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October 2, 2002
Stories
of modern science ... from UPI 
By Ellen Beck
United Press
International
DOPPLER DURING SURGERY
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.
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MIT MODEL PREDICTS DEFECTS
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.
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EFFICIENTLY
MANAGING BROADBAND
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.
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LAND USE HAS BIG EFFECT ON CLIMATE
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.
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(EDITORS: For more information about DOPPLER,
contact Richard Merritt at 919-684-4148 or e-mail merri006@mc.duke.edu. For
DEFECTS, contact Elizabeth Thomson at 617-258-5402 or thomson@mit.edu, for
BROADBAND, Barbara Hale, 814-865-9481 or bah@psu.edu, and for LANDUSE,
Krishna Ramanujan 301-286-3026 or Kramanuj@pop900.gsfc.nasa.gov)
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