The nonlinear theory of oscillating systems brings new aspects into the study of variable stars. Beyond the comparison of linear periods and the estimate of stability, the appearance and disappearance of possible modes can be studied in detail. While nonlinearity in stellar pulsations is not a very complicated concept, it generally requires extensive and sometimes so phisticated numerical studies. Therefore, the development of appropriate computational tools is required for applications of nonlinear theory to real phenomena in variable stars. Taking trends in variable star studies into consideration, the International Astronomical Union organized a colloquium for the nonlinear phenomena of variable stars at Mito, Japan in 1992. The colloquium served to give an overview of the new frontiers of variable star studies and to encourage further development of this field. The colloquium covered the fundamental theory, interesting observational facts, and the numerical modeling. The publication of the proceedings was somewhat delayed since one of the editors, M. T., was overwhelmed by administrative work. We are sorry that the excellent reviews of Drs. H. :Mori, M. Sano, and K. Makishima cannot be found in the proceedings. We also miss the summary given by Dr. W. W. Dziembowski. Throughout the editing procedure Dr. Y. Tanaka of Ibaraki University kindly helped us. Because of the unfortunate delay of the publication~ the significance of several papers may be affected. Even so, we believe that the papers are useful to variable star researchers because of their scientific importance.

Long-term monitoring is of fundamental significance in solving many important problems in astrophysics and, furthermore, has unequalled value in extending observational runs with small telescopes for the education of young astronomers in order to teach them how to secure high-quality observational data over many years. The Impact of Long-Term Monitoring on Variable Star Research contains reports based on the analysis of data collected in the visible, IR and radio measurement ranges, as well as the design and history of well known photometric systems. Though the reporting of novel results forms an important part of the book, there are also reports of eight discussion sessions covering more general areas, such as extinction monitoring, the problems of archival storage of astronomical data, service observation, the role played by long-term monitoring in graduate teaching and thesis supervision, the interplay between the great observational effort and theory, the contribution of LTM to new knowledge of fundamental data, and the increasing decommissioning of telescopes of modest aperture.

Massive stars occupy an exceptional place in general astrophysics. They trigger many if not all of the important processes in galactic evolution whereas due to their intrinsic brightness, they offer the (only until now) possibility to study the stellar content and stellar behaviour in distant galaxies. The last, say, 25 years, massive stars have been the subject of numerous meetings discussing the influence of massive stars on population synthesis, the number distribution of different types of massive stars, the LBV phenomenon, WR stars, X-ray binaries, stellar winds in massive stars, chemical pecularities in massive stars, supernova explosions of massive stars and the important SN1987A event, the influence of massive stars and chemical evolution of galaxies. It is clear that without a theory of stellar evolution, the study of these topics loses a lot of its significance. Massive star evolution therefore got a chance in these meetings, but rarely as a prime subject. The state of the art, the physical processes and the uncertainties in stellar evolution were barely touched. Even more, the influence of close binaries in all these massive star meetings slowly disappeared the last, say, 13 years without any scientific justification, although a significant fraction of stars occurs in close binaries with periods small enough so that both components will interact during their evolution. Denying the binaries or not discussing their influence on results and conclusions, makes the latter very uncertain or even completely unreliable.

The pilot boat just moved away and'its lights are already fading towards the coast of Northeastern Queensland over which Saturn is going to set. There is still quite some time to go before dawn. The big ship has now regained her cruise speed following its roughly northwesterly route in the South Coral Sea along the chain of nearby reefs. Few people are around at this time, except a dozen early birds sharing some 'shipshaping' exercise on the top deck and taking advantage of the relative coolness of the night. On my way down to the stateroom, I cannot but stop once more in front of that elegant composition by British artist Brigid Collins (1963-) hanging in the monumental staircase between Decks 7 and 8. That piece 2 of art, a 1.8x 1.8m oil on canvas plus collage entitled Berinl in honour of the Danish explorer, gathers together many navigation-related themes of the time: Suns, Moons, planets, sky maps, astrolabes, small telescopes, as well as drawings, diagrams and charts of all kinds. It is somehow a digest of how astronomical information was then collected, made available, and used.

