The role of high pressure experiments in the discovery of supercon ducting materials with a T. above liquid nitrogen temperature has demon strated the importance of such experiments. The same role holds true in the tailoring of materials for optoelectronic devices. In addition, much progress has been made recently in the search for metallic hydro gen, and the application of high pressure in polymer research has brought forth interesting results. These facts together with the suc cess of previous small size meetings (such as the "First International Conference on the Physics of Solids at High Pressure", held in 1965 in Tucson, Arizona, U. S. A. ; "High Pressure and Low Temperature Physics", held in 1977 in Cleveland, Ohio, U. S. A. ; and "Physics of Solids Under High Pressure", held in 1981 in bad Honnef, Germany), motivated us to organize a workshop with emphasis on the newest results and trends in these fields of high pressure research. Furthermore, it was intended to mix experienced and young scien tists to realize an idea best expressed in a letter by Prof. Weinstein: "I think it is an excellent idea. I have often felt that the number of excellent young researchers in the high pressure field need an opportu nity to put forward their work with due recognition. " Thanks to the support of the key speakers, we were able to achieve this goal and had more than 50\ young participants.

The author integrates discussions of fractal geometry, surface modeling techniques, and applications to real world problems to provide a comprehensive, accessible overview of the field. His work will equip researchers with the basic tools for measurement and interpretation of data, stimulating more work on these problems and, perhaps, leading to an understanding of the reasons that Nature has adopted this geometry to shape much of our world.

This volume contains the invited papers and selected contributed papers presented at the biennial International Symposium on ELECTRON COLLISIONS WITH MOLECULES, CLUSTERS AND SURF ACES held at Royal Holloway, University of London from 29th to 30th July, 1993. This Symposium was a Satellite Meeting of the XVIII International Conference on the Physics of Electronic and Atomic Collisions (ICPEAC) and follows a 16 year tradition of Satellite Conferences in related areas of collisions held in association with previous ICPEAC's. In the past each of these electron -molecule symposia covered the broad field of electron-molecule scattering at rather low energies, but also included hot topics. This time as well as covering the whole field, well defined electron collisions with clusters and with particles in the complex potential of a surface were emphasized. Not many details are known about such collisions, although they become more and more important in surface characterisation, plasma-wall interactions, electron induced desorption and reorganisation of adsorbed particles. Recently, much work, theoretical and experimental, has been devoted to electron collisions with rather large carbon, silicon and halogen containing molecules. These problems are of relevance in plasma assisted thin film formation and etching of surfaces and can now be approached with advanced theoretical methods and experimental equipment.

The aim of this NATO Advanced Study Institute was to bring together scientists and students working in the field of laser matter interactions in order to review and stimulate developmentoffundamental science with ultra-short pulse lasers. New techniques of pulse compression and colliding-pulse mode-locking have made possible the construction of lasers with pulse lengths in the femtosecond range. Such lasers are now in operation at several research laboratories in Europe and the United States. These laser facilities present a new and exciting research direction with both pure and applied science components. In this ASI the emphasis is on fundamental processes occurring in the interaction of short laser pulses with atoms, molecules, solids, and plasmas. In the case of laser-atom (molecule) interactions, high power lasers provide the first access to extreme high-intensity conditions above 10'8 Watts/em', a new frontier for nonlinear interaction of photons with atoms and molecules. New phenomena observed include multiphoton ionization processes, atomic collisions in the presence of a strong laser field, Coulomb explosion following rapid ionization of a molecule and the production of high harmonics of the laser source. Another important topic reviewed in this ASI is the lasercooling ofatoms.

