Sample records for quaternary fission

  1. Quaternary Studies

    NSDL National Science Digital Library

    First, the Irish Quaternary Association (IQUA) website publicizes its aim "to promote Quaternary studies in Ireland through its publications, and the organization of field meetings and conferences" (1). Visitors can learn about the importance of quaternary studies as well as find out the latest news and upcoming meetings. At the second website, the University of Wisconsin-Madison describes the current and recent studies dealing with "basic and applied problems in glacial geology, surficial geology, palynology, sedimentology, geologic mapping, hydrogeology, soils, and environmental geology "(2). The website offers abstracts of publications of members of the Department of Geology and Geophysics and the Wisconsin Geological and Natural History Survey along with descriptions of the lab, a shaded relief map of the Wisconsin area, and amusing glacial songs. Next, the Godwin Institute of Quaternary Research (GIQR) presents the University of Cambridge's history in quaternary research and the seven current research groups and four recent research projects (3 ). The website furnishes news from the research groups, a gallery of historical images of the East Anglia excursion, and summaries of the Institute's reference collections. Fourth, the International Union for Quaternary Research (INQUA) discusses quaternary scientists' investigations "to interpret the changing world of the glacial ages and their impact on our planet's surface environments" (4). Researchers can find out about INQUA-funded projects, meetings, and scientific commissions. Next, the Quaternary Research Association explains that it "exists to promote understanding of the Quaternary Period by publishing field guides, technical guides, and an international journal as well as holding field meetings and speaker meetings" (5). Students and researchers can discover employment, research, grant, meetings, and educational opportunities. Sixth, the University of Wales presents its investigations in the Remote Sensing Laboratory, Palaeoecology Laboratory, and the Luminescence Laboratory (6 ). Users can find concise descriptions of individual researchers' successes, abstracts of published papers, and links to conference information. The seventh website illustrates the Alaska Quaternary Center's commitment "to the promotion of interdisciplinary research and the enhancement of interdisciplinary instruction in Quaternary sciences" (7). Users can view images of the field work and learn how to obtain quaternary data from the Geographic Information Network of Alaska (GINA). Lastly, Rutgers University promotes its Graduate Certificate in Quaternary Studies where students take part in geology, geography, meteorology, and other disciplines interested in the last couple of million years of Earth's history (8). Students and educators can find information on the researchers involved with the program and the necessary course work.

  2. Quaternary investigation

    SciTech Connect

    Stieve, A.

    1991-05-15

    The primary purpose of the Quaternary investigation is to provide information on the location and age of Quaternary deposits for use in evaluating the presence or absence of neotectonic deformation or paleoliquefaction features within the Savannah River Site (SRS) region. The investigation will provide a basis for evaluating the potential for capable faults and associated deformation in the SRS vicinity. Particular attention will be paid to the Pen Branch fault.

  3. Irish Quaternary Association (IQUA)

    NSDL National Science Digital Library

    The Irish Quaternary Association (IQUA) website publicizes its aim "to promote Quaternary studies in Ireland through its publications, and the organization of field meetings and conferences." Visitors can learn about the importance of quaternary studies, find out the latest news and upcoming meetings, and find links to Quaternary studies journals.

  4. Quaternary and Geomorphology.

    ERIC Educational Resources Information Center

    Andrews, J. T.; Graf, W. L.

    1983-01-01

    Highlights conferences and meetings of organizations involved with quaternary geology and geomorphology, including International Union of Quaternary Research Conference held in Moscow. The impetus of a revision of "The Quaternary of the United States" resulted from this conference. Includes activities/aims of "Friends of the Pleistocene"…

  5. Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Denschlag, J. O.

    This chapter first gives a survey on the history of the discovery of nuclear fission. It briefly presents the liquid-drop and shell models and their application to the fission process. The most important quantities accessible to experimental determination such as mass yields, nuclear charge distribution, prompt neutron emission, kinetic energy distribution, ternary fragment yields, angular distributions, and properties of fission isomers are presented as well as the instrumentation and techniques used for their measurement. The contribution concentrates on the fundamental aspects of nuclear fission. The practical aspects of nuclear fission are discussed in http://dx.doi.org/10.1007/978-1-4419-0720-2_57 of Vol. 6.

  6. Quaternary Research Association

    NSDL National Science Digital Library

    The Quaternary Research Association explains that it "exists to promote understanding of the Quaternary Period by publishing field guides, technical guides, and an international journal as well as holding field meetings and speaker meetings." Students and researchers can discover employment, research, grant, meetings, and educational opportunities.

  7. International Union for Quaternary Research

    NSDL National Science Digital Library

    The International Union for Quaternary Research (INQUA) discusses quaternary scientists' investigations "to interpret the changing world of the glacial ages and their impact on our planet's surface environments.". Researchers can find out about INQUA-funded projects, meetings, scientific commissions, and INQUA's two publicaions, Quaternary International, and Quaternary Perspectives.

  8. Benchmarking nuclear fission theory

    NASA Astrophysics Data System (ADS)

    Bertsch, G. F.; Loveland, W.; Nazarewicz, W.; Talou, P.

    2015-07-01

    We suggest a small set of fission observables to be used as test cases for validation of theoretical calculations. The purpose is to provide common data to facilitate the comparison of different fission theories and models. The proposed observables are chosen from fission barriers, spontaneous fission lifetimes, fission yield characteristics, and fission isomer excitation energies.

  9. Quaternary Research Center

    NSDL National Science Digital Library

    "The Quaternary Research Center (QRC) fosters interdisciplinary research on the last two million years of the global environment: a time which encompasses massive, abrupt changes of climate, sea level, global biota and ice extent, as well the evolution of humans and the advent of civilization." Divided into six laboratories, the University of Washington's Center studies Cosmogenic Isotopes, Stable Isotopes, Old Quaternary Isotopes, Periglacial environments, quaternary ecology, paleoecology, and remote sensing. Researchers can find a tremendous amount of isotope, carbon dioxide, and chemistry data on the Taylor Dome, a part of the East Antarctic ice sheet. Students and educators can read papers by the center covering topics such as interactions among climate, surface, and tectonics; and glaciations and climate variations in the Pacific Northwest.

  10. Bimodal fission

    SciTech Connect

    Hulet, E.K.

    1989-04-19

    In recent years, we have measured the mass and kinetic-energy distributions from the spontaneous fission of /sup 258/Fm, /sup 259/Md, /sup 260/Md, /sup 258/No, /sup 262/No, and /sup 260/(104). All are observed to fission with a symmetrical division of mass, whereas the total-kinetic-energy (TKE) distributions strongly deviated from the Gaussian shape characteristically found in the fission of all other actinides. When the TKE distributions are resolved into two Gaussians the constituent peaks lie near 200 and near 233 MeV. We conclude two modes or bimodal fission is occurring in five of the six nuclides studied. Both modes are possible in the same nuclides, but one generally predominates. We also conclude the low-energy but mass-symmetrical mode is likely to extend to far heavier nuclei; while the high-energy mode will be restricted to a smaller region, a region of nuclei defined by the proximity of the fragments to the strong neutron and proton shells in /sup 132/Sn. 16 refs., 7 figs., 1 tab.

  11. Fission meter

    DOEpatents

    Rowland, Mark S. (Alamo, CA); Snyderman, Neal J. (Berkeley, CA)

    2012-04-10

    A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source.

  12. Quaternary Research Association Educational Resources

    NSDL National Science Digital Library

    The Quaternary Research Association (QRA) is an organization comprising archaeologists, botanists, civil engineers, geographers, geologists, soil scientists, zoologists and others interested in research into the problems of the Quaternary. This site describes their activities and organization. This direct link to the educational teaching resources provides access to glacier and glaciation resources.

  13. Quaternary GIS Laboratory

    NSDL National Science Digital Library

    This is the home page of the Quaternary Geographic Information System (GIS) Laboratory at the Institute of Arctic and Alpine Research (INSTAAR) at the University of Colorado. The laboratory supports quantitative spatial analysis of glacier, climate, coastal, and other environmental relationships at high latitudes. Users can access a collection of climate animations for the State of Alaska which show seasonal variation in monthly temperature and precipitation. There is also a set of high-resolution imagery and terrain models for Barrow, Alaska, an animation of the land bridge between Asia and North America, an atlas of paleoglaciation for the state, and links to a variety of other projects involving climatology, paleoclimatology, and glacial geomorphology in the Sate of Alaska.

  14. Enantioselective Construction of Cyclic Quaternary Centers: (-)-Mesembrine

    E-print Network

    Taber, Douglass

    Enantioselective Construction of Cyclic Quaternary Centers: (-)-Mesembrine Douglass F. Taber, (-)-mesembrine 1. Amide 2 should be a useful chiron for the enantioselective construction of cyclic quaternary of mesembrine2,3 and its analogues is the enantioselective construction of the chiral quaternary center.4 We

  15. Evidence on the influence of fission channels on fission phenomena

    Microsoft Academic Search

    T. Kaiser; H. R. von Gunten; J. Hadermann; K. Junker

    1978-01-01

    Partial fission channel widths can be extracted from fission cross-section analysis only up to a rotation in the space of fission vectors. We propose to obtain a physically significant basis for fission vectors taking into account information from other fission characteristics such as the valley-to-peak ratio of the mass distribution and the number of prompt neutrons emitted per fission event.

  16. Robustness of Quaternary glacial cycles

    NASA Astrophysics Data System (ADS)

    Ganopolski, Andrei; Brovkin, Victor; Calov, Reinhard

    2015-04-01

    In spite of significant progress in paleoclimate reconstructions and modeling some aspects of Quaternary climate cycles are still poorly understood. Among them is the question of whether glacial cycles are deterministic and solely externally forced or, at least partially, they are stochastic. The answer to this question can only be obtained using a comprehensive Earth system models which incorporates all major components of the Earth system - atmosphere, ocean, land surface, northern hemisphere ice sheets, terrestrial biota and soil carbon, aeolian dust and marine biogeochemistry. Here, we used the Earth system model of intermediate complexity CLIMBER-2. The model was optimally tuned to reproduce climate, ice volume and CO2 variability for the last 0.8 million years. Using the same model version, we performed a large set of simulations covering the entire Quaternary (3 million years). By starting the model at different times (with the time step of 100,000 years) and using identical initial conditions we run the model for 500,000 years using the Earth's orbital variations as the only prescribed radiative forcing. We show that within less than 100,000 years after the beginning of each experiment the modeling results converge to the same solution which depends only on the orbital forcing and boundary conditions, such as topography and terrestrial sediment thickness for the ice sheets or volcanic CO2 outgassing for the carbon cycle. By using only several sets of the Northern Hemisphere orography and sediment thickness which represent different stages of landscape evolution during Quaternary, we are able to reproduce all major regimes of Quaternary long-term climate variability. Our results thus strongly support the notion that Quaternary glacial cycles are deterministic and externally forced.

  17. The nuclear fission process

    Microsoft Academic Search

    Wagemans

    1991-01-01

    Fifty years after its discovery, the nuclear fission phenomenon is of recurring interest. When its fundamental physics aspects are considered, fission is viewed in a very positive way, which is reflected in the great interest generated by the meetings and large conferences organized for the 50th anniversary of its discovery. From a purely scientific and practical point of view, a

  18. Biomodal spontaneous fission

    SciTech Connect

    Hulet, E.K. (Lawrence Livermore National Lab., CA (USA))

    1989-09-26

    Investigations of mass and kinetic-energy distributions from spontaneous fission have been extended in recent years to an isotope of element 104 and, for half-lives, to an isotope of element 108. The results have been surprising in that spontaneous fission half-lives have turned out to be much longer than expected and mass and kinetic- energy distributions were found to abruptly shift away from those of the lighter actinides, showing two modes of fission. These new developments have caused a re-evaluation of our understanding of the fission process, bringing an even deeper appreciation of the role played by nuclear shell effects upon spontaneous fission properties. 16 refs., 10 figs.

  19. Introduction Preliminaries Construction of Quaternary Sequences Construction of Familes References New Construction of Quaternary Sequences

    E-print Network

    No, Jong-Seon

    Introduction Preliminaries Construction of Quaternary Sequences Construction of Familes References New Construction of Quaternary Sequences with Good Correlation Using Binary Sequences with Good University May 28, 2010 May 28, 2010 2010 CITS 2nd 1/ 34 #12;Introduction Preliminaries Construction

  20. Bimodal fission of Hs*

    NASA Astrophysics Data System (ADS)

    Itkis, I. M.; Itkis, M. G.; Knyazheva, G. N.; Kozulin, E. M.; Loktev, T. A.; Novikov, K. V.; Hanappe, F.; Vardaci, E.

    2014-05-01

    Mass and energy distributions of fission fragments obtained in the reactions 22Ne + 249Cf, 26Mg + 248Cm, and 22Ne + 238U have been measured. A special attention will be paid on the properties of mass-energy distribution of fission fragments obtained in the reaction 26Mg + 248Cm at an excitation energy of 35 MeV. At this energy shell effects should become more effective in fission, the TKE distribution of symmetric fragments obtained in the reaction 26Mg + 248Cm differs strongly from a Gaussian shape. Besides a low-energy component, a high-energy component, not foreseen in the LDM, arises. This is attributed to the fact that both fission fragments are close to the spherical neutron shell N = 82. It means that for the compound nucleus 274Hs*, formed in the reaction 26Mg + 248Cm, the phenomenon of bimodal fission was observed for the first time. For the compound nucleus 260No* formed in the reaction 22Ne + 238U at the initial excitation energy of 41 MeV the bimodal fission as well as superasymmetric fission were observed.

  1. Quaternary glaciation of Mount Everest

    Microsoft Academic Search

    Lewis A. Owen; Ruth Robinson; Douglas I. Benn; Robert C. Finkel; Nicole K. Davis; Chaolu Yi; Jaakko Putkonen; Dewen Li; Andrew S. Murray

    2009-01-01

    The Quaternary glacial history of the Rongbuk valley on the northern slopes of Mount Everest is examined using field mapping, geomorphic and sedimentological methods, and optically stimulated luminescence (OSL) and 10Be terrestrial cosmogenic nuclide (TCN) dating. Six major sets of moraines are present representing significant glacier advances or still-stands. These date to >330ka (Tingri moraine), >41ka (Dzakar moraine), 24–27ka (Jilong

  2. Quaternary ecology: A paleoecological perspective

    SciTech Connect

    Delcourt, H.R.; Delcourt, P.A.

    1991-01-01

    This book considers issues and problems in ecology which may be illuminated, if not solved, by considering paleoecology. The five central chapters include a discussion of application of Quaternary ecology to future global climate change, including global warming. Other areas presented include: population dispersal, invasions, expansions, and migrations; plant successions; ecotones; factors in community structure; ecosystem patterns and processes. Published case studies are numerous. The role played by continuing climatic change in vegetation change is acknowledged but not stressed.

  3. 40 CFR 721.10511 - Quaternary ammonium salts (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 false Quaternary ammonium salts (generic). 721.10511 Section 721...Substances § 721.10511 Quaternary ammonium salts (generic). (a) Chemical substance...identified generically as quaternary ammonium salts (PMNs P-07-320,...

  4. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Quaternary ammonium chloride combination...Preservatives § 172.165 Quaternary ammonium chloride combination... The food additive, quaternary ammonium chloride combination...7.0-8.0; total amines, maximum 1 percent...

  5. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Quaternary ammonium chloride combination...Preservatives § 172.165 Quaternary ammonium chloride combination... The food additive, quaternary ammonium chloride combination...7.0-8.0; total amines, maximum 1 percent...

  6. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...2013-07-01 false Tricyclic quaternary amine salt (generic). 721.10569... § 721.10569 Tricyclic quaternary amine salt (generic). (a...identified generically as tricyclic quaternary amine salt (PMN...

  7. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Quaternary ammonium chloride combination...Preservatives § 172.165 Quaternary ammonium chloride combination... The food additive, quaternary ammonium chloride combination...7.0-8.0; total amines, maximum 1 percent...

  8. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2009-04-01 true Quaternary ammonium chloride combination...Preservatives § 172.165 Quaternary ammonium chloride combination... The food additive, quaternary ammonium chloride combination...7.0-8.0; total amines, maximum 1 percent...

  9. 21 CFR 172.165 - Quaternary ammonium chloride combination.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Quaternary ammonium chloride combination...Preservatives § 172.165 Quaternary ammonium chloride combination... The food additive, quaternary ammonium chloride combination...7.0-8.0; total amines, maximum 1 percent...

  10. 40 CFR 721.10569 - Tricyclic quaternary amine salt (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...2014-07-01 false Tricyclic quaternary amine salt (generic). 721.10569... § 721.10569 Tricyclic quaternary amine salt (generic). (a...identified generically as tricyclic quaternary amine salt (PMN...

  11. Surface interaction of quaternary amines with hair

    Microsoft Academic Search

    B. C. Beard; J. Hare

    2002-01-01

    Surface analysis by X-ray photoelectron spectroscopy (XPS) has shown specific 1?1 (ionic) interaction between cationic alkyl\\u000a quaternary surfactant molecules and the anionic sulfonate groups present on the hair surface. The primary driving force for\\u000a the adsorption of alkyl quaternary amine molecules to the surface of the hair from aqueous solution is the ionic interaction\\u000a between quaternary groups and the surface

  12. Nuclear fission of Fm isotopes

    SciTech Connect

    Asano, T. [VBL, Hokkaido University, Sapporo (Japan); Wada, T. [Department of Pure and Applied Physics, Kansai University, Suita (Japan); Ohta, M. [Hirao School of Management, Konan University, Nishinomoya (Japan); Chiba, S. [Advanced Science Research Center, JAEA Tokai, Naka (Japan)

    2010-06-01

    Multi-modal fission has been systematically investigated for the series of isotopes of Fm and Cf. The multi-dimensional Langevin-type stochastic differential equation is used for the dynamical calculation. The primary fission mode changes from mass-asymmetric fission to mass-symmetric fission with the increase of neutron numbers for both Fm and Cf cases.

  13. Singlet fission photovoltaics

    E-print Network

    Lee, Jiye

    2013-01-01

    The efficiency of a solar cell is restricted by the "single junction limit," whereby photons with energy higher than the bandgap lose energy by thermalization. Singlet exciton fission splits a high-energy molecular excitation ...

  14. Singlet exciton fission photovoltaics.

    PubMed

    Lee, Jiye; Jadhav, Priya; Reusswig, Philip D; Yost, Shane R; Thompson, Nicholas J; Congreve, Daniel N; Hontz, Eric; Van Voorhis, Troy; Baldo, Marc A

    2013-06-18

    Singlet exciton fission, a process that generates two excitons from a single photon, is perhaps the most efficient of the various multiexciton-generation processes studied to date, offering the potential to increase the efficiency of solar devices. But its unique characteristic, splitting a photogenerated singlet exciton into two dark triplet states, means that the empty absorption region between the singlet and triplet excitons must be filled by adding another material that captures low-energy photons. This has required the development of specialized device architectures. In this Account, we review work to develop devices that harness the theoretical benefits of singlet exciton fission. First, we discuss singlet fission in the archetypal material, pentacene. Pentacene-based photovoltaic devices typically show high external and internal quantum efficiencies. They have enabled researchers to characterize fission, including yield and the impact of competing loss processes, within functional devices. We review in situ probes of singlet fission that modulate the photocurrent using a magnetic field. We also summarize studies of the dissociation of triplet excitons into charge at the pentacene-buckyball (C60) donor-acceptor interface. Multiple independent measurements confirm that pentacene triplet excitons can dissociate at the C60 interface despite their relatively low energy. Because triplet excitons produced by singlet fission each have no more than half the energy of the original photoexcitation, they limit the potential open circuit voltage within a solar cell. Thus, if singlet fission is to increase the overall efficiency of a solar cell and not just double the photocurrent at the cost of halving the voltage, it is necessary to also harvest photons in the absorption gap between the singlet and triplet energies of the singlet fission material. We review two device architectures that attempt this using long-wavelength materials: a three-layer structure that uses long- and short-wavelength donors and an acceptor and a simpler, two-layer combination of a singlet-fission donor and a long-wavelength acceptor. An example of the trilayer structure is singlet fission in tetracene with copper phthalocyanine inserted at the C60 interface. The bilayer approach includes pentacene photovoltaic cells with an acceptor of infrared-absorbing lead sulfide or lead selenide nanocrystals. Lead selenide nanocrystals appear to be the most promising acceptors, exhibiting efficient triplet exciton dissociation and high power conversion efficiency. Finally, we review architectures that use singlet fission materials to sensitize other absorbers, thereby effectively converting conventional donor materials to singlet fission dyes. In these devices, photoexcitation occurs in a particular molecule and then energy is transferred to a singlet fission dye where the fission occurs. For example, rubrene inserted between a donor and an acceptor decouples the ability to perform singlet fission from other major photovoltaic properties such as light absorption. PMID:23611026

  15. Potentials of fissioning plasmas

    NASA Technical Reports Server (NTRS)

    Thom, K.

    1979-01-01

    Successful experiments with the nuclear pumping of lasers have demonstrated that in a gaseous medium the kinetic energy of fission fragments can be converted directly into nonequilibrium optical radiation. This confirms the concept that the fissioning medium in a gas-phase nuclear reactor shows an internal structure such as a plasma in near thermal equilibrium varying up to a state of extreme nonequilibrium. During 20 years of research under NASA support major elements of the fissioning plasma reactor were demonstrated in theory and experiment, culminating in a proof-of-principle reactor test conducted at the Los Alamos Scientific Laboratory. It is concluded that the construction of a gaseous fuel reactor power plant is within the reach of present technology.

  16. Fission fragment angular distributions

    SciTech Connect

    Bond, P.D.

    1985-01-01

    Many recent papers have found that calculations with the standard angular distribution formula for fission fragments from compound nuclei do not reproduce the strong anisotropies observed in the decay of high spin systems. They conclude that a noncompound nuclear process must exist for some partial waves and postulate an ad-hoc angular distribution for this process in order to reproduce the strong anisotropies. It is the purpose of this contribtion to demonstrate that much of the data are, in fact, consistent with compound nucleus formation and to emphasize that the standard model is not a generally valid way to calculate fission fragment angular distributions from a compound nucleus.

  17. Space Fission System Test Effectiveness

    Microsoft Academic Search

    Mike Houts; Glen L. Schmidt; Melissa van Dyke; Tom Godfroy; James Martin; Shannon Bragg-Sitton; Ricky Dickens; Pat Salvail; Roger Harper

    2004-01-01

    Space fission technology has the potential to enable rapid access to any point in the solar system. If fission propulsion systems are to be developed to their full potential, however, near-term customers need to be identified and initial fission systems successfully developed, launched, and utilized. One key to successful utilization is to develop reactor designs that are highly testable. Testable

  18. Tip model of cold fission

    Microsoft Academic Search

    F. Gönnenwein; B. Börsig

    1991-01-01

    Cold fission is defined to be the limiting case of nuclear fission where virtually all of the available energy is converted into the total kinetic energy of the fragments. The fragments have, therefore, to be born in or at least close to their respective ground states. Starting from the viewpoint that cold fission corresponds to most compact scission configurations, energy

  19. Pulsed Fission Propulsion Concept

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In the 1960's U.S. Government laboratories, under Project Orion, investigated a pulsed nuclear fission propulsion system. Small nuclear pulse units would be sequentially discharged from the aft end of the vehicle. A blast shield and shock absorber system would protect the crew and convert the shock loads into a continuous propulsive force.

  20. Pulsed Fission Propulsion Concept

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In the 1960's U.S. Government laboratories, under Project Orion, investigated a pulsed nuclear fission propulsion system. Small nuclear pulse units would be sequentially discharged from the aft end of the vehicle. A blast shield and shock absorber system would protect the crew and convert the shock loads into a continuous propusive force.

  1. Natural fission reactor

    Microsoft Academic Search

    L G. A. Cowan

    1976-01-01

    The evidence supporting the establishment of the zones of a natural fission reactor that occurred about 2 billion years ago is presented. The reactor evidence was found in an open-pit uranium mine in the southeastern part of the Gabon Republic, near the Equator on the coast of West Africa. The history of the probable sequence of events leading to the

  2. Antibacterial and Hemolytic Activities of Quaternary Pyridinium

    E-print Network

    Antibacterial and Hemolytic Activities of Quaternary Pyridinium Functionalized Polynorbornenesa] They found that polymers with higher cationic functionality had stronger antibacterial activity. Sepa- rately, it was shown that methacrylate based polymers with pendant pyridinium moieties exhibited antibacterial activity

  3. Ice Age refugia and Quaternary extinctions: An issue of Quaternary evolutionary palaeoecology

    NASA Astrophysics Data System (ADS)

    Stewart, John R.; Cooper, Alan

    2008-12-01

    Quaternary palaeoecology, as a discipline, involves the analysis of a large range of fossil organisms from the last ca. 2 million years. This paper considers the role that these Quaternary records can take in better understanding the evolution of those organisms. We also discuss the surprisingly low uptake of evolutionary biology in Quaternary palaeoecological studies. This leads us to encourage an advance on both these fronts with a greater degree of collaboration with phylogeographic and ancient DNA researchers. These discussions accompany a summary of a special issue of Quaternary Science Reviews representing the proceedings of the XVII INQUA held in Cairns Australia in 2007. This special issue includes papers on a wide variety of Quaternary evolutionary palaeoecological and population dynamic subjects including extinct Pacific Island palm trees, Beringian beetles, Scandinavian trees, and the effects on human and animal populations of an extraterrestrial impact event in the Late Glacial of North America.

  4. Fission channels of ?

    Microsoft Academic Search

    R. A. Gherghescu; D. N. Poenaru; W. Greiner

    1998-01-01

    The main fission modes of the double magic 0954-3899\\/24\\/6\\/009\\/img9 are investigated from both a static and dynamic point of view. A set of spin-orbit and 0954-3899\\/24\\/6\\/009\\/img10 strength parameters is selected such that a minimum occurs in the shell correction energy at Z = 120 and N = 184. The mass asymmetry is settled around the two double magic fragments: 0954-3899\\/24\\/6\\/009\\/img11

  5. Fission-induced plasmas

    NASA Technical Reports Server (NTRS)

    Harries, W. L.; Shiu, Y. J.

    1979-01-01

    The possibility of creating a plasma from fission fragments, and to utilize the energy of the particles to create population inversion that would lead to laser action is investigated. An investigation was made of various laser materials which could be used for nuclear-pumped lasing. The most likely candidate for a fissioning material in the gaseous form is uranium hexafluoride - UF6, and experiments were performed to investigate materials that would be compatible with it. One of the central problems in understanding a fission-induced plasma is to obtain a model of the electron behavior, and some preliminary calculations are presented. In particular, the rates of various processes are discussed. A simple intuitive model of the electron energy distribution function is also shown. The results were useful for considering a mathematical model of a nuclear-pumped laser. Next a theoretical model of a (3)He-Ar nuclear-pumped laser is presented. The theory showed good qualitative agreement with the experimental results.

  6. Quaternary geologic map of Minnesota

    NASA Technical Reports Server (NTRS)

    Goebel, J. E.

    1977-01-01

    The Quaternary Geologic Map of Minnesota is a compilation based both on the unique characteristics of satellite imagery and on the results of previous field investigations, both published and unpublished. The use of satellite imagery has made possible the timely and economical construction of this map. LANDSAT imagery interpretation proved more useful than expected. Most of the geologic units could be identified by extrapolating from specific sites where the geology had been investigated into areas where little was known. The excellent geographic registry coupled with the multi-spectral record of these images served to identify places where the geologic materials responded to their ecological environment and where the ecology responded to the geologic materials. Units were well located on the map at the scale selected for the study. Contacts between till units could be placed with reasonable accuracy. The reference points that were used to project delineations between units (rivers, lakes, hills, roads and other features), which had not been accurately located on early maps, could be accurately located with the help of the imagery. The tonal and color contrasts, the patterns reflecting geologic change and the resolution of the images permitted focusing attention on features which could be represented at the final scale of the map without distraction by other interesting but site-specific details.

  7. Quaternary glaciation of Mount Everest

    NASA Astrophysics Data System (ADS)

    Owen, Lewis A.; Robinson, Ruth; Benn, Douglas I.; Finkel, Robert C.; Davis, Nicole K.; Yi, Chaolu; Putkonen, Jaakko; Li, Dewen; Murray, Andrew S.

    2009-07-01

    The Quaternary glacial history of the Rongbuk valley on the northern slopes of Mount Everest is examined using field mapping, geomorphic and sedimentological methods, and optically stimulated luminescence (OSL) and 10Be terrestrial cosmogenic nuclide (TCN) dating. Six major sets of moraines are present representing significant glacier advances or still-stands. These date to >330 ka (Tingri moraine), >41 ka (Dzakar moraine), 24-27 ka (Jilong moraine), 14-17 ka (Rongbuk moraine), 8-2 ka (Samdupo moraines) and ˜1.6 ka (Xarlungnama moraine), and each is assigned to a distinct glacial stage named after the moraine. The Samdupo glacial stage is subdivided into Samdupo I (6.8-7.7 ka) and Samdupo II (˜2.4 ka). Comparison with OSL and TCN defined ages on moraines on the southern slopes of Mount Everest in the Khumbu Himal show that glaciations across the Everest massif were broadly synchronous. However, unlike the Khumbu Himal, no early Holocene glacier advance is recognized in the Rongbuk valley. This suggests that the Khumbu Himal may have received increased monsoon precipitation in the early Holocene to help increase positive glacier mass balances, while the Rongbuk valley was too sheltered to receive monsoon moisture during this time and glaciers could not advance. Comparison of equilibrium-line altitude depressions for glacial stages across Mount Everest reveals asymmetric patterns of glacier retreat that likely reflects greater glacier sensitivity to climate change on the northern slopes, possibly due to precipitation starvation.

  8. A Quaternary volcanic ash deposit in western Missouri

    SciTech Connect

    Emerson, J.W. (Central Missouri State Univ., Warrensburg, MO (United States))

    1993-03-01

    Quaternary volcanic ash has been found in more than fifty localities in the midwest. The most widespread deposits originated from the Long Valley caldera, California; the Jemez calderas, New Mexico; or the Yellowstone caldera, Wyoming. Fission track dating has grouped the deposits into six separate ash falls ranging from 700,000--2,000,000 years old. A small volcanic ash deposit in western Missouri may be correlative with those found along the Kansas and Marais de Cygnes rivers in eastern Kansas. The ash deposit is in Northwest Bates County Missouri, exposed along a tributary to Miami Creek, four miles east of the Kansas state line. The ash layer is interbedded with alluvial terrace deposits and ranges from fifteen to thirty inches in thickness. It is inferred to have been deposited in a pond or oxbow lake. The color is white with a pale yellow tinge (Munsell 10YR 8/2). Shard examination shows that about 70% are flat bubble-wall types, about 20% have straight ridges, less than 10% are bubble-junction, and only a trace are vesicular. The closest known volcanic ash occurrence is an ash outcropping in a Kansas river terrace near DeSoto, KS, forty-five miles to the northwest. The DeSoto deposit has been identified as the .62 m.y. Lava Creek B ash from the Yellowstone caldera. A preliminary correlation of the Missouri ash with the DeSoto ash is based on similar shard morphology and color.

  9. More detailed study of fission dynamics in fusion-fission reactions within a stochastic approach

    Microsoft Academic Search

    P. N. Nadtochy; G. D. Adeev; A. V. Karpov

    2002-01-01

    A stochastic approach based on three-dimensional Langevin equations was applied to a more detailed study of fission dynamics in fusion-fission reactions. The dynamical model has been developed and extended to investigate fission characteristics of light fissioning nuclei at low excitation energies. The energy dependences of an anisotropy of the fission fragment angular distribution, an evaporation residue cross section, a fission

  10. The SPIDER fission fragment spectrometer for fission product yield measurements

    NASA Astrophysics Data System (ADS)

    Meierbachtol, K.; Tovesson, F.; Shields, D.; Arnold, C.; Blakeley, R.; Bredeweg, T.; Devlin, M.; Hecht, A. A.; Heffern, L. E.; Jorgenson, J.; Laptev, A.; Mader, D.; O`Donnell, J. M.; Sierk, A.; White, M.

    2015-07-01

    The SPectrometer for Ion DEtermination in fission Research (SPIDER) has been developed for measuring mass yield distributions of fission products from spontaneous and neutron-induced fission. The 2E-2v method of measuring the kinetic energy (E) and velocity (v) of both outgoing fission products has been utilized, with the goal of measuring the mass of the fission products with an average resolution of 1 atomic mass unit (amu). The SPIDER instrument, consisting of detector components for time-of-flight, trajectory, and energy measurements, has been assembled and tested using 229Th and 252Cf radioactive decay sources. For commissioning, the fully assembled system measured fission products from spontaneous fission of 252Cf. Individual measurement resolutions were met for time-of-flight (250 ps FWHM), spacial resolution (2 mm FHWM), and energy (92 keV FWHM for 8.376 MeV). Mass yield results measured from 252Cf spontaneous fission products are reported from an E-v measurement.

  11. Bacterial adhesion inhibition of the quaternary ammonium functionalized silica nanoparticles

    Microsoft Academic Search

    Jooyoung Song; Hyeyoung Kong; Jyongsik Jang

    2011-01-01

    Quaternary ammonium compounds have been considered as excellent antibacterial agents due to their effective biocidal activity, long term durability and environmentally friendly performance. In this work, 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride as a quaternary ammonium silane was applied for the surface modification of silica nanoparticles. The quaternary ammonium silane provided silica surface with hydrophobicity and antibacterial properties. In addition, the glass surface which

  12. Synthesis of Surface-Active Quaternary Amino Polyfluorosiloxanes

    E-print Network

    Chaudhury, Manoj K.

    , on further reaction with various amines followed by quaternization, gave quaternary amino polyfluorosiloxanes prepared by quaternization of fluorocarbon amines using alkyl halide. Quaternary fluorocarbon7 (CF3)2CF(CF2Synthesis of Surface-Active Quaternary Amino Polyfluorosiloxanes ASHISH VAIDYA, MANOJ CHAUDHURY

  13. Post-scission fission theory: Neutron emission in fission

    SciTech Connect

    Madland, D.G.

    1997-11-01

    A survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N (E) and the average prompt neutron multiplicity {bar {nu}}{sub p}. Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N (E) and {bar {nu}}{sub p} upon the fissioning nucleus and its excitation energy are treated. Recent work in the calculation of the prompt fission neutron spectrum matrix N (E, E{sub n}), where E{sub n} is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of our ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches.

  14. Fission-Product Yields following Fast Fission of ^238U.^*

    NASA Astrophysics Data System (ADS)

    Campbell, J. M.; Couchell, G. P.; Li, S.; Nguyen, H. V.; Pullen, D. J.; Seabury, E. H.; Schier, W. A.; Tipnis, S. V.; England, T. R.

