Ruwenzori: July 2010

Thursday 15 July 2010

Johnald's Fantastical Daily Link Splurge

Happiness and Sadness Spread Just Like Disease
Poop Study: People Have Friendly Gut Viruses
Apes, Old World Monkeys May Have Split Later Than Thought
Our Eavesdropping-on-ET Strategy Not Likely to Work

Happiness and Sadness Spread Just Like Disease

Posted: 14 Jul 2010 02:17 PM PDT

There may be a literal truth underlying the common-sense intuition that happiness and sadness are contagious.

A new study on the spread of emotions through social networks shows that these feelings circulate in patterns analogous to what's seen from epidemiological models of disease.

Earlier studies raised the possibility, but had not mapped social networks against actual disease models.

"This is the first time this contagion has been measured in the way we think about traditional infectious disease," said biophysicist Alison Hill of Harvard University.

Data in the research, in the July 7 Proceedings of the Royal Society, comes from the Framingham Heart Study, a one-of-a-kind project which since 1948 has regularly collected social and medical information from thousands of people in Framingham, Massachusetts.

Earlier analyses found that a variety of habits and feelings, including obesity, loneliness, smoking and happiness appear to be contagious.

In the current study, Hill's team compared patterns of relationships and emotions measured in the study to those generated by a model designed to track SARS, foot-and-mouth disease and other traditional contagions. They discounted spontaneous or immediately shared emotion — friends or relatives undergoing a common experience — and focused on emotional changes that followed changes in others.

In the spread of happiness, the researchers found clusters of "infected" and "uninfected" people, a pattern considered a "hallmark of the infectious process," said Hill. "For happiness, clustering is what you expect from contagion rates. Whereas for sadness, the clusters were much larger than we'd expect. Something else is going on."

Happiness proved less social than sadness. Each happy friend increased an individual's chances of personal happiness by 11 percent, while just one sad friend was needed to double an individual's chance of becoming unhappy.

Patterns fit disease models in another way. "The more friends with flu that you have, the more likely you are to get it. But once you have the flu, how long it takes you to get better doesn't depend on your contacts. The same thing is true of happiness and sadness," said David Rand, an evolutionary dynamics researcher at Harvard. "It fits with the infectious disease framework."

The findings still aren't conclusive proof of contagion, but they provide parameters of transmission rates and network dynamics that will guide predictions tested against future Framingham results, said Hill and Rand. And whereas the Framingham study wasn't originally designed with emotional information in mind, future studies tailored to test network contagion should provide more sophisticated information.

Both Hill and Rand warned that the findings illustrate broad, possible dynamics, and are not intended to guide personal decisions, such as withdrawing from friends who are having a hard time.

"The better solution is to make your sad friends happy," said Rand.

Image: Morgan/Flickr.

See Also:

Citation: "Emotions as infectious diseases in a large social network: the SISa model." By Alison L. Hill, David G. Rand, Martin A. Nowak and Nicholas A. Christakis. Proceedings for the Royal Society B, Published online before print, July 7, 2010.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.

Poop Study: People Have Friendly Gut Viruses

Posted: 14 Jul 2010 11:42 AM PDT

It's not just the bugs in our guts that are surprisingly friendly. It's our viruses, too.

After slowly coming to appreciate the importance of symbiotic bacteria for running our bodies, scientists have wondered whether viruses also help. Now a gene-hunting expedition in the gut has found it teeming with highly personalized viral communities.

"Viral diversity and life cycles are poorly understood in the human gut and other body habitats," wrote researchers led by Washington University microbiologist Jeffrey Gordon in a study in the July 14 Nature. Unlike gut bacteria, these viruses — our "virome" — appear uniquely individual, differing even between identical twins.

The study is a natural extension of research on internal bacteria, which outnumber each body's human cells by a factor of 10. Collectively called the microbiome, they perform digestive and metabolic tasks our bodies can't accomplish unaided. In a way, the microbiome is as much a part of us as any organ. It just happens to come from another order of life.

Gordon's lab, which specializes in the links between gut bacteria and obesity, has been at the forefront of microbiome research. That's led them to question whether, just as scientists once failed to appreciated the importance of bacteria, they've overlooked viruses.

"The idea was that having a virus, under any circumstance, is basically bad. Sometimes it causes disease, sometimes not, but having viruses present is abnormal," said Andrew Gewirtz, an Emory University microbiologist not involved in the study. "As the complexity of the microbiota became appreciated, people have wondered whether that is really true, or if there's a normal population of viruses. This is the first paper to look in a systematic way."

Because intestinal tracts are difficult to study directly, Gordon's team sampled DNA from the stool samples of four identical-twin pairs and their mothers. They identified which sequences came from bacteria, and which from viruses.

