How Jesus did it? Haha Just joking!

How to walk on water

Water snails crawl along under the water surface on ripples of slime.

Philip Ball

Some water snails have an extraordinary way of getting around: they crawl upside down at the water's surface. A team of US researchers may now have figured out how they do it.

At face value, the snails' motion seems almost impossible: how can they drag themselves across a fluid surface that they can't actually grip? But Eric Lauga of the University of California, San Diego and his colleagues say that, by creating little ripples in the surface, water snails transform it into one that does effectively offer a 'foothold'.

The question of how snails move has been studied for at least a century, but only relatively recently has an understanding emerged. For land snails, the secret's in the slime: the trail of mucus is sticky, but flows like a liquid if stressed beyond a certain level. So as the snail's 'foot' presses on it, the mucus offers an adhesive grip for some parts of the foot while lubricating the movement of other parts.

But this mechanism needs a solid surface to which the snail can stick. It won't work in water. Nonetheless, some freshwater and marine snails crawl 'hanging' from the water surface while secreting a trail of mucus. How do they do it?

Making waves

Lauga and colleagues studied the common freshwater snail Sorbeoconcha physidae , which can crawl at a respectable speed (in snail terms) of 0.2 cm per second. The snails stay buoyant by trapping some air inside their shells.

The snail's foot wrinkles into little rippling waves with a wavelength of about a millimetre and this produces corresponding waves in the mucus layer that it secretes between the foot and the air. But because surface tension constrains the deformation of the mucus, the shape of its top surface (in contact with air) doesn't exactly mirror that of the bottom surface (in contact with the foot). In effect, parts of the mucus film get squeezed, and parts get stretched, creating a pressure difference that pushes the foot forwards.

The researchers think their theory, described in a paper soon to be published in the journal Physics of Fluids ¹, offers only the beginnings of a full answer. It may also depend on the complex ways in which the mucus flows when squeezed, for example.

Sticky problem

Not all water snails move this way, says Lauga's colleague Anette Hosoi, of the Massachusetts Institute of Technology in Cambridge, Massachusetts. Many propel themselves using arrays of tiny hair-like appendages called cilia. Others simply swim underwater, or crawl along the bottom.

The researchers suspect that, as well as elucidating a biological puzzle, the findings might point to a new method of propulsion. Hosoi and her co-workers have already copied the adhesive/lubricating propulsive method of land snails to drive a robotic device². Now it might be feasible to build similar devices that walk on water, although Hosoi says that this will require tricky mastery of buoyancy to keep them floating right at the water surface.

That earlier 'artificial snail' was built for sheer curiosity. But Hosoi says that once she and her colleagues reported it, "suddenly people were coming out of the woodwork": the researchers were approached by people in the oil industry and in medical research, among others.

So she suspects that, if they succeed with a synthetic water snail, "we may be hearing from industry again".

• References
  
  • Lee, S. et al., Phys. Fluids (in press, 2008).
    
  • Chan, B. et al. Phys. Fluids 17, 113101 (2005). | Article | ChemPort |
    

http://www.nature.com/news/2008/080626/full/news.2008.915.html?s=news_rss

The clock on men goes tick tock too.

Ouch to guys. Girls, you're not alone. Ouch.. even coffee..

 

The female biological clock—its tick-tock marking the decline of fertility that grows louder as a woman reaches middle age—is deeply ingrained in popular consciousness. Take this scene from the film Bridget Jones's Diary: Bridget's Uncle Geoffrey reminds her that as a career girl she "can't put it off forever," alluding to her declining fertility. His wife Una chimes in: "tick-tock, tick-tock," her finger wagging like a metronome.

The biological clock, although just a metaphor, refers to a real phenomenon: Women over 35 years of age are only half as likely to become pregnant in the most fertile part of their menstrual cycle than women younger than 26.

So do men suffer from the same thing?

"For women, a biological clock is a decline in fertility and an increased chance of having genetically abnormal babies as they age," says Harry Fisch, director of New York City's Male Reproductive Center and author of The Male Biological Clock: The Startling News About Aging, Sexuality, and Fertility in Men. "And that's exactly what's happening with men."

So how did Indian farmer Nanu Ram Jogi sire a healthy child at the age of 90 last year? Such a feat would be impossible for a woman, even in an age when Carmela Bousada, 67, gave birth to twins in January 2007 after lying about her age to the doctors who gave her in vitro fertilization. Whereas fertility declines along with testosterone levels as men age, it doesn't drop to zero.

