1. Institut für Theoretische Physik, Westfälische Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 9, 48149 Münster, Germany
2. Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK
3. Interdisciplinary Centre for Mathematical Modelling, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK
4. Center for Nonlinear Science (CeNoS), Westfälische Wilhelms-Universität Münster, Corrensstr. 2, 48149 Münster, Germany
5. Department of Physics, University of California, Berkeley, California 94720, USA