Unlike stomach bacteria, which are relatively consistent between siblings, viral profiles varied markedly. The pattern's significance isn't yet evident, but it's striking.

Samples taken at later dates showed that viral communities were stable, rather than fluctuating as would be expected if competing with bacteria. Virome and microbiome coexist peacefully, and may even cooperate.

More than 4,000 different viral strains were ultimately identified, 80 percent of which hadn't been seen before. Despite the novelty, the researchers could match individual genes to known functions. This doesn't show the targets of those functions, but it's possible that "viral genes are just providing that little something that bacteria don't have," said Gewirtz.

Gordon's team next intends to see what happens when human virome samples are added to mice engineered to contain human microbiomes. Other scientists will further explore the virome's role.

"Human microbiome projects have been initiated throughout the world," wrote Gordon's team. "Our results indicate that these metagenomic studies should also include" the virome.

Images: Left: the human colon against a background of virus-like particles. Right: functional associations of genes from friendly stomach viruses and bacteria./Alejandro Reyes, Vamsi Narra, Laura Kyro, and Jeffrey Gordon.

See Also:

Citation: "Viruses in the faecal microbiota of monozygotic twins and their mother." Reyes A, Haynes M, Hanson N, Angly FE, Health AC, Rohwer F and Gordon JI. Nature, Vol. 466 No. 7304, July 15, 2010.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.

Apes, Old World Monkeys May Have Split Later Than Thought

Posted: 14 Jul 2010 11:30 AM PDT

A slope-faced, big-toothed creature from the distant past has inspired scientists to recalibrate the ancient evolutionary split between apes and Old World monkeys.

Discoverers of a partial apelike skull in western Saudi Arabia say that it now appears that a poorly understood parting of major primate groups occurred between 29 million and 24 million years ago. A 2004 analysis of DNA from living apes and monkeys in Africa and Asia had estimated an earlier divergence, between 34.5 and 29.2 million years ago.

An intriguing mosaic of features on the newly unearthed fossil, which dates to between 29 million and 28 million years ago, suggests that it lived shortly before a common ancestor that gave rise to hominoids — a primate lineage that includes apes and humans — and the monkeys of Africa, Asia and Europe. A team led by anthropology graduate student Iyad Zalmout of the University of Michigan in Ann Arbor reports the find in the July 15 Nature.

Zalmout and his colleagues assign the skull to a new primate genus and species, Saadanius hijazensis.

"This is wonderful discovery, a real missing link that fills in a gap in our understanding of the timing and pattern of anatomical change involved in the evolution of Old World monkeys and apes," remarks anthropologist John Fleagle of Stony Brook University in New York.

Zalmout, working with members of the Saudi Geological Survey in Jeddah, found the partial Saadanius skull on Feb. 17, 2009, in a section of Saudi Arabia's Shumaysi Formation framed by previously dated volcanic ash layers. Based on the specimen's size and shape, the researchers estimate that Saadanius weighed 15 to 20 kilograms (33 to 44 pounds), making it a medium-sized primate for its time.

Saadanius sports a projecting snout, a relatively tall face with long, narrow nasal bones, broad cheek teeth and other traits resembling those of older primates previously unearthed at a geological formation on the edge of Egypt's Sahara Desert. Researchers estimate that those creatures lived between 35 million and 30 million years ago.

But a few critical anatomical features, including a long, tube-shaped ear canal, distinguish Saadanius from its primate predecessors, the scientists say. And unlike Old World monkeys and hominoids that evolved after about 24 million years ago, Saadanius — which Zalmout's group identifies as a male based on dental characteristics — lacked nasal sinuses and large canine teeth typical of later ape and monkey males.

For that reason, the researchers use 24 million years as the most recent estimate of when Old World monkeys diverged from apes.

Anthropologist Brenda Benefit of New Mexico State University in Las Cruces proposed in 1993 that a common ancestor of Old World monkeys and apes, or its close relative, would look much like the new fossil find. "Saadanius strikingly matches her prediction," says Michigan's William Sanders, a co-author of the new study.

Saadanius apparently lived not long before Old World monkeys and apes diverged from a common ancestor, Fleagle says. Unfortunately, a 5-million-to-10-million-year gap separates Saadanius from the earliest known Old World monkeys and hominoids, so key pieces of the evolutionary transition are still missing.

That makes it difficult to narrow down the timing of an ape–Old World monkey divergence, says anthropologist Elwyn Simons of Duke University in Durham, North Carolina. But the new fossil "fits in exactly as it should" in primate evolution, he holds.

Although additional fossil finds are needed, the Saudi specimen offers a more reliable age estimate for a crucial shift in primate evolution than can be gleaned from DNA studies of living apes and monkeys, comments anthropologist David Begun of the University of Toronto.

Image: Partial cranium of the discovered Saadanius specimen./Zalmout and Sanders.

