Magazine article Science News

Added Noise Keeps Waves Going

Magazine article Science News

Added Noise Keeps Waves Going

Article excerpt

Usually a nuisance, noise sometimes aids the transmission of a signal.

Researchers have now demonstrated in the laboratory that random fluctuations in the concentration of a chemical across a surface can enhance the propagation of waves of another chemical's activity in a thin gel. "Noise actually helps," says chemist Kenneth Showalter of West Virginia University in Morgantown.

Showalter and his coworkers Sandor Kadar and Jichang Wang report their results in the Feb. 19 Nature.

The observation of enhanced wave propagation in a chemical medium represents a new avenue in the study of a phenomenon called stochastic resonance (SN: 2/23/91, p. 127), in which the addition of noise can boost a weak signal to detectable levels.

"This is the first experimental demonstration of stochastic resonance that occurs in a system spread over a surface [and changing with time]," says Frank Moss of the Center for Neurodynamics at the University of Missouri-St. Louis. The findings also provide a model of how internal noise may sustain long-range chemical waves in networks of brain cells (SN: 11/23/96, p. 330).

Showalter and his coworkers studied a photosensitive version of a chemical system known as the Belousov-Zhabotinsky reaction, in which rising and falling chemical concentrations appear as visible waves traveling through a thin layer of silica gel. Shining light on the gel produces a chemical that quenches wave propagation.

The researchers initially adjusted the light intensity to suppress wave activity. They then replaced that uniform illumination with a grid in which intensity varied from cell to cell and from time to time in each cell, yet maintained an average intensity across the grid that inhibited activity. …

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