1. Department of Chemistry, University of Washington, Seattle, Washington 98195
2. Stanford Synchrotron Radiation Lightsource, 2575 Sand Hill Road, Menlo Park, California 94025
3. Department of Environmental Science, Policy and Management, University of California, Berkeley, California 94720-3114
4. Division of Environmental and Biomolecular Systems, Oregon Health & Science University, 20000 NW Walker Road, Beaverton, Oregon 97006