1. Graduate Student Research Assistant, Univ. of Michigan, School of Natural Resources and Environment, Center for Sustainable Systems, Dana Building, 440 Church Street, Ann Arbor, MI 48109, US, e-mail: arbucklepw@yahoo.com
2. Assistant Professor, Stanford Univ., Department of Civil and Environmental Engineering, 285B Yang and Yamazaki Energy and Environment Building, 473 Via Ortega, Stanford, CA 94305, US, e-mail: mlepech@stanford.edu
3. Professor, Univ. of Michigan, School of Natural Resources and Environment and Civil and Environmental Engineering Department, and Co-Director of the Center for Sustainable Systems, 440 Church Street, Ann Arbor, MI 48109, US, e-mail: gregak@umich.edu