It is with great joy that we present a collection of essays written in honour of Jayant Vishnu Narlikar, who completed 60 years of age on July 19, 1998, by his friends and colleagues, including several of his for mer students. Jayant has had a long research career in astrophysics and cosmology, which he began at Cambridge in 1960, as a student of Sir Fred Hoyle. He started his work with a big bang, expounding on the steady state theory of the Universe and creating a new theory of gravity inspired by Mach's principle. He also worked on action-at-a-distance electrodynamics, inspired by the explorations of Wheeler, Feynman and Hogarth in that direction. This body of work established Jayant's rep utation as a bold and imaginative physicist who was ever willing to take a fresh look at fundamental issues, undeterred by conventional wis dom. This trait, undoubtedly inherited from his teacher and mentor, has always remained with Jayant. It is now most evident in his untir ing efforts to understand anomalies in quasar astronomy, and to develop the quasi-steady state cosmology, along with a group of highly distin guished astronomers including Halton Arp, Geoffrey Burbidge and Fred Hoyle. In spite of all this iconoclastic activity, Jayant remains a part of the mainstream; he appreciates as well as encourages good work along conventional lines by his students and colleagues. This is clear from the range of essays included in this volume, and the variety and distribution of the essayists.

th The 4 ESO CCO Workshop, Optical Detectors for Astronomy, was held during September 13-16, 1999 at its usual location, the headquarters of the European Southern Observatory in Garching, Germany. We prefer to remember this workshop as a "meeting of friends", who came to Garching to visit ESO and to present their work, rather than a formal meeting. Based on our experience with the 1996 ESO CCO workshop, we deliberately put emphasis on creating an environment that encouraged the participants to stay together and informally exchange ideas. These informal events began with a tour of the BWM auto factory and continued with a reception at "SchloB Beletic", the conference dinner at a real SchloB of the Bavarian International School (where the participants enjoyed basket, baseball, table soccer, rock climbing and eventually dancing) and concluded with a tour of the Paulaner Brewery and dinner at the Seehaus in the Englisher Garten. The lunch "Biergarten", adjacent to the poster session area, was a daily meeting point. The result was a good mixture of excellent presentations and posters, collected in these Proceedings, and many occasions for people to get in touch and to have fun together, as witnessed by the selection of workshop pictures that we randomly placed between papers. This book contains a special contribution.

This NATO AS was the third in the series of Advanced Study Institutes on neutron stars, which started with 'Timing Neutron Stars', held in Qe me near izmir, Turkey (April 1988), followed by 'Neutron Stars, an Interdis ciplinary Subject', held in Agia Pelagia on the island of Crete (September 1990). The first school centered on our main observational access to neu tron stars, i. e. the timing of radio pulsars and accretion powered neutron stars, and on what timing of neutron stars teaches us of their structure and environment. The second school had as its theme the interplay between diverse areas of physics which find interesting, even exotic applications in the extreme conditions of neutron stars and their magnetospheres. As the field has developed, with the number of observed neutron stars rapidly in creasing, and our knowledge of many individual neutron stars getting deeper and more detailed, an evolutionary picture of neutron stars has started to emerge. This led us to choose 'The Lives of the Neutron Stars' as the uni fying theme of this third Advanced Study Institute on neutron stars. Different types of neutron star activity have been proposed to follow one another in stages during the lives of neutron stars in the same basic population; the evolutionary connection between low-mass X-ray binaries and millisecond radio pulsars is perhaps the prime example."

This volume contains the lectures presented at the second course of the International School of Space Chemistry held in Erice (Sicily) from October 20 - 30 1991 at the "E. Majorana Centre for Scientific Culture." The course was attended by 58 participants from 13 countries. The Chemistry of Life's Origins is well recognized as one of the most critical subjects of modem chemistry. Much progress has been made since the amazingly perceptive contributions by Oparin some 70 years ago when he first outlined a possible series of steps starting from simple molecules to basic building blocks and ultimate assembly into simple organisms capable of replicating, catalysis and evolution to higher organisms. The pioneering experiments of Stanley Miller demonstrated already forty years ago how easy it could have been to form the amino acids which are critical to living organisms. However we have since learned and are still learning a great deal more about the primitive conditions on earth which has led us to a rethinking of where and how the condition for prebiotic chemical processes occurred. We have also learned a great deal more about the molecular basis for life. For instance, the existence of DNA was just discovered forty years ago.

Living material contains about twenty different sorts of atom combined into a set of relatively simple molecules. Astrobiologists tend to believe that abiotic mater ial will give rise to life in any place where these molecules exist in appreciable abundances and where physical conditions approximate to those occurring here on Earth. We think this popular view is wrong, for it is not the existence of the building blocks of life that is crucial but the exceedingly complicated structures in which they are arranged in living forms. The probability of arriving at biologically significant arrangements is so very small that only by calling on the resources of the whole universe does there seem to be any possibility of life originating, a conclusion that requires life on the Earth to be a minute component of a universal system. Some think that the hugely improbable transition from non-living to living mat ter can be achieved by dividing the transition into many small steps, calling on a so-called 'evolutionary' process to bridge the small steps one by one. This claim turns on semantic arguments which seek to replace the probability for the whole chain by the sum of the individual probabilities of the many steps, instead of by their product. This is an error well known to those bookies who are accustomed to taking bets on the stacking of horse races. But we did not begin our investigation from this point of view.

