9705810 Baygents The International Research Fellow Awards Program enables U.S. scientists and engineers to conduct three to twenty - four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a nine-month postdoctoral research visit by Dr. James C. Baygents of the University of Arizona to work with Dr. Robert J. Hunter at the University of Sydney in Australia. Support for this project will be provided by the U.S.-Australia Program of the Division of International Programs. This project will work to describe the dynamics of colloidal particles in applied electric fields that vary with position and time. Equipped with a proper theoretical description of the particle dynamics, one can then interpret the results of experimental measurements on nonlinear electrokinetic effects. Electroacoustics is a procedure in which one applies an alternating electric field to a colloidal suspension. Since most colloid particles are electrically charged, they respond to this field by oscillating backwards and forwards at the same frequency as the applied field. This generates a sound wave, and it is by measuring the properties of the sound wave that it is possible to obtain a detailed characterization of the colloid particles. Current theory assumes that the applied field strengths are so low that the particle response is linear. Dr. Baygent's research will extend the theories of these effects to take into account the non-linear effects which would result if the field strength is raised to much higher levels. Sufficiently high fields should be able to orient the particles along the direction of the field and this would cause them to respond differently to an unoriented particle. This added information could be used to obtain the charge and size of the particles as well as their aspect ratio (length to diameter) if they are non-spherical. ***
