Jun 1, 2013

Even With Defects, Graphene Is Strongest Material in the World

In a new study, published in Science, Columbia Engineering researchers demonstrate that graphene, even if stitched together from many small crystalline grains, is almost as strong as graphene in its perfect crystalline form. This work resolves a contradiction between theoretical simulations, which predicted that grain boundaries can be strong, and earlier experiments, which indicated that they were much weaker than the perfect lattice.

Graphene consists of a single atomic layer of carbon, arranged in a honeycomb lattice. "Our first Science paper, in 2008, studied the strength graphene can achieve if it has no defects -- its intrinsic strength," says James Hone, professor of mechanical engineering, who led the study with Jeffrey Kysar, professor of mechanical engineering. "But defect-free, pristine graphene exists only in very small areas. Large-area sheets required for applications must contain many small grains connected at grain boundaries, and it was unclear how strong those grain boundaries were. This, our second Science paper, reports on the strength of large-area graphene films grown using chemical vapor deposition (CVD), and we're excited to say that graphene is back and stronger than ever."

The study verifies that commonly used methods for post-processing CVD-grown graphene weaken grain boundaries, resulting in the extremely low strength seen in previous studies. The Columbia Engineering team developed a new process that prevents any damage of graphene during transfer. "We substituted a different etchant and were able to create test samples without harming the graphene," notes the paper's lead author, Gwan-Hyoung Lee, a postdoctoral fellow in the Hone lab. "Our findings clearly correct the mistaken consensus that grain boundaries of graphene are weak. This is great news because graphene offers such a plethora of opportunities both for fundamental scientific research and industrial applications."

In its perfect crystalline form, graphene (a one-atom-thick carbon layer) is the strongest material ever measured, as the Columbia Engineering team reported in Science in 2008 -- so strong that, as Hone observed, "it would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap." For the first study, the team obtained small, structurally perfect flakes of graphene by mechanical exfoliation, or mechanical peeling, from a crystal of graphite. But exfoliation is a time-consuming process that will never be practical for any of the many potential applications of graphene that require industrial mass production.

Currently, scientists can grow sheets of graphene as large as a television screen by using chemical vapor deposition (CVD), in which single layers of graphene are grown on copper substrates in a high-temperature furnace. One of the first applications of graphene may be as a conducting layer in flexible displays.

"But CVD graphene is 'stitched' together from many small crystalline grains -- like a quilt -- at grain boundaries that contain defects in the atomic structure," Kysar explains. "These grain boundaries can severely limit the strength of large-area graphene if they break much more easily than the perfect crystal lattice, and so there has been intense interest in understanding how strong they can be."

The Columbia Engineering team wanted to discover what was making CVD graphene so weak. In studying the processing techniques used to create their samples for testing, they found that the chemical most commonly used to remove the copper substrate also causes damage to the graphene, severely degrading its strength.

Their experiments demonstrated that CVD graphene with large grains is exactly as strong as exfoliated graphene, showing that its crystal lattice is just as perfect. And, more surprisingly, their experiments also showed that CVD graphene with small grains, even when tested right at a grain boundary, is about 90% as strong as the ideal crystal.

"This is an exciting result for the future of graphene, because it provides experimental evidence that the exceptional strength it possesses at the atomic scale can persist all the way up to samples inches or more in size," says Hone. "This strength will be invaluable as scientists continue to develop new flexible electronics and ultrastrong composite materials."

Strong, large-area graphene can be used for a wide variety of applications such as flexible electronics and strengthening components -- potentially, a television screen that rolls up like a poster or ultrastrong composites that could replace carbon fiber. Or, the researchers speculate, a science fiction idea of a space elevator that could connect an orbiting satellite to Earth by a long cord that might consist of sheets of CVD graphene, since graphene (and its cousin material, carbon nanotubes) is the only material with the high strength-to-weight ratio required for this kind of hypothetical application.

Read more at Science Daily

First Glimpse of Moving Starlight

The entire cosmos is filled with light that has never been seen. Every star in every galaxy that’s ever existed in our universe has emitted starlight. Curious as it may sound, almost all of that light is still traveling through the cosmos. Yet remarkably enough, a group of researchers has managed to get a glimpse of this starlight as it’s still traveling.

This sea of photons, some newly created, some fantastically ancient, which surrounds everything is known as Extragalactic Background Light (or EBL for short). In a similar way to the Cosmic Microwave Background (CMB) — the leftover radiation from the big bang — measuring the EBL is rather important in cosmology.

Most recently, new research published by Alberto Dominguez, together with six co-authors, gives the best measurement ever made of this background light, showing how the EBL has varied over the past 5 billion years!

Measuring Light Before it Reaches You

Physicists consider light to be comprised of tiny, discreet packets of energy, referred to as photons. Photons that reach our eyes, we see. Whether emitted by shining stars, generated by computer screens, or reflected from surfaces, these photons allow us our view of the Universe. But unless they reach our eyes, we’d never even know they were there.

Consider that thought, and you might realize that our universe is actually filled with photons. Because space is mostly empty, most of the photons leaving a star like the Sun will never land on any surface. Only a small percentage illuminate planets like ours, and the number which reach planets around other stars is infinitesimal, compared to the total number of photons the Sun produces. Soon enough, these photons will actually leave the galaxy. Once they do, they become denizens of intergalactic space, with only a tiny chance of ever entering another galaxy.

Needless to say, seeing light while it’s still traveling is no easy task. In fact, it’s actually impossible to measure directly. In order to glimpse the EBL, Dominguez’s team needed to take some rather ingenious measures. They turned their attention to a type of galaxy known as a blazar.

Blazars are distant galaxies whose central supermassive black holes are pointed directly towards Earth. This means that intensely bright light emitted by those black holes is easy to spot, even from halfway across the Universe.

By looking at gamma rays emitted by those blazars — or more specifically, the attenuation of certain energies of gamma ray — the scientistss managed to accurately gauge what photons were in the intergalactic space between us and the blazars.

Gamma Ray Attenuation

Attenuation simply means that between us and the blazar, photons have been absorbed, meaning the light appears less intense than it should. The precise reason for this lies in the rather bizarre realm of quantum physics.

The universe at the quantum level, is a very strange place indeed. Einstein’s theory of relativity famously states that E = mc² — or in other words, mass and energy are two sides of the same coin. In deep space, photons are so numerous that they may collide with each other. When they do, if the combined energy of the two photons is high enough, they can spontaneously create matter (this is studied in a field known as two photon physics).

When photons create matter this way, they produce a pair of matter and anti-matter particles which then proceed to go their separate ways. Only photons with specific energies can interact in this way — so by looking at blazars and measuring which gamma ray wavelengths are attenuated, Dominguez and his colleagues could work backwards and find out which photons they were interacting with.

This gives an indirect measure of which photons were a part of the EBL that the blazar light traveled through. Because light only travels at a finite speed, looking at more distant blazars allows the EBL to be measured further away.

For a long time, this gamma ray attenuation had only ever been predicted. Until late last year, when observations taken with the Fermi gamma ray observatory confirmed that gamma rays from distant blazars are indeed absorbed before they reach us.

The Cosmic Gamma Ray Horizon

In order to actually measure the gamma ray attenuation, Dominguez and company first had to look at the blazars at lower energies, using a variety of different telescopes. Looking at x rays and other lower energy photons, they managed to calculate how bright the blazars should appear at gamma ray energies.

They then used several more telescopes to directly observe how bright the blazars are in gamma rays. The difference between the predicted and observed brightnesses gave the attenuation and, in turn, the EBL which would have caused that attenuation.

