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August 13, 1999

For more information on these science news and feature story tips, please contact the public information officer at the end of each item at (703) 292-8070. Editor: Cheryl Dybas

SCIENTISTS USE NOISE TO SORT PROTEINS

Two National Science Foundation (NSF)-funded scientists have invented a device that could simplify the study of cells by isolating the molecules that inhabit cell walls. The unusual apparatus harnesses thermal noise to drive the sorting process, rather than relying on conventional energy sources.

"The ability to separate membrane-associated molecules is extremely important," says chemist Steven Boxer of California’s Stanford University, "because they play a vital role in the life of the cell and have proven exceptionally difficult to purify, characterize and study."

Boxer and colleague Alexander van Oudenaarden developed the new sorting system, and report on its design and operation in the August 13 issue of the journal Science. Unlike conventional separation techniques, the new system can separate membrane molecules in their native environment and do so continuously, rather than in batches. Because it relies on fabrication techniques developed in the microelectronics industry, the device should be inexpensive to manufacture in volume and relatively simple to modify for specific purposes, Boxer says. [Cheryl Dybas]

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LIGO PROTOTYPE USED TO SEARCH FOR GRAVITATIONAL WAVES

In 1918, Albert Einstein predicted the existence of gravitational waves in his general theory of relativity, but so far, scientists have only found indirect evidence of their existence. The future NSF-funded Laser Interferometer Gravitational-wave Observatory (LIGO) will be one of the most sensitive instruments ever designed to directly detect gravitational waves reaching the earth from outer space.

In LIGO, laser beams travelling between mirrors inside 4-kilometer vacuum tubes will be slightly offset when the mirrors are hit with gravitational waves. These instruments will be able to measure displacements smaller in size than the diameter of a proton.

Researchers recently analyzed data obtained with a small (40-meter-long vacuum tubes) LIGO prototype at the California Institute of Technology. They will publish their findings in the August 23 Physical Review Letters. The scientists looked for gravitational-wave "chirps" emitted by binary neutron stars within our galaxy -- two stars spiraling together and coalescing at the end of their lives. The team was able to determine an upper limit for the rate of such events occurring within our galaxy no more than once every two hours. Future LIGO detectors should be able to detect similar events that have occurred in far away galaxies, at rates as infrequent as once every million years.

Construction of the LIGO detectors at Hanford, Washington, and Livingston, Louisiana, is almost complete; they are expected to be operational by the end of 2001. [Amber Jones]

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MALE/FEMALE SALARY GAPS IN ENGINEERING LESS THAN IN MANY OTHER OCCUPATIONS

Recent studies have found that in the United States, women earn as little as 71-74 cents on every dollar earned by men. This is not quite the case in the engineering profession, says a newly published NSF Issue Brief, which asks in its title, "How Large is the Gap in Salaries of Male and Female Engineers?"

In engineering, the salary gap was as small as 13 percent in 1995, based upon an NSF survey covering employed full-time engineers, which included 1.5 million college graduates of all ages in 16 engineering occupations. Controlling for years of experience and other variables in a process called multivariate regression analysis, the gender gap in salaries actually shrinks to as little as three percent or less.

The brief also noted that unmeasured factors like time out of the workplace might help explain the remaining 2-3 percent of the difference not explained by the studied variables. [Bill Noxon]

For the entire issue brief, see: http://www.nsf.gov/sbe/srs/issuebrf/ib99352.htm

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