Posted: 14 Jul 2010 09:01 AM PDT

Bad news for SETI: Even with the most sensitive radio telescopes yet designed, humans probably won't find intelligent aliens by listening in on their phones and televisions, a new study finds.

"Eavesdropping on ET is very hard, even with the latest radio telescopes," said astronomer Duncan Forgan of the University of Edinburgh, a coauthor of the study. "If we don't try any other ways of searching for aliens, then we may never find them."

Forgan and astronomer Robert Nichol of the Institute of Cosmology and Gravitation in the U.K. set out to test the suggestion that rather than building expensive telescopes dedicated exclusively to listening for signals from aliens, SETI — the search for extra-terrestrial intelligence — could be done on the cheap by piggy-backing on other astronomy missions.

Some astronomers hoped SETI searches could ride on the coattails of the planned Square Kilometer Array, which will probe the history of the universe with thousands of small antennas spread out either Australia or South Africa.

"We focused on the SKA because it will be an incredible advancement in radio astronomy," Forgan said. "It will be the most powerful radio telescope ever built."

The SKA will also be sensitive in the same frequency range that cellphones, radio and television operate in. If the aliens out there are anything like us, that frequency range is exactly where we should expect to find them, astronomers have suggested.

In 2007, astrophysicists Abraham Loeb and Matias Zaldarriaga of the Harvard-Smithsonian Center for Astrophysics calculated that signals similar to those used in human military radar could be detected from more than 160 light-years away using a telescope in the Netherlands called LOFAR, and more than 650 light-years away using the SKA.

But assuming these aliens have technology like ours, there won't be enough time to find them, Forgan and Nichol argue. Humans, the only intelligent civilization we know of, have been communicating using radio waves for only about 100 years — and we're beginning to go quiet. Advances in technology mean less power is needed to broadcast, and digital communication is starting to replace radio altogether.

Forgan and Nichol randomly generated about 500,000 alien civilizations based on current theories of planet formation, and an optimistic guess as to how many would develop life. They then assumed that each civilization broadcasts in radio for 100 years, and they can hear each other from up to 300 light-years away.

"All communication disappears," the team wrote. Even with a telescope like the SKA, the odds of eavesdropping on another civilization are one in 10 million. The results were posted in a paper on the astronomy preprint website arxiv.org and accepted for publication in the International Journal of Astrobiology.

A more fruitful strategy would be to target our searches, Forgan suggests. We may not be able to hear leaked signals, but we could still pick up a deliberate beacon from a civilization that wanted to announce its presence. A telescope dedicated to searching for such a beacon, like the Allen Telescope Array in northern California, would improve the odds to one in 10 thousand.

Jill Tarter of the SETI Institute thinks Forgan underestimates the usefulness of the SKA. "The SKA is being built with a large field of view and many simultaneous beams, so that there should in fact be significant observing time available for SETI," she said.

Whatever the odds, Loeb thinks we should eavesdrop, anyway. "Rather than speculate about how generic is our own evolution and whether others will be the same, we should just search," he said. He points out that a lot of technological advances are driven by social forces. For example, Earth gave off the most radio waves during the Cold War, when radar ballistic missile searches were common.

"Politics are impossible to predict, they don't follow laws of physics," he said. "We should just explore the sky, and try to set as strong limits as we can."

Forgan agrees. "We should always continue to eavesdrop as it is a cheap search method, especially if we piggy-back," he said. "If you don't listen, you won't hear anything."

Image: SKA

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Wednesday 14 July 2010

Johnald's Fantastical Daily Link Splurge

Frogs Jump Farther When Competing at County Fair
Salmon Killer Disease Mystery Solved
Death Star Off the Hook for Mass Extinctions
Hubble Captures Cosmic Cauldron
Human Evolution Recapped in Kids’ Brain Growth
Terahertz Detectors Could See Through Your Clothes From a Mile Away
Rosetta’s Closest Asteroid Flyby Photos
Earth From Space: Greenland Glacier Shrinks Overnight
Dark Matter May Be Building Up Inside the Sun
Turbulence Discovery Could Lead to Better Planes

Frogs Jump Farther When Competing at County Fair

Posted: 13 Jul 2010 03:00 PM PDT

PROVIDENCE, Rhode Island — Rumors of the great jumping frogs of Calaveras County have not been greatly exaggerated.

The longest jump reported in scientific papers for an American bullfrog is almost 4.3 feet, says Henry Astley of Brown University in Providence, Rhode Island. Yet, new measurements have added almost three feet to that record by using California's Calaveras County Fair as a testing ground for determining maximal species performance. Inspired by a Mark Twain story from 1865, the fair has for 83 years featured a highly competitive jumping-frog contest.

