1. Escuela de Ingeniería Química, Universidad de Los Andes, Mérida, Venezuela, Graduate School of Environment and Information Sciences, Yokohama National University, Tokiwadai 79-7, Hodogaya-ku, Yokohama 240-8501, Japan, and Materials Development Research Laboratories, Kao Corporation, 1334, Minato, Wakayama-shi, Wakayama 640-8580, Japan