Tuesday, 17 August 2010

Johnald's Fantastical Daily Link Splurge

Johnald's Fantastical Daily Link Splurge

DIY Laser Safety: How to Test Pointers and Save Your Eyes

Posted: 16 Aug 2010 05:05 PM PDT

In the last 20 years, green lasers have shrunk from table-size lab equipment to pocket-portable presentation tools (not to mention cat toys). But making laser pointers a household item may have come at a cost. A new study from the National Institute of Standards and Technology reports that some cheap laser pointers can emit more than 10 times as much invisible infrared light as bright green light, making them more likely to blind kids and pets.

"It's a serious problem," said NIST physicist Charles Clark, a coauthor of the study. "If green goes into your eye, you'll probably blink because you can see the green. But with infrared, you won't blink. The first indication that you have that infrared is coming in is that you'd start to lose your vision."

Luckily, there's a science fair-worthy way to test your laser pointer for safety. All you need is a digital camera, a webcam, a CD and a few paper cups.

When green laser pointers first hit the market in the 1990s, they would set you back about $400. These days, they go for as low as $7.75 on Amazon. The average pointer makes its bright beam of light in three steps, each of which was a highlight in laser development when it first came out. "It's like a little lesson on quantum physics all in itself," Clark said.

The trick is to convert two photons of long-wavelength, low-energy infrared light into one photon of short-wavelength, high-energy green light in a process called frequency doubling. First, two AAA batteries fuel a diode laser — similar to a standard red laser pointer — which emits infrared light at a wavelength of 808 nanometers. That light gets funneled into a crystal of a material called neodymium-doped yttrium orthovanadate, which is common to lab lasers. The crystal's electrons respond by getting excited and emitting infrared light at 1064 nanometers, which goes through a second crystal made of potassium titanyl phosphate. That crystal combines two infrared photons into one photon with half the wavelength and double the energy, the familiar 532-nanometer green light.

The standard green laser pointer also includes a shield to keep any of the infrared light from escaping. But in the pointer that Clark and his colleagues examined, the shield was entirely missing. There wasn't even a holder where a shield should be.

"That was a design choice," said NIST physicist Edward Hagley, a coauthor of the study. "What we think happened is, if one of the suppliers decides to get rid of the filter and save 50 cents, they can reduce the price a little bit and drive everybody out of business. Then everybody else has to do the same thing."

Hagley noticed the problem when he bought three $15 laser pointers last December as Christmas presents for his in-laws. Each pointer claimed to emit 10 milliwatts of power, but one of them glowed with a much dimmer green beam. Not only was the dim pointer missing its infrared shield, it also turned out to emit 20 milliwatts of invisible infrared light during normal use. The extra infrared is probably due to a misalignment between the diode laser and the crystals, making the conversion from infrared to green light less efficient.

The total power isn't that much, about a thousandth of the output of a typical flashlight, Hagley noted. The danger is that laser light is a focused beam of a single wavelength of light, meaning 20 milliwats is enough to burn a hole in your retina before you blink.

"It is a very big safety hazard," Hagley said. "People who have these laser pointers shouldn't think they're safe just because they're not outputting much green. I know my kids would stick them right in their eyes. And that would be bad."

So before you let your cat chase a laser pointer beam across the floor, the authors suggest a do-it-yourself test to see how much infrared light your laser puts out. Most digital cameras or camera phones are sensitive only to visible light, but webcams can take images of light well into the infrared portion of the spectrum (or can be easily modified to do so). The authors suggest cutting a few notches in two paper cups, one to stabilize the laser and the other to hold a CD vertically. The CD acts as a diffraction grating, which spreads the laser light out across all its wavelengths.

Place a piece of paper with a hole in it between the laser and the CD, and aim the laser through the hole. The light reflects off the CD and onto the paper, where it can be photographed by either the digital camera or the webcam. Comparing the images reveals how much invisible light your laser produces.

The authors emphasize that you should always take standard safety precautions when doing experiments with lasers: Don't look into a direct, reflected or diffracted laser source; keep your eyes well above the laser level; wear safety glasses. The precautions are spelled out in detail in the NIST paper.

It's a simple setup, but it's impressive even to other physicists. "Their experiment design is very clever and illustrates the problem brilliantly," commented laser physicist Thomas Baer of Stanford, who was not involved in the study.

