Frozen Puck Hovers Over Track Using “Quantum Levitation”

12:18:44 AM, Wednesday, October 19, 2011

"Researchers at the school of physics and astronomy at Tel Aviv University have created a track around which a semiconductor can float, thanks to the phenomenon of “quantum levitation“.

This levitation effect is explained by the Meissner effect, which describes how, when a material makes the transition from its normal to its superconducting state, it actively excludes magnetic fields from its interior, leaving only a thin layer on its surface.

When a material is in its superconducting state — which involves very low temperatures — it is strongly diamagnetic. This means that when a magnetic field is externally applied, it will create an equally opposing magnetic field, locking it in place.

A material called yttrium barium copper oxide can be turned into a superconductor by exposure to liquid nitrogen — which makes it one of the highest-temperature superconductors.

In the video it appears that a puck of yttrium barium copper oxide cooled by liquid nitrogen is repelling the magnets embedded on the handheld device. It also shows that the angle of the magnet can be locked in a magnetic field. Later in the video the puck can be seen to zoom round a circular track of magnets, in the same way that Maglev high-speed trains do."

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Frustration Inspires New Form of Graphene

1:45:45 AM, Monday, October 17, 2011

"They're the building block of graphite – ultra-thin sheets of carbon, just one atom thick, whose discovery was lauded in 2010 with a Nobel Prize in Physics.

The seemingly simple material is graphene, and many researchers believe it has great potential for many applications, from electronic devices to high-performance composite materials.

Graphene is extremely strong, an excellent conductor, and with no internal structure at all, it offers an abundance of surface area – much like a sheet of paper.

When it comes to producing and utilizing graphene on a large scale, however, researchers have come upon a major problem: the material's tendency to aggregate. Like paper, graphene sheets easily stack into piles, thus greatly reducing their surface area and making them unprocessable.

Researchers at Northwestern University have now developed a new form of graphene that does not stack. The new material – inspired by a trash can full of crumpled-up papers – is made by crumpling the graphene sheets into balls.

A paper describing the findings, "Compression and Aggregation-resistant Particles of Crumpled Soft Sheets," was published October 13 in the journal ACS Nano.

Graphene-based materials are very easily aggregated due to the strong interaction between the sheets, called "Van der Waals attraction." Therefore, common steps in materials processing, such as heating, solvent washing, compression, and mixing with other materials, can greatly affect how the sheets are stacked. When the paper-like sheets band together – picture a deck of cards – their surface area is lost; with just a fraction of its original surface area available, the material becomes less effective. Stacked graphene sheets also become rigid and lose their processability.

Some scientists have tried to physically keep the sheets apart by inserting non-carbon "spacers" between them, but that changes the chemical composition of the material. When graphene is crumpled into balls, however, its surface area remains available and the material remains pure.

"If you imagine a trash can filled with paper crumples, you really get the idea," says Jiaxing Huang, Morris E. Fine Junior Professor in Materials and Manufacturing, the lead researcher of the study. "The balls can stack up into a tight structure. You can crumple them as hard as you want, but their surface area won't be eliminated, unlike face-to-face stacking."

"Crumpled paper balls usually express an emotion of frustration, a quite common experience in research," Huang says, "However, here 'frustration' quite appropriately describes why these particles are resistant to aggregation – because their uneven surface frustrates or prevents tight face-to-face packing no matter how you process them."

To make crumpled graphene balls, Huang and his team created freely suspended water droplets containing graphene-based sheets, then used a carrier gas to blow the aerosol droplets through a furnace. As the water quickly evaporated, the thin sheets were compressed by capillary force into near-spherical particles..."

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Russia Asked to Join ExoMars Project

12:36:44 AM, Monday, October 17, 2011

"Europe has formally invited Russia to participate in space missions to Mars in 2016 and 2018.

A "yes" from the Russian space agency (Roscosmos) may be the only way of saving the missions which are at risk of cancellation due to lack of funds.