This research gives the first ever significant detection of a region of space known as the Cosmic Gamma Ray Horizon — the distance at which roughly one third of gamma rays at a certain specific energy have been absorbed.

By looking at the EBL over the past 5 billion years, cosmologists can learn about how galaxies change as the Universe ages. Whether or not ancient galaxies work the same way as modern ones is very important to our understanding of the Universe.

As it happens, the kinds of galaxies observed in the Universe today are responsible for most of the extragalactic background light over all time. Because there’s still a lot out there in the Universe which we don’t fully understand, it also sets a limit on any other light sources which we may not yet know about.

Read more at Discovery News

May 31, 2013

One of the Moon's Mysteries Solved: Origin of Mascon Basins

A mystery of the moon that imperiled astronauts and spacecraft on lunar missions has been solved by a Purdue University-led team of scientists as part of NASA's GRAIL mission.

Large concentrations of mass lurk on the lunar surface hidden like coral reefs beneath the ocean waves -- an unseen and devastating hazard. These concentrations change the gravity field and can either pull a spacecraft in or push it off course, sealing its fate to a crash on the face of the moon.

"In 1968 these mass concentrations were an unwelcome discovery as scientists prepared for the Apollo landings, and they have remained a mystery ever since," said Jay Melosh, a member of the Gravity Recovery and Interior Laboratory, or GRAIL, science team who led the research. "GRAIL has now mapped where they lay, and we have a much better understanding of how they developed. If we return to the moon, we can now navigate with great precision."

A better understanding of these features also adds clues to the moon's origin and evolution and will be useful in studying other planets where mass concentrations also are known to exist including Mars and Mercury, said Melosh, who is a distinguished professor of earth, atmospheric and planetary sciences and physics.

"We now know the ancient moon must have been much hotter than it is now and the crust thinner than we thought," he said. "For the first time we can figure out what size asteroids hit the moon by looking at the basins left behind and the gravity signature of the areas. We now have tools to figure out more about the heavy asteroid bombardment and what the ancient Earth may have faced."

The team confirmed the standing theory that the concentrations of mass were caused by massive asteroid impacts billions of years ago and determined how these impacts changed the density of material on the moon's surface and, in turn, its gravity field. A paper detailing the results will be published online by the journal Science on May 30.

In addition to Melosh, Purdue team members include Andrew Freed, associate professor of earth, atmospheric and planetary sciences, and graduate students Brandon Johnson and David Blair. Additional team members include Maria Zuber, GRAIL principal investigator and professor at the Massachusetts Institute of Technology; J. Andrews-Hanna of the Colorado School of Mines; S. Solomon of Columbia University; and the GRAIL Science Team.

"The explanation of mascons has eluded scientists for decades," Zuber said. "Since their initial discovery they have also been observed on Mars and Mercury, and by understanding their formation on the moon we have greatly advanced knowledge of how major impacts modified planetary crusts."

The mass concentrations form a target pattern with a gravity surplus at the bulls-eye surrounded by a ring of gravity deficit and an outer ring of gravity surplus. The team found that this pattern arises as a natural consequence of crater excavation, collapse and cooling following an impact.

The team determined that the increase in density and gravitational pull at the bulls-eye was caused by lunar material melted from the heat of the asteroid impact. The melting causes the material to become more concentrated, stronger and denser, and pulls in additional material from the surrounding areas, Melosh said.

The large asteroid impacts also caused big holes into which the surrounding lunar material collapsed. As the cool, strong lunar crust slid into the holes it bent downward, forming a rigid, curved edge that held down the material beneath it and prevented it from fully rebounding to its original surface height. This causes a ring with less gravitational pull because the mass is held farther below the surface, the top of which is what most influences the gravitational signature, he said.

The outer ring of increased gravitational pull comes from the added mass of the material ejected by the initial impact that then piles on top of the lunar surface.

The team combined expertise in specialized computer analysis methods called hydrocodes and finite element codes to create computer simulations that could show the physical changes occurring from microseconds to millions of years. The team analyzed the Freundlich-Sharanov and Humorum mascon basins.

Melosh is a pioneer in adapting computer hydrocodes -- computer programs originally created to analyze the flow of liquids -- to simulate how complex materials move when high-speed collisions occur, like that of a planetary collision. Hydrocodes can be used to study such phenomena on a time scale of microseconds to hours, but are not practical from time scales much longer than that, he said.

Read more at Science Daily

Researchers Coax Clays to Make Human Bone

Weak bones, broken bones, damaged bones, arthritic bones. Whether damaged by injury, disease or age, your adult body can't create entirely new bone, but maybe science can. Researchers at North Dakota State University, Fargo, are making strides in tissue engineering, designing scaffolds that may lead to ways to regenerate bone. Published in the Journal of Biomedical Materials Research Part A, the research of Dr. Kalpana Katti, Dr. Dinesh Katti and graduate student Avinash Ambre includes a novel method that uses nanosized clays to make scaffolds to mineralize bone minerals such as hydroxyapatite.

The NDSU research team's 3-D mesh scaffold is composed of degradable materials that are compatible to human tissue. Over time, the cells generate bone and the scaffold deteriorates. As indicated in the NDSU team's published scientific research from 2008 to 2013, the nanoclays enhance the mechanical properties of the scaffold by enabling scaffold to bear load while bone generates. An interesting finding by the Katti group has shown that the nanoclays also impart useful biological properties to the scaffold.

"The biomineralized nanoclays also impart osteogenic or bone-forming abilities to the scaffold to enable birth of bone," said Dr. Kalpana Katti, Distinguished Professor of civil engineering at NDSU. "Although it would have been exciting to say that this finding had a 'Eureka moment,' this discovery was a methodical exploration of simulations and modeling, indicating that amino acid modified nanoclays are viable new nanomaterials," said Katti. The work was initially published in the Journal of Biomacromolecules in 2005. The current findings point toward the potential use of nanoclays for broader applications in medicine.

The NDSU's group most recent study in the Journal of Biomedical Materials Research Part A, published online Feb. 15, 2013, reports that nanoclays mediate human mesenchymal stem cell differentiation into bone cells and grow bone. The Katti research group uses amino acids, the building blocks of life, to modify clay structures and the modified nanoclays coax new bone growth. "Our current research studies underway involve the use of bioreactors that mimic fluid/blood flow in the human body during bone tissue regeneration," said Dr. Kalpana Katti.

The Katti group at NDSU has pioneered the use of nanoclays in bone regeneration since 2008, with research results appearing in Biomedical Materials, ASME Journal of Nanotechnology for Engineering and Medicine, Materials Science and Engineering C, along with the February 2013 publication in the Journal of Biomedical Materials Research Part A.

Read more at Science Daily

Science vs. Fiction: 'After Earth'

What happens if the planet turns on us?

The sci-fi adventure film "After Earth," a kind of family affair starring Will Smith and his son Jaden Smith, is really two movies in one. The film's bookend segments are set aboard interstellar spacecraft with high-tech gadgetry, a thousand or so years into the future.

But the film's middle passages involve conjecture on biology, ecology and a particularly intriguing premise: What would happen if the Earth, as an organism, evolved to defend itself against the harmful human species? We take a look at the film's blend of biological and technological fiction to see if there's any basis in reality.

Predatory plants

Fiction: In several early scenes, Kitai is seen running through beautiful but deadly forest glades in which predatory plants appear to have limited movement and even locomotion.