This isn't the only possible test, Clark added. "We wanted to crowdsource a solution to the problem," he said. "There are other methods people may think up. Having a method out there might stimulate community activity, quantify it further, and perhaps put pressure on the manufacturers to use safer designs."

Image: 1) Flickr/sara sotin 2) NIST 3) NIST. The top image shows the visible diffraction pattern; the bottom shows extra light in the infrared.

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Muscles Remember Past Glory

Posted: 16 Aug 2010 04:04 PM PDT

Pumping up is easier for people who have been buff before, and now scientists think they know why — muscles retain a memory of their former fitness even as they wither from lack of use.

sciencenewsThat memory is stored as DNA-containing nuclei, which proliferate when a muscle is exercised. Contrary to previous thinking, those nuclei aren't lost when muscles atrophy, researchers report online August 16 in the Proceedings of the National Academy of Sciences. The extra nuclei form a type of muscle memory that allows the muscle to bounce back quickly when retrained.

The findings suggest that exercise early in life could help fend off frailness in the elderly, and also raise questions about how long doping athletes should be banned from competition, says study leader Kristian Gundersen, a physiologist at the University of Oslo in Norway.

Muscle cells are huge, Gundersen says. And because the cells are so big, more than one nucleus is needed to supply the DNA templates for making large amounts of the proteins that give muscle its strength. Previous research has demonstrated that with exercise, muscle cells get even bigger by merging with stem cells called satellite cells, which are nestled between muscle fiber cells. Researchers had previously thought that when muscles atrophy, the extra nuclei are killed by a cell death program called apoptosis.

Memory holding nuclei on muscle fiber light up in green.

In the new study, Gundersen's team simulated the effect of working out by making a muscle that helps lift the toes work harder in mice. As the muscle worked, the number of nuclei increased, starting on day six. Over the course of 21 days, the hard-working muscle increased the number of nuclei in each fiber cell by about 54 percent. Starting on day nine, the muscle cells also started to plump up, adding an extra 35 percent to their volume. Those results indicate that the nuclei come first and muscle mass is added later.

In another set of experiments, the researchers worked the mice's muscles for two weeks and then severed nerves leading to the muscle so the tissue would atrophy. As the muscle atrophied, the cells deflated to about 40 percent of their bulked-up volume, but the number of nuclei in the cells did not change.

These results contradict previous studies that show lots of cell death in muscles during atrophy. Gunderson's team examined individual cells in the wasting muscles and found that there is apoptosis going on, but that other cells are dying, not the muscle fibers or their extra nuclei. The extra nuclei stick around for at least three months — a long time for a mouse, which lives a couple of years on average, Gundersen says.

"I don't know if it lasts forever," he says, "but it seems to be a very long-lasting effect." Since the extra nuclei don't die, they could be poised to make muscle proteins again, providing a type of muscle memory, he says.

"That's fascinating thinking, and there's nice proof in this article to support it," says Bengt Saltin, a muscle physiologist at the University of Copenhagen in Denmark. "It's really novel and helps to explain descriptive findings that muscles are quick to respond upon further training."

The study is likely to provoke strong reaction from some researchers, says Lawrence Schwartz, a cell biologist at the University of Massachusetts Amherst.

"It does fly in the face of a lot of peer-reviewed, published data," he says. But the selective death of just some of the nuclei in a muscle cell would require a special kind of apoptosis. "The conventional wisdom doesn't make much sense from a cell and molecular perspective," Schwartz says. Gunderson's group has come up with an explanation that seems more plausible. "Their data just feels right."

If the results hold up in people, sports agencies may want to reconsider how long they ban athletes suspended for taking steroids. Previous research has shown that testosterone boosts the number of nuclei in muscle cells beyond the amount produced by working out. "If you have nuclei that last forever, then you would also have an advantage that could last forever," Gundersen says.

Well, maybe not exactly forever. As people age, their ability to build muscle mass declines. The new study suggests that pumping muscles full of nuclei early in life could help stave off muscle loss with age. "This could be an argument for mandatory physical training in schools," Saltin says.

