[1] Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, CZ-121 16 Prague 2, Czech Republic
[2] Zentrum Funktionswerkstoffe gGmbH, Sachsenweg 8, D-38678 Clausthal-Zellerfeld, Germany
[3] Inst. Werkstoffkunde/Werkstofftech., TU Clausthal, Agricolastr. 6, D-38678 Clausthal-Zellerfeld, Germany