1. Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Straße 24/25, 14476 Potsdam, Germany
2. Ambrosys GmbH, David-Gilly Straße 1, 14469 Potsdam, Germany
3. Department of Applied Mathematics, University of Washington, Seattle, Washington 98195, USA
4. Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195, USA