    1996-10-01

    High-resolution gamma-ray spectra from fast fission of ^238U have been measured at 13 delay-time intervals ranging from 0.3s to 5,000s after fission. The spectra were measured using a high-purity germanium detector enclosed in a NaI(Tl) Compton suppression annulus. The rapid transfer of fission products from the fission chamber to a low-background counting room by means of a helium-jet/tape transport system leads to a marked reduction in background and allows measurement of spectra at short delay times. Beta-gamma coincidence leads to a further reduction in background. Cumulative and independent yields of individual fission products are calculated from the relative line intensities extracted from the aggregate spectra, and are compared to ENDF/B-VI yield values. Supported in part by the U.S. Department of Energy

  15. Fission and Fusion Game

    NSDL National Science Digital Library

    2012-09-28

    In this activity, students play a board game where they learn the characteristics of and differences between fission and fusion, as well as the real world applications of these energy-releasing reactions. Reproducible game cards and and game board are included in the resource. The investigation supports material presented in chapter 3, "What Heats the Earth's Interior?" in the textbook, Energy flow, part of the Global System Science, an interdisciplinary course for high school students that emphasizes how scientists from a wide variety of fields work together to understand significant problems of global impact.

  16. Catalytic enantioselective synthesis of quaternary carbon stereocentres

    NASA Astrophysics Data System (ADS)

    Quasdorf, Kyle W.; Overman, Larry E.

    2014-12-01

    Quaternary carbon stereocentres--carbon atoms to which four distinct carbon substituents are attached--are common features of molecules found in nature. However, before recent advances in chemical catalysis, there were few methods of constructing single stereoisomers of this important structural motif. Here we discuss the many catalytic enantioselective reactions developed during the past decade for the synthesis of single stereoisomers of such organic molecules. This progress now makes it possible to incorporate quaternary stereocentres selectively in many organic molecules that are useful in medicine, agriculture and potentially other areas such as flavouring, fragrances and materials.

  17. Fission-fragment angular distributions

    SciTech Connect

    Bond, P.D.

    1984-02-06

    The universally used ''exact'' formula for fission-fragment angular distributions is shown to be valid only under restrictive assumptions. The more general expression, which depends crucially on the final fragment spin distributions, predicts dramatically more anisotropic angular distributions for fission from nuclei at high spin. Recent ''anomalous'' results are analyzed.

  18. Fission-Fragment Angular Distributions

    NASA Astrophysics Data System (ADS)

    Bond, P. D.

    1984-02-01

    The universally used "exact" formula for fission-fragment angular distributions is shown to be valid only under restrictive assumptions. The more general expression, which depends crucially on the final fragment spin distributions, predicts dramatically more anisotropic angular distributions for fission from nuclei at high spin. Recent "anomalous" results are analyzed.

  19. Fission hindrance in hot nuclei

    Microsoft Academic Search

    B. B. Back; D. J. Hofman; V. Nanal

    1997-01-01

    The role of dynamics in fission has attracted much interest since the discovery of this process over fifty years ago. However, the study of the dynamical aspects of fission was for many years hampered by the lack of suitable experimental observables against which theoretical calculations could be tested. For example, it was found that the total kinetic energy release in

  20. A threshold for dissipative fission

    SciTech Connect

    Thoennessen, M. [Michigan State Univ., East Lansing, MI (United States); Bertsch, G.F. [Washington Univ., Seattle, WA (United States)

    1993-09-21

    The empirical domain of validity of statistical theory is examined as applied to fission data on pre-fission data on pre-fission neutron, charged particle, and {gamma}-ray multiplicities. Systematics are found of the threshold excitation energy for the appearance of nonstatistical fission. From the data on systems with not too high fissility, the relevant phenomenological parameter is the ratio of the threshold temperature T{sub thresh} to the (temperature-dependent) fission barrier height E{sub Bar}(T). The statistical model reproduces the data for T{sub thresh}/E{sub Bar}(T) < 0.26 {plus_minus} 0.05, but underpredicts the multiplicities at higher T{sub thresh}/E{sub Bar}(T) independent of mass and fissility of the systems.

  1. Fifty years with nuclear fission

    SciTech Connect

    Behrens, J.W.; Carlson, A.D. (eds.) (National Institute of Standards and Technology, Gaithersburg, MD (United States))

    1989-01-01

    The news of the discovery of nuclear fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fifieth anniversary of its discovery by holding a topical meeting entitled, Fifty Years with Nuclear Fission,'' in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent development in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicated a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two fully days of sessions (April 27 and 28) at the main site of the NIST in Gaithersburg, Maryland. The wide range of topics covered in this Volume 1 by this topical meeting included plenary invited, and contributed sessions entitled: Preclude to the First Chain Reaction -- 1932 to 1942; Early Fission Research -- Nuclear Structure and Spontaneous Fission; 50 Years of Fission, Science, and Technology; Nuclear Reactors, Secure Energy for the Future; Reactors 1; Fission Science 1; Safeguards and Space Applications; Fission Data; Nuclear Fission -- Its Various Aspects; Theory and Experiments in Support of Theory; Reactors and Safeguards; and General Research, Instrumentation, and By-Product. The individual papers have been cataloged separately.

  2. Enantioselective construction of remote quaternary stereocentres

    NASA Astrophysics Data System (ADS)

    Mei, Tian-Sheng; Patel, Harshkumar H.; Sigman, Matthew S.

    2014-04-01

    Small molecules that contain all-carbon quaternary stereocentres--carbon atoms bonded to four distinct carbon substituents--are found in many secondary metabolites and some pharmaceutical agents. The construction of such compounds in an enantioselective fashion remains a long-standing challenge to synthetic organic chemists. In particular, methods for synthesizing quaternary stereocentres that are remote from other functional groups are underdeveloped. Here we report a catalytic and enantioselective intermolecular Heck-type reaction of trisubstituted-alkenyl alcohols with aryl boronic acids. This method provides direct access to quaternary all-carbon-substituted ?-, ?-, ?-, ?- or ?-aryl carbonyl compounds, because the unsaturation of the alkene is relayed to the alcohol, resulting in the formation of a carbonyl group. The scope of the process also includes incorporation of pre-existing stereocentres along the alkyl chain, which links the alkene and the alcohol, in which the stereocentre is preserved. The method described allows access to diverse molecular building blocks containing an enantiomerically enriched quaternary centre.

  3. Action of Quaternary Ammonium Salts on Nerve

    Microsoft Academic Search

    S. L. Cowan

    1933-01-01

    EXPERIMENTS similar to those of Fromherz with curare on medullated nerve, referred to by Prof. A. V. Hill in his article on ``The Physical Nature of the Nerve Impulse'',1 in NATURE of April 8, have been made with pure quaternary ammonium salts prepared by Dr. H. R. Ing. These have a curare-like action, preventing transmission of excitation from nerve to

  4. Method for clay stabilization with quaternary amines

    SciTech Connect

    Himes, R.E.

    1992-03-24

    This patent describes a method of treating a subterranean formation. It comprises: contacting the formation with an aqueous treatment fluid containing a formation control additive in an amount effective to stabilize the formation; the additive comprising a quaternary ammonium compound selected from compounds.

  5. Surface modification of sepiolite with quaternary amines

    Microsoft Academic Search

    Jovan Lemi?; Magdalena Tomaševi?-?anovi?; Mirjana Djuri?i?; Tanja Stani?

    2005-01-01

    This study was aimed at elucidating the mechanism of adsorption of quaternary amines, stearyldimethylbenzylammoniumchloride (SDBAC), as monomers and as micelles, distearyldimethylammoniumchloride (DDAC) and hexadecyltrimethylammoniumchloride (HTAC), on the surface of sepiolite. The adsorption capacity for these surfactants onto sepiolite, calculated by fitting the experimental data to the Langmuir–Freundlich equation, were 324% (SDBAC), 278% (DDAC), and 258% (HTAC) of the cation exchange

  6. ADSORPTION MECHANISM OF QUATERNARY AMINES BY SEPIOLITE

    Microsoft Academic Search

    E. Sabah; M. S. Çelik

    2002-01-01

    A series of adsorption tests examined the uptake of typical quaternary cationic surfactants, dodecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide from water by a clay mineral, sepiolite. Adsorption tests conducted under different conditions revealed that sepiolite is highly receptive to adsorption of cationic surfactants. Adsorption of cationic surfactants on sepiolite exhibits two distinct regions. The first stage is characterized by low rate

  7. Connections between Quaternary and Binary Bent Functions

    E-print Network

    Connections between Quaternary and Binary Bent Functions Patrick Solâ??e 1 and Natalia Tokareva 2 1@math.nsc.ru Abstract. Boolean bent functions were introduced by Rothaus (1976) as combinatorial objects related to di functions (Schmidt, 2006) and quater­ nary bent functions (Kumar, Scholtz, Welch, 1985) are explored. We

  8. Connections between Quaternary and Binary Bent Functions

    E-print Network

    Tokareva, Natalia

    Connections between Quaternary and Binary Bent Functions Patrick Sol´e1 and Natalia Tokareva2 1@math.nsc.ru Abstract. Boolean bent functions were introduced by Rothaus (1976) as combinatorial objects related functions (Schmidt, 2006) and quater- nary bent functions (Kumar, Scholtz, Welch, 1985) are explored. We

  9. Fifty years with nuclear fission

    SciTech Connect

    Behrens, J.W.; Carlson, A.D. (eds.) (National Institute of Standards and Technology, Gaithersburg, MD (United States))

    1989-01-01

    The news of the discovery of nucler fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fiftieth anniversary of its discovery by holding a topical meeting entitled, Fifty years with nuclear fission,'' in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent developments in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicating a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two full days of sessions (April 27 and 28) at the main sites of the NIST in Gaithersburg, Maryland. The wide range of topics covered by Volume 2 of this topical meeting included plenary invited, and contributed sessions entitled, Nuclear fission -- a prospective; reactors II; fission science II; medical and industrial applications by by-products; reactors and safeguards; general research, instrumentation, and by-products; and fission data, astrophysics, and space applications. The individual papers have been cataloged separately.

  10. Call Title: Nuclear Fission and Radiation Protection Call Identifier: FP7-Fission-2009

    E-print Network

    De Cindio, Fiorella

    small or medium-scale Collaborative Projects Advanced nuclear systems for increased sustainability in sustainable nuclear fission energy Coordination and Support Action (coordinating action) Fission-2.3 FissionCall Title: Nuclear Fission and Radiation Protection · Call Identifier: FP7-Fission-2009 · Date

  11. Fusion, fission, and quasi-fission using TDHF

    NASA Astrophysics Data System (ADS)

    Umar, Sait; Oberacker, Volker

    2014-03-01

    We study fusion, fission, and quasi-fission reactions using the time-dependent Hartee-Fock (TDHF) approach together with the density-constrained TDHF method for fusion. The only input is the Skyrme NN interaction, there are no adjustable parameters. We discuss the identification of quasi-fission in 40Ca+238U, the scission dynamics in symmetric fission of 264Fm, as well as calculating heavy-ion interaction potentials V (R) , mass parameters M (R) , and total fusion cross sections from light to heavy systems. Some of the effects naturally included in these calculations are: neck formation, mass exchange, internal excitations, deformation effects, as well as nuclear alignment for deformed systems. Supported by DOE grant DE-FG02-96ER40975.

  12. Fission products of transuranium elements in space

    NASA Astrophysics Data System (ADS)

    Shukoliukov, Iu. A.; Dang, V. M.

    The current status of the problem of transuranium elements in space is reviewed. Particular attention is given to Pu-244 fission products in eucrite achondrites; xenon as a fission product in chondrites; the isotopic composition of Xe in meteorites and the evolution of the earth's atmosphere; anomalies of the isotopic composition of uranium in meteorites; the contribution of fission products to the abundance of other elements in space; fission products in lunar matter; and cosmochronology according to fission products.

  13. Quantum Relaxation in Singlet Fission

    NASA Astrophysics Data System (ADS)

    Teichen, Paul; Eaves, Joel

    2013-03-01

    Singlet fission is a multielectron process in organic chromophores, where an initially excited singlet state decays into two independent triplets. First observed in organic semiconductors almost 40 years ago, the phenomenon may be a promising route for increasing yields in next-generation photovoltaics. Early theories that ignored quantum coherence between excited states were capable of explaining the fission process on nanosecond timescales, but recent observations of fission on sub picosecond timescales call several tenants of those theories into question. We present a theory of optical dephasing and decoherence in singlet fission, drawing on ideas from quantum information theory to establish conditions for decoherence and disentanglement between the relevant quantum states on the picosecond timescale.

  14. Background radiation from fission pulses

    SciTech Connect

    England, T.R.; Arthur, E.D.; Brady, M.C.; LaBauve, R.J.

    1988-05-01

    Extensive source terms for beta, gamma, and neutrons following fission pulses are presented in various tabular and graphical forms. Neutron results from a wide range of fissioning nuclides (42) are examined and detailed information is provided for four fuels: /sup 235/U, /sup 238/U, /sup 232/Th, and /sup 239/Pu; these bracket the range of the delayed spectra. Results at several cooling (decay) times are presented. For ..beta../sup -/ and ..gamma.. spectra, only /sup 235/U and /sup 239/Pu results are given; fission-product data are currently inadequate for other fuels. The data base consists of all known measured data for individual fission products extensively supplemented with nuclear model results. The process is evolutionary, and therefore, the current base is summarized in sufficient detail for users to judge its quality. Comparisons with recent delayed neutron experiments and total ..beta../sup -/ and ..gamma.. decay energies are included. 27 refs., 47 figs., 9 tabs.

  15. Advanced Space Fission Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; Borowski, Stanley K.

    2010-01-01

    Fission has been considered for in-space propulsion since the 1940s. Nuclear Thermal Propulsion (NTP) systems underwent extensive development from 1955-1973, completing 20 full power ground tests and achieving specific impulses nearly twice that of the best chemical propulsion systems. Space fission power systems (which may eventually enable Nuclear Electric Propulsion) have been flown in space by both the United States and the Former Soviet Union. Fission is the most developed and understood of the nuclear propulsion options (e.g. fission, fusion, antimatter, etc.), and fission has enjoyed tremendous terrestrial success for nearly 7 decades. Current space nuclear research and technology efforts are focused on devising and developing first generation systems that are safe, reliable and affordable. For propulsion, the focus is on nuclear thermal rockets that build on technologies and systems developed and tested under the Rover/NERVA and related programs from the Apollo era. NTP Affordability is achieved through use of previously developed fuels and materials, modern analytical techniques and test strategies, and development of a small engine for ground and flight technology demonstration. Initial NTP systems will be capable of achieving an Isp of 900 s at a relatively high thrust-to-weight ratio. The development and use of first generation space fission power and propulsion systems will provide new, game changing capabilities for NASA. In addition, development and use of these systems will provide the foundation for developing extremely advanced power and propulsion systems capable of routinely and affordably accessing any point in the solar system. The energy density of fissile fuel (8 x 10(exp 13) Joules/kg) is more than adequate for enabling extensive exploration and utilization of the solar system. For space fission propulsion systems, the key is converting the virtually unlimited energy of fission into thrust at the desired specific impulse and thrust-to-weight ratio. This presentation will discuss potential space fission propulsion options ranging from first generation systems to highly advanced systems. Ongoing research that shows promise for enabling second generation NTP systems with Isp greater than 1000 s will be discussed, as will the potential for liquid, gas, or plasma core systems. Space fission propulsion systems could also be used in conjunction with simple (water-based) propellant depots to enable routine, affordable missions to various destinations (e.g. moon, Mars, asteroids) once in-space infrastructure is sufficiently developed. As fuel and material technologies advance, very high performance Nuclear Electric Propulsion (NEP) systems may also become viable. These systems could enable sophisticated science missions, highly efficient cargo delivery, and human missions to numerous destinations. Commonalities between NTP, fission power systems, and NEP will be discussed.

  16. The categorical space of fission

    Microsoft Academic Search

    Luciano G Moretto; Gordon J Wozniak

    1989-01-01

    The dualistic view of fission and evaporation as two distinct compound nucleus processes is substituted with a unified view\\u000a in which fission, complex fragment emission and light particle evaporation are seen as part of a single process. The underlying\\u000a connection between these decay modes is the mass asymmetry coordinate and the ridge line as the locus of the associated conditional

  17. The Microscopic Theory of Fission

    SciTech Connect

    Younes, W; Gogny, D

    2009-06-09

    Fission-fragment properties have been calculated for thermal neutron-induced fission on a {sup 239}Pu target, using constrained Hartree-Fock-Bogoliubov calculations with a finite-range effective interaction. A quantitative criterion based on the interaction energy between the nascent fragments is introduced to define the scission configurations. The validity of this criterion is benchmarked against experimental measurements of the kinetic energies and of multiplicities of neutrons emitted by the fragments.

  18. Perchlorate removal by quaternary amine modified reed

    Microsoft Academic Search

    Salem Baidas; Baoyu Gao; Xiaoguang Meng

    2011-01-01

    We report a kinetic and equilibrium study of perchlorate adsorption onto giant reed modified by quaternary amine (QA) functional groups in batch reactors. The effect of pH, contact time, and initial perchlorate concentration on removal was investigated. The adsorption capacity for perchlorate was 169mg\\/g on the modified reed (MR) particles ranging in size from 100 to 250?m. The isotherm results

  19. Hydration effects in quaternary amine extraction systems

    Microsoft Academic Search

    J. D. Miller; M. C. Fuerstenau

    1970-01-01

    The extraction of Al+++, Cd++, Co++, Cu+, Cu++, Fe++, Fe+++, In+++, Ni++, and Zn++ with quaternary amine was studied using chloride and sulfate as ligands. On the basis of loading experiments and slope analyses,\\u000a the species extracted were: CdCl4=, CoCl4=, CuCl2?, CuCl4=, FeCl4?, and ZnCl4=. Water content of the organic phase was analyzed as a function of loading by Karl

  20. Palladium-catalyzed asymmetric quaternary stereocenter formation.

    PubMed

    Gottumukkala, Aditya L; Matcha, Kiran; Lutz, Martin; de Vries, Johannes G; Minnaard, Adriaan J

    2012-05-29

    An efficient palladium catalyst is presented for the formation of benzylic quaternary stereocenters by conjugate addition of arylboronic acids to a variety of ?,?-disubstituted carbocyclic, heterocyclic, and acyclic enones. The catalyst is readily prepared from PdCl(2), PhBOX, and AgSbF(6), and provides products in up to 99% enantiomeric excess, with good yields. Based on this strategy, (-)-?-cuparenone has been prepared in only two steps. PMID:22532469

  1. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...2011-07-01 false Quaternary ammonium salt of fluorinated alkylaryl amide. 721...Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl amide. ...identified generically as quaternary ammonium salt of fluorinated alkylaryl amide...

  2. 40 CFR 721.9075 - Quaternary ammonium salt of fluorinated alkylaryl amide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...2010-07-01 false Quaternary ammonium salt of fluorinated alkylaryl amide. 721...Substances § 721.9075 Quaternary ammonium salt of fluorinated alkylaryl amide. ...identified generically as quaternary ammonium salt of fluorinated alkylaryl amide...

  3. Compact fission counter for DANCE

    SciTech Connect

    Wu, C Y; Chyzh, A; Kwan, E; Henderson, R; Gostic, J; Carter, D; Bredeweg, T; Couture, A; Jandel, M; Ullmann, J

    2010-11-06

    The Detector for Advanced Neutron Capture Experiments (DANCE) consists of 160 BF{sub 2} crystals with equal solid-angle coverage. DANCE is a 4{pi} {gamma}-ray calorimeter and designed to study the neutron-capture reactions on small quantities of radioactive and rare stable nuclei. These reactions are important for the radiochemistry applications and modeling the element production in stars. The recognition of capture event is made by the summed {gamma}-ray energy which is equivalent of the reaction Q-value and unique for a given capture reaction. For a selective group of actinides, where the neutron-induced fission reaction competes favorably with the neutron capture reaction, additional signature is needed to distinguish between fission and capture {gamma} rays for the DANCE measurement. This can be accomplished by introducing a detector system to tag fission fragments and thus establish a unique signature for the fission event. Once this system is implemented, one has the opportunity to study not only the capture but also fission reactions. A parallel-plate avalanche counter (PPAC) has many advantages for the detection of heavy charged particles such as fission fragments. These include fast timing, resistance to radiation damage, and tolerance of high counting rate. A PPAC also can be tuned to be insensitive to {alpha} particles, which is important for experiments with {alpha}-emitting actinides. Therefore, a PPAC is an ideal detector for experiments requiring a fast and clean trigger for fission. A PPAC with an ingenious design was fabricated in 2006 by integrating amplifiers into the target assembly. However, this counter was proved to be unsuitable for this application because of issues related to the stability of amplifiers and the ability to separate fission fragments from {alpha}'s. Therefore, a new design is needed. A LLNL proposal to develop a new PPAC for DANCE was funded by NA22 in FY09. The design goal is to minimize the mass for the proposed counter and still be able to maintain a stable operation under extreme radioactivity and the ability to separate fission fragments from {alpha}'s. In the following sections, the description is given for the design and performance of this new compact PPAC, for studying the neutron-induced reactions on actinides using DANCE at LANL.

  4. Thorium-uranium fission radiography

    NASA Technical Reports Server (NTRS)

    Haines, E. L.; Weiss, J. R.; Burnett, D. S.; Woolum, D. S.

    1976-01-01

    Results are described for studies designed to develop routine methods for in-situ measurement of the abundance of Th and U on a microscale in heterogeneous samples, especially rocks, using the secondary high-energy neutron flux developed when the 650 MeV proton beam of an accelerator is stopped in a 42 x 42 cm diam Cu cylinder. Irradiations were performed at three different locations in a rabbit tube in the beam stop area, and thick metal foils of Bi, Th, and natural U as well as polished silicate glasses of known U and Th contents were used as targets and were placed in contact with mica which served as a fission track detector. In many cases both bare and Cd-covered detectors were exposed. The exposed mica samples were etched in 48% HF and the fission tracks counted by conventional transmitted light microscopy. Relative fission cross sections are examined, along with absolute Th track production rates, interaction tracks, and a comparison of measured and calculated fission rates. The practicality of fast neutron radiography revealed by experiments to data is discussed primarily for Th/U measurements, and mixtures of other fissionable nuclei are briefly considered.

  5. Singlet exciton fission in solution.

    PubMed

    Walker, Brian J; Musser, Andrew J; Beljonne, David; Friend, Richard H

    2013-12-01

    Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermolecular coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solutions of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene molecule. The intermediate breaks up when the two triplets separate to each TIPS-pentacene molecule. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight. PMID:24256865

  6. Singlet exciton fission in solution

    NASA Astrophysics Data System (ADS)

    Walker, Brian J.; Musser, Andrew J.; Beljonne, David; Friend, Richard H.

    2013-12-01

    Singlet exciton fission, the spin-conserving process that produces two triplet excited states from one photoexcited singlet state, is a means to circumvent the Shockley-Queisser limit in single-junction solar cells. Although the process through which singlet fission occurs is not well characterized, some local order is thought to be necessary for intermolecular coupling. Here, we report a triplet yield of 200% and triplet formation rates approaching the diffusion limit in solutions of bis(triisopropylsilylethynyl (TIPS)) pentacene. We observe a transient bound excimer intermediate, formed by the collision of one photoexcited and one ground-state TIPS-pentacene molecule. The intermediate breaks up when the two triplets separate to each TIPS-pentacene molecule. This efficient system is a model for future singlet-fission materials and for disordered device components that produce cascades of excited states from sunlight.

  7. Mitochondrial Fusion and Fission in Mammals

    E-print Network

    Chan, David

    Mitochondrial Fusion and Fission in Mammals David C. Chan Division of Biology, California Institute dynamics, organelle morphology, membrane fusion, membrane trafficking Abstract Eukaryotic cells maintain. Unbalanced fission leads to mitochondrial fragmentation, and un- balanced fusion leads to mitochondrial

  8. Quantum efficiency and fission rate in tetracene

    E-print Network

    Wu, Tony Chang-Chi

    2013-01-01

    Using singlet fission in a photovoltaic cell, the theoretical energy conversion efficiency limit is larger than the Shockley-Queisser limit due to two excitons produced with one incident photon. In a singlet fission material, ...

  9. Reexamination of fission fragment angular distributions and the fission process: Analysis of data

    SciTech Connect

    Bond, P.D.

    1985-08-01

    A reanalysis of selected fission fragment angular distributions is made using formulae derived in the previous paper. In contrast to previous results it is concluded that the recent heavy-ion-induced fission data is consistent with standard assumptions of fission, although it is suggested that incomplete fusion plays a major role in high energy heavy ion collisions leading to fission.

  10. Neck Influence on Fission Paths

    SciTech Connect

    Gherghescu, Radu A.; Poenaru, D. N. [Horia Hulubei National Institute of Physics and Nuclear Engineering (IFIN-HH), P O Box MG-6, RO 077125 Bucharest-Magurele (Romania)

    2008-01-24

    The neck region generates a microscopic potential, derived in correlation with the necking region within the fission-like shape on the potential theory basis. The whole microscopic potential is of the two-center type, yielding the evolution of proton and neutron level schemes from one parent to two completely separated fragment nuclei. The shell corrections are calculated using the neck in single-particle levels. The total deformation energy is obtained from the macroscopic-microscopic method. As an application, dynamic calculation is performed for the fission of {sup 236}Pu, using the multidimensional minimization within the total space of deformation of two spheroids joined by a smoothed necking region.

  11. Ballistic piston fissioning plasma experiment.

    NASA Technical Reports Server (NTRS)

    Miller, B. E.; Schneider, R. T.; Thom, K.; Lalos, G. T.

    1971-01-01

    The production of fissioning uranium plasma samples such that the fission fragment stopping distance is less than the dimensions of the plasma is approached by using a ballistic piston device for the compression of uranium hexafluoride. The experimental apparatus is described. At room temperature the gun can be loaded up to 100 torr UF6 partial pressure, but at compression a thousand fold increase of pressure can be obtained at a particle density on the order of 10 to the 19th power per cu cm. Limited spectral studies of UF6 were performed while obtaining the pressure-volume data. The results obtained and their implications are discussed.

  12. Process for treating fission waste. [Patent application

    DOEpatents

    Rohrmann, C.A.; Wick, O.J.

    1981-11-17

    A method is described for the treatment of fission waste. A glass forming agent, a metal oxide, and a reducing agent are mixed with the fission waste and the mixture is heated. After melting, the mixture separates into a glass phase and a metal phase. The glass phase may be used to safely store the fission waste, while the metal phase contains noble metals recovered from the fission waste.

  13. Multiple-Coincidence Interrogation of Fissionables

    SciTech Connect

    J.P. Hurley, R.P. Keegan, J.R. Tinsley, R. Trainham

    2009-05-01

    The multiple coincidence technique uses 14.1 MeV neutrons to produce (n, multiple-?) coincidences to detect fissile and fissionable materials. Measurements of n-?-? coincidences with targets of depleted uranium (DU), W, and Pb, show that the counting rate for the DU is substantially above that for the non-fissionables. Also, the data involving prompt neutrons and delayed gammas in the DU time spectra provide a signature for fissionables that is distinct from that of non-fissionables.

  14. Surface Micellization Patterns of Quaternary Ammonium Surfactants on Mica

    E-print Network

    Aksay, Ilhan A.

    Surface Micellization Patterns of Quaternary Ammonium Surfactants on Mica Heather N. Patrick equilibrium structures of adsorbed films of quaternary ammonium surfactants on mica have been investigated never been reported on graphite. Mica is a model hydrophilic surface and has been previously used

  15. Late Quaternary history of Washington Land, North Greenland OLE BENNIKE

    E-print Network

    Ingólfsson, Ólafur

    Late Quaternary history of Washington Land, North Greenland OLE BENNIKE Bennike, O. 2002 (September): Late Quaternary history of Washington Land, North Greenland. Boreas, Vol. 31, 260­272. Oslo. ISSN 0300-9483. During the last glacial stage, Washington Land in western North Greenland was probably completely inun

  16. Uplift of quaternary shorelines in eastern Patagonia: Darwin revisited

    Microsoft Academic Search

    Kevin Pedoja; Vincent Regard; Laurent Husson; Joseph Martinod; Benjamin Guillaume; Enrique Fucks; Maximiliano Iglesias; Pierre Weill

    2011-01-01

    During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the repartition of the Quaternary coastal sequences

  17. Quaternary seismo-tectonic activity of the Polochic Fault, Guatemala

    E-print Network

    Paris-Sud XI, Université de

    Quaternary seismo-tectonic activity of the Polochic Fault, Guatemala Christine Authemayou,1 transform boundary between the North American and Caribbean plates in Guatemala and the associated seismic), Quaternary seismo-tectonic activity of the Polochic Fault, Guatemala, J. Geophys. Res., 117, B07403, doi:10

  18. Sorption and desorption of quaternary amine cations on clays

    Microsoft Academic Search

    Z. Zhong Zhang; Donald L. Sparks; Noel C. Scrivner

    1993-01-01

    The authors have studied the sorption and desorption of three quaternary amines, namely, nonyltrimethylammonium, dodecyltrimethylammonium, and hexadecyltrimethylammonium, on homoionic Na- and K-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were sorbed on the montmorillonite when the added amines were less than 70% of the cation-exchange capacity of the montmorillonite. Sorption of

  19. Neutronics for critical fission reactors and subcritical fission in hybrids

    NASA Astrophysics Data System (ADS)

    Salvatores, Massimo

    2012-06-01

    The requirements of future innovative nuclear fuel cycles will focus on safety, sustainability and radioactive waste minimization. Critical fast neutron reactors and sub-critical, external source driven systems (accelerator driven and fusion-fission hybrids) have a potential role to meet these requirements in view of their physics characteristics. This paper provides a short introduction to these features.

  20. Neutronics for critical fission reactors and subcritical fission in hybrids

    SciTech Connect

    Salvatores, Massimo [CEA-Cadarache, DEN-Dir, Bat. 101, St-Paul-Lez-Durance 13108 (France)

    2012-06-19

    The requirements of future innovative nuclear fuel cycles will focus on safety, sustainability and radioactive waste minimization. Critical fast neutron reactors and sub-critical, external source driven systems (accelerator driven and fusion-fission hybrids) have a potential role to meet these requirements in view of their physics characteristics. This paper provides a short introduction to these features.

  1. Towards a quaternary time scale*1

    NASA Astrophysics Data System (ADS)

    Berggren, W. A.; Burckle, L. H.; Cita, M. B.; Cooke, H. B. S.; Funnell, B. M.; Gartner, S.; Hays, J. D.; Kennett, J. P.; Opdyke, N. D.; Pastouret, L.; Shackleton, N. J.; Takayanagi, Y.

    1980-05-01

    Nine first-appearance datums (FADs), twenty-three last-appearance datums (LADs), and three other micropaleontological datums are related to the magnetic-reversal, oxygen-isotope, and calcite-dissolution/coarse-fraction time scales to provide a preliminary basis for subdivision of the Quaternary in deep-sea sediments. The magnetic-reversal, oxygen-isotope, and calcite-dissolution/coarse-fraction scales have been correlated by determination on the same core materials, and absolute dates applied by {40K}/{40Ar} or 14C dating of materials in known positions on one or another of these scales. FADS and LADs have been determined in cores for which either a magnetic-reversal, oxygen-isotope, or calcite-dissolution/coarse-fraction scale has also been available. Altogether 3 FADs and 5 LADs based on diatoms, 4 FADs and 5 LADs based on calcareous nannoplankton, 1 FAD and 8 LADs based on radiolarians, 1 FAD and 5 LADs based on planktonic foraminifers, 2 acme datums, and 1 ratio reversal datum have been determined, and absolute dates inferred by interpolation from known dates on the reference time scales. Some of the FADs and LADs apply or are synchronous only over limited areas of the oceans; others appear to be synchronous throughout the oceans. The base of the Quaternary is set at the top of the Olduvai event at 1.7 my. Four FADs, twelve LADs, two acme datums, and one ratio reversal datum occur above the base of the Quaternary at an average rate of about 1 per 100,000 yr. Five FADs and twelve LADs are recognized in the 0.8-my interval between the top of the Olduvai event and the Gauss/Matuyama Boundary at 2.5 my at an average incidence of about 1 per 50,000 yr.

  2. Our 50-year odyssey with fission: Summary

    Microsoft Academic Search

    Nix

    1989-01-01

    On the occasion of this International Conference on Fifty Years Research in Nuclear Fission, we summarize our present understanding of the fission process and the challenges that lie ahead. The basic properties of fission arise from a delicate competition between disruptive Coulomb forces, cohesive nuclear forces, and fluctuating shell and pairing forces. These static forces are primarily responsible for such

  3. Summary: Our 50-year odyssey with fission

    Microsoft Academic Search

    J. Rayford Nix

    1989-01-01

    On the occasion of this International Conference on Fifty Years Research in Nuclear Fission, we summarize our present understanding of the fission process and the challenges that lie ahead. The basic properties of fission arise from a delicate competition between disruptive Coulomb forces, cohesive nuclear forces and fluctuating shell and pairing forces. These static forces are primarily responsible for such

  4. FISSION-PRODUCT CAPTURE CROSS SECTIONS

    Microsoft Academic Search

    J. D. Garrison; B. W. Roos

    1962-01-01

    Experimental measurements of fission product capture cross sections and ; statistical estimates of capture cross sections for energies at which no ; measurements have been made yielded a set of group cross sections for primary and ; secondary fission products covering the complete range of energies of interest ; for reactor calculations. Capture cross sections and fission product yield ;

  5. Space Fission Propulsion System Development Status

    Microsoft Academic Search

    M. Houts; M. K. Van Dyke; T. J. Godfroy; K. W. Pedersen; J. J. Martin; R. Dickens; E. Williams; R. Harper; P. Salvail; I. Hrbud

    2001-01-01

    The world's first man-made self-sustaining fission reaction was achieved in 1942. Since then fission has been used to propel submarines, generate tremendous amounts of electricity, produce medical isotopes, and provide numerous other benefits to society. Fission systems operate independently of solar proximity or orientation, and are thus well suited for deep space or planetary surface missions. In addition, the fuel

  6. Fission products of transuranium elements in space

    Microsoft Academic Search

    Iu. A. Shukoliukov; V. M. Dang

    1984-01-01

    The current status of the problem of transuranium elements in space is reviewed. Particular attention is given to Pu-244 fission products in eucrite achondrites; xenon as a fission product in chondrites; the isotopic composition of Xe in meteorites and the evolution of the earth's atmosphere; anomalies of the isotopic composition of uranium in meteorites; the contribution of fission products to

  7. Quaternary vertebrates from Greenland: A review

    NASA Astrophysics Data System (ADS)

    Bennike, Ole

    Remains of fishes, birds and mammals are rarely reported from Quaternary deposits in Greenland. The oldest remains come from Late Pliocene and Early Pleistocene deposits and comprise Atlantic cod, hare, rabbit and ringed seal. Interglacial and interstadial deposits have yielded remains of cod, little auk, collared lemming, ringed seal, reindeer and bowhead whale. Early and Mid-Holocene finds include capelin, polar cod, red fish, sculpin, three-spined stickleback, Lapland longspur, Arctic hare, collared lemming, wolf, walrus, ringed seal, reindeer and bowhead whale. It is considered unlikely that vertebrates could survive in Greenland during the peak of the last glaciation, but many species had probably already immigrated in the Early Holocene.

