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  • 1
    Publication Date: 2011-06-24
    Description: Author(s): P. Talou, B. Becker, T. Kawano, M. B. Chadwick, and Y. Danon Prompt fission neutrons following the thermal and 0.5 MeV neutron-induced fission reaction of 239 Pu are calculated using a Monte Carlo approach to the evaporation of the excited fission fragments. Exclusive data such as the multiplicity distribution P ( ν ) , the average multiplicity as a function of fr... [Phys. Rev. C 83, 064612] Published Thu Jun 23, 2011
    Keywords: Nuclear Reactions
    Print ISSN: 0556-2813
    Electronic ISSN: 1089-490X
    Topics: Physics
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  • 2
    Publication Date: 2012-05-02
    Description: Author(s): S. Kunieda, R. C. Haight, T. Kawano, M. B. Chadwick, S. M. Sterbenz, F. B. Bateman, O. A. Wasson, S. M. Grimes, P. Maier-Komor, H. Vonach, T. Fukahori, and Y. Watanabe Neutron reactions that produce α particles have been investigated experimentally and analyzed by reaction model calculations for incident neutron energies from threshold to 150 MeV on elemental chromium and iron. The cross sections were measured at the Los Alamos Neutron Science Center by direct obs... [Phys. Rev. C 85, 054602] Published Tue May 01, 2012
    Keywords: Nuclear Reactions
    Print ISSN: 0556-2813
    Electronic ISSN: 1089-490X
    Topics: Physics
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  • 3
    Publication Date: 2015-09-17
    Description: Multicellular assemblages of microorganisms are ubiquitous in nature, and the proximity afforded by aggregation is thought to permit intercellular metabolic coupling that can accommodate otherwise unfavourable reactions. Consortia of methane-oxidizing archaea and sulphate-reducing bacteria are a well-known environmental example of microbial co-aggregation; however, the coupling mechanisms between these paired organisms is not well understood, despite the attention given them because of the global significance of anaerobic methane oxidation. Here we examined the influence of interspecies spatial positioning as it relates to biosynthetic activity within structurally diverse uncultured methane-oxidizing consortia by measuring stable isotope incorporation for individual archaeal and bacterial cells to constrain their potential metabolic interactions. In contrast to conventional models of syntrophy based on the passage of molecular intermediates, cellular activities were found to be independent of both species intermixing and distance between syntrophic partners within consortia. A generalized model of electric conductivity between co-associated archaea and bacteria best fit the empirical data. Combined with the detection of large multi-haem cytochromes in the genomes of methanotrophic archaea and the demonstration of redox-dependent staining of the matrix between cells in consortia, these results provide evidence for syntrophic coupling through direct electron transfer.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McGlynn, Shawn E -- Chadwick, Grayson L -- Kempes, Christopher P -- Orphan, Victoria J -- England -- Nature. 2015 Oct 22;526(7574):531-5. doi: 10.1038/nature15512. Epub 2015 Sep 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA. ; Exobiology Branch, National Aeronautics and Space Administration Ames Research Center, Moffett Field, California 94035, USA. ; Control and Dynamical Systems, California Institute of Technology, Pasadena, California 91125, USA. ; SETI Institute, Mountain View, California 94034, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26375009" target="_blank"〉PubMed〈/a〉
    Keywords: Anaerobiosis ; Archaea/cytology/*metabolism ; Cytochromes/genetics/metabolism/ultrastructure ; Deltaproteobacteria/cytology/*metabolism ; Diffusion ; Electron Transport ; Genome, Archaeal/genetics ; Genome, Bacterial/genetics ; Heme/metabolism ; Methane/*metabolism ; Microbiota/physiology ; Models, Biological ; Molecular Sequence Data ; *Single-Cell Analysis ; Sulfates/metabolism ; *Symbiosis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2016-02-26
    Description: The oxidation of methane with sulfate is an important microbial metabolism in the global carbon cycle. In marine methane seeps, this process is mediated by consortia of anaerobic methanotrophic archaea (ANME) that live in syntrophy with sulfate-reducing bacteria (SRB). The underlying interdependencies within this uncultured symbiotic partnership are poorly understood. We used a combination of rate measurements and single-cell stable isotope probing to demonstrate that ANME in deep-sea sediments can be catabolically and anabolically decoupled from their syntrophic SRB partners using soluble artificial oxidants. The ANME still sustain high rates of methane oxidation in the absence of sulfate as the terminal oxidant, lending support to the hypothesis that interspecies extracellular electron transfer is the syntrophic mechanism for the anaerobic oxidation of methane.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Scheller, Silvan -- Yu, Hang -- Chadwick, Grayson L -- McGlynn, Shawn E -- Orphan, Victoria J -- New York, N.Y. -- Science. 2016 Feb 12;351(6274):703-7. doi: 10.1126/science.aad7154.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26912857" target="_blank"〉PubMed〈/a〉
    Keywords: Anaerobiosis ; *Carbon Cycle ; Electron Transport ; Geologic Sediments/microbiology ; Methane/*metabolism ; Methanosarcinales/classification/genetics/*metabolism ; Molecular Sequence Data ; Oxidation-Reduction ; Phylogeny ; RNA, Archaeal/classification/genetics ; Seawater/microbiology ; Sulfates/*metabolism ; Sulfur-Reducing Bacteria/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2016-12-28