The Nato Advanced Study Institute "Phase Transitions in Liquid Crystals" was held May 2-12, 1991, in Erice, Sicily. This was the 16th conference organized by the International School of Quantum Electronics, under the auspices of the "Ettore Majorana" Centre for Scientific Culture. The subject of "Liquid Crystals" has made amazing progress since the last ISQE Course on this subject in 1985. The present Proceedings give a tutorial introduction to today's most important areas, as well as a review of current results by leading researchers. We have brought together some of the world's acknowledged experts in the field to summarize both the present state of their research and its background. Most of the lecturers attended all the lectures and devoted their spare hours to stimulating discussions. We would like to thank them all for their admirable contributions. The Institute also took advantage of a very active audience; most of the students were active researchers in the field and contributed with discussions and seminars. Some of these student seminars are also included in these Proceedings. We did not modify the original manuscripts in editing this book, but we did group them according to the following topics: 1) "Theoretical Foundations"; 2) "Thermotropic Liquid Crystals"; 3) "Ferroelectric Liquid Crystals"; 4) "Polymeric Liquid Crystals"; and 5) "Lyotropic Liquid Crystals".

This report presents an account of the course "Nonlinear Spectroscopy of Solids: Advances and Applications" held in Erice, Italy, from June 16 to 30, 1993. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. The purpose of this course was to present and discuss physical models, mathematical formalisms, experimental techniques, and applications relevant to the subject of nonlinear spectroscopy of solid state materials. The universal availability and application of lasers in spectroscopy has led to the widespread observation of nonlinear effects in the spectroscopy of materials. Nonlinear spectroscopy encompasses many physical phenomena which have their origin in the monochromaticity, spectral brightness, coherence, power density and tunability of laser sources. Conventional spectroscopy assumes a linear dependence between the applied electromagnetic field and the induced polarization of atoms and molecules. The validity of this assumption rests on the fact that even the most powerful conventional sources of light produce a light intensity which is not strong enough to equalize the rate of stimulated emission and that of the experimentally observed decay. A different situation may arise when laser light sources are used, particularly pulsed lasers. The use of such light sources can make the probability of induced emission comparable to, or even greater than, the probability of the observed decay; in such cases the nonlinearity of the response of the system is revealed by the experimental data and new properties, not detectable by conventional spectroscopy, will emerge.

Covering both theory and applications, this important work provides a comprehensive introduction to the modern theory of X-ray and electronic spectra of free atoms. Romas Karazija discusses methods of angular momenta, irreducible tensorial operators, and coefficients of fractional parentage and their use in determining cross sections and probabilities of elementary processes. In addition, Karazija addresses the structure of electronic shells with inner vacancies and many-body effects.

This volume contains the papers presented at the NATO Advanced Research Workshop on "Magnetism and Structure in Systems of Reduced Dimension," held at l'Institut d'Etudes Scientifiques de Cargese - U.M.S. - C.N.R.S. - Universite de Corte Universite de Nice Sophia - Antipolis during June 15-19, 1992. The ordering of papers in the volume reflects the sequence of papers presented at the workshop. The aim was not to segregate the papers into rigidly defmed areas but to group the papers into small clusters, each cluster having a common theme. In this way the parallel, rather than serial, development of areas such as preparation of films, magnetic and structural characterization was highlighted. Indeed the success of the field depends on such parallel development and is assisted by workshops of this nature and the international collaborations which they foster. The organizers and participants of the NATO workshop express their thanks to Mme. Marie-France Hanseier and the staff at l'Institut d'Etudes Scientifiques de Cargese U.M.S. - C.N.R.S. - Universite de Corte - Universite de Nice Sophia - Antipolis for making the workshop and local arrangements a memorable success. Warm thanks are also expressed to Varadachari Sadagopan and Pascal Stefanou for their encouragement and help in making the workshop a reality. We are also grateful to Kristl Hathaway, Larry Cooper and Gary Prinz for advice in developing the workshop program."