  8. New ternary and quaternary group IV tellurides

    SciTech Connect

    Keane, P.M.

    1992-01-01

    As a continuation of the interest in ternary transition-metal chalcogenides, the exploration of the ternary and quaternary Group IV tellurides, a class of compound largely unexplored, has been undertaken. For this particular system, the reactive flux method proves to be an invaluable crystallization and synthetic technique. These reactions have yielded several new phases, the majority of which represent unprecedented structure types. The compounds K[sub 4]M[sub 3]Te[sub 17] (M = Zr, Hf) contain one-dimensional [sup 1][sub [infinity

  9. Antibacterial activity of gemini quaternary ammonium salts.

    PubMed

    Ob??k, Ewa; Piecuch, Agata; Guz-Regner, Katarzyna; Dworniczek, Ewa

    2014-01-01

    A series of gemini quaternary ammonium salts (chlorides and bromides), with various hydrocarbon chain and spacer lengths, were tested. These compounds exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria and were not mutagenic. The strongest antibacterial effect was observed for TMPG-10 Cl (against Pseudomonas aeruginosa ATCC 27853) and TMPG-12 Br (against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 11229 and clinical ESBL(+) isolate 434) surfactants. These compounds inhibited the adhesion of Staphylococcus epidermidis ATCC 35984 to a polystyrene surface and eradicated biofilm formed by P. aeruginosa PAO1. The activity of studied compounds was dependent on hydrocarbon chain length. PMID:24236547

  10. Late-quaternary shift of fagus distribution

    Microsoft Academic Search

    Matsuo Tsukada

    1982-01-01

    Based on six resolved maps of its pollen frequency (dating 13,000, 10,000, 8,000, 6,000, 3,000 and 500 yr B.P.) at 33 sites\\u000a scattered almost throughout the Japanese Archipelago,Fagus shows principally a, unidirectional late-Quaternary shift in distribution from the southwest to the northeast. The maximum\\u000a areal coverage was from 10,000 to 7,000 years ago, although northeastern populations were not fully developed

  11. Fifty years with nuclear fission

    Microsoft Academic Search

    J. W. Behrens; A. D. Carlson

    1989-01-01

    The news of the discovery of nucler fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fiftieth anniversary of its discovery by holding a

  12. Space Fission System Test Effectiveness

    NASA Astrophysics Data System (ADS)

    Houts, Mike; Schmidt, Glen L.; van Dyke, Melissa; Godfroy, Tom; Martin, James; Bragg-Sitton, Shannon; Dickens, Ricky; Salvail, Pat; Harper, Roger

    2004-02-01

    Space fission technology has the potential to enable rapid access to any point in the solar system. If fission propulsion systems are to be developed to their full potential, however, near-term customers need to be identified and initial fission systems successfully developed, launched, and utilized. One key to successful utilization is to develop reactor designs that are highly testable. Testable reactor designs have a much higher probability of being successfully converted from paper concepts to working space hardware than do designs which are difficult or impossible to realistically test. ``Test Effectiveness'' is one measure of the ability to realistically test a space reactor system. The objective of this paper is to discuss test effectiveness as applied to the design, development, flight qualification, and acceptance testing of space fission systems. The ability to perform highly effective testing would be particularly important to the success of any near-term mission, such as NASA's Jupiter Icy Moons Orbiter, the first mission under study within NASA's Project Prometheus, the Nuclear Systems Program.

  13. Space Fission System Test Effectiveness

    SciTech Connect

    Houts, Mike [Los Alamos National Laboratory, MS-K575, Los Alamos, NM 87545 (United States); Schmidt, Glen L. [New Mexico Tech, Institute for Engineering Research and Applications, 901 University Blvd SE, Albuquerque, NM 87109-4339 (United States); Van Dyke, Melissa; Godfroy, Tom; Martin, James; Bragg-Sitton, Shannon; Dickens, Ricky; Salvail, Pat; Harper, Roger [NASA MSFC, TD40, Marshall Space Flight Center, AL, 35812 (United States)

    2004-02-04

    Space fission technology has the potential to enable rapid access to any point in the solar system. If fission propulsion systems are to be developed to their full potential, however, near-term customers need to be identified and initial fission systems successfully developed, launched, and utilized. One key to successful utilization is to develop reactor designs that are highly testable. Testable reactor designs have a much higher probability of being successfully converted from paper concepts to working space hardware than do designs which are difficult or impossible to realistically test. ''Test Effectiveness'' is one measure of the ability to realistically test a space reactor system. The objective of this paper is to discuss test effectiveness as applied to the design, development, flight qualification, and acceptance testing of space fission systems. The ability to perform highly effective testing would be particularly important to the success of any near-term mission, such as NASA's Jupiter Icy Moons Orbiter, the first mission under study within NASA's Project Prometheus, the Nuclear Systems Program.

  14. Binary fission via lnviscid Trajectories

    Microsoft Academic Search

    N. R. Lebovitz

    1987-01-01

    We sketch an evolutionary picture which, unlike the classical picture, appears favorable to the hypothesis that close binary stars originate in the fission of a single slowly contracting protostar. The main differences from the classical picture are (1) evolution proceeds along certain families of Riemann ellipsoids, rather than along the Jacobi family and (2) the critical ellipsoid on the evolutionary

  15. Etching fission tracks in zircons

    USGS Publications Warehouse

    Naeser, C.W.

    1969-01-01

    A new technique has been developed whereby fission tracks can be etched in zircon with a solution of sodium hydroxide at 220??C. Etching time varied between 15 minutes and 5 hours. Colored zircon required less etching time than the colorless varieties.

  16. The role of Quaternary environmental change in plant macroevolution: the exception or the rule?

    Microsoft Academic Search

    Katherine J. Willis; Karl J. Niklas

    2004-01-01

    The Quaternary has been described as an important time for genetic diversification and speciation. This is based on the premise that Quaternary climatic conditions fostered the isolation of populations and, in some instances, allopatric speciation. However, the 'Quaternary Ice-Age speciation model' rests on two key assumptions: (i) that biotic responses to climate change during the Quaternary were significantly different from

  17. Quaternary glaciation of tibet: The geological evidence

    NASA Astrophysics Data System (ADS)

    Derbyshire, Edward; Shi Yafeng; Li Jijun; Zheng Benxing; Li Shijie; Wang Jingtai

    The question of the number and extent of Pleistocene glaciations on the Qinghai-Xizang (Tibet) Plateau remains contentious. There has been considerable research activity in Tibet by Chinese scientists since the late 1950s and their principal findings, including data on glacial and periglacial geomorphology, sedimentology, tectonics, stratigraphy and lake history, have been used to reconstruct ice margins and palaeosnowlines. Three, and in places, four distinct glaciations have been recognised, the most extensive occurring in the later Middle Pleistocene. Valley and piedmont glacial systems, with some mountain ice caps and a small ice sheet on the upper reaches of the Huang He, have been recognised but there is no evidence of a single Tibetan ice sheet. As the Plateau and the Himalaya-Karakoram underwent accelerating uplift through the Quaternary, there occurred progressive desiccation in the interior as the influx of Indian Ocean moisture was constrained. Equilibrium line elevations in the last glacial maximum were 4000 m in the south, east and northeast Plateau margins, rising to 5500 m in the northwest interior. The heat island provided by the Plateau, the progressive reduction in precipitation most marked during the glacials, and the strong southeast to northwest precipitation gradients, produced a glacier distribution pattern dominated by the trans-Tibetan mountain ranges. Tectonics and periglacial (including aeolian) processes have played an equal role with glaciation in generating the Plateau's Quaternary sedimentary succession.

  18. Fission dynamics at low excitation energy

    E-print Network

    Y. Aritomo; S. Chiba

    2013-10-14

    The origin of mass asymmetry in the fission of uranium at a low excitation energy is clarified by a trajectory analysis of the Langevin equation. The positions of the peaks in the mass distribution of fission fragments are mainly determined by fission saddle points originating from the shell correction energy. The widths of the peaks, on the other hand, result from a shape fluctuation around the scission point caused by the random force in the Langevin equation. We found that a random vibration in the oblate direction of fissioning fragments is essential for the fission process. According to this picture, fission does not occur with continuous stretching in the prolate direction, similarly to that observed in starch syrup. This is expected to lead to a new viewpoint of fission dynamics and the splitting mechanism.

  19. DSP Algorithms for Fission Fragment and Prompt Fission Neutron Spectroscopy

    SciTech Connect

    Zeynalova, O. [Moscow State Institute of Radioengineering, Electronics and Automation 78, Vernadski Avenue, 119454 Moscow (Russian Federation); Joint Institute for Nuclear Research, Joliot Curie 6, Dubna, Moscow region (Russian Federation); Zeynalov, Sh. [Joint Institute for Nuclear Research, Joliot Curie 6, Dubna, Moscow region (Russian Federation); European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, 2440 Geel (Belgium); Hambsch, F.-J.; Oberstedt, S.; Fabry, I. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, 2440 Geel (Belgium)

    2009-10-29

    Digital signal processing (DSP) algorithms are in high demand for modern nuclear fission investigation due to importance of increase the accuracy of fissile nuclear data for new generation of nuclear power stations. DSP algorithms for fission fragment (FF) and prompt fission neutron (PFN) spectroscopy are described in the present work. The twin Frisch-grid ionization chamber (GTIC) is used to measure the kinetic energy-, mass- and angular distributions of the FF in the {sup 252}Cf(SF) reaction. Along with the neutron time-of-flight (TOF) measurement the correlation between neutron emission and FF mass and energy is investigated. The TOF is measured between common cathode of the GTIC and the neutron detector (ND) pulses. Waveform digitizers (WFD) having 12 bit amplitude resolution and 100 MHz sampling frequency are used for the detector pulse sampling. DSP algorithms are developed as recursive procedures to perform the signal processing, similar to those available in various nuclear electronics modules, such as constant fraction discriminator (CFD), pulse shape discriminator (PSD), peak-sensitive analogue-to-digital converter (pADC) and pulse shaping amplifier (PSA). To measure the angle between FF and the cathode plane normal to the GTIC a new algorithm is developed having advantage over the traditional analogue pulse processing schemes. Algorithms are tested by comparing the numerical simulation of the data analysis of the {sup 252}Cf(SF) reaction with data available from literature.

  20. Antimicrobial Polymeric Materials with Quaternary Ammonium and Phosphonium Salts

    PubMed Central

    Xue, Yan; Xiao, Huining; Zhang, Yi

    2015-01-01

    Polymeric materials containing quaternary ammonium and/or phosphonium salts have been extensively studied and applied to a variety of antimicrobial-relevant areas. With various architectures, polymeric quaternary ammonium/phosphonium salts were prepared using different approaches, exhibiting different antimicrobial activities and potential applications. This review focuses on the state of the art of antimicrobial polymers with quaternary ammonium/phosphonium salts. In particular, it discusses the structure and synthesis method, mechanisms of antimicrobial action, and the comparison of antimicrobial performance between these two kinds of polymers. PMID:25667977

  1. A quaternary temperament model and defense cluster preferences.

    PubMed

    Kelly, Kathryn E; Tobacyk, Jerome J

    2003-10-01

    A quaternary model of temperament constructed from orthogonal axes defined by Extraversion-Introversion and Thinking-Feeling resulted in four groups: Introverted Thinking, Introverted Feeling, Extraverted Thinking, and Extraverted Feeling. Hypothesized relationships between quaternary groups and defense cluster preferences were tested by giving 158 female college students the Myers-Briggs Type Indicator and the Defense Mechanisms Inventory. There was little support for hypothesized relationships between the quaternary model and defense preferences. The only hypothesized significant group difference showed the Extraverted Feeling group recording a greater preference for the Reversal defense cluster than the Introverted Feeling group. PMID:14650666

  2. Biocide comparison: Aldehyde versus mixture of aldehyde and quaternary amine

    SciTech Connect

    Prasad, R. [Champion Technologies, Inc., Houston, TX (United States)

    1994-12-31

    Glutaraldehyde and quaternary ammonium chloride salts are widely used biocides in oil field systems to control microbiologically influenced corrosion (MIC). These biocides and others were evaluated for their efficacy to control sessile and planktonic sulfate reducing bacteria (SRB) and aerobic bacteria. The efficacy of these biocides was then compared. In addition to laboratory evaluation, all the biocides were evaluated against SRB and acid producing bacteria in two different field waters. It was found that the blend containing aldehyde and quaternary amino was, in general, a more effective biocide than either glutaraldehyde or quaternary amine alone.

  3. Fission Properties for R-Process Nuclei

    SciTech Connect

    Erler, J. [Inst. fur Theoretische Physik II, Univ. Erlangen-Numberg, Germany/UTK/ORNL; Langanke, K. [GSI-Darmstadt/Tech. Univ. Darmstadt, Inst. Phys./Frankfurt Inst. Advanced Studies, Germany; Loens, H. P. [GSI-Darmstadt/Tech. Univ. Darmstadt, Inst. Phys.; Martinez-Pinedo, G. [GSI-Darmstadt/Tech. Univ. Darmstadt, Inst. Phys.; Reinhard, P.-G. [Inst. fur Theoretische Physik II, Univ. Erlangen-Numberg, Germany

    2012-01-01

    We present a systematics of fission barriers and fission lifetimes for the whole landscape of superheavy elements (SHE), i.e., nuclei with Z 100. The fission lifetimes are also compared with the -decay half-lives. The survey is based on a self-consistent description in terms of the Skyrme-Hartree-Fock (SHF) approach. Results for various different SHF parametrizations are compared to explore the robustness of the predictions. The fission path is computed by quadrupole constrained SHF. The computation of fission lifetimes takes care of the crucial ingredients of the large-amplitude collective dynamics along the fission path, as self-consistent collective mass and proper quantum corrections. We discuss the different topologies of fission landscapes which occur in the realm of SHE (symmetric versus asymmetric fission, regions of triaxial fission, bimodal fission, and the impact of asymmetric ground states). The explored region is extended deep into the regime of very neutron-rich isotopes as they are expected to be produced in the astrophysical r process.

  4. Mobility of fission gas bubbles

    Microsoft Academic Search

    F. A. Nichols; C. Ronchi

    1985-01-01

    The importance of bubble migration in fuel swelling and fission-product release remains a controversial topic in spite of a great deal of research. For steady-state analyses some authors ignore bubble motion totally, whereas others employ mobilities (based on out-of-pile measurements) which are far below the theoretical diffusion-control predictions. Under transient conditions some continue to employ zero or low bubble mobilities,

  5. Quaternary coral reef refugia preserved fish diversity.

    PubMed

    Pellissier, Loïc; Leprieur, Fabien; Parravicini, Valeriano; Cowman, Peter F; Kulbicki, Michel; Litsios, Glenn; Olsen, Steffen M; Wisz, Mary S; Bellwood, David R; Mouillot, David

    2014-05-30

    The most prominent pattern in global marine biogeography is the biodiversity peak in the Indo-Australian Archipelago. Yet the processes that underpin this pattern are still actively debated. By reconstructing global marine paleoenvironments over the past 3 million years on the basis of sediment cores, we assessed the extent to which Quaternary climate fluctuations can explain global variation in current reef fish richness. Comparing global historical coral reef habitat availability with the present-day distribution of 6316 reef fish species, we find that distance from stable coral reef habitats during historical periods of habitat loss explains 62% of the variation in fish richness, outweighing present-day environmental factors. Our results highlight the importance of habitat persistence during periods of climate change for preserving marine biodiversity. PMID:24876495

  6. On Quaternary glaciations, observations and theories

    NASA Astrophysics Data System (ADS)

    Paillard, D.

    2015-07-01

    In a recent paper, Paillard (2015) presents a rapid overview of both major theoretical and empirical studies of Pleistocene glaciations. In particular, it is explained how, over the last 150 years, astronomical theories were confronted to observational constraints and why the "100-kyr problem" is still the major unsolved issue of Quaternary ice ages. This paper also discusses the main alternative theory, which involves changes in atmospheric carbon dioxide concentration. It is then argued that a synthesis of both theories would better account for empirical evidences, as well as for our current knowledge of climate physics. Indeed, if there is no doubt that ice ages are "paced" by the astronomy as evidenced in Hays et al. (1976), the cause of terminations, and therefore the dynamics of the 100-kyr cycles, appears to be closely linked to Southern Ocean climate and atmospheric pCO2.

  7. Antifungal activity of gemini quaternary ammonium salts.

    PubMed

    Ob??k, Ewa; Piecuch, Agata; Krasowska, Anna; Luczy?ski, Jacek

    2013-12-14

    A series of gemini quaternary ammonium chlorides and bromides with various alkyl chain and spacer lengths was synthesized. The most active compounds against fungi were chlorides with 10 carbon atoms within the hydrophobic chain. Among these compounds were few with no hemolytic activity at minimal inhibitory concentrations. None of the tested compounds were cytotoxic and mutagenic. Cationic gemini surfactants poorly reduced the adhesion of microorganisms to the polystyrene plate, but inhibited the filamentation of Candida albicans. One of the tested compounds eradicated C. albicans and Rodotorula mucilaginosa biofilm, what could be important in overcoming catheter-associated infections. It was also shown that gemini surfactants enhanced the sensitivity of C. albicans to azoles and polyenes, thus they might be potentially used in combined therapy against fungi. PMID:23827647

  8. Suggested terminology for Quaternary dating methods

    USGS Publications Warehouse

    Colman, Steven M.; Pierce, K.L.; Birkeland, P.W.

    1987-01-01

    Classification of Quaternary dating methods should be based on the level of quantitative information and the degree of confidence contained in the age estimates produced by the dating methods. We recommend the use of the terms numerical-age, calibrated-age, relative-age, and correlated-age to describe these levels. We also classify dating methods by type into sideral, isotopic, radiogenic, chemical and biological, geomorphic, and correlation methods. The use of "absolute" is inappropriate for most dating methods, and should be replaced by "numerical." The use of "date" should be minimized in favor of "age" or "age estimate." We recommend use of the abbreviations ka and Ma for most ages; calender dates can be used where appropriate and yr B.P. can be used for radiocarbon ages. ?? 1987.

  9. [Quaternary ammonium compounds--new occupational hazards].

    PubMed

    Lipi?ska-Ojrzanowska, Agnieszka; Walusiak-Skorupa, Jolanta

    2014-01-01

    Quaternary ammonium compounds (QACs, quats) belong to organic ionic chemical agents which display unique properties of both surfactants and disinfectants. Their wide distribution in the work environment and also in private households brings about new occupational hazards. This paper reviews reports about the health effects of QACs. QACs could play a role of sensitizers and irritants to the skin and mucous membranes. It is suspected that particular QACs can display an immunologic cross-reactivity between each other and with other chemical compounds containing ammonium ion, such as muscle relaxants widely used in anesthesia. They may promote the development of airway allergy, however, the background mechanisms are still unclear and need to be further investigated. Until now, a few cases of occupational asthma induced by QACs have been described and their involvement in contact dermatitis has been documented. The possibility of anaphylaxis due to QACs cannot be excluded as well. PMID:25812396

  10. Technical Application of Nuclear Fission

    NASA Astrophysics Data System (ADS)

    Denschlag, J. O.

    The chapter is devoted to the practical application of the fission process, mainly in nuclear reactors. After a historical discussion covering the natural reactors at Oklo and the first attempts to build artificial reactors, the fundamental principles of chain reactions are discussed. In this context chain reactions with fast and thermal neutrons are covered as well as the process of neutron moderation. Criticality concepts (fission factor ?, criticality factor k) are discussed as well as reactor kinetics and the role of delayed neutrons. Examples of specific nuclear reactor types are presented briefly: research reactors (TRIGA and ILL High Flux Reactor), and some reactor types used to drive nuclear power stations (pressurized water reactor [PWR], boiling water reactor [BWR], Reaktor Bolshoi Moshchnosti Kanalny [RBMK], fast breeder reactor [FBR]). The new concept of the accelerator-driven systems (ADS) is presented. The principle of fission weapons is outlined. Finally, the nuclear fuel cycle is briefly covered from mining, chemical isolation of the fuel and preparation of the fuel elements to reprocessing the spent fuel and conditioning for deposit in a final repository.

  11. MODELING AND FISSION CROSS SECTIONS FOR AMERICIUM.

    SciTech Connect

    ROCHMAN, D.; HERMAN, M.; OBLOZINSKY, P.

    2005-05-01

    This is the final report of the work performed under the LANL contract on the modeling and fission cross section for americium isotopes (May 2004-June 2005). The purpose of the contract was to provide fission cross sections for americium isotopes with the nuclear reaction model code EMPIRE 2.19. The following work was performed: (1) Fission calculations capability suitable for americium was implemented to the EMPIRE-2.19 code. (2) Calculations of neutron-induced fission cross sections for {sup 239}Am to {sup 244g}Am were performed with EMPIRE-2.19 for energies up to 20 MeV. For the neutron-induced reaction of {sup 240}Am, fission cross sections were predicted and uncertainties were assessed. (3) Set of fission barrier heights for each americium isotopes was chosen so that the new calculations fit the experimental data and follow the systematics found in the literature.

  12. Fission dynamics within time-dependent Hartree-Fock: deformation-induced fission

    E-print Network

    Goddard, P M; Rios, A

    2015-01-01

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide $^{240}$Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate non-adiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behaviour. Those beginning just beyond the ...

  13. Comparative evaluation of solar, fission, fusion, and fossil energy resources. Part 2: Power from nuclear fission

    NASA Technical Reports Server (NTRS)

    Clement, J. D.

    1973-01-01

    Different types of nuclear fission reactors and fissionable materials are compared. Special emphasis is placed upon the environmental impact of such reactors. Graphs and charts comparing reactor facilities in the U. S. are presented.

  14. The tempo of avian diversification during the Quaternary

    Microsoft Academic Search

    Robert M. Zink; John Klicka; Brian R. Barber

    2004-01-01

    It is generally assumed that the Quaternary was a period of heightened diversification in temperate ver- tebrate organisms. Previous molecular systematics studies have challenged this assertion. We re-examined this issue in north temperate birds using log-lineage plots and distributions of sister-taxon distances. Log- lineage plots support earlier conclusions that avian diversification slowed during the Quaternary. To test plots of empirical

  15. Late quaternary geologic history of the south Texas continental shelf

    E-print Network

    Pyle, Carroll Anthony

    1977-01-01

    LATE QUATERNARY GEOLOGIC HISTORY OF THE SOUTH TEXAS CONTINENTAL SHELF A Thesis CARROLL ANTHONY PYLE Submitted to the Graduate College of Texas AAM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE... December 1977 Major Subject: Oceanography LATE QUATERNARY GEOLOGIC HISTORY OF THE SOUTH TEXAS CONTINENTAL SHELF A Thesis by CARROLL ANTHONY PYLE Approved as to style and content by: (Chairman of Comm tee) (Head of Depar nt) ember) Me ber...

  16. STRIPPING OF GOLD FROM QUATERNARY AMINE EXTRACTION SYSTEMS

    Microsoft Academic Search

    Gang Ma; Wenfei Yan; Jing Chen; Weijin Zhou; Jinguang Wu; Guangxian Xu

    2000-01-01

    A new procedure based on the use of sodium perchlorate (NaC1O4) and saturated potassium chloride (KCl) solutions for gold stripping from quaternary amine extraction systems is proposed for the first time. In this procedure, the stripping of Au(CN)2 is accomplished by the ClO4 ions in the first step, and the regeneration of quaternary amine is achieved by Cl ions in

  17. Fission barriers and half-lives

    SciTech Connect

    Moeller, P.; Nix, J.R.; Swiatecki, W.J.

    1989-01-01

    We briefly review the development of theoretical models for the calculation of fission barriers and half-lives. We focus on how results of actual calculations in a unified macroscopic-microscopic approach provide an interpretation of the mechanisms behind some of the large number of phenomena observed in fission. As instructive examples we choose studies of the rapidly varying fission properties of elements at the end of the periodic system. 31 refs., 10 figs.

  18. Fission Fragment Orientation and ?-RAY Emission Anisotropy

    NASA Astrophysics Data System (ADS)

    Adrich, P.; Kopatch, Yu. N.; Lubkiewicz, E.; Wollersheim, H. J.; Mutterer, M.

    2003-10-01

    Angular correlations of prompt ?-rays in binary spontaneous fission of 252Cf were measured with a GSI super clover detector. The position-sensitive ?-ray spectrometer was combined with an efficient detection system for fission fragments. For the study of ?-ray angular correlations the intensities of individual ?-transitions were measured relative to the fission axis. Surprisingly, the measured ?-ray angular correlations for stretched E2 transitions show a large anisotropy, which can be described by a complete alignment of the initial fragment spins.

  19. Binary fission in damped rotating polytropes. II

    Microsoft Academic Search

    R. A. Gingold; J. J. Monaghan

    1979-01-01

    The fission sequences of Gingold and Monaghan are recomputed using a significantly larger number (800) of particles in the smoothed-particle-hydrodynamic treatment. The results confirm the general mode of fission found earlier for polytropes with n = 0.5. An interesting three-pointed 'star fish' structure is now apparent before fission and a low-mass third object is formed. The nature of the disruption

  20. Monte carlo sampling of fission multiplicity.

    SciTech Connect

    Hendricks, J. S. (John S.)

    2004-01-01

    Two new methods have been developed for fission multiplicity modeling in Monte Carlo calculations. The traditional method of sampling neutron multiplicity from fission is to sample the number of neutrons above or below the average. For example, if there are 2.7 neutrons per fission, three would be chosen 70% of the time and two would be chosen 30% of the time. For many applications, particularly {sup 3}He coincidence counting, a better estimate of the true number of neutrons per fission is required. Generally, this number is estimated by sampling a Gaussian distribution about the average. However, because the tail of the Gaussian distribution is negative and negative neutrons cannot be produced, a slight positive bias can be found in the average value. For criticality calculations, the result of rejecting the negative neutrons is an increase in k{sub eff} of 0.1% in some cases. For spontaneous fission, where the average number of neutrons emitted from fission is low, the error also can be unacceptably large. If the Gaussian width approaches the average number of fissions, 10% too many fission neutrons are produced by not treating the negative Gaussian tail adequately. The first method to treat the Gaussian tail is to determine a correction offset, which then is subtracted from all sampled values of the number of neutrons produced. This offset depends on the average value for any given fission at any energy and must be computed efficiently at each fission from the non-integrable error function. The second method is to determine a corrected zero point so that all neutrons sampled between zero and the corrected zero point are killed to compensate for the negative Gaussian tail bias. Again, the zero point must be computed efficiently at each fission. Both methods give excellent results with a negligible computing time penalty. It is now possible to include the full effects of fission multiplicity without the negative Gaussian tail bias.

  1. Heavy-ion-induced fission - experimental status

    Microsoft Academic Search

    W. U. Schröder; J. R. Huizenga

    1989-01-01

    The process of fission of a composite nucleus produced in heavy-ion collisions is characterized in terms of the experimental kinetic-energy, mass and angular distributions of the fission fragments. Measurements of associated particles, and possibly of gamma-rays, emitted prior to scission demonstrate that heavy-ion fission is an inherently slow (~10-20 - 10-19 s) process that is dominated by overdamped collective motion

  2. Sorption and desorption of quaternary amine cations on clays

    SciTech Connect

    Zhang, Z.Z.; Sparks, D.L. (Univ. of Delaware, Newark, DE (United States)); Scrivner, N.C. (DuPont Engineering, Newark, DE (United States))

    1993-08-01

    The authors have studied the sorption and desorption of three quaternary amines, namely, nonyltrimethylammonium, dodecyltrimethylammonium, and hexadecyltrimethylammonium, on homoionic Na- and K-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were sorbed on the montmorillonite when the added amines were less than 70% of the cation-exchange capacity of the montmorillonite. Sorption of quaternary amine cations involves at least two types of reactions, namely, an exchange reaction and the adsorption of amines at nonexchangeable sites. The exchange reaction proceeded almost to completion when Na[sup +] was the exchangeable cation. Exchangeable K[sup +] was much more difficult to replace. The adsorbed quaternary amine cations were not easily desorbed in the presence of 0.1 M NaCl and KCl solutions. In addition, desorption of quaternary amines did not increase with prolonged equilibrium time, up to 180 days. Therefore, it appears that there is good promise in using quaternary amine-modified clays as effective sorbents for removing organic pollutants or mitigating their mobilities in the environment. 26 refs., 5 figs., 6 tabs.

  3. Calculated medium-energy fission cross sections

    SciTech Connect

    Arthur, E.D.; Young, P.G.

    1988-01-01

    Calculations were made of neutron-induced fission cross sections on /sup 238/U and /sup 237/Np to compare with new data available up to 100 MeV. This process also produced fission barrier parameters for neptunium and uranium compound systems required for calculation of p + /sup 238/U fission cross sections. To achieve reasonable agreement with higher energy neutron-induced fission data, a phenomenological enhancement to barrier heights based upon the average angular momentum of the compound system was required. These calculational procedures resulted in predictions of /sup 238/U(p,f) cross sections that agree well with available data. 7 refs., 2 figs.

  4. Theoretical Description of the Fission Process

    SciTech Connect

    Witold Nazarewicz

    2003-07-01

    The main goals of the project can be summarized as follows: Development of effective energy functionals that are appropriate for the description of heavy nuclei. Our goal is to improve the existing energy density (Skyrme) functionals to develop a force that will be used in calculations of fission dynamics. Systematic self-consistent calculations of binding energies and fission barriers of actinide and trans-actinide nuclei using modern density functionals. This will be followed by calculations of spontaneous fission lifetimes and mass and charge divisions using dynamic adiabatic approaches based on the WKB approximation. Investigate novel microscopic (non-adiabatic) methods to study the fission process.

  5. Experimental investigation into Quaternary badland geomorphic development

    NASA Astrophysics Data System (ADS)

    Kasanin-Grubin, Milica; Kuhn, Nikolaus; Yair, Aaron; Bryan, Rorke; Schwanghart, Wolfgang

    2010-05-01

    Badland morphology is commonly linked to lithological properties of the bedrock. However, recent investigations indicate that the geomorphic development is sensitive to climate and in particular to precipitation characteristics. In this study, the precipitation characteristics that are critical for the Quaternary landscape development in the Dinosaur Badlands in Alberta, Canada, and Zin Valley Badlands, Negev Desert, Israel are investigated. Runoff, erosion and weathering were simulated in the field and the laboratory to determine rates for modeling different precipitation regimes. Currently, the geomorphic development in the Dinosaur badlands is characterized by weathering/supply limited conditions, leading to slope retreat independent of lithology. In the Negev, transport limited conditions cause frequent runoff discontinuity, creating a pattern of areas dominated by erosion or deposition. The results of the weathering and erosion experiments show that the balance between snowmelt induced weathering in the spring and summer rainfall and erosion determine the rate of slope retreat in the Dinosaur Badlands. In the Zin Valley, on the other hand, the magnitude of the individual rainstorms determines whether a slope section is eroded or acts as a sediment sink. The experiments illustrate that the badland slopes experienced an auto-stabilization during the Quaternary in the Zin Valley. In the Dinosaur Badlands Holocene climatic variations have not caused a permanent differentiation of patterns of erosion and deposition. Based on these results the reaction of badland slopes to changing precipitation characteristics was modeled. In their current state, both badland slope systems appear to be fairly stable against climate change in the range of those occurring during the Holocene. However, the stability is achieved in different ways. In the Dinosaur Badlands, weathering rates are low compared to erosion capacity, maintaining continuous evacuation of sediment from slopes to the flood planes of the Red Deer River system. Only a very pronounced contrast between winter weathering and drier summers would generate a colluvium and thus change slope hydrology. In the Zin Valley the development of a thick colluvium at the foot of the slopes has increased infiltration capacity, reducing runoff and sediment yield into the floodplain. Here, only an increase in rainfall magnitude would improve runoff continuity and induce the erosion of the colluvium. This would in turn reduce infiltration capacity and thus initiate a positive feedback on runoff and sediment yield into the Zin River. Overall, Holocene climate change appears to be insufficient to change the geomorphic development in both badlands. However, this stability is achieved not despite of climate, but because of the specific history of geomorphic development. In addition, the combination of erosion and weathering experiments with numerical modeling demonstrates the versatility of Experimental Geomorphology in landscape evolution studies.

  6. Fission dynamics within time-dependent Hartree-Fock: deformation-induced fission

    E-print Network

    P. M. Goddard; P. D. Stevenson; A. Rios

    2015-04-03

    Background: Nuclear fission is a complex large-amplitude collective decay mode in heavy nuclei. Microscopic density functional studies of fission have previously concentrated on adiabatic approaches based on constrained static calculations ignoring dynamical excitations of the fissioning nucleus, and the daughter products. Purpose: To explore the ability of dynamic mean-field methods to describe fast fission processes beyond the fission barrier, using the nuclide $^{240}$Pu as an example. Methods: Time-dependent Hartree-Fock calculations based on the Skyrme interaction are used to calculate non-adiabatic fission paths, beginning from static constrained Hartree-Fock calculations. The properties of the dynamic states are interpreted in terms of the nature of their collective motion. Fission product properties are compared to data. Results: Parent nuclei constrained to begin dynamic evolution with a deformation less than the fission barrier exhibit giant-resonance-type behaviour. Those beginning just beyond the barrier explore large amplitude motion but do not fission, whereas those beginning beyond the two-fragment pathway crossing fission to final states which differ according to the exact initial deformation. Conclusions: Time-dependent Hartree-Fock is able to give a good qualitative and quantitative description of fast fission, provided one begins from a sufficiently deformed state.

