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This volume is the fourth in the series of the Proceedings of the College Park Colloquia on Chemical Evolution. These Colloquia, and the resulting Proceedings, are presented in the interest of fostering the impact of the interdisciplinary nature of chemical evolu tion on contemporary scientific thought. vii EDITORS'INTRODUCTION The Fourth College Park Colloquium on Chemical Evolution was held on October 18 - 20, 1978 at the University of Maryland. The meeting, supported by the National Aero nautics and Space Administration and the National Science Foundation, centered on the variable environments, both past and present, in which living organisms have survived, grown, and evolved - the limits of life. Previous colloquia had emphasized the Giant Planets (1974) 1, Early Life during the Precambrian (1975)2 and Comparative Planetology (1976)3. The College Park Colloquia have been noted for the broad interdisciplinary nature of the training and interests of the participants. The fourth meeting was no ex ception with the participation of approximately 85 researchers, representing many academic fields. As with previous meetings, the interdisciplinary approach to the question of the limits of life encouraged the exchange of knowledge and information. A major scientific aspiration is to understand why living systems are restricted to certain environments.
Sommario
Limits to Life at Low Temperatures and at Reduced Water Contents and Water Activities.- Biological Limits of Temperature and Pressure.- Endolithic Microbial Life in Hot and Cold Deserts.- Purification and Properties of Malate Dehydrogenase from the Extreme Thermophile Bacillus Caldolyticus.- The Gas Vacuole: An Early Organelle of Prokaryote Motility?.- Physical Chemistry and Evolution of Salt Tolerance in Halobacteria.- Halophily and Halotolerance in Cyanophytes.- Soil Stabilization by a Prokaryotic Desert Crust: Implications for Precambrian Land Biota.- The Evolution of the Solar 'Constant'.- Ozone, Ultraviolet Flux and Temperature of the Paleoatmosphere.- Atmospheric Constraints on the Evolution of Metabolism.- Archean Photoautotrophy: Some Alternatives and Limits.- Sulphur Isotope Ratios in Late and Early Precambrian Sediments and their Implications Regarding Early Environments and Early Life.- Antiquity and Evolutionary Status of Bacterial Sulfate Reduction: Sulfur Isotope Evidence.- Structural Features of Manganese Precipitating Bacteria.- The Radioracemization of Amino Acids by Ionizing Radiation: Geochemical and Cosmochemical Implications.