Still, Jogi is definitely the exception rather than the rule. One study found that the odds of fatherhood for those under the age of 30 was 32.1 percent compared with 20 percent over the age of 50, signifying a 38 percent drop in male fertility across that age gap.

One study examined 97 men between the ages of 22 and 80 and found that as they aged their semen volume decreased by 0.001 ounce (0.03 milliliter) per year from an average total of 0.09 ounce (2.7 milliliters)  and their "total progressively motile sperm count"—a rough index for the fertility potential of one's sperm based on its movement—decreased about five percent with each year they aged.

Fisch and his colleagues have also found that the children of women over 35 whose babies' fathers were also of that age were more likely to have Down's syndrome than offspring whose fathers were younger.

In other studies, older men were more likely to father children with mental illness or other deficits. Roughly 11 children out of a thousand conceived by men over age 50 developed schizophrenia compared with under three children out of a thousand for fathers under 20 in one study from the Archives of General Psychiatry. And the children of men 40 years or older were nearly six times more likely to have autism spectrum disorders than kids begot by men under 30.

So do men's sperm get staler over time? To maintain sperm levels, cells known as germ cells must continue dividing. After all, men find ways to dispose of sperm—ahem—and once ejaculated they only survive for several days. By the age of 50, these germ cells will have divided 840 times. Each one of those divisions is an opportunity for something to go wrong. "There's more of a chance to have genetic abnormalities the more the cells divide," Fisch says. In sperm these mutations dot the genes with changes in the basic structure of the DNA—and can lead to problems in the resulting offspring.

Bioengineer Narendra Singh of the University of Washington in Seattle and his colleagues compared the sperm of men of different ages. Sure enough, sperm in men older than 35 had more DNA damage than that from younger men. And although unhealthy sperm are supposed to commit cell suicide, some of the sperm they looked at had lost that ability to "take one for the team"—meaning they'd be around to fertilize an egg. "This may lead to offspring with defective DNA, which may translate to mental and physical defects," Singh says.

Can men prevent this damage? No, but they may be able to mitigate it. There are factors within men's control that can accelerate adverse effects: alcohol, smoking, drugs and environmental pollution—even coffee consumption. So avoid them, says Singh.

Still, even after correcting for various lifestyle factors, the DNA of sperm are increasingly damaged with advancing age.

"The question is, can we reverse the [male] biological clock?" asks Fisch, who is studying various ways to keep sperm healthy.

Perhaps Bridget Jones's Uncle Geoffrey and Aunt Una should have chastised her love interest, Mark Darcy, too, for procrastinating procreation. That "tick-tock, tick-tock," it would seem, applies to both sexes.

 

http://www.sciam.com/article.cfm?id=fact-or-fiction-men-have-biological-clocks

Popularity…

So you really can't make others like you by doing nice stuff? Interesting.

How do you make a reputation for yourself?

Category: Research • Social
Posted on: June 26, 2008 12:35 PM, by Dave Munger

My high school experience, like that of nearly everyone who attended my school, was a perplexing one. It seemed there were only a few "popular" people -- those that everyone knew and liked -- and wanted to be like. Everyone else was much like me: they struggled to become more popular, with little success. Everyone had a few friends, but somehow these friends were never as good as the popular people would be, or so it seemed.

One of the things that I believed was preventing me from becoming popular was my reputation. Those who knew me saw me in a certain way -- a non-popular way. Maybe if I started to do popular-ish things, then people would notice me and I'd eventually become popular. I tried being nice to people, telling jokes, buying people lunch, wearing better clothes, but none of it seemed to matter much. Everyone who bothered to notice me thought pretty much the same of me as they had before.

But being popular and having a good reputation aren't just valuable in high school. The people who get promotions and make sales in business always seem to be the ones who've got the most connections. Sure, knowledge and skill matter, but "knowing the right people" also seems to matter, especially if the right people think highly of you.

But there have been surprisingly few studies of how reputations -- good or bad -- develop. Cameron Anderson and Aiwa Shirako say there hasn't been any realistic study exploring how peoples' reputations are formed. The few laboratory studies typically don't account for secondhand information -- gossip -- which can be an important source of information about a person. To do this requires a long-term setting involving many interactions among a large group of individuals. Anderson and Shirako found such a setting in a semester-long business-school negotiation course with 39 students.

In this class, students were frequently divided into small groups to participate in realistic business negotiation scenarios: the purchase of a business, hiring, and mediating conflicts between employees. At the start of the class, each student rated how well they knew all of their classmates. After each negotiation session, partners were rated for how trustworthy, empathetic, and caring they had been in the session. Finally, independent judges rated how successful each negotiator had been in each session -- both in securing their own interests, and in achieving a result that was satisfactory to all participants.

