1. Department of Chemical and Processing Engineering; University of Genoa; via Balbi, 5 16126 Cedex 05 Italy
2. Department of Physics; “Al. I. Cuza” University of Iasi; Carol I Blvd., 11A 700506 Romania
3. UPMC; Univ Paris 06, UMR 7197, LRS, Le Raphaël, 3 rue Galilée 94200 Ivry France
4. CNRS; Univ Paris 06, UMR 7070, LM2N, bât. F, B.P. 52, 4 place Jussieu Paris F-75231 Cedex 05 France