The star-formation process begins when interstellar gas clouds become increasingly dense. At some point the hydrogen and helium atoms start combining to form molecules in certain cold regions of these clouds. A hydrogen molecule forms when two hydrogen atoms join. They do so inefficiently in empty space, but find each other more readily on the surface of a cosmic dust particle.
"The biggest particles of cosmic dust are like the smallest particles of sand on good beaches in Hawaii," Gnedin said.
These hydrogen molecules are fragile and easily destroyed by the intense ultraviolet light emitted from massive young stars. But in some galactic regions dark clouds, so-called because of the dust they contain, form a protective layer that protects the hydrogen molecules from the destructive light of other stars.
"I like to think about stars as being very bad parents, because they provide a bad environment for the next generation," Gnedin joked. The dust therefore provides a protective environment for stellar nurseries, Kravtsov noted.
"There is a simple connection between the presence of dust in this diffuse gas and its ability to form stars, and that's something that we modeled for the first time in these galaxy-formation simulations," Kravtsov said. "It's very plausible, but we don't know for sure that that's exactly what's happening."
The Gnedin-Kravtsov model also provides a natural explanation for why spiral galaxies predominately fill the sky today, and why small galaxies form stars slowly and inefficiently.
"We usually see very thin disks, and those types of systems are very difficult to form in galaxy-formation simulations," Kravtsov said.
That's because astrophysicists have assumed that galaxies formed gradually through a series of collisions. The problem: simulations show that when galaxies merge, they form spheroidal structures that look more elliptical than spiral.
But early in the history of the universe, cosmic gas clouds were inefficient at making stars, so they collided before star formation occurred. "Those types of mergers can create a thin disk," Kravtsov said.
As for small galaxies, their lack of dust production could account for their inefficient star formation. "All of these separate pieces of evidence that existed somehow all fell into one place," Gnedin observed. "That's what I like as a physicist because physics, in general, is an attempt to understand unifying principles behind different phenomena."
More work remains to be done, however, with input from newly arrived postdoctoral fellows at UChicago and more simulations to be performed on even more powerful supercomputers. "That's the next step," Gnedin said.
Binghamton University researchers recently revived ancient bacteria trapped for thousands of years in water droplets embedded in salt crystals.
For decades, geologists have looked at these water droplets -- called fluid inclusions -- and wondered whether microbes could be extracted from them. Fluid inclusions have been found inside salt crystals ranging in age from thousands to hundreds of millions years old.
But there has always been a question about whether the organisms cultured from salt crystals are genuinely ancient material or whether they are modern-day contaminants, said Tim Lowenstein, professor of geological sciences and environmental studies at Binghamton.
Lowenstein and Binghamton colleague J. Koji Lum, professor of anthropology and of biological sciences, believe they have resolved this doubt. And they've received $400,000 from the National Science Foundation to support further research on the topic.
Lowenstein's team, which has been pursuing this problem for years, began by examining the fluid inclusions under a microscope. "Not only did we find bacteria, we found several types of algae as well," he said. "The algae actually may be the food on which the bacteria survive for tens of thousands of years."
When Lum got involved, the researchers began to wonder about the DNA of the organisms they were finding.
"You have a little trapped ecosystem," Lum said. "Some of these guys are feeding on other ones trapped in this space. The things that aren't alive in there, their DNA is still preserved."
Lum's graduate student Krithivas Sankaranarayanan reviewed existing literature on ancient DNA and helped to develop a protocol for use with Lowenstein's samples.
"We have these samples going back from the present to over 100,000 years in one exact location," Lum said. "So Tim can look at the salinity and reconstruct ancient climates. Now we're looking at the DNA from bacteria, the algae, the fungi and what was living in those waters and how those things changed over time. We have a view of all the different organisms that were in the lakes at the time these inclusions were formed."
The researchers sequence the DNA and culture the bacteria they find. Then it's time to think big. Lum's most optimistic view of the project goes like this: "It's possible that we can observe organisms evolving and see how they're reacting to climate change over geologic time."
The samples Lowenstein works with are drawn from Death Valley and Saline Valley in California as well as from sites in Michigan, Kansas and Italy.
Temperatures at these locations may have reached 130 degrees Fahrenheit in the past, and the pockets of water trapped inside the rocks are generally very salty.
