1. Theory of Polymers and Soft Matter, Department of Applied Physics, Technische Universiteit Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
2. Dutch Polymer Institute, P.O. Box 902, 5600 AX Eindhoven, The Netherlands
3. Department of Physics, San Diego State University, San Diego, California 92182, United States
4. Institute of Mathematical Problems of Biology, Pushchino 142290, Russia