Science: There are more than 400 known species of carnivorous plants -- or more accurately, insectovorous plants -- which consume their prey through a chemical process similar to digestion. All plants move, of course, but usually too slowly to be discerned without the help of time-lapse photography. But there are exceptions: Several underwater plant species move about visibly, in still water, and the famous Venus fly trap snaps shut in less than half a second when capturing its prey.
Columbia Pictures

Oxygen boost inhalers

Fiction: In the film, Kitai discovers that the Earth's atmosphere has adapted in at least one specific way to discourage human habitation -- there's not enough oxygen to survive. So he must use a futuristic inhaler which, his father explains, will coat his lungs and boost oxygen absorption.

Science: Modern asthma inhalers don't technically increase oxygen absorption into the bloodstream, but they do facilitate lung function by way of two main types of aerosolized medication: Bronchodilators relax muscle constriction, and anti-inflammatory agents suppress

Read more at Discovery News

Visiting Asteroid Has a Moon

A large asteroid that will sail relatively close past Earth on Friday is not alone. Radar images taken by astronomers on Wednesday revealed the asteroid, known as 1998 QE2, is accompanied by an orbiting moon.

“It was quite a surprise,” Marina Brozovic, a radar scientist with NASA’s Jet Propulsion Laboratory in Pasadena, Calif., said during an NASA interview.

“This is something we did not expect,” she said.

The pair will come as close as about 3.6 million miles to Earth at 4:59 p.m. EDT on Friday. That’s just 15 times farther away than Earth’s moon.

“For an asteroid of this size, it’s a close shave,” said Paul Chodas with NASA’s Near Earth Object program office at JPL.

Measuring about 1.7 miles in diameter, 1998 QE2 is among the largest asteroids with orbits that can pass near Earth.

At its most distant, 1998 QE2 flies to  the far edge of the Main Asteroid Belt, nearly to Jupiter. Its pass on Friday is expected to be its closest approach to Earth for at least the next 200 years.

“For the foreseeable future, there’s nothing to worry about,” Chodas said.

Asteroid 1998 QE2 was not named after the United Kingdom’s Queen Elizabeth II, or the QE2 cruise ship. The designation stems from the date and place of its discovery –  1998 by the Massachusetts Institute of Technology Lincoln Near Earth Asteroid Research (LINEAR) program.

Astronomers are hoping to get images and data during the flyby that rival what a visiting spacecraft could collect.

From Discovery News

May 30, 2013

How Turtles Got Their Shells

Turtle shells, which turn out to be complex structures made up of 50 bones, evolved long before dinosaurs roamed the earth, according to new research.

Turtles and their shells now predate the Jurassic period, according to a study in the latest issue of Current Biology. It’s a body design that was built to last, representing millions of years of fine-tuning.

Turtle shells began their transformation more than 260 million years ago in the Permian period, said Tyler Lyson, of Yale University and the Smithsonian, in a press release. “Like other complex structures, the shell evolved over millions of years and was gradually modified into its present-day shape.”

The shell looks like just one solid shield, but because it’s made up of multiple bones, it is formed through the fusion of the turtle’s ribs and vertebrae.

“The reason, I think, that more animals don’t form a shell via the broadening and eventually suturing together of the ribs is that the ribs of mammals and lizards are used to help ventilate the lungs,” Lyson said. “If you incorporate your ribs into a protective shell, then you have to find a new way to breathe!”

He explained that turtles have done just that, with the help of a muscular sling.

That  system evolved in relatives of the turtle such as Eunotosaurus. Discovery of a well-preserved fossil of this extinct South African reptile allowed Lyson and his team to fill a 55-million-year-old gap in the turtle fossil record, showing how the shell formed.

Before the find, the world’s oldest known turtle ancestor was Odontochelys semitestacea, a reptile about 220 million years old. It had a fully developed plastron – the belly side of the shell — but only a partial carapace on its back.

Like turtles, Eunotosaurus had nine broadened ribs and lacked intercostal muscles that run between ribs in certain other animals.

Read more at Discovery News

Ancient Egyptians Crafted Jewelry From Meteorites

An ancient Egyptian iron bead found inside a 5,000-year-old tomb was crafted from a meteorite, new research shows.

The tube-shaped piece of jewelry was first discovered in 1911 at the Gerzeh cemetery, roughly 40 miles (70 kilometers) south of Cairo. Dating between 3350 B.C. and 3600 B.C., beads found at the burial site represent the first known examples of iron use in ancient Egypt, thousands of years before Egypt's Iron Age. And their cosmic origins were suspected from the start.

Soon after the beads were discovered, researchers showed that the metal jewelry was rich in nickel, a signature of iron meteorites. But in the 1980s, academics cast doubt on the beads' celestial source, arguing that the high nickel content could have been the result of smelting.

Scientists from the Open University and the University of Manchester recently analyzed one of the beads with an electron microscope and an X-ray CT scanner. They say the nickel-rich chemical composition of the bead's original metal confirms its meteorite origins.

What's more, the researchers say the bead had a Widmanstätten pattern, a distinctive crystal structure found only in meteorites that cooled at an extremely slow rate inside asteroids when the solar system was forming, according to Nature. Further investigation also showed that the bead was not molded under heat, but rather hammered into shape by cold-working.

The first record of iron smelting in ancient Egypt comes from the sixth century B.C., and iron artifacts from before that time are quite rare, Nature reported.

"Today, we see iron first and foremost as a practical, rather dull metal," study researcher Joyce Tyldesley, an Egyptologist at the University of Manchester, said in a statement. "To the ancient Egyptians, however, it was a rare and beautiful material which, as it fell from the sky, surely had some magical/religious properties."

The iron beads' inclusion in burials also suggests this material was deeply important to ancient Egyptians, Tyldesley added.

Read more at Discovery News

Volcanic Bulges Seen With Microwaves

Don’t try this at home. Your microwave oven uses shorter waves than the L-band microwaves that last March scanned the deadly Galeras volcano in Columbia in the greener image above. The other image is in visible light (on a rare clear day in this area). The microwaves are being used by researchers at NASA to study the land surface, among other things, which is particularly useful when you are dealing with an active volcano, like Galeras, which has a recent history of eruptions and is currently at alert level III. In the last two weeks low level seismicity has accompanied small ash and gas plumes rising from the crater.

L-band microwaves are like those used by a car’s GPS receiver. They can be used to penetrate forest canopies to measure the ground below. So rain or shine, forest or no, detecting even the small changes in the land surface can be done by taking a series of microwave images to see if there is any bulging ground, which is caused by magma rising from below. Such bulges can signal a coming eruption, and so detecting them early is a valuable tool for warning people and saving lives.

The Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) captured the data for the green, false-color microwave image on March 13, 2013, while on board a NASA Gulfstream C-20A aircraft. UAVSAR has a spatial resolution of 6 meters (20 feet) per pixel.

The natural color image was made in 2002 by the Enhanced Thematic Mapper Plus on the Landsat 7 satellite. Landsat 7′s resolution is 30 meters per pixel.

From Discovery News

Is Mars Infested With Pareidolia Rats?

It has finally happened. Not content with (potentially) infecting the pristine Martian surface with our germs, it appears that we’ve sent a rat (yes, a whole rat) to the Red Planet. And this isn’t some far-fetched hypothesis, there’s photographic evidence!

NASA’s Mars rover Curiosity snapped this panorama (above) of the “Rocknest” site with its MastCam camera on sol 52 (Sept. 28, 2012) of the mission. Now, with a keen eye and fertile imagination, a UFO enthusiast realized there was a camouflaged rodent hiding in the rocks. Needless to say, there’s no other evidence supporting this claim, it’s just something that looks like a rodent.

