"Great progress has been made in electrical science, chiefly in Germany, by cultivators of the theory of action at a distance. The valuable electrical measurements of W. Weber are interpreted by him according to this theory, and the electromagnetic speculation which was originated by Gauss, and carried on by Weber, Riemann, F. and C. Neumann, Lorenz, etc. , is founded on the theory of action at a distance, but depending either directly on the relative velocity of the particles, or on the gradual propagation of something, whether potential or force, from the one particle to the other. The great success which these eminent men have attained in the application of mathematics to electrical phenomena, gives, as is natural, additional weight to their theoretical speculations, so that those who, as students of electricity, turn to them as the greatest authorities in mathematical electricity, would probably imbibe, along with their mathematical methods, their physical hypothesis. These physical hypotheses, however, are entirely alien from the way of looking at things which I adopt, and one object which I have in view is that some of those who wish to study electricity may, by reading this treatise, come to see that there is another way of treating the subject, which is no less fitted to explain the phenomena, and which, though in some parts it may appear less definite, corresponds, as I think, more faithfuHy with our actual knowledge, both in what it affirms and in what it leaves undecided.

The NATO Advanced Research Workshop on Coherent Optical Processes in Semiconductors was held in Cambridge, England on August 11-14,1993. The idea of holding this Workshop grew from the recent upsurge in activity on coherent transient effects in semiconductors. The development of this field reflects advances in both light sources and the quality of semiconductor structures, such that tunable optical pulses are now routinely available whose duration is shorter than the dephasing time for excitonic states in quantum wells. It was therefore no surprise to the organisers that as the programme developed, there emerged a heavy emphasis on time-resolved four-wave mixing, particularly in quantum wells. Nevertheless, other issues concerned with coherent effects ensured that several papers on related problems contributed some variety. The topics discussed at the workshop centred on what is a rather new field of study, and benefited enormously by having participants representing many of the principal groups working in this area. Several themes emerged through the invited contributions at the Workshop. One important development has been the careful examination of the two-level model of excitonic effects; a model which has been remarkably successful despite the expected complexities arising from the semiconductor band structure. Indeed, modest extensions to the two level model have been able to offer a useful account for some of the complicated polarisation dependence of four-wave mixing signals from GaAs quantum wells. This work clearly is leading to an improved understanding of excitons in confined systems.

Cosmic electrodynamics is the specific branch of plasma physics which studies electromagnetic phenomena -- mostly the role of electromagnetic forces in dynamics of highly-conducting compressible medium in the solar interior and atmosphere, solar wind, in the Earth's magnetosphere and magnetospheres of other planets as well as pulsars and other astrophysical objects. This textbook is written to be used at several different levels. It is aimed primarily at beginning graduate students who are assumed to have a knowledge of basic physics. Starting from the language of plasma physics, from Maxwell's equations, the author guides the reader into the more specialized concepts of cosmic electrodynamics. The main attention in the book is paid to physics rather than maths. However, the clear mathematical image of physical processes in space plasma is presented and spelled out in the surrounding text. There is not another way to work in modern astrophysics at the quantitative level. The book will also be useful for professional astronomers and for specialists, who investigate cosmic plasmas from space, as well as for everybody who is interested in modern astrophysics.

Intersubband transitions in quantum wells have attracted tremendous attention in recent years, mainly due to the promise of applications in the mid and far-infrared regions (2--20 mum). Many of the papers presented in Quantum Well Intersubband Transition Physics and Devices are on the basic linear intersubband transition processes, detector physics and detector application, reflecting the current state of understanding and detector applications, where highly uniform, large focal plane arrays have been demonstrated. Other areas are still in their early stages, including infrared modulation, harmonic generation and emission.

Magnetostatic Waves and their Applications is the first book devoted to magnetostatic waves. The book gives a thorough review of the field suitable for scientists, engineers and advanced students involved in magnetism and microwave electronics new to this area. It covers the field from essential physics to applications in microwave electronics, with details of the materials and materials processing methods included.