The 2016 mission involves a satellite to study the Martian atmosphere, while a big robot rover to investigate the surface is scheduled for 2018.

Both are being planned with the US, which is also struggling financially.

If Russia can be persuaded to provide a rocket to launch the 2016 satellite, it should make both atmospheric and surface ventures financially feasible.

But the European and US space agencies (Esa and Nasa) know that for Roscosmos to be interested, it will want a meaningful degree of participation.

The in-kind return for Russia would be the opportunity to provide instrumentation and technology for the missions, and for its researchers to be included in the science teams.

"Everything is open for discussion," said Esa director of science, Alvaro Gimenez.

"There are possibilities for the Russians to contribute to the rover; there may also be possibilities for them to contribute to the payload on the orbiter," he told BBC News.

"Of course, in the case of 2016, we don't have much time available to get everything on board; and in the case of 2018, we don't have much room available because it is just a single Esa/Nasa rover.

"That's why we have to start the discussions now, to see what the Russians have available and what they can develop in a fast-track."

Esa's and Nasa's joint Mars programme (known in Europe as ExoMars) has looked increasingly unsteady in recent months.

The US let it be known during the summer that it could no longer afford to provide the rocket to launch the 2016 orbiter; and Europe, which still has not raised the full funds needed for ExoMars among its member states, has no money available to buy a rocket itself..."

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Why Einstein Was Wrong About Being Wrong

12:30:30 AM, Monday, October 17, 2011

"If you want to get your mind around the research that won three astronomers the Nobel Prize in physics last week, it helps to think of the universe as a lump of dough - raisin-bread dough, to be precise - mixed, kneaded and ready to rise. Hold that thought.

Now consider Albert Einstein - not the wild-haired, elderly, absent-minded professor he became in his later years but a young, dashing scientist in his 30s. It's 1916, and he's just published his revolutionary general theory of relativity. It's not necessary to understand the theory (thank goodness). You just have to accept that it gave scientists the mathematical tools they needed to forge a better understanding of the cosmos than they'd ever had.

There was just one problem. Relativity told physicists that the universe was restless. It couldn't just sit there. It either had to be expanding or contracting. But astronomers looked, and as far as they could tell, it was doing neither. The lump of dough wasn't rising, and it wasn't shrinking.

The only way that was possible, Einstein realized, was if some mysterious force was propping up the universe, a sort of antigravity that pushed outward just hard enough to balance the gravity that was trying to pull it inward. Einstein hated this idea. An extra force meant he had to tinker with the equations of general relativity, but the equations seemed so perfect just as they were. Changing them in any way would tarnish their mathematical beauty.

Einstein did it anyway. The universe ought to behave according to the laws he had set out, but it simply wasn't cooperating. The "cosmological constant" - his name for the new antigravity force - became part of the theory.

Then, a decade or so later, the great astronomer Edwin Hubble went up to the Mount Wilson Observatory above Pasadena and used the world's most powerful telescope to peer deeper into the universe than anyone had before. Making excruciatingly careful measurements of the galaxies he could see beyond the Milky Way, Hubble was astonished to learn that they weren't stationary at all. The galaxies - the raisins in the bread dough - were in motion, each moving apart from the other. The dough was rising in all directions, and the raisins were going along for the ride..."

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NanotubeYarns Twist Like Muscles

12:25:17 AM, Monday, October 17, 2011

"Yarns made of the tiny straws of carbon called nanotubes have an astounding ability to twist as they contract, scientists have found.

The effect, reported in Science, is similar to the action of muscles found in elephant trunks and squid tentacles.

However, the yarns twist 1,000 times as much as previous "artificial muscles".

The effect, which occurs thanks to a conducting fluid in which the yarns were dipped, could be put to use in motors much thinner than a human hair.

The team of researchers from Australia, the US, Canada and South Korea demonstrated motors that could spin at nearly 600 revolutions per minute, turning a weight 2,000 times heavier than the yarn itself.

