Controlled pulse reversal on a ring electrode

Oscillatory rotating activation pulses on a Pt ring electrode during formic acid oxidation were externally perturbed via a trigger electrode at one lo cation of the ring. While usual phase resetting was obtained for small pert urbation amplitudes, stronger perturbations resulted in reversal of the dir ection of pulse motion when applied behind the pulse over a wide phase inte rval. The results are in agreement with simulations carried out with a reac tion-migration model and can be rationalized in terms of short-range positi ve and long-range negative coupling. (C) 2001 Elsevier Science. B.V. All ri ghts reserved.