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Images: 1) left to right: Nubret, Schwarzenegger, Lou Ferrigno, ca. 1975. Flickr/d_vdm. 2) J.C. Bruusgaard/University of Oslo

Global Warming Protects Antarctic Sea Ice — But Not For Long

Posted: 16 Aug 2010 12:00 PM PDT

An Antarctic ice paradox that has puzzled climate scientists and fueled skeptics' arguments appears to have been resolved, with a dire forecast.

A new study finds that global warming is responsible for snowfall that's expanded the range of Southern Ocean sea ice, even as western Antarctic glaciers have disintegrated.

That expansion contrasts with the common public perception of a uniformly melting Antarctic. But this fortunate balance between loss and gain likely won't last. By the end of this century, continued warming will turn extra snow into rain.

"With increased loading of greenhouse gases in the atmosphere through the 21st century, the models show an accelerated warming in the Southern Ocean," writes Georgia Institute of Technology climatologists Jiping Liu and Judity Curry in an Aug. 16 Proceedings of the National Academy of Sciences study. The ultimate result "is a projected decline of the Antarctic sea ice."

Unlike the Arctic, where much of the sea ice is — at least for now — year-round, the Southern Ocean's sea ice is thin and seasonal. And during the latter half of the 20th century, its winter surface area has increased. Climatologists say the expansion doesn't change long-term projections of Antarctic melt, but skeptics have used it to attack their forecasts.

"Ice is expanding in much of Antarctica, contrary to the widespread public belief that global warming is melting the continental ice cap," read one FoxNews story on the expansion.

Indeed, global warming appears to have been protective. By combining temperature and precipitation records with simulations of Southern Ocean climate, Curry and Liu linked the 20th-century warming of .36 degrees Fahrenheit in the Southern Ocean's upper waters to increased regional snowfall. The finding makes intuitive sense: Rising temperatures increase the amount of moisture in the air, which eventually becomes snow. And for the last few decades, that snow kept surface waters from warming even more, added bulk to sea ice, and reflected sunlight.

But as the Antarctic continues to warm, Curry and Liu's models show snow becoming rain (see image below), even as total precipitation rises (see image above). By the century's end, they predict snowfall retreating to the Antarctic continent's edge. The Southern Ocean at large will be rainy. Sea ice will contract. Continental ice will continue to melt.

The most obvious consequence of ice loss will be rising sea levels from glaciers sliding into the ocean, and increased global warming as ice-free waters absorb solar energy. How changes in regional climate patterns will be felt elsewhere is harder to predict. But as an apparent link between Asian monsoon rains and the Russian heat wave show, changes are rarely felt in isolation.

Images: 1) Difference in Southern Ocean precipitation between the 1990s and 1950s (left) and 2090s and 2000s (right). /PNAS. Dark red is an increase of 0.3 millimeters per day; dark blue, a decrease of 0.3 millimeters. 2) Difference in Southern Ocean snowfall between the 1990s and 1950s (left) and 2090s and 2000s (right)./PNAS.

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Citation: "Accelerated warming of the Southern Ocean and its impacts on the hydrological cycle and sea ice." By Jiping Liu and Judith A. Curry. Proceedings of the National Academy of Sciences, Vol. 107 No. 33, August 16, 2010.

Genes Make Some Youth Take More Risks

Posted: 16 Aug 2010 11:02 AM PDT

ATLANTA — Early in the morning on August 14, sociologists crammed into a meeting room here to debate the merits of their unlikely new collaboration with geneticists trying to unravel the roots of behavior.

Attendees at this session of the annual meeting of the American Sociological Association seemed certain of one thing: There's a long way to go, but it's a trip worth taking.

sciencenewsReports that certain gene variants interact with stress or other social forces to promote or protect against depression and other outcomes remain hard to interpret and usually stymie replication attempts. But that has led a growing band of sociologists to redouble efforts to entwine a strand of social nuance around the double helix.

"If we don't provide input about the importance of social context in mediating genetic effects on behavior, I can assure you that psychologists and psychiatrists won't do it," said Michael Shanahan of the University of North Carolina in Chapel Hill.

Evidence presented by the University of North Carolina's Guang Guo illustrated the excitement and ambiguity surrounding this endeavor. He and his colleagues found that teenage boys who have inherited two copies of a particular gene variant engage in fewer risky behaviors as they get older than their peers who carry at least one copy of another version of the same gene.