To find out how far frogs can leap in a single bound, researchers had to measure for themselves, because the contest is based on the total distance covered in three jumps.

Contest officials don't permit scientists to set up equipment in the jumping arena, Astley says. Preserving optimal jump conditions, comparable year-to-year, is a big deal in Calaveras County. Contestants raise intense disputes over matters such as whether a fairgoer heading toward a popcorn stand has distracted a frog at a critical second.

Astley and his colleagues measured jump distance using computer analysis of video from a camera carefully positioned in the viewing area. More than half the 3,449 frog jumps researchers recorded in the 2009 contest beat the record from the scientific literature, Astley reported July 10 at the 2010 Joint Meeting of Ichthyologists and Herpetologists.

Judges at the 2009 contest declared the winning three-jump distance to be 21 feet even, as measured from the starting plate to the point where the frog finally plopped. The Brown team, however, recorded a different frog as covering the most ground on a single jump, a leap of 7.2 feet.

Such great leaps raise issues of biomechanics, Astley said. Calaveras frogs appear to be jumping farther than possible for the calculated power of bullfrog muscles. Astley speculated that the frogs amplify their power by using their leg tendons as a spring, stretching the tendons and letting them snap back all at once.

Most frog jockeys, as human contestants are known, compete using the American bullfrog (Rana catesbeiana), a large, voracious species that has invaded the West Coast from the eastern United States. Jockeys can touch their frogs only at the beginning of the first jump. Afterward, they rely on shouting, blowing or crouching behind the frog and doing their own startling leaps to urge the frogs on.

Anyone can rent a frog at the fair to enter the contest. But many serious competitors bring their own, inspiring rumors about secret locations in the wild for catching a top jumper.

Jockey expertise in locating a top frog and inspiring it matters to performance, according to Astley's data. Jump lengths of rental frogs showed a roughly bell-shaped distribution. In contrast, non-rental frogs showed a distribution lopsided toward the high end of jump length.

By now the Calaveras frogs may indeed be reaching the outer limits of what bulllfrog species can do, Astley said. Winning jumps tended to lengthen during early decades of the contest but haven't improved a lot since the 1980s.

"Were the pro frogs tested for steroids?" herpetologist Matt Hinderliter of The Nature Conservancy in Camp Shelby, Mississippi, asked Astley at the meeting.

No, but a frog-doping scandal would hardly explain all the study results, such as how so many of the rental frogs beat the old "maximum" distance for a jump, Astley said. Analyses of the spread of jump distances recorded at the fair, he said, suggest that scientists need to test hundreds of animals to see anything close to a species' real maximum performance. And judging by the antics of hard-core frog jockeys, the animal's motivation matters too.

Image: Flikr/unclebumpy

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Salmon Killer Disease Mystery Solved

Posted: 13 Jul 2010 09:38 AM PDT

The identity of a mysterious disease that's raged through European salmon farms, wasting the hearts and muscles of infected fish, has been revealed.

Genome sleuthing shows the disease is caused by a previously unknown virus. The identification doesn't suggest an obvious cure — for now, scientists have only a name and a genome — but it's an important first step.

"It's a new virus. And with this information now in hand, we can make vaccines," said Ian Lipkin, director of Columbia University's Center for Infection and Immunity, a World Health Organization-sponsored disease detective lab.

Two years ago, Norweigan fisheries scientists approached Lipkin and asked for help in identifying the cause of Heart and Skeletal Muscle Inflammation, or HSMI, the official name for a disease first identified in 1999 on a Norweigan salmon farm.

Infected fish are physically stunted, and their muscles are so weakened that they have trouble swimming or even pumping blood. The disease is often fatal, and the original outbreak has been followed by 417 others in Norway and the United Kingdom. Every year there's more of the disease, and it's now been seen in wild fish, suggesting that farm escapees are infecting already-dwindling wild stocks.

Lipkin's team — which has also identified mystery viruses killing Great Apes in the Ivory Coast, and sea lions off the U.S. West Coast — combed through genetic material sampled from infection salmon pens, looking for DNA sequences resembling what's seen in other viruses, and inferring from those what the HSMI-causing sequence should look like. Lipkin likened the process to solving a crossword puzzle. The researchers eventually arrived at the 10-gene virus they called piscine reovirus, or PRV. The virus was described July 9 in Public Library of Science One.

Related reoviruses have been found on poultry farms and cause muscle and heart disease in chickens. "Analogies between commercial poultry production and Atlantic salmon aquaculture may be informative," wrote the researchers. "Both poultry production and aquaculture confine animals at high density in conditions that are conducive to transmission of infectious agents."

Such findings may be useful as the Obama administration develops a national policy for regulating aquaculture.

"If the potential hosts are in close proximity, it goes through them like wildfire," said Lipkin.