Carbon nanotubes have only recently been identified by scientists; they are "straws" made only of atoms of carbon linked together in hexagons. They have remarkable physical properties - being more than 100 times stronger than steel.

Ray Baughman of the University of Texas at Dallas is a renowned researcher into the tubes' properties, and is a co-author of the new research.

"The carbon nanotube yarns comprise invididual nanotubes - untold billions of them - that are about 1/100,000th the diameter of a human hair," he told the podcast of Science magazine.

The yarns were made by pulling sheets of nanotubes from "forests" of the tubes and twisting them to form a coiled structure - much as yarn is made from wool.

They were then dipped in an electrolyte - a fluid containing ions, electrically charged atoms. When a voltage was applied at the ends of the yarns, these ions moved into the fibres, causing them to expand..."

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Wooden Buildings Reach New Heights

12:19:28 AM, Monday, October 17, 2011

"Soon, the first tenants will start moving into a new block of council flats in Hackney in north London.

Nothing remarkable about that except Bridport House is built of wood, and it is the largest timber-built apartment block in the world.

It is possibly the biggest timber building of any kind.

Not only that, but a few hundred metres away there is another timber-built block of flats, rather smaller overall, but even taller.

Soon high-rise buildings made of wood may replace many conventional concrete and steel structures, even in the UK, a country with few forests and no modern tradition of building in wood."

-- Follow link for video.

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Could a Computer One Day Rewire Itself? New Nanomaterial 'Steers' Electric Currents in Multiple Dimensions

12:11:12 AM, Monday, October 17, 2011

"Scientists at Northwestern University have developed a new nanomaterial that can "steer" electrical currents. The development could lead to a computer that can simply reconfigure its internal wiring and become an entirely different device, based on changing needs.

As electronic devices are built smaller and smaller, the materials from which the circuits are constructed begin to lose their properties and begin to be controlled by quantum mechanical phenomena. Reaching this physical barrier, many scientists have begun building circuits into multiple dimensions, such as stacking components on top of one another.

The Northwestern team has taken a fundamentally different approach. They have made reconfigurable electronic materials: materials that can rearrange themselves to meet different computational needs at different times.

"Our new steering technology allows use to direct current flow through a piece of continuous material," said Bartosz A. Grzybowski, who led the research. "Like redirecting a river, streams of electrons can be steered in multiple directions through a block of the material -- even multiple streams flowing in opposing directions at the same time."

Grzybowski is professor of chemical and biological engineering in the McCormick School of Engineering and Applied Science and professor of chemistry in the Weinberg College of Arts and Sciences.

The Northwestern material combines different aspects of silicon- and polymer-based electronics to create a new classification of electronic materials: nanoparticle-based electronics.

The study, in which the authors report making preliminary electronic components with the hybrid material, will be published online Oct. 16 by the journal Nature Nanotechnology. The research also will be published as the cover story in the November print issue of the journal..."

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New Metal-Eating Bacteria Found on Titanic

3:23:18 AM, Saturday, October 15, 2011

"Bacteria scooped from the wreckage of the Titanic almost 20 years ago have been confirmed as a new species in the December issue of a microbiology journal.

While new scientific discoveries are usually heralded as joyous news, this discovery is bittersweet.

The bacteria, found on the ship's "rusticles" (rust formations that look like icicles), are eating the Titanic.

The strain, dubbed Halomonas titanicae, was initially designated BH1T in honor of the researchers who discovered it, then-graduate student Bhavleen Kaur and Dr. Henrietta Mann at Dalhousie University in Halifax, Canada.

The researchers tested the bacteria to see whether it was "good bacteria" or "bad bacteria," according to the school's website.

Let's just say the bug has an appetite for destruction.

"The BH1 cells stuck to the surface of these [small metal tags] and eventually destroyed the metal. So we knew we had a bad bacteria,” Mann is quoted as saying on the Dalhousie University website.

"In 1995, I was predicting that Titanic had another 30 years," said Mann, who still works at the university, according to CBS News. "But I think it's deteriorating much faster than that now ... Eventually there will be nothing left but a rust stain," she is quoted as saying.