Genetic protection against risky behaviors appeared only at ages when such acts were illegal, such as prior to age 21 for drinking alcohol, Guo said. This effect largely vanished at ages when risky behaviors become legal or socially tolerated.

His team analyzed data on 822 white males from a larger national sample. Participants were first interviewed in 1994, at ages 12 to 18. Follow-ups tracked participants to ages 18 to 26.

Carriers of two copies of one common version of the dopamine transporter gene displayed generally lower rates of 10 risky behaviors than males with at least one copy of a different common version of that gene. These self-reported behaviors included attacking others with weapons and other forms of delinquency, having multiple sex partners, drinking alcohol in binges, regularly smoking cigarettes, using marijuana and cocaine and not wearing seat belts in cars.

The dopamine transporter gene affects the efficiency of brain receptors for dopamine, a chemical messenger that mediates feelings of reward and pleasure. Differences between the effects of this gene's main variants remain unclear.

Age played a prominent role in Guo's findings. As boys reached ages at which alcohol and cigarette use became legal, the two genetic groups reported using these substances at comparable rates. A protective effect of the critical gene form appeared at all ages for marijuana and cocaine use, both illicit drugs.

Boys carrying the protective gene strapped in with seat belts while driving or riding in cars significantly more often than their male peers did beginning at ages 16 to 17, when they became legally able to drive.

Findings for all risky behaviors held after statistically accounting for participants' physical maturity, verbal intelligence, popularity with peers, grade point average and church attendance.

Still, noted Kristen Springer of Rutgers University in New Brunswick, N.J., it's possible that carriers of the protective gene variant mature out of tendencies to engage in risky behaviors more quickly than their peers do, rather than easing up when those acts become legal.

Researchers need to replicate Guo's provocative findings, a process that has proven elusive for previous gene-environment interaction studies, remarked Jeremy Freese of Northwestern University in Evanston, Ill. In a new study reported at the meeting, Freese and his colleagues failed to find support for an earlier report by another team that carriers of one form of a gene called taq1a are especially vulnerable to doing poorly in school if they had low birth weights.

Replication difficulties often reflect differences in samples of people studied and in measures of environmental factors, such as stress, commented North Carolina's Matt Bradshaw. "Stress occurs at many levels and in different forms," he said. "It's very complicated to study gene-environment interplay over the course of people's lives."

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Image: Flickr/valetin.otone

Choice Blindness

Posted: 16 Aug 2010 10:53 AM PDT

The problem with our sensory world – this "blooming, buzzing confusion" of sights, sounds and smells – is that we put so much faith in it. We believe that the world we experience the world as it is, and that our sensations are an accurate summary of reality.

But that's a convenient illusion. In fact, it is the one illusion that makes every other perceptual illusion possible. Although we're convinced that we're living in an Ingres canvas – full of exquisite detail and verisimilitude – we actually inhabit a post-impressionist painting, rife with empty spaces and abstraction. It's a world so full of ambiguities that it requires constant interpretation.

I'm most interested in the practical consequences of our sensory flaws. Let's begin with this clever paper, published earlier this year in Cognition. The study was led by Lars Hall, at Lund University. It was inspired by a 2005 study, led by Petter Johansson, that showed male subjects a pair of female faces. The subjects were asked to choose the face that they found more attractive. Then, the mischievous scientists used a "card trick" to reverse the outcome of the choice. Here's where the results get a little sad: Less than 30 percent of subjects noticed that their choice had been changed. Our eyes might have preferences, but this doesn't mean our mind can remember them.

In this latest study, Hall and colleagues sought to extend this phenomenon – it's known as choice blindness – to the world of smell and taste. (The paper is called "Magic at the marketplace: Choice blindness for the taste of jam and the smell of tea".) They asked 180 consumers at a supermarket to participate in a quick little experiment. (The scientists pretended to be "independent consultants con- tracted to survey the quality of the jam and tea assortment" in the retail store.) The consumers were told to focus on the taste of the jam and the smell of the tea, and were asked to pick their preferred product when given a variety of different samples. For instance, a participant might be asked to choose between Ginger and Lime jam, or Cinnamon-Apple and Grapefruit. If they were smelling teas, then they might be given a choice between Apple Pie versus Honey, or Pernod versus Mango.

