Program, sponsored this report (no. S93-058), as required by Naval School of Health Sciences, Bethesda, Instruction (NSHSBETHINST) 6000.41B. The views expressed in this article are those of the authors and do not reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government. This statement is required by Air Force Instruction (AFI) 40-402 in reports of research involving humans: "The voluntary fully informed consent of the subjects used in this research was obtained as required by 32 Code of Federal Regulations (CFR) 219 and AFI 40-402.