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.

Stellar pulsations provide a complex system in stars. This complexity is studied by analyzing the non-sinusoidal, semi-regular, or irregular light curves. This unique volume summarizes the application of recent theoretical results obtained from stellar pulsation studies. In addition, the latest developments in hydrodynamic simulations are discussed. A historical sketch of the study of beat Cepheids, first known for their variable amplitudes, is given as an introduction to the book. This introduction clearly demonstrates how complicated the study of variable stars can be, and therefore challenges and invites the reader to study the entire book.

Editing the proceedings of a scientific meeting is not an easy task. Sometimes people who give an excellent talk do not send the manuscript by the deadline. However, this time, thanks to the punctuality of all the participants, we have this excellent volume for the workshop on mass losing pulsating stars and their circumstellar matter prepared in time. Almost all of the oral presentations including the summary are collected in this volume. We regret that we cannot put in this volume a few posters that we failed to receive before the editorial work. The workshop was planned as a small meeting with less than fifty attendants because the city of Sendai was far from the most of the active institutions. However, the number of submitted papers exceeded the SOC's expectation; many interesting contributions had to be scheduled in the poster session. Still, the oral sessions were so tight that many participants might have felt frustrated for the shortage of discussions. The organizers of the workshop have to apologize to the attendants for the inconvenience caused from such a happy underestimate about the size of the workshop.

How can the interior of the Sun, white dwarfs and other stars be studied by stellar seismology? What can Doppler imaging tell us about high-degree pulsations? What impact are CCD and infrared observations having on extending the Cepheid and RR Lyrae distance scale? And how are other classes of pulsators providing independent checks of the distance scale? These and many other critical questions are answered in this timely review of the dramatic advances made in pulsating star research in the last decade. This survey collects together more than thirty comprehensive reviews and over one hundred summaries of research papers from the 139th IAU Colloquium, held in Victoria, British Columbia. Together these cover all aspects of recent developments in the field of variable star research and preview some of the exciting advances anticipated for the next decade. This volume provides an essential review for graduate students and researchers.

The 4th Experimental Chaos Conference was a forum for members of the scientific and engineering communities to discuss recent developments in, and techniques of, experimental nonlinear dynamics. The focus of this important conference was on actual realizations of nonlinear and chaotic systems. The latest developments in applications of nonlinear dynamics and chaos were presented, the requirement being that all presentations were actually implemented in experiments or devices. The areas covered were spatio-temporal patterns, optical chaos, biological dynamics, communication and synchronization, control of chaotic systems, mechanical dynamics, fluid dynamics, quantum chaos, and chaotic condensed matter systems.

This book provides a survey of the basic ideas of the cellular automaton (CA) modelling environment, emphasising the relevance of this framework to astrophysical applications. It contains introductory level lectures on lattice gases, and on CA turbulence, diffusion-reaction processes, percolation and self-organised criticality. Further, it gives a variety of astrophysical applications, including stellar oscillations, galactic evolution, distribution of luminous matter in the universe, etc.