Magazine

Introduction


Thousands of researchers gathered in Austin, Tex., for the American Physical Society's annual March meeting. Some 5,500 talks were given, and two subjects stood out: biology and solid-state physics. Senior writer Otis Port was there and filed this report. The interplay between biology and physics was clear throughout the week-long American Physical Society meeting in Austin. On day one, Harvard University's Daniel Branton talked about new porous materials that can classify DNA strands as they move through nano-size holes, and several interdisciplinary teams presented the latest insights into the physics of protein action. After midweek discussions of RNA's role in evolution, the final day took on biomedical physics and neurobiology.

New imaging technology was a hot topic. Massachusetts General Hospital and General Electric are evaluating an improved method to spot breast cancer, using "tomosynthesis." This technique creates three-dimensional, digital X-ray pictures. After reviewing results from the first 200-odd patients, radiologists are optimistic that 3-D images will help them find the 10% to 20% of tumors now missed because they are masked in 2-D images by other breast tissue.

To watch biology in action, the National Institutes of Health has formed a multinational team that is producing high-speed movies of proteins performing their life-sustaining tasks. Each frame depicts a mere 150 quadrillionths of a second (femtoseconds) of a protein's work. And University of California at Berkeley researchers are using laser strobes to make 100-femtosecond images for studying how beta carotene harvests light for energy in plants. It's getting tougher and tougher to shrink semiconductor components so as to double computer power every 18 months, as "required" by Moore's Law. In a decade or so, today's transistors may reach the point where no further reduction is possible. So what comes next?

Spintronics and moletronics, probably. The former entails storing a data bit by changing the direction of a single electron's spin. The challenge is how to exert such precise control. In Austin, most researchers talked about using a magnetic field to flip spin directions. That's fine in the laboratory. For commercial circuits, though, it would mean basic changes in computer design. But a team from University of California at Santa Barbara and University of Pittsburgh reports it can switch spins with electronic signals like those used to control today's disk drives. So spintronics could spin out of the lab sooner than anyone had expected.

As for moletronics -- using molecules as transistors -- various approaches were discussed, and one group is constructing working moletronic circuits. Headed by IBM's Donald M. Eigler, who in 1989 lined up 35 atoms to spell "IBM," the team arranges carbon-monoxide molecules so they execute logic functions via physical interactions, like billiard balls. The circuitry is so teensy that it skips over four decades of Moore's Law. Three years ago, physicists with the University of California at San Diego startled the scientific world by constructing a composite material that's flat yet focuses radio waves. The usual dish-antenna shape isn't needed because the material bends certain electromagnetic waves in the opposite direction of all other materials. Many researchers have since joined the effort to probe the strange properties of such "left-handed lenses."

Collaborators at Harvard University and Massachusetts Institute of Technology shot a microwave beam into a flat slab. The beam didn't emerge slightly wider, as it ordinarily would. Instead, a tiny microwave spotlight popped out, suggesting that beams could be focused to finer points than possible with existing lenses.

Other teams are using computer models to explore the potential of left-handed optics and even semiconductors. Calculations by researchers at Australian National University and University of Utah point to peculiar optical effects. The Utah crew predicts that left-handed optical lenses would create a series of internal reflections not found in ordinary lenses. Assembling the reflections may provide a new approach to three-dimensional imaging and displays. Also, a Naval Research Laboratory group is working on left-handed materials for electronic circuits. Team member Clifford M. Krowne says the research has uncovered unique physics features, unknown until now, that might yield new types of chip components -- if left-handed materials compatible with silicon can be developed. -- Comic books are no laughing matter for University of Minnesota physics students. James Kakalios teaches a freshman course that uses superhero exploits to drive home lessons. For example, if Spider-Man's silk were as strong as that of a spider, it really would enable him to swing between skyscrapers.

-- Keeping chips cool is becoming a major headache. Transistors generate heat, and packing more of them onto chips is producing silicon hot plates. Stanford University researcher Thomas Kenny reported experimental success with "thermionic" cooling, which harnesses the phenomenon of tunneling -- electrons burrowing through matter -- to bleed off heat. But real-world chips are a long way off.


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