The metal-eating bug presents a dilemma for scientists.

"Letting it proceed with its deterioration is also a learning process," said Kaur, who now works with the Ontario Science Centre, according to National Geographic. "If we stop and preserve it, then we stop the process of degradation," Kaur is quoted as saying.

The findings were published in the December 8 issue of the International Journal of Systematic and Evolutionary Microbiology.

The Titanic, heralded in its day as the largest passenger ship in the world, sank on its maiden voyage in 1912, killing more than 1,500 people. The wreckage was found in 1985 by an expedition team more than 2 miles deep in the Atlantic Ocean."

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Scientists Solve Puzzle of Black Death’s DNA

2:01:39 AM, Saturday, October 15, 2011

"After the Black Death reached London in 1348, about 2,400 people were buried in East Smithfield, near the Tower of London, in a cemetery that had been prepared for the plague’s arrival. From the teeth of four of those victims, researchers have now reconstructed the full DNA of a microbe that within five years felled one-third to one-half of the population of Western Europe.

The bacterium that causes plague, Yersinia pestis, is still highly virulent today but has different symptoms, leading some historians to doubt that it was the agent of the Black Death.

Those doubts were laid to rest last year by detection of the bacterium’s DNA in plague victims from mass graves across Europe. With the full genome now in hand, the researchers hope to recreate the microbe itself so as to understand what made the Black Death outbreak so deadly.

So far, the evidence points more toward the conditions of the time than to properties of the bacterium itself. The genome recovered from the East Smithfield victims is remarkably similar to that of the present-day bacterium, says the research team, led by Kirsten I. Bos of McMaster University in Ontario and Johannes Krause of the University of Tübingen in Germany.

This is the first time the genome of an ancient pathogen has been reconstructed, opening the way to tracking other ancient epidemics and how their microbes adapted to human hosts.

The bacterium’s genome consists of a single chromosome, about 4.6 million DNA units long, and three small rings of DNA called plasmids. In the 660 years since the Black Death struck, only 97 of these DNA units have changed and only a dozen of these changes occur in genes and therefore would affect the organism’s physical properties, the researchers report in Wednesday’s issue of the journal Nature. Dr. Krause and others reported the DNA sequence of one of the plasmids in August. The changes in the genome will be studied one by one to see how each affects the microbe’s virulence.

The researchers hope eventually to modify a living plague bacterium so that its genome is identical to that of the agent of the Black Death. Such a microbe could be handled only in special secure facilities. But even if it did infect a person, the bacterium would be susceptible to antibiotics, like its living descendants, said Hendrik Poinar of McMaster University, a team member.

If the microbe’s genome is so little changed, the deadliness of the Black Death may reflect the condition of its medieval victims. Harsh as the economic stresses assailing Europe today may be, they are a breeze compared with problems in the mid-14th century. The climate was cooling, heavy rains rotted out crops and caused frequent famines, and the Hundred Years’ War began in 1337. People were probably already suffering from malnutrition and other diseases when the plague arrived like the fourth horseman of the apocalypse. “People honestly thought it was the end of the world,” Ms. Bos said..."

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What’s the Most Important Lesson You Learned from a Teacher?

3:08:10 AM, Wednesday, October 12, 2011

"Five mornings a week, Keith gets up before dawn, puts on one of his geekiest bow ties (think Space Invaders, DNA helices, and daVinci’s Vitruvian Man), and drives half an hour down the freeway to teach teenagers about the wonders of science and the rigors of the scientific method at a local high school.

It’s a demanding life with little downtime. Keith’s evenings and weekends are often consumed by lesson planning and other school-related activities, but he’s perpetually stressed out about whether he’s doing enough for his kids. With his Ph.D. in chemical engineering from Berkeley — one of the top five such programs in the country — he could triple his schoolteacher’s salary by taking a job as a bench scientist at DuPont or Exxon-Mobil, as many of his fellow Berkeley grads have done.

