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See Inside May 2009

News Scan Briefs: Logic That Feels the Noise

Also: self-medicating bugs, apes that plan, mesh that floats and brain bias in vision

Logic That Feels the Noise
As microchips shrink, the inescapable electronic buzz that emerges from thermal fluctuations, cross talk between wires and other sources can endanger their proper function. A way around that problem could be stochastic resonance, a phenomenon in which noise can boost a weak signal and improve a system’s performance. Certain kinds of structures, such as a sensory nerve, will output a signal only when background noise is sufficiently high. Researchers at Arizona State University constructed logic gates—circuit elements that perform logic functions— that behave in a similar way. When noise levels are low, the gates perform unreliably; however, at the kinds of noise levels expected for the smallest transistors, they work correctly. Such unusual, nonlinear behavior could help microchips get smaller. Moreover, altering certain applied voltages in the circuit can reconfigure the gate on the fly, thereby creating a morphing processor. Tune in to the March 13 issue of Physical Review Letters for more details. 
—Charles Q. Choi

Bug Off
The capability to seek out medicinal plants was thought to be limited to creatures with advanced brains; for instance, chimpanzees harboring intestinal worms swallow bristly leaves to scrape the parasites from their guts. Now researchers at Wesleyan University and their colleagues find that woolly bear caterpillars (Grammia incorrupta) also self-medicate when ill. Caterpillars infested with parasitic fly maggots ate roughly twice as much alkaloid (specifically, pyrrolizidine alkaloid) as uninfested ones; such toxins naturally exist in bloodroot and other caterpillar food plants. As a result, roughly 20 percent more of the infested caterpillars survived into adulthood as compared with infested caterpillars that did not munch on the medicine. The findings, the first known instance of invertebrate self-medication, appear in the March 10 PLoS ONE.  
—Charles Q. Choi

Planning of the Apes
A rock-throwing chimp at Sweden’s Furuvik Zoo proves that nonhuman primates can plan for the future. For the past several years, Santino has put on a show of dominance every day at around 11 A.M. by yelling and running around, which is typical of male chimps. But he would occasionally lob rocks at zoo visitors. (Fortunately, his aim is terrible, and no one has been seriously hurt.) Workers found that earlier in the morning he would calmly fish his ammunition out of the moat around his habitat and chip away at concrete rocks on his island to form dessert-plate-size disks. Santino would then pile up his weapons. This observation, described in the March 10 Current Biology, confirms lab experiments showing that our fellow apes can prepare for upcoming events.
—Coco Ballantyne

Float Your Boat
Imagine a mesh that instead of letting water in repelled it so much that a life preserver made from it would support a horse. Scientists at the Harbin Institute of Technology in China created such a mesh out of copper wires 200 microns thick and pores about that size or smaller. They dunked the lattice first in silver nitrate solution and then in acid, which deposited the silver onto the copper as leaflike structures seven microns high. Like the hairs on the underside of the great diving beetle Dytis­cus marginalis, the silver leaves trap a film of air, thereby making the meshes superwater-repellent.

Postage-stamp-size boats made of these lattices could hold three times as much sand as ones made from untreated meshes, and they still floated even when their upper edges dipped below the water’s surface. Although the scientists admit that applying their superbuoyant technology to full-size ships would be unlikely—the hydrophobic repulsion is probably too weak for large vessels—they note it could lead to a new generation of miniature aquatic robots. Their work surfaces in the February 25 Applied Materials & Interfaces.
—Charles Q. Choi

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