During the past 30 years materials science has developed into a full-fledged field for basic and applied scientific enquiry. Indeed, materials scientists have devoted their efforts to creating new materials with improved electronic, magnetic, thermal, mechanical, and optical properties. Often unnoticed, these new materials are rapidly invading our homes and automobiles, and may be found in our utensils, electronic equipment, textiles, home appliances, and electric motors. Even though they may go unnoticed, these new materials have either improved the efficiency and lifetime of these items or have reduced their weight or cost. In particular, magnetically ordered materials are useful in various applications, such as motors, magnetic imaging, magnetic recording, and magnetic levitation. Hence, much effort has been devoted to the development of better hard magnetic materials, magnetic thin films, and molecular magnets. During the same period of time, Mossbauer-effect spectroscopy has grown from a laboratory curiosity to a mature spectroscopic technique, a technique that probes solid-state materials at specific atomic sites and yields microscopic information on the magnetic and electronic properties of these materials. Iron-57 is the most commonly and easily used Mossbauer-effect isotope and, of course, is particularly relevant for the study of magnetic materials. Various applications of Mossbauer spectroscopy to magnetic materials are discussed in the first six chapters of this volume. Other isotopes such as zinc-67 and gadolinium-ISS have recently been used to study the electronic properties of zinc compounds and the electronic and magnetic properties of rare-earth transition metal compounds.

This book is based on the contributions to a course, entitled Applied Magnetism, which was the 25th Course of the International School of Materials Science and Technology. The Course was held as a NATO Advanced Study Institute at the Ettore Majorana Centre in Erice, Sicily, Italy between the 1st and 12th July 1992, and attracted almost 70 participants from 15 different countries. The book deals with the theory, experiments and applications of the main topical areas of applied magnetism. These selected areas include the physics of magnetic recording, magnetic and magneto-optic recording devices, systems and media, magnetic fine particles, magnetic separation, domains and domain walls in soft magnetic materials, permanent magnets, magnetoresistance, thin film magneto-optics, and finally, microwave, optical and computational magnetics. The material is organised into I 0 self-contained chapters which together provide a comprehensive coverage of the subject of applied magnetism. The aim is to emphasise the connection between the fundamental theoretical concepts, key experiments and the important technological developments which have been achieved in this field up to the present time. Moreover, when and where possible, pointers to future trends are indicated which hopefully, together with the background material, will promote further advancement of research. The organizing committee would like to acknowledge the sponsorship of the NATO Scientific Affairs Division, the National Science Foundation of the USA, the Science and Engineering Research Council of the UK, the Italian Ministry of Education, the Italian Ministry of University and Scientific Research and the Sicilian Regional Government.

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."

In the years since the book of Lozanskii and Firsov "The Theory of Spark" 1975] was published, a number of experimental and theoretical studies in the physics of electric breakdown in gases were conducted. As a result of these studies, the concept of a wavelike nature of breakdown initiated by single high-voltage electric pulses or by a constant electric field was confirmed. Theoretical models in which the concept of breakdown in a constant external field was developed were first exposed in the above-named book in the chapter "Development of a streamer regarded as an ionization wave," written by Rodin and Starostin. This book treats the initial stage of electric breakdown as a wave pro cess. The wavelike nature of the phenomena under consideration is pre sented for streamers and sliding discharges, for electric breakdown develop ment in long discharge tubes as well as in gas-filled gaps. Chapter 1 gives a qualitative consideration of phenomena determin ing the electric breakdown of gases. The experimental data and theoretical results are exposed and discussed with application to streamers, plane ion ization waves, breakdown waves in long tubes, and propagation of sliding discharges. The subject of this chapter may be considered as an area of applications of different theoretical models, formulas, and estimates that are presented in other chapters of the book."

In this book, the author draws on his broad experience to describe both the theory and the applications of wave propagations. The contents are presented in four parts and the sequence of these parts reflect the development of ionospheric and propagational research in areas such as space research geophysics and communications. The first part of the book presents an outline of the theory of electromagnetic waves propagating in a cold electron plasma. For reference, vector analysis, dyadics and eigenvalues introduced in this part are presented in the appendices. Practical aspects of radio wave propagation are the subject of the second part. The typical conditions in different frequency ranges are discussed and the irregular features of the ionospheric structure such as sound and gravity waves are also considered. Warm plasma and the effects of ions are considered in the third part, which includes a discussion of sound-like waves in electron and ion plasmas. Nonlinear effects and instabilities are described in the fourth part.