Image: A healthy salmon, above; a salmon with HSMI, below./T. Poppe.

See Also:

Citation: "Heart and Skeletal Muscle Inflammation of Farmed Salmon Is Associated with Infection with a Novel Reovirus." By Gustavo Palacios, Marie Lovoll, Torstein Tengs, Mady Hornig, Stephen Hutchison, Jeffrey Hui, Ruth-Torill Kongtorp, Nazir Savji, Ana V. Bussetti, Alexander Solovyov, Anja B. Kristoffersen, Christopher Celone, Craig Street, Vladimir Trifonov, David L. Hirschberg, Raul Rabadan, Michael Egholm, Espen Rimstad, W. Ian Lipkin. PLoS ONE, Vol. 5 No. 7, July 9, 2010.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.

Death Star Off the Hook for Mass Extinctions

Posted: 13 Jul 2010 04:30 AM PDT

A massive extinction like the one that claimed the dinosaurs has hit the Earth like clockwork every 27 million years, a new fossil analysis confirms. But the study claims to rule out one controversial explanation: a dark stellar companion called Nemesis that sends a regular rain of deadly comets toward Earth.

"The main astronomical ideas you can come up with that could cause something like this just don't work," said physicist Adrian Melott of the University of Kansas, a co-author of the new study.

Nemesis was first suggested in 1984 as a way to explain an alarmingly regular series of extinctions in the marine fossil record, which was discovered by paleontologists David Raup and Jack Sepkoski. In light of the suggestion in 1980 that the dinosaurs were killed by a catastrophic impact, an invisible cosmic sniper lobbing comets at the inner solar system seemed like a plausible culprit.

Two independent groups of astronomers suggested that a dim brown dwarf or red dwarf star lying between one and two light-years from the sun could throw a shower of ice and rock from the Oort Cloud every 26 million or 27 million years to wreak havoc on Earth. Because the orbit of this "death star" would be tweaked by interactions with other stars and the Milky Way, the time between one impact and the next should vary by 15 to 30 percent.

But now, Melott and co-author Richard Bambach of the National Museum of Natural History in Washington, D.C., say that's not actually what happens. The extinctions come almost exactly every 27 million years, they say, to a confidence interval of 99 percent.

"It's really too good, it's too sharp and fixed," Melott said. "It's like a clock."

Melott and Bambach compared two huge data sets going back 500 million years, twice as far as the 1984 study looked. One dataset, the Sepkoski database, is a continuation of the original study. The other, the Paleobiology Database, was compiled between 2000 and 2008. Both sets include many fossils that have been found and cataloged since 1984.

The researchers searched mathematically for patterns that were common to both datasets, and found that both showed an excess of organisms disappearing every 27 million years, too regularly to be caused by a shiftable star.

"It was a slam dunk on finding exactly what you would expect to find if they [Raup and Sepkoski] were right, which surprised me," Melott said. "We have strong confirmation of this periodicity, it's exactly the same one that those guys found in '84, and we have no clue what's causing it."

Other astronomers think Nemesis is still out there, however. Richard A. Muller of the University of California at Berkeley, one of the authors of the 1984 paper proposing the dark star and the author of a popular book called Nemesis: The Death Star, thinks Melott is "coming to too strong a conclusion."

"I would agree with most of what he says, but I think he is overestimating the accuracy of the geologic timescale," he said. The geological record gives only an approximate sense of when major extinctions happened. "You get them in the right order, but it's really difficult to get an actual date," he said. In light of that uncertainty, "I would say the Nemesis hypothesis is still alive."

There is a way to check. Several ongoing astronomical survey telescopes, including NASA's Wide-Field Infrared Survey Explorer, the Large Synoptic Survey Telescope and the Pan-STARRS survey, are scanning the sky with enough sensitivity to find Nemesis if it exists. If they don't find the dark star, then it probably isn't there.

"That's the ultimate test," Muller said.

Image: Dallas1200am/Flickr

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Hubble Captures Cosmic Cauldron

Posted: 13 Jul 2010 03:00 AM PDT

The churning clouds of dust and gas in this colorful new Hubble image of star-forming region NGC 2467 speak to the violent, tumultuous youthfulness of the region's stars. The hot infant stars that were brewed in the cloud are emitting fierce ultraviolet radiation, sculpting and eroding the surrounding gas and making it glow in visible wavelengths.

Most of the radiation comes from the single hot, massive star just above the center of the image. Its radiation has pushed aside so much of the gas that a new generation of stars has started forming in the denser regions around the edge. Many more young stars inhabit this region than are visible in this image, but they are hidden by gas and dust.

NGC 2467 lies in the southern constellation Puppis, the Latin name for the poop deck of a ship. It is part of a larger constellation representing the Argo, Jason's ship in Greek mythology. NGC 2467 is thought to lie about 13,000 light-years from Earth.

