1. Laboratory of Geophysical and Industrial Flows, Grenoble University, UJF-INPG-CNRS BP 53X, 38041 Grenoble Cedex 9, France and Centre de Recherches sur les Très Basses Températures, CNRS B.P. 166, 38042 Grenoble Cedex 09, France
2. Laboratory of Geophysical and Industrial Flows, Grenoble University, UJF-INPG-CNRS, BP 53X, 38041 Grenoble Cedex 9, France