At the end of the semester, each student was asked to nominate the most trustworthy and sympathetic negotiators. People who received a lot of nominations in these categories were said to have developed a reputation for cooperativeness. Students were also asked to nominate the most aggressive and ruthless negotiators, which combined to form a measure of a reputation for selfishness. The key to this study was the comparison of actual cooperative and selfish behavior with those reputations. Were people who were actually cooperative in negotiations nominated by their classmates? It depends on one additional factor: how popular each student was at the beginning of the course. Take a look at this graph of the results for cooperativeness:

It turns out that your reputation for cooperativeness is only affected by your behavior if you're already popular. If you're not popular, it appears that no one takes notice of your behavior, so it has no impact on your reputation. People with lots of social connections can build a good reputation -- or a bad one -- with much more ease than people with few social connections.

Anderson and Shirako also asked students what the bases for their reputation nominations were, and found that popular people were nominated significantly more frequently based both on first- and second-hand knowledge. So if a person is popular, people are more likely to talk about them, more likely to act based on what they've heard, and even more likely to notice the popular person's behavior when talking with them face-to-face.

So it may be that the reason I never became popular in high school was that I was going about it backwards. Instead of trying to acquire a reputation first and get friends later, I needed to get the friends first, then work on my reputation. But how do you get friends if you don't have a reputation -- good or bad? That, unfortunately, is what makes high school such an awkward time for so many of us.

Cameron Anderson, Aiwa Shirako (2008). Are individuals' reputations related to their history of behavior? Journal of Personality and Social Psychology, 94 (2), 320-333 DOI: 10.1037/0022-3514.94.2.320

 

http://scienceblogs.com/cognitivedaily/2008/06/how_do_you_make_a_reputation.php

Holy. Crap.

Legacy of ancient impact means Mars now comes with either thick or thin crust.
Katharine Sanderson

Kaboom! When a giant impact whacked into a young Mars around 4 billion years ago, the impact made such a huge dent in the northern hemisphere that it left the entire planet lop-sided.
This dent has been partly hidden from the view of scientists because of the large Tharsis volcanic range that now spans the area. But what scientists had noticed was a striking difference of up to 30 kilometres in the thickness of the planet’s crust between the northern lowlands and the southern highlands.
This ‘crustal dichotomy’ was thought to be caused by either a giant impact, or by a shifting of the martian mantle. A set of calculations by Jeffrey Andrews-Hanna, of the Massachusetts Institute of Technology, and colleagues, now offers strong evidence for a huge impact, forming a crater four times bigger than anything seen before in our Solar System. The work is published in Nature 1.
Andrews-Hanna and his team used computer modelling to 'remove' Tharsis from the martian landscape, to try and work out why the transition between thick and thin crusts was so marked. And there he saw it – a huge crater, 10,600 kilometres long and 8,500 kilometres wide. “The lowlands of Mars is an enormous elliptical projection,” says Andrews-Hanna. “There’s only one process we know of that causes this kind of depression" – a very big impact.
Other known basins created by enormous impacts basins are also elliptical, and they are a similar shape to the northern lowlands of Mars, he says.
Through thick and thin
The meteorite would have blasted out the rock from the planet's northern lowlands, forming the crater called the Borealis basin, and some of this ejecta would have been deposited round on the other side of the planet, making its crust even thicker.
“This is the defining event in Mars’s history,” says Andrews-Hanna. This computer-simulated video suggests what it might have looked like to anyone around back then.
This idea that the crustal dichotomy was caused by a giant impact was suggested2 in the 1980s by Don Wilhelms from the US Geological Survey and Steven Squyres, who has more recently found fame as director of the Mars Rover project. “When Don Wilhelms and I first proposed this idea almost 25 years ago, we felt that it was consistent with the observations, and our intuition was that it was physically possible,” says Squyres. “That's really all it was, though – intuition. We didn't actually do the calculations.”
Improved computational tools in the intervening years have now allowed this test of the idea to be done, says Squyres. “This still doesn't prove that a giant impact created the dichotomy, of course,” he says, “we weren't there to see it happen, and all of this is inference. But it means that it's a physically reasonable idea, and that's a significant step forward.”

