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U.Va. Engineering Researchers Confirm 25-Year-Old TheoryThat Groups Seek Unison

May 31, 2002-- Unison is the harmony that nature loves best.

When crickets chirp, or fireflies flash their lights, or a frenzied audience of pre-teen girls applauds the latest boy band, the action starts as a collection of individuals but ends as a group — chirping, flashing or clapping — acting together.

These interactions among individuals lead to group dynamics known as synchrony. A theory explaining how synchronization emerges was developed 25 years ago but never validated in a laboratory setting. Until now.

In today’s [May 31] issue of the journal Science, three chemical engineers at the University of Virginia describe the results of experiments they designed to confirm the theory of synchronization that scholars Arthur Winfree and Yoshiki Kuramoto conceived in the 1970s.

"We used chemistry as a platform to study this phenomenon, which occurs in many different scientific fields, including biology, physics and ecology," said Jack Hudson, the Wills Johnson Professor of Chemical Engineering at U.Va.’s School of Engineering and Applied Science, who heads the research team.

The researchers -- including chemical engineering post-doc Istvan Kiss and doctoral candidate Yumei Zhai — studied the onset of synchrony by observing a series of electrochemical reactions. They plunged the tips of 64 wires made of nickel into a beaker of sulfuric acid. Then they plugged the other ends into a power source, turned on the power and recorded the results.

What they found was that, because of interactions among the 64 electrodes, a group of the metal tips began reacting simultaneously. And as the interactions grew stronger, the remaining points joined in as well. (Imagine a fight on the playground attracting first a cluster of children and then everyone, including the principal, once it becomes clear what is going on.)

In the lab, the pace of the chemical reaction on each metal tip was illustrated by a wavy, or oscillating, line on an oscilloscope. Initially, the 64 waves differed slightly in their length, depth and height. But over time — the experiments ran for about three minutes -- the waves began to coincide. Synchrony had been achieved.

"We used a quantitative measure to determine how much order there is in a group of reactions in a system and to show how the strength of interactions influences this order," Hudson said.

Through their work, the U.Va. researchers found that Winfree and Kuramoto’s theory predicting the onset of synchronization in oscillators covers more ground than the theorists had imagined. Varying the experiments, the U.Va. team found that the theory holds true not only for regular reactions, but also for irregular, so-called chaotic reactions.

Hudson believes his team’s work will have an impact on research in many different fields and in the development of more powerful lasers and microwaves for communications.

Contact: Charlotte Crystal, (434) 924-6858

FOR ADDITIONAL INFORMATION: Contact the Office of University Relations at (434) 924-7116. Television reporters should contact the TV News Office at (434) 924-7550.

SOURCE: U.Va. News Services


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