Number 267 (Story #2), April 23, 1996 by Phillip F. Schewe and Ben Stein COLLECTIVE SYNCHRONIZATION CAN ACT LIKE A PHASE TRANSITION. Several systems with large populations exhibit a coordinated ensemble behavior. For example, fireflies can flash in unison, crickets can chirp together, and pacemaker cells in the heart work together. Theorists, such as Yoshiki Kuramoto of the University of Kyoto (Japan), have supposed for some time that the onset of synchronization would be equivalent to a phase transition, like the transformation of water into ice, and have worked out formulas to deal with the problem. (Science News, 13 April 1996.) Now, physicists at Georgia Tech and Cornell have performed experimental studies of large series arrays of nonidentical Josephson junctions which bear out the models. As the input current was varied, the array showed two phase transitions, one in which the voltage oscillations of the junctions became partially synchronized, and a second in which the frequency coupling became complete. Normally, the junctions, which are all slightly different, would oscillate at their own natural frequencies. The researchers plan next to test two-dimensional arrays. (Kurt Wiesenfeld et al., Physical Review Letters, 15 January 1996.)