Control of the accumulation of non-process elements and organic compounds in pulp mills with bleach filtrate reuse. Milestones and progress, Quarter 9 (July 1--September 30, 1998)

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

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The Tempo and mode(S) of Prebiotic Evolution

International Astronomical Union Colloquium ◽

10.1017/s0252921100014937 ◽

1997 ◽

Vol 161 ◽

pp. 419-429 ◽

Cited By ~ 1

Author(s):

Antonio Lazcano

Keyword(s):

Origin Of Life ◽

Organic Compounds ◽

Biological Evolution ◽

Current Evidence ◽

Early Diversification ◽

Time Period ◽

The Galaxy ◽

History Of ◽

Widespread Phenomenon ◽

The Origin Of Life

AbstractDifferent current ideas on the origin of life are critically examined. Comparison of the now fashionable FeS/H2S pyrite-based autotrophic theory of the origin of life with the heterotrophic viewpoint suggest that the later is still the most fertile explanation for the emergence of life. However, the theory of chemical evolution and heterotrophic origins of life requires major updating, which should include the abandonment of the idea that the appearance of life was a slow process involving billions of years. Stability of organic compounds and the genetics of bacteria suggest that the origin and early diversification of life took place in a time period of the order of 10 million years. Current evidence suggest that the abiotic synthesis of organic compounds may be a widespread phenomenon in the Galaxy and may have a deterministic nature. However, the history of the biosphere does not exhibits any obvious trend towards greater complexity or «higher» forms of life. Therefore, the role of contingency in biological evolution should not be understimated in the discussions of the possibilities of life in the Universe.

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