Over the last few years there has been increasing need for systematic and straregically designed experiments of surface morphology evolution resulting form ion bombardment induced sputtering. Although there is an impressive number of investi gations {1} concerned with semiconductor materials as a result of immediate applications, the most systematic investigations have been conducted with fcc metals with particular interest on single crystal Cu {2,3}. Evidence now exists that within certain para meters (i. e ion species (Ar+), ion energy (20-44 KeV), substrate 2 temperature (80-550 Degrees K), dose rate (100-500 gA cm- ) , residual x 5 9 pressure (5 10- to 5x10- mm Hg) and polar and azimuthal angle of ion incidence {4} reproducible surface morphology (etch pits and pyramids) is achieved on the (11 3 1) specific crystallographic orientation. The temporal development of individual surface features was alsoobserved in this laterstudy {4}, by employing an in situ ion source in the scanning electron microscope at Salford, a technique also empolyed in studies of the influence of polar angle of ion incidence {5} and surface contaminants {6} on the topographyof Ar+ bombarded Si. Studies have also been made on the variation of incident ion species with the (11 3 1) Cu surface and it was fully recognized {7} that residual surface contaminants when present could playa major role in dictating the morhological evolution.

This book contains most, but regrettably not all, the papers that were presented at the Advanced Research Study Institute, ASI, held at the Fantasia Hotel, Kusadasi, Turkey, July 26 - August 8, 1998. A powerful incentive to the development of vortex physics in superconductors, that has began with Abrikosov Vortices in Shubnikov's Mixed State, was realized after the discovery of the high-Tc superconductivity. Indeed, a number of the most intriguing phenomena and states of the flux line lattice are observed in high-Tc superconducting materials due to their high anisotropy, intrinsically layered crys- tal structure, extremely small coherence length and the possibility of coexistence of superconducting vortex states with high-energy thermal fluctuation. These pe- culiarities are demonstrated as the 2D flux line lattice of point-vortices (pan- cakes), Josephson vortices or strings in parallel and/or tilted magnetic fields, flux line lattice melting into vortex liquid and its freezing into vortex "solid" (e. g. , crystal-or glass-like) state. It is well known, that the main reason for conditioning of the vortex ensemble state and behavior (except the extrinsic factors, such as applied magnetic field or temperature) is a set of intrinsic/extrinsic superconduct- ing material properties caused by the crystal nature and symmetry, atoms ar- rangement, anisotropy, as well as by the spectrum of crystal defects, their dimen- sions, arrangement and density.

This book contains most, but regrettably not all, the papers that were presented at The Advanced Research Workshop, held July 1-5, 1997, at Smolenice Castle, Slovak Republic. The problem of angular divergence is of great importance in quantum electronics: low divergence is required not only in most of practical laser applications, but also for achieving high efficiency of parametric laser frequency conversion, and harmonic generation. The large volume of available studies aimed at improving the pump systems and the spectroscopic properties of lasing media, brought about no more than 2-3 fold increases in laser efficiency, while concurrent studies of angular divergence and the implementation of the findings, resulted in several order of magnitude of increases in radiance. The spatial beam structure that is formed in the laser cavity together with the active element constitute the most critical laser elements. The engineering devices, such as excitation systems, lasing gas circulation systems, etc., are usually at the top of the agenda of scientific meetings and of gatherings of engineering experts. The divergence problem has never been discussed by a broad community of experts in this field.

In the thirty years since the invention of the CO2 gas laser, the major design issue has shifted from how to obtain the desired power level to how to achieve reliable operation. At the same time, the opening of many laser development facilities in the Former Soviet Union has allowed their achievements and design approaches to be understood and appreciated for the first time. Further, the industrial laser user community has identified a number of emerging applications at higher power levels (15-20 kW) than are attainable by most commercial devices. In High Power Lasers - Science and Engineering, the designers, developers and users of high-power gas laser systems discuss design approaches, methods of enhancing performance, new applications, and user requirements.

Advances in Materials Science and Implant Orthopedic Surgery brings together experts from major university hospitals, materials scientists specializing in bio-materials, and development engineers working for implant manufacturers to address such issues as: mechanisms of fixation; foreign-body immune response; generation and consequences of ionic and wear debris; materials selection, design and manufacturing schemes; and surgical techniques to maximize the safety and efficacy of the devices.

