1. Hashimoto Polymer Phasing Project, ERATO, JST, Keihan-na Plaza, 1-7 Hikari-dai, Seika, Kyoto 619-02, Japan, and Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 606-01, Japan, and Applied Mathematics Department, Research School of Physical Sciences, Australian National University, Canberra 0200, Australia