1 Aachen University of Applied Sciences, Institute of Bioengineering, Heinrich-Mußmann-Str. 1, 52428 Jülich, Germany.
2 Medical University of Graz, Institute of Biophysics, Neue Stiftingtalstr. 6 (MC1.D.)/IV A, 8010 Graz, Austria. Electronic address: wolfram.mueller@medunigraz.at.