The Third Microquasar Workshop (or the 'Fifth' Workshop on Galactic Relativ istic Jet Sources), was held in Granada, Andalucia (Spain) on 11-13 September 2000. The aim of this workshop in Granada, following the previous Microquasar Workshops in Greenbelt (1997) and Paris (1998) and the Workshops on galactic sources with relativistic jets in Jodrell Bank (1996) and Milton Keynes (1998), was to focus on the theoretical and observational aspects of microquasars. The study of microquasars, the sources in our Galaxy displaying powerful re lativistic jets, is a rapidly advancing field in astrophysics. The new instrumentation on ground (MERLIN, SCUBA, VLA, VLT) and aboard satellites (ASCA, BSAX, ISO, IXAE and RXTE) has provided important results, and much more is expected to come from Chandra and XMM-Newton. In the further future, powerful instru mentation will come online in the sub-mm (ALMA) and gamma-rays (INTEG RAL), extending our coverage to important regions for the study of microquasars. Energy transport via relativistic jets is one of the most important physical mechan isms taking place in compact objects. Large efforts have been devoted to properly understand the disk-jet connection, and even the effects of rotation or magnetic fields. Several new important advances have been made recently, both from the point of view of the theoretical treatment of jets and the different new observational tests.

In recent years aperture synthesis and interferometry have become very powerful tools in radioastronomy. Investigation of distant galaxies, for example, have revealed structures with sizes of less than a kiloparsec. In general, the study of galaxies has benefited from the great power of these techniques. Radar applications have also dramatically increased their quality by using the interferometry principle. Tracking and airborne radar can now determine position and velocity of objects with a much higher accuracy. This book describes in the first six, short chapters the basics of interferometry and aperture synthesis. The following two, long chapters treat the aspects of radioastronomical interferometers and radar applications of interferometry in great detail. The text offers readers a very good opportunity to familiarize themselves with the mathematical background of these very complex techniques. For researchers and students in radioastronomy and electrical engineering.

It is now a well established tradition that every four years, at the end of winter, a group of "celestial mechanicians" from all over the world gather at the "Alpen gasthof Peter Rosegger" in the Styrian Alps (Ramsau, Austria). This time the colloquium was held from March 17 to March 23, 1996 and was devoted to the Dynamical Behaviour of our Planetary System. The papers covered a large range of questions of current interest: theoretical questions (re- nances, universal properties, non integrability, transport, ... ) and questions about numerical tools ( symplectic maps, indicators of chaos, ... ) were particularly well represented; the never ending problem of the sculpting of the asteroid belt was also qui te popular. You will find in the following pages a pot-pourri of what we listen to; you will miss of course the diversity of accents with which the tunes were delivered: from China, from Japan, from Brazil, from the United-States of America and from all over Europe, East and West. Let us not forget that the comet 199682 (Hyakutake) came to visit us; many an evening was spent on the deck of the Alpengasthof contemplating this celestial visitor who liked to play hide-and-seek behind the spruce trees.

This volume contains the proceedings of the meeting entitled, "The IGM/Galaxy Connection: The Distribution of Baryons at z = 0. " The meeting was held August 8 -10 at the National Center for Atmospheric Research (NCAR) located in Boulder, Colorado on the foothills of the Rocky Mountains (see conference photo). We organized this meeting because we felt it was time to address the link between galaxies and the intergalactic medium at low redshift. In this vein, we posed several questions to the conference participants: Where are the baryons in the local universe and in what phase do they reside? What signatures of galaxy evolution have been imprinted on the IGM? What percentage of intergalactic gas is left from the galaxy formation process? What does the distribution of baryons at z = 0 tell us about the early universe? The conference was an overwhelming success with lots of friendly interaction and discussion among the participants. At lunch we were treated to splendid views from the NCAR terrace and discussions rang ing from the importance of the LSR, GSR, and LGSR velocity frames to how long the desserts would last with 90 astronomers and the hot Boul der sun. From an inventory of the baryons, to the associations between galaxies and Lya absorbers, to the mechanisms by which galaxies obtain and lose gas, the conference covered many topics. The results of these endeavors are contained in these pages and eloquently summarized by Chris Impey.

