This volume contains the proceedings of the workshop held in March 1990 at Austin, Texas on Self-Organization, Emerging Properties and Learning. The workshop was co-sponsored by NATO Scientific Affairs Division, Solvay Institutes of Physics and Chemistry, the University of Texas at Austin and IC2 Institute at Austin. It gathered representatives from a large spectrum of scientific endeavour. The subject matter of self-organization extends over several fields such as hydrodynamics, chemistry, biology, neural networks and social sciences. Several key concepts are common to all these different disciplines. In general the self-organization processes in these fields are described in the framework of the nonlinear dynamics, which also governs the mechanisms underlying the learning processes. Because of this common language, it is expected that any progress in one area could benefit other fields, thus a beneficial cross fertilization may result. In last two decades many workshops and conferences had been organized in various specific fields dealing with self-organization and emerging properties of systems. The aim of the workshop in Austin was to bring together researchers from seemingly unrelated areas and interested in self-organization, emerg{ng properties and learning capabilities of interconnected multi-unit systems. The hope was to initiate interesting exchange and lively discussions. The expectations of the organiziers are materialized in this unusual collection of papers, which brings together in a single volume representative research from many related fields. Thus this volume gives to the reader a wider perspective over the generality and ramifications of the key concepts of self organization.

This volume contains the proceedings of the workshop held in March 1990 at Austin, Texas on Self-Organization, Emerging Properties and Learning. The workshop was co-sponsored by NATO Scientific Affairs Division, Solvay Institutes of Physics and Chemistry, the University of Texas at Austin and IC2 Institute at Austin. It gathered representatives from a large spectrum of scientific endeavour. The subject matter of self-organization extends over several fields such as hydrodynamics, chemistry, biology, neural networks and social sciences. Several key concepts are common to all these different disciplines. In general the self-organization processes in these fields are described in the framework of the nonlinear dynamics, which also governs the mechanisms underlying the learning processes. Because of this common language, it is expected that any progress in one area could benefit other fields, thus a beneficial cross fertilization may result. In last two decades many workshops and conferences had been organized in various specific fields dealing with self-organization and emerging properties of systems. The aim of the workshop in Austin was to bring together researchers from seemingly unrelated areas and interested in self-organization, emerg{ng properties and learning capabilities of interconnected multi-unit systems. The hope was to initiate interesting exchange and lively discussions. The expectations of the organiziers are materialized in this unusual collection of papers, which brings together in a single volume representative research from many related fields. Thus this volume gives to the reader a wider perspective over the generality and ramifications of the key concepts of self organization.

will probably be clarified by the continued cooperative efforts of scientists such as those in the group that met in Berlin last September. The staff of Dahlem Konferenzen is responsible for making the meeting of this group memorably pleasant and pleasantly mem- orable. Dr. Bernhard's gifts of charm, organizational skill, and administrative toughness assured that the conference was run elegantly, smoothly, and decisively, even down to the choice of editors for this volume. Marie Cervantes-Waldmann performed minor miracles extracting manuscripts gently but persistently from the authors and in turning the typescripts into a book. The other staff members of Dahlem Konferenzen were unfailingly helpful even under trying circumstances. They will be well rememberedbyall who were fortunate enough to be asked to Berlin for the first week in September, 1980. Mineral Deposits and the Evolution of the Biosphere, eds. H. D. Holland and M. Schidlowski, pp. 5-30. Dahlem Konferenzen, 1982. Berl in, Heidelberg, New York: Springer-Verlag. Microbial Processes in the Sulfur Cycle Through Time H. G. TrUper Institut f. Microbiologie, Rheinische Friedrich-Wilhelms-Universitat, 5300 Bonn 1, F. R. Germany Abstract. Two microbial processes are involved in the sulfur cycle of the earth's biosphere: anoxic dissimilatory sulfur oxidation by phototrophic bacteria and dissimilatory sulfate reduction by sulfate-reducing bacteria. In the presence of oxygen at chemoclines and redoxclines dissimilatory sulfur oxidation by chemolithotrophic bacteria (Thiobacillus, Beg- giatoa, and others) occurs. In addition, dissimilatory sulfur reducing bacteria participate in the sulfur cycle.