This volume summarizes recent developments in our understanding of active galactic nuclei, including quasars, seyfert galaxies and radio galaxies. The predominant emphasis is put on observational results with information from essentially all wave bands, but important theoretical results are also presented. Among the contributions are discussions of the different types of active galaxies, the nature of the central engine, the wiggly structure of radio jets, the dynamics of the gas in jets, the study of millimeter and extreme ultraviolet regions, and a discussion of the observed continuum of the entire electromagnetic spectrum. The intended readers are professional astronomers and astrophysicists as well as graduate students in this field of research.

The proceedings of this workshop should probably be prefaced with a few words on some of the more confusing jargon. The phrases "Very Low-Mass star" , "VLM star", or simply "VLM" are now used fairly uniformly by as tronomers studying the stars at the bottom of the hydrogen-burning stellar main sequence - unfortunately, however, there is no clear definition as to what constitutes a VLM star. The reader should be warned that VLM stars are variously considered to be stars with; masses less than 0.3M ; masses 0 less than 0.1M ; spectra later than about M6-7; luminosities fainter than 0 Mv = 15; or luminosities fainter than Mbol = 12. The important features of a VLM star, however, would seem to be (1) that it is about as faint as a star can be, and (2) that it still remains a star (ie. it still burns hydrogen) . All of the above criteria, therefore, would seem to qualify an object as a VLM star, and requiring a more stringent definition is probably quibbling.

The 14 papers in this collection discuss recent progress in areas such as mixing in stellar interiors, redistribution and loss of angular momentum, emphasizing in particular the effects of turbulence. An introductory review by E. Schatzman, to whom this volume is dedicated, is followed by three sections: observational facts (surface abundances, stellar rotation, loss of mass and angular momentum, etc.), physical knowledge (mass transport and mixing by waves, turbulent transport, fast dynamo action, etc.), and the interpretation of observations.

Large-scale structures in the universe are becoming ever more important in modern astrophysics. This volume is dedicated to the memory of the late astrophysicist Fritz Zwicky and presents 34 lectures dealing with observational and theoretical aspects of the morphology of the universe. Reports on the distribution, properties and evolution of groups, clusters and superclusters of galaxies, as well as theoretical attempts to explain these findings using such ideas as biased galaxy formation and cold dark matter, are presented here for researchers and students of astronomy and astrophysics.

volume XIX A of IAU Transactions contains the reports by Presidents of Commissions, covering the period July 1981 - June 1984. The topics of IAU Commissions deal with all of contemporary astronomy and the present volume therefore constitutes an exhaustive and unique record of astronomical research during this interval. It is particularly useful for astronomers and other scientists who want to gain an overview of a certain field, not necessarily near their own research area. Each Commission President was requested, by early 1984, to begin prep arations for the compilation of his/her Commission report. All members of Commissions were asked to supply details about their individual research pro grammes. The ensuing, very substantial task of concatenating was undertaken in late 1984 by the Presidents, often supported by a team of authors, all recog nized authorities in their fields. In order to preserve some measure of uni formity - which is in any case very difficult with so many authors - editorial guidelines were sent to Presidents, including the number of pages allotted to each Commission.

When leaving the Victoria airport the day before our Colloquium, I saw a van of the Dunsmuir Lodge marked with big letters which I read as "Alcohol Colloquium". I do often make such blunders because of the global, casual, and careless way in which I read various ads, and checked myself quickly to read it correctly as "Algol Colloquium". Millions of fellow citizens could easily make the same mistake, and no apology could be expected. Even I read and hear the word alcohol more frequently than Algol, although I must say that Algols have given me more pleasure and fewer headaches over the years; in that, however, I may be a singularity, and possibly a pitiful one at that. Being appointed Chairman of the Scientific Organizing Committee, I may be deemed to be a purer" Algolist" than other investigators, although my range of active interests is much broader; and the same is true about all the 28 invited speakers and all the other participants of the Colloquium. Our interest are strongly diversified, but there are several good reasons that brought us together at this Colloquium.

For some time to come, this book should be the main source for research in prominences. It surveys the results of the past years, including the "Hvar Reference Atmosphere", which was developed by a panel as a model for quiescent prominences. The reader will find papers on the formation of and physical conditions in prominences, on magnetic fields, on mass motion and energy flow, and on the prominence-corona interface.

Astronomy is by nature an interdisciplinary activity: it involves mathematics, physics, chemistry and biology. Astronomers use (and often develop) the latest technology, the fastest computers and the most refined software. In this book twenty-two leading scientists from nine countries talk about how astronomy interacts with these other sciences. They describe modern instruments used in astronomy and the relations between astronomy and technology, industry, politics and philosophy. They also discuss what it means to be an astronomer, the history of astronomy, and the place of astronomy in society today.

