October 2, 2002

Stories of modern science ... from UPI
By Ellen Beck
United Press International


Top Stories

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     Using Doppler technology during major surgery can reduce hospital stays and help patients recover faster. Duke University anesthesiologists say a Doppler technique of using reflected sound waves to measure the heart's pumping action can better guide the use of fluids and plasma during surgery. By not allowing fluid levels to drop below normal, a common surgery occurrence, proper intestine function is maintained and patients have less postoperative nausea and vomiting. Blood, plasma or synthetic plasma expanders are given during surgery in response to changes in blood pressure, urine output or heart rate, but with an esophageal Doppler monitor, a continuous reading of cardiac output is produced so the anesthesiologist knows how to keep fluids at normal levels. The EDM includes a small ultrasound probe put down the esophagus to a site near the aorta, the main heart artery. By measuring the reflection of sound waves directed into the aorta, the EDM measures the volume of blood pumped out of the heart and to the body.
     Massachusetts Institute of Technology engineers can predict where a defect in a material will happen, its initial features and how it will advance. Cracks and other defects can cause minor to major mishaps -- from malfunctioning microchips to earthquakes. "There has been much past work on defects in materials, but no one has really explained how a crack or void nucleates in the first place," says MIT's Subra Suresh. The model uses key features observed in experiments and is based on many years of theory and experiments by numerous researchers. The model could be especially useful in nanotechnology, where a minuscule dislocation -- a disorder in the arrangement of atoms inside a material -- or a crack can drastically compromise the performance of a device.
     A new allocation technique developed by Pennsylvania State University engineers allows more efficient management of the radio spectrum and prevents interference on wireless broadband systems for high-speed Internet access. The goal is to potentially bringing down costs for consumers. Mohsen Kavehrad of Penn State says quality service could be provided to more homes using only a limited span of the radio spectrum. More customers on the available bandwidth translate into lower costs. Wireless local loops need software and hardware to help the network respond to changes in traffic while ensuring every hertz in the available spectrum is used efficiently. The engineers developed software that allows the subscriber signal whose direction of arrival is subjected to fewer interferers to be processed ahead of ones experiencing the most interference. In other words, the new strategy allows avoiding strong co-channel interference by sequencing the processing of the signals according to the amount of interference they are experiencing.

     It's not just greenhouse gases that affect global climate. Researchers say human-caused land use changes are another important factor. Urban sprawl, deforestation, reforestation, agricultural and irrigation have a big effect on regional surface temperatures, precipitation and larger-scale atmospheric circulation. In some areas, such as North America, Europe and southeast Asia, the impact is even greater than greenhouse gases. "Through landcover changes over the last 300 years, we may have already altered the climate more than would occur associated with the radiative effect of a doubling of carbon dioxide," says Roger Pielke Sr., an atmospheric scientist at Colorado State University and lead author. The researchers also suggest using a new method for comparing different human-influenced agents of climate change in terms of the redistribution of heat over land and in the atmosphere.
     (EDITORS: For more information about DOPPLER, contact Richard Merritt at 919-684-4148 or e-mail For DEFECTS, contact Elizabeth Thomson at 617-258-5402 or, for BROADBAND, Barbara Hale, 814-865-9481 or, and for LANDUSE, Krishna Ramanujan 301-286-3026 or

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