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Findings
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A laser that's out of this world A fiber-optic laser system no bigger than a laptop computer could orbit Earth via satellite within the decade as the next high-tech tool to test the health of the atmosphere. The project, to be led by researchers at the Whiting School of Engineering and NASA's Goddard Space Flight Center, would gather data for monitoring air pollution, the status of the ozone layer, and atmospheric changes that might be leading to global warming. NASA recently awarded a three-year, $815,500 grant to the Hopkins-Goddard team. The new laser is one of a dozen proposals selected by NASA's Earth Science Technology Office, which is interested in developing better lasers for use in atmospheric sensing applications. Scientists hope to develop a prototype within three years. The fiber-optic technology--simple, light, compact, and efficient--currently is used mostly in research and telecommunications, but is ideal for space travel. "Conventional lasers are inefficient and extremely bulky," says principal investigator Jin Kang, a Hopkins assistant professor of electrical and computer engineering. Among other limits, such lasers require carefully aligned mirrors, lenses, and other optical devices. In a fiber-optic laser, as the light goes around a loop of fibers, it becomes amplified, Kang says. "Fiber optic lasers are simple," he adds. "If you look at a thread of your clothes, it's not that much thicker." Kang, who came to Hopkins in 1998, has specialized in photonics, working with fiber-optic lasers during his three years at the U.S. Naval Research Laboratory. For the NASA project, Kang will design a high-powered ultraviolet laser light source. Goddard scientists will create the laser device and spacecraft. "All the power supplies, all the coolers, all of that has got to be shrunk down into one highly modular package rugged enough for the rigors of space flight," says Harry Shaw, associate branch head for Goddard's Component Technologies and Radiation Effects, in Greenbelt, Md. The Hopkins-Goddard laser will likely become a critical device in advanced versions of NASA's LIDAR system, which works in a manner similar to radar but uses light instead of radio waves. Light beams aimed at the atmosphere hit gas molecules and bounce back, carrying a wavelength absorption "fingerprint" that indicates the type and density of the gas. Under new technology applications, fiber-optic lasers could join other test instruments in smaller and cheaper satellites, allowing more widespread use in space. A satellite rigged with a UV fiber-optic laser also would better provide data gathered in the atmosphere's ultraviolet range, allowing more in-depth analysis of ozone levels and a more advanced glimpse into atmospheric chemistry. --JCS
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Of breakups and "babies" Hopkins astronomer Harold Weaver did not expect to see high drama when he began using the Hubble Space Telescope (HST) to observe Comet LINEAR, an erstwhile, unextraordinary comet. But Weaver got a surprise on July 5 when LINEAR dramatically increased in brightness as its core exploded. Over the next few days, the comet blew off a chunk of its crust and shot out an immense amount of dust, "like a giant geyser," says Weaver. The dust reflected sunlight, causing an intense brightening. Later in the month, ground-based observers reported that the comet was missing in action. They assumed it had disintegrated. So in early August, Weaver went back for a second look with Hubble. He saw that LINEAR had broken up into dozens of smaller pieces and dust. "We saw all these mini comets, fragments, like comet babies," says Weaver. These smaller pieces appear now to have essentially vaporized. Astronomers do not know what caused the explosion, says Weaver. Something may have forced LINEAR out of its normal orbit, sending the comet closer to the sun, heating an explosive section of the comet's core, he says. "But we don't really know why it broke up. "It's the first time we've ever watched the breakup of a comet in such detail," he adds. The results support the popular theory that comet nuclei are really made up of a cluster of smaller icy bodies called "cometesimals." --MH
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New promise for producing infection
fighters Driven by emerging diseases and growing bacterial resistance to existing antibiotics, scientists are eagerly pursuing new antibacterial drugs. Their quest could now be easier, thanks to a new process for synthesizing chemical compounds developed by a Hopkins team led by Thomas Lectka, associate professor of chemistry. The process involves a class of drugs--including penicillin and other infection fighters--known as beta-lactams. Such compounds are "chiral," meaning they can appear in both a left-handed and right-handed form (with each form known as an enantiomer). Though identical in structure, the enantiomers can react differently to enzymes; one enantiomer may be beneficial and the other harmful, dramatically altering a drug's biochemical properties. To avoid the confounding effects posed by dual enantiomers, Lectka has focused on synthesis techniques that produce chiral compounds with just one form. As a catalyst, his team uses quinine--a natural substance that was once a premier malaria treatment and is itself enantiomerically pure--as a catalyst. A small amount of quinine can produce large batches of single enantiomer beta-lactams, and since quinine is not changed by the reaction, it can be used indefinitely, Lectka notes. "Beta-lactams have been critical tools for fighting the spread of bacterial infections in the past, and they could be so again," says Lectka, noting that in addition to their use as antibiotics, "they have recently found use in treating patients with conditions ranging from arthritis to HIV." --Sue De Pasquale
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