1. Martin-Luther-University Halle-Wittenberg, Center of Engineering Sciences; D-06099 Halle/Saale Germany
2. University of Rostock, Institute of Physics; Wismarsche Str. 43-45 18051 Rostock Germany
3. Consiglio Nazionale delle Ricerche, Istituto per i Polimeri, Compositi e Biomateriali - c/o Comprensorio Olivetti - Via Campi Flegrei; 34 - 80078 Pozzuoli (NA) Italy