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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.
---
(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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