    Description: Author(s): P. Talou, T. Kawano, I. Stetcu, J. P. Lestone, E. McKigney, and M. B. Chadwick The emission of prompt fission γ rays within a few nanoseconds to a few microseconds following the scission point is studied in the Hauser-Feshbach formalism applied to the deexcitation of primary excited fission fragments. Neutron and γ -ray evaporations from fully accelerated fission fragments are … [Phys. Rev. C 94, 064613] Published Thu Dec 22, 2016
    Keywords: Nuclear Reactions
    Print ISSN: 0556-2813
    Electronic ISSN: 1089-490X
    Topics: Physics
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  • 6
    Publication Date: 2019-06-28
    Description: This paper describes an algorithm for the high accuracy computation of some statistical quantities of the magnitude of a random trajectory correction maneuver (TCM). The trajectory correction velocity increment Delta V is assumed to be a three-component random vector with each component being a normally distributed random scalar having a possibly nonzero mean. Knowledge of the statitiscal properties of the magnitude of a random TCM is important in the planning and execution of maneuver strategies for deep-space missions such as Galileo. The current algorithm involves the numerical integration of a set of differential equations. This approach allows the computation of density functions for specific Delta V magnitude distributions to high accuracy without first having to generate large numbers of random samples. Possible applications of the algorithm to maneuver planning, planetary quarantine evaluation, and guidance success probability calculations are described.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 86-2061
    Format: text
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  • 7
    Publication Date: 2019-07-13
    Description: In January of 1982 the United States will launch Galileo, the first space mission designed to perform an intensive tour of the Galilean satellites of Jupiter. This paper discusses the results of preliminary maneuver strategy studies for typical interplanetary and orbital phases of the Galileo mission. These studies include the effects of maneuver placement and various linear control algorithms on propellant consumption as determined by Monte Carlo analysis. Estimates of total propellant required for various probabilities of mission success are also given.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 78-1393 , Astrodynamics Conference; Aug 07, 1978 - Aug 09, 1978; Palo Alto, CA; US
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  • 8
    Publication Date: 2019-06-28
    Description: Selecting a spacecraft maneuver strategy usually involves tradeoffs of many competing factors. This paper describes such a tradeoff process. The method uses parametric data to cope with targeting requirements, thruster configuration and performance, hardware constraints, operational considerations, propellant optimization demands, and expected execution and orbit determination errors, while remaining flexible to react to new conditions.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 84-2014
    Format: text
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  • 9
    Publication Date: 2019-06-28
    Description: This paper describes the development and use of an algorithm to compute approximate statistics of the magnitude of a single random trajectory correction maneuver (TCM) Delta v vector. The TCM Delta v vector is modeled as a three component Cartesian vector each of whose components is a random variable having a normal (Gaussian) distribution with zero mean and possibly unequal standard deviations. The algorithm uses these standard deviations as input to produce approximations to (1) the mean and standard deviation of the magnitude of Delta v, (2) points of the probability density function of the magnitude of Delta v, and (3) points of the cumulative and inverse cumulative distribution functions of Delta v. The approximates are based on Monte Carlo techniques developed in a previous paper by the author and extended here. The algorithm described is expected to be useful in both pre-flight planning and in-flight analysis of maneuver propellant requirements for space missions.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 84-2013
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  • 10
    Publication Date: 2019-07-13
    Description: A number of interplanetary missions now being planned involve placing deterministic maneuvers along the flight path to alter the trajectory. Lee and Boain (1973) examined the statistics of trajectory correction maneuver (TCM) magnitude with no deterministic ('bias') component. The Delta v vector magnitude statistics were generated for several values of random Delta v standard deviations using expansions in terms of infinite hypergeometric series. The present investigation uses a different technique (Monte Carlo simulation) to generate Delta v magnitude statistics for a wider selection of random Delta v standard deviations and also extends the analysis to the case of nonzero deterministic Delta v's. These Delta v magnitude statistics are plotted parametrically. The plots are useful in assisting the analyst in quickly answering questions about the statistics of Delta v magnitude for single TCM's consisting of both a deterministic and a random component. The plots provide quick insight into the nature of the Delta v magnitude distribution for the TCM.
    Keywords: ASTRODYNAMICS
    Type: AIAA PAPER 82-1429 , Astrodynamics Conference; Aug 09, 1982 - Aug 11, 1982; San Diego, CA
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