George E. Totten is President of G. E. Totten & Associates, Inc., Seattle, Washington. The coeditor of the Steel Heat Treatment Handbook and editor of the Handbook of Hydraulic Fluid Technology (both titles, Marcel Dekker, Inc.), as well as the author or coauthor of approximately 350 professional publications on hydraulics, lubrication, quenching and heat treatment, Dr. Totten is a Fellow of ASM International and a member of the American Chemical Society, SAE International, and the American Society for Testing and Materials, among other professional organizations. He received the B.S. and M.S. degrees from Fairleigh Dickinson University, Teaneck, New Jersey and the Ph.D. degree from New York University, New York. D. Scott MacKenzie is Technical Specialist, Heat Treating Products, Houghton International Incorporated, Valley Forge, Pennsylvania. Formerly Dr. MacKenzie was equipment and process engineer, The Boeing Company, St. Louis, Missouri, responsible for equipment, processes, maintenance and training for all aluminum steel and titanium heat treating. The author or coauthor of numerous publications in atmosphere control, quenching and aluminum heat treatment, he is a member of ASM International. He received the B.S. degree (1981) from The Ohio State University, Columbus and the M.S. (1995) and Ph.D. (2000) degrees in metallurgical engineering from the University of Missouri-Rolla.