The picture was created from images taken with the Advanced Camera for Surveys through three different filters, shown in blue, green and red. The data were taken in 2004.

Higher-resolution versions are available.

Image: NASA, ESA and Orsola De Marco (Macquarie University)

Posted: 12 Jul 2010 02:05 PM PDT

For a quick summary of the last 25 million years in human brain evolution, just watch how our brains change between infancy and adulthood.

Over its first few decades, the human cerebral cortex — the brain's wrinkled outer tissue — evolves in ways that parallel its evolution since we last shared a common ancestor with macaque monkeys.

It's not an absolute one-to-one correlation, but the overlap is so striking that it's hard to ignore, said neurobiologist David Van Essen of Washington University in St. Louis.

In a study published July 12 in the Proceedings of the National Academy of Sciences, Van Essen's team compared brain scans of infant and adult humans. The resulting differences were then mapped against a comparison of cortex shape differences in adult humans and macaques, with whom our species last shared a common ancestor 25 million years ago.

Since then, the human brain has gone into overdrive, becoming extraordinary large and complex. Not all changes involve size and shape — we've also got new gene networks operating in novel ways — but they're certainly part of the human equation. And at infancy, the brain that will someday be big is small and relatively unformed.

According to Van Essen, this pattern of brain development may represent a virtue made from evolutionary necessity.

In the new study, the areas that change least — between baby and adult, human and macaque — are those related to core senses like vision, which are ostensibly necessary right from birth. If other, less immediately important faculties were also mature, babies' heads might be so large as to cause difficulties during pregnancy.

This in turn allows undeveloped brain regions to "benefit from the experiences of childhood," said Van Essen. Extra-large helpings of social and cultural knowledge customize the infant brain, making both babies and the species more adaptable and allowing for complex social institutions to develop.

"Childhood is an extended period for humans, compared to other primates," said Van Essen. "We learn an enormous amount, but it takes us a very long time to do it.

Image: Top row, a comparative map of cortical differences between the average adult macaque and human; middle row, a comparison between the infant and adult human brain; bottom, a comparison of human developmental and evolutionary changes./PNAS.

See Also:

Citation: "Similar patterns of cortical expansion during human development and evolution." By Jason Hill, Terrie Inder, Jeffrey Neil, Donna Dierker, John Harwell, David Van Essen. Proceedings of the National Academy of Sciences, Vol. 107. No. 28, July 13, 2010.

Brandon Keim's Twitter stream and reportorial outtakes; Wired Science on Twitter. Brandon is currently working on a book about ecological tipping points.

Terahertz Detectors Could See Through Your Clothes From a Mile Away

Posted: 12 Jul 2010 12:16 PM PDT

Someone may soon be able to tell what types material are in your pockets from tens, and possibly thousands, of feet away.

Using terahertz remote sensing, detectors could see through walls, clothing and packaging materials and immediately identify the unique terahertz waves of the materials contained inside, such as explosives or drugs.

Until now, detecting terahertz waves — the portion of the electromagnetic spectrum between infrared and microwave light — hasn't been possible from distances more than inches because the waves are absorbed by ambient moisture in the air, killing the signal.

"A lot of other researchers thought that terahertz remote sensing was mission impossible," said physicist Jingle Liu of Rensselaer Polytechnic Institute, lead author of the study published July 11 in Nature Photonics.

Liu's team solved the problem by not relying on the terahertz waves themselves to generate or carry the signal back to the detector. Instead, they used the reflection created by lasers pointed at the target.

Terahertz range of the electromagnetic spectrum

Two lasers at different frequencies aimed at the target together generate a plasma (basically excited, or ionized air). This plasma emits a florescence that is scattered in characteristic ways by the terahertz radiation of the material it hits. The reflection of the florescence is detectable from remote distances

The researchers have tested hundreds of different substances and created a library of terahertz spectra to compare to the signal from the target and instantly identify the material that was hit.

The researchers demonstrated that they could detect the signal from 67 feet away, the length of their laboratory space, but theoretically they could identify materials hundreds of feet or even miles away, Liu said.

"Homeland security and military agencies have been struggling for years to get technology like this," said terahertz expert Abul Azad at Los Alamos National Laboratory. "I think the approach they have revealed is really, really unique."

The first application of this technology will likely be for the remote detection of roadside bombs, also known as improvised explosive devices (IEDs) by the military. Homeland Security and the Defense Department were the primary funders of the research.

Terahertz detectors could also be used for airport security to detect illegal substances hidden in people's clothes. The approach would be less invasive than x-rays, Liu said, because terahertz waves are much lower in energy. It would not reveal anything concealed inside the body, because the terahertz signals cannot go through water, or metal.

