Institution: | (1) Condensed Matter Theory Group, Blackett Laboratory, Imperial College, London SW7 2BZ, UK, GB;(2) Physico-Chimie Théorique, ESA CNRS 7083, E.S.P.C.I., 75231 Paris Cedex 05, France, FR;(3) Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany, DE |