The NATO Advanced Research Workshop on "Nanomagnetic Devices" was held in Miraflores de la Sierra, Madrid, Spain, from 14 to 19 September 1992. This book contains 21 invited articles related to suggestive and relevant aspects of Magnetism. The NATO Advanced Research Workshop was Co-directed by R.C. O'Handley, B. Heinrich and A. Hernando. The organisers as well as the participants are gratefully acknowledged to the NATO Science Committee. I also wish to thank the publishers for their advice and help in organizing the book. xi DESIDERATA OF STORAGE DEVICES C.E. YEACK-SCRANTON IBM Corporation, E02/005 5600 Cottle Road San Jose, CA 95139 USA ABSTRACT. Typical requirements on cost, capacity, and performance of today's magnetic storage devices and industry trends in these attributes are given. Scaling components, devices, and materials is shown to be a key factor in further improvement, Challenges to continued scaling are reviewed, particularly as they relate to magnetic nano-structures, materials, and characterization techniques.

The workshop on "Optical Properties of Low Dimensional Silicon sL Structures" was held in Meylan, France on March, I yd, 1993. The workshop took place inside the facilities of France Telecom- CNET. Around 45 leading scientists working on this rapidly moving field were in attendance. Principal support was provided by the Advanced Research Workshop Program of the North Atlantic Treaty Organisation (NATO). French Delegation a l'Armement and CNET gave also a small financial grant, the organisational part being undertaken by the SEE and CNET. There is currently intense research activity worldwide devoted to the optical properties of low dimensional silicon structures. This follow the recent discovery of efficient visible photoluminescence (PL) from highly porous silicon. This workshop was intended to bring together all the leading European scientists and laboratories in order to reveal the state of the art and to open new research fields on this subject. A large number of invited talks took place (12) together with regular contribution (20). The speakers were asked to leave nearly 1/3 of the time to the discussion with the audience, and that promoted both formal and informal discussions between the participants.

The purpose of this book is to provide core material in nonlinear analysis for mathematicians, physicists, engineers, and mathematical biologists. The main goal is to provide a working knowledge of manifolds, dynamical systems, tensors, and differential forms. Some applications to Hamiltonian mechanics, fluid mechanics, electromagnetism, plasma dynamics and control theory are given using both invariant and index notation. The prerequisites required are solid undergraduate courses in linear algebra and advanced calculus.

The Advanced Research Workshop on the Physical Properties of Semiconductor Interfaces at the Sub-Nanometer Scale was held from 31 August to 2 September, 1992, in Riva del Garda. Italy. The aim of the workshop was to bring together experts in different aspects of the study of semiconductor interfaces and in small-scale devices where the interface properties can be very significant It was our aim that this would help focus research of the growth and characterization of semiconductor interfaces at the atomic scale on the issues that will have the greatest impact on devices of the future. Some 30 participants from industrial and academic research institutes and from 11 countries contributed to the workshop with papers on their recent wode. . 'There was ample time for discussion after each talk. as well as a summary discussion at the end of the meeting. The major themes of the meeting are described below. The meeting included several talks relating to the different growth techniques used in heteroepitaxial growth of semiconductors. Horikoshi discussed the atomistic processes involved in MBE, MEE and MOCVD, presenting results of experimental RHEED and photoluminescence measurements; Foxon compared the merits of MBE, MOCVD, and eBE growth; Molder described RHEED studies of Si/Ge growth by GSMBE, and Pashley discussed the role of surface reconstructions in MBE growth as seen from STM studies on GaAs. On the theoretical side, Vvedensky described several different methods to model growth: molecular dynamics, Monte Carlo techniques, and analytic modeling.

Market: Physicists, chemists, biochemists, and biologists. Here's the first book to gather the vast range of experimental data in electron spin resonance (ESR) into a single volume. Concise yet comprehensive, it offers an easy-to-use collection of up-to-date experimental data, methods, and theory. The Handbook includes key contributions from leading scientists and provides over 200 tables and figures. Although specific ESR subfields are covered in numerous books and journals, the Handbook of Electron Spin Resonance is the only comprehensive reference to present extensive tabulation of data and experimental results. The Handbook also provides introductions to theoretical backgrounds, methods, and instrumentation.

Professor Dobbs provides an elegant and clear account of the subject, leading the student from electrostatics through to Maxwell's equations and electromagnetic waves, covering all the material needed by a student taking courses on electricity and magnetism and electromagnetic waves.