But as you may have guessed, after exercising an ounce of logical thought, what was once a cute furry four-legged creature suddenly becomes… wait for it… this is a good one… a rock. And there you have it ladies and gentlemen: We’ve found a rock on Mars… that looks like a rat.

This certainly isn’t the first time shapes on Mars have fooled the brains of many. What’s more, there’s a name for this psychological phenomenon: pareidolia — possibly an evolutionary trait.

This psychological oddity makes us see familiar objects in apparently random shapes, such as Mars yetis, faces, elephants, black ops bases and parrots on Mars. Pareidolia is the same thing that makes us see the face of Jesus Christ in burnt toast and bunnies in clouds.

Perhaps it’s time to engage some upper-level reasoning and realize that just because there’s a rock on Mars that looks like a rat (whether its a trick of the light, or if it’s genuinely shaped like a small mammal), it doesn’t mean that it is a rat. There is also the possibility that the whole “Mars rat” thing isn’t serious at all and judging by the way the initial report is worded, it could go either way.

Regardless, the story is now in the mainstream and it’s highly likely that our Mars rat will soon get his own Twitter account. Therefore, it’s worth reminding the world that Mars cannot support complex biology like rodents and it’s highly unlikely that any basic lifeforms can be found on the Red Planet’s barren surface today (although there may be some pockets of modern day habitability below the surface).

Read more at Discovery News

May 29, 2013

Arctic Current Flowed Under Deep Freeze of Last Ice Age, Study Says

During the last ice age, when thick ice covered the Arctic, many scientists assumed that the deep currents below that feed the North Atlantic Ocean and help drive global ocean currents slowed or even stopped. But in a new study in Nature, researchers show that the deep Arctic Ocean has been churning briskly for the last 35,000 years, through the chill of the last ice age and warmth of modern times, suggesting that at least one arm of the system of global ocean currents that move heat around the planet has behaved similarly under vastly different climates.

"The Arctic Ocean must have been flushed at approximately the same rate it is today regardless of how different things were at the surface," said study co-author Jerry McManus, a geochemist at Columbia University's Lamont-Doherty Earth Observatory.

Researchers reconstructed Arctic circulation through deep time by measuring radioactive trace elements buried in sediments on the Arctic seafloor. Uranium eroded from the continents and delivered to the ocean by rivers, decays into sister elements thorium and protactinium. Thorium and protactinium eventually attach to particles falling through the water and wind up in mud at the bottom. By comparing expected ratios of thorium and protactinium in those ocean sediments to observed amounts, the authors showed that protactinium was being swept out of the Arctic before it could settle to the ocean bottom. From the amount of missing protactinium, scientists can infer how quickly the overlying water must have been flushed at the time the sediments were accumulating.

"The water couldn't have been stagnant, because we see the export of protactinium," said the study's lead author, Sharon Hoffmann, a geochemist at Lamont-Doherty.

The upper part of the modern Arctic Ocean is flushed by North Atlantic currents while the Arctic's deep basins are flushed by salty currents formed during sea ice formation at the surface. "The study shows that both mechanisms must have been active from the height of glaciation until now," said Robert Newton, an oceanographer at Lamont-Doherty who was not involved in the research. "There must have been significant melt-back of sea ice each summer even at the height of the last ice age to have sea ice formation on the shelves each year. This will be a surprise to many Arctic researchers who believe deep water formation shuts down during glaciations."

The researchers analyzed sediment cores collected during the U.S.-Canada Arctic Ocean Section cruise in 1994, a major Arctic research expedition that involved several Lamont-Doherty scientists. In each location, the cores showed that protactinium has been lower than expected for at least the past 35,000 years. By sampling cores from a range of depths, including the bottom of the Arctic deep basins, the researchers show that even the deepest waters were being flushed out at about the same rate as in the modern Arctic.

The only deep exit from the Arctic is through Fram Strait, which divides Greenland and Norway's Svalbard islands. The deep waters of the modern Arctic flow into the North Atlantic via the Nordic seas, contributing up to 40 percent of the water that becomes North Atlantic Deep Water -- known as the "ocean's lungs" for delivering oxygen and salt to the rest of world's oceans.

Read more at Science Daily

Woolly Mammoth Blood Found in Preserved Carcass

Russian scientists claim to have discovered blood in the carcass of a woolly mammoth, adding that the rare find could boost their chances of cloning the prehistoric animal.

An expedition led by Russian scientists earlier this month uncovered the well-preserved carcass of a female mammoth on a remote island in the Arctic Ocean.

Semyon Grigoryev, the head of the expedition, said the animal died at the age of around 60 some 10,000 to 15,000 years ago, and that it was the first time that an old female had been found.

But what was more surprising was that the carcass was so well preserved that it still had blood and muscle tissue.

"When we broke the ice beneath her stomach, the blood flowed out from there, it was very dark," Professor Grigoryev, who is a scientist at the Yakutsk-based Northeastern Federal University, said.

"This is the most astonishing case in my entire life. How was it possible for it to remain in liquid form? And the muscle tissue is also red, the colour of fresh meat," he added.

Prof Grigoryev said that the lower part of the carcass was very well preserved as it ended up in a pool of water that later froze over. The upper part of the body including the back and the head are believed to have been eaten by predators, he added.

"The forelegs and the stomach are well preserved, while the hind part has become a skeleton."

The discovery, Prof Grigoryev said, gives new hope to researchers in their quest to bring the woolly mammoth back to life.

"This find gives us a really good chance of finding live cells which can help us implement this project to clone a mammoth," he said.

"Previous mammoths have not had such well-preserved tissue."

Last year, Prof Grigoryev's Northeastern Federal University signed a deal with cloning pioneer Hwang Woo-Suk of South Korea's Sooam Biotech Research Foundation, who in 2005 created the world's first cloned dog.

In the coming months, mammoth specialists from South Korea, Russia and the United States are expected to study the remains which the Russian scientists are now keeping at an undisclosed northern location.

Read more at Discovery News

World's Earliest Bird Discovered

Textbooks around the world will need changing to reflect the oldest known bird. A new species has knocked Archaeopteryx out of its former top spot.

A small, feathered beast called Aurornis xui, described in the latest issue of Nature, is now believed to be the first known bird.

"Our analyses indicate it as the most primitive bird known,” said co-author Andrea Cau, a vertebrate paleontologist at the Museo Geologico Giovanni Capellini in Italy. "It was a small feathered dinosaur that lived in what is now China about 160 million years ago. It looked like a ground bird, but with a long tail, clawed hands and toothed jaws.”

Cau and colleagues recently analyzed the bird’s remains, which were unearthed at the Tiaojishan Formation of Liaoning Province in northeastern China.

The name Aurornis xui is made up of the words Aurora (Latin for "daybreak”) Ornis (Greek for "bird”) and xui, in honor of Xu Xing, a well-known Chinese paleontologist who specializes in feathered dinosaurs and the non-avian dinosaur-to-bird transition.

The line between non-avian dinosaurs and birds blurs at the mid-to-late Jurassic period, but the researchers believe that both Aurornis and Archaeopteryx were more bird than non-avian dino. Prior to this study, there was some debate over whether Archaeopteryx, which lived 10 to 15 million years after Aurornis, was a bird. The authors of this latest report believe it was.

There is now a clear lineage leading from non-avian dinosaurs to birds, starting with the clade of dinosaurs called Maniraptora ("hand snatchers").

"The maniraptoran theropods are the animals most similar to Archaeopteryx and early birds, and thus are the best candidate as avian ancestors,” Cau said. "In particular, we found that the earliest birds were very similar to the earliest troodontids, a kind of maniraptorans.”