  7. HYBRID NUCLEAR CYCLES FOR NUCLEAR FISSION SUSTAINABILITY

    Microsoft Academic Search

    Mireia Piera; José M. Martínez-Val

    Nuclear fission can play and must play an important role in paving the road to Energy Sustainability. Nuclear Fission does not produce CO2 emissions, and it is already exploited at commercial level with the current NPP (Nuclear Power Plants). Most of them are based on LWR reactors, which have a very good safety record. It must be noted, however, that

  8. Nuclear fission sustainability with hybrid nuclear cycles

    Microsoft Academic Search

    José M. Martínez-Val; Mireia Piera

    2007-01-01

    An analysis is presented on the main requirements to develop nuclear fission in the context of social, economic and environmental sustainability. This analysis is mainly focused on maximizing the energy actually generated from the potential contents of fissionable natural resources. The role of fertile to fissile breeding is highlighted, as well as the need of attaining a very high safety

  9. Fission stability diagram of sup 240 Pu

    SciTech Connect

    Garcias, F.; Barranco, M.; Wio, H.S. (Departament de Fisica, Universitat de ses Illes Balears, E-07071 Palma de Mallorca, Spain (ES)); Ngo, C. (Laboratoire National Saturne, F-91191 Gif-sur-Yvette, France); Nemeth, J. (Institute of Theoretical Physics, Eotvos University, H-1088 Budapest, Hungary)

    1989-09-01

    We have used an axially symmetric deformed Thomas-Fermi model to evaluate the fission barrier of {sup 240}Pu as a function of the quadrupole moment {ital Q}{sub 2} for different values of the angular momentum {ital L} and temperature {ital T}. The fission stability diagram of this nucleus is investigated.

  10. Nuclear Power from Fission Reactors. An Introduction.

    ERIC Educational Resources Information Center

    Department of Energy, Washington, DC. Technical Information Center.

    The purpose of this booklet is to provide a basic understanding of nuclear fission energy and different fission reaction concepts. Topics discussed are: energy use and production, current uses of fuels, oil and gas consumption, alternative energy sources, fossil fuel plants, nuclear plants, boiling water and pressurized water reactors, the light…

  11. The binary fission origin of the moon

    Microsoft Academic Search

    Alan B. Binder

    1986-01-01

    The compositional similarities between the Earth's mantle and the bulk Moon make the fission model a candidate for the origin of the Moon. The author reviews the major arguments for and against the binary fission model and outlines questions that need to be answered in order to determine if the Moon could or could not have formed in this way.

  12. Get Close to a Nuclear Fission Reaction!

    NSDL National Science Digital Library

    2004-01-29

    This animation-enhanced essay from the FRONTLINE Web site details what happens inside a nuclear reactor core. Learn how engineers and technicians have designed nuclear facilities to control fission activity, regulate the tremendous heat released during fission, contain radiation, and process electricity.

  13. Quaternary Ammonium Biocides: Efficacy in Application

    PubMed Central

    2014-01-01

    Quaternary ammonium compounds (QACs) are among the most commonly used disinfectants. There has been concern that their widespread use will lead to the development of resistant organisms, and it has been suggested that limits should be place on their use. While increases in tolerance to QACs have been observed, there is no clear evidence to support the development of resistance to QACs. Since efflux pumps are believe to account for at least some of the increased tolerance found in bacteria, there has been concern that this will enhance the resistance of bacteria to certain antibiotics. QACs are membrane-active agents interacting with the cytoplasmic membrane of bacteria and lipids of viruses. The wide variety of chemical structures possible has seen an evolution in their effectiveness and expansion of applications over the last century, including non-lipid-containing viruses (i.e., noroviruses). Selection of formulations and methods of application have been shown to affect the efficacy of QACs. While numerous laboratory studies on the efficacy of QACs are available, relatively few studies have been conducted to assess their efficacy in practice. Better standardized tests for assessing and defining the differences between increases in tolerance versus resistance are needed. The ecological dynamics of microbial communities where QACs are a main line of defense against exposure to pathogens need to be better understood in terms of sublethal doses and antibiotic resistance. PMID:25362069

  14. Theoretical Description of the Fission Process

    SciTech Connect

    Witold Nazarewicz

    2009-10-25

    Advanced theoretical methods and high-performance computers may finally unlock the secrets of nuclear fission, a fundamental nuclear decay that is of great relevance to society. In this work, we studied the phenomenon of spontaneous fission using the symmetry-unrestricted nuclear density functional theory (DFT). Our results show that many observed properties of fissioning nuclei can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. From the calculated collective potential and collective mass, we estimated spontaneous fission half-lives, and good agreement with experimental data was found. We also predicted a new phenomenon of trimodal spontaneous fission for some transfermium isotopes. Our calculations demonstrate that fission barriers of excited superheavy nuclei vary rapidly with particle number, pointing to the importance of shell effects even at large excitation energies. The results are consistent with recent experiments where superheavy elements were created by bombarding an actinide target with 48-calcium; yet even at high excitation energies, sizable fission barriers remained. Not only does this reveal clues about the conditions for creating new elements, it also provides a wider context for understanding other types of fission. Understanding of the fission process is crucial for many areas of science and technology. Fission governs existence of many transuranium elements, including the predicted long-lived superheavy species. In nuclear astrophysics, fission influences the formation of heavy elements on the final stages of the r-process in a very high neutron density environment. Fission applications are numerous. Improved understanding of the fission process will enable scientists to enhance the safety and reliability of the nation’s nuclear stockpile and nuclear reactors. The deployment of a fleet of safe and efficient advanced reactors, which will also minimize radiotoxic waste and be proliferation-resistant, is a goal for the advanced nuclear fuel cycles program. While in the past the design, construction, and operation of reactors were supported through empirical trials, this new phase in nuclear energy production is expected to heavily rely on advanced modeling and simulation capabilities.

  15. Spectroscopy of selected fission fragments

    SciTech Connect

    Hoellinger, F.; Schulz, N.; Gall, B. J. P.; Bentaleb, M.; Courtin, S.; Lubkiewicz, E.; Durell, J. L.; Jones, M. A.; Leddy, M.; Phillips, W. R.; Smith, A. G.; Urban, W.; Varley, B. J.; Deloncle, I.; Porquet, M.-G.; Wilson, A.; Ahmad, I.; Morss, L. R.; Kutsarova, T.; Minkova, A.; Duprat, J.; Sergolle, H.; Gautherin, C.; Lucas, R.

    1999-10-22

    The spectroscopy of nuclei produced as fragments in the fission process has been undertaken using the EUROGAM II {gamma}-ray multidetector array. The first experiment involved a spontaneously fissioning {sup 248}Cm source and produced neutron-rich nuclei. The data analysis concentrated on the odd-A Ce isotopes and the present contribution details the structure of {sup 151}Ce which results from the strong coupling of the odd neutron to the core. The results of a preliminary analysis of the yrast structure of {sup 138}Te will also be given. In a second experiment performed at the VIVITRON accelerator in Strasbourg, nuclei on the neutron-rich side of the valley of stability were produced via the {sup 28}Si + {sup 176}Yb reaction at 145 MeV bombarding energy. The level schemes of {sup 99}Mo, {sup 101}Tc and {sup 103}Ru have been extended to high spins ({approximately} 20h). Two new high lying structures in {sup 101}Tc are explained with the help of cranked shell model calculations.

  16. Adsorption and excess fission xenon

    NASA Astrophysics Data System (ADS)

    Podosek, F. A.; Bernatowicz, T. J.; Kramer, F. E.

    The adsorption of Xe and Kr on lunar soil 10084 was measured by a method that employs only very low fractions of monolayer coverage. Results are presented as parameters for calculation of the Henry constant for adsorption as a function of temperature. The adsorption potentials are about 3 kcal/mole for Kr and 5 kcal/mole for Xe; heating the sample in vacuum increased the Xe potential to nearly 7 kcal/mole. Henry constants at the characteristic lunar temperature are about 0.3 cu cm STP/g-atm. These data were applied to consider whether adsorption is important in producing the excess fission Xe effect characteristic of highland breccias. Sorption equilibrium with a transient lunar atmosphere vented fission Xe produces concentrations seven orders of magnitude lower than observed concentrations. Higher concentrations result because of the resistance of the regolith to upward diffusion of Xe. A diffusion coefficient of 0.26 sq cm/sec is estimated for this process.

  17. Systematics of Fission-Product Yields

    SciTech Connect

    A.C. Wahl

    2002-05-01

    Empirical equations representing systematics of fission-product yields have been derived from experimental data. The systematics give some insight into nuclear-structure effects on yields, and the equations allow estimation of yields from fission of any nuclide with atomic number Z{sub F} = 90 thru 98, mass number A{sub F} = 230 thru 252, and precursor excitation energy (projectile kinetic plus binding energies) PE = 0 thru {approx}200 MeV--the ranges of these quantities for the fissioning nuclei investigated. Calculations can be made with the computer program CYFP. Estimates of uncertainties in the yield estimates are given by equations, also in CYFP, and range from {approx} 15% for the highest yield values to several orders of magnitude for very small yield values. A summation method is used to calculate weighted average parameter values for fast-neutron ({approx} fission spectrum) induced fission reactions.

  18. Theory of neutron emission in fission

    SciTech Connect

    Madland, D.G.

    1988-01-01

    Neutron emission in fission is usually described in terms of two observables: the energy spectrum of emitted neutrons N(E) and the average number of neutrons emitted per fission, or average neutron multiplicity, /bar v/p. These observables are measured before the residual fission fragments decay toward the valley of ..beta.. stability and are therefore referred to as the prompt neutron spectrum N(E) and the average prompt neutron multiplicity /bar v/p. They are of fundamental importance to the design of macroscopic systems that are driven by the fission reaction, such as thermal or fast reactors. It is the purpose of this paper to describe existing theoretical models for these two observables. Other observables for neutron emission in fission will not be described here due to space limitations. 12 refs., 2 figs.

  19. Theory of neutron emission in fission

    SciTech Connect

    Madland, D.G.

    1989-01-01

    Following a summary of the observables in neutron emission in fission, a brief history is given of theoretical representations of the prompt fission neutron spectrum N(E) and average prompt neutron multiplicity /bar /nu///sub p/. This is followed by descriptions, together with examples, of modern approaches to the calculation of these quantities including recent advancements. Emphasis will be placed upon the predictability and accuracy of the modern approaches. In particular, the dependence of N(E) and /bar /nu///sub p/ on the fissioning nucleus and its excitation energy will be discussed, as will the effects of and competition between first-, second- and third-chance fission in circumstances of high excitation energy. Finally, properties of neutron-rich (fission-fragment) nuclei are discussed that must be better known to calculate N(E) and /bar /nu///sub p/ with higher accuracy than is currently possible. 17 refs., 11 figs.

  20. Mechanisms of Mitochondrial Fission and Fusion

    PubMed Central

    van der Bliek, Alexander M.; Shen, Qinfang; Kawajiri, Sumihiro

    2013-01-01

    Mitochondria continually change shape through the combined actions of fission, fusion, and movement along cytoskeletal tracks. The lengths of mitochondria and the degree to which they form closed networks are determined by the balance between fission and fusion rates. These rates are influenced by metabolic and pathogenic conditions inside mitochondria and by their cellular environment. Fission and fusion are important for growth, for mitochondrial redistribution, and for maintenance of a healthy mitochondrial network. In addition, mitochondrial fission and fusion play prominent roles in disease-related processes such as apoptosis and mitophagy. Three members of the Dynamin family are key components of the fission and fusion machineries. Their functions are controlled by different sets of adaptor proteins on the surface of mitochondria and by a range of regulatory processes. Here, we review what is known about these proteins and the processes that regulate their actions. PMID:23732471

  1. Event-by-Event Fission with FREYA

    SciTech Connect

    Randrup, J; Vogt, R

    2010-11-09

    The recently developed code FREYA (Fission Reaction Event Yield Algorithm) generates large samples of complete fission events, consisting of two receding product nuclei as well as a number of neutrons and photons, all with complete kinematic information. Thus it is possible to calculate arbitrary correlation observables whose behavior may provide unique insight into the fission process. The presentation first discusses the present status of FREYA, which has now been extended up to energies where pre-equilibrium emission becomes significant and one or more neutrons may be emitted prior to fission. Concentrating on {sup 239}Pu(n,f), we discuss the neutron multiplicity correlations, the dependence of the neutron energy spectrum on the neutron multiplicity, and the relationship between the fragment kinetic energy and the number of neutrons and their energies. We also briefly suggest novel fission observables that could be measured with modern detectors.

  2. Superfluid dynamics of 258Fm fission

    E-print Network

    Guillaume Scamps; Cédric Simenel; Denis Lacroix

    2015-01-15

    Theoretical description of nuclear fission remains one of the major challenges of quantum many-body dynamics. The slow, mostly adiabatic motion through the fission barrier is followed by a fast, non-adiabatic descent of the potential between the fragments. The latter stage is essentially unexplored. However, it is crucial as it generates most of the excitation energy in the fragments. The superfluid dynamics in the latter stage of fission is obtained with the time-dependent Hartree-Fock theory including BCS dynamical pairing correlations. The fission modes of the 258Fm nucleus are studied. The resulting fission fragment characteristics show a good agreement with experimental data. Quantum shell effects are shown to play a crucial role in the dynamics and formation of the fragments. The importance of quantum fluctuations beyond the independent particle/quasi-particle picture is underlined and qualitatively studied.

  3. Fifty years with nuclear fission. Volume 1

    SciTech Connect

    Behrens, J.W.; Carlson, A.D. [eds.] [National Institute of Standards and Technology, Gaithersburg, MD (United States)

    1989-12-31

    The news of the discovery of nuclear fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fifieth anniversary of its discovery by holding a topical meeting entitled, ``Fifty Years with Nuclear Fission,`` in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent development in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicated a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two fully days of sessions (April 27 and 28) at the main site of the NIST in Gaithersburg, Maryland. The wide range of topics covered in this Volume 1 by this topical meeting included plenary invited, and contributed sessions entitled: Preclude to the First Chain Reaction -- 1932 to 1942; Early Fission Research -- Nuclear Structure and Spontaneous Fission; 50 Years of Fission, Science, and Technology; Nuclear Reactors, Secure Energy for the Future; Reactors 1; Fission Science 1; Safeguards and Space Applications; Fission Data; Nuclear Fission -- Its Various Aspects; Theory and Experiments in Support of Theory; Reactors and Safeguards; and General Research, Instrumentation, and By-Product. The individual papers have been cataloged separately.

  4. Construction of bispirooxindoles containing three quaternary stereocentres in a cascade using a

    E-print Network

    Barbas III, Carlos F.

    Construction of bispirooxindoles containing three quaternary stereocentres in a cascade using-step constructions of molecules with multiple quaternary carbon stereocentres are rare. The spirooxindole structural by a novel multifunctional organocatalyst that contains tertiary and primary amines and thiourea moieties

  5. Prompt fission neutron spectra of n+235U above the (n,nf) fission threshold

    NASA Astrophysics Data System (ADS)

    Shu, Neng-Chuan; Jia, Min; Chen, Yong-Jing; Liu, Ting-Jin

    2015-05-01

    Calculations of prompt fission neutron spectra (PFNS) from the 235U(n, f) reaction were performed with a semi-empirical method for En = 7.0 and 14.7 MeV neutron energies. The total PFNS were obtained as a superposition of (n,xnf) pre-fission neutron spectra and post-fission spectra of neutrons which were evaporated from fission fragments, and these two kinds of spectra were taken as an expression of the evaporation spectrum. The contributions of (n,xnf) fission neutron spectra on the calculated PFNS were discussed. The results show that emission of one or two neutrons in the (n,nf) or (n,2nf) reactions influences the PFNS shape, and the neutron spectra of the (n,xnf) fission-channel are soft compared with the neutron spectra of the (n,f) fission channel. In addition, analysis of the multiple-chance fission component showed that second-chance fission dominates the PFNS with an incident neutron energy of 14.7 MeV whereas first-chance fission dominates the 7 MeV case. Supported by National Natural Science Foundation of China (11205246, 91126010, U1230127, 91226102), IAEA CRP (15905), and Defense Industrial Technology Development Program (B0120110034)

  6. Quaternary Evolution of Karliova Triple Junction

    NASA Astrophysics Data System (ADS)

    Sançar, Taylan; Zabc?, Cengiz; Akyüz, H. Serdar

    2013-04-01

    The arguments to explain Quaternary evolution of Karl?ova Triple Junction (KTJ) depends upon two different analogue models. The compressional type of Prandtl Cell Model (PCM) and 60 km wide shear zone with concomitant counter clockwise block rotation used to modelled for west and east of the KTJ respectively. The data for the model of west of the KTJ acquired by extensive field studies, and quantified geomorphic features. Compressional PCM put forward that behavior of slip lines controlled by boundary faults. But the model is not enough to explain slip distribution, age relation of them. At west of the KTJ boundary faults presented by eastern most segments of the North Anatolian Fault Zone (NAFZ) and the East Anatolian Fault Zone (EAFZ). Slip lines, however, presented by Bahçeli and Toklular faults. Both field studies and morphometric analyses undisputedly set forth that there are two different fault types between the NAFZ and EAFZ. The most strain loaded fault type, which are positioned near the NAFZ, start as a strike-slip fault and when it turn to SE its sense of motion change to oblique normal due to changing orientation of principal stress axes. The new orientation of stress axes exposed in the field as a special kind of caprock -cuesta-. The younger slip lines formed very close to junction point and accommodate less slip. Even though slip trajectories started from the boundary faults in compressional PCM, at the west of KTJ, right lateral trajectories more clearly formed close the NAFZ and left lateral trajectories, relatively less strain loaded fault type, are poorly formed close the EAFZ . We think that, this differences between KTJ and compressional PCM result from the distinction of velocity of boundary faults. East of the KTJ governed by completely different mechanism. The region controlled two main fault systems. The Varto Fault Zone (VFZ), the eastern branch of the KTJ, and Murat Fault (MF) delimited the region from north and south respectively. The region also delimited at west by the EAFZ. All secondary faults between these three faults are strike slip faults. The faults which are positioned NW-SE and nearly parallel to the N70W oriented VFZ are dextral, whereas sinistral faults are N-S oriented and nearly orthogonal to NW-SE trending right lateral faults. Sinistral faults develop in the overlap area between adjacent left stepping of dextral faults which are arranged in an en echelon pattern. This configuration formed under shear zone regime with one Previous shear zone model studies proposed that right lateral faults form the 17-24 degree to principal displacement zone. Paleo-magnetic studies of Plio-Quaternary rocks, which covered the all region, show that there is a counterclockwise block rotation between 18 to 23 degree that is clearly explain position of the secondary right lateral faults.

  7. Analysis of Quaternary Amine Compounds by Hydrophilic Interaction Chromatography\\/Mass Spectrometry (HILIC\\/MS)

    Microsoft Academic Search

    Yong Guo

    2005-01-01

    Hydrophilic interaction chromatography (HILIC) was explored for the separation of selected quaternary amine compounds of biological and environmental importance, including acetylcholine, choline, betaine, chlormequat, and mepiquat. The HILIC method was successful in separating the model quaternary amine compounds without the need for ion?pairing reagents. The present study indicates that the amide phase provides much stronger retention for the quaternary amine

  8. Late Quaternary fire regimes of Australasia

    NASA Astrophysics Data System (ADS)

    Mooney, S. D.; Harrison, S. P.; Bartlein, P. J.; Daniau, A.-L.; Stevenson, J.; Brownlie, K. C.; Buckman, S.; Cupper, M.; Luly, J.; Black, M.; Colhoun, E.; D'Costa, D.; Dodson, J.; Haberle, S.; Hope, G. S.; Kershaw, P.; Kenyon, C.; McKenzie, M.; Williams, N.

    2011-01-01

    We have compiled 223 sedimentary charcoal records from Australasia in order to examine the temporal and spatial variability of fire regimes during the Late Quaternary. While some of these records cover more than a full glacial cycle, here we focus on the last 70,000 years when the number of individual records in the compilation allows more robust conclusions. On orbital time scales, fire in Australasia predominantly reflects climate, with colder periods characterized by less and warmer intervals by more biomass burning. The composite record for the region also shows considerable millennial-scale variability during the last glacial interval (73.5-14.7 ka). Within the limits of the dating uncertainties of individual records, the variability shown by the composite charcoal record is more similar to the form, number and timing of Dansgaard-Oeschger cycles as observed in Greenland ice cores than to the variability expressed in the Antarctic ice-core record. The composite charcoal record suggests increased biomass burning in the Australasian region during Greenland Interstadials and reduced burning during Greenland Stadials. Millennial-scale variability is characteristic of the composite record of the sub-tropical high pressure belt during the past 21 ka, but the tropics show a somewhat simpler pattern of variability with major peaks in biomass burning around 15 ka and 8 ka. There is no distinct change in fire regime corresponding to the arrival of humans in Australia at 50 ± 10 ka and no correlation between archaeological evidence of increased human activity during the past 40 ka and the history of biomass burning. However, changes in biomass burning in the last 200 years may have been exacerbated or influenced by humans.

  9. Tertiary and Quaternary Research with Remote Sensing Methods

    NASA Technical Reports Server (NTRS)

    Conel, J. E.

    1985-01-01

    Problems encountered in mapping the Quaternary section of the Wind River Region using remote sensing methods are discussed. Analysis of the stratigraphic section is a fundamental aspect of the geologic study of sedimentary basins. Stratigraphic analysis of post-Cretaceous rocks in the Wind River Basin encounters problems of a distinctly different character from those involved in studying the pre-Cretaceous section. The interior of the basin is predominantly covered by Tertiary and Quaternary sediments. These rocks, except on the basin margin to the north, are mostly flat lying or gently dipping. The Tertiary section consists of sandstones, siltstones, and tuffaceous sediments, some variegated, but in general poorly bedded and of great lithologic similarity. The Quaternary sediments consist of terrace, fan, and debris tongue deposits, unconsolidated alluvium occupying the bottoms of modern watercourses, deposits of eolian origin and tufa. Terrace and fan deposits are compositionally diverse and reflect the lithologic diversity of the source terranes.

  10. The tempo of avian diversification during the Quaternary.

    PubMed Central

    Zink, Robert M; Klicka, John; Barber, Brian R

    2004-01-01

    It is generally assumed that the Quaternary was a period of heightened diversification in temperate vertebrate organisms. Previous molecular systematics studies have challenged this assertion. We re-examined this issue in north temperate birds using log-lineage plots and distributions of sister-taxon distances. Log-lineage plots support earlier conclusions that avian diversification slowed during the Quaternary. To test plots of empirical sister-taxon distances we simulated three sets of phylogenies: constant speciation and extinction, a pulse of recent speciation, and a pulse of recent extinction. Previous opinions favour the model of recent speciation although our empirical dataset on 74 avian comparisons failed to reject a distribution derived from the constant and extinction models. Hence, it does not appear that the Quaternary was a period of exceptional rates of diversification, relative to the background rate. PMID:15101578

  11. Quaternary naltrexone reverses radiogenic and morphine-induced locomotor hyperactivity

    SciTech Connect

    Mickley, G.A.; Stevens, K.E.; Galbraith, J.A.; White, G.A.; Gibbs, G.L.

    1984-04-01

    The present study attempted to determine the relative role of the peripheral and central nervous system in the production of morphine-induced or radiation-induced locomotor hyperactivity of the mouse. Toward this end, we used a quaternary derivative of an opiate antagonist (naltrexone methobromide), which presumably does not cross the blood-brain barrier. Quaternary naltrexone was used to challenge the stereotypic locomotor response observed in these mice after either an i.p. injection of morphine or exposure to 1500 rads /sup 60/Co. The quaternary derivative of naltrexone reversed the locomotor hyperactivity normally observed in the C57BL/6J mouse after an injection of morphine. It also significantly attenuated radiation-induced locomotion. The data reported here support the hypothesis of endorphin involvement in radiation-induced and radiogenic behaviors. However, these conclusions are contingent upon further research which more fully evaluates naltrexone methobromide's capacity to cross the blood-brain barrier.

  12. Fifty years with nuclear fission. Volume 2

    SciTech Connect

    Behrens, J.W.; Carlson, A.D. [eds.] [National Institute of Standards and Technology, Gaithersburg, MD (United States)

    1989-12-31

    The news of the discovery of nucler fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fiftieth anniversary of its discovery by holding a topical meeting entitled, ``Fifty years with nuclear fission,`` in the United States during the year 1989. The objective of the meeting was to bring together pioneers of the nuclear industry and other scientists and engineers to report on reminiscences of the past and on the more recent developments in fission science and technology. The conference highlighted the early pioneers of the nuclear industry by dedicating a full day (April 26), consisting of two plenary sessions, at the National Academy of Sciences (NAS) in Washington, DC. More recent developments in fission science and technology in addition to historical reflections were topics for two full days of sessions (April 27 and 28) at the main sites of the NIST in Gaithersburg, Maryland. The wide range of topics covered by Volume 2 of this topical meeting included plenary invited, and contributed sessions entitled, Nuclear fission -- a prospective; reactors II; fission science II; medical and industrial applications by by-products; reactors and safeguards; general research, instrumentation, and by-products; and fission data, astrophysics, and space applications. The individual papers have been cataloged separately.

  13. Recent Advances in Singlet Fission

    NASA Astrophysics Data System (ADS)

    Smith, Millicent B.; Michl, Josef

    2013-04-01

    A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited molecule shares its energy with a ground-state neighbor to produce two triplet excited molecules. It has been observed to occur in single-crystal, polycrystalline, and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivatives, and it is argued that a wider structural variety would be desirable. The current state of the development of molecular structure design rules, based on first-principles theoretical considerations, is described along with initial examples of implementation.

  14. Recent advances in singlet fission.

    PubMed

    Smith, Millicent B; Michl, Josef

    2013-01-01

    A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited molecule shares its energy with a ground-state neighbor to produce two triplet excited molecules. It has been observed to occur in single-crystal, polycrystalline, and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivatives, and it is argued that a wider structural variety would be desirable. The current state of the development of molecular structure design rules, based on first-principles theoretical considerations, is described along with initial examples of implementation. PMID:23298243

  15. Phase 1 space fission propulsion system design considerations

    Microsoft Academic Search

    Mike Houts; Melissa van Dyke; Tom Godfroy; Kevin Pedersen; James Martin; Ricky Dickens; Pat Salvail; Ivana Hrbud; Robert Carter

    2002-01-01

    Fission technology can enable rapid, affordable access to any point in the solar system. If fission propulsion systems are to be developed to their full potential; however, near-term customers must be identified and initial fission systems successfully developed, launched, and operated. Studies conducted in fiscal year 2001 (IISTP, 2001) show that fission electric propulsion (FEP) systems operating at 80 kWe

  16. Phase 1 Space Fission Propulsion Energy Source Design

    Microsoft Academic Search

    Mike Houts; Melissa Van Dyke; Tom Godfroy; Kevin Pedersen; James Martin; Ricky Dickens; Pat Salvail; Ivana Hrbud; Robert Carter

    2002-01-01

    Fission technology can enable rapid, affordable access to any point in the solar system. If fission propulsion systems are to be developed to their full potential; however, near-term customers must be identified and initial fission systems successfully developed, launched, and operated. Studies conducted in fiscal year 2001 (IISTP, 2001) show that fission electric propulsion (FEP) systems with a specific mass

  17. Nuclear Thermal Rockets: The Physics of the Fission Reactor

    E-print Network

    Ross, Shane

    Nuclear Thermal Rockets: The Physics of the Fission Reactor Shane D. Ross Control and Dynamical heats up when it passes through a nuclear reactor, where controlled fission of some fissionable material, with the nuclear fission reactor as a heat source [Lawrence, Witter, and Humble, 1992]. it works essentially

  18. Singlet fission in reduced dimensions of crystals

    NASA Astrophysics Data System (ADS)

    Teichen, Paul; Eaves, Joel

    2014-03-01

    In some molecular systems the decay of an initially excited singlet into two independent triplets, a process called singlet fission, is highly efficient. Organic crystals are among the most promising candidates for increasing yields in next-generation photovoltaics. Although excitons are known to exist in reduced dimensions of crystals the role of dimensionality in the entanglement of two triplets born out of singlet fission remains unclear. We develop a quantum lattice model for singlet fission to examine the role of quantum entanglement and exciton delocalization.

  19. Ice Age Earth: Late Quaternary geology and climate

    SciTech Connect

    Dawson, A.G.

    1992-01-01

    This book is a concise and readable account of the most important geologic records of the late Quaternary. It provides a synopsis of the major environmental changes that took place from approximately 13,000 to 7,000 years ago, highlighting the complexity and rapidity of past climate changes and the environmental responses they produced. The text is well illustrated, though some figures are rough and need more explanation. Also needed is a critical appraisal of the geochronology which places the paleoenvironmental records into the temporal domain. However, as a whole the book reaches its objective of summarizing the most important scientific findings about the nature of the late Quaternary climate changes.

  20. Isomeric-to-prompt fission ratios for the uranium fission isomers 236Um and 238Um

    NASA Astrophysics Data System (ADS)

    Tischler, R.; Kleinrahm, A.; Kroth, R.; Günther, C.

    1980-07-01

    Fission isomers in 236U and 238U have been populated in 235U(d, p)236Um, 236U(d, pn)236Um, and the 238U(d, pn)238Um reactions. Time spectra of fission fragments with respect to the cyclotron beam pulses have been measured. From these measurements the isomeric-to-prompt fission ratios are derived for deuteron energies ranging from 17 to 25 MeV. The isomeric-to-prompt ratios show a distinct maximum around 20 MeV for the (d, pn) reactions, whereas a monotonic decrease is observed for the 235U(d, p)236Um reaction. NUCLEAR REACTIONS, FISSION 235U(d, pf) and 236,238U(d, pnf), measured delayed fission fragment time spectra, deduced isomeric-to-prompt fission ratios.

  1. Fission Matrix Capability for MCNP Monte Carlo

    SciTech Connect

    Carney, Sean E. [Los Alamos National Laboratory; Brown, Forrest B. [Los Alamos National Laboratory; Kiedrowski, Brian C. [Los Alamos National Laboratory; Martin, William R. [Los Alamos National Laboratory

    2012-09-05

    In a Monte Carlo criticality calculation, before the tallying of quantities can begin, a converged fission source (the fundamental eigenvector of the fission kernel) is required. Tallies of interest may include powers, absorption rates, leakage rates, or the multiplication factor (the fundamental eigenvalue of the fission kernel, k{sub eff}). Just as in the power iteration method of linear algebra, if the dominance ratio (the ratio of the first and zeroth eigenvalues) is high, many iterations of neutron history simulations are required to isolate the fundamental mode of the problem. Optically large systems have large dominance ratios, and systems containing poor neutron communication between regions are also slow to converge. The fission matrix method, implemented into MCNP[1], addresses these problems. When Monte Carlo random walk from a source is executed, the fission kernel is stochastically applied to the source. Random numbers are used for: distances to collision, reaction types, scattering physics, fission reactions, etc. This method is used because the fission kernel is a complex, 7-dimensional operator that is not explicitly known. Deterministic methods use approximations/discretization in energy, space, and direction to the kernel. Consequently, they are faster. Monte Carlo directly simulates the physics, which necessitates the use of random sampling. Because of this statistical noise, common convergence acceleration methods used in deterministic methods do not work. In the fission matrix method, we are using the random walk information not only to build the next-iteration fission source, but also a spatially-averaged fission kernel. Just like in deterministic methods, this involves approximation and discretization. The approximation is the tallying of the spatially-discretized fission kernel with an incorrect fission source. We address this by making the spatial mesh fine enough that this error is negligible. As a consequence of discretization we get a spatially low-order kernel, the fundamental eigenvector of which should converge faster than that of continuous kernel. We can then redistribute the fission bank to match the fundamental fission matrix eigenvector, effectively eliminating all higher modes. For all computations here biasing is not used, with the intention of comparing the unaltered, conventional Monte Carlo process with the fission matrix results. The source convergence of standard Monte Carlo criticality calculations are, to some extent, always subject to the characteristics of the problem. This method seeks to partially eliminate this problem-dependence by directly calculating the spatial coupling. The primary cost of this, which has prevented widespread use since its inception [2,3,4], is the extra storage required. To account for the coupling of all N spatial regions to every other region requires storing N{sup 2} values. For realistic problems, where a fine resolution is required for the suppression of discretization error, the storage becomes inordinate. Two factors lead to a renewed interest here: the larger memory available on modern computers and the development of a better storage scheme based on physical intuition. When the distance between source and fission events is short compared with the size of the entire system, saving memory by accounting for only local coupling introduces little extra error. We can gain other information from directly tallying the fission kernel: higher eigenmodes and eigenvalues. Conventional Monte Carlo cannot calculate this data - here we have a way to get new information for multiplying systems. In Ref. [5], higher mode eigenfunctions are analyzed for a three-region 1-dimensional problem and 2-dimensional homogenous problem. We analyze higher modes for more realistic problems. There is also the question of practical use of this information; here we examine a way of using eigenmode information to address the negative confidence interval bias due to inter-cycle correlation. We apply this method mainly to four problems: 2D pressurized water reactor (PWR) [6],

  2. Fission product induced swelling of U-Mo alloy fuel

    NASA Astrophysics Data System (ADS)

    Kim, Yeon Soo; Hofman, G. L.

    2011-12-01

    Fuel swelling of U-Mo alloy was modeled using the measured data from samples irradiated up to a fission density of ˜7 × 10 27 fissions/m 3 at temperatures below ˜250 °C. The overall fuel swelling was measured from U-Mo foils with as-fabricated thickness of 250 ?m. Volume fractions occupied by fission gas bubbles were measured and fuel swelling caused by the fission gas bubbles was quantified. The portion of fuel swelling by solid fission products including solid and liquid fission products as well as fission gas atoms not enclosed in the fission gas bubbles is estimated by subtracting the portion of fuel swelling by gas bubbles from the overall fuel swelling. Empirical correlations for overall fuel swelling, swelling by gas bubbles, and swelling by solid fission products were obtained in terms of fission density.

  3. Fragment Energy Correlation Measurements for 252Cf Spontaneous Fission and 235U Thermal-Neutron Fission

    Microsoft Academic Search

    H. W. Schmitt; J. H. Neiler; F. J. Walter

    1966-01-01

    Fission-fragment mass and energy distributions and mass-versus-energy correlations have been obtained for 252Cf spontaneous fission and 235U thermal-neutron-induced fission. Silicon surface-barrier detectors were used in energy correlation measurements; absolute fragment energies were obtained by means of the mass-dependent energy calibration developed recently at this laboratory. Average total fragment kinetic energies before neutron emission are found to be 186.5+\\/-1.2 MeV for

  4. Microscopic description of complex nuclear decay: Multimodal fission

    NASA Astrophysics Data System (ADS)

    Staszczak, A.; Baran, A.; Dobaczewski, J.; Nazarewicz, W.

