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19 March 2011 | NewScientist | 21 BUILDING a sticky substance into car bodywork could make them more resistant to impacts, new experiments suggest. Paula Mellado of Harvard University and her colleagues tested how flexible, CD-sized plastic discs crumple when their centres are pulled through coin- sized holes. The sides of each disc are forced to bend inwards, forming cone-like structures that rub against one another. In an upcoming edition of Physical Review E, the team reports that discs coated with a thin layer of glue were harder to pull through the hole than uncoated discs. “When you have a sticky membrane, the two sides will touch each other, but they won’t slip,” says Mellado. With the sides sticking to one another, the disc resists further deformation, Mini brain scanner lets rats run free IT IS a first – a mini brain scanner small enough for rats to wear that lets you compare the animals’ behaviour with what is going on in their brains. Rats usually have to be anaesthetised before they can be scanned, but the “ratCAP” makes it possible to watch how the animals behave and observe their brain chemistry at the same time, says David Schlyer, co-leader of the team that developed the mini- scanner at Brookhaven National Laboratory in Upton, New York. The positron-emission tomography scanner encircles the rat’s head and constantly images the activity of vital brain chemicals such as dopamine and serotonin (Nature Methods, DOI: 10.1038/nmeth.1582). The team is also hoping to develop wearable scanners for people and monkeys, so they too can engage in activities while their brains are being scanned. Black hole’s burps may blow bubbles around Milky Way STARS plunging into the giant black hole at the centre of our galaxy can explain two huge bubbles of gamma rays that NASA’s Fermi space telescope discovered last year. The bubbles tower 25,000 light years above and below the Milky Way’s disc of stars. More than 100,000 stars swarm within a light year of the black hole. Now, Kwong Sang Cheng of the University of Hong Kong and his colleagues calculate that the black hole’s gravity tears one of these stars apart every 30,000 years (The Astrophysical Journal Letters, in press). Half the star’s mass falls into the black hole, NASA/GODDARD SPACE FLIGHT CENTER IN BRIEF Bumper sticker has a whole new meaning and cannot easily curl up to pass through the hole. She suggests that adding a sticky coating to the surfaces of sheet materials that are likely to pass across each other in an impact, such as those used to make cars, could make them more resistant to impacts, without adding much to their weight. Such a sticky surface “could make a good impact-absorbing material”, says Tom Witten at the University of Chicago. while the other half shoots away at high speed, shocking gas that lies in the halo around the Milky Way’s disc until it emits gamma rays. However, Douglas Finkbeiner of the Harvard- Smithsonian Center for Astrophysics in Cambridge, Massachusetts, thinks individual stars dribbling into the black hole would probably not produce the sharp edges seen around the Fermi bubbles. “To make a sharp edge, the mechanism really needs to turn on and turn off,” he says. “My money is on the explanations that involve something more dramatic and more rare.” He suspects that every 1 million to 10 million years, a huge cloud of gas or an entire cluster of stars plummets into the black hole. The most recent such event, he says, produced the Fermi bubbles we see today. WHETHER you are looking for food or fleeing a predator, the same kind of gene controls whether you stay or go. Cori Bargmann of Rockefeller University in New York City and colleagues studied nematode worms (Caenorhabditis elegans) to find out how they decide whether to leave a dwindling food source. The gene tyra-3 helps control the decision. It codes for a neurotransmitter receptor related to the one for adrenalin, which controls the “fight or flight” response (Nature, DOI: 10.1038/ nature09821). The study suggests that the genes have conserved their function throughout animal evolution, Bargmann says. “This is an ancient vocabulary,” he says. Should I stay or should I go?
