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The Next Solar Powered Plant


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THE NEXT SOLAR-POWERED PLANT

PLANTS ARE MARVELOUSLY efficient solar-powered factories that convert carbon dioxide to cellulose. Chemical engineers have long wished they could adapt this process to synthesize other chemicals without burning fuel. Now, Mark E. Thompson, associate professor of chemistry at the University of Southern California, says he's taken the first step: the creation of a solar "chemophyll," modeled on chlorophyll in plants.

Though it converts sunlight to energy, Thompson's chemophyll bears little similarity to conventional solar cells. It consists of two thin layers of organic compounds on an ultrathin gold sheet. The inner layer functions as an electron donor and the outer as an acceptor. When light strikes the outer surface, electrons flow between the layers, establishing a current. Unlike silicon cells, the chemophyll works in electrolyte solutions conducive to chemical reactions.

The chemophyll produces less power than a typical silicon device. But with better materials, Thompson hopes to achieve higher voltages. This could lead to cells that act as catalysts to assist the conversion of COsubscript2 to methane, or to separate clean-burning hydrogen from oxygen in sea water.EDITED BY NEIL GROSSReturn to top

GENE THERAPY: NEW HOPE FOR BIVALVES

GENE THERAPY HASN'T CURED any human ailments. But it may offer a way to immunize oysters, clams, and mussels against such viruses as hepatitis A, which can be passed to humans. Molecular biologists Thomas Chen of the University of Connecticut and Jane Burns at the University of California, San Diego, have tailored a retrovirus to carry immunizing genes into shellfish.

In an experiment described in the Apr. 16 issue of the Proceedings of the National Academy of Sciences, the scientists altered the protein coating of a retrovirus that typically infects only mammals, enabling it to attach to receptors on fish cells. Next, they loaded the retrovirus with a test gene and injected it into surf clams. The gene was picked up by the clams' DNA and passed on to their offspring, becoming a permanent part of their genetic code. In principle, genes altered to confer disease resistance could be transferred by similar means. Roy Martin, vice-president of the National Fisheries Institute in Arlington, Va., thinks certified disease-free shellfish would appeal to many consumers.

Gene transfers could benefit America's $300 million shellfish industry in other ways, too. A trout growth hormone boosts shellfish growth by 50%, Chen says. The gene that encodes the hormone is a research target for Pangenix, a San Diego biotech company that licensed the delivery technique from the two universities.EDITED BY NEIL GROSS By David GrahamReturn to top

IT'S A HARD, HARD ROAD

CONCRETE TAKES SO LONG TO HARDEN COM-pletely--28 days, for a standard formula--that road-repair crews tend to fall back on less durable patching materials. New Jersey's Transportation Dept. wanted concrete that could be poured after the evening rush hour and be ready by the next morning. So it challenged suppliers.

The winner: Sika Corp., the Lyndhurst (N.J.)-based U.S. arm of Sika AG, in Zurich. Its mixture, Sika Rapid, hardens concrete made from standard cement so quickly that it can support normal traffic in six hours. That means it can withstand a compressive force of 2,500 to 3,000 pounds per square inch and a flexing strength of 300 to 350 PSI. And it keeps hardening after that.

The Swiss formula was tested with the New Jersey Institute of Technology, Rutgers University, cement supplier Essroc of Nazareth, Pa., and Redy-Mixt Konkcrete of Woodbury, N.J. It's being road-tested this spring.EDITED BY NEIL GROSS By Peter CoyReturn to top


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