Any study on the historical evolution of nations and countries points out the decisive importance of productivity trends. We are all very familiar with the main evolution which started with a hunting society at the dawn of civilization, then moved to an agricultural society, and quickly to craftsmanship and com merce. The beginning of the industrial society dates back to the end of the eighteenth century in England, with the introduction of the assembly line in the textile and smelting industries. However, in the last few decades, we are becoming more and more acutely aware of the paramount importance of the production of "information". Indeed, according to a few economists today, we should be classified as living in an information society which has superseded the industrial society. At this point it simply becomes necessary to talk about the computer informa tion industry, which is more and more pervading our lives, from the personal computer, to the workstation, to information networks and electronic mail, to the blueprint executed by robots, to the supercomputer necessary in any major scientific and engineering task. The computer has already brought about a momentous change in the production line - less and less man-size, more and more robot-size. But this rush to tech nical innovation has not stopped at this point. Artificial intelligence and expert systems are becoming a more and more important factor for production by many enterprises and activities.

This volume collects a number of the invited lectures and a few selected contrib utions presented at the International Symposium on Structure and Dynamics of Nucleic Acids, Proteins and Membranes held August 31st through September 5th, 1986, in Riva del Garda, Italy. The title of the conference as well as a number of the topics covered represent a continuation of two previous conferences, the first held in 1982 at the University of California in San Diego, and the second in 1984 in Rome at the Accademia dei Lincei. These two earlier conferences have been documented in Structure and Dynamics: Nucleic Acids and Proteins, edited by E. Clementi and R. H. Sarma, Adenine Press, New York, 1983, and Structure and Motion: Membranes, Nucleic Acids and Proteins, edited by E. Clementi, G. Corongiu, M. H. Sarma and R. H. Sarma, Adenine Press, New York, 1985. At this conference in Riva del Garda we were very hesitant to keep the name of the conference the same as the two previous ones. Indeed, a number of topics discussed in this conference were not included in the previous ones and even the emphasis of this gathering is only partly reflected in the conference title. An alternative title would have been Structure and Dynamics of Nucleic Acids, Proteins, and Higher Functions, or, possibly, "higher components" rather than "higher functions."

Any study on the historical evolution of nations and countries points out the decisive importance of productivity trends. We are all very familiar with the main evolution which started with a hunting society at the dawn of civilization, then moved to an agricultural society, and quickly to craftsmanship and com merce. The beginning of the industrial society dates back to the end of the eighteenth century in England, with the introduction of the assembly line in the textile and smelting industries. However, in the last few decades, we are becoming more and more acutely aware of the paramount importance of the production of "information." Indeed, according to a few economists today, we should be classified as living in an information society which has superseded the industrial society. At this point it simply becomes necessary to talk about the computer informa tion industry, which is more and more pervading our lives, from the personal computer, to the workstation, to information networks and electronic mail, to the blueprint executed by robots, to the supercomputer necessary in any major scientific and engineering task. The computer has already brought about a momentous change in the production line - less and less man-size, more and more robot-size. But this rush to tech nical innovation has not stopped at this point. Artificial intelligence and expert systems are becoming a more and more important factor for production by many enterprises and activities."

Principles and Practice of Stereotactic Radiosurgery, Second Edition serves as the definitive reference textbook for SRS practitioners. It provides a theoretical basis for the use of therapeutic radiation including imaging techniques and radiobiology. The bulk of the textbook contains chapters that are comprehensive in scope on all diseases that are treated by SRS. Lastly, it addresses administrative and technical aspects of running an SRS unit. Each chapter provides an expansive treatment of the subject, with emphasis placed on the technical aspects of SRS so that practitioners in this field can use it as a daily reference. Written by noted experts in the field, Principles and Practice of Stereotactic Radiosurgery, Second Edition is the only reference needed for neurosurgeons, radiation oncologists and medical physicists at all levels of training and practice who are interested in SRS.