The Optical Society of America Conference on Applications of High Fields and Short Wavelength Sources, held in Santa Fe, New Mexico, USA, from March 20-22, 1997, was an exceptionally exciting conference. This conference was the seventh in a series of topical con ferences, held every two years, which are devoted to the generation and application of high field and short wavelength sources. The meeting was truly international in scope, with equal participation from both within and outside of the US. In the past two years, there has been dramatic progress in both laser and x-ray coher ent sources, both fundamental and applied. The 1997 meeting highlighted these advances, which are summarized in sections 1 and 2 of this volume. Terawatt-class lasers are now avail able in the UV or at high repetition rates. Michael Perry (LLNL) presented a keynote talk on petawatt class lasers and their applications in inertial confinement fusion, while Jorge Rocca (Colorado State University) presented a keynote talk on tabletop soft-x-ray lasers. Genera tion and measurement techniques are becoming very sophisticated throughout the UV and x ray region of the spectrum, and coherent sources have been extended to wavelengths below 30A. Phase control in the x-ray region is also now possible, and new phase-matching schemes in the UV have been experimentally demonstrated. It is clear that a new field of x-ray nonlin ear optics will deveiop rapidly over the next few years."

ESO's new and exciting telescope, the VLT in Chile, will certainly bring a host of new results in optical astronomy for the years to come. This workshop surveys a large variety of possible observations and the needed instrumentation. It is an exciting overview of front research in astronomy rarely published before. The book covers the whole gamut of optical-IR astronomy from the solar system, search for planets in nearby stars, physics of galactic stars and clusters, galactic structure, structure of nearby galaxies, AGN and quasars, clusters of galaxies, to large structure and cosmology. Furthermore it summarizes the two panel discussions.

The ESO jIAC Workshop on Quasar Hosts was held in Puerto de la Cruz, Tenerife, from 24 to 27 September 1996 in the Conference Centre of the Ca- bildo Insular de Tenerife. The four days of the meeting were filled with fasci- nating new results and interesting discussions, and ranged from the centre of our own galaxy to some of the most distant objects known in the universe. Quasar Host studies are going through an exciting time, and are benefiting from new facilities, including the refurbished HST and the Keck, and from novel techniques, including adaptive optics and deconvolution methods. We also saw the first of hopefully many results from the ISO satellite. These re- sults were presented during the many sessions and discussed in the gardens over coffee, and on the bus during our tour of the Canaries Observatories. We would very much like to thank the secretaries of ESO and lAC, Christina Stoffer, Pamela Bristow, Monica Murphy, Judith de Araoz, and Beatriz Mederos, who we depended on for their expertise and efficiency. Our colleagues on the scientific organising committee, Phil Crane, Bob Fosbury, Marie-Helene Ulrich, Peter Shaver and Jose Rodriguez-Espinosa, deserve considerable thanks for their contributions to the programme. We must also thank the local organising committee, Fernando Cabrera- Guerra, Monica Murphy, Ismael Perez-Fournon, Ana Perez-Garcia, Luis Ramirez-Castro, and Montserrat Villar-Martin, for all their efforts in making sure things ran smoothly on the day.

The purpose of this volume is to present the latest planetary studies of an international body of scientists concerned with the physical and chemical aspects of terrestrial planets. In recent years planetary science has developed in leaps and bounds. This is a result of the application of a broad range of scientific disciplines, particularly physical and chemical, to an understanding of the information received from manned and unmanned space exploration. The first five chapters expound on many of the past and recent observations in an attempt to develop meaningful physical-chemical models of planetary formation and evolution. For any discussion of the chemical processes in the solar nebula, it is important to understand the boundary conditions of the physical variables. In Chapter 1, Saf ranov and Vitjazev have laid down explicitly all the physical constraints and the problems of time-dependence of nebular evolutionary processes. Planetary scientists and students will find in this chapter a collection of astrophysical parameters on the transfer of angular momentum, formation of the disk and the gas envelope, nebular turbulence, physical mixing of particles of various origins and growth of planetesimals. The authors conclude their work with important information on ev olution of terrestrial planets. Although symbols are defined in the text of the article, readers who are not familiar with the many symbols and abbreviations in astrophysical literature will find it useful to consult the Appendix for explanations."