    2009-07-01

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  5. Microscopic description of complex nuclear decay: multimodal fission

    E-print Network

    Staszczak, A; Dobaczewski, J; Nazarewicz, W

    2009-01-01

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  6. Microscopic description of complex nuclear decay: multimodal fission

    E-print Network

    A. Staszczak; A. Baran; J. Dobaczewski; W. Nazarewicz

    2009-06-23

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  7. Microscopic description of complex nuclear decay: Multimodal fission

    SciTech Connect

    Staszczak, A.; Baran, A. [Institute of Physics, Maria Curie-Sklodowska University, pl. M. Curie-Sklodowskiej 1, PL-20-031 Lublin (Poland); Department of Physics and Astronomy, University of Tennessee Knoxville, Tennessee 37996 (United States); Physics Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831 (United States); Dobaczewski, J. [Institute of Theoretical Physics, University of Warsaw, ul. Hoza 69, PL-00-681 Warsaw (Poland); Department of Physics, P. O. Box 35 (YFL), FI-40014 University of Jyvaeskylae (Finland); Nazarewicz, W. [Department of Physics and Astronomy, University of Tennessee Knoxville, Tennessee 37996 (United States); Physics Division, Oak Ridge National Laboratory, P. O. Box 2008, Oak Ridge, Tennessee 37831 (United States); Institute of Theoretical Physics, University of Warsaw, ul. Hoza 69, PL-00-681 Warsaw (Poland)

    2009-07-15

    Our understanding of nuclear fission, a fundamental nuclear decay, is still incomplete due to the complexity of the process. In this paper, we describe a study of spontaneous fission using the symmetry-unrestricted nuclear density functional theory. Our results show that the observed bimodal fission can be explained in terms of pathways in multidimensional collective space corresponding to different geometries of fission products. We also predict a new phenomenon of trimodal spontaneous fission for some rutherfordium, seaborgium, and hassium isotopes.

  8. Receiver architectures and aperiodic correlation parameters for direct-sequence spread spectrum with quaternary complex spreading sequences

    Microsoft Academic Search

    Thomas G. Macdonald; Michael B. Pursley

    1998-01-01

    Results on quaternary complex sequences have provided quaternary sequences that have better periodic correlation properties than binary sequences. In this paper we examine a receiver architecture that takes advantage of the superior periodic correlation properties of these quaternary sequences, and we investigate the aperiodic correlation properties that permit quaternary direct-sequence spread spectrum to discriminate against multipath and provide multiple-access capability

  9. I-NERI ANNUAL TECHNICAL PROGRESS REPORT: 2006-002-K, Separation of Fission Products from Molten LiCl-KCl Salt Used for Electrorefining of Metal Fuels

    SciTech Connect

    S. Frank

    2009-09-01

    An attractive alternative to the once-through disposal of electrorefiner salt is to selectively remove the active fission products from the salt and recycle the salt back to the electrorefiner (ER). This would allow salt reuse for some number of cycles before ultimate disposal of the salt in a ceramic waste form. Reuse of ER salt would, thus, greatly reduce the volume of ceramic waste produced during the pyroprocessing of spent nuclear fuel. This final portion of the joint I-NERI research project is to demonstrate the separation of fission products from molten ER salt by two methods previously selected during phase two (FY-08) of this project. The two methods selected were salt/zeolite contacting and rare-earth fission product precipitation by oxygen bubbling. The ER salt used in these tests came from the Mark-IV electrorefiner used to anodically dissolved driver fuel from the EBR-II reactor on the INL site. The tests were performed using the Hot Fuel Dissolution Apparatus (HFDA) located in the main cell of the Hot Fuels Examination Facility (HFEF) at the Materials and Fuels complex on the INL site. Results from these tests were evaluated during a joint meeting of KAERI and INL investigators to provide recommendations as to the future direction of fission product removal from electrorefiner salt that accumulate during spent fuel treatment. Additionally, work continued on kinetic measurements of surrogate quaternary salt systems to provide fundamental kinetics on the ion exchange system and to expand the equilibrium model system developed during the first two phases of this project. The specific objectives of the FY09 I-NERI research activities at the INL include the following: • Perform demonstration tests of the selected KAERI precipitation and INL salt/zeolite contacting processes for fission product removal using radioactive, fission product loaded ER salt • Continue kinetic studies of the quaternary Cs/Sr-LiCl-KCl system to determine the rate of ion exchange during the salt/zeolite contacting process • Compare the adsorption models to experimentally obtained, ER salt results • Evaluate results obtained from the oxygen precipitation and salt/zeolite ion exchange studies to determine the best processes for selective fission-product removal from electrorefiner salt.

  10. Charge Transfer-Mediated Singlet Fission

    NASA Astrophysics Data System (ADS)

    Monahan, N.; Zhu, X.-Y.

    2015-04-01

    Singlet fission, the splitting of a singlet exciton into two triplet excitons in molecular materials, is interesting not only as a model many-electron problem, but also as a process with potential applications in solar energy conversion. Here we discuss limitations of the conventional four-electron and molecular dimer model in describing singlet fission in crystalline organic semiconductors, such as pentacene and tetracene. We emphasize the need to consider electronic delocalization, which is responsible for the decisive role played by the Mott-Wannier exciton, also called the charge transfer (CT) exciton, in mediating singlet fission. At the strong electronic coupling limit, the initial excitation creates a quantum superposition of singlet, CT, and triplet-pair states, and we present experimental evidence for this interpretation. We also discuss the most recent attempts at translating this mechanistic understanding into design principles for CT state-mediated intramolecular singlet fission in oligomers and polymers.

  11. Reactor power history from fission product signatures 

    E-print Network

    Sweeney, David J.

    2009-05-15

    The purpose of this research was to identify fission product signatures that could be used to uniquely identify a specific spent fuel assembly in order to improve international safeguards. This capability would help prevent and deter potential...

  12. Nuclear fission as resonance-mediated conductance

    E-print Network

    G. F. Bertsch

    2014-12-18

    For 75 years the theory of nuclear fission has been based on the existence of a collective coordinate associated with the nuclear shape, an assumption required by the Bohr-Wheeler formula as well as by the R-matrix theory of fission. We show that it is also possible to formulate the theory without the help of collective coordinates. In the new formulation, fission is facilitated by individual states in the barrier region rather than channels over the barrier. In a certain limit the theory reduces to a formula closely related to the formula for electronic conductance through resonant tunneling states. In contrast, conduction through channels gives rise to a staircase excitation function that is well-known in nanoscale electronics but has never been seen in nuclear fission.

  13. Advanced modeling of prompt fission neutrons

    SciTech Connect

    Talou, Patrick [Los Alamos National Laboratory

    2009-01-01

    Theoretical and numerical studies of prompt fission neutrons are presented. The main results of the Los Alamos model often used in nuclear data evaluation work are reviewed briefly, and a preliminary assessment of uncertainties associated with the evaluated prompt fission neutron spectrum for n (0.5 MeV)+{sup 239}Pu is discussed. Advanced modeling of prompt fission neutrons is done by Monte Carlo simulations of the evaporation process of the excited primary fission fragments. The successive emissions of neutrons are followed in the statistical formalism framework, and detailed information, beyond average quantities, can be inferred. This approach is applied to the following reactions: {sup 252}Cf (sf), n{sub th} + {sup 239}Pu, n (0.5 MeV)+{sup 235}U, and {sup 236}Pu (sf). A discussion on the merits and present limitations of this approach concludes this presentation.

  14. Porous fission fragment tracks in fluorapatite

    SciTech Connect

    Li Weixing; Ewing, Rodney C. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1005 (United States); Wang Lumin [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Department of Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Sun Kai [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2104 (United States); Lang, Maik [Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1005 (United States); Trautmann, Christina [GSI Helmholtz Centre for Heavy Ion Research, Planckstr. 1, 64291 Darmstadt (Germany)

    2010-10-01

    Fission tracks caused by the spontaneous fission of {sup 238}U in minerals, as revealed by chemical etching, are extensively used to determine the age and thermal history of Earth's crust. Details of the structure and annealing of tracks at the atomic scale have remained elusive, as the original track is destroyed during chemical etching. By combining transmission electron microscopy with in situ heating, we demonstrate that fission tracks in fluorapatite are actually porous tubes, instead of having an amorphous core, as generally assumed. Direct observation shows thermally induced track fragmentation in fluoapatite, in clear contrast to the amorphous tracks in zircon, which gradually ''fade'' without fragmentation. Rayleigh instability and the thermal emission of vacancies control the annealing of porous fission tracks in fluorapatite.

  15. Systematics of fission barriers in superheavy elements

    Microsoft Academic Search

    T. Burvenich; M. Bender; J. A. Maruhn; P.-G. Reinhard

    2004-01-01

    We investigate the systematics of fission barriers in superheavy elements in the range Z = 108- 120 and N = 166-182. Results from two self-consistent models for nuclear structure, the relativistic mean-field (RMF) model as well as the non-relativistic Skyrme-Hartree-Fock approach are compared and discussed. We restrict ourselves to axially symmetric shapes, which provides an upper bound on static fission

  16. Fast neutron induced fission of 238U

    Microsoft Academic Search

    S. T. Lam; L. L. Yu; H. W. Fielding; W. K. Dawson; G. C. Neilson; J. T. Sample

    1980-01-01

    Fission of 238U was induced by a pulsed beam of monoenergetic fast neutrons. A heavy-ion surface barrier detector was used for the detection of fission fragments. Fragment mass was determined from measured fragment energy and fragment flight time. Fragment-mass distribution and correlation of fragment kinetic energy with fragment mass were obtained for neutron incident energies of 2.0 to 5.2 MeV

  17. Systematics of Fission Barriers in Superheavy Elements

    E-print Network

    T. Buervenich; M. Bender; J. A. Maruhn; P. -G. Reinhard

    2004-02-03

    We investigate the systematics of fission barriers in superheavy elements in the range Z = 108-120 and N = 166-182. Results from two self-consistent models for nuclear structure, the relativistic mean-field (RMF) model as well as the non-relativistic Skyrme-Hartree-Fock approach are compared and discussed. We restrict ourselves to axially symmetric shapes, which provides an upper bound on static fission barriers. We benchmark the predictive power of the models examining the barriers and fission isomers of selected heavy actinide nuclei for which data are available. For both actinides and superheavy nuclei, the RMF model systematically predicts lower barriers than most Skyrme interactions. In particular the fission isomers are predicted too low by the RMF, which casts some doubt on recent predictions about superdeformed ground states of some superheavy nuclei. For the superheavy nuclei under investigation, fission barriers drop to small values around Z = 110, N = 180 and increase again for heavier systems. For most of the forces, there is no fission isomer for superheavy nuclei, as superdeformed states are in most cases found to be unstable with respect to octupole distortions.

  18. Spontaneous fission of the heaviest elements

    SciTech Connect

    Hoffman, D.C.

    1989-04-01

    Although spontaneous fission was discovered in /sup 238/U in 1940, detailed studies of the process were first made possible in the 1960's with the availability of milligram quantities of /sup 252/Cf. The advent of solid-state detectors made it possible to perform measurements of coincident fission fragments from even very short-lived spontaneous fission activities or those available in only very small quantities. Until 1971 it was believed that the main features of the mass and kinetic-energy distributions were essentially the same as those for thermal neutron-induced fission and that all low-energy fission proceeded via asymmetric mass division with total kinetic energies which could be derived by linear extrapolation from those of lighter elements. In 1971, measurements of /sup 257/Fm showed an increase in symmetric mass division with anomalously high TKE's. Subsequent experiments showed that in /sup 258/Fm and /sup 259/Fm, the most probable mass split was symmetric with very high total kinetic energy. Measurements for the heavier elements have shown symmetric mass distributions with both high and low total kinetic energies. Recent results for spontaneous fission properties of the heaviest elements are reviewed and compared with theory. 31 refs., 8 figs., 1 tab.

  19. Ionization Chamber for Prompt Fission Neutron Investigations

    NASA Astrophysics Data System (ADS)

    Zeynalov, Sh.; Zeynalova, O.; Hambsch, F.-J.; Sedyshev, P.; Shvetsov, V.

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy measurement. Correlated FF kinetic energies, their masses and the angle of FF in respect to the axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electronic circuitry and special multi-channel pulse processing apparatus. Mathematical formulae provided for FF angles measured in respect to the coordinate axes. It was shown how the point of fission fragments origin on the target plane may be determined using the same measured data. The last feature made the TIC a rather powerful tool for prompt fission neutron (PFN) emission investigation in event-by-event analysis of individual fission reactions from non- point fissile source. Position sensitive neutron induced fission detector for neutron-imaging applications with both thermal and low energy neutrons was found as another possible implementation of the designed TIC.

  20. Quaternary fossil fauna of South Canterbury, South Island, New Zealand

    Microsoft Academic Search

    T. H. Worthy

    1997-01-01

    This study documents the Late Quaternary fossil fauna from 59 fossil sites in the South Canterbury downlands, South Island, New Zealand. Twenty?seven sites were predator accumulations attributed to laughing owls, two were accumulated by falcons, two were swamp sites, and the rest were pitfalls or rockshelter deposits. A total of 60 indigenous species of birds, one bat, three rodents, one

  1. Quaternary research in Poland: selected achievements and prospects

    Microsoft Academic Search

    Leszek Marks

    A b s t r a c t . During the last thirty years there were several turnouts in Quaternary studies that increasingly accelerated our under- standing of natural processes and opened new research fields. Among others, they included complex reconstruction of palaeoclimatic phenomena, studies of deep-sea and long-term continental record, and extensive application of reliable dating methods. In Poland

  2. Synthesis and antimicrobial properties of polymerizable quaternary ammoniums

    Microsoft Academic Search

    Laurent Caillier; Elisabeth Taffin de Givenchy; Richard Levy; Yves Vandenberghe; Serge Géribaldi; Frédéric Guittard

    2009-01-01

    Introduction of biocide monomers during the process of polymerization is a promising approach in the development of new permanent non leaching biocide materials. Two series of surfactants monomers, with a quaternary ammonium group as polar head and an acrylic function as the polymerizable moiety, were synthesized and tested to evaluate their surface active properties alongside with their antibacterial and antifungal

  3. Study on antibacterial behavior of insoluble quaternary ammonium

    Microsoft Academic Search

    Shan Jiang; Li Wang; Haojie Yu; Ying Chen; Quan Shi

    2006-01-01

    Insoluble crosslinked polystyrenes (PS) grafted with different quaternary ammonium groups were synthesized as antibacterial agents. Their antibacterial activ- ities against Staphylococcus aureus were investigated by a colony count method. It was found that when the concen- tration of the insoluble antibacterial agent was low, the antibacterial activity was different from that of the typical soluble antibacterial agent. The antibacterial activity

  4. Antibacterial Nanocomposite with Calcium Phosphate and Quaternary Ammonium

    Microsoft Academic Search

    L. Cheng; M. D. Weir; K. Zhang; S. M. Xu; Q. Chen; X. Zhou; H. H. K. Xu

    2012-01-01

    Secondary caries is a frequent reason for restoration failure, resulting from acidogenic bacteria and their biofilms. The objectives of this study were to: (1) develop a novel nanocomposite containing nanoparticles of amorphous calcium phosphate (NACP) and quaternary ammonium dimethacrylate (QADM); and (2) investigate its mechanical and antibacterial durability. A spray-drying technique yielded NACP with particle size of 116 nm. The

  5. Historical distribution of Sundaland's Dipterocarp rainforests at Quaternary glacial maxima

    E-print Network

    Slik, Ferry

    Historical distribution of Sundaland's Dipterocarp rainforests at Quaternary glacial maxima Niels, 2014 (received for review February 21, 2014) The extent of Dipterocarp rainforests on the emergent the rainforests of Sundaland, and their distributions serve as a proxy for rainforest extent. We used species

  6. Effects of Quaternary Sea Level Cycles on Strontium in Seawater

    Microsoft Academic Search

    Heather M Stoll; Daniel P Schrag

    1998-01-01

    The effects of Quaternary sea level changes on the Sr budget of the ocean are investigated using coupled numerical models of the seawater Sr and Ca budgets. Glacial\\/interglacial sea level cycles influence the Sr concentration of seawater directly through the periodic exposure and weathering of aragonite on continental shelves and indirectly by modulating the location and extent of carbonate deposition

  7. Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information

    ERIC Educational Resources Information Center

    Oehlke, Betsy M.; Dolliver, Holly A. S.

    2011-01-01

    The majority of soils in the western Wisconsin have developed from glacial sediments deposited during the Quaternary Period (2.6 million years before present). In many regions, multiple advances and retreats have left a complex landscape of diverse glacial sediments and landforms. The soils that have developed on these deposits reflect the nature…

  8. LATE QUATERNARY GLACIATION OF THE ERCIYES VOLCANO, CENTRAL TURKEY

    E-print Network

    Zreda, Marek

    LATE QUATERNARY GLACIATION OF THE ERCIYES VOLCANO, CENTRAL TURKEY SARIKAYA, M. Akif1, ÇINER, Attila, Turkey, aciner@hun.edu.tr, (2) Hydrology and Water Resources, Univ of Arizona, Tucson, AZ 85721 Mount Erciyes (3917 m), highest stratovolcano of Central Turkey, is located in the northeastern part

  9. Hydroclimatic interpretation of Quaternary shorelines on South Australian playas

    Microsoft Academic Search

    Gerald C. Nanson; Roger A. Callen; David M. Price

    1998-01-01

    The catchment of Lake Eyre is one of the world's largest internally drained basins. The playas near its depocentre, the driest region of Australia, contain a partial record of Quaternary climatic and hydrologic events for the last full glacial cycle, and probably beyond. Ancient beach-ridges marginal to lakes Eyre, Frome, Callabonna and Blanche have been dated using thermoluminescence (TL) to

  10. Application of quaternary phase diagrams to compound semiconductor processing

    SciTech Connect

    Sinclair, R.

    1994-10-01

    Isobaric, isothermal phase diagrams are a molar representation of condensed phases in equilibrium with each other at a fixed temperature, pressure, and composition. Since three or four elements are usually involved at a fabricated interface in a semiconductor device, knowledge of the appropriate ternary or quaternary phase diagram is important for optimizing the processing parameters and designing long term stability of devices. While the use of phase diagrams is well-established in the fields of metallurgy, ceramics and mineralogy, only recently have phase diagrams been employed to provide a framework for understanding thin film reactions on a substrate, encountered in semiconductor processing. Even though there are many examples of applications of ternary phase diagrams in the semiconductor literature (for instance, metallization of GaAs, the use of refractory metal silicides for metallization layers in VLSI devices and oxidation of III-V compounds), the same is not true for quaternary phase diagrams. To date, the only application is oxidation of mercury cadmium telluride. This lack of examples is not warranted, as four elements are often involved at a critical interface in compound semiconductor processing and devices. This paper reports on the progress made to remedy this situation by considering the application of quaternary phase diagrams to understanding and predicting the behavior of II-VI thin film interfaces in photovoltaic devices under annealing conditions. Moreover, for the first time, solid solubility is taken into account for quaternary phase diagrams of semiconductor systems.

  11. Modeling of Ion-Pairing Extraction with Quaternary Amines

    Microsoft Academic Search

    I. M. Coelhoso; J. P. S. G. Crespo; M. J. T. Carrondo

    1996-01-01

    The objective of this work is to present a general methodology and to describe the modeling of ion-pairing extraction of organic acids, including amino acids, with quaternary amines, allowing for the prediction of equilibrium concentrations with different operating conditions. The model takes into account the hydration of the organic phase, thus making it also valid for any organic phase used.

  12. Solvent Extraction of Organomercury Compound with Quaternary Amines

    Microsoft Academic Search

    F. L. Moore

    1975-01-01

    Methylmercuric chloride and phenylmercuric acetate extract very efficiently with quaternary amines dissolved in diethylbenzene or other simple solvents. The extraction is effective from either alkaline or acidic solution. The technique considerably extends the scope of conventional solvent extraction practice to permit the extraction and concentration of total mercury in environmental and biological matrices.

  13. Reaction of 2-arylazobenzimidazolium quaternary salts with amines

    Microsoft Academic Search

    R. A. Sogomonova; A. M. Simonov; L. N. Divaeva; S. N. Kolodyazhnaya

    1982-01-01

    Different behaviors of aromatic and nonaromatic amines with respect to a change in the structure of the salt and variations in the reaction conditions were revealed in a study of the reaction of 2-arylazobenzimidazolium quaternary salts with amines. Aliphatic and secondary cyclic amines react at comparable rates via pathways involving cleavage of the azo group and replacement of the hydrogen

  14. Quaternary Ammonium Polysaccharides for Gene Delivery Ira Yudovin-Farber,

    E-print Network

    Linial, Michal

    Quaternary Ammonium Polysaccharides for Gene Delivery Ira Yudovin-Farber, Chava Yanay, Tony Azzam by conjugation of various monoquaternary (MQ) ammonium oligoamines to oxidized dextran by reductive amination that contain primary, secondary, or tertiary amines (11). Under physiological conditions, polyamines become

  15. AREAL DISTRIBUTION OF THE VARIOUS COMBINATIONS OF QUATERNARY CLIMATES

    Microsoft Academic Search

    Stuart A. HARRIS

    Palseoclimates hâve recently been recognized as a major influence in controlling the type of Iandscape, soil and végétation found in diverse areas of the world. Their methods of récognition hâve been discussed and their effects are well known. Most of thèse phenomena hâve been produced in Tertiary and Quaternary times. In this paper, the apparent extent of various simple com-

  16. LARGE-SCALE QUATERNARY DETACHMENTS IN VENTURA BASIN, SOUTHERN CALIFORNIA

    Microsoft Academic Search

    Robert S. Yeats

    1983-01-01

    The Ventura basin is an east-north- east trending trough in the California Transverse Ranges which records major Quaternary detachment faulting at three levels. The earliest thrusting occurred along weak siltstone interbeds in a sequence dominated by competent basin-plain tur- bidite sandstone. Because sedimentation contin- ued during thrusting, the age, rate, and direc- tion of thrusting can be worked out. Faulting

  17. Application of Analytic Geometry to Ternary and Quaternary Diagrams.

    ERIC Educational Resources Information Center

    MacCarthy, Patrick

    1986-01-01

    Advantages of representing ternary and quaternary composition diagrams by means of rectangular coordinates were pointed out in a previous paper (EJ 288 693). A further advantage of that approach is that analytic geometry, based on rectangular coordinates, is directly applicable as demonstrated by the examples presented. (JN)

  18. Prompt gamma-ray coincidences from U-235 induced fission

    NASA Astrophysics Data System (ADS)

    Jewell, J. Keith; Cole, Jerald; Drigert, Mark; Reber, Edward; Aryaeinejad, Rahmat

    1999-10-01

    An experiment to measure gamma-ray emission from the prompt fission fragments of U-235 was recently performed at the Intense Pulsed Neutron Source facility at Argonne National Laboratory. Ten HPGE detectors were used to observe coincident gamma-rays from the fission fragments. Unlike previous fission studies which focused on the fission fragments populated by beta decay, we have measured the prompt fission yields by inducing fission in the U-235 target. Coincidence information between light and heavy fission fragments permits the assignment of observed gamma-rays to a particular isotope. Preliminary analysis indicates new spectroscopic information for dozens of nuclei, as well as the observation of isotopes for which gamma-ray decays were previously unreported. We will report on the prompt fission yields of the major fission fragments, as well as the new spectroscopic information for select nuclei.

  19. A new design of fission detector for prompt fission neutron investigation

    NASA Astrophysics Data System (ADS)

    Zeynalov, Sh.; Zeynalova, O.; Nazarenko, M. A.; Hambsch, F.-J.; Oberstedt, S.

    2012-10-01

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy spectroscopy. Correlated FF kinetic energies, their masses and the angle of the fission axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electronic circuitry and special multi-channel pulse processing apparatus. Mathematical algorithms were provided along with formulae derived for fission axis angles determination. It was shown how the point of fission fragments origin on the target plane may be determined using the same measured data. The last feature made the TIC a rather powerful tool for prompt fission neutron (PFN) emission investigation in event by event analysis of individual fission reactions from non point fissile source. Position sensitive neutron induced fission detector for neutron imaging applications with both thermal and low energy neutrons was found as another possible implementation of the designed TIC.

  20. Systematics on fission fragment mass distribution of neutron induced 235U fission

    Microsoft Academic Search

    Ting-Jin Liu; Zheng-Jun Sun; Neng-Chuan Shu

    2008-01-01

    Based on the neutron induced fission fragment mass distribution data up to neutron energy 20 MeV measured with the double kinetic energy method (KEM) and the radio active method (RAM), the systematics of fission fragment mass distribution was investigated by using 5 Gaussian model and the systematics parameters were obtained by fitting the experimental data. With the systematics, the yields

  1. Options for development of space fission propulsion systems

    NASA Astrophysics Data System (ADS)

    Houts, Mike; van Dyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Salvail, Pat; Hrbud, Ivana

    2001-02-01

    Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include high specific power continuous impulse propulsion systems and bimodal nuclear thermal rockets. Despite their tremendous potential for enhancing or enabling deep space and planetary missions, to date space fission systems have only been used in Earth orbit. The first step towards utilizing advanced fission propulsion systems is development of a safe, near-term, affordable fission system that can enhance or enable near-term missions of interest. An evolutionary approach for developing space fission propulsion systems is proposed. .

  2. Fission Surface Power Technology Development Update

    NASA Technical Reports Server (NTRS)

    Palac, Donald T.; Mason, Lee S.; Houts, Michael G.; Harlow, Scott

    2011-01-01

    Power is a critical consideration in planning exploration of the surfaces of the Moon, Mars, and places beyond. Nuclear power is an important option, especially for locations in the solar system where sunlight is limited or environmental conditions are challenging (e.g., extreme cold, dust storms). NASA and the Department of Energy are maintaining the option for fission surface power for the Moon and Mars by developing and demonstrating technology for a fission surface power system. The Fission Surface Power Systems project has focused on subscale component and subsystem demonstrations to address the feasibility of a low-risk, low-cost approach to space nuclear power for surface missions. Laboratory demonstrations of the liquid metal pump, reactor control drum drive, power conversion, heat rejection, and power management and distribution technologies have validated that the fundamental characteristics and performance of these components and subsystems are consistent with a Fission Surface Power preliminary reference concept. In addition, subscale versions of a non-nuclear reactor simulator, using electric resistance heating in place of the reactor fuel, have been built and operated with liquid metal sodium-potassium and helium/xenon gas heat transfer loops, demonstrating the viability of establishing system-level performance and characteristics of fission surface power technologies without requiring a nuclear reactor. While some component and subsystem testing will continue through 2011 and beyond, the results to date provide sufficient confidence to proceed with system level technology readiness demonstration. To demonstrate the system level readiness of fission surface power in an operationally relevant environment (the primary goal of the Fission Surface Power Systems project), a full scale, 1/4 power Technology Demonstration Unit (TDU) is under development. The TDU will consist of a non-nuclear reactor simulator, a sodium-potassium heat transfer loop, a power conversion unit with electrical controls, and a heat rejection system with a multi-panel radiator assembly. Testing is planned at the Glenn Research Center Vacuum Facility 6 starting in 2012, with vacuum and liquid-nitrogen cold walls to provide simulation of operationally relevant environments. A nominal two-year test campaign is planned including a Phase 1 reactor simulator and power conversion test followed by a Phase 2 integrated system test with radiator panel heat rejection. The testing is expected to demonstrate the readiness and availability of fission surface power as a viable power system option for NASA's exploration needs. In addition to surface power, technology development work within this project is also directly applicable to in-space fission power and propulsion systems.

  3. Decreasing mitochondrial fission prevents cholestatic liver injury.

    PubMed

    Yu, Tianzheng; Wang, Li; Lee, Hakjoo; O'Brien, Dawn K; Bronk, Steven F; Gores, Gregory J; Yoon, Yisang

    2014-12-01

    Mitochondria frequently change their shape through fission and fusion in response to physiological stimuli as well as pathological insults. Disrupted mitochondrial morphology has been observed in cholestatic liver disease. However, the role of mitochondrial shape change in cholestasis is not defined. In this study, using in vitro and in vivo models of bile acid-induced liver injury, we investigated the contribution of mitochondrial morphology to the pathogenesis of cholestatic liver disease. We found that the toxic bile salt glycochenodeoxycholate (GCDC) rapidly fragmented mitochondria, both in primary mouse hepatocytes and in the bile transporter-expressing hepatic cell line McNtcp.24, leading to a significant increase in cell death. GCDC-induced mitochondrial fragmentation was associated with an increase in reactive oxygen species (ROS) levels. We found that preventing mitochondrial fragmentation in GCDC by inhibiting mitochondrial fission significantly decreased not only ROS levels but also cell death. We also induced cholestasis in mouse livers via common bile duct ligation. Using a transgenic mouse model inducibly expressing a dominant-negative fission mutant specifically in the liver, we demonstrated that decreasing mitochondrial fission substantially diminished ROS levels, liver injury, and fibrosis under cholestatic conditions. Taken together, our results provide new evidence that controlling mitochondrial fission is an effective strategy for ameliorating cholestatic liver injury. PMID:25342755

  4. AMS measurements of fission products at CIAE

    NASA Astrophysics Data System (ADS)

    Shen, Hongtao; Jiang, Shan; He, Ming; Dong, Kejun; Ouyang, Yinggen; Li, Zhenyu; Guan, Yongjing; Yin, Xinyi; Peng, Bo; Zhou, Duo; Yuan, Jian; Wu, Shaoyong

    2013-01-01

    Fission products are present in special nuclear materials as contaminants remaining from isotope separation or reprocessing, or through ingrowth due to spontaneous and neutron induced fission. The long half-lived fission products (LLFPs) are among the most dangerous radionuclides to the environment. Ultra-high-sensitivity measurement of LLFPs in rocks or soil samples from the fission environment would provide very important information for nuclear safety inspection. The Beijing HI-13-AMS facility with a high terminal voltage of 13 MV is suitable for measuring LLFPs, especially for heavy fission products such as 79Se, 93Zr, 99Tc, 107Pd, 121mSn, 126Sn, 129I and 151Sm. In this paper some new methods developed for AMS measurement of 79Se, 93Zr, 99Tc, 121mSn, 126Sn, 129I and 151Sm are presented. Major features of these methods will be introduced, including the preparation of samples, the selection of target material and the molecular ions extracted from the material in the ion source, as well as the identification and detection of the nuclides to be determined.

  5. Singlet fission in linear chains of molecules

    NASA Astrophysics Data System (ADS)

    Ambrosio, Francesco; Troisi, Alessandro

    2014-11-01

    We develop a model configuration interaction Hamiltonian to study the electronic structure of a chain of molecules undergoing singlet fission. We first consider models for dimer and trimer and then we use a matrix partitioning technique to build models of arbitrary size able to describe the relevant electronic structure for singlet fission in linear aggregates. We find that the multi-excitonic state (ME) is stabilized at short inter-monomer distance and the extent of this stabilization depends upon the size of orbital coupling between neighboring monomers. We also find that the coupling between ME states located on different molecules is extremely small leading to bandwidths in the order of ˜10 meV. This observation suggests that multi-exciton states are extremely localized by electron-phonon coupling and that singlet fission involves the transition between a relatively delocalized Frenkel exciton and a strongly localized multi-exciton state. We adopt the methodology commonly used to study non-radiative transitions to describe the singlet fission dynamics in these aggregates and we discuss the limit of validity of the approach. The results indicate that the phenomenology of singlet fission in molecular crystals is different in many important ways from what is observed in isolated dimers.

  6. Singlet fission in linear chains of molecules.

    PubMed

    Ambrosio, Francesco; Troisi, Alessandro

    2014-11-28

    We develop a model configuration interaction Hamiltonian to study the electronic structure of a chain of molecules undergoing singlet fission. We first consider models for dimer and trimer and then we use a matrix partitioning technique to build models of arbitrary size able to describe the relevant electronic structure for singlet fission in linear aggregates. We find that the multi-excitonic state (ME) is stabilized at short inter-monomer distance and the extent of this stabilization depends upon the size of orbital coupling between neighboring monomers. We also find that the coupling between ME states located on different molecules is extremely small leading to bandwidths in the order of ?10?meV. This observation suggests that multi-exciton states are extremely localized by electron-phonon coupling and that singlet fission involves the transition between a relatively delocalized Frenkel exciton and a strongly localized multi-exciton state. We adopt the methodology commonly used to study non-radiative transitions to describe the singlet fission dynamics in these aggregates and we discuss the limit of validity of the approach. The results indicate that the phenomenology of singlet fission in molecular crystals is different in many important ways from what is observed in isolated dimers. PMID:25429953

  7. Study on fission blanket fuel cycling of a fusion-fission hybrid energy generation system

    NASA Astrophysics Data System (ADS)

    Zhou, Z.; Yang, Y.; Xu, H.

    2011-10-01

    This paper presents a preliminary study on neutron physics characteristics of a light water cooled fission blanket for a new type subcritical fusion-fission hybrid reactor aiming at electric power generation with low technical limits of fission fuel. The major objective is to study the fission fuel cycling performance in the blanket, which may possess significant impacts on the feasibility of the new concept of fusion-fission hybrid reactor with a high energy gain (M) and tritium breeding ratio (TBR). The COUPLE2 code developed by the Institute of Nuclear and New Energy Technology of Tsinghua University is employed to simulate the neutronic behaviour in the blanket. COUPLE2 combines the particle transport code MCNPX with the fuel depletion code ORIGEN2. The code calculation results show that soft neutron spectrum can yield M > 20 while maintaining TBR >1.15 and the conversion ratio of fissile materials CR > 1 in a reasonably long refuelling cycle (>five years). The preliminary results also indicate that it is rather promising to design a high-performance light water cooled fission blanket of fusion-fission hybrid reactor for electric power generation by directly loading natural or depleted uranium if an ITER-scale tokamak fusion neutron source is achievable.

  8. Low-mass fission detector for the fission neutron spectrum measurement

    SciTech Connect

    Wu, C Y; Henderson, R; Gostic, J; Haight, R C; Lee, H Y

    2010-10-20

    For the fission neutron spectrum measurement, the neutron energy is determined in a time-of-flight experiment by the time difference between the fission event and detection of the neutron. Therefore, the neutron energy resolution is directly determined by the time resolution of both neutron and fission detectors. For the fission detection, the detector needs not only a good timing response but also the tolerance of radiation damage and high {alpha}-decay rate. A parallel-plate avalanche counter (PPAC) has many advantages for the detection of heavy charged particles such as fission fragments. These include fast timing, resistance to radiation damage, and tolerance of high counting rate. A PPAC also can be tuned to be insensitive to particles, which is important for experiments with - emitting actinides. Therefore, a PPAC is an ideal detector for experiments requiring a fast and clean trigger for fission. In the following sections, the description will be given for the design and performance of a new low-mass PPAC for the fission-neutron spectrum measurements at LANL.

