1. CREPEC, Dept. of Chemical Engineering; Polytechnique Montréal; P.O. Box 6079, Station Centre-Ville Montréal Québec Canada H3C 3A7
2. Dept. of Microbiology, Infectiology and Immunology, Pavillon Roger-Gaudry; Univ. de Montréal; P.O. Box 6128, Station Centre-ville Montréal Québec Canada H3C 3J7