Troodontidae is a family of bird-like dinosaurs with feathers and two clawed limbs for movement on the ground. They had large eyes and laid eggs. This animal family is now thought to consist of the closest relatives of birds.

The study reveals that typical bird flight, powered only by the forelimbs, either evolved at least twice, or was subsequently lost or modified in some other species. It likely emerged when the earliest birds took to the trees.

"According to our scenario, powered flight evolved along the avian lineage after its separation from other maniraptorans,” Cau explained. "Powered flight probably evolved after early birds acquired more arboreal adaptations.”

The new fossils, combined with those of other early avians reveal that the earliest birds were widespread throughout Europe and Asia by the end of the Jurassic. The discovery supports what is seen today: a very far-reaching distribution of birds.

Paleontologist Michael Benton of the University of Bristol, commenting on the new paper, told Discovery News, "This is a very exciting new find from the pre-Archaeopteryx Tiaojishan Formation of China, and it appears to stabilize the phylogenetic tree.”

Read more at Discovery News

While Venus Simmered, Fast-Cooling Earth Thrived

For rocky planets like Earth the key to holding onto water, a prime ingredient for life, is: location, location, location.

This is the conclusion arrived at by a team of Japanese researchers studying why Earth and its sister world Venus ended up so different.

Scientists believe the second and third planets from the sun started more or less as twins, with similar elements and environments, including magma oceans that likely lasted hundreds of millions of years.

But Venus, positioned roughly 67 million miles from the sun, took more time to cool off and solidify its core, thanks to a steamy lower atmosphere that ended up costing the planet all its water. Meanwhile, 25 million miles farther away, Earth cooled more quickly, enabling it to retain its water, a new computer model shows.

Lead researcher Keiko Hamano, with the University of Tokyo, said the idea for the study stemmed from the realization that baby planets’ atmospheres and interiors would interact with each other.

He integrated previously separate studies on planet evolution and came up with a simple model that explains why terrestrial bodies like Venus and Earth, although both located within the sun’s so-called “habitable zone,” where liquid water can exist, ended up so different.

The researchers identified two types of rocky bodies, based solely on distance to a parent star. One type, like Venus, stays molten for a prolonged period of time, which allows its volatiles to escape. The others, like Earth, solidify within several million years, which allows them to keep their water and form oceans.

The study presumes that Earth, located about 93 million miles away from the sun, and Venus, about one-third closer, formed roughly to their present locations.

“There's no reason to think otherwise,” planetary scientist Linda Elkins-Tanton, with the Carnegie Institution for Science in Washington D.C., told Discovery News.

The distance of a planet to its host star is just one of many factors likely to impact its ability to host life. In addition to having the right temperature and conditions for surface water, a planet’s composition, ability to experience plate tectonics and formation of a protective magnetic field also may be key to habitability, Elkins-Tanton points out.

Read more at Discovery News

May 28, 2013

Picking Up a Second Language Is Predicted by Ability to Learn Patterns

Some people seem to pick up a second language with relative ease, while others have a much more difficult time. Now, a new study suggests that learning to understand and read a second language may be driven, at least in part, by our ability to pick up on statistical regularities.

The study is published in Psychological Science, a journal of the Association for Psychological Science.

Some research suggests that learning a second language draws on capacities that are language-specific, while other research suggests that it reflects a more general capacity for learning patterns. According to psychological scientist and lead researcher Ram Frost of Hebrew University, the data from the new study clearly point to the latter:

"These new results suggest that learning a second language is determined to a large extent by an individual ability that is not at all linguistic," says Frost.

In the study, Frost and colleagues used three different tasks to measure how well American students in an overseas program picked up on the structure of words and sounds in Hebrew. The students were tested once in the first semester and again in the second semester.

The students also completed a task that measured their ability to pick up on statistical patterns in visual stimuli. The participants watched a stream of complex shapes that were presented one at a time. Unbeknownst to the participants, the 24 shapes were organized into 8 triplets -- the order of the triplets was randomized, though the shapes within each triplet always appeared in the same sequence. After viewing the stream of shapes, the students were tested to see whether they implicitly picked up the statistical regularities of the shape sequences.

The data revealed a strong association between statistical learning and language learning: Students who were high performers on the shapes task tended to pick up the most Hebrew over the two semesters.

"It's surprising that a short 15-minute test involving the perception of visual shapes could predict to such a large extent which of the students who came to study Hebrew would finish the year with a better grasp of the language," says Frost.

According to the researchers, establishing a link between second language acquisition and a general capacity for statistical learning may have broad implications.

Read more at Science Daily

Evolution Driven by Humans' Unnatural Selections

In the film "After Earth," the main characters return to Earth after the planet has evolved natural defenses against humans.

In real life, plants and animals are evolving in response to human action as well, although with less malicious intent than on the silver screen.

Tuskless Elephants

Criminal armies equipped with high powered weapons have declared war on Earth's largest land animal. Outlaw organizations, such as Joseph Kony's Lord's Resistance Army, sell black market ivory to finance their rampages in Central Africa.

Elephants can't fight back like the creatures in "After Earth," but evolution is helping to make some of them less attractive to poachers. The frequency of female elephants (Loxodonta africana) without tusks increased from 10.5 percent to 38.2 percent in South Luangwa National Park, Zambia, according to research published in the African Journal of Ecology. The tuskless trait appeared to run in families and may have been a result of tuskless females being spared by poachers. Tuskless mothers survived in greater numbers and hence had more tuskless daughters.

Car-Dodging Birds

U.S. Department of Agriculture scientists estimated that 80 million birds die in collisions with motor vehicles in the United States every year. One bird may be evolving to dodge vehicles.

Over the last 30 years, a decreasing number of cliff swallows have been killed along roads in southwestern Nebraska, according to research published in Current Biology. At the same time, ornithologists' measurements of the birds wings have been decreasing. Birds with shorter wings are more nimble.

The study's authors suggested that automobiles may be killing higher numbers of long-winged birds, leaving more of the nimble, nubbier-winged swallows to pass on their genes.

 Not-So-Bighorned Sheep

Like the ivory poachers, bighorn sheep trophy hunters gun for animals that have the most impressive headgear.

Males in some populations of bighorn sheep (Ovis canadensis) no longer grow large horns, which the authors of a 1995 study in Conservation Biology suggested may have resulted from human hunters' unnatural selection. Having no horns could cause problems for males since they butt heads when sparring for dominance and access to females.

Read more at Discovery News

First Evidence of Leopard Eating a Chimp Found

Only rarely have people seen what happens when chimpanzees and leopards come into close quarters in the wilds of Africa. On these occasions, chimpanzees have made loud, fearful calls, or played the aggressor: In one case, chimps even surrounded a leopard den and killed a cub.

But the big-brained primates don't always win: For the first time, scientists have found evidence of a leopard eating a chimpanzee.

In Tanzania's Mahale Mountains National Park, researchers spent 41 days collecting African leopard scat from June to August 2012 (summer internship, anyone?). In one of the cat's "offerings," scientists found several chimpanzee patella and phalanges, corresponding to kneecaps and toe bones, respectively. DNA analysis showed that the bones came from an adult female chimp.

The researchers can't be entirely certain that the leopard hunted down the chimp, because the cats occasionally eat dead animals; in other words, it's possible the chimp keeled over and then became leopard chow. However, the finding has led scientists to re-examine three mysterious wounds incurred by three different chimps in Mahale over the last few years. The wounds were deeper than thought to be possible from fights with other chimps, which is what scientists previously thought had happened.