But Keith has a passion for teaching. He lives for those moments when he can help a student make sense of the world through science. (He’s also my husband.)

People who make the career choices that Keith did don’t get a lot of respect these days. In endless discussions of “the crisis in education,” teachers are routinely described as burned out, bumbling, underqualified, and unfit — particularly if they belong to a union. In his new book Class Warfare, aspiring education reformer Steven Brill calls school districts “the most lavishly funded and entrenched bureaucracies in America… supported by an interest group — the teachers’ unions — which [have] money and playbooks every bit as effective in thwarting the public interest as Big Oil, the NRA, or Big Tobacco.”

It’s as if we’ve collectively decided that anyone who devotes his life to standing at the head of a classroom, when salaries are so low and school budgets are being slashed, can’t be that smart after all — an insidious legacy of the era when teaching was one of the few acceptable occupations for women.

Conversely, teachers who are clearly effective are portrayed as exceptional: self-sacrificing superheroes who single-handedly boost their students’ scores on standardized tests with little regard for such mundane concerns as a living wage, job security, health benefits, and adequate class resources. Meanwhile, billionaire venture capitalists like PayPal founder Peter Thiel advise young entrepreneurs to drop out of college altogether as a “bad investment” and get down to the serious business of raising capital in their teens — as if a wide-ranging education was just another expendable item on a spreadsheet.

While reading this moving NPR story about a neurosurgeon who phoned his high-school science teacher to express his gratitude after performing a tricky operation, it struck me how rarely we hear from accomplished people about the debt they owe to their teachers. The words of a true teacher stay with us a long time, offering wise counsel in a confusing world and a potent inoculation against foolishness. Yet we rarely get to thank them explicitly. Perhaps only in mid-life, we realize that the career path we chose was set, at least in part, by the recognition, praise, or clarifying criticism of a respected teacher when we were young.

In that spirit, I’ve asked some of the brightest folks I know in science and media to answer this simple question: What’s the most important lesson you learned from a teacher?

I’m delighted to report that a wide range of writers and thinkers were eager to share their stories. Among those who pay tribute to their most influential teachers here are two bestselling authors, Rebecca Skloot and Deborah Blum; the brilliant culture critic Mark Dery; award-winning science journalists David Dobbs, Amy Harmon, and Hillary Rosner; cognitive psychologist Uta Frith, the pioneer of autism research who translated Hans Asperger’s original paper; and several of the most perceptive and prolific bloggers around, including Maggie Koerth-Baker of BoingBoing, Geoff Manaugh of BLDGBLOG, and Ed Yong of Not Exactly Rocket Science. It turns out that by asking people that simple question, you open floodgates of memory and understanding.

If you feel inspired after reading these marvelous, charming, and occasionally terrifying tales from the classroom, please consider Googling up a memorable teacher and sending them an email to tell them what you’re up to now and express your appreciation. I guarantee that doing so will improve your day and profoundly touch the heart of someone who helped guide you into the world. Life is brief.

One of my favorite stories about a teacher’s enduring impact comes from Pulitzer prize-winning poet Gary Snyder, the real-life model for the hero of Jack Kerouac’s novel The Dharma Bums, and one of the first American students to study Zen in Japan. Snyder’s teacher there was a tough old monk who delivered his lengthy discourses on Buddhadharma in such a soft voice that his students strained to hear them, struggling to stay awake on their meditation cushions..."

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World's Oldest Running Car Fetches $4.6 Million at Auction

1:03:08 AM, Wednesday, October 12, 2011

"The world's oldest running car, an 1884 De Dion Bouton Et Trapardoux Dos-A-Dos Steam Runabout, made history Friday, fetching $4.62 million at RM Auctions' Hershey, Pennsylvania event. Before a packed house, the 127-year-old ride quickly eclipsed its $500,000 starting bid.

By the time the dust had settled, the gavel fell at $4.2 million. The final price included a ten-percent buyer's premium. The crowd began applauding as soon as the car crept onto the stage and the enthusiasm didn't wane until well after the sale.

