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Cool Air: A Sound Approach


Developments to Watch

COOL AIR: A SOUND APPROACH

COMPRESSORS ARE THE UNGAINLY guts of air conditioners, refrigerators, and industrial cooling systems. Because pistons, crankshafts, and other moving parts are essential, compressors guzzle electricity while pumping refrigerants through cooling pipes. But not for long, if MacroSonix Corp. in Richmond, Va., has its way. President Tim S. Lucas has invented an energy-stingy compressor that requires no moving parts. He recently showed a prototype to a meeting of acoustical engineers in San Diego.

The compressor's secret: superpowerful sound waves. Energy transmitted by sound is already used by ultrasonic welding to melt plastics. Beyond a certain amplitude, though, sound energy dissipates as shock waves. Lucas discovered he could thwart this dissipation by precisely shaping the sound waves inside special containers called resonators. These can generate sound waves that pack 1,600 times more energy than ever before and can create pressures reaching 500 pounds per square inch. "It's one of the most exciting things to come along in acoustics in several years," says Gregory W. Swift, an acoustics expert at Los Alamos National Laboratory.EDITED BY OTIS PORT Neil GrossReturn to top

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FLATLAND: THE FINAL FRONTIER?

A PROJECT CALLED CHeX IS about as close as you can get to the mythical Flatland, a world with only two dimensions. CHeX stands for Confined Helium Experiment, conducted aboard the Space Shuttle Columbia. One purpose, says John A. Lipa, the Stanford University physicist who heads CHeX, is to help determine how small chips can get before quantum effects force the semiconductor industry to spend gigabucks harnessing the woolly world of quantum physics.

Blame it on two-faced electrons. Usually they behave like particles, but sometimes like waves. The latter occurs in flatland circuits, where lines aren't much bigger than electron waves. Confine electrons that tightly, and the conductivity of metals and semiconductors plunges.

There are three theories to explain this, but little direct evidence. That's where helium comes in. It is the only substance whose atoms don't become immobile even at absolute zero. In fact, at roughly -456F, helium becomes a "superfluid" with no resistance to electron flow. The size of the so-called confinement effect then increases 10,000 times, becoming big enough to measure directly. The results should help show which of the three theories provides the most accurate prediction.EDITED BY OTIS PORTReturn to top

SOLVE THIS RIDDLE AND WIN $50,000

MOST PEOPLE STOP THINKING ABOUT MATH PROBLEMS when they finish school. Not Andrew Beal, founder of Beal Bank in Dallas. His hobby is number theory, and he's so excited by a recent insight that he'll pay up to $50,000 to anyone who can validate his discovery.

Beal's challenge relates to Pierre de Fermat's famous last theorem, an arcane proposition that defied solution for three centuries until Princeton University mathematician Andrew J. Wiles licked it a few years ago. To spur a speedier resolution to his conjecture, Beal is offering $5,000, and will increase it by $5,000 a year up to $50,000, to the first person to prove or disprove this:

If A, B, C, x, y, and z are positive whole numbers, x, y, and z are greater than 2, and Ax+ By = Cz, then A, B, and C have a common factor. (Fermat's theorem is more restrictive, with the exponents x, y, and z being identical.) For example, in 36 + 183 = 38, all the numbers have 3 as a factor.

Beal has already shown his conjecture holds for exponents as large as 100, but he hasn't been able to formulate a proof. A committee of mathematicians, headed by R. Daniel Mauldin of the University of North Texas, will oversee Beal's contest.EDITED BY OTIS PORT Elizabeth VeomettReturn to top


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