Combining experts from the medical and materials sciences, the Institute considered current concepts in medical and materials sciences as they relate to implantable prostheses in orthopedic surgical practice. The syllabus included theory and applications of materials properties, physiological function, and host response to metal and non-metal materials. Total hip prostheses are the most common orthopedic device implanted today involved in over 200,000 operations. Failures occur at the rate of 10~-40~ at ~ to 10 years. Failures are due to loosening, infection, fracture of femoral components, or destruction of the pe 1 vi c components .' All these, and other problems related to the implantation of the devices, the surgical procedures, and device pathology, were. discussed in light of current, as well as, emerging technologies and scientific knowledge. Repeatedly, scientists designing prostheses became aware of a lack of understanding of physiological phenomena associated with biocompatibility; the interchange among practising physicians, basic scientists, and pathologists at this Institute was appreciated. We thank all the contributors and participants for their effort. Thanks are also due to the personnel of the Scientific Affairs Division of NATO. The daily routines of running the Institute were greatly facilitated by the efforts of Pedro Cuevas, M.D, Jose Gutierrez Diaz, M.D, and Dr. Hanita Kossowsky. The devoted help of Nir Kossovsky, M.D, in setting the conference and in editing this book, is sincerely appreci ated.

Five questions dominated the ARW on Physics and Materials Science of High Temperature Superconductors, of which this book forms the permanent record. Briefly, these are: (i) How close are we to a unified theory? The consensus is that we are not. (ii) Flux pinning: can it be achieved in bulk materials? Still an open question. The following three questions are related. (iii) Can grain boundary contributions be brought under control? (iv) What is the real requirement for purity and general chemistry control? (v)What is the practical outlook for bulk products - tapes and wires? One of the conclusions is that the geometry and dimensions in thin films are the key parameters that facilitate the realization of high current densities and, consequently, their commercial application. On the other hand, the very large number of poorly understood microstructural, chemical and mechanical variables involved in the preparation of bulk materials are currently prohibiting large scale commercialization of wires and tapes.

Five questions dominated the ARW on Physics and Materials Science of High Temperature Superconductors, of which this book forms the permanent record. Briefly, these are: (i) How close are we to a unified theory? The consensus is that we are not. (ii) Flux pinning: can it be achieved in bulk materials? Still an open question. The following three questions are related. (iii) Can grain boundary contributions be brought under control? (iv) What is the real requirement for purity and general chemistry control? (v)What is the practical outlook for bulk products - tapes and wires? One of the conclusions is that the geometry and dimensions in thin films are the key parameters that facilitate the realization of high current densities and, consequently, their commercial application. On the other hand, the very large number of poorly understood microstructural, chemical and mechanical variables involved in the preparation of bulk materials are currently prohibiting large scale commercialization of wires and tapes.

Advances in Materials Science and Implant Orthopedic Surgery brings together experts from major university hospitals, materials scientists specializing in bio-materials, and development engineers working for implant manufacturers to address such issues as: mechanisms of fixation; foreign-body immune response; generation and consequences of ionic and wear debris; materials selection, design and manufacturing schemes; and surgical techniques to maximize the safety and efficacy of the devices.

Since the discovery of high temperature superconductivity, a tidal wave of res earch into the newly found phenomena took off in several directions. The theor ists began to examine BSC and its implications. Mostly everyone was syn thesizing materials.The experimentalists were studying relations among electri cal and magnetic properties while the pure materials scientists began to exam ine the microstructures, and the relations of processing to one or two measurab le parameters. The engineering and systems community were preparing real conductors and designing the needed components. Each of the communities was holding between two and three annual meetings to discuss most recent re sults. As work progressed, and promised applications did not materialize, it became apparent to us that the physics and materials science communities needed to establish solid communication lines. This NATO Advanced Study Institute was thus conceived and organized. This was a two week summer school, which 15 internationally acclaimed physicists and material scientists were invited to par ticipate in the capacity of Lecturers. Eighty students, from 12 different countries, also attended."

Over the last few years there has been increasing need for systematic and straregically designed experiments of surface morphology evolution resulting form ion bombardment induced sputtering. Although there is an impressive number of investi gations {1} concerned with semiconductor materials as a result of immediate applications, the most systematic investigations have been conducted with fcc metals with particular interest on single crystal Cu {2,3}. Evidence now exists that within certain para meters (i. e ion species (Ar+), ion energy (20-44 KeV), substrate 2 temperature (80-550 Degrees K), dose rate (100-500 gA cm- ) , residual x 5 9 pressure (5 10- to 5x10- mm Hg) and polar and azimuthal angle of ion incidence {4} reproducible surface morphology (etch pits and pyramids) is achieved on the (11 3 1) specific crystallographic orientation. The temporal development of individual surface features was alsoobserved in this laterstudy {4}, by employing an in situ ion source in the scanning electron microscope at Salford, a technique also empolyed in studies of the influence of polar angle of ion incidence {5} and surface contaminants {6} on the topographyof Ar+ bombarded Si. Studies have also been made on the variation of incident ion species with the (11 3 1) Cu surface and it was fully recognized {7} that residual surface contaminants when present could playa major role in dictating the morhological evolution.