  9. Final excitation energy of fission fragments

    SciTech Connect

    Schmidt, Karl-Heinz; Jurado, Beatriz [Centre d'Etudes Nucleaires de Bordeaux Gradignan (CENBG), CNRS/IN2P3, Chemin du Solarium, B.P. 120, F-33175 Gradignan (France)

    2011-06-15

    We study how the excitation energy of the fully accelerated fission fragments is built up. It is stressed that only the intrinsic excitation energy available before scission can be exchanged between the fission fragments to achieve thermal equilibrium. This is in contradiction with most models used to calculate prompt neutron emission, where it is assumed that the total excitation energy of the final fragments is shared between the fragments by the condition of equal temperatures. We also study the intrinsic excitation-energy partition in statistical equilibrium for different level-density descriptions as a function of the total intrinsic excitation energy of the fissioning system. Excitation energies are found to be strongly enhanced in the heavy fragment, if the level density follows a constant-temperature behavior at low energies, e.g., in the composed Gilbert-Cameron description.

  10. Phase Transition Induced Fission in Lipid Vesicles

    E-print Network

    C. Leirer; B. Wunderlich; V. M. Myles; M. F. Schneider

    2010-05-24

    In this work we demonstrate how the first order phase transition in giant unilamellar vesicles (GUVs) can function as a trigger for membrane fission. When driven through their gel-fluid phase transition GUVs exhibit budding or pearl formation. These buds remain connected to the mother vesicle presumably by a small neck. Cooling these vesicles from the fluid phase (T>Tm) through the phase transition into the gel state (Tfission of the neck, while the mother vesicle remains intact. Pearling tubes which formed upon heating break-up and decay into multiple individual vesicles which then diffuse freely. Finally we demonstrate that mimicking the intracellular bulk viscosity by increasing the bulk viscosity to 40cP does not affect the overall fission process, but leads to a significant decrease in size of the released vesicles.

  11. Energy partition in low energy fission

    E-print Network

    M. Mirea

    2011-02-14

    The intrinsic excitation energy of fission fragments is dynamically evaluated in terms of the time dependent pairing equations. These equations are corroborated with two conditions. One of them fixes the number of particles and the another separates the pairing active spaces associated to the two fragments in the vicinity of the scission configuration. The fission path is obtained in the frame of the macroscopic-microscopic model. The single particle level schemes are obtained within the two center Woods-Saxon shell model. It is shown that the available intrinsic dissipated energy is not shared proportionally to the masses of the two fission fragments. If the heavy fragment possesses nucleon numbers close to the magic ones, the accumulated intrinsic excitation energy is lower than that of the light fragment.

  12. Dissipative dynamics in quasi-fission

    E-print Network

    V. E. Oberacker; A. S. Umar; C. Simenel

    2014-09-10

    Quasi-fission is the primary reaction mechanism that prevents the formation of superheavy elements in heavy-ion fusion experiments. Employing the time-dependent density functional theory approach we study quasi-fission in the systems $^{40,48}$Ca+$^{238}$U. Results show that for $^{48}$Ca projectiles the quasi-fission is substantially reduced in comparison to the $^{40}$Ca case. This partly explains the success of superheavy element formation with $^{48}$Ca beams. For the first time, we also calculate the repartition of excitation energies of the two fragments in a dynamic microscopic theory. The system is found in quasi-thermal equilibrium only for reactions with $^{40}$Ca. The differences between both systems are interpreted in terms of initial neutron to proton asymmetry of the colliding partners.

  13. Prompt fission neutron emission: Problems and challenges

    NASA Astrophysics Data System (ADS)

    Hambsch, F.-J.; Bry?, T.; Gamboni, T.; Geerts, W.; Göök, A.; Matei, C.; Oberstedt, S.; Vidali, M.

    2013-12-01

    This paper presents some of the challenges ahead of us even after 75 years of the discovery of the fission process and large progress made since then. The focus is on application orientation, which requires improved measurements on fission cross-sections and neutron and ?-ray multiplicities. Experimental possibilities have vastly improved the past decade leading to developments of highly sophisticated detector systems and the use of digital data acquisition and signal processing. The development of innovative fast nuclear reactor technology needs improved respective nuclear data. Advancements in theoretical modelling also require better experimental data. Theory has made progress in calculating fission fragment distributions (i.e. GEF code) as well as prompt neutron and ?-ray emission to catch up with the improved experiments.

  14. Lunar surface fission power supplies: Radiation issues

    SciTech Connect

    Houts, M.G.; Lee, S.K.

    1994-07-01

    A lunar space fission power supply shield that uses a combination of lunar regolith and materials brought from earth may be optimal for early lunar outposts and bases. This type of shield can be designed such that the fission power supply does not have to be moved from its landing configuration, minimizing handling and required equipment on the lunar surface. Mechanisms for removing heat from the lunar regolith are built into the shield, and can be tested on earth. Regolith activation is greatly reduced compared with a shield that uses only regolith, and it is possible to keep the thermal conditions of the fission power supply close to these seen in free space. For a well designed shield, the additional mass required to be brought fro earth should be less than 1000 kg. Detailed radiation transport calculations confirm the feasibility of such a shield.

  15. Lunar surface fission power supplies: Radiation issues

    NASA Astrophysics Data System (ADS)

    Houts, M. G.; Lee, S. K.

    1994-06-01

    A lunar space fission power supply shield that uses a combination of lunar regolith and materials brought from earth may be optimal for early lunar outposts and bases. This type of shield can be designed such that the fission power supply does not have to be moved from its landing configuration, minimizing handling and required equipment on the lunar surface. Mechanisms for removing heat from the lunar regolith are built into the shield, and can be tested on earth. Regolith activation is greatly reduced compared with a shield that uses only regolith, and it is possible to keep the thermal conditions of the fission power supply close to these seen in free space. For a well designed shield, the additional mass required to be brought from earth should be less than 1000 kg. Detailed radiation transport calculations confirm the feasibility of such a shield.

  16. A microscopic model of singlet fission.

    PubMed

    Teichen, Paul E; Eaves, Joel D

    2012-09-20

    Singlet fission, where an electronically excited singlet on one chromophore converts into a doubly excited state on two, has gone from a curiosity in organic photophysics to a potential pathway for increasing solar energy conversion efficiencies. Focusing on the role of solvent-induced energy level fluctuations that would be present in a dye-sensitized solar cell, we present a microscopic model for singlet fission. Starting from an electronic model Hamiltonian, we construct diabatic states in a manifold of single and double excitations with total singlet multiplicity and then develop a multilevel non-Markovian theory of dynamics for electronic populations in the presence of energy level fluctuations. Depending on the energy scales, energy gap fluctuations can either facilitate or hinder interconversion steps that lead to singlet fission. We critically assess the Markovian approximation that leads to golden rule rates and study the role of intramolecular solvation dynamics and electron transfer. PMID:22587487

  17. Solution-processable singlet fission photovoltaic devices.

    PubMed

    Yang, Le; Tabachnyk, Maxim; Bayliss, Sam L; Böhm, Marcus L; Broch, Katharina; Greenham, Neil C; Friend, Richard H; Ehrler, Bruno

    2015-01-14

    We demonstrate the successful incorporation of a solution-processable singlet fission material, 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), into photovoltaic devices. TIPS-pentacene rapidly converts high-energy singlet excitons into pairs of triplet excitons via singlet fission, potentially doubling the photocurrent from high-energy photons. Low-energy photons are captured by small-bandgap electron-accepting lead chalcogenide nanocrystals. This is the first solution-processable singlet fission system that performs with substantial efficiency with maximum power conversion efficiencies exceeding 4.8%, and external quantum efficiencies of up to 60% in the TIPS-pentacene absorption range. With PbSe nanocrystal of suitable bandgap, its internal quantum efficiency reaches 170 ± 30%. PMID:25517654

  18. Quantitative Intramolecular Singlet Fission in Bipentacenes.

    PubMed

    Sanders, Samuel N; Kumarasamy, Elango; Pun, Andrew B; Trinh, M Tuan; Choi, Bonnie; Xia, Jianlong; Taffet, Elliot J; Low, Jonathan Z; Miller, John R; Roy, Xavier; Zhu, X-Y; Steigerwald, Michael L; Sfeir, Matthew Y; Campos, Luis M

    2015-07-22

    Singlet fission (SF) has the potential to significantly enhance the photocurrent in single-junction solar cells and thus raise the power conversion efficiency from the Shockley-Queisser limit of 33% to 44%. Until now, quantitative SF yield at room temperature has been observed only in crystalline solids or aggregates of oligoacenes. Here, we employ transient absorption spectroscopy, ultrafast photoluminescence spectroscopy, and triplet photosensitization to demonstrate intramolecular singlet fission (iSF) with triplet yields approaching 200% per absorbed photon in a series of bipentacenes. Crucially, in dilute solution of these systems, SF does not depend on intermolecular interactions. Instead, SF is an intrinsic property of the molecules, with both the fission rate and resulting triplet lifetime determined by the degree of electronic coupling between covalently linked pentacene molecules. We found that the triplet pair lifetime can be as short as 0.5 ns but can be extended up to 270 ns. PMID:26102432

  19. PASSAGE OF FISSION PRODUCTS THROUGH THE SKIN OF TUNA

    E-print Network

    was slow. PASSAGE OF FISSION PRODUCTS THROUGH THE SKIN OF TUNA In relation to "fallout" from nuclear -bomb the penetration of radioactive strontium, cesium, and ruthenium common products of nuclear fission, through

  20. Luminescence dating of quaternary deposits in geology in Brazil.

    PubMed

    Tatumi, Sonia Hatsue; Gozzi, Giuliano; Yee, Márcio; de Oliveira, Victor Inácio; Sallun, Alethéa Ernandes Martins; Suguio, Kenitiro

    2006-01-01

    In the present work, systematic dating by luminescence methods has been done on 50 Quaternary geological samples within the study area of São Paulo State, Brazil. Bleaching experiments showed that residual TL intensity of 375 degrees C peak, of the quartz, was obtained after 10 h of sunlight exposition. Intensities decays of the 325 and 375 degrees C TL peaks can be fitted using second order exponential equation. Paleodose values were evaluated using regeneration methods with multiple aliquots. Samples dated indicate preliminary ages varying from 9 +/- 1 to 935 +/- 130 ka for colluvio-elluvial deposits, and from 17 +/- 2 to 215 +/- 30 ka for alluvial deposits of the study area. They cover four peneplained surfaces shaped during the Quaternary: I (1000-400 ka), II (400-120 ka), III (120-10 ka) and IV (10 ka until today), in decreasing order. PMID:16782979

  1. Quaternary Fault and Fold Database of the United States

    NSDL National Science Digital Library

    This database summarizes geologic, geomorphic, and geographic information for about 2,000 Quaternary faults and folds in the United States. These structures are believed to be sources of magnitude 6 or greater earthquakes during the Quaternary Period (the past 1,600,000 years). Maps of these geologic structures are linked to detailed descriptions, including geologic setting, fault orientation, fault type, sense of movement, slip rate, recurrence (repeat) interval, and the time of the most recent surface-faulting event. The database is searchable by using an interactive map viewer, a state/regional interactive map, or a text-based search. There is also a link to a fact sheet that provides information about the database.

  2. Community ecology in a changing environment: Perspectives from the Quaternary

    PubMed Central

    Jackson, Stephen T.; Blois, Jessica L.

    2015-01-01

    Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a “missing middle”: Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit. PMID:25901314

  3. Community ecology in a changing environment: Perspectives from the Quaternary.

    PubMed

    Jackson, Stephen T; Blois, Jessica L

    2015-04-21

    Community ecology and paleoecology are both concerned with the composition and structure of biotic assemblages but are largely disconnected. Community ecology focuses on existing species assemblages and recently has begun to integrate history (phylogeny and continental or intercontinental dispersal) to constrain community processes. This division has left a "missing middle": Ecological and environmental processes occurring on timescales from decades to millennia are not yet fully incorporated into community ecology. Quaternary paleoecology has a wealth of data documenting ecological dynamics at these timescales, and both fields can benefit from greater interaction and articulation. We discuss ecological insights revealed by Quaternary terrestrial records, suggest foundations for bridging between the disciplines, and identify topics where the disciplines can engage to mutual benefit. PMID:25901314

  4. Helix Bundle Quaternary Structure from [alpha]/[beta]-Peptide Foldamers

    SciTech Connect

    Horne, W. Seth; Price, Joshua L.; Keck, James L.; Gellman, Samuel H. (UW-MED)

    2008-11-18

    The function of a protein generally depends on adoption of a specific folding pattern, which in turn is determined by the side chain sequence along the polypeptide backbone. Here we show that the sequence-encoded structural information in peptides derived from yeast transcriptional activator GCN4 can be used to prepare hybrid {alpha}/{beta}-peptide foldamers that adopt helix bundle quaternary structures. Crystal structures of two hybrid {alpha}/{beta}-peptides are reported along with detailed structural comparison to {alpha}-peptides of analogous side chain sequence. There is considerable homology between {alpha}- and {alpha}/{beta}-peptides at the level of helical secondary structure, with modest but significant differences in the association geometry of helices in the quaternary structure.

  5. ?-CD assisted dissolution of quaternary ammonium permanganates in aqueous medium.

    PubMed

    Bank, Suraj Prakash; Guru, Partha Sarathi; Dash, Sukalyan

    2014-10-13

    The non-polar internal cavity of ?-cyclodextrin (?-CD) has been exploited for the entrapment of the hydrophobic tails of two water insoluble quaternary ammonium permanganates (QAPs): cetyltrimethylammonium permanganate (CTAP) and tetrabutylammonium permanganate (TBAP), for solubilization in aqueous medium. The solubilization and organizational behavior of the QAPs in aqueous ?-CD solution have been determined from the comparison of their rates of self-oxidation in presence and in absence of ?-CD. Effect of QAP concentration on their observed rate constants (k(obs)) at a fixed ?-CD concentration, phase solubility analysis in varying ?-CD concentration, impact of quaternary ammonium bromides (QABs) on the kobs values of CTAP and TBAP at fixed QAP and ?-CD concentrations, and the temperature effect have been reported. A scheme to explain the solvation of QAPs in aqueous ?-CD has been proposed based on dynamic light scattering (DLS) analysis of the samples. PMID:25037419

  6. A new spin gapless semiconductors family: Quaternary Heusler compounds

    NASA Astrophysics Data System (ADS)

    Xu, G. Z.; Liu, E. K.; Du, Y.; Li, G. J.; Liu, G. D.; Wang, W. H.; Wu, G. H.

    2013-04-01

    By using first-principles calculations, we investigate the band structures of a series of quaternary LiMgPdSn-type Heusler compounds. Our calculation results show that five compounds, CoFeMnSi, CoFeCrAl, CoMnCrSi, CoFeVSi and FeMnCrSb, possess unique electronic structures characterized by a half-metallic gap in one spin direction while they have a zero-width gap in the other spin direction showing a spin gapless semiconducting behavior. We further analyse the electronic and magnetic properties of all quaternary Heusler alloys involved, and reveal a semi-empirical general rule (the total valence electrons number should be 26 or 28) for indentifying spin gapless semiconductors in Heusler compounds. The influences of lattice distortion and main-group element change have also been discussed.

  7. Dynamic fission instability of dissipative protoplanets

    NASA Technical Reports Server (NTRS)

    Boss, A. P.; Mizuno, H.

    1985-01-01

    Analytical and numerical approaches are taken to consider if a rapidly rotating, viscous protoearth would have lost mass by a fission process and thereby given birth to the moon. The fast rotation is assumed as the source of the instability in the dissipative liquid protoearth. Governing hydrodynamic equations are defined for the evolution of the protoearth. Account is taken of viscous dissipation, the pressure equation of state for the atmospheric material sent on a ballistic trajectory, and the effective viscosity. The results indicate that dynamic fission was probably not the process by which the protomoon came into existence.

  8. In-beam Fission Study at JAEA

    NASA Astrophysics Data System (ADS)

    Nishio, Katsuhisa

    2013-12-01

    Fission fragment mass distributions were measured in heavy-ion induced fissions using 238U target nucleus. The measured mass distributions changed drastically with incident energy. The results are explained by a change of the ratio between fusion and quasifission with nuclear orientation. A calculation based on a fluctuation dissipation model reproduced the mass distributions and their incident energy dependence. Fusion probability was determined in the analysis. Evaporation residue cross sections were calculated with a statistical model in the reactions of 30Si + 238U and 34S + 238U using the obtained fusion probability in the entrance channel. The results agree with the measured cross sections for seaborgium and hassium isotopes.

  9. Laser spectroscopy of cooled zirconium fission fragments.

    PubMed

    Campbell, P; Thayer, H L; Billowes, J; Dendooven, P; Flanagan, K T; Forest, D H; Griffith, J A R; Huikari, J; Jokinen, A; Moore, R; Nieminen, A; Tungate, G; Zemlyanoi, S; Aystö, J

    2002-08-19

    The first on-line laser spectroscopy of cooled fission fragments is reported. The r ions, produced in uranium fission, were extracted and separated using an ion guide isotope separator. The ions were cooled and bunched for collinear laser spectroscopy by a gas-filled linear Paul trap. New results for nuclear mean-square charge radii, dipole, and quadrupole moments are reported across the N=60 shape change. The mean-square charge radii are found to be almost identical to those of the Sr isotones and previously offered modeling of the radial changes is critically reviewed. PMID:12190460

  10. Humidity sensor using epoxy resin containing quaternary ammonium salts

    Microsoft Academic Search

    Chil-Won Lee; Hee-Woo Rhee; Myoung-Seon Gong

    2001-01-01

    Humidity-sensitive epoxy monomer, glycidyl trimethyl ammonium chloride (GTMAC) was selected as the humidity-sensing resin. Polypropylene glycol diglycidyl ether (PPGDGE) and methyl tetrahydrophthalic anhydride (MTPHA) were used as a comonomer and a curing agent, respectively. The humidity-sensitive membranes were composed of GTMAC, PPGDGE and MTPHA. When impedance characteristics of the epoxy resins containing quaternary ammonium salts were measured, the impedance decreased

  11. Antibacterial activity of quaternary ammonium salt grafted cotton

    Microsoft Academic Search

    N. Ladhari; M. H. V. Baouab; Abdelbasset Ben Dekhil; Amina Bakhrouf; P. Niquette

    2007-01-01

    Cotton having good antibacterial activity can be obtained without the need for a binding chemical as a cross linker or the need for chemically pre-treated antibacterial agent. The procedure of synthesis consists in grafting an alkali-cellulose fibre by a quaternary ammonium salt: Epoxy propyltrimethylammonium chloride (EPTMAC). The characterization of grafted cotton (EPTMAC-Cotton) has been targeted on the nitrogen and the

  12. Quaternary fluvial archives: achievements of the Fluvial Archives Group

    NASA Astrophysics Data System (ADS)

    Bridgland, David; Cordier, Stephane; Herget, Juergen; Mather, Ann; Vandenberghe, Jef; Maddy, Darrel

    2013-04-01

    In their geomorphological and sedimentary records, rivers provide valuable archives of environments and environmental change, at local to global scales. In particular, fluvial sediments represent databanks of palaeoenvironment and palaeoclimatic (for example) of fossils (micro- and macro-), sedimentary and post-depositional features and buried soils. Well-dated sequences are of the most value, with dating provided by a wide range of methods, from radiometric (numerical) techniques to included fossils (biostratigraphy) and/or archaeological material. Thus Quaternary fluvial archives can also provide important data for studies of Quaternary biotic evolution and early human occupation. In addition, the physical disposition of fluvial sequences, be it as fragmented terrace remnants or as stacked basin-fills, provides valuable information about geomorphological and crustal evolution. Since rivers are long-term persistent features in the landscape, their sedimentary archives can represent important frameworks for regional Quaternary stratigraphy. Fluvial archives are distributed globally, being represented on all continents and across all climatic zones, with the exception of the frozen polar regions and the driest deserts. In 1999 the Fluvial Archives Group (FLAG) was established, as a working group of the Quaternary Research Association (UK), aimed at bringing together those interested in such archives. This has evolved into an informal organization that has held regular biennial combined conference and field-trip meetings, has co-sponsored other meetings and conference sessions, and has presided over two International Geoscience Programme (IGCP) projects: IGCP 449 (2000-2004) 'Global Correlation of Late Cenozoic Fluvial Deposits' and IGCP 518 (2005-2007) 'Fluvial sequences as evidence for landscape and climatic evolution in the Late Cenozoic'. Through these various activities a sequence of FLAG publications has appeared, including special issues in a variety of journals, amassing a substantial volume of information on fluvial archives worldwide. This presentation will highlight some of these data and will describe important patterns observed and interpretations arising therefrom.

  13. Quaternary TL Surveys: A Guide to Thermoluminescence (TL) Date Measurement

    NSDL National Science Digital Library

    Quaternary TL Surveys, a company that provides date measurement services to archaeologists and geologists, offers this comprehensive tutorial on archaeometric dating techniques. The tutorial contains a general overview as well as specific information on dating flint and stone, stalagmitic calcite, sediments, and methods of interpreting and using TL dates. For ease of use, portions of the guide are marked to alert users to their relative importance.

  14. Vegetation ecotone dynamics in Southwest Alaska during the Late Quaternary

    Microsoft Academic Search

    Linda B. Brubaker; Patricia M. Anderson; Feng Sheng Hu

    2001-01-01

    To examine Late Quaternary vegetation change across the modern vegetation gradient from continuous boreal forest (central Alaska) to Betula shrub tundra (Bristol Bay region), pollen records from Idavain and Snipe Lakes are described and compared to those of four other sites in southwest Alaska. Major features of the vegetation history at Idavain Lake include herb-dominated tundra (ca 14–12kaBP), mixed herb\\/Betula

  15. Low Sensitivity of Listeria monocytogenes to Quaternary Ammonium Compounds

    Microsoft Academic Search

    L. Mereghetti; R. Quentin; N. Marquet-Van Der Mee; A. Audurier

    2000-01-01

    Ninety-seven epidemiologically unrelated strains of Listeria monocytogenes were investigated for their sen- sitivities to quaternary ammonium compounds (benzalkonium chloride and cetrimide). The MICs for seven serogroup 1\\/2 strains were high. Three came from the environment and four came from food; none were isolated from human or animal samples. All 97 strains carried the mdrL gene, which encodes a multidrug efflux

  16. Precise timing and rate of massive late Quaternary soil denudation

    Microsoft Academic Search

    M. Jennifer Cooke; Libby A. Stern; Jay L. Banner; Lawrence E. Mack; Thomas W. Stafford; Rickard S. Toomey

    2003-01-01

    Strontium isotopes are a unique tool to study soil-erosion dynamics. Changes in Sr isotope ratios (87Sr\\/86Sr) provide a record of late Quaternary landscape denudation of the Edwards Plateau of central Texas, United States. The use of Sr isotopes as a tracer for soil erosion is based on the observation that, in central Texas, the 87Sr\\/86Sr ratio of soil correlates with

  17. Primary biodegradation of amine oxide and quaternary ammonium amphiphiles.

    PubMed

    Cupková, V; Sirotková, L; Mlynarcík, D; Devínsky, F; Lacko, I; Kovacková, Z

    1993-01-01

    Biodegradation of two amphiphilic "soft" antimicrobially active derivatives of lauric (dodecanoic) acid, a quaternary ammonium salt and an amine oxide bearing an amide or ester group, was followed using microorganisms from activated sludge. Primary biodegradation was determined by ion-selective electrodes, total biodegradation as the chemical oxygen demand. Though organic ammonium salts quickly undergo primary biodegradation, the rest of the molecule is difficult to destroy. In contrast, amine oxides are easily biodegradable. PMID:8500780

  18. Composite aromatic boxes for enzymatic transformations of quaternary ammonium substrates.

    PubMed

    Nagy, Gergely N; Marton, Lívia; Contet, Alicia; Ozohanics, Olivér; Ardelean, Laura-Mihaela; Révész, Agnes; Vékey, Károly; Irimie, Florin Dan; Vial, Henri; Cerdan, Rachel; Vértessy, Beáta G

    2014-12-01

    Cation-? interactions to cognate ligands in enzymes have key roles in ligand binding and enzymatic catalysis. We have deciphered the key functional role of both charged and aromatic residues within the choline binding subsite of CTP:phosphocholine cytidylyltransferase and choline kinase from Plasmodium falciparum. Comparison of quaternary ammonium binding site structures revealed a general composite aromatic box pattern of enzyme recognition sites, well distinguished from the aromatic box recognition site of receptors. PMID:25283789

  19. Analytical 13 C NMR spectroscopy of fatty quaternary amines

    Microsoft Academic Search

    E. H. Fairchild

    1982-01-01

    Natural abundance13C nuclear magnetic resonance spectroscopy (CMR) has been used for the rapid, nondestructive analysis of fatty quaternary ammonium\\u000a compounds. Quantitative analysis of mixtures of mono-, di-and tri-fatty ammonium chlorides can be accommpublished under conditions\\u000a that do not involve heat or extremes of pH and that are independent of solvent present. In order to determine optimal conditions\\u000a for quantitative studies,

  20. Activity of an insoluble antimicrobial quaternary amine complex in plastics

    Microsoft Academic Search

    D. L. Price; A. D. Sawant; D. G. Ahearn

    1991-01-01

    Summary Growth and survival ofStaphylococcus aureus, Pseudomonas aeruginosa., Klebsiella pneumoniae andAspergillus niger were reduced by a low-solubility polysubstituted.-quaternary amine complex (InterseptR) processed into the matrices of ethylene vinyl acetate, polystyrene and polyethylene., Recoveries of challenge microorganisms from agar film overlays and determination of the effects of the complex on radiolabelled-leucine transport by adhered cells and bacterial biofilms were more suitable

  1. Large-scale quaternary detachments in Ventura basin, southern California

    Microsoft Academic Search

    Robert S. Yeats

    1983-01-01

    The Ventura basin is an east-north-east trending trough in the California Transverse Ranges which records major Quaternary detachment faulting at three levels. The earliest thrusting occurred along weak siltstone interbeds in a sequence dominated by competent basin-plain turbidite sandstone. Because sedimentation continued during thrusting, the age, rate, and direction of thrusting can be worked out. Faulting began 1.3 m.y. ago

  2. NMR enantiodifferentiation of quaternary ammonium salts of Tröger base.

    PubMed

    Michon, Christophe; Gonçalves-Farbos, Maria-Héléna; Lacour, Jérôme

    2009-10-01

    Hexacoordinated phosphorus BINPHAT anion 1 is an efficient NMR chiral solvating agent for quaternary ammonium cations (quats) derived from Tröger base leading to large separations of the proton signals of the enantiomers and even in polar solvent media such as CD(3)CN (Delta Delta delta up to 0.12 ppm). Quite surprisingly, this efficacy in the NMR split efficiency is not translated into a supramolecular stereocontrol (Pfeiffer effect) of the cation configuration by the anion. PMID:19161219

  3. Efficient formation of benzylic quaternary centers via palladium catalysis.

    PubMed

    Gottumukkala, Aditya L; Suljagic, Jasmin; Matcha, Kiran; de Vries, Johannes G; Minnaard, Adriaan J

    2013-09-01

    Four's a crowd: An efficient protocol for the formation of benzylic quaternary centers via arylation of enones using a catalyst made from Pd(O2 CCF3 )2 and 2,2'-bipyridine is developed. For cyclic substrates, catalyst loadings as low as 1 mol % Pd are enough to afford excellent yields (>90%) using a variety of arylboronic acids. In case of acyclic substrates, the addition of KSbF6 was found to improve conversions and yields. PMID:23821532

  4. Analysis of Human Dopamine D3 Receptor Quaternary Structure*

    PubMed Central

    Marsango, Sara; Caltabiano, Gianluigi; Pou, Chantevy; Varela Liste, María José; Milligan, Graeme

    2015-01-01

    The dopamine D3 receptor is a class A, rhodopsin-like G protein-coupled receptor that can form dimers and/or higher order oligomers. However, the molecular basis for production of these complexes is not well defined. Using combinations of molecular modeling, site-directed mutagenesis, and homogenous time-resolved FRET, the interfaces that allow dopamine D3 receptor monomers to interact were defined and used to describe likely quaternary arrangements of the receptor. These were then compared with published crystal structures of dimeric ?1-adrenoreceptor, ?-opioid, and CXCR4 receptors. The data indicate important contributions of residues from within each of transmembrane domains I, II, IV, V, VI, and VII as well as the intracellular helix VIII in the formation of D3-D3 receptor interfaces within homo-oligomers and are consistent with the D3 receptor adopting a ?1-adrenoreceptor-like quaternary arrangement. Specifically, results suggest that D3 protomers can interact with each other via at least two distinct interfaces: the first one comprising residues from transmembrane domains I and II along with those from helix VIII and a second one involving transmembrane domains IV and V. Moreover, rather than existing only as distinct dimeric species, the results are consistent with the D3 receptor also assuming a quaternary structure in which two transmembrane domain I-II-helix VIII dimers interact to form a ”rhombic” tetramer via an interface involving residues from transmembrane domains VI and VII. In addition, the results also provide insights into the potential contribution of molecules of cholesterol to the overall organization and potential stability of the D3 receptor and possibly other GPCR quaternary structures. PMID:25931118

  5. Preliminary results utilizing high-energy fission product ?-rays to detect fissionable material in cargo

    NASA Astrophysics Data System (ADS)

    Slaughter, D. R.; Accatino, M. R.; Bernstein, A.; Church, J. A.; Descalle, M. A.; Gosnell, T. B.; Hall, J. M.; Loshak, A.; Manatt, D. R.; Mauger, G. J.; Moore, T. L.; Norman, E. B.; Pohl, B. A.; Pruet, J. A.; Petersen, D. C.; Walling, R. S.; Weirup, D. L.; Prussin, S. G.; McDowell, M.

    2005-12-01

    A concept for detecting the presence of special nuclear material (235U or 239Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their ?-delayed neutron emission or ?-delayed high-energy ? radiation between beam pulses provide the detection signature. Fission product ?-delayed ?-rays above 3 MeV are nearly 10 times more abundant than ?-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified.

  6. New fission mode of the 252Cf spontaneous fission obtained with modern HPGE detectors

    NASA Astrophysics Data System (ADS)

    Daniel, A. V.; Ter-Akopian, G. M.; Hamilton, J. H.; Oganessian, Yu. Ts.; Kormicki, J.; Popeko, G. S.; Ramayya, A. V.; Ma, W.-C.; Babu, B. R. S.; Ginter, T.; Zhu, S. J.; Rasmussen, J.; Stoyer, M. A.; Lee, I. Y.; Asztalos, S.; Chu, S. Y.; Gregorich, K. E.; Macchiavelli, A. O.; Mohar, M. F.; Prussin, S. G.; Kliman, J.; Morhac, M.; Cole, J. D.; Aryaeinejad, R.; Dardenne, Y. K.; Driger, M.

    1998-02-01

    The data of Independent yields of secondary fission fragment pairs (emerging after prompt neutron emission from primary fragment pairs) obtained by detecting coincidences between ? rays following the spontaneous fission of 252Cf have been expanded. Our approach to estimate characteristics of the primary fragments pairs (mass and excitation energy distributions) by unfolding the yields of secondary fragment pairs is discussed. Mew model parameters were introduced and results are presented here. The new results confirmed our old assumption that in case of Mo-Ba charge split the two fission modes differing with average total kinetic energy on ˜36 MeV are realized.

  7. Simulated Atomic Fission Engine (S.A.F.E)

    NASA Technical Reports Server (NTRS)

    VanDyke, Melissa

    1999-01-01

    This paper presents viewgraphs of S.A.F.E. (Simulated Atomic Fission Engine). The topics include: 1) Why Space Fission Propulsion? 2) History of Fission System Development; 3) New Approach to Space Fission Propulsion System Development; 4) Propulsion Flight Demonstrator Schematic Flight Configuration; 5) Ongoing Propellant Energy Source Tests; 6) First Generation Propulsion System Status; 7) Tungsten Fuel Pin Simulator Tests; 8) Full Module Test (High Efficiency Mode); and 9) First Generation Propulsion Flight Demonstrator Status.

  8. Mass distribution in 19F induced fission of 232Th

    Microsoft Academic Search

    G. K. Gubbi; A. Goswami; B. S. Tomar; B. John; A. Ramaswami; A. V. R. Reddy; P. P. Burte; S. B. Manohar

    1996-01-01

    Formation cross sections of several fission products have been determined using the recoil catcher technique followed by gamma-ray spectrometry in 19F induced fission of 232Th at Elab=95 and 112 MeV. The data show significant admixture of fission from compound nuclei formed by complete fusion as well as targetlike nuclei formed by transfer reactions. Mass distributions for both the fissioning systems

  9. Mass distribution in 11B induced fission of 232Th

    Microsoft Academic Search

    G. K. Gubbi; A. Goswami; B. S. Tomar; A. Ramaswami; A. V. R. Reddy; P. P. Burte; S. B. Manohar; B. John

    1999-01-01

    Formation cross sections of several fission products have been determined using recoil catcher technique followed by gamma-ray spectrometry in 11B induced fission of 232Th at Elab=72, 60, and 55 MeV. The data show significant admixture of fission from compound nucleus formed by complete fusion as well as targetlike nuclei formed by transfer reaction. Mass distributions for both the fissioning systems

  10. Mass distributions in nucleon-induced fission at intermediate energies

    Microsoft Academic Search

    M. C. Duijvestijn; A. J. Koning; F.-J. Hambsch

    2001-01-01

    Temperature-dependent fission barriers and fission-fragment mass distributions are calculated in the framework of the multimodal random neck-rupture model (MM-RNRM). It is shown how the distinction between the different fission modes disappears at higher excitation energies, due to the melting of shell effects. The fission-fragment mass yield calculations are coupled to the nuclear reaction code ALICE-91, which takes into account the

  11. Optimally moderated nuclear fission reactor and fuel source therefor

    DOEpatents

    Ougouag, Abderrafi M. (Idaho Falls, ID); Terry, William K. (Shelley, ID); Gougar, Hans D. (Idaho Falls, ID)

    2008-07-22

    An improved nuclear fission reactor of the continuous fueling type involves determining an asymptotic equilibrium state for the nuclear fission reactor and providing the reactor with a moderator-to-fuel ratio that is optimally moderated for the asymptotic equilibrium state of the nuclear fission reactor; the fuel-to-moderator ratio allowing the nuclear fission reactor to be substantially continuously operated in an optimally moderated state.

