1. Polymers and Complex Fluids, School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK; Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802; Imaging Materials and Media, Research and Development, Eastman Kodak Company, Rochester, New York 14650-2116; Institut für Festkörperforschung, Forschungszentrum Jülich, D-52425 Jülich, Germany; and Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX, UK