1. Fraunhofer Institute for Physical Measurement Techniques (IPM), Heidenhofstr. 8, D-79110 Freiburg, Germany (A.L., T.B.); Roche Diagnostics GmbH, Sandhofer Str. 116, D-68305 Mannheim, Germany (K.H., R.M., W.P.); and Faculty of Physics and Astronomy, University of Heidelberg, D-69122 Heidelberg, Germany (W.P.)