References
Andrews-Hanna, J. C., Zuber, M. T. & Banerdt, W. B. Nature 453, 1212-1215 (2008)
Wilhelms, D. E & Squyres, S. W. Nature 309, 138-140 (1984)

wolverine frog

June 24, 2008—Eleven species of African frogs—including Trichobatracus robustus (top) and Astylosternus perreti (bottom)—sport a Wolverine-like defense mechanism, scientists have announced. When threatened, the amphibians pierce their skin with toe bones, sprouting makeshift claws with which to attack predators.
David C. Blackburn, a biologist at Harvard University, came across the frogs while conducting fieldwork in Cameroon. When he picked up one of the fist-size amphibians, it kicked its hind legs violently.
"I was surprised to come across frogs that can give you such a nasty scratch when you pick them up," Blackburn said. "When I got back to the U.S., I used preserved museum specimens to study the anatomy of these claws, because it was obviously pretty unusual."
After going through 63 species of African frogs, Blackburn found that in at least 11, the bones at the ends of the toes are connected to smaller and sharper free-floating bones. These smaller end bones are part of structures called nodules that are connected to the rest of the foot by a collagen-rich sheath. (Related: video: "See-Through Frogs Bred By Japanese Researchers" [October 1, 2007].)
By flexing a certain foot muscle, the frog causes the bone to retreat from the nodule and pierce the skin, revealing a clawlike structure. Unlike ordinary claws, such as those of a cat's, the frog bones do not possess a protective coating of a protein known as keratin, nor do they emerge from a specialized structure in the foot.
The frogs, all in the genera Astylosternus, Trichobatracus, or Scotobleps, appear to employ this mechanism only when threatened, as revealing the claws causes traumatic damage to the frogs' skin.
Blackburn's study is described in a forthcoming issue of the journal Biology Letters.

http://news.nationalgeographic.com/news/2008/06/080624-frog-claws.html

adverts -.-

ok adverts pissing me off. need new tag board.

Coils

i can already imagine this in our physics textbook -.-

Universal law of coiling

Physicists reveal why paper curls the way it does.

Philip Ball

D. WHITEHEAD/CORBIS

Ever noticed that when a piece of paper is rolled into a tube, the innermost part straightens away from the coil before touching down? Try it and see. A team of researchers has investigated this phenomenon and discovered that the precise shape of this rolled-up material is not only surprisingly subtle but also universal.

The angle that the innermost sheet makes with the coiled roll (α in the diagram) is always the same, say Enrique Cerda of the University of Santiago in Chile and his co-workers, about 24.1° — regardless of the thickness of the sheet or the width of the coil¹.

What's more, the angle subtended between this contact point and the place where the sheet first detaches from the coil's inner face (β ) is always 125.2°. This universal shape confounds the intuition that stiffer sheets would have a different cross-sectional profile from flimsy ones. Rolled-up carpet, paper or metal will all adopt the same shape.

To prove it, Cerda's team measured the 'touchdown' angle for a thin slab of mica (a sheet-like mineral) and a strip of metal coiled within tubes of various widths. They found that the angles deviated from the predicted 24.1° by no more than about a degree.

“Universal angles have come up before in other situations that involve thin sheets and filaments,” says Lakshminarayanan Mahadevan of Harvard University, who was not involved in the work. For example, he and Cerda have previously calculated the universal shapes of flat sheets confined in cylinders by conical deformation, as generated by pushing down on the sheet with a pencil tip². Universal shapes arise, he says, “because of the strong constraints that geometry imposes on the possible deformations”.

“This type of constraint occurs in other systems as well,” Mahadevan explains. “For example, the characteristic size of a drop that breaks off from a stream of fluid always has a size that is comparable to the filament diameter, irrespective of the material of the fluid.”

The work is the kind of basic mechanics that one might have expected to have been done already. It is true that the problem is mathematically daunting, involving the calculation of forces and torques that create mechanical equilibrium in a curved, elastic sheet pressing outwards against a confining tube. But Mahadevan says, “the question could have been addressed a long time ago, except for the fact that some of the equations require numerical or graphical solution — which might have slowed things down just a trifle”. Cerda says that the phenomenon was well within the reach of eighteenth-century mathematics, but “it seems no one thought to ask”.

The researchers say that analogous shapes should exist for coiled sheets in other confining geometries, such as cones or coiled fibres. The coiling of fibres might be relevant to the packing of DNA inside the protein capsules of viruses, and to the mechanisms of biological structures that provide cellular scaffolding.

• References

  1. Romero, V. , Witten, T. A. & Cerda, E. Proc. R. Soc. A doi:10.1098/rspa.2007.0372 (2008).
  2. Cerda, E. & Mahadevan, L. Proc. R. Soc. A 461, 671–700 (2005).

