1. School of Biological and Chemical Sciences, The University of Newcastle, Callaghan, N.S.W., 2308 Australia; Centre for Multiphase Processes, The University of Newcastle, Callaghan, N.S.W., 2308 Australia; School of Chemistry, Physics and Environmental Science, University of Sussex, Falmer, Brighton BN1 9QJ, UK; and Unilever Research, Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral CH63 3JW, UK