Rhodes for his unceasing efforts of guidance and support throughout my graduate study. Acknowledgment is also made to Merck, Sharp and Dahme Research Laboratories, West Point, Pennsylvania, for the opportunity to work as a research associate during the period of June to August, 1978. Special thanks is due Dr. Joseph B. Schwartz for his guidance, both in Pennsylvania and in Rhode Island. I also wish to acknowledge the help of Rao N. Chilamkurty for his technical assistance, R. Scott McKenzie for his editorial comments, and Beth Richardson for her warmth, personal support and friendship.