Defined moral rules

What do you think?

People are incredibly social beings, and we rely heavily on our interactions with others to thrive, and even survive, in the world. To avoid chaos in these interactions, humans create social norms. These rules and regulations establish appropriate and acceptable ways for us to act and respond to each other. For instance, when waiting in line, we expect people also to wait their turn. As a result, we get upset when someone decides to cut in line: they violated a social norm.

But how are social norms maintained? And what makes us comply with social norms? Primarily, the answer is that, if we don't follow the rules, we might get in trouble. Numerous studies demonstrate that, when the threat of punishment is removed, people tend to disregard social norms. The neat and orderly line disintegrates.

It remains unclear, however, how the brain processes the threat of punishment when deciding whether or not to comply with a social norm. A recent study conducted by neuroscientist Manfred Spitzer and his colleagues at the University of Ulm in Germany and the University of Zurich in Switzerland tried to shed light on this mystery. The researchers put 24 healthy male students in a functional magnetic resonance imaging (fMRI) scanner to see what parts of the brain were activated during a two-person social exchange with real monetary stakes.

In this game, a research participant ("Person A") was given money, and had to decide how much he wanted to give to another person ("Person B") and how much he wanted to keep. In one variation of the game—the "punishment threat condition"—Person B could punish Person A if he or she believed that Person A had divided the money unfairly, or violated the "fairness social norm." In another situation, there was no punishment threat and Person A could act freely without worrying about the consequences. The researchers sought to find out how much more money Person A would give to Person B under the threat of punishment, and what brain circuits are associated with this change in behavior. 

Not surprisingly, the threat of punishment made people act more fairly. In the "punishment threat condition" people split the money close to equally. However, when Person B had no recourse, the people given the money acted very differently and gave away, on average, less than 10 percent of the money.

One of the interesting things about social norm compliance, however, is that there is tremendous individual variation. Some people would never cut in line or act unfairly, whereas others don't think twice about it. Using a questionnaire, the researchers measured each participant's "Machiavellism," a combination of selfishness and opportunism, which is often used to describe someone's tendency to manipulate other people for personal gain. Sure enough, the people with high Machiavellism scores gave less money away when there was no punishment threat and were best at avoiding punishment when the threat of punishment was present. Therefore, these individuals earned the most money overall.

When the researchers looked at the brain activity of people playing this simple game, they found a consistent pattern. One region in the frontal lobes, the orbitofrontal cortex, seemed to be responsible for evaluating the potential for punishment. In other words, it figured out whether or not violating the social norm would get us in trouble. A second brain region, the dorsolateral prefrontal cortex, was responsible for inhibiting the natural tendency to keep most of the money (this would be the greedy thing to do) if this action might lead to future punishment. Interestingly, these brain areas only were activated when the threat of punishment came from a real person, and not a computer that was programmed to act like a real person.

Furthermore, just as Machiavellism personality traits influenced how people behave, these traits also relate to what is happening in the brain. The orbitofrontal cortex was most activated in the more self-interested, opportunistic people. This finding makes sense because, if the orbitofrontal cortex is helping people detect and evaluate threats, then it should be most active in people who are worried about getting punished. This study can also help us understand what might be happening in the brains of people who struggle to follow social norms, which is what happens in mental illnesses such as psychopathy and antisocial personality disorder.

Of course, many different variables not studied in this experiment can also affect social norm compliance. Even a norm as seemingly straightforward as "fairness" can get pretty complicated pretty quickly. The social norm of fairness, after all, does not always mean an equal distribution of goods. Someone may deserve more based on effort, talent or simply the feeling of entitlement that comes from social status. For instance, one could argue that in the non-punishment situation, Person A was put in a position of power, because he or she was given complete control of the money. On the other hand, when Person B is given the right to punish Person A, Person B is now put in a superior position of power. And accordingly, the social norm for Person A changes: it is no longer acceptable for him to keep all the money for himself. This adjustment suggests that the brain activity evident in the Spitzer study could, in part, be related to changes in power and status between the punishment and non-punishment condition. In fact, in a recent study, we found that the dorsolateral prefrontal cortex was more activated when interacting with a person who is in superior social position.

We may have a long road ahead to understand the complexity of the brain mechanism underlying human social behavior fully, but Spitzer and his colleagues should certainly be commended for their efforts and well-designed research experiment on social norm compliance. Although questions remain and the interpretations are not completely straightforward, this study takes us one step closer to solving the puzzle of the social brain.

http://www.sciam.com/article.cfm?id=why-the-brain-follows-the