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Nanowired to Ferret Out Explosives


Every hour, a land mine kills or maims as many as three people. Tens of millions of these deadly devices are scattered across 70 countries.

Chemists at the University of California at San Diego believe they may have a cost-effective solution for ferreting out land mines and other bombs. By encasing a silicon-based polymer in conductive molecules, they've developed a nanowire that can detect very faint traces of explosives in air or under water. When the polymeric wires--each only 1/2,000th the diameter of a human hair--are sprayed on filter paper, they normally glow under an ultraviolet light. But the glow gets switched off by even trace amounts of an explosive--on someone's hand, for example (top), or coming from hidden explosives. So a surface coated with the substance, combined with a portable UV lamp, would create a small bomb detector that can find sea mines and booby traps along beaches, or spot guns in airline baggage or at border checkpoints. A system based on this technology should be less costly to make than existing approaches, says biochemistry professor William C. Trogler, who assisted with the research. Few materials conjure up an image of strength better than steel. But peering into his electron microscope at Northwestern University, Laurence D. Marks can view tiny tubes that are twice as strong as steel, yet 1,000 times thinner than a human hair. Marks, director of the university's Center for Transportation Nanotechnology, led a team that scored a first by imaging and analyzing a new class of nanostructures made of hexagons of boron and nitrogen atoms.

Marks foresees the boron-nitride nanostructures finding a home in the aerospace industry. The molecules are similar to their better-known cousins, carbon nanotubes. Both have walls only one atom thick. And because the new nanostructures are tough, light, and flexible--just like the carbon variety--they could be used to coat gears in aircraft or rocket engines, for instance. But here's the difference: When a carbon nanostructure oxidizes, it produces carbon monoxide or carbon dioxide--not useful, in engineering terms, and perhaps even harmful. When boron nitride oxidizes, on the other hand, the molecules form boric acid, which is an excellent solid lubricant. "If applications can be found, taking it commercial would be easy," Marks says.

The boron nitride work is the first big breakthrough at Marks's federally funded center, which opened in November. Next, he hopes to work on nanostructures composed of molybdenum disulfide. The compound is an even better solid lubricant, so Marks expects that it could be especially handy in space--keeping antennas and other movable parts on satellites from freezing. People send Saleh A. Naser unusual substances. From the mountains of Russia and the jungles of Vietnam, plant extracts gathered by herbalists and shamans flow into the molecular biology department at the University of Central Florida, where associate professor Naser tests them for efficacy against drug-resistant strains of tuberculosis. He has studied some intriguing compounds over the years. But none compares to a substance that's common in North America: nicotine. "We've looked at thousands of compounds, from natural sources and synthetic," he says. "By far, nicotine is the most effective I have ever seen in the test tube."

Naser, who gets no money from tobacco growers, says he and his team stumbled onto nicotine's antibacterial activity while studying proteins in the leaf. Not knowing which of the compounds in the plant were responsible, they tested nicotine--which has other medicinal effects--and immediately hit home. "We're sure it's the active ingredient, and it's extraordinary how small the required amounts are," Naser says. He is planning further tests in tissue cultures and lab animals. -- For afflictions such as mad cow disease, which are caused by deformed "prion" proteins, there is no positive diagnosis until after the patient dies. But scientists at Serono Pharmaceutical Research Institute in Geneva, reporting in the June 14 issue of Nature, think they can diagnose these diseases in living patients by speeding up the proliferation of prions in a test tube containing a sample of spinal fluid. If any dangerous prions are present in the sample, then in just hours their numbers will increase to an extent that would normally take 30 months--the time required to spot abnormalities in people and animals.

-- Noting that handheld vacuum cleaners now make up 40% of all vacuum sales, Dallas-based Electrolux plans to cut the cord on its full-size vacuum cleaners. To do so, the company, which isn't part of Sweden's Electrolux, has designed cleaners that use fuel cells--gadgets that generate electricity from a chemical reaction between hydrogen and oxygen. Small snap-in tanks will hold enough hydrogen to last for a month or so. The new sweepers, due in 2003, will be priced between $300 and $1000.


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