Since the discovery in 1986 of high temperature superconductors by J. G. Bednorz and K. A. Muller, a considerable progress has been made and several important scientific problems have emerged. Within this NATO Advanced Study Institute our intention was to focus mainly on the controversial topic of the symmetry of the superconducting gap and given the very short coherence length, the role of fluctuations. The Institute on 'The Gap Symmetry and Fluctuations in High- Superconductors' took place in the "Institut d'Etudes Scientifiques de Cargese" in Corsica, France, between 1 - 13 September 1997. The 110 participantsfrom 18 countries (yet 30 nationalities) including 23 full time lecturers, have spent two memorable weeks in this charming Mediterranean resort. All lecturers were asked to prepare pedagogical papers to clearly present the central physical idea behind specific model or experiment. The better understanding of physics of high temperature superconductivity is certainly needed to guide the development of applications of these materials in high and weak current devices.

Small-angle scattering of X rays and neutrons is a widely used diffraction method for studying the structure of matter. This method of elastic scattering is used in various branches of science and technology, includ ing condensed matter physics, molecular biology and biophysics, polymer science, and metallurgy. Many small-angle scattering studies are of value for pure science and practical applications. It is well known that the most general and informative method for investigating the spatial structure of matter is based on wave-diffraction phenomena. In diffraction experiments a primary beam of radiation influences a studied object, and the scattering pattern is analyzed. In principle, this analysis allows one to obtain information on the structure of a substance with a spatial resolution determined by the wavelength of the radiation. Diffraction methods are used for studying matter on all scales, from elementary particles to macro-objects. The use of X rays, neutrons, and electron beams, with wavelengths of about 1 A, permits the study of the condensed state of matter, solids and liquids, down to atomic resolution. Determination of the atomic structure of crystals, i.e., the arrangement of atoms in a unit cell, is an important example of this line of investigation."

At first glance, the articles in this book may appear to have nothing in common. They cover such seemingly disparate subjects as the properties of small metallic clusters and the behavior of superfluid He3, nuclear physics and organic materials, copper oxides and mag netic resonance. Why have they been brought together, particUlarly in our time of narrow spe cialization? In fact, the properties and effects described in this book touch upon one and the same fundamental phenomenon: pair correlation. Introduced in the theory of superconductivity by J. Bardeen, L. Cooper, and J. Schrieffer (BCS), this effect plays a key role in various Fermi systems. The book consists of several sections. The first chapter is concerned with conven tional and high Tc superconductors. The second chapter describes two relatively young fami lies of superconductors: organics and fullerenes. Chapter III addresses the superfluidity of 3 He * The discovery of this phenomenon in 1971 was a big event in physics and last year was acknowledged by a Nobel prize. This book contains the text of the Nobel lecture. Chapters IV and V are devoted to correlations in finite Fermi systems such as small metallic clusters, C 60 anions, and atomic nuclei. The book thus covers a broad range of problems, illuminating the close ties between various areas of physics.

Much of this book was written during a sabbatical visit by J. C. H. S. to the Max Planck Institute in Stuttgart during 1991. We are therefore grateful to Professors M. Ruhle and A. Seeger for acting as hosts during this time, and to the Alexander von Humbolt Foundation for the Senior Scientist Award which made this visit possible. The Ph. D. work of one of us (J. M. Z. ) has also provided much of the background for the book, together with our recent papers with various collaborators. Of these, perhaps the most important stimulus to our work on convergent-beam electron diffraction resulted from a visit to the National Science Foundation's Electron Microscopy Facility at Arizona State University by Professor R. H(lJier in 1988, and from a return visit to Trondheim by J. C. H. S. in 1990. We are therefore particularly grateful to Professor H(lJier and his students and co-workers for their encouragement and collaboration. At ASU, we owe a particular debt of gratitude to Professor M. O'Keeffe for his encouragement. The depth of his under standing of crystal structures and his role as passionate skeptic have frequently been invaluable. Professor John Cowley has also been an invaluable sounding board for ideas, and was responsible for much of the experimental and theoretical work on coherent nanodiffraction. The sections on this topic derive mainly from collaborations by J. C. H. S. with him in the seventies.

This book reviews all the state-of-the-art simulation methods used to investigate the atomistic-scale properties of technologically important oxide materials. Previous and many recent results are carefully discussed.