These proceedings are based upon the invited review papers and the research notes presented at the NATO Advanced Research Institute on "Artificial Particle Beams in Space Plasma Studies" held at Geilo, Norway April 21-26, 1981. In the last decade a number of research groups have employed artificial particle beams both from sounding rockets and satellites in order to study various ionospheric and magnetospheric phenomena. However, the artificial particle beams used in this manner have given rise to a number of puzzling effects. Thus, instead of being just a probe for studying the ambient magnetosphere, the artificial particle beams have presented a rich variety of plasma physics problems, in parti ular various discharge phenomena, which in themselves are worthy of a careful study. The experimental studies in space using artificial particle beams have in turn given rise to both theore tical and laboratory studies. In the laboratory experi ments special attention has been paid to the problem of creating spacelike conditions in the vacuum chamber. The theoretical. work has addressed the question of beam plasma-neutral interaction with emphasis on the wave generation and the modified energy distributions of the charged particles. Numerical simulations have been used extensively. With the advent of the Space Shuttle in which several artificial particle beam experiments are planned for the 1980's, there is a growing interest in such experiments. Furthermore, there is a need for coordinating these studies, both in space and in the laboratory."

This book contains the proceedings of the 1989 Crafoord Symposium organized by the Royal Swedish Academy of Sciences. The scientific field for the Crafoord Prize of 1989 was decided in 1988 by the Academy to be Magnetospheric Physics. On September 27,1989 the Academy awarded the 1989 Crafoord Prize to Professor J. A. Van Allen, Iowa City, USA "for his pioneer work in space research, in particular for the discovery of the high energy charged particles that are trapped in the Earth's magnetic field and form the radiation belts -often called the Van Allen belts - around the Earth". The subject for the Crafoord Symposium, which was held on September 28-29 at the Royal Swedish Academy of Sciences in Stockholm, was Magnetospheric Physics, Achievements and Prospects. Some seventy of the world's leading scientists in magnetospheric physics (see list of participants) were invited to the Symposium. The program contained only invited papers. After the ?resentation of the Crafoord Prize Laureate, Prof. J . A. Van Allen, and his specially invited lecture: "Active Experiments in Magnetospheric Physics" follows in these proceedings two papers on the achievements of magnetospheric research hitherto. The main part of the proceedings (8 papers) deal with the main theme of the Symposium: How we shall carry on magnetospheric research in the future. The Symposium was organized by five members of the Academy representing the field of space physics: Lars Block (Stockholm), Rolf Bostrom (Uppsala), Kerstin Fredga (Stockholm), Carl-Gunne Fiilthammar (Stockholm) and Bengt Hultqvist (Kiruna, Chairman).

Astrobiology is one of the hottest areas of current research, reflecting not only impressive advances in the understanding of the origin of life but also the discovery of over 100 extrasolar planets in recent years. This volume is based on a meeting held in 2002 at the Space Telescope Science Institute, which aimed to lay the astrophysical groundwork for locating habitable places in the Universe. Written by leading scientists in the field, it covers a range of topics relevant to the search for life in the Universe, including: cosmology and its implications for the emergence of life, the habitable zone in the Milky Way Galaxy, the formation of stars and planets, the study of interstellar and interplanetary matter, searches for extrasolar planets, the synthesis of organic material in space, and spectroscopic signatures that could be used to detect life. This is an invaluable resource for both professional researchers and graduate students.

Originally published in 1989, this book provides a comprehensive account of how to handle astronomical data. Descriptions of data acquisition, handling, and interpretation are included. The advice starts with chapters on observatories and observations, followed by discussions on the archiving of data and its presentation in the literature. There are many useful suggestions on the nomenclature of astronomical objects, and descriptions of the astronomical catalogues. Three chapters concentrate on databases and astronomical data centres. Finally the author comments on publication and the growth of astronomical data. The clear advice given in this book will be of interest to professional astronomers and graduate students who handle data.

What is unorthodox in this book? Much has happened in the last few years, especially in terms of the somewhat surpris ing rate at which the theories presented herein have been gaining increasing acceptance and support even by the most skeptical professionals. Nevertheless, the purpose of this up-dated Preface is not to tell the biographical and acceptance story behind this book, but to bring together some non-physical and non technical conclusions for those readers who find the physico-mathematical sections of this book too difficult to follow. A secondary purpose is to present here some newer conclu sions, especially in general philosophy and in aesthetics. Yet, the main physico philosophical conclusions presented in this book are not to be summarized here. For that purpose one must tum to the text itself. * * * The theories presented here have been developed in total isolation. They were never presented in "professional conferences," as most current writers do. Whether or not that was important remains to be seen. Hence, all I can state to critics and enthusiastic follow ers alike is the fact that I do not belong to any 'formal discipline', 'pressure group', or 'pro fessional organization'."

The imaging process in stellar interferometers is explained starting from first principles on wave propagation and diffraction. Wave propagation through turbulence is described in detail using Kolmogorov statistics. The impact of turbulence on the imaging process is discussed both for single telescopes and for interferometers. Correction methods (adaptive optics and fringe tracking) are presented including wavefront sensing/fringe sensing methods and closed loop operation. Instrumental techniques like beam combination and visibility measurements (modulus and phase) as well as Nulling and heterodyne interferometry are described. The book closes with examples of observing programmes linking the theory with individual astrophysical programmes.

