[1] Phys Tech Bundesanstalt, Semicond Grp, D-35032 Braunschweig, Germany
[2] Phys Tech Bundesanstalt, Electromagnet Fields Grp, D-35032 Braunschweig, Germany
[3] Phys Tech Bundesanstalt, Working Grp High Frequency Measurement Tech, D-35032 Braunschweig, Germany
[4] Univ Marburg, Dept Phys, D-35032 Marburg, Germany
[5] Helmholtz Ctr Infect Res, D-38124 Braunschweig, Germany
[6] Univ Wurzburg, Inst Pharmakol & Toxikol, D-97078 Wurzburg, Germany