Theoretically, Liu said, terahertz remote sensing could also be used identify the composition of an unknown toxic spill in the environment, or the composition of objects in space.

Image: 1) Schematic of the terahertz wave remote sensing technique/Zhang. 2) Wikipedia/Tatoute.

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Rosetta’s Closest Asteroid Flyby Photos

Posted: 10 Jul 2010 03:27 PM PDT

<< previous image | next image >>

The Rosetta spacecraft took its first close-up images of the asteroid Lutetia today, revealing it to be a heavily cratered, elongated rock.

Rosetta got within 2,000 miles of the asteroid, which is about 80 miles long and 4.5 billion years old. The closest images got down to less than 200 feet in resolution.

The spacecraft was traveling at around 9 miles per second, and the whole flyby took less than a minute. The European Space Agency mission is now focused on its primary target, comet Churyumov-Gerasimenko. Rosetta should arrive at the comet in 2014 and hang out with it for a few months and send a lander to the comet nucleus.

Image: ESA 2010 MPS for OSIRIS Team MPS/UPD/LAM/IAA/RSSD/INTA/UPM/DASP/IDA

Earth From Space: Greenland Glacier Shrinks Overnight

Posted: 10 Jul 2010 01:12 PM PDT

A 2.7-square-mile chunk of Greenland's Jakobshavn Isbrae glacier, one-eighth the size of New York's Manhattan Island, broke off into the ocean between July 6 and 7.

The sudden mile-long retreat of the glacier, caught in the image above by DigitalGlobe's WorldView 2 satellite, moved the point where the ice meets the ocean further back than it has ever been seen. This kind of calving event isn't that unusual, but seeing it hours after it happened in this much detail is rare. And the event is somewhat unexpected this year.

"While there have been ice breakouts of this magnitude from Jakobshavn and other glaciers in the past, this event is unusual because it occurs on the heels of a warm winter that saw no sea ice form in the surrounding bay," said cryospheric program scientist Thomas Wagner in a press release July 9.

"While the exact relationship between these events is being determined, it lends credence to the theory that warming of the oceans is responsible for the ice loss observed throughout Greenland and Antarctica," Wagner said.

The Jakobshavn Isbrae glacier has retreated more than 27 miles since 1850, and six of those miles were lost since 2000. Scientists estimate that up to 10 percent of Greenland's ice that is currently being lost is coming from this glacier, making it the largest single cause of rising sea level in the northern hemisphere.

Image: Jakobshavn Isbrae glacier on July 6 (left) and July 7 (right) DigitalGlobe.

Posted: 09 Jul 2010 10:48 AM PDT

The sun could be a net for dark matter, a new study suggests. If dark matter happens to take a certain specific form, it could build up in our nearest star and alter how heat moves inside it in a way that would be observable from Earth.

Dark matter is the mysterious stuff that makes up about 83 percent of the matter in the universe, but doesn't interact with electromagnetic forces. Although the universe contains five times as much dark matter as normal matter, dark matter is completely invisible both to human eyes and every kind of telescope ever devised. Physicists only know it's there because of its gravitational effect on normal matter. Dark matter keeps galaxies spinning quickly without flying apart and is responsible for much of the large-scale structure in the universe.

Current dark matter detectors are looking for WIMPs, or weakly interacting massive particles, that connect only with the weak nuclear force and gravity. Based on the most widely accepted theories, most experiments are tuned to look for a particle that is about 100 times more massive than a proton. The chief suspect is also its own antiparticle: Whenever a WIMP meets another WIMP, they annihilate each other.

"This is something that has always worried me," said astroparticle physicist Subir Sarkar of the University of Oxford. If equal amounts of matter and antimatter were created in the big bang, the particles should have completely wiped each other out by now. "Obviously that did not happen, we are here to prove it," he said. "So something created an asymmetry of matter over antimatter," letting a little bit of matter survive after all the antimatter was gone.

Whatever made regular matter beat out regular antimatter could have worked on dark matter as well, Sarkar suggests. If dark matter evolved similarly to regular matter, it would have to be much lighter than current experiments expect, only about 5 times the mass of a proton. That's a suggestive number, Sarkar says.

"If it were five times heavier, it would get five times the abundance. That's what dark matter is," he said. "That's the simplest explanation for dark matter in my view."

The trouble is, these light particles are much more difficult to detect with current experiments. In a paper in the July 2 Physical Review Letters, Sarkar and Oxford colleague Mads Frandsen suggest another way to find light dark matter: Look to the sun.

Because lightweight dark matter particles wouldn't vaporize each other when they meet, the sun should collect the particles the way snowballs collect more snow.

"The sun has been whizzing around the galaxy for 5 billion years, sweeping up all the dark matter as it goes," Sarkar said.

