1. Postdoctoral Researcher, Dept. of Radiology, Center for Multimodal Imaging and Genetics, 9452 Medical Center Dr., FL 4W 106, Univ. of California, San Diego, La Jolla, CA 92037-1337.
2. Assistant Professor, Dept. of Civil Engineering, Johns Hopkins Univ., 3400 N. Charles St., Baltimore, MD 21218 (corresponding author).