1. U.S. Geological Survey, Box 25046, MS 973, Denver Federal Center, Denver,
Colorado 80225-0046, United States
2. U.S. Geological Survey, 345 Middlefield Road, Building 15, MS 496, Menlo
Park, California 94025-3561, United States
3. Stanford Synchrotron Radiation Lightsource, 2525 Sand Hill Rd, MS 69, Menlo
Park, California 94025, United States