  12. Protein flexibility facilitates quaternary structure assembly and evolution.

    PubMed

    Marsh, Joseph A; Teichmann, Sarah A

    2014-05-01

    The intrinsic flexibility of proteins allows them to undergo large conformational fluctuations in solution or upon interaction with other molecules. Proteins also commonly assemble into complexes with diverse quaternary structure arrangements. Here we investigate how the flexibility of individual protein chains influences the assembly and evolution of protein complexes. We find that flexibility appears to be particularly conducive to the formation of heterologous (i.e., asymmetric) intersubunit interfaces. This leads to a strong association between subunit flexibility and homomeric complexes with cyclic and asymmetric quaternary structure topologies. Similarly, we also observe that the more nonhomologous subunits that assemble together within a complex, the more flexible those subunits tend to be. Importantly, these findings suggest that subunit flexibility should be closely related to the evolutionary history of a complex. We confirm this by showing that evolutionarily more recent subunits are generally more flexible than evolutionarily older subunits. Finally, we investigate the very different explorations of quaternary structure space that have occurred in different evolutionary lineages. In particular, the increased flexibility of eukaryotic proteins appears to enable the assembly of heteromeric complexes with more unique components. PMID:24866000

  13. Ranges in Air and Mass Identification of Plutonium Fission Fragments

    Microsoft Academic Search

    Seymour Katcoff; John A. Miskel; Charles W. Stanley

    1948-01-01

    Determinations were made of the mean and extrapolated ranges in air of plutonium fission fragments for twenty individual masses between 83 and 157. Collimated fission fragments passing through air at 120 or 140 mm pressure were deposited, after being stopped by the air, on a series of fourteen thin lacquer films. These were analyzed radio-chemically for individual fission products. The

  14. Fission measurements with PPAC detectors using a coincidence technique

    SciTech Connect

    Paradela, C.; Duran, I.; Tarrio, D. [Universidad de Santiago de Compostela (Spain); Audouin, L.; Tassan-Got, L.; Stephan, C. [Inst. de Physique Nucleaire d'Orsay (France)

    2011-07-01

    A fission detection setup based on Parallel Plate Avalanche Counters (PPAC) has been constructed and used at the CERN n-TOF facility. The setup takes advantage of the coincidence detection of both fission fragments to discriminate the background reactions produced by high energy neutrons and it allows obtaining neutron-induced fission cross section up to 1 GeV. (authors)

  15. Enabling the Use of Space Fission Propulsion Systems

    Microsoft Academic Search

    Mike Houts; Melissa Van Dyke; Tom Godfroy; James Martin; Kevin Pedersen; Ricky Dickens; Ivana Hrbud; Leo Bitteker; Bruce Patton; Suman Chakrabarti; Joe Bonometti

    2000-01-01

    This paper gives brief descriptions of advantages of fission technology for reaching any point in the solar system and of earlier efforts to develop space fission propulsion systems, and gives a more detailed description of the safe, affordable fission engine (SAFE) concept being pursued at the National Aeronautics and Space Administration's Marshall Space Flight Center.

  16. Phase 1 space fission propulsion system testing and development progress

    Microsoft Academic Search

    Melissa van Dyke; Mike Houts; Kevin Pedersen; Tom Godfroy; Ricky Dickens; David Poston; Bob Reid; Pat Salvail; Peter Ring

    2001-01-01

    Successful development of space fission systems will require an extensive program of affordable and realistic testing. In addition to tests related to design\\/development of the fission system, realistic testing of the actual flight unit must also be performed. Testing can be divided into two categories, non-nuclear tests and nuclear tests. Full power nuclear tests of space fission systems are expensive,

  17. ON LOW-ENERGY FISSION OF ODD NUCLEI K. DIETRICH

    E-print Network

    Boyer, Edmond

    -dimensional barrier V(0153), i.e. the fission coordinate a is not coupled to other degrees of freedom. In reference [3435 ON LOW-ENERGY FISSION OF ODD NUCLEI K. DIETRICH Physik-Department der Technischen Universität.F.A. (reçu le 30 octobre 1975, accepté le 12 janvier 1976) Résumé. 2014 On donne une théorie de la fission

  18. Options for development of space fission propulsion systems

    Microsoft Academic Search

    Mike Houts; Melissa van Dyke; Tom Godfroy; Kevin Pedersen; James Martin; Ricky Dickens; Pat Salvail; Ivana Hrbud

    2001-01-01

    Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include high specific power continuous impulse propulsion systems and bimodal nuclear thermal rockets. Despite their tremendous potential for enhancing or enabling deep space and planetary missions, to date space fission systems have only been used in Earth orbit. The first step towards

  19. Enabling the Use of Space Fission Propulsion Systems

    SciTech Connect

    Mike Houts; Melissa Van Dyke; Tom Godfroy; James Martin; Kevin Pedersen; Ricky Dickens; Ivana Hrbud; Leo Bitteker; Bruce Patton; Suman Chakrabarti; Joe Bonometti

    2000-06-04

    This paper gives brief descriptions of advantages of fission technology for reaching any point in the solar system and of earlier efforts to develop space fission propulsion systems, and gives a more detailed description of the safe, affordable fission engine (SAFE) concept being pursued at the National Aeronautics and Space Administration's Marshall Space Flight Center.

  20. Fission of Entangled Spins: An Electronic Structure Perspective Xintian Feng,

    E-print Network

    Krylov, Anna I.

    61001, Ukraine *S Supporting Information ABSTRACT: Electronic structure aspects of singlet fission of singlet fission are explained. Based on the Cauchy-Schwarz inequality, we propose using the norm of one, and Excited States Singlet fission (SF), a process in which one singlet excited state splits into two triplets

  1. Boolean Network Model Predicts Cell Cycle Sequence of Fission Yeast

    E-print Network

    Bornholdt, Stefan

    Boolean Network Model Predicts Cell Cycle Sequence of Fission Yeast Maria I. Davidich, Stefan network model of the cell-cycle regulatory network of fission yeast (Schizosaccharomyces Pombe sequence being a strongly attractive trajectory. Comparing the fission yeast cell-cycle model to a similar

  2. SPIDER Progress Towards High Resolution Correlated Fission Product Data

    NASA Astrophysics Data System (ADS)

    Shields, Dan; Meierbachtol, Krista; Tovesson, Fredrik; Arnold, Charles; Blackeley, Rick; Bredeweg, Todd; Devlin, Matt; Hecht, Adam; Jandel, Marian; Jorgenson, Justin; Nelson, Ron; White, Morgan; Spider Team

    2014-09-01

    The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (?), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. The SPIDER detector (SPectrometer for Ion DEtermination in fission Research) is under development with the goal of obtaining high-resolution, high-efficiency, correlated fission product data needed for many applications including the modeling of next generation nuclear reactors, stockpile stewardship, and the fundamental understanding of the fission process. SPIDER simultaneously measures velocity and energy of both fission products to calculate fission product yields (FPYs), neutron multiplicity (?), and total kinetic energy (TKE). A detailed description of the prototype SPIDER detector components will be presented. Characterization measurements with alpha and spontaneous fission sources will also be discussed. LA-UR-14-24875. This work is in part supported by LANL Laboratory Directed Research and Development Projects 20110037DR and 20120077DR.

  3. Mass distribution of fission products following photofission of uranium-238

    Microsoft Academic Search

    D. Swindle; R. Wright; K. Takahashi; W. H. Rivera; J. L. Meason

    1973-01-01

    The mass-yield distribution of fission products following photofission ; of ²³⁸U using bremsstrahlung energies of 22, 24, and 28 MeV were measured ; by radiochemically isolating the fission products belonging to 24 mass chains. ; The absolute activities of these nuclides were determined by BETA - and gamma ; counting techniques, and the cumulative fission yields were calculated relative ;

  4. Database and Map of Quaternary Faults and Folds in Peru and its Offshore Region

    USGS Publications Warehouse

    Machare, Jose; Fenton, Clark H.; Machette, Michael N.; Lavenu, Alain; Costa, Carlos; Dart, Richard L.

    2003-01-01

    This publication consists of a main map of Quaternary faults and fiolds of Peru, a table of Quaternary fault data, a region inset map showing relative plate motion, and a second inset map of an enlarged area of interest in southern Peru. These maps and data compilation show evidence for activity of Quaternary faults and folds in Peru and its offshore regions of the Pacific Ocean. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. These data are accompanied by text databases that describe these features and document current information on their activity in the Quaternary.

  5. Quaternary ammonium salts and lubricating oil containing said salts as dispersants

    SciTech Connect

    Chafetz, H.; Lee, G. D.

    1981-02-03

    Quaternary ammonium salts prepared by reacting an alkenylsuccinimide with a monocarboxylic acid ester provide improved dispersancy in lubricating oils, as compared with the starting alkenylsuccinimides.

  6. Polycationic antimicrobial dendrimers: a comparison of alkyl pyridinium,quaternary ammonium, quaternary phosphonium and tertiary sulfonium salts

    NASA Astrophysics Data System (ADS)

    Chen, Chris; Cooper, Stuart

    2000-03-01

    Polycationic biocides usually kill bacteria through the interactions of the positively charged head groups with negatively charged bacteria and the interactions of the hydrophobic segments with phospholipid cell membranes, which implies that high local charge densities and a large number of hydrophobic groups would lead to enhanced biocidal potency. The advent of dendrimers offers us the first-ever opportunity to achieve the desired high local density. We have demonstrated that dimethyl dodecyl ammonium chloride functionalized polypropylene imine dendrimers are over 100 times more potent than their small molecule ounterparts. In this study, quaternary ammonium, quaternary phosphonium, alkyl pyridinium and tertiary sulfonium salts based on polypropylene imine dendrimers have been synthesized and characterized. Their antimicrobial properties have been quantified with a novel bioluminescence method. The structure-activity relationship of these polycationic dendrimers has also been investigated to elucidate the molecular mechanism for the enhanced antimicrobial effects.

  7. Quaternary extension in southern Tibet: Field observations and tectonic implications

    NASA Astrophysics Data System (ADS)

    Armijo, Rolando; Tapponnier, Paul; Mercier, J. L.; Han, Tong-Lin

    1986-12-01

    We summarize evidence for Quaternary and active faulting collected in the field during three Sino-French expeditions to southeastern Tibet (1980-1982). Detailed mapping of Quaternary and active faults as well as microtectonic measurements indicate that normal faulting has been the dominant tectonic regime north of the Himalayas in the last 2 ± 0.5 m.y. The maximum horizontal principal stress in south Tibet appears to be only the intermediate principal stress ?2, ?1 being vertical. South of the "chord" joining the eastern and western syntaxes of the Himalayan arc, extensional strains are principally localized within seven regularly spaced rift zones, three of which have been studied in some detail. The extension direction is determined to be N96° E ± 7° mainly from statistical averaging of strikes of newly formed normal faults. Throw rates on normal faults are evaluated for different time spans (2 ± 0.5 m.y., 60 ± 40 kyr, and 10 ± 2 kyr B.P.), using structural and topographic reliefs, as well as synglacial and postglacial vertical offsets. The rate of Quaternary extension is about 1% m.y.-1 along an 1100-km-long ESE traverse across south Tibet. This corresponds to a "spreading" rate of 1 ± 0.6 cm/yr. This rate and the divergent horizontal projections of slip vectors of earthquakes along the Himalayan front constrain the rate at which rigid India underthrusts southern Tibet to be 2 ± 1 cm/yr. Although most of the normal faults appear to be independent of, and nearly orthogonal to, the ?E-W Mesozoic-Tertiary tectonic fabric, the Yadong-Gulu rift appears to be guided for over 130 km by the older, oblique (?NE-SW) Nyainqentanglha range and fault zones along it. This reactivated zone is the most prominent left-lateral strike-slip fault system in SE Tibet. Excepting this zone, and the vicinity of the SE extremity of the Karakorum fault, Quaternary strike-slip faulting is rare in south Tibet, i.e., south of the chord between the syntaxes of the Himalayan arc. North of the chord, the tectonic style is different. There minor conjugate strike-slip faulting is widespread and appears to control Quaternary normal faulting, which is more diffuse and subdued than in south Tibet. Along the chord, the presence of a major zone of active right-lateral, en échelon strike-slip faults (Karakorum-Jiali fault zone) probably reflects the greater facility of eastward extrusion in north central Tibet, in response to the northward push of India. The eastern Himalayan syntaxis may be an obstacle to such extrusion movements south of the chord.

  8. Quaternary coastal evolution of Oman (Arabian Peninsula) - a quantitative approach

    NASA Astrophysics Data System (ADS)

    Hoffmann, G.; Rupprechter, M.; Roepert, A.; Quraishi, K. Al; Balushi, N. Al; Grützner, C.; Reicherter, K.

    2012-04-01

    The paper reviews the Quaternary coastal evolution of Oman. Emphasise is put on quantifying the different forcing factors. The plate tectonic setting, the Quaternary climate evolution, the sea-level history and the impact of natural hazards are identified as key factors of coastal evolution. The Arabian Plate is characterized by a northward movement forming a continent-continent collision zone in the west and the Makran Subduction Zone in the east. As a result differential land movement is observable in Oman. The Quaternary climate evolution is well understood. Besides other proxies notably spelothems and aeolian deposits allow to draw a consistent picture. It is understood that changes in the position of the intertropical convergence zone result in intensity-changes of the summer monsoon. These changes are related to global atmospheric circulation patterns. Data on the sea-level history are sparse; despite general assumptions of a sea-level lowstand, correlating with the last glacial maximum, resulting in terrestrial conditions within the Arabian Gulf. Furthermore, a mid-Holocene sea level highstand in the range of +2m is documented in several locations. The coastlines of Oman are affected by tsunami and hurricanes. However, almost no instrumental or historical data on the impact of such natural hazards are available due to the isolation of the country in the past. Several Quaternary deposits have been investigated in a reconnaissance survey. There is sound geological evidence for a tsunami to have affected the coastline in 1945, with the possibility of older tsunami events being also recorded in the geological record. There is strong evidence of differential land movement along the coastline; locally indicated by marine terraces in elevations of up to 400m (Rupprechter at al. 2012). By quantifying the differential land movement for numerous sites, the sea-level history will be revealed. Ultimately the data will be utilized to form the base of a modeling approach. Furthermore, a sedimentary archive of past precipitation events is documented which will allow reconstructing frequency and intensity of precipitation events and may indicate the impact of past hurricanes. It is concluded that the geological archives are suitable to quantify the forcing factors of Quaternary coastal evolution on different time scales and that the recurrence intervals of natural hazards will be revealed. Proxy data will be gained in subsequent investigations. This allows a scientific based holistic approach for an integrated coastal zone management that helps to formulate adaptation strategies with regard to global warming and expected environmental changes.

  9. Fission barriers and probabilities of spontaneous fission for elements with Z$\\geq$100

    E-print Network

    A. Baran; M. Kowal; P. -G. Reinhard; L. M. Robledo; A. Staszczak; M. Warda

    2015-03-05

    This is a short review of methods and results of calculations of fission barriers and fission half-lives of even-even superheavy nuclei. An approvable agreement of the following approaches is shown and discussed: The macroscopic-microscopic approach based on the stratagem of the shell correction to the liquid drop model and a vantage point of microscopic energy density functionals of Skyrme and Gogny type selfconsistently calculated within Hartree-Fock-Bogoliubov method. Mass parameters are calculated in the Hartree-Fock-Bogoliubov cranking approximation. A short part of the paper is devoted to the nuclear fission dynamics. We also discuss the predictive power of Skyrme functionals applied to key properties of the fission path of $^{266}$Hs. It applies the standard techniques of error estimates in the framework of a $\\chi^2$ analysis.

  10. Fission barriers and probabilities of spontaneous fission for elements with Z$\\geq$100

    E-print Network

    Baran, A; Reinhard, P -G; Robledo, L M; Staszczak, A; Warda, M

    2015-01-01

    This is a short review of methods and results of calculations of fission barriers and fission half-lives of even-even superheavy nuclei. An approvable agreement of the following approaches is shown and discussed: The macroscopic-microscopic approach based on the stratagem of the shell correction to the liquid drop model and a vantage point of microscopic energy density functionals of Skyrme and Gogny type selfconsistently calculated within Hartree-Fock-Bogoliubov method. Mass parameters are calculated in the Hartree-Fock-Bogoliubov cranking approximation. A short part of the paper is devoted to the nuclear fission dynamics. We also discuss the predictive power of Skyrme functionals applied to key properties of the fission path of $^{266}$Hs. It applies the standard techniques of error estimates in the framework of a $\\chi^2$ analysis.

  11. Fission Dynamics in the Proton Induced Fission of Actinide Nuclei at Intermediate Energies

    SciTech Connect

    Kozulin, E. M.; Bogachev, A. A.; Itkis, M. G.; Kliman, J.; Knyazheva, G. N.; Krupa, L. [Flerov Laboratory of Nuclear Reactions, JINR, 141980 Dubna (Russian Federation); Aeystoe, J.; Iamaletdinov, S.; Lyapin, V.; Mutterer, M.; Rubchenya, V. A.; Sillanpaeae, M. O.; Trzaska, W. H. [Department of Physics, University of Jyvaeskylae, FIN-40351, Jyvaeskylae (Finland); Hanappe, F. [Universite Libre de Bruxelles, 1050 Brussels (Belgium); Dorvaux, O. [Institut de Recherches Subatomiques, F-67037 Strasbourg Cedex (France); Khlebnikov, S. V. [Khlopin Radium Institute, 194021, St.-Petersburg (Russian Federation); Vardaci, E. [INFN, Dipartimento di Scienze Fisiche, Sezione di Napoli, I-180125, Naples (Italy)

    2006-08-14

    A multi-parameter correlation study of the reactions 232Th(p,f), 238U(p,f) and 242Pu(p,f) at Ep=13, 20, 40 and 55 MeV has been conducted. The fission fragment mass, total kinetic energy distributions, double differential neutron spectra and {gamma}-ray spectra have been measured. The three humped shape of mass distributions has been observed up to higher proton energy. Pre-equilibrium, pre-scission and post-scission neutron and {gamma}-ray multiplicities measured in coincidence with primary fission fragments provided access to fission dynamics. Shell structure effects were observed in fission fragment mass distributions even at high excitation energy. Manifestation of the nuclear shell Z = 28 near fragment mass Afr = 78 has been detected.

  12. Fission neutron output measurements at LANSCE

    SciTech Connect

    Nelson, Ronald Owen [Los Alamos National Laboratory; Haight, Robert C [Los Alamos National Laboratory; Devlin, Matthew J [Los Alamos National Laboratory; Fotiadis, Nikolaos [Los Alamos National Laboratory; Laptev, Alexander [Los Alamos National Laboratory; O' Donnell, John M [Los Alamos National Laboratory; Taddeucci, Terry N [Los Alamos National Laboratory; Tovesson, Fredrik [Los Alamos National Laboratory; Ullmann, J L [Los Alamos National Laboratory; Wender, Stephen A [Los Alamos National Laboratory; Bredeweg, T A [Los Alamos National Laboratory; Jandel, M [Los Alamos National Laboratory; Vieira, D J [Los Alamos National Laboratory; Wu, Ching - Yen [LLNL; Becker, J A [LLNL; Stoyer, M A [LLNL; Henderson, R [LLNL; Sutton, M [LLNL; Belier, Gilbert [BRUYERES-LE-CHATEL, FRANCE; Chatillon, A [BRUYERES-LE-CHATEL, FRANCE; Granier, Thierry [CEA, BRUYERES-LE-CHATEL, FRANCE; Laurent, Benoit [CEA, BRUYERES-LE-CHATEL, FRANCE; Taieb, Julien [CEA, BRUYERES-LE-CHATEL, FRANCE

    2010-01-01

    Accurate data for both physical properties and fission properties of materials are necessary to properly model dynamic fissioning systems. To address the need for accurate data on fission neutron energy spectra, especially at outgoing neutron energies below about 200 keV and at energies above 8 MeV, ongoing work at LANSCE involving collaborators from LANL, LLNL and CEA Bruyeres-le-Chatel is extending the energy range, efficiency and accuracy beyond previous measurements. Initial work in the outgoing neutron energy range from 1 to 7 MeV is consistent with current evaluations and provides a foundation for extended measurements. As part of these efforts, a new fission fragment detector that reduces backgrounds and improves timing has been designed fabricated and tested, and new neutron detectors are being assessed for optimal characteristics. Simulations of experimental designs are in progress to ensure that accuracy goals are met. Results of these measurements will be incorporated into evaluations and data libraries as they become available.

  13. Transfer-induced fission of superheavy nuclei

    SciTech Connect

    Adamian, G. G. [Joint Institute for Nuclear Research, RU-141980 Dubna (Russian Federation); Institute of Nuclear Physics, Tashkent, UZ-702132 Uzbekistan (Uzbekistan); Antonenko, N. V.; Zubov, A. S. [Joint Institute for Nuclear Research, RU-141980 Dubna (Russian Federation); Sargsyan, V. V. [Joint Institute for Nuclear Research, RU-141980 Dubna (Russian Federation); Yerevan State University, Yerevan (Armenia); Scheid, W. [Institut fuer Theoretische Physik der Justus-Liebig-Universitaet, D-35392 Giessen (Germany)

    2010-07-15

    Possibilities of transfer-induced fission of new isotopes of superheavy nuclei with charge numbers 103-108 are studied for the first time in the reactions {sup 48}Ca+{sup 244,246,248}Cm at energies near the corresponding Coulomb barriers. The predicted cross sections are found to be measurable with the detection of three-body final states.

  14. Fission Barriers of Compound Superheavy Nuclei

    SciTech Connect

    Pei, Junchen [ORNL; Nazarewicz, Witold [ORNL; Sheikh, J. A. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Kerman, A. K. [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)

    2009-01-01

    The dependence of fission barriers on the excitation energy of the compound nucleus impacts the survival probability of superheavy nuclei synthesized in heavy-ion fusion reactions. We study the temperature-dependent fission barriers by means of the self-consistent nuclear density functional theory. The equivalence of isothermal and isentropic descriptions is demonstrated. The effect of the particle gas is found to be negligible in the range of temperatures studied. Calculations have been carried out for ^{264}Fm, ^{272}Ds, ^{278}112, ^{292}114, and ^{312}124. For nuclei around ^{278}112 produced in "cold fusion" reactions, we predict a more rapid decrease of fission barriers with temperature as compared to the nuclei around ^{292}114 synthesized in "hot fusion" experiments. This is explained in terms of the difference between the ground-state and fission-barrier temperatures. Our calculations are consistent with the long survival probabilities of the superheavy elements produced in Dubna with the ^{48}Ca beam.

  15. THE DELAYED NEUTRON PRECURSORS IN FISSION

    Microsoft Academic Search

    1959-01-01

    A survey of the experimental data on delayed neutron half lives and ; yields gives indication for the existence of a greater number of delayed neutron ; precursors than the six commonly accepted. This finds further support in the ; fact that the ratio of delayed neutron yield to cumulative fission yield of a ; delayed neutron precursor depends on

  16. Fifty years with nuclear fission. Volume 2

    Microsoft Academic Search

    J. W. Behrens; A. D. Carlson

    1989-01-01

    The news of the discovery of nucler fission, by Otto Hahn and Fritz Strassmann in Germany, was brought to the United States by Niels Bohr in January 1939. Since its discovery, the United States, and the world for that matter, has never been the same. It therefore seemed appropriate to acknowledge the fiftieth anniversary of its discovery by holding a

  17. Factors influencing audiovisual fission and fusion illusions

    Microsoft Academic Search

    Tobias S. Andersen; Kaisa Tiippana; Mikko Sams

    2004-01-01

    Information processing in auditory and visual modalities interacts in many circumstances. Spatially and temporally coincident acoustic and visual information are often bound together to form multisensory percepts [B.E. Stein, M.A. Meredith, The Merging of the Senses, A Bradford Book, Cambridge, MA, (1993), 211 pp.; Psychol. Bull. 88 (1980) 638]. Shams et al. recently reported a multisensory fission illusion where a

  18. Fission Detection Using the Associated Particle Technique

    SciTech Connect

    R.P. Keegan, J.P. Hurley, J.R. Tinsley, R. Trainham, S.C. Wilde

    2008-09-18

    A beam of tagged 14 MeV neutrons from the deuterium-tritium (DT) reaction is used to induce fission in a target composed of depleted uranium. The generator yield is 107 neutrons/second radiated into a 4? solid angle. Two 4 in.×4 in. NaI detectors are used for gamma-ray detection. The fission process is known to produce multiple gamma-rays and neutrons. Triple coincidences (?-?-?) are measured as a function of neutron flight time up to 90 ns after fission, where the ?-particle arises from the DT reaction. A sudden increase in the triple coincidence rate at the location of the material is used to localize and detect fission in the interrogated target. Comparisons are made with experiment runs where lead, tungsten, and iron were used as target materials. The triple coincidence response profile from depleted uranium is noted to be different to those observed from the other target materials. The response from interrogation targets composed of fissile material is anticipated to be even more unique than that observed from depleted uranium.

  19. Space parity violation in nuclear fission

    Microsoft Academic Search

    G. A. Petrov; G. V. Valskii; A. K. Petukhov; A. Ya. Alexandrovich; Yu. S. Pleva; V. E. Sokolov; A. B. Laptev; O. A. Scherbakov

    1989-01-01

    Experimental results of systematic studies of the space parity violation effect in heavy nucleus fission induced by transversally polarized monochromatic neutrons with the energies less then ~ 2 eV have been presented. Modern explanations of the results obtained and perspectives of the further investigations are discussed.

  20. Fission in intermediate energy heavy ion reactions

    SciTech Connect

    Wilhelmy, J.B.; Begemann-Blaich, M.; Blaich, T.; Boissevain, J.; Fowler, M.M.; Gavron, A.; Jacak, B.V.; Lysaght, P.S.; Britt, H.C.; Fields, D.J.

    1989-04-01

    A systematic study of reaction mechanisms at intermediate energies (50--100 MeV/A) has been performed at the Lawrence Berkeley Laboratory's BeValac using medium weight projectiles on medium and heavy element targets. A gas and plastic phoswich detector system was employed which gave large geometric coverage and a wide dynamic response. The particles identified with the gas detectors could be characterized into three components--intermediate mass fragments (IMF), fission fragments (FF) and heavy residues (HR). Major observed features are: the reaction yields are similar in the 50 to 100 MeV/A range, central collisions have high multiplicity of IMF's with broad angular correlations consistent with a large participant region, effects of final state Coulomb interactions are observed and give information on the size and temporal behavior of the source, true fission yields are dependent on target fissility and correlated with relatively peripheral collisions. Analysis of fission and evaporation yields implies limiting conditions for which fission decay remains a viable deexcitation channel. 15 refs., 7 figs.

  1. Search for other natural fission reactors

    Microsoft Academic Search

    K. E. Apt; J. P. Balagna; E. A. Bryant; G. A. Cowan; W. R. Daniels; R. J. Vidale

    1977-01-01

    Precambrian uranium ores have been surveyed for evidence of other natural fission reactors. The requirements for formation of a natural reactor direct investigations to uranium deposits with large, high-grade ore zones. Massive zones with volumes approximately greater than 1 m³ and concentrations approximately greater than 20 percent uranium are likely places for a fossil reactor if they are approximately greater

  2. Fission-fragment gamma-ray multiplicities

    SciTech Connect

    Hook, D.E.

    1987-01-01

    The gamma ray multiplicity (M{gamma}) of fission fragments is a valuable experimental clue to the physics of the fission process in particular and the dynamics of heavy-ion collisions in general. Apparatus for measuring M{gamma} as a function of mass asymmetry was constructed and commissioned. The apparatus consisted of a time-of-flight telescope with a time resolution for fission fragments of {approx}1.5 ns and a solid angle of some 0.04 strad. The telescope was constructed using a micro-channel plate start detector and a parallel plate avalanche counter as a stop detector. Gamma rays from the fragments were detected in an array of three 5{double prime} {times} 6{double prime} NaI(Tl) detectors placed approximately 55 cm from the target. When used in beam this apparatus provided sufficient mass resolution for the detected fission fragments and allowed excellent separation of the {gamma}-rays and neutrons from the reaction on the basis of their time-of-flight.

  3. Angular-momentum-bearing modes in fission

    SciTech Connect

    Moretto, L.G.; Peaslee, G.F.; Wozniak, G.J.

    1989-03-01

    The angular-momentum-bearing degrees of freedom involved in the fission process are identified and their influence on experimental observables is discussed. The excitation of these modes is treated in the ''thermal'' limit, and the resulting distributions of observables are calculated. Experiments demonstrating the role of these modes are presented and discussed. 61 refs., 12 figs.

  4. Energy dependence of optically induced exciton fission

    Microsoft Academic Search

    C. E. Swenberg; M. A. Ratner; N. E. Geacintov

    1974-01-01

    A general discussion of the kinematics of optically induced fission in organic crystals is presented. Explanations are given for the nonoccurrence of this phenomenon in certain systems, and a theoretical interpretation is offered for the photon energy dependence of the magnetic field effect on the prompt fluorescence of solid tetracene at 77°K. The structure observed by Moller and Pope below

  5. Singlet exciton fission in a hexacene derivative.

    PubMed

    Lee, Jiye; Bruzek, Matthew J; Thompson, Nicholas J; Sfeir, Matthew Y; Anthony, John E; Baldo, Marc A

    2013-03-13

    Hexacene, an acene with six benzene rings, is notable for its exceptionally small triplet energy, around one third of the singlet energy. Herein, singlet fission, i.e., conversion of a singlet exciton into two triplets, is demonstrated in a thin film of hexacene derivative, employing both transient absorption spectroscopy and magnetic field effects on photocurrent. PMID:23293054

  6. DIFFUSION OF FISSION GAS IN URANIUM

    Microsoft Academic Search

    1963-01-01

    The diffusion coefficient and activation energy for diffusion of xenon-; 133 in uranium metal have been determined for a number of varying sample ; conditions, with metal of hlgh purity and commercial purity. Thin foil samples ; were neutron irradiated, in groups, under conditions such as to produce optimum ; uniformity of fission product concentration throughout the samples. The samples

  7. Nondestructive fission gas release measurement and analysis

    Microsoft Academic Search

    P. M. OLeary; D. R. Packard

    1993-01-01

    Siemens Power Corporation (SPC) has performed reactor poolside gamma scanning measurements of fuel rods for fission gas release (FGR) detection for more than 10 yr. The measurement system has been previously described. Over the years, the data acquisition system, the method of spectrum analysis, and the means of reducing spectrum interference have been significantly improved. A personal computer (PC)-based multichannel

  8. Interstellar rendezvous missions employing fission propulsion systems

    Microsoft Academic Search

    Roger X. Lenard; Ronald J. Lipinski

    2000-01-01

    There has been a conventionally held nostrum that fission system specific power and energy content is insufficient to provide the requisite high accelerations and velocities to enable interstellar rendezvous missions within a reasonable fraction of a human lifetime. As a consequence, all forms of alternative mechanisms that are not yet, and may never be technologically feasible, have been proposed, including

  9. Propagation of a constant velocity fission wave

    NASA Astrophysics Data System (ADS)

    Deinert, Mark

    2011-10-01

    The ideal nuclear fuel cycle would require no enrichment, minimize the need fresh uranium, and produce few, if any, transuranic elements. Importantly, the latter goal would be met without the reprocessing. For purely physical reasons, no reactor system or fuel cycle can meet all of these objectives. However, a traveling-wave reactor, if feasible, could come remarkably close. The concept is simple: a large cylinder of natural (or depleted) uranium is subjected to a fast neutron source at one end, the neutrons would transmute the uranium downstream and produce plutonium. If the conditions were right, a self-sustaining fission wave would form, producing yet more neutrons which would breed more plutonium and leave behind little more than short-lived fission products. Numerical studies have shown that fission waves of this type are also possible. We have derived an exact solution for the propagation velocity of a fission wave through fertile material. The results show that these waves fall into a class of traveling wave phenomena that have been encountered in other systems. The solution places a strict conditions on the shapes of the flux, diffusive, and reactive profiles that would be required for such a phenomenon to persist. The results are confirmed numerically.

  10. Energy distributions of fission fragments of preactinides and the hypothesisof independent fission modes

    SciTech Connect

    Itkis, M.G.; Okolovich, V.; Rusanov, A.Y.; Smirenkin, G.N.

    1985-05-01

    Experimental information is studied concerning the mass-energy distributions of fission fragments from preactinide nuclei from /sup 210/Tl to /sup 213/At. The dependence of the first and second moments of the fragment kinetic-energy distributions E/sub k/(M) and sigma/sup 2//sub E//sub k/(M) upon the excitation energy and nucleon content of the nuclei is analyzed. The two-fission-mode hypothesis is justified and its applicability range is found.

  11. Fission-fragment kinetic energy and mass distributions for /sup 252/Cf spontaneous fission

    SciTech Connect

    Bao, Z.; Han, H.; Meng, J.; Huang, S.

    1983-01-01

    Fission-fragment kinetic energy and mass distributions for /sup 252/Cf spontaneous fission were obtained by correlation energy measurements using gold-silicon surface-barrier detectors. The results show that two pronounced shoulders exist on the mass distribution curves in the total kinetic energy region between 200--216 MeV. Each curve might be considered as composed of three components with the peaks located at about 107, 112, and 118 amu.

  12. Insights into nuclear structure and the fission process from spontaneous fission

    SciTech Connect

    Hamilton, J.H.; Butler-Moore, K.; Ramayya, A.V. [Vanderbilt Univ., Nashville, TN (United States)] [and others

    1993-12-31

    The {gamma}-rays emitted following spontaneous and induced fission are rich sources of information about the structure of neutron-rich nuclei and about the fission process itself. The study of spontaneous fissioning isotopes with large Ge detector arrays are providing a wealth of such information as seen, for example, in recent reports. In this paper we present some of our most recent results on nuclear structure studies and conclusions on the fission process itself. In our work, we have employed in spontaneous fission, a triple gamma coincidence study for the first time and a high resolution, X-ray detector-{gamma}-coincidence study. These data provide powerful ways of separating the gamma rays which belong to a particular nucleus. The triple coincidence technique was used to uniquely identify the levels in {sup 136}Te and higher spin states in its N=84 isotones, {sup 138}Xe and {sup 140}Ba{sup 171}. Some other examples of the level structures observed in the low and high mass partners are presented, including a detailed analysis of the backbending of the moment of inertia in {sup 112,114,116}Pd. Finally, we present the first examples of how our analysis allows one to extract a detailed picture of the dependence of the angular momentum on the mass and atomic numbers of the fission fragments and of the long-sought neutron multiplicity distribution from zero-n to ten-n as a function of the charge and mass asymmetry.

  13. Fission Reaction Event Yield Algorithm, FREYA - For event-by-event simulation of fission

    NASA Astrophysics Data System (ADS)

    Verbeke, J. M.; Randrup, J.; Vogt, R.

    2015-06-01

    From nuclear materials accountability to detection of special nuclear material, SNM, the need for better modeling of fission has grown over the past decades. Current radiation transport codes compute average quantities with great accuracy and performance, but performance and averaging come at the price of limited interaction-by-interaction modeling. For fission applications, these codes often lack the capability of modeling interactions exactly: energy is not conserved, energies of emitted particles are uncorrelated, prompt fission neutron and photon multiplicities are uncorrelated. Many modern applications require more exclusive quantities than averages, such as the fluctuations in certain observables (e.g. the neutron multiplicity) and correlations between neutrons and photons. The new computational model, FREYA (Fission Reaction Event Yield Algorithm), aims to meet this need by modeling complete fission events. Thus it automatically includes fluctuations as well as correlations resulting from conservation of energy and momentum. FREYA has been integrated into the LLNL Fission Library, and will soon be part of MCNPX2.7.0, MCNP6, TRIPOLI-4.9, and Geant4.10.