The environment may sound harsh -- in fact, it's among the most extreme on Earth -- but the creatures that survive there are tough.
"These are some of the hardiest beasts on the planet," Lum said. And the conditions inside these water droplets are ideally suited to preserving DNA.
"They're like time capsules," Lowenstein agreed.
jueves, 18 de noviembre de 2010
In the coming decades we will begin to characterize planets in the habitable zones around nearby stars. The problem is that just because they are habitable we will still be hard-pressed to understand if the chemistry of their atmospheres comes only from microorganisms, or six-legged giraffes, or even sentient beings.
A huge influence on planet's ability to evolve complex life is not just location, location, location, but rather environment, environment environment. The difference? Some planetary systems may have gas giant planets that accelerate the rate of comet or asteroid impacts on the surface of their terrestrial siblings.
Other Earth-like worlds might orbit petulant young red dwarf stars that spit out searing flares that pound the planets.
But Earth history has shown that one species’ Armageddon may be another species’ Genesis. Take the devastating asteroid impact that triggered a mass extinction 65 million years ago, toppling the mightiest predators that ever-walked Earth, the dinosaurs. Surviving dinosaurs evolved to take to the air and mammals rose from the shadows to dominate our planet.
Even more dramatically, a biological arms race -- the Cambrian Explosion -– took place on the cusp of Earth’s near-death experience as a "snowball Earth" about 500 million years ago.
Based on these discoveries, the emerging view is that long periods of ecological stability are punctuated by catastrophes, both Earth-made and extraterrestrial. It seems that when all hell is breaking loose on a Earth major evolutionary changes happen rapidly.
Aside from our new view of the devastating threats from space debris, this kind of "kick in the pants" model for evolution is not new.
Last year was the 150th anniversary of Darwin's landmark publication, On the Origin of the Species, which laid the foundation for modern biology.
Darwin's idea was that most evolution was accomplished very gradually by competition between organisms that became better adapted to relatively stable environment. But 28 years earlier than Darwin's publication the Scottish horticulturalist Patrick Matthew published his own ideas about the process of natural selection:
"There is a natural law universal in nature, tending to render every reproductive being the best possibly suited to its condition . . . it is only the hardier, more robust, better suited to circumstance individuals, who are able to struggle forward to maturity, . . . from the strict ordeal by which Nature tests their adaptation to her standard of perfection and fitness to continue their kind by reproduction.'
In other words, Matthew thought that it took no less than global catastrophes to shock evolution out of a laid-back state and spur diversity and competition among organisms. When the going gets tough only the tough get going -- to borrow the phrase from Billy Ocean's 1985 pop song.
Matthew’s musings were simply published in the appendix to his 1831 book with the utterly forgettable title: Naval Timber and Arboriculture.
Writing in a recent issue of Historical Biology, New York University geologist Michael Rampino concludes: "Others have said that Matthew's thesis was published in too obscure a place to be noticed by the scientific community, or that the idea was so far ahead of its time that it could not be connected to generally accepted knowledge. As a result, his discovery was consigned to the dustbin of premature and unappreciated scientific ideas."
Oh, only if the Internet existed in 1831, Matthew could have blogged away on his ideas.
But this is a very salient idea today as it applies to the rough-and-tumble planetary systems we are finding. Those terrestrial planets though to undergo intense periods of bombardments might be a hotbed of evolution gone wild. Or perhaps there is a "catastrophe rate limit" beyond which life suffers arrested development.
Age of the Exoplanet
This is one of the biggest motivations I can image for undertaking a many-centuries-long program of understanding the evolutionary history of nearby Earth-like planets. This would require extraordinarily sophisticated survey robots that would scrutinize a planet’s biosphere. Other robots would have to probe a planet’s geologic past, and the architecture of the home planetary system.
Therefore, simply finding circumstantial evidence of microbial activity on other worlds will become intellectually dissatisfying to future scientists.
Perhaps on the millennial celebration of Darwin’s work -- or instead Matthew’s work -- our distance descendants will have a truly universal concept of how life evolves in a range of planetary environments.
This is a monumental task only dreamt of in science fiction stories. But little might Matthew have imagined that his ideas would be potentially be applicable to worlds whirling around the distant stars.
* The first planet of extra-galactic origin in the Milky Way has been found.
* The planet is located about 2,000 light-years from Earth in the constellation Fornax.