Der bekannte Astronom Karl Schwarzschild (1873-1916) gilt als der Begrunder der Astrophysik und als hervorragender Forscher mit einer erstaunlichen Bandbreite seiner Interessen. Arbeiten zur Himmelsmechanik, Elektrodynamik und Relativitatstheorie weisen ihn als vorzuglichen Mathematiker und Physiker auf der Hohe seiner Zeit aus. Untersuchungen zur Photographischen Photometrie, Optik und Spektroskopie zeigen den versierten Beobachter, der sein Messinstrumentarium beherrscht, und schliesslich arbeitete Schwarzschild als Astrophysiker an Sternatmospharen, Kometen, Struktur und Dynamik von Sternsystemen. Die in seinem kurzen Leben entstandene Fulle an wissenschaftlichen Arbeiten ist in drei Banden der Gesamtausgabe gesammelt, erganzt durch biographisches Material, Annotationen von Fachleuten und einen Essay des Nobelpreistragers S. Chandrasekhar."

The success of the two first Alexander von Humboldt Colloquia on Celestial Mechanics (March 1984 and March 1988) encouraged us to meet again this year from March 29 to April 4, 1992 in the " Alpengasthof Peter Rosegger"" in the Styrian Alps (Ramsau, Austria). This time the colloquium was devoted to the "Qualitative and Quantitative behaviour of Planetary Systems." The papers covered a large range of questions of current interest from the behaviour of dust particles to the stability of the Solar System as a whole, without forgetting the motion of Asteroids and their classification into families. KAM theory, chaotic motions, resonances, Lyapunov characteristic exponents, perturbation theory, numerical integration were - of course - on the menu every day, served with sauces and accents from various part of the world: from China, from Brazil, from the United States and from all over Europe. To be able to organize this - now well established - meeting, we have to thank primarily the munificence of the Austrian Ministry of Science, furthermore the Steiermarkischen Wissenschafts- und Landesfonds and the Osterreichische Nationalbank for financial support. Also, the Osterreichische Forschungsgemein schaft and the University of Vienna made it possible to invite participants to this meeting from abroad. Support in form of "Tagungsunterlagen" was given by the Creditanstalt-Bankverein in Vienna and coffee during the whole meeting time was donated by Homig-Kaffee Graz."

In recent years there has been a steadily increasing cross-fertilization between cosmology and particle physics, on both the theoretical and experimental levels. Particle physics has provided new experimental data from the big accelerators in operation, and data from space satellites are accumulating rapidly. Cosmology is still one of the best laboratories for testing particle theory. The present work discusses such matters in the context of inflation, strings, dark matter, neutrinos and gravitational wave physics in the very early universe, field theory at the Planck scale, and high energy physics. A particular emphasis has been placed on a new topology for spatial infinity, on the relation between temperature and gravitational potential, a canonical formulation of general relativity, the neutrino mass, spin in the early universe, the measurement of gravity in the 10--100 m range, galaxy--galaxy and cluster--cluster correlation, black holes, string theory and string/string duality. The work also presents a beautiful review of high energy elementary particle physics, treating the meaning, status and perspectives of unification and standard model gauge couplings.

This essential and highly-illustrated guide is for anyone taking their first steps in observational astronomy. It shows what you can expect to see, helping you get the most from your equipment. This unique book gives amateurs the guidance and assurance they need to become more proficient observers.

The proceedings of the international conference held in honor of Lodewijk Woltjer, focus on the physics, origin and space distribution of AGNs and quasars and their relationship to the environment, a very wide subject which has attracted much of Lodewijk Wolter's research interest. A number of lectures were also dedicated to reviewing the recent observational advances and those that may be attained by the introduction of new and powerful astronomical instrumentation both from the ground and from space, in recognition of the central role played by L. Woltjer in the promotion of the ESO VLT and of his involvement in shaping ESA's space programme Horizon 2000+.

Infrared astronomy has undergone an enormous revolution during the last decade. Despite the great technical difficulties of building detectors in a cryogenic environment, the scientific advances in infrared astronomy have been astounding. In the near future many more advances can be expected from still newer developments in telescope and detector designs. High quality detector arrays and passively cooled telescopes are very promising techniques for achieving considerably larger apertures. This volume contains the refereed papers from the workshop on 'Next Generation Infrared Observatory', dealing with all new aspects of future infrared telescopes.