In the last ten years, the physics and technology of low dimensional structures has experienced a tremendous development. Quantum structures with vertical and lateral confinements are now routinely fabricated with feature sizes below 100 run. While quantization of the electron states in mesoscopic systems has been the subject of intense investigation, the effect of confinement on lattice vibrations and its influence on the electron-phonon interaction and energy dissipation in nanostructures received atten tion only recently. This NATO Advanced Research Workshop on Phonons in Sem iconductor Nanostructures was a forum for discussion on the latest developments in the physics of phonons and their impact on the electronic properties of low-dimensional structures. Our goal was to bring together specialists in lattice dynamics and nanos tructure physics to assess the increasing importance of phonon effects on the physical properties of one-(lD) and zero-dimensional (OD) structures. The Workshop addressed various issues related to phonon physics in III-V, II-VI and IV semiconductor nanostructures. The following topics were successively covered: Models for confined phonons in semiconductor nanostructures, latest experimental observations of confined phonons and electron-phonon interaction in two-dimensional systems, elementary excitations in nanostructures, phonons and optical processes in reduced dimensionality systems, phonon limited transport phenomena, hot electron effects in quasi - ID structures, carrier relaxation and phonon bottleneck in quantum dots."

The unexpected and therefore really amazing discovery of J.G. Bednorz and K.A. MA1/4ller, that certain oxide compounds enter a superconductivity state at temperatures above 30 K, pushed research on superconductivity into the limelight of science in general in a way that seemed reserved only for high energy or particle physics. It may therefore be expected that this entire review would solely deal with superconductivity at high temperatures, i.e. above the boiling point of hydrogen. Any unexpected occurrence of superconductivity is, however, a challenge to scientists interested either in the physics of this phenomenon or in its materials science aspects. In this respect, the eighties have been quite revolutionary in the sense that, on various occasions, superconductivity was discovered in materials whose physical properties were not obviously favourable for adopting this ground state. Therefore, apart from emphasizing the topic of oxide superconductors, this collection of reprints also contains a selection of papers that deal with other subjects, such as coexistence of magnetic order and superconductivity, heavy electron and organic superconductors. This is all the more justified when we consider the fact that various aspects of superconductivity in high Tc oxide compounds are, or might be, connected with features that are also observed in these other materials. For nonspecialists who might be interested in this collection of reprints the Editor briefly reviews the possibilities for identifying superconductivity and discusses some special features of the superconducting state.

This book is the result of a NATO Advanced Research Workshop held in Vimeiro, Portugal, in May 1992. The objectives of this Workshop were: i) to promote exchange of knowledge between experts in various fields of discharge modeling, plasma diagnostics and microwave plasma applications; ii) to assess the state-of-the-art in this field from a multidisciplinary viewpoint; iii) to identify basic points needing clarification and to estab- lish basic guidelines for future research; iv) to compare the properties of microwave dis- charges to those of RF discharges, as plasma sources for specific applications. Most of the contributors to this book are well known scientists in the field of mi- crowave discharge sources, modeling, diagnostics and applications. The book provides an up-to-date review in this field which should be useful for both the fundamentalists and those using these systems in applications such as surface treatment and elemental analysis. We are gmteful to a number of organizations for providing the fmancial assistance that made the Workshop possible. Foremost is the NATO Scientific Affairs Division, which provided the major contribution for the Workshop. In addition, the following Por- tuguese sources made contributions: Instituto Nacional de Investiga~iio Cientifica, Junta Nacional de Investiga~iio Cientifica e Tecnologica, Centro de Electrodinamica da Univer- sidade Tecnica de Lisboa, Instituto Superior Tecnico, Banco Nacional Ultmmarino, and Regiiio de Turismo do Oeste.

