1. Department of Chemical Engineering (0211), Virginia Polytechnic Institute & State University, Blacksburg, Virginia 24061, Departamento de Engenharia Quimica, Instituto Militar de Engenharia, Rio de Janeiro, RJ, 22290-270 Brasil, and Departamento de Fisica, Universidad Nacional de la Plata and IFILP (CONICET), CC/67-1900 La Plata, Argentina