The use of ion beams for the modification of the structure and properties of the near-surface region of ceramics began in earnest in the early 19805. Since the mechanical properties of such materials are dominated by surface flaws and the surface stress state, the use of surface modification tech niques would appear to be an obvious application. As is often the case in research and development, most of the initial studies can be characterized as cataloging the response of various ceramic materials to a range of ion beam treatments. The systematic study of material and ion beam parameters is well underway and we are now designing experiments to provide specific information about the processing parameter - structure-property rela tionships. This NATO-Advanced Study Institute was convened in order to assess our current state of knowledge in this field, to identify opportunities and needs for further research, and to identify the potential of such processes for technological application. It became apparent that this class of inorganic compounds, loosely termed ceramics, presents many challenges to the understanding of ion-solid inter actions, the relationships among ion-beam parameters, materials parameters, and the resulting structures, as well as relationships between structure and properties. In many instances, this understanding will represent a major extension of that learned from the study of metals and semiconductors."

Combining experts from the medical and materials sciences, the Institute considered current concepts in medical and materials sciences as they relate to implantable prostheses in orthopedic surgical practice. The syllabus included theory and applications of materials properties, physiological function, and host response to metal and non-metal materials. Total hip prostheses are the most common orthopedic device implanted today involved in over 200,000 operations. Failures occur at the rate of 10~-40~ at ~ to 10 years. Failures are due to loosening, infection, fracture of femoral components, or destruction of the pe 1 vi c components .' All these, and other problems related to the implantation of the devices, the surgical procedures, and device pathology, were. discussed in light of current, as well as, emerging technologies and scientific knowledge. Repeatedly, scientists designing prostheses became aware of a lack of understanding of physiological phenomena associated with biocompatibility; the interchange among practising physicians, basic scientists, and pathologists at this Institute was appreciated. We thank all the contributors and participants for their effort. Thanks are also due to the personnel of the Scientific Affairs Division of NATO. The daily routines of running the Institute were greatly facilitated by the efforts of Pedro Cuevas, M.D, Jose Gutierrez Diaz, M.D, and Dr. Hanita Kossowsky. The devoted help of Nir Kossovsky, M.D, in setting the conference and in editing this book, is sincerely appreci ated.

In the thirty years since the invention of the CO2 gas laser, the major design issue has shifted from how to obtain the desired power level to how to achieve reliable operation. At the same time, the opening of many laser development facilities in the Former Soviet Union has allowed their achievements and design approaches to be understood and appreciated for the first time. Further, the industrial laser user community has identified a number of emerging applications at higher power levels (15-20 kW) than are attainable by most commercial devices. In High Power Lasers - Science and Engineering, the designers, developers and users of high-power gas laser systems discuss design approaches, methods of enhancing performance, new applications, and user requirements.

This book contains most, but regrettably not all, the papers that were presented at The Advanced Research Workshop, held July 1-5, 1997, at Smolenice Castle, Slovak Republic. The problem of angular divergence is of great importance in quantum electronics: low divergence is required not only in most of practical laser applications, but also for achieving high efficiency of parametric laser frequency conversion, and harmonic generation. The large volume of available studies aimed at improving the pump systems and the spectroscopic properties of lasing media, brought about no more than 2-3 fold increases in laser efficiency, while concurrent studies of angular divergence and the implementation of the findings, resulted in several order of magnitude of increases in radiance. The spatial beam structure that is formed in the laser cavity together with the active element constitute the most critical laser elements. The engineering devices, such as excitation systems, lasing gas circulation systems, etc., are usually at the top of the agenda of scientific meetings and of gatherings of engineering experts. The divergence problem has never been discussed by a broad community of experts in this field.

This book contains most, but regrettably not all, the papers that were presented at the Advanced Research Study Institute, ASI, held at the Fantasia Hotel, Kusadasi, Turkey, July 26 - August 8, 1998. A powerful incentive to the development of vortex physics in superconductors, that has began with Abrikosov Vortices in Shubnikov's Mixed State, was realized after the discovery of the high-Tc superconductivity. Indeed, a number of the most intriguing phenomena and states of the flux line lattice are observed in high-Tc superconducting materials due to their high anisotropy, intrinsically layered crys- tal structure, extremely small coherence length and the possibility of coexistence of superconducting vortex states with high-energy thermal fluctuation. These pe- culiarities are demonstrated as the 2D flux line lattice of point-vortices (pan- cakes), Josephson vortices or strings in parallel and/or tilted magnetic fields, flux line lattice melting into vortex liquid and its freezing into vortex "solid" (e. g. , crystal-or glass-like) state. It is well known, that the main reason for conditioning of the vortex ensemble state and behavior (except the extrinsic factors, such as applied magnetic field or temperature) is a set of intrinsic/extrinsic superconduct- ing material properties caused by the crystal nature and symmetry, atoms ar- rangement, anisotropy, as well as by the spectrum of crystal defects, their dimen- sions, arrangement and density.