1. Departamento de Química, Universidade de Coimbra, 3004-535 Coimbra, Portugal; Physical Chemistry 1, Center for Chemistry and Chemical Engineering, P.O. Box 124, 221 00 Lund, Sweden; and Unilever Research Laboratorium, Olivier van Noortlaan 120, P.O. Box 114, 3130 AC Vlaardingen, The Netherlands