A 2009 study suggested that chimpanzees face only negligible pressure from predators. If it's indeed true that the leopard ate a live chimp, scientists may need to rethink this view and further examine how predation from leopards, or other animals, might have driven the chimpanzee's evolution, the researchers said. One study from 1993 found evidence of lions eating four chimpanzees, also in Mahale Mountains National Park. The park is one of the few places with ongoing research where the range of leopards and chimpanzees overlap, which helps explain why this was witnessed there.

The new research was published online May 21 in the Journal of Human Evolution.

From Discovery News

Child Abuse Evident in Ancient Egyptian Cemetery

A 2- to 3-year-old child from a Romano-Christian-period cemetery in Dakhleh Oasis, Egypt, shows evidence of physical child abuse, archaeologists have found. The child, who lived around 2,000 years ago, represents the earliest documented case of child abuse in the archaeological record, and the first case ever found in Egypt, researchers say.

The Dakhleh Oasis is one of seven oases in Egypt's Western Desert. The site has seen continuous human occupation since the Neolithic period, making it the focus of several archaeological investigations, said lead researcher Sandra Wheeler, a bioarchaeologist at the University of Central Florida. Moreover, the cemeteries in the oasis allow scientists to take a unique look at the beginnings of Christianity in Egypt.

In particular, the so-called Kellis 2 cemetery, which is located in the Dakhleh Oasis town of Kellis (southwest of Cairo), reflects Christian mortuary practices. For example, "instead of having children in different places, everyone is put in one place, which is an unusual practice at this time," Wheeler told LiveScience. Dating methods using radioactive carbon from skeletons suggest the cemetery was used between A.D. 50 and A.D. 450.

When the researchers came across the abused toddler — labeled "Burial 519" -- in Kellis 2, nothing seemed out of the ordinary at first. But when Wheeler's colleague Tosha Duprasbegan brushing the sand away, she noticed prominent fractures on the child's arms.

"She thought, 'Whoa, this was weird,' and then she found another fracture on the collarbone," Wheeler said. "We have some other kids that show evidence of skeletal trauma, but this is the only one that had these really extreme fracture patterns."

Signs of abuse

The researchers decided to conduct a series of tests on Burial 519, including X-ray work, histology (microscopic study of tissues) and isotopic analyses, which pinpoint metabolic changes that show when the body tried to repair itself. They found a number of bone fractures throughout the body, on places like the humerus (forearm), ribs, pelvis and back.

Whereas no particular fracture is diagnostic of child abuse, the pattern of trauma suggests it occurred. Additionally, the injuries were all in different stages of healing, which further signifies repeated nonaccidental trauma.

One of the more interesting fractures was located on the child's upper arms, in the same spot on each arm, Wheeler said. The fractures were complete, broken all the way through the bone — given that children are more flexible than adults, a complete break like that would have taken a lot of force.

After comparing the injury with the clinical literature, the researchers deduced that someone grabbed the child's arms and used them as handles to shake the child violently. Other fractures were also likely caused by shaking, but some injuries, including those on the ribs and vertebrae, probably came from direct blows.

The archaeologists aren't sure what ultimately killed the toddler. "It could be that last fracture, which is the clavicle fracture," Wheeler said, referring to the collarbone. "Maybe it wasn't a survivable event."

A unique case

Child abuse in the archaeological record is rare. One possible reason, Wheeler said, is that archaeologists didn't really pay much attention to child remains until about 20 years ago, believing that children couldn't tell them much about the past.

A few cases of possible child abuse have since come out of France, Peru and the United Kingdom, all of which date back to medieval times or later. "Certainly, our case has the best context in terms of the archaeology and skeletal analysis," Wheeler said.

Of the 158 juveniles excavated from the Kellis 2 cemetery, Burial 519 is the only one showing signs of repeated nonaccidental trauma, suggesting child abuse wasn't something that occurred throughout the community. The uniqueness of the case supports the general belief that children were a valued part of ancient Egyptian society.

By contrast, though Romans loved their kids immensely, they believed children were born soft and weak, so it was the parents' duty to mold them into adults. They often engaged in such practices as corporal punishment, immobilizing newborn infants on wooden planks to ensure proper growth and routinely bathing the young in cold water as to not soften them with the feel of warm water.

Read more at Discovery News

May 27, 2013

Researchers Identify Genetic Suspects in Sporadic Lou Gehrig's Disease

Researchers at the Stanford University School of Medicine have identified mutations in several new genes that might be associated with the development of spontaneously occurring cases of the neurodegenerative disease known as amyotrophic lateral sclerosis, or ALS. Also known as Lou Gehrig's disease, the progressive, fatal condition, in which the motor neurons that control movement and breathing gradually cease to function, has no cure.

Although researchers know of some mutations associated with inherited forms of ALS, the majority of patients have no family history of the disease, and there are few clues as to its cause. The Stanford researchers compared the DNA sequences of 47 patients who have the spontaneous form of the disease, known as sporadic ALS, with those of their unaffected parents. The goal was to identify new mutations that were present in the patient but not in either parent that may have contributed to disease development.

Several suspects are mutations in genes that encode chromatin regulators -- cellular proteins that govern how DNA is packed into the nucleus of a cell and how it is accessed when genes are expressed. Protein members of one these chromatin-regulatory complexes have recently been shown to play roles in normal development and some forms of cancer.

"The more we know about the genetic causes of the disorder, the greater insight we will have as to possible therapeutic targets," said Aaron Gitler, PhD, associate professor of genetics. "Until now, researchers have primarily relied upon large families with many cases of inherited ALS and attempted to pinpoint genetic regions that seem to occur only in patients. But more than 90 percent of ALS cases are sporadic, and many of the genes involved in these cases are unknown."

Gitler is the senior author of the study, which will be published online May 26 in Nature Neuroscience. Postdoctoral scholar Alessandra Chesi, PhD, is the lead author. Gitler and Chesi collaborated with members of the laboratory of Gerald Crabtree, MD, professor of developmental biology and of pathology. Crabtree, a Howard Hughes Medical Institute investigator, is also a co-author of the study.

Chesi and Gitler combined deductive reasoning with recent advances in sequencing technology to conduct the work, which relied on the availability of genetic samples from not only ALS patients, but also the patients' unaffected parents. Such trios can be difficult to obtain for diseases like sporadic ALS that strike well into adulthood when a patient's parents may no longer be alive. Gitler and Chesi collaborated with researchers from Emory University and Johns Hopkins University to collect these samples.

The researchers compared the sequences of a portion of the genome called the exome, which directly contributes to the amino acid sequences of all the proteins in a cell. (Many genes contain intervening, non-protein-coding regions of DNA called introns that are removed prior to protein production.) Mutations found only in the patient's exome, but not in that of his or her parents', were viewed as potential disease-associated candidates -- particularly if they affected the composition or structure of the resulting protein made from that gene.

Focusing on just the exome, which is about 1 percent of the total amount of DNA in each human cell, vastly reduced the total amount of DNA that needed to be sequenced and allowed the researchers to achieve relatively high coverage (or repeated sequencing to ensure accuracy) of each sample.

"We wanted to find novel changes in the patients," Chesi said. "These represent a class of mutations called de novo mutations that likely occurred during the production of the parents' reproductive cells." As a result, these mutations would be carried in all the cells of patients, but not in their parents or siblings.

Using the exome sequencing technique, the researchers identified 25 de novo mutations in the ALS patients. Of these, five are known to be in genes involved in the regulation of the tightly packed form of DNA called chromatin -- a proportion that is much higher than would have been expected by chance, according to Chesi.