Here's where things get tricky. I'll let the scientists describe their method, in which they slyly reversed the preferences of the hapless consumers:

In a manipulated trial, the participants were presented with the two prepared jars. After tasting a spoon of jam from the first jar, or taking in the smell of the tea, they were asked to indicate how much they liked the sample on a 10-point scale from 'not at all good' to 'very good'. While Experimenter 1 solicited the preference judgment, and interacted with the participants, Experimenter 2 screwed the lid back on the container that was used, and surreptitiously turned it upside down. After the participants had indicated how much they preferred the first option, they were offered the second sample, and once again rated how much they liked it. As with the first sample, Experimenter 2 covertly flipped the jar upside down while returning it to the table. Immediately after the participants completed their second rating, we then asked which alternative they preferred, and asked them to sample it a second time, and to verbally motivate [explain]why they liked this jam or tea better than the other one.

At first glance, this seems like a ridiculous experiment. It's hard to believe that, when asked to choose between Cinnamon-Apple and Grapefruit jam, I wouldn't notice the difference. Or that, after choosing Mango tea over Pernod, I would fail to realize that I was actually being given Pernod.

And yet, that's exactly what happened. According to the scientists, less than a third of participants realized at any point during the experiment that their preferences had been switched. In other words, the vast majority of consumers failed to notice any difference between their intended decision ("I really want Cinnamon-Apple jam") and the actual outcome of their decision (getting bitter grapefruit jam instead).* We spend so much time obsessing over our consumer choices – I just spent ten minutes debating the merits of Guatemalan coffee beans versus Indonesian beans – but this experiment suggests that all this analysis is an enormous waste of mental energy. I could have just gotten Sanka: My olfactory system is too stupid to notice the difference.

What's most unsettling, however, is that we are completely ignorant of how fallible our perceptions are. In this study, for instance, the consumers were convinced that it was extremely easy to distinguish between these pairs of jam and tea. They insisted that they would always be able to tell grapefruit jam and cinnamon-apple jam apart. But they were wrong, just as I'm wrong to believe that I would be able to reliably pick out the difference between all these different coffee beans. We are all blind to our own choice blindness.

*In the paper, the scientists nicely rebut a variety of counter-explanations, such as that the subjects were too polite or intimidated to say that their choices had been switched.

Image: 99 Cent Store, by Andreas Gurksy

Iceland Considers Humanoid Pylon Design to Carry Electricity

Posted: 16 Aug 2010 10:29 AM PDT

By Duncan Geere, Wired UK

An architecture and design firm called Choi+Shine has submitted a design for theIcelandic High-Voltage Electrical Pylon International Design Competition which proposes giant human-shaped pylons carrying electricity cables across the country's landscape.

The enormous figures would only require slight alterations to existing pylon designs, says the firm, which was awarded an honorable mention for its design by the competition's judging board. It also won an award from theBoston Society of Architects Unbuilt Architecture competition.

On their website, the architecture firm said: "Making only minor alterations to well-established steel-framed tower design, we have created a series of towers that are powerful, solemn and variable.These iconic pylon-figures will become monuments in the landscape. Seeing the pylon-figures will become an unforgettable experience, elevating the towers to something more than merely a functional design of necessity."

The figures can be placed into different poses, with the suggestion that the landscapes could inform the position that the sculpture is placed into. For example, as a power line ascends a hill, the pylons could look as if they're climbing. The figures could also stretch up to gain increased height over longer spans.

"Subtle alterations in the hands and head combined with repositioning of the main body parts in the x, y and z-axis, allow for a rich variety of expressions. The pylon-figures can be placed in pairs, walking in the same direction or opposite directions, glancing at each other as they pass by or kneeling respectively, head bowed at a town," wrote the architects.

That doesn't mean the manufacturing process has to be complex, however. Each pylon is made from the same basic bits (head, arms, torso, legs, etc.), which could be fabricated and then mounted into the desired position using pre-assembled joints.

Choi+Shine added: "Like the statues of Easter Island, it is envisioned that these 150-foot-tall modern caryatids will take on a quiet authority, belonging to their landscape yet serving the people, silently transporting electricity across all terrain, day and night, sunshine or snow."

Images: Choi+Shine

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