Our life is a highly nonlinear process. It starts with birth and ends with death; in between there are a lot of ups and downs. Quite often, we believe that stable and steady situations, probably easy to capture by linearization, are paradisiacal, but already after a short period of everyday routine we usually become bored and seek change, that is, nonlinearities. If we reflect for a while, we notice that our life and our perceptions are mainly determined by nonlinear phenomena, for example, events occurring suddenly and unexpectedly. One may be surprised by how long scientists tried to explain our world by models based on a linear ansatz. Due to the lack of typical nonlinear patterns, although everybody experienced nonlinearities, nobody could classify them and, thus, . study them further. The discoveries of the last few decades have finally provided access to the world of nonlinear phenomena and have initiated a unique inter disciplinary field of research: nonlinear science. In contrast to the general tendency of science to become more branched out and specialized as the result of any progress, nonlinear science has brought together many different disciplines. This has been motivated not only by the immense importance of nonlinearities for science, but also by the wonderful simplicity ohhe concepts. Models like the logistic map can be easily understood by high school students and have brought revolutionary new insights into our scientific under standing."

It is widely recognized that an understanding of the optical pro perties of matter will give a great deal of important information re levant to the fundamental physical properties. This is especially true in semiconductor physics for which, due to the intrinsic low screening of these materials, the optical response is quite rich. Their spectra reflect indeed as well electronic as spin or phonon transitions. This is also in the semiconductor field that artificial structures have been recently developed, showing for the first time specific physical properties related to the low dimentionality of the electronic and vi bronic properties: with this respect the quantum and fractional quan tum Hall effects are among the most well known aspects. The associated reduced screening is also a clear manifestation of these aspects and as such favors new optical properties or at least significantly enhan ces some of them. For all these reasons, it appeared necessary to try to review in a global way what the optical investigation has brought today about the understanding of the physics of semiconductors. This volume collects the papers presented at the NATO Advanced study Inst i tut e on "Optical Properties of Semiconductors" held at the Ettore Majorana Centre, Erice, Sicily on March 9th to 20th, 1992. This school brought together 70 scientists active in research related to optical properties of semiconductors. There were 12 lecturers who pro vided the main contributions ."

Electrophotography and Development Physics focuses on the complicated and increasingly important technology found in photocopiers and laser printers. An introduction chapter acquaints the reader with the technical history of electrophotography, its current and projected markets, and also alternative related copying and printing technologies. A concise descriptionof the physics of the complete electrophotgraphic process is followed by an in-depth treatment of static electricity. The three types of developmentsystems (two component, monocomponent, and liquid), and their associated charging mechanisms. In this second edition, a discussion of the new color copiers and a chapter updating the original material have been added. On mastering this material, which is presented in a manner suitable for both the newcomer and the established expert, the reader will have a workingknowledge of the electrophotographic process and a detailed knowledge of its important subsystem, development.

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.

to Electromagnetic Inverse Scattering by K. I. Hopcraft Department of Theoretical Mechanics, University of Nottingham, Nottingham, U. K. and P. R. Smith Department of Electronic and Electrical Engineering, University of Technology, Loughborough, U. K. Springer-Science+Business Media, B. V. Library of Congress Cataloging-in-Publication Data Hopcraft, K. I. An lntroductlon to electromagnetic inverse scattering I by K. I. Hopcraft and P. R. Smith. p. cm. -- (Developments in electromagnetic theory and application; 7) Includes blbliographical references and index. ISBN 978.90.481.4070.1 1. Electromagnetic waves--Scattering. 2. Inverse scattering transform. I. Smith, P. R., Ph. D. II. Title. III. Series: DevelopNents in electromagnetic theory and applications; 7. OC665. S3H67 1992 539. 2--dc20 92-23966 ISBN 978-90-481-4070-1 ISBN 978-94-015-8014-4 (eBook) DOI 10. 1007/978-94-015-8014-4 AH Rights Reserved (c) 1992 Springer Science+Business Media Dordrecht OriginaHy published by Kluwer Academic Publishers in 1992 Softcover reprint of the hardcover Ist edition 1992 No part ofthe material protected by this copyright notice may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording or by any information storage and retrieval system, without written permission from the copyright owner. Contents (;Iossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ix I'reface . . . . . xi 1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 1 What is inverse scattering? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1. 2 Why study inverse scattering? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1. 3 An historical sketch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. 4 How to solve inverse problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Definitions and terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Electromagnetic wave equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ."

Discusses physical, chemical, and nanotemplating synthesis techniques for the production of magnetic nanoparticles. Covers experimental techniques for determination of the macroscopic and microscopic magnetization of nanoparticles. Discusses the role of nanomagnetism in high-density magnetic recording media, nanostructured permanent magnets, MRI imaging enhancement and magnetically guided drug delivery.