Furthermore, one of the five chromatin regulatory proteins, SS18L1, is a member of a neuron-specific complex called nBAF, which has long been studied in Crabtree's laboratory. This complex is strongly expressed in the brain and spinal cord, and affects the ability of the neurons to form branching structures called dendrites that are essential to nerve signaling.

"We found that, in one sporadic ALS case, the last nine amino acids of this protein are missing," Gitler said. "I knew that Gerald Crabtree's lab had been investigating SS18L1, so I asked him about it. In fact, they had already identified these amino acids as being very important to the function of the protein."

When the researchers expressed the mutant SS18L1 in motor neurons isolated from mouse embryos, they found the neurons were unable to extend and grow new dendrites as robustly as normal neurons in response to stimuli. They also showed that SS18L1 appears to physically interact with another protein known to be involved in cases of familial, or inherited, ALS.

Although the results are intriguing, the researchers caution that more work is necessary to conclusively prove whether and how mutations in SS18L1 contribute to sporadic cases of ALS. But now they have an idea of where to look in other patients, without requiring the existence of patient and parent trios. They are planning to sequence SS18L1 and other candidates in an additional few thousand sporadic ALS cases.

Read more at Science Daily

New Gene Discovery for Babies Born With Hole in the Heart

New gene discovery for babies born with hole in the heart A new gene associated with a form of congenital heart disease in newborn babies -- known as "a hole in the heart" has been discovered by researchers. British Heart Foundation (BHF) Professor Bernard Keavney, from The University of Manchester and Newcastle University, led the research which saw investigators from Newcastle, Nottingham, Oxford and Leicester universities in the UK, together with colleagues in Europe, Australia and Canada pool resources.

The discovery, published in Nature Genetics today, will help lead to better understanding of why some patients are born with the disorder. Congenital heart disease (CHD) is the most common form of congenital malformation, occurring in seven in 1000 babies born and is one of the major causes of childhood death and illness. Most patients born with CHD now survive to adulthood, so identifying the responsible genes is important as experts attempt to provide individual-specific genetic counselling for these people.

In about 20% of cases, a predisposing cause can be identified, for example Down's Syndrome, but in the remainder of patients, although genes are recognised to be important, scientists do not know the identity of these genes. The study, funded by the BHF and the Wellcome Trust, looked at over 2,000 CHD patients and measured over 500,000 genetic markers which vary in the general population. The genetic markers in the patients were compared to the markers of over 5,600 people in good health who acted as a control group.

The researchers found a relationship between a particular region of the human genome and risk of atrial septal defect (ASD) -- a "hole" between the heart's blood-collecting chambers, which they went on to confirm in additional cases of atrial septal defect and healthy controls. BHF Professor Keavney, Director of the Institute of Cardiovascular Sciences at The University of Manchester, said identifying a gene associated with one type of CHD was an important step forward. "We found that a common genetic variation near a gene called Msx1 was strongly associated with the risk of a particular type of CHD called atrial septal defect or hole in the heart," he said. "ASD is one of the most common forms of congenital heart disease, and it carries a risk of heart failure and stroke. We estimated that around 10% of ASDs may be due to the gene we found. We can now work to find out how Msx1 and/or its neighbour genes affect the risk of ASD."

Researchers looked at all the major types of congenial heart disease (CHD), but they did not find a genetic marker common in all types of CHD. Professor Keavney added: "Our work also suggests that if we conduct larger studies we will be able to find genes that cause other types of CHD. Although we are not there yet, further studies may enable us to give better genetic counselling to high risk families. Also, when we identify genes important in the development of the heart because they have gone wrong, it helps us understand normal development better. Such an understanding is fundamental to any attempt to treat people with heart disease at any age -- for example those suffering from heart failure -- using regenerative medicine." Dr Shannon Amoils, Senior Research Advisor at the BHF, which part-funded the study, said: "We've made great strides in treating congenital heart disease; most babies born with a heart defect have a much brighter future now than they would have had in the 1960s when the BHF was founded. But we still need to fund much more research like this, to better understand the fundamental causes of congenital heart defects. "These important results show how large collaborative studies are incredibly useful for uncovering the influence of our genes on congenital heart disease.

Read more at Science Daily

Rats Have a Double View of the World

Scientists from the Max Planck Institute for Biological Cybernetics in Tübingen, using miniaturised high-speed cameras and high-speed behavioural tracking, discovered that rats move their eyes in opposite directions in both the horizontal and the vertical plane when running around. Each eye moves in a different direction, depending on the change in the animal's head position. An analysis of both eyes' field of view found that the eye movements exclude the possibility that rats fuse the visual information into a single image like humans do. Instead, the eyes move in such a way that enables the space above them to be permanently in view -- presumably an adaptation to help them deal with the major threat from predatory birds that rodents face in their natural environment.

Like many mammals, rats have their eyes on the sides of their heads. This gives them a very wide visual field, useful for detection of predators. However, three-dimensional vision requires overlap of the visual fields of the two eyes. Thus, the visual system of these animals needs to meet two conflicting demands at the same time; on the one hand maximum surveillance and on the other hand detailed binocular vision.

The research team from the Max Planck Institute for Biological Cybernetics have now, for the first time, observed and characterised the eye movements of freely moving rats. They fitted minuscule cameras weighing only about one gram to the animals' heads, which could record the lightning-fast eye movements with great precision. The scientists also used another new method to measure the position and direction of the head, enabling them to reconstruct the rats' exact line of view at any given time.

The Max Planck scientists' findings came as a complete surprise. Although rats process visual information from their eyes through very similar brain pathways to other mammals, their eyes evidently move in a totally different way. "Humans move their eyes in a very stereotypical way for both counteracting head movements and searching around. Both our eyes move together and always follow the same object. In rats, on the other hand, the eyes generally move in opposite directions," explains Jason Kerr from the Max Planck Institute for Biological Cybernetics.

In a series of behavioural experiments, the neurobiologists also discovered that the eye movements largely depend on the position of the animal's head. "When the head points downward, the eyes move back, away from the tip of the nose. When the rat lifts its head, the eyes look forward: cross-eyed, so to speak. If the animal puts its head on one side, the eye on the lower side moves up and the other eye moves down." says Jason Kerr.

In humans, the direction in which the eyes look must be precisely aligned, otherwise an object cannot be fixated. A deviation measuring less than a single degree of the field of view is enough to cause double vision. In rats, the opposing eye movements between left and right eye mean that the line of vision varies by as much as 40 degrees in the horizontal plane and up to 60 degrees in the vertical plane. The consequence of these unusual eye movements is that irrespective of vigorous head movements in all planes, the eyes movements always move in such a way to ensure that the area above the animal is always in view simultaneously by both eyes -something that does not occur in any other region of the rat's visual field.

Read more at Science Daily

Climate Researchers Discover New Rhythm for El Niño

El Niño wreaks havoc across the globe, shifting weather patterns that spawn droughts in some regions and floods in others. The impacts of this tropical Pacific climate phenomenon are well known and documented.

A mystery, however, has remained despite decades of research: Why does El Niño always peak around Christmas and end quickly by February to April?

Now there is an answer: An unusual wind pattern that straddles the equatorial Pacific during strong El Niño events and swings back and forth with a period of 15 months explains El Niño's close ties to the annual cycle. This finding is reported in the May 26, 2013, online issue of Nature Geoscience by scientists from the University of Hawai'i at Manoa Meteorology Department and International Pacific Research Center.

"This atmospheric pattern peaks in February and triggers some of the well-known El Niño impacts, such as droughts in the Philippines and across Micronesia and heavy rainfall over French Polynesia," says lead author Malte Stuecker.