Although exploratory and developmental activity in electron beam testing (EBT) 25 years, it was not had already been in existence in research laboratories for over until the beginning of the 1980s that it was taken up seriously as a technique for integrated circuit (IC) testing. While ICs were being fabricated on design rules of several microns, the mechanical ne edle probe served quite adequately for internal chip probing. This scenario changed with growing device complexity and shrinking geometries, prompting IC manufacturers to take note ofthis new testing technology. It required several more years and considerable investment by electron beam tester manufacturers, however, to co me up with user-friendly automated systems that were acceptable to IC test engineers. These intervening years witnessed intense activity in the development of instrumentation, testing techniques, and system automation, as evidenced by the proliferation of technical papers presented at conferences. With the shift of interest toward applications, the technology may now be considered as having come of age.

Molecular similarity has always been an important conceptual tool of chemists, yet systematic approaches to molecular similarity problems have only recently been recognized as a major contributor to our understanding of molecular properties. Advanced approaches to molecular similarity analysis have their foundation in quantum similarity measures, and are important direct or indirect contributors to some of the predictive theoretical, computational, and also experimental methods of modern chemistry. This volume provides a survey of the foundations and the contemporary mathematical and computational methodologies of molecular similarity approaches, where special emphasis is given to applications of similarity studies to a range of practical and industrially significant fields, such as pharmaceutical drug design. The authors of individual chapters are leading experts in various sub-fields of molecular similarity analysis and the related fundamental theoretical chemistry topics, as well as the relevant computational and experimental methodologies. Whereas in each chapter the emphasis is placed on a different area, nevertheless, the overall coverage and the wide scope of the book provides the reader with a general yet sufficiently detailed description that may serve as a good starting point for new studies and applications of molecular similarity approaches. The editors of this volume are grateful to the authors for their contributions, and hope that the readers will find this book a useful and motivating source of information in the rapidly growing field of molecular similarity analysis.

This thesis presents results from a combined atomic-resolution Z-contrast and annular bright-field imaging and electron energy loss spectroscopy in the Scanning Transmission Electron Microscopy, as well as first principles studies of the interfaces between crystalline Si3N4 and amorphous (i) CeO2-x as well as (ii) SiO2 intergranular film (IGF). These interfaces are of a great fundamental and technological interest because they play an important role in the microstructural evolution and mechanical properties of Si3N4 ceramics used in many high temperature and pressure applications. The main contribution of this work is its detailed description of the bonding characteristics of light atoms, in particular oxygen and nitrogen, at these interfaces, which has not been achieved before. The atomic-scale information on the arrangement of both light and heavy atoms is critical for realistic modeling of interface properties, such as interface strength and ion transport, and will facilitate increased control over the performance of ceramic and semiconductor materials for a wide-range of applications.

"You, 0 Sun, are the eye of the world You are the soul of all embodied beings You are the source of all creatures You are the discipline of all engaged in work" - Translated from Mahabharata 3rd Century BC Today, energy is the lifeline and status symbol of "civilized" societies. All nations have therefore embarked upon Research and Development pro grams of varying magnitudes to explore and effectively utilize renewable sources of energy. Albeit a low-grade energy with large temporal and spatial variations, solar energy is abundant, cheap, clean, and renewable, and thus presents a very attractive alternative source. The direct conver sion of solar energy to electricity (photovoltaic effect) via devices called solar cells has already become an established frontier area of science and technology. Born out of necessity for remote area applications, the first commercially manufactured solar cells - single-crystal silicon and thin film CdS/Cu2S - were available well over 20 years ago. Indeed, all space vehicles today are powered by silicon solar cells. But large-scale terrestrial applications of solar cells still await major breakthroughs in terms of discovering new and radical concepts in solar cell device structures, utilizing relatively more abundant, cheap, and even exotic materials, and inventing simpler and less energy intensive fabrication processes. No doubt, this extraordinary challenge in R/D has led to a virtual explosion of activities in the field of photovoltaics in the last several years."