The Runabout had been in the same family for 81 years prior to the sale, and is one of six De Dion tricycles known to still exist. A total of 20 of the three-wheelers were built. When new, the trike had a top speed of 38 mph and a range of 20 miles on one tank of water. The vehicle that sold last night was the only car to show up for the world's first auto race, where it averaged 16 mph over a 20-mile course. Hop the jump for a press release."

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Light-Attack Plane Seeks New Life In Navy

2:27:06 AM, Tuesday, October 11, 2011

"Lockheed Martin and Hawker-Beechcraft are considering pitching its AT-6B light-attack counterinsurgency plane for the upcoming Navy-led Combat Dragon II program, according to sources familiar with the effort.

The Navy recently shifted over $17 million into the Combat Dragon II program, designed to prove that a small, turboprop-driven aircraft can be used for "high end/special aviation" missions in Afghanistan.

The program was driven by the need coming out of from Central Command to have aircraft do close air support missions that larger fighters and bombers could not do, specifically in support of Naval Special Warfare units.

The Navy tried to fill that requirement through the Imminent Fury program, using the Brazilian-built Embraer Super Tucano. But that program fizzled out shortly before the planes headed out to Afghanistan for operational tests.

Combat Dragon II, which is set to kick off in Afghanistan by next spring, will use modified, Vietnam-era OV-10 Broncos, sources say. But the Lockheed Martin-Hawker Beechcraft team are pushing the Navy to include their plane in that mix.

While no decision has been made on whether to roll the AT-6B into Combat Dragon II, its inclusion could breath some new life into the program.

To date, the only firm commitment to buy a light-attack aircraft has come from the Afghan Ministry of Defense to support its fledgling air forces.

The Air Force was looking at the AT-6B, along with the Super Tucano, to build a fleet of aircraft specifically to train partner nations in counterinsurgency and counterterrorism operations. But to date, the Air Force has yet to formally solicit proposals from industry for that international training effort.

Moreover, Air Force leaders -- including Air Force Chief of Staff Gen. Norton Schwartz -- have said the service will never field a light-attack aircraft of its own, despite the fact the Joint Requirements Oversight Council and Joint Requirements Board validated the need for the plane, sources say.

But since the AT-6B already uses the same fire controls as the venerable A-10 Warthog, and that it can be fitted with key sensor and communication systems needed for counterinsurgency missions, makes the plane a good fit for the Navy or whoever needs a light-attack airplane, Lockheed Martin Business Development chief Bob Silva said."

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Virus Hits US Drone Fleet: Report

1:49:06 AM, Tuesday, October 11, 2011

"A computer virus has hit the US Predator and Reaper drone fleet that Washington deploys to hunt down militants, logging the keystrokes of pilots remotely flying missions, Wired magazine reported.

The virus was first detected about two weeks ago by the military's Host-Based Security System, but it had not halted missions flown remotely over Afghanistan and other warzones from Nevada's Creech Air Force Base, Wired said Friday.

No classified information was believed to have been lost or sent outside the network, though the resilient virus resisted several attempts to remove it.

"We keep wiping it off, and it keeps coming back," a source familiar with the network infection told the US magazine. "We think it's benign. But we just don't know."

Military network security specialists said it remained unclear whether the virus was intentional and how far it had spread, but they were certain it had infected Creech's classified and unclassified machines. Secret data may thus have leaked out and reached someone outside military officials.

The US military does not hide its own drone flights in Libya or the war in Afghanistan, in contrast to the CIA's covert missions to take out Al-Qaeda extremists in Pakistan, Yemen and elsewhere. The drones have become a critical weapon of choice for the United States in fighting militants abroad..."

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Huge New Dinosaur Trackway Found in U.S.

11:49:03 PM, Monday, October 10, 2011

"Fossilized tracks of dinosaurs "stomping in the mud" have been discovered in southwestern Arkansas, scientists say.