* The finding also challenges theories of planet formation, which hold that stars need more than hydrogen and helium to produce planets.
HIP 13044b is the first planet of any origin found around a star lacking resources beyond hydrogen and helium. Click to enlarge this image.
Between six billion and nine billion years ago, the Milky Way and another smaller galaxy found themselves at approximately the same place at approximately the same time.
Our galaxy emerged the victor, taking with it some spoils of war -- stars and material from the crushed galaxy -- which even to this day remain not quite meshed into the Milky Way's overall churn and flow. Scientists now discover there was a tag-along as well: a Jupiter-like planet known as HIP 13044b.
Like most of the 500 or so planets that have been discovered beyond our solar system, not much is know about the adoptee, which was found by measuring the slight gravitational tugs it exerts on its parent star.
But astronomers suspect it's a survivor. Not only did HIP 13044b successfully migrate from its galaxy of origin to ours, the planet also apparently survived the brutal ballooning of its parent, which has transitioned from a hydrogen-burning middle-aged star into a helium-fueled senior citizen known as a red giant.
Our own sun will undergo a similar change of life in another five billion years or so.
HIP 13044b's existence is bit of a mystery too, since it is the first planet of any origin found around a star lacking resources beyond hydrogen and helium. Such so-called "metal-poor" stars weren't believed to have the right stuff to produce planets.
"More statistics are needed to really find out how likely it is for metal-poor stars to form planets," study co-author Rainer Klement, with the Max-Planck-Institut für Astronomie, told Discovery News. "I think this will be the biggest impact of the research."
"They did an extremely careful job," added exoplanet-hunter Sara Seager, with the Massachusetts Institute of Technology. "They seemed to have gone through the scenarios very carefully."
The transplanted planet, which is at least 1.25 times the mass of Jupiter, lies about 2000 light-years from Earth in the southern constellation of Fornax, also known as the Furnance.
Lead researcher Johny Setiawan, also from Max Planck, and colleagues remain on the hunt for any HIP 13044b sibling planets -- those that are still around anyway. From the spin rate of the parent star, which is faster than it should be, scientists think the red giant already has consumed some of HIP 13044b's sisters.
NASA’s WISE infrared space telescope is losing its refrigeration, but its backlog of data is still yielding cool images such this one of an odd, blobby, jellyfish-like nebula.
“I just happened to look up one of my favorite objects in our WISE catalogue and was shocked to see these odd rings,” said Michael Ressler, a member of the WISE science team at NASA’s Jet Propulsion Lab, in a press release.
The object, called the “Crystal Ball” nebula or NGC1514, is a planetary nebula located 800 light-years away in the constellation Taurus. Planetary nebulas form when a dying star puffs off its outer layers of material and illuminates the gaseous cloud from within. They’re called “planetary” because the first such objects discovered were roughly spherical, like a planet, although nebulas with lopsided wings are now known to be common.
In visible light (left image), NGC 1514 looked a lot like any other asymmetrical nebula. But WISE’s infrared image (right) shows loopy rings surrounding NGC 1514 that are unlike anything astronomers had seen before.
“This object has been studied for more than 200 years, but WISE shows us it still has surprises,” Ressler said. The observations are reported Nov. 9 in the Astronomical Journal.
The rings could be dust ejected from a pair of dying stars at the nebula’s center, one a giant star heavier and hotter than the sun, the other a dense white dwarf. The giant star sheds some outer layers as it ages to form a bubble around the two stars. Jets of material from the white dwarf are thought to have smashed into the bubble, forming the rings that glow orange in the WISE image.
The green cloud is an inner shell of previously shed material, which shows up in light blue in the visible image.
The rings went undetected until WISE because their dust is heated and glows with the infrared light that WISE can detect. In this image, infrared light with a wavelength of 3.4 micrometers is blue; 4.6-micrometer light is turquoise; 12-micrometer light is green and 22-micrometer light is red. In visible-light images, the rings are washed out by the bright clouds of gas.
Many more surprises lurk in the piles of data WISE collected between January and October of this year. The first batch of data will be released to the astronomical community in spring 2011. Meanwhile, WISE — which ran out of coolant in late September and is now too warm for two of its infrared cameras to function — is continuing on as NEOWISE, searching for near-Earth objects like asteroids and comets.