[1] Univ Grenoble 1, Lab Plastes & Differenciat Cellulaire, CNRS, F-38041 Grenoble 9, France
[2] European Synchrotron Radiat Facil, F-38043 Grenoble, France
[3] Univ Grenoble 1, Lab Louis Neel, CNRS, Inst Natl Polytech Grenoble, F-38042 Grenoble, France