1. CNRS, Univ. Bordeaux, Centre de Recherche Paul Pascal, UMR 5031, 115 Avenue Schweitzer, 33600 Pessac, France
2. Univ. Bordeaux, CNRS, Bordeaux INP, LCPO, UMR 5629, F-33600 Pessac, France
3. Department of Chemical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K.