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Huygens: The Man behind the Principle is the story of the great seventeenth-century Dutch mathematician and physicist Christiaan Huygens (1629-95). This comprehensive biography describes in detail how Huygens arrived at discoveries and inventions that are often wrongly ascribed to Newton. Huygens played a key role in the 'scientific revolution', and the Huygens Principle on the wave theory of light helped establish his reputation. The discovery of Saturn's rings and the invention of the pendulum clock made him so famous that he was invited to be the first director of the French Academy of Science, but his life as director teetered on the edge of powerlessness. Despite Huygens' many achievements no complete biography had previously been published in English. This book gives scientists and historians the opportunity to learn more about all aspects of Huygens' life while bringing his story to a wider audience.

Understanding the formation of objects at all scales in the universe, from galaxy clusters to stars and planets, is a major problem in modern astrophysics, and one of the most exciting challenges of twenty-first century astronomy. Even though they are characterized by different scales, the formation of planets, stars and galaxies share many common physical processes and are rooted in the same underlying domains of physics. This unique reference for graduate students and researchers in astrophysics was the first to cover structure formation on various scales in one volume. This book gathers together extensive reviews written by world experts in physics and astrophysics working in planet, star and galaxy formation, and related subjects. It addresses current issues in these fields and describes the recent observational status and theoretical and numerical methods aimed at understanding these problems.

'Fractal geometry addressesitselfto questions that many people have been asking themselves. It con cerns an aspect of Nature that almost everybody had been conscious of, but could not address in a formal fashion. ' 'Fractal geometry seems to be the proper language to describe the complezity of many very compli cated shapes around us. ' (Mandelbrot, 1990a) 'I believe that fractals respond to a profound un easiness in man. ' (Mandelbrot, 1990b) The catchword fractal, ever since it was coined by Mandelbrot (1975) to refer to a class of abstract mathematical objects that were already known at the turn ofthe 19th century, has found an unprecedented resonance both inside and outside the scientific community. Fractal concepts, far more than the concepts of catastrophe theory introduced a few years earlier, are currently being applied not only in the physical sciences, but also in biology and medicine (Goldberger and West 1987). In the mid-eighties, Kadanoff (1986) asked the question: 'Why all the fuss about /ractals' '. He offered a twofold answer: in the first place, it is 'because of the practical, technological importance of fractal objects'. Indeed he emphasised the relevance of these structures for materials scientists and oil drilling engineers, in search of structures with novel properties, or models for the flow of oil through the soil. His second answer was: 'Because of the intellectual interest of fractals '."

In 1879, while a graduate student under Henry Rowland at the Physics Department of The Johns Hopkins University, Edwin Herbert Hall discovered what is now universally known as the Hall effect. A symposium was held at The Johns Hopkins University on November 13, 1979 to commemorate the lOOth anniversary of the discovery. Over 170 participants attended the symposium which included eleven in vited lectures and three speeches during the luncheon. During the past one hundred years, we have witnessed ever ex panding activities in the field of the Hall effect. The Hall effect is now an indispensable tool in the studies of many branches of condensed matter physics, especially in metals, semiconductors, and magnetic solids. Various components (over 200 million ) that utilize the Hall effect have been successfully incorporated into such devices as keyboards, automobile ignitions, gaussmeters, and satellites. This volume attempts to capture the important aspects of the Hall effect and its applications. It includes the papers presented at the symposium and eleven other invited papers. Detailed coverage of the Hall effect in amorphous and crystalline metals and alloys, in magnetic materials, in liquid metals, and in semiconductors is provided. Applications of the Hall effect in space technology and in studies of the aurora enrich the discussions of the Hall effect's utility in sensors and switches. The design and packaging of Hall elements in integrated circuit forms are illustrated."

Transitions from the innermost shells of iron, especially the K- and L-shelllines, provide a powerful tool for probing the physical characteristics of hot plasmas in X-ray sources. Their strength and purity allow important conclusions to be drawn even with modest energy resolution. They should also help in studying the regions around black holes and neutron stars. In this book the state of the art and themost recent theoretical and experimental observations are presented. The book will be a valuable source for future satellite missions. It addresses both researchers and graduate students in astrophysics.

This is a fair overview of the basic problems in Solar Physics. The authors address not only the physics that is well understood but also discuss many open questions. The lecturers' involvement in the SOHO mission guarantees a modern and up-to-date analysis of observational data and makes this volume an extremely valuable source for further research.