1. School of Chemical, Biological and Environmental Engineering, Oregon State Univ.; Corvallis OR 97331
2. Dep. of Geophysical Sciences and Center for Advanced Radiation Sources, Univ. of Chicago; Chicago IL 60637
3. Earth and Environmental Sciences Division, Los Alamos National Laboratory; Los Alamos NM 87544
4. Institut de Mecanique des Fluides de Toulouse, Univ. of Toulouse; France