The buildup of dark matter could solve a pressing problem in solar physics, called the solar composition problem. Sensitive observations of waves on the sun's surface have revealed that the sun has a much easier time transporting heat from its interior to its surface than standard models predict it should.

Dark matter particles that interact only with each other could make up the difference. Photons and particles of regular matter bounce off each other on their way from the sun's interior to its surface, so light and heat can take billions of years to escape. But because dark matter particles ignore all the regular matter inside the sun, they have less stuff in their way and can transport heat more efficiently.

"When we do the calculation, to our amazement, it turns out this is true," Sarkar said. "They can transport enough heat to solve the solar composition problem."

Next, Sarkar and Frandsen calculated how being full of dark matter would affect the number of neutrinos the sun gives off. They found that the neutrino flux would change by a few percent. That's not much, Sarkar said, but it's just enough to be detected by two different neutrino experiments — one in Italy called Borexino and one in Canada called SNO+ — that are soon to get under way.

"It's a speculative idea, but it's testable," Sarkar said. "And the tools to test it are coming on line pretty fast. We don't have to wait 20 years."

The idea of lightweight dark matter influencing the sun is "not too much of a stretch, in my opinion," said physicist Dan Hooper of Fermilab in Illinois. "I look at their numbers, and they're very plausible to me."

Some puzzling results from dark matter detectors hint that these lightweight particles could have already been detected. Earlier this year, a germanium hockey puck in a mine in Minnesota called the Coherent Germanium Neutrino Technology (CoGeNT) detected a signal from a particle about 7 times the mass of the proton, though they're not sure yet whether it's dark matter. Another detector in Italy called DAMA has reported similar results.

"There's an increasingly compelling body of evidence accumulating" that dark matter is just a few times as massive as a proton, Hooper said. "The jury is still out, but if this is really what's going on, we should be able to know it with some confidence in the next year or so."

Update: Regular matter makes up 5 percent of the energy density of the universe, and dark matter makes up 25 percent (five times more than regular matter). The remaining 70 percent is dark energy.

Image: NASA/Solar Dynamics Observatory

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Turbulence Discovery Could Lead to Better Planes

Posted: 09 Jul 2010 09:51 AM PDT

With just a single measurement, a new model may deftly describe turbulent fluid flows near an airplane wing, ship hull or cloud, researchers report in the July 9 Science. If the long-sought model proves successful, it may lead to more efficient airplanes, better ways to curb pollution dispersal and more accurate weather forecasts.

Fluid dynamicist Alexander Smits of Princeton University calls the new model "a very significant advance" that opens up a new way of thinking about chaotic, energy-sapping turbulence.

Turbulence is a problem that extends far beyond a bumpy plane ride. Fluid flowing past a body — whether it's air blowing by a fuselage or water streaming across Michael Phelps's swimming suit — contorts and twists as it bounces off an edge and interferes with incoming flows, creating highly chaotic patterns. Airliners squander up to half of their fuel just overcoming the turbulence within a foot or so of the aircraft, and turbulent patterns in the bottom 100 meters of the atmosphere confound weather and climate predictions.

Physicists and engineers have had a good grip on the basic behaviors of fluids since the mid-1800s, but have been baffled by the complexity of the tumultuous flows near a boundary. "We don't really have a handle on the physics," says study co-author Ivan Marusic of the University of Melbourne in Australia. "So even though the problem is over a hundred years old, we still really haven't had a major breakthrough."

In their new study Marusic and his colleagues measured forces in a giant wind tunnel, both near and away from a wall. Data collected by probes suggested a tight link between the small-scale turbulence near a wall and large, smoother patterns of air flow farther from the wall. In particular, newly identified flow patterns called superstructures turn out to have a big effect on the turbulence near the wall. These smooth, predictable flow patterns away from the wall change the turbulence right next to the wall in predictable ways, a link that allowed Marusic and colleagues to write a mathematical formula relating the two.

"The fact is that we were sort of amazed because it's such a simple formulation," Marusic says. "Now with this model, all we need to do is measure the outer flow and we can predict what's happening near the wall."

If it pans out, the formula may be incorporated into models of climate, weather and pollution dispersal. And now that they have a better understanding of the near-wall turbulence, Marusic and his colleagues are trying to reduce it by manipulating the smooth flow of fluids away from a wall.

One of the strengths of the new model is that it allows the complex flow near boundaries to be reduced to a bare-bones motion that can be easily understood, says engineer Ronald Adrian of Arizona State University in Tempe, who authored an accompanying article in the same issue of Science.

"This model is a breakthrough step, but we're not ready to say that it's going to solve all our problems," he says. "I don't know if we have enough evidence yet to call it universal, but the hope is that it will be universal."

Image: zoagli/Flickr

Saturday 10 July 2010

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Posted: 08 May 2009 05:35 PM PDT

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