This NATO Advanced Study Institute course provided an updated understanding, from a fundamental and deep point of view, of the progress and current problems in the early universe, cosmic microwave background radiation, large-scale struc ture, dark matter problem, and the interplay between them. Emphasis was placed on the mutual impact of fundamental physics and cosmology, both at the theo retical and experimental or observational levels, within a deep and well defined programme, and a global unifying view, which, in addition, provides of careful inter-disciplinarity. In addition, each course of this series introduced and promoted topics or sub jects which, although not of a purely astrophysical or cosmological nature, were of relevant physical interest for astrophysics and cosmology. Deep understanding, clarification, synthesis, and careful interdisciplinarity within a fundamental physics framework, were the main goals of the course. Lectures ranged from a motivation and pedagogical introduction for students and participants not directly working in the field to the latest developments and most recent results. All lectures were plenary, had the same duration, and were followed by a discus sion. The course brought together experimentalists and theoreticans physicists, astro physicists and astronomers from a wide variety of backgrounds, including young scientists at the post-doctoral level, senior scientists and advanced graduate stu dents as well.

Minor bodies in the Solar System, though representing only a small fraction of the mass in the Solar System, may well play a fundamental role in terrestrial evolution. This book contains investigations of the dynamics and physics of comets, asteroids and meteor streams, and the rather controversial topic of periodic phenomena in the Solar System as signified by geological records, together with several associated developments in celestial dynamics. All these problems are interwoven. This book makes a contribution towards unravelling the nature of the interactions between the Earth and its celestial environment.

The genesis of IAU Colloquium 182, 'Sources and scintillations: refraction and scattering in radio astronomy,' can be traced to the desire, on the one hand, of Beijing Astronomical Observatory radio astronomers to organize a conference which would highlight the need for high sensitivity - as a way ofpromoting their own project to build the world's largest telescope (FAST) - and to a suggestion from Ron Ekers on the other. During a discussion with the two SOC co-chairs (as they then were not) in January 1999 in Epping, Ron noted the success ofa meeting on 'radio seeing' in Beijing in 1989, and wondered whether the time might not be ripe to organize another conference devoted to radio propagation. This set the ball rolling, and with enthusiastic input from SOC members, a successful application was made to the IAU. Later, the URSI also agreed to co-sponsor the meeting. From April 17-21, 2000, over 80 astronomers from a dozen countries met in Guiyang, China, to discuss the latestexciting results and theoretical ideas on radio propagation through interstellar, intergalactic and interplanetary space. These pro ceedings include almost all (95%) ofthe oral presentations given at the conference. In addition to the 52 talks presented during 5 days of the Colloquium, Ron Ekers gave a fine summary at the end to tie things up. There were also poster sessions where some twenty papers were displayed. Besides the scientific sessions, the LOC had organized a program for spouses and otheraccompanying persons.

The original plans for a meeting to celebrate the second centenary of the As tronomical Observatory of Palermo were for a celebration with a double character. The gathering was to have both a historical character, appropriate for a bicenten nial, and a technical character, to note and chronicle the new phase of the history of the Observatory, which has prospered in parallel with the development of this fairly recent topic in astronomical research, the physics of stellar and solar coronae. After the untimely death of the Observatory's Director, Giuseppe S. Vaiana (Pippo to his many friends), a number of colleagues and friends insisted that the celebration should nevertheless be held and should be dedicated to this farsighted scientist who stimulated the development of coronal physics from the early x-ray observations of the solar corona to the recognition of coronae as an observable feature of nearly all stars. This memorial dedication did not change the character of the meeting, which was held in Palermo from 22 to 26 June 1992; as his contributions are very alive in the papers presented at the meeting and collected here, Pippo Vaiana has certainly achieved his place in the history of Astronomy."

Robotic technology offers two potential benefits for future space exploration. One benefit is minimizing the risk that astronauts face. The other benefit is increasing their productivity. Realizing the benefits of robotic technology in space will require solving several problems which are unique and now becoming active research topics. One of the most important research areas is dynamics, control, motion and planning for space robots by considering the dynamic interaction between the robot and the base (space station, space shuttle, or satellite). Any inefficiency in the planning and control can considerably risk by success of the space mission. Space Robotics: Dynamics and Control presents a collection of papers concerning fundamental problems in dynamics and control of space robots, focussing on issues relevant to dynamic base/robot interaction. The authors are all pioneers in theoretical analysis and experimental systems development of space robot technology. The chapters are organized within three problem areas: dynamics problems, nonholonomic nature problems, and control problems. This collection provides a solid reference for researchers in robotics, mechanics, control, and astronautical science.

The first presentation of the novel interdisciplinary optical remote sensing technique for various ionized diluted media, based on the collisional polarization of the spectoral emission. The book provides a methodology of the impact spectropolarimetic sensing of many solutions to many practical diagnostic problems.