1. Max Planck Institute for Dynamics and Self-Organization, Am Fassberg 17, D-37077 Göttingen, Germany
2. Lewis & Clark College, Portland, Oregon, USA
3. Institute for Dynamics of Complex Systems, University of Göttingen, Göttingen 37077, Germany
4. Laboratory of Atomic and Solid-State Physics and Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, New York 14853, USA
5. Univ Lyon, Ecole Normale Superieure de Lyon, CNRS, Laboratoire de Physique, F-69342 Lyon, France