Many and ever more mobile users wish to enjoy a variety of multimedia services, in very diverse geographical environments. The growing number of communication options within and across wireless standards is accommodating the growing volume and heterogeneity in wireless wishes. On the other hand, advancement in radio technologies opening much more flexibility, a.o. through Software Defined Radios, opens up the possibility to realize mobile devices featuring multi-mode options at low cost and interesting form factors.

It is crucial to manage the new degrees of freedom opened up in radios and standards in a smart way, such that the required service is offered at satisfactory quality as efficiently as possible. Efficiency in energy consumption is clearly primordial for battery powered mobile terminals specifically, and in the context of growing ecological concerns in a broader context. Moreover, efficient usage of the spectrum is a growing prerequisite for wireless systems, and coexistence of different standards puts overall throughput at risk.

The management of flexibility risks bringing about intolerable complexity and hamper the desired agility. A systematic approach, consisting of anticipative preparing for smooth operation, allows mastering this challenge. Case studies show that already today, this approach enables smart operation of radios realizing impressive efficiency gains without hampering Quality-of-Service. In the future wireless communication scenes will be able to profit form the opening of the spectrum. Even smarter and cognitive behavior will become possible and essential.

This volume contains the lectures and seminars presented at the NATO Advanced Study Institute on IIAdvances in Laser Spectroscopyll the tenth course of the Europhysics School of Quantum Electronics, held under the supervision of the Quantum Electronics Division of the European Physical Society. The Institute was held at Centro "I Cappuccinill San Miniato, Tuscany, July 26, - August 7, 1981. The Europhysics School of Quantum Electronics was started in 1970 with the aim of providing instruction for young researchers and advanced students already engaged in the area of quantum elec- tronics or wishing to switch to this area from a different back- ground. From the onset, the School has been under the direction of Prof. F. T. Arecchi, then at the University of Pavia, now at the University of Florence, .and Dr. D. Roess of Siemens, Munich. In 1981, Prof. H. Walther, University of Munich and Max-Planck- Institut fUr Quantenoptik joined as director. Each year the Directors choose a subject of particular interest, alternating fundamental topics with technological ones, and ask colleagues specifically competent in a given area to take the scientific responsibility for that course.

This series of books, which is published at the rate of about one per year, addresses fundamental problems in materials science. The contents cover a broad range of topics from small clusters of atoms to engineering materials and involve chemistry, physics, and engineering, with length scales ranging from Angstromsup to millimeters. The emphasis is on basic science rather than on applications. Each book focuses on a single area ofcurrent interest and brings together leading experts to give an up-to-date discussion of their work and the work ofothers. Each article contains enough references that the interested reader can accesstherelevant literature. Thanks aregiven to the Center forFundamental Materials Research atMichigan State University forsupportingthis series. M.F. Thorpe, Series Editor E-mail: [email protected] EastLansing, Michigan, September, 1995 PREFACE This book records selected papers given at an interdisciplinary Symposium on Access in Nanoporous Materials held in Lansing, Michigan, on June 7-9, 1995. Broad interest in the synthesis of ordered materials with pore sizes in the 1.0-10 nm range was clearly manifested in the 64 invited and contributed papers presented by workers in the formal fields of chemistry, physics, and engineering. The intent of the symposium was to bring together a small number ofleading researchers within complementary disciplines to share in the diversity of approaches to nanoporous materials synthesis and characterization."

are intended to fill the gap between a manufacturer's handbook, and review articles that highlight the latest scientific developments. A fourth volume will deal with techniques for specimen handling, beam artifacts, and depth profiling. It will provide a compilation of methods that have proven useful for specimen handling and treatment, and it will also address the common artifacts and problems associated with the bombardment of solid sur faces by photons, electrons, and ions. A description will be given of methods for depth profiling. Surface characterization measurements are being used increasingly in di verse areas of science and technology. We hope that this series will be useful in ensuring that these measurements can be made as efficiently and reliably as possible. Comments on the series are welcomed, as are suggestions for volumes on additional topics. C. J. Powell Gaithersburg, Maryland A. W. Czandema Golden, Colorado D. M. Hercules Pittsburgh, Pennsylvania T. E. Madey New Brunswick, New Jersey J. T. Yates, Jr."

