[1] Nat Univ Trieste, Ist Nazl Fis Mat, Trieste, Italy
[2] Nat Univ Trieste, Dipartimento Mat Risorse, Trieste, Italy
[3] Univ Cambridge, Elect Engn Div, Dept Engn, Cambridge CB3 0FA, England
[4] Univ Amsterdam, Dept Chem & Pharmaceut Sci, NL-1012 WX Amsterdam, Netherlands
[5] Univ Karlsruhe, Inst Zuverlassigkeit Bauteilen & Systemen, Karlsruhe, Germany
[6] Fraunhofer Inst Werkstoffmech IWM, Freiburg, Germany
[7] Kings Coll London, Dept Phys, London WC2R 2LS, England