518 research outputs found

    Cohomology of finite dimensional pointed Hopf algebras

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    We prove finite generation of the cohomology ring of any finite dimensional pointed Hopf algebra, having abelian group of grouplike elements, under some mild restrictions on the group order. The proof uses the recent classification by Andruskiewitsch and Schneider of such Hopf algebras. Examples include all of Lusztig's small quantum groups, whose cohomology was first computed explicitly by Ginzburg and Kumar, as well as many new pointed Hopf algebras. We also show that in general the cohomology ring of a Hopf algebra in a braided category is braided commutative. As a consequence we obtain some further information about the structure of the cohomology ring of a finite dimensional pointed Hopf algebra and its related Nichols algebra.Comment: 36 pages, references adde

    Material studies related to lunar surface exploration. Volume 1 - Lunar soil mechanics and soil properties Final report, 6 Mar. 1967 - 30 Jun. 1968

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    Lunar soil mechanics and properties for structural engineering aspects of lunar spacecraft landings and surface exploratio

    Dcse Estimation and Prediction of Radiation Effects on Aquatic Biota Resulting from Radioactive Releases .from the Nuclear Fuel Cycle*

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    ABSTRACT -NOTICE vepott was rnir . prepared as an accou.T of work S'Cut efponsibuity for the accuracy, completeness « uJulnas of any information, apparatus, product o process disclosed, or represents that its use would not d iht process disclo, p infringe privately owned lights. Aquatic organisms are exposed to radionuclides released to the environment during various steps of the nuclear fuel cycle. Routine releases from these processes are limited in compliance with technical specifications, requirements of federal regulations. These regulations reflect I.C.R.P. recommendations which are designed to provide an environment considered safe for man. It is generally accepted that aquatic organisms will not receive damaging external radiation doses in such environments; however, because of possible bioaccunulation of radionuclides there is concern that aquatic organisms might be adversely affected 'ay internal doses. The objectives of this paper are: (1) to estimate the radiation dose received by aquatic biota from the different processes and determine the major dose-contributing radionuclides, and (2) to assess the impact of estimated doses on aquatic biota. Dose estimates are made by using radionuclide concentration measured in the liquid effiuents of representative facilities. Where measurements of concentrations are rot available, predicted radioactive releases to the aquatic environment are used for dose calculations. Although radioactive releases from reactors used to generate electrical energy have received the most attention, and are the best documented, this evaluation indicates the potential for a greater radiation dose to aquatic biota from the nuclear fuel supply facilities (i.e., mining and milling).. The effects of chronic low-level radiation on aquatic organisms are discussed from somatic and genetic viewpoints. Based on the body of radiobiological evidence accumulated up to the present time, no significant deleterious effects are predicted for populations of aquatic organisms exposed to the estimated dose rates resulting from routine releases from conversion, enrichment, fabrication, reactors and reporcessing facilities. At the doses estimated for milling and mining operations it would be difficult to detect radiation effects on aquatic populations; however, the significance of such radiation exposures to aquatic populations cannot be fully evaluated without further research on effects of chronic low-level radiation
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