1. IFW Dresden, P.O. Box 270116, D-01171 Dresden, Germany
2. Siemens Healthcare GmbH, Technology Centre, Guenther-Scharowsky-Strasse 1, 91058 Erlangen, Germany
3. Erich Schmid Institute of Materials Science, Austrian Academy of Sciences, Jahnstrasse 12, A-8700 Leoben, Austria
4. Department Materials Physics, Montanuniversität Leoben, Jahnstraße 12, A-8700 Leoben, Austria