The 1985 joint Cryogenic Engineering/International Cryogenic Materi als Conference was held on the campus of the Massachusetts Institute of Technology, Cambridge, Massachusetts. About 350 papers were presented at the joint conference on a wide variety of topics in cryogenic science and engineering. This volume of Advances in cryogenic Eogineerlng, the thirty-first in the series which began in 1954, contains most of the papers which were presented at the 1985 Cryogenic Engineering Conference. Each paper was rigorously peer reviewed to maintain the international reputation of Advances as the premier archival publication in the field of cryoscience, engineering, and technology. All the papers published in Volume 31 contain an abstract. A copy of the book will be sent to all maj or abstracting services, which should improve retrieval of the information contained in the published papers. I would like to thank the authors and those who served as reviewers. I especially appreciate the assistance of my colleague M. E. Stone who edited some of the papers for this volume. Terry Gutierrez was invaluable in preparing the manuscripts for publication, and I thank her. xvii DEDICATION Dr. Samuel C. Collins, Professor Emeritus of the Massachusetts Institute of Technology, internationally known as the father of practical helium liquefiers and founder of the MIT Cryogenic Engineering Laboratory, died on June 19, 1984, in George Washington University Hospital, Washington, DC."