This book contains papers presented at the International Conference on Organic Superconductivity which was held May 20-24, 1990, at the Stanford Sierra Conference Center, South Lake Tahoe, California. In the twenty years since the First Conference on Organic Superconductivity was held (Hawaii, 1969), there has been remarkable progress in the field. At present, development is accelerating with contributions from many groups in many countries worldwide. The discovery of high Tc superconductivity by G. Bednorz and K. Muller in 1986 and subsequent developments in the ceramic superconductors have had an enormous impact on the field of superconductivity as a whole. This discovery occurred in an area entirely different from that of conventional superconduc tivity, underscoring the importance of the search for and study of novel materials of all kinds. We believe that the organics, with their wide range of structural, chemical, and physical properties, belong in this category of novel materials. This book reflects the efforts of researchers from various disciplines: physicists, chemists, and materials scientists. It addresses the normal and superconducting properties of organic materials, as well as the search for new compounds and new syntheses. We are pleased to note that one of these papers reports on the discovery of a new organic superconductor with a record high Tc in this class. One chapter is devoted to a comparison of organic superconductors and the cuprates, another, to the prospects of discovering other novel conducting or superconducting compounds."

The workshop entitled Magnetic Susceptibility of Superconductors and other Spin Systems (S4) was held at Coolfont Resort and Health Spa. located near Berkley Springs West Virginia on May 20-23. 1991. There were over sixty attendees. approximately half from the United States. the remainder representing over twelve different countries. The international character of the workshop may be gleaned form the attendee list, included in this volume. The intent of the workshop was to bring together those experimentalists and theoreticians whose efforts have resulted in significant recent contributions to the development and use of the ac susceptibility technique as well as to the interpretation of data obtained from these measurements. Many spirited discussions occurred during and after the presentations. These are reflected in the manuscripts contained in these proceedings. Although camera ready manuscripts were required from all participants at registration, all manuscripts were revised and reflect the lively exchanges that followed each presentation. The small size of the workshop allowed the participants a high degree of flexibility. Consequently when a controversial topic such as "the irreversibility line" emerged, a special session was organized on the spot. At the suggestion of Ron Goldfarb, participants were invited to contribute a one page summary containing their thoughts on the topic. These stand alone contributions were retyped and included as submitted, with only minor editorial changes. These proceedings are intended for those experienced scientists new to the field and graduate students just beginning their research.

The great advantage of coincidence measurements is that by suitable choice of the kinematical and geometrical arrangement one may probe delicate physical effects which would be swamped in less differential experiments. The measurement of the triple dif ferential and higher-order cross sections presents enormous technical difficulties, but refined experiments of this type provide an insight into the subtleties of the scattering process and offer a welcome, if severe, test of the available theoretical models. The last few years have been an exciting time to work in the field and much has been learned. Profound insights have been gleaned into the basic Coulomb few body problem in atomic physics: the experimental study of the fundamental (e,2e) processes on hydrogen and helium targets continues to add to our knowledge and indeed to challenge the best of our theoretical models; significant advances have been made in the understanding of the "double excitation problem," that is the study of ionization processes with two active target electrons: important measurements of (e,3e), (, ), 2e), excitation-ionization and excitation autoionization have been reported and strides have been made in their theoretical description; the longstanding discrepancies between theory and experiment for relativistic (e,2e) processes were resolved, spin dependent effects predicted and ob served and the first successful coincidence experiments on surfaces and thin films were announced. Theory and experiment have advanced in close consort. The papers pre sented here cover the whole gambit of research in the field. Much has been achieved but much remains to be done."