When anomalous trade winds shift south they can terminate an El Niño by generating eastward propagating equatorial Kelvin waves that eventually resume upwelling of cold water in the eastern equatorial Pacific. This wind shift is part of the larger, unusual atmospheric pattern accompanying El Niño events, in which a high-pressure system hovers over the Philippines and the major rain band of the South Pacific rapidly shifts equatorward.

With the help of numerical atmospheric models, the scientists discovered that this unusual pattern originates from an interaction between El Niño and the seasonal evolution of temperatures in the western tropical Pacific warm pool.

"Not all El Niño events are accompanied by this unusual wind pattern" notes Malte Stuecker, "but once El Niño conditions reach a certain threshold amplitude during the right time of the year, it is like a jack-in-the-box whose lid pops open."

A study of the evolution of the anomalous wind pattern in the model reveals a rhythm of about 15 months accompanying strong El Niño events, which is considerably faster than the three- to five-year timetable for El Niño events, but slower than the annual cycle.

"This type of variability is known in physics as a combination tone," says Fei-Fei Jin, professor of Meteorology and co-author of the study. Combination tones have been known for more than three centuries. They where discovered by violin builder Tartini, who realized that our ear can create a third tone, even though only two tones are played on a violin.

"The unusual wind pattern straddling the equator during an El Niño is such a combination tone between El Niño events and the seasonal march of the sun across the equator" says co-author Axel Timmermann, climate scientist at the International Pacific Research Center and professor at the Department of Oceanography, University of Hawai'i. He adds, "It turns out that many climate models have difficulties creating the correct combination tone, which is likely to impact their ability to simulate and predict El Niño events and their global impacts."

Read more at Science Daily

May 26, 2013

Cosmic Swirly Straws: Galaxies Fed by Funnels of Fuel

Computer simulations of galaxies growing over billions of years have revealed a likely scenario for how they feed: a cosmic version of swirly straws.

The results show that cold gas -- fuel for stars -- spirals into the cores of galaxies along filaments, rapidly making its way to their "guts." Once there, the gas is converted into new stars, and the galaxies bulk up in mass.

"Galaxy formation is really chaotic," said Kyle Stewart, lead author of the new study appearing in the May 20th issue of the Astrophysical Journal. "It took us several hundred computer processors, over months of time, to simulate and learn more about how this process works." Stewart, who is now at the California Baptist University in Riverside, Calif., completed the majority of this work while at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

In the early universe, galaxies formed out of clumps of matter, connected by filaments in a giant cosmic web. Within the galaxies, nuggets of gas cooled and condensed, becoming dense enough to trigger the birth of stars. Our Milky Way spiral galaxy and its billions of stars took shape in this way.

The previous, standard model of galaxy formation held that hot gas sank into the centers of burgeoning galaxies from all directions. Gas clouds were thought to collide into each other, sending out shock waves, which then heated up the gas. The process is similar to jets creating sonic booms, only in the case of galaxies, the in-falling gas travels faster than the speed of sound, piling up into waves. Eventually, the gas cools and sinks to the galactic center. This process was theorized to be slow, taking up to 8 billion years.

Recent research has contradicted this scenario in smaller galaxies, showing that the gas is not heated. An alternate "cold-mode" theory of galaxy formation was proposed instead, suggesting the cold gas might funnel along filaments into galaxy centers. Stewart and his colleagues set out to test this theory and address the mysteries about how the cold gas gets into galaxies, as well as the rate at which it spirals in.

Since it would take billions of years to watch a galaxy grow, the team simulated the process using supercomputers at JPL; NASA's Ames Research Center, Moffett Field, Calif.; and the University of California, Irvine. They ran four different simulations of the formation of a galaxy like our Milky Way, starting from just 57 million years after the big bang until present day.

The simulations began with the starting ingredients for galaxies -- hydrogen, helium and dark matter -- and then let the laws of physics take over to create their galactic masterpieces. Supercomputers are needed due to the enormous number of interactions.

"The simulations are like a gigantic game of chess," said Alyson Brooks, a co-author of the paper and expert in galaxy simulations at the University of Wisconsin, Madison. "For each point in time, we have to figure out how a given particle -- our chess piece -- should move based on the positions of all of the other particles. There are tens of millions of particles in the simulation, so figuring out how the gravitational forces affect each particle is time-consuming."

When the galaxy concoctions were ready, the researchers inspected the data, finding new clues about how cold gas sinks into the galaxy centers. The new results confirm that cold gas flows along filaments and show, for the first time, that the gas is spinning around faster than previously believed. The simulations also revealed that the gas is making its way down to the centers of galaxies more quickly than what occurs in the "hot-mode" of galaxy formation, in about 1 billion years.

"We have found that the filamentary structures that galaxies are built on are key to how they build up over time, by threading gas into them efficiently," said Leonidas Moustakas, a co-author at JPL.

The researchers looked at dark matter too -- an invisible substance making up about 85 percent of matter in the universe. Galaxies form out of lumps of regular matter, so-called baryonic matter that is composed of atoms, and dark matter. The simulations showed that dark matter is also spinning at a faster rate along the filaments, spiraling into the galaxy centers.

The results help answer a riddle in astronomy about galaxies with large extended disks of material spinning around them, far from their centers. Researchers didn't understand how the outer material could be spinning so fast. The cold-mode allows for this rapid spinning, fitting another jigsaw piece into the puzzle of how galaxies grow.

"The goal of simulating galaxies is to compare them to what telescopes observe and see if we really understand how to build a galaxy," said Stewart. "It helps us makes sense of the real universe."

Read more at Science Daily

Alien Debris Found in Lunar Craters

Strange minerals detected at the centers of impact craters on the moon may be the shattered remains of the space rocks that made the craters and not exhumed bits of the moon's interior, as had been previously thought.

The foreign matter in the craters is probably asteroid debris and some could even be from Earth, which has thrown off its share of material as it's been battered by asteroids and comets over the eons.

The discovery comes not from finding anything new in the craters themselves, but by planetary scientists who were looking at models of how meteorite impacts affect the moon. Specifically, the researchers simulated some high-angle, exceptionally slow impacts -- at least slow compared to possible impact speeds -- and they were surprised at what they found.

"Nobody has done it at such high resolution," said planetary scientist Jay Melosh of Purdue University. Melosh and his colleagues published a paper on the discovery in the May 26 online issue of the journal Nature Geoscience.

They found that when a slow enough impact happened, at speeds of less than 27,000 miles per hour (43,000 kph), the rock that struck doesn't necessarily vaporize. Instead, it gets shattered into a rain of debris that is then swept back down the crater sides and piles up in the crater's central peak.

In the case of craters like Copernicus (pictured top), the foreign material stands out because it contains minerals called spinels. These only form under great pressure -- in the Earth's mantle, for instance, and perhaps in the mantle of the moon. But spinels are also common in some asteroids, said Melosh, which are fragments of broken or failed planets from earlier days in the formation of our solar system.

The team has concluded, therefore, that the unusual minerals observed in the central peaks of many lunar impact craters are not lunar natives, but imports.

That conclusion could also explain why the same minerals, if they were instead from the interior of the moon, are not found in the largest impact basins -- as would be expected if the impact event was larger and penetrated deeper into the moon.

"An origin from within the Moon does not readily explain why the observed spinel deposits are associated with craters like Tycho and Copernicus instead of the largest impact basins," writes Arizona State University researcher Erik Asphaug in a commentary on the paper. "Excavation of deep-seated materials should favor the largest cratering events."

Read more at Discovery News