Journal article: Available to journalists on request
3) What do ice crystals in Greenland have in common with the building blocks of proteins?
J. Ferkinghoff-Borg et al.
Physical Review Letters (to appear)
The size of ice crystals in the Greenland ice sheet and the length of alpha-helices in proteins, two seemingly very different phenomena, are actually both incidences of the same physical processes of diffusion and fragmentation, according to a new paper. Structures like crystals and the building blocks of proteins gradually grow and shrink randomly due to diffusion, which tends to make the largest chunks even larger.
But these structures may break abruptly due to stresses. Combining these two competing processes, the authors derive an equation for the size distribution of fragments, and show that it fits experimental data for both of these very different systems. Many other natural phenomena could also be described by the same processes.
Journal article: Available to journalists on request
4) Air bubbles slow sound waves in water.
A. Krokhin, J. Arriaga, and L. Gumen
Physical Review Letters (to appear)
The speed of sound in water drops sharply with inclusion of just a few small air bubbles, according to a new calculation. Being able to calculate the speed of sound in air-water mixtures is critical for meteorology, oceanography, and air and sea navigation. The paper derives the first exact formula for the speed of sound in any mixture of air and water. Previously only approximations were available, which were inaccurate at higher concentrations of air. In pure water, sound travels about five times as fast as it does in pure air. Just a small amount of air added to water dramatically slows sound waves. But when the air bubbles get big enough to touch each other, sound can propagate through them, and the speed rises somewhat. For the revers
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Contact: David Harris
harris@aps.org
301-209-3238
American Physical Society
17-Nov-2003