Spanning the length of two football fields, the footprints hint that a giant predator was a bit pigeon-toed.

Several species, including the eight-ton Acrocanthosaurus atokensis—one of the largest predators ever to walk Earth—and sauropods, or long-necked plant-eaters, left their footprints in the 120-million-year-old Cretaceous limestone.

At the time, Arkansas was a broad mud flat, similar to the hot, dry, and salty shores of the modern-day Persian Gulf—not a particularly "pleasant place," said team leader Stephen Boss, a geoscientist at the University of Arkansas in Fayetteville.

Predators like Acrocanthosaurus were likely attracted to the site by sauropods and other prey species, but "what the sauropods are doing out there, who knows?" Boss said.

Though found elsewhere in North America, dinosaur trackways are rare in the southern U.S., he said. Indeed, most people tend to think of dinosaurs dwelling in the "classic" western lands of Colorado and Utah.

"They don't think this is a place that dinosaurs once roamed, but it is—and here's the proof."

Dinosaur Tracks Reveal Pigeon-Toed Predator?

A private citizen recently found the tracks, which were possibly exposed after a rainstorm scoured away a thin layer of shale. The shape of the footprints and the age of the limestone leaves "no doubt" that they were left by dinosaurs, said Boss, whose new research has not yet been published.

"The photographs seem to make it clear that they are indeed theropod dinosaur tracks," vertebrate paleontologist Thomas R. Holtz, Jr. said via email. Theropods, which included T. rex, were two-legged predators.

"Acrocanthosaurus tracks are already well known from Texas, and we have fossils of Acrocanthosaurus and closely related forms from Texas, Oklahoma, and Maryland, so almost certainly it lived in Arkansas, too," added Holtz, of the University of Maryland.

The tracks were likely left by multiple dinosaurs and must have been filled in fairly quickly—if they'd been exposed for long, the prints would have eroded beyond recognition, team member Boss said.

Set Lasers to "Discover"

Boss and colleagues scanned the trackway with a laser at a high resolution. The scan digitally preserved the tracks so that the scientists could analyze them and "walk across that surface in cyberspace," he said..."

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Double Impact: Did 2 Giant Collisions Turn Uranus on Its Side?

11:38:05 PM, Monday, October 10, 2011

"Knock, knock. That's not the start of a joke but the hard-luck history of Uranus. New research suggests that the giant planet may have suffered two massive impacts early in its history, which would account for its extreme, mysterious axial tilt.

Uranus orbits nearly on its side; its axis of rotation is skewed by 98 degrees relative to an ordinary upright orientation, perpendicular to the orbital plane. Many planetary scientists have sought to explain the odd tilt by invoking a giant impact into Uranus billions of years ago. But the giant planet has a system of moons circling its equator that would have been disrupted by such an impact.

"If Uranus is suddenly tilted, the satellites keep moving like that from north pole to south pole, and [wouldn't be] equatorial at all," Alessandro Morbidelli of the Observatory of Côte d’Azur in Nice, France, reported here Thursday at a joint meeting of the American Astronomical Society Division for Planetary Sciences and the European Planetary Science Congress.

But what if the tilting was a more gradual process, caused not by one mammoth impact but by two somewhat smaller nudges? Simulations show that the two-strike mechanism appears to solve the problem, knocking Uranus sideways and allowing it to develop equatorially orbiting moons, Morbidelli said.

The key is that the impacts must have come very early, before Uranus's moons had coalesced from a disk of gas and dust surrounding the planet. That disk, supplemented by debris stirred up by the collisions, would have migrated around the planet to form a thin equatorial disk that gave rise to Uranus's five large moons.

In the simulations, the same sort of equatorial migration also worked for the single-impact tilt scenario, but that scenario came with one important and disqualifying caveat: the moons orbited in the wrong direction, counter to Uranus's rotation. "If you tilt Uranus all in one shot, you produce regular satellites on the equator, but they will all be retrograde, and the satellites are actually prograde," Morbidelli said..."

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