  14. The behavior of fission products during nuclear rocket reactor tests

    SciTech Connect

    Bokor, P.C.; Kirk, W.L.; Bohl, R.J. (Los Alamos National Laboratory, MS E550, Los Alamos, New Mexico (USA))

    1991-01-10

    Fission product release from nuclear rocket propulsion reactor fuel is an important consideration for nuclear rocket development and application. Fission product data from the last six reactors of the Rover program are collected in this paper to provide as basis for addressing development and testing issues. Fission product loss from the fuel will depend on fuel composition and reactor design and operating parameters. During ground testing, fission products can be contained downstream of the reactor. The last Rover reactor tested, the Nuclear Furnance, was mated to an effluent clean-up system that was effective in preventing the discharge of fission products into the atmosphere.

  15. Rapid separation of fresh fission products (draft)

    SciTech Connect

    Dry, D. E. (Donald E.); Bauer, E. (Eve); Petersen, L. A. (Lisa A.)

    2003-01-01

    The fission of highly eruiched uranium by thermal neutrons creates dozens of isotopic products. The Isotope and Nuclear Chemistry Group participates in programs that involve analysis of 'fiesh' fission products by beta counting following radiochemical separations. This is a laborious and time-consuming process that can take several days to generate results. Gamma spectroscopy can provide a more immediate path to isolopic activities, however short-lived, high-yield isotopes can swamp a gamma spectrum, making difficult the identification and quantification of isotopes on the wings and valley of the fission yield curve. The gamma spectrum of a sample of newly produced fission products is dominated by the many emissions of a very few high-yield isotopes. Specilkally, {sup 132}Te (3.2 d), its daughter, {sup 132}I(2 .28 h), {sup 140}Ba (12.75 d), and its daughter {sup 140}La (1.68 d) emit at least 18 gamma rays above 100 keV that are greater than 5% abundance. Additionally, the 1596 keV emission fiom I4'La imposes a Compton background that hinders the detection of isotopes that are neither subject to matrix dependent fractionation nor gaseous or volatile recursors. Some of these isotopes of interest are {sup 111}Ag, {sup 115}Cd, and the rare earths, {sup 153}Sm, {sup 154}Eu, {sup 156}Eu, and {sup 160}Tb. C-INC has performed an HEU irradiation and also 'cold' carrier analyses by ICP-AES to determine methods for rapid and reliable separations that may be used to detect and quantify low-yield fission products by gamma spectroscopy. Results and progress will be presented.

  16. Fission track dating of kimberlitic zircons

    USGS Publications Warehouse

    Haggerty, S.E.; Raber, E.; Naeser, C.W.

    1983-01-01

    The only reliable method for dating kimberlites at present is the lengthy and specialized hydrothermal procedure that extracts 206Pb and 238U from low-uranium zircons. This paper describes a second successful method by fission track dating of large single-crystal zircons, 1.0-1.5 cm in dimension. The use of large crystals overcomes the limitations imposed in conventional fission track analysis which utilizes crushed fragments. Low track densities, optical track dispersion, and the random orientation of polished surfaces in the etch and irradiation cycle are effectively overcome. Fission track ages of zircons from five African kimberlites are reported, from the Kimberley Pool (90.3 ?? 6.5 m.y.), Orapa (87.4 ?? 5.7 and 92.4 ?? 6.1 m.y.), Nzega (51.1 ?? 3.8 m.y.), Koffiefontein (90.0 ?? 8.2 m.y.), and Val do Queve (133.4 ?? 11.5 m.y.). In addition we report the first radiometric ages (707.9 ?? 59.6 and 705.5 ?? 61.0 m.y.) of crustal zircons from kimberlites in northwest Liberia. The fission track ages agree well with earlier age estimates. Most of the zircons examined in this study are zoned with respect to uranium but linear correlations are established (by regression analysis) between zones of variable uranium content, and within zones of constant uranium content (by analysis of variance). Concordance between the fission track method and the U/Pb technique is established and we concluded that track fading from thermal annealing has not taken place. Kimberlitic zircons dated in this study, therefore, record the time of eruption. ?? 1983.

  17. A Novel Route to Recognizing Quaternary Ammonium Cations Using Electrospray Mass Spectrometry

    NASA Astrophysics Data System (ADS)

    Shackman, Holly M.; Ding, Wei; Bolgar, Mark S.

    2015-01-01

    Characterizing and elucidating structures is a commonplace and necessary activity in the pharmaceutical industry with mass spectrometry and NMR being the primary tools for analysis. Although many functional groups are readily identifiable, quaternary ammonium cations have proven to be difficult to unequivocally identify using these techniques. Due to the lack of an N-H bond, quaternary ammonium groups can only be detected in the 1H NMR spectra by weak signals generated from long-range 14N-H coupling, which by themselves are inconclusive evidence of a quaternary ammonium functional group. Due to their low intensity, these signals are frequently not detected. Additionally, ions cannot be differentiated in a mass spectrum as an M+ or [M + H]+ ion without prior knowledge of the compound's structure. In order to utilize mass spectrometry as a tool for determining this functionality, ion cluster formation of quaternary ammonium cations and non-quaternary amines was studied using electrospray ionization. Several mobile phase modifiers were compared; however, the addition of small amounts of trifluoroacetic acid proved superior in producing characteristic and intense [M +2TFA]- clusters for compounds containing quaternary ammonium cations when using negative electrospray. By fragmenting this characteristic ion using CID, nearly all compounds studied could be unambiguously identified as containing a quaternary ammonium cation or a non-quaternary amine attributable to the presence (non-quaternary amine) or absence (quaternary ammonium cation) of the resulting [2TFA + H]- ion in the product spectra. This method of analysis provides a rapid, novel, and reliable technique for indicating the presence of quaternary ammonium cations in order to aid in structural elucidation.

  18. A novel route to recognizing quaternary ammonium cations using electrospray mass spectrometry.

    PubMed

    Shackman, Holly M; Ding, Wei; Bolgar, Mark S

    2015-01-01

    Characterizing and elucidating structures is a commonplace and necessary activity in the pharmaceutical industry with mass spectrometry and NMR being the primary tools for analysis. Although many functional groups are readily identifiable, quaternary ammonium cations have proven to be difficult to unequivocally identify using these techniques. Due to the lack of an N-H bond, quaternary ammonium groups can only be detected in the (1)H NMR spectra by weak signals generated from long-range (14)N-H coupling, which by themselves are inconclusive evidence of a quaternary ammonium functional group. Due to their low intensity, these signals are frequently not detected. Additionally, ions cannot be differentiated in a mass spectrum as an M(+) or [M + H](+) ion without prior knowledge of the compound's structure. In order to utilize mass spectrometry as a tool for determining this functionality, ion cluster formation of quaternary ammonium cations and non-quaternary amines was studied using electrospray ionization. Several mobile phase modifiers were compared; however, the addition of small amounts of trifluoroacetic acid proved superior in producing characteristic and intense [M +2TFA](-) clusters for compounds containing quaternary ammonium cations when using negative electrospray. By fragmenting this characteristic ion using CID, nearly all compounds studied could be unambiguously identified as containing a quaternary ammonium cation or a non-quaternary amine attributable to the presence (non-quaternary amine) or absence (quaternary ammonium cation) of the resulting [2TFA + H](-) ion in the product spectra. This method of analysis provides a rapid, novel, and reliable technique for indicating the presence of quaternary ammonium cations in order to aid in structural elucidation. PMID:25391726

  19. Conservation of Isospin in Neutron-Rich Fission Fragments

    E-print Network

    Ashok Kumar Jain; Deepika Choudhury; Bhoomika Maheshwari

    2014-08-11

    On the occasion of the $75^{th}$ anniversary of the fission phenomenon, we present a surprisingly simple result which highlights the important role of isospin and its conservation in neutron rich fission fragments. We have analysed the fission fragment mass distribution from two recent heavy-ion reactions $^{238}$U($^{18}$O,f) and $^{208}$Pb($^{18}$O,f) as well as a thermal neutron fission reaction $^{245}$Cm(n$^{th}$,f). We find that the conservation of the total isospin explains the overall trend in the observed relative yields of fragment masses in each fission pair partition. The isospin values involved are very large making the effect dramatic. The findings open the way for more precise calculations of fission fragment distributions in heavy nuclei and may have far reaching consequences for the drip line nuclei, HI fusion reactions, and calculation of decay heat in the fission phenomenon.

  20. Fifty years of nuclear fission: Nuclear data and measurements series

    SciTech Connect

    Lynn, J.E.

    1989-06-01

    This report is the written version of a colloquium first presented at Argonne National Laboratory in January 1989. The paper begins with an historical preamble about the events leading to the discovery of nuclear fission. This leads naturally to an account of early results and understanding of the fission phenomena. Some of the key concepts in the development of fission theory are then discussed. The main theme of this discussion is the topography of the fission barrier, in which the interplay of the liquid-drop model and nucleon shell effects lead to a wide range of fascinating phenomena encompassing metastable isomers, intermediate-structure effects in fission cross-sections, and large changes in fission product properties. It is shown how study of these changing effects and theoretical calculations of the potential energy of the deformed nucleus have led to broad qualitative understanding of the nature of the fission process. 54 refs., 35 figs.

  1. Fission rate measurements in fuel plate type assembly reactor cores

    SciTech Connect

    Rogers, J.W.

    1988-01-01

    The methods, materials and equipment have been developed to allow extensive and precise measurement of fission rate distributions in water moderated, U-Al fuel plate assembly type reactor cores. Fission rate monitors are accurately positioned in the reactor core, the reactor is operated at a low power for a short time, the fission rate monitors are counted with detectors incorporating automated sample changers and the measurements are converted to fission rate distributions. These measured fission rate distributions have been successfully used as baseline information related to the operation of test and experimental reactors with respect to fission power and distribution, fuel loading and fission experiments for approximately twenty years at the Idaho National Engineering Laboratory (INEL). 7 refs., 8 figs.

  2. A transferable model for singlet-fission kinetics.

    PubMed

    Yost, Shane R; Lee, Jiye; Wilson, Mark W B; Wu, Tony; McMahon, David P; Parkhurst, Rebecca R; Thompson, Nicholas J; Congreve, Daniel N; Rao, Akshay; Johnson, Kerr; Sfeir, Matthew Y; Bawendi, Moungi G; Swager, Timothy M; Friend, Richard H; Baldo, Marc A; Van Voorhis, Troy

    2014-06-01

    Exciton fission is a process that occurs in certain organic materials whereby one singlet exciton splits into two independent triplets. In photovoltaic devices these two triplet excitons can each generate an electron, producing quantum yields per photon of >100% and potentially enabling single-junction power efficiencies above 40%. Here, we measure fission dynamics using ultrafast photoinduced absorption and present a first-principles expression that successfully reproduces the fission rate in materials with vastly different structures. Fission is non-adiabatic and Marcus-like in weakly interacting systems, becoming adiabatic and coupling-independent at larger interaction strengths. In neat films, we demonstrate fission yields near unity even when monomers are separated by >5 Å. For efficient solar cells, however, we show that fission must outcompete charge generation from the singlet exciton. This work lays the foundation for tailoring molecular properties like solubility and energy level alignment while maintaining the high fission yield required for photovoltaic applications. PMID:24848234

  3. A transferable model for singlet-fission kinetics

    NASA Astrophysics Data System (ADS)

    Yost, Shane R.; Lee, Jiye; Wilson, Mark W. B.; Wu, Tony; McMahon, David P.; Parkhurst, Rebecca R.; Thompson, Nicholas J.; Congreve, Daniel N.; Rao, Akshay; Johnson, Kerr; Sfeir, Matthew Y.; Bawendi, Moungi G.; Swager, Timothy M.; Friend, Richard H.; Baldo, Marc A.; van Voorhis, Troy

    2014-06-01

    Exciton fission is a process that occurs in certain organic materials whereby one singlet exciton splits into two independent triplets. In photovoltaic devices these two triplet excitons can each generate an electron, producing quantum yields per photon of >100% and potentially enabling single-junction power efficiencies above 40%. Here, we measure fission dynamics using ultrafast photoinduced absorption and present a first-principles expression that successfully reproduces the fission rate in materials with vastly different structures. Fission is non-adiabatic and Marcus-like in weakly interacting systems, becoming adiabatic and coupling-independent at larger interaction strengths. In neat films, we demonstrate fission yields near unity even when monomers are separated by >5 Å. For efficient solar cells, however, we show that fission must outcompete charge generation from the singlet exciton. This work lays the foundation for tailoring molecular properties like solubility and energy level alignment while maintaining the high fission yield required for photovoltaic applications.

  4. Distribution of Prompt Neutron Emission Probability for Fission Fragments in Spontaneous Fission of 252Cf and 244,248Cm

    SciTech Connect

    Vorobyev, A.S.; Shcherbakov, O.A. [Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, 188300 (Russian Federation); Dushin, V.N.; Jakovlev, V.A.; Kalinin, V.A.; Petrov, B.F. [V.G. Khlopin Radium Institute, St. Petersburg, 194021 (Russian Federation); Hambsch, F.-J. [EC-JRC-Institute for Reference Materials and Measurements Retieseweg 111, B-2440, Geel (Belgium); Laptev, A.B. [Petersburg Nuclear Physics Institute, Gatchina, Leningrad district, 188300 (Russian Federation); Japan Nuclear Cycle Development Institute, Tokai-mura, Naka-gun, Ibaraki, 319-1194 (Japan)

    2005-05-24

    Neutrons emitted in fission events were measured separately for each complementary fragment in correlation with fission fragment energies. Two high-efficiency Gd-loaded liquid scintillator tanks were used for neutron registration. Fission fragment energies were measured using a twin Frisch gridded ionization chamber with a pinhole collimator. The neutron multiplicity distributions were obtained for each value of the fission fragment mass and energy and corrected for neutron registration efficiency, background, and pile-up. The dependency of these distributions on fragment mass and energy for different energy and mass bins as well as mass and energy distribution of fission fragments are presented and discussed.

  5. A comparison of lignin and stable carbon isotope compositions in quaternary marine sediments

    Microsoft Academic Search

    JOHN I. HEDGES; ALEXANDER VAN GEEN

    1982-01-01

    Heges, J.I. and van Geen, A., 1982. A comparison of lignin and stable carbon isotope compositions in quaternary marine sediments. Mar. Chem., 11: 43--53. Organic matter in four Quaternary sediment cores from the Gulf of Mexico and one core from the Washington State coast have been analyzed for lignin and stable carbon isotope compositions. Holocene sequences of all five cores

  6. 182 28th ANNUAL eMS Sorption and Desorption of Quaternary Amine Cations on Clays

    E-print Network

    Sparks, Donald L.

    182 28th ANNUAL eMS Sorption and Desorption of Quaternary Amine Cations on Clays Z. Z. Zhang and D? The present study was conducted to investigate the sorption and desorption of several quaternary amines on Na of amines was conducted at an ionic strength of 0.01 M, and desorption of amines was studied by adding

  7. Multiplexed global internal standard technique (mGIST) using a quaternary amine coding agent

    Microsoft Academic Search

    Cathy S Sioma

    2003-01-01

    The goal of this research was to investigate the use of a quaternary amine coding agent for the use in Multiplexed Global Internal Standard Technology (mGIST). ^ The work reported here began with the search for a reagent that would improve on the limitations of current GIST reagents. Literature reviews and initial studies indicated that a quaternary amine coding agent

  8. Antistatic Wool. Part II: Quaternary Polyethoxylated Amines As Antistatic Agents for Wool

    Microsoft Academic Search

    Donna M. Brown; M. T. Pailthorpe

    1988-01-01

    An investigation is reported that describes the effects of quaternary polyethoxylated amines on the antistatic properties of wool.The ethoxylated amines reported in previous work were quaternized with benzyl chloride, and the products were found to be very effective in reducing the electrical resistance of wool. The antistatic effect observed for the quaternary ethoxylated amines was not dependent on time, alkyl–chain

  9. A review of Quaternary range shifts in European aquatic Coleopterageb_572 87..100

    E-print Network

    Murcia, Universidad de

    of the Quaternary fossil record of Euro- pean water beetles to evaluate their geographical and temporal coverage compiled Quaternary water beetle records from public databases and published references. We included of the species. Results Our final data set included over 9000 records for 259 water beetle species. Fossil

  10. Late Quaternary variability of sedimentary nitrogen isotopes in the eastern South Pacific Ocean

    E-print Network

    Demouchy, Sylvie

    Late Quaternary variability of sedimentary nitrogen isotopes in the eastern South Pacific Ocean), Late Quaternary variability of sedimentary nitrogen isotopes in the eastern South Pacific Ocean) in the water columns of the Arabian Sea (AS) and the eastern North and South Pacific oceans (ENP; ESP) holds

  11. Late-Quaternary diminution and abundance of prehistoric bison (Bison sp.) in eastern Washington state, USA

    Microsoft Academic Search

    R. Lee Lyman

    Bison (Bison spp.) occurred in eastern Washington state during the late Quaternary. This area is considered to be peripheral to the center of this taxon's natural range. Bison in the plains east of the Rocky Mountains, the heart of this range, underwent diminution during the late Quaternary, and apparently also did so in other, peripheral areas. A ratio diagram of

  12. Neutron emission as a clock and thermometer to probe the dynamics of fusion-fission and quasi-fission

    NASA Astrophysics Data System (ADS)

    Hinde, D. J.

    1993-03-01

    A compilation of currently available data on pre-scission neutron multiplicities shows clearly that the excitation energy in the fission fragments hardly increases with bombarding energy. This can be explained if fission is always a slow process, whilst evaporation becomes more and more rapid. The neutron clock-thermometer is introduced as a tool to deduce the dynamical timescale for fusion-fission, giving (35±15)×10-21 s. Quasi-fission is faster than fusion-fission because the equilibrium deformation is never reached (the mononucleus is thought to be always very deformed) thus fragment temperatures are higher, and the strong variation of vpre with TKE shows that a significant number of neutrons are emitted while the fragments are accelerating after scission. This appears not to be the case for fusion-fission. The fall in vpre for asymmetric mass-splits suggests that the dynamical time scale is shorter: this will influence fission mass-distributions.

  13. A correlated electron view of singlet fission.

    PubMed

    Zimmerman, Paul M; Musgrave, Charles B; Head-Gordon, Martin

    2013-06-18

    Singlet fission occurs when a single exciton splits into multiple electron-hole pairs, and could dramatically increase the efficiency of organic solar cells by converting high energy photons into multiple charge carriers. Scientists might exploit singlet fission to its full potential by first understanding the underlying mechanism of this quantum mechanical process. The pursuit of this fundamental mechanism has recently benefited from the development and application of new correlated wave function methods. These methods-called restricted active space spin flip-can capture the most important electron interactions in molecular materials, such as acene crystals, at low computational cost. It is unrealistic to use previous wave function methods due to the excessive computational cost involved in simulating realistic molecular structures at a meaningful level of electron correlation. In this Account, we describe how we use these techniques to compute single exciton and multiple exciton excited states in tetracene and pentacene crystals in order to understand how a single exciton generated from photon absorption undergoes fission to generate two triplets. Our studies indicate that an adiabatic charge transfer intermediate is unlikely to contribute significantly to the fission process because it lies too high in energy. Instead, we propose a new mechanism that involves the direct coupling of an optically allowed single exciton to an optically dark multiexciton. This coupling is facilitated by intermolecular motion of two acene monomers that drives nonadiabatic population transfer between the two states. This transfer occurs in the limit of near degeneracies between adiabatic states where the Born-Oppenheimer approximation of fixed nuclei is no longer valid. Existing theories for singlet fission have not considered this type of coupling between states and, therefore, cannot describe this mechanism. The direct mechanism through intermolecular motion describes many experimentally observed characteristics of these materials, such as the ultrafast time scale of photobleaching and triplet generation during singlet fission in pentacene. We believe this newly discovered mechanism provides fundamental insight to guide the creation of new solar materials that exhibit high efficiencies through multiple charge generation. PMID:23427823

  14. Environ. Sci. Technol. 1993, 27, 1625-1631 Sorptlon and Desorption of Quaternary Amine Cations on Clays

    E-print Network

    Sparks, Donald L.

    Environ. Sci. Technol. 1993, 27, 1625-1631 Sorptlon and Desorption of Quaternary Amine Cations 19714 We have studied the sorption and desorption of three quaternary amines, namely-montmorillonite using a titration procedure. More than 99% of all three of the quaternary amine cations studied were

  15. An aminostratigraphy for the British Quaternary based on Bithynia opercula

    PubMed Central

    Penkman, Kirsty E.H.; Preece, Richard C.; Bridgland, David R.; Keen, David H.; Meijer, Tom; Parfitt, Simon A.; White, Tom S.; Collins, Matthew J.

    2013-01-01

    Aminostratigraphies of Quaternary non-marine deposits in Europe have been previously based on the racemization of a single amino acid in aragonitic shells from land and freshwater molluscs. The value of analysing multiple amino acids from the opercula of the freshwater gastropod Bithynia, which are composed of calcite, has been demonstrated. The protocol used for the isolation of intra-crystalline proteins from shells has been applied to these calcitic opercula, which have been shown to more closely approximate a closed system for indigenous protein residues. Original amino acids are even preserved in bithyniid opercula from the Eocene, showing persistence of indigenous organics for over 30 million years. Geochronological data from opercula are superior to those from shells in two respects: first, in showing less natural variability, and second, in the far better preservation of the intra-crystalline proteins, possibly resulting from the greater stability of calcite. These features allow greater temporal resolution and an extension of the dating range beyond the early Middle Pleistocene. Here we provide full details of the analyses for 480 samples from 100 horizons (75 sites), ranging from Late Pliocene to modern. These show that the dating technique is applicable to the entire Quaternary. Data are provided from all the stratotypes from British stages to have yielded opercula, which are shown to be clearly separable using this revised method. Further checks on the data are provided by reference to other type-sites for different stages (including some not formally defined). Additional tests are provided by sites with independent geochronology, or which can be associated with a terrace stratigraphy or biostratigraphy. This new aminostratigraphy for the non-marine Quaternary deposits of southern Britain provides a framework for understanding the regional geological and archaeological record. Comparison with reference to sites yielding independent geochronology, in combination with other lines of evidence, allows tentative correlation with the marine oxygen isotope record. PMID:23396683

  16. Arctic-alpine blockfields in northern Sweden: Quaternary not Neogene

    NASA Astrophysics Data System (ADS)

    Goodfellow, B. W.; Stroeven, A. P.; Fabel, D.; Fredin, O.; Derron, M.-H.; Bintanja, R.; Caffee, M. W.

    2014-02-01

    Slowly-eroding, blockfield-mantled, non-glacial surface remnants may serve as markers against which to determine Quaternary glacial erosion volumes in high latitude mountain settings. To investigate this potential utility of these surfaces, chemical weathering, erosion rates, and origins of mountain blockfields are investigated in northern Sweden. This is done, firstly, by assessing the intensity of regolith chemical weathering along altitudinal transects descending from three blockfield-mantled summits. Clay/silt ratios, secondary mineral assemblages determined through X-ray diffraction, and the presence of chemically weathered grains visible on scanning electron microscopy, in fine matrix samples collected from pits excavated along the transects are each used for this purpose. Secondly, erosion rates and total surface histories of two of the summits are inferred from concentrations of in situ-produced cosmogenic 10Be and 26Al in quartz at the blockfield surface. An interpretative model is adopted that includes temporal variations in nuclide production rates through surface burial by glacial ice and glacial isostasy-induced elevation changes of the blockfield surfaces. Together, our data indicate that these blockfields are not derived from remnants of intensely weathered Neogene weathering profiles, as is commonly considered. Evidence for this interpretation includes minor chemical weathering in each of the three examined blockfields, despite some differences according to slope position. In addition, average erosion rates of ∼16.2 mm ka-1 and ∼6.7 mm ka-1, calculated for two blockfield-mantled summits, are low but of sufficient magnitude to remove present blockfield mantles, of up to a few meters in thickness, within a late-Quaternary timeframe. Hence, blockfield mantles appear to be replenished by regolith formation through, primarily physical, weathering processes that have operated during the Quaternary. Erosion rates remain low enough, however, for blockfield-mantled, non-glacial surface remnants to provide reasonable landscape markers against which to contrast Quaternary erosion volumes in surrounding glacial landscape elements. The persistence of blockfield mantles over a number of glacial-interglacial cycles and an apparently low likelihood that they can re-establish on glacially eroded bedrock, also discounts the operation of a "glacial buzz-saw" on surface remnants that are presently perceived as non-glacial. These interpretations are tempered though by outstanding questions concerning the composition of preceding Neogene regoliths and why they have apparently been comprehensively removed from these remnant non-glacial surfaces. It remains possible that periglacial erosion of perhaps more intensely weathered Neogene regoliths was high during the Pliocene-Pleistocene transition to colder conditions and that periglacial processes reshaped non-glacial surface remnants largely before the formation of blockfield armours.

  17. Quaternary Faults and Folds by State and Region

    NSDL National Science Digital Library

    This interactive map of the United states provides access to maps of Quaternary faults and folds by state or region (for example, the Gulf Coast). Clicking on the colored areas of the map links the user to state/regional maps and further, to 1x2 degree sheets for each area. On the sheets, users can find faults numbered and indexed to a legend. Links from the legend provide access to written information, where available, for each fault. There are three levels of written reports, ranging from a brief synopsis to a "complete" report that includes references.

  18. Synthesis and antibacterial activities of quaternary ammonium salt of chitosan

    Microsoft Academic Search

    Zhishen Jia; Dongfeng shen; Weiliang Xu

    2001-01-01

    Chitosan derivatives with quaternary ammonium salt, such as N,N,N-trimethyl chitosan, N–N-propyl-N,N-dimethyl chitosan and N-furfuryl-N,N-dimethyl chitosan were prepared using different 96% deacetylated chitosan of Mv 2.14×105, 1.9×104, 7.8×103. Amino groups on chitosan react with aldehydes to from a Schiff base intermediate. Quaternized chitosan were obtained by reaction of a Schiff base with methyl iodide. The yields, degree of quaternization and water-solubility

  19. Quaternary Fault and Fold Database for the United States: California

    NSDL National Science Digital Library

    This interactive map shows the major fault systems of the Quaternary for the State of California. It is subdivided into 1x2 degree sheets, each of which is linked to a more detailed map. Users can select a sheet and see an enlargement of the area. Individual fault systems are numbered and keyed to a legend which provides a link to a written synopsis of information for the fault, including fault type and geologic history. Links are also provided to more extensive reports for the faults, including a "complete" report with references.

  20. Cyclic explosive activity of the Iceland plume in the quaternary

    NASA Astrophysics Data System (ADS)

    Eroshenko, D. V.; Kharin, G. S.

    2014-02-01

    Data on the volcanic ash layers in 70 DSDP and ODP Sites and 100 cores obtained during cruises of the R/V Akademik Kurchatov and Mikhail Lomonosov were used for compiling tephrostratigraphic scale and schematic distribution maps of the pyroclastic material in the Quaternary sediments of the North Atlantic and Norwegian-Greenland Basin. It is revealed that the distribution of pyroclastic material through this region is characterized by cyclic and spatially irregular patterns. Based on their petrochemical and geochemical properties, these ashes are compared with the volcanics of Iceland and the Jan Mayen islands. The relations between the extreme climatic and cyclic explosive events are discussed.

  1. Extraction of actinides by quaternary amines from hydrochloric acid medium

    Microsoft Academic Search

    V. R. Bhandiwad; Rajendra Swarup; S. K. Patil

    1979-01-01

    The extraction of Np(IV), Pu(IV) and U(VI) from aqueous hydrochloric acid into quaternary amines has been studied. The dependence\\u000a of the distribution coefficient on amine concentration suggests that the actinide ions extracted are NpCl\\u000a 6\\u000a 2?\\u000a PuCl\\u000a 6\\u000a 2?\\u000a and UO2Cl\\u000a 4\\u000a 2?\\u000a . This is further supported by the absorption spectra of the amine extracts of these actinide ions.

  2. Neutron angular correlations in spontaneous and neutron-induced fission

    NASA Astrophysics Data System (ADS)

    Vogt, R.; Randrup, J.

    2014-12-01

    Background: Neutron emission is correlated in fission events because, on average, more than one neutron is emitted per fission. Measurements of these correlations, coupled with studies of more inclusive observables such as neutron multiplicity, provide sensitive information about the fission mechanism. Neutron-neutron angular correlations have been studied in both spontaneous fission of 252Cf and neutron-induced fission of 235U. These correlations, until recently incalculable in most available simulations of fission, can now be calculated in event-by-event simulations of fission. Purpose: Phenomenological studies of fission are of interest both for basic science and for practical applications. Neutron-neutron angular correlations are characteristic of the fissioning isotope and could be used in material identification. Method: We use our model of complete fission events, freya, to first study the sensitivity of two-neutron angular correlations to the model inputs and then compare to available data. We also compare our simulations to neutron-fragment angular correlations. Results: We find that the correlations calculated with freya are fairly robust with respect to the input parameters. Any strong deviations in the correlations result in poor agreement with measured inclusive neutron observables such as neutron multiplicity as a function of fragment mass and the neutron multiplicity distribution. The agreement of freya with the present set of correlation data is found to be good. Conclusions: freya can be used to reliably predict neutron-neutron angular correlations and could then be used to identify materials.

  3. Spontaneous fission half-lives and their systematics

    SciTech Connect

    Holden, N.E.

    1998-03-01

    Spontaneous fission is a phenomenon exhibited by heavy nuclei, which can be a major mode of decay of nuclei of elements heavier than thorium and can be a determining factor in their stability. For purposes of this paper, spontaneous fission will be considered a process in which a nucleus breaks up into two approximately equal parts. The emission of light nuclei or heavy ions such as {sup 12}C, {sup 16}O, or {sup 32}S will not be considered. This radioactive decay mode is often much smaller than the spontaneous fission decay mode, although this is not true in all cases. Barwick noted that this might indicate that the assumed half-life for spontaneous fission of some older experiments might be partially due to heavy fragment radioactivity. Other than taking note of this potential correction to spontaneous fission half-lives, this decay mode of heavy fragment radioactivity will be ignored. Excited states of some heavy nuclei may decay via spontaneous fission. These so-called fission isomers will not be discussed here. Electron capture (EC) or beta-delayed fission is a process in which prompt fission of a sufficiently excited daughter state occurs following population by EC or beta decay. The fission activity will appear to decay with the half-life of the parent and was earlier confused in some cases with SF. This process has been discussed in detail in a review and will not be considered in this paper.

  4. True ternary fission of superheavy nuclei

    SciTech Connect

    Zagrebaev, V. I.; Karpov, A. V. [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, 141980 Dubna, Moscow Region (Russian Federation); Greiner, Walter [Frankfurt Institute for Advanced Studies, J.W. Goethe-Universitaet, D-60438 Frankfurt am Main (Germany)

    2010-04-15

    True ternary fission with formation of a heavy third fragment is quite possible for superheavy nuclei because of the strong shell effects leading to a three-body clusterization with the two doubly magic tinlike cores. The simplest way to discover this phenomenon in the decay of excited superheavy nuclei is a detection of two tinlike clusters with appropriate kinematics in low-energy collisions of medium-mass nuclei with actinide targets. The three-body quasi-fission process could be even more pronounced for giant nuclear systems formed in collisions of heavy actinide nuclei. In this case a three-body clusterization might be proved experimentally by the detection of two coincident leadlike fragments in low-energy U + U collisions.

  5. Nuclear Fission Investigation with Twin Ionization Chamber

    SciTech Connect

    Zeynalova, O.; Zeynalov, Sh. [JINR-Joint Institute for Nuclear Research, Dubna, Moscow region (Russian Federation); Nazarenko, M. [Moscow State Institute of Radioengineering and Automation, 78 Vernadski Avenue, 119454 Moscow (Russian Federation); Hambsch, F.-J.; Oberstedt, S. [EC-JRC Institute for Reference Materials and Measurements, Retieseweg 111, 2440 Geel (Belgium)

    2011-11-29

    The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.

  6. Nuclear Fission Investigation with Twin Ionization Chamber

    NASA Astrophysics Data System (ADS)

    Zeynalova, O.; Zeynalov, Sh.; Nazarenko, M.; Hambsch, F.-J.; Oberstedt, S.

    2011-11-01

    The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.

  7. Search for the inverse fission of uranium

    NASA Astrophysics Data System (ADS)

    Loveland, W.; Yanez, R.; Beckerman, J.; Leonard, M.; Pettersson, G.; Gross, C. J.; Shapira, D.; Liang, J. F.; Kohley, Z.; Varner, R. L.

    2011-10-01

    A search for the ``inverse fission'' of uranium has been made. Two ``inverse fission'' reactions were studied, the reaction of 124Sn + 100Mo and the reaction of 132Sn + 100Mo. In the former case, evaporation residues were searched for using (a) in-beam ?-spectroscopy, (b) post-irradiation ?-spectroscopy and (c) in-beam detection of recoiling evaporation residues while in the latter case, the evaporation residue, 230U was searched for using post irradiation radio-analytical techniques. Data acquisition and analysis is on-going with expected upper limits or production cross sections of < 1 microbarn. The implications of these results for determining the fusion probability, PCN, in the collisions of massive nuclei are discussed. This work was supported in part by the USDOE Office of Nuclear Physics under Grant DE-FG06-97ER41026 and Contract No. DE-AC02-06CH11357.

  8. Quality and availability of fission-products

    Microsoft Academic Search

    Rasmussen

    1965-01-01

    The information contained in this report was copied from carts used for discussions at Richland on May 4--6, 1965. Representatives of the Martin Company, US Rubber company, General Electric -- HAPO, and AEC-RL00 were present. The data represent the best current information on the quantity, quality, and availability of each fission product considered, i.e., strontium-90, cesium-137, promethium-147, and cerium-144.

  9. Fission fragment rockets: A new frontier

    SciTech Connect

    Chapline, G.F.; Howard, W.M.; Schnitzler, B.G.

    1989-04-01

    A new reactor concept is described which would enable fission fragments to be continuously extracted from the reactor. Such a reactor has the potential of enabling extremely energetic and ambitious deep space missions. In this talk the basic physics issues involved in the operation of this type of reactor are outlined, and some possible applications to space exploration are described. 3 refs., 2 figs., 3 tabs.

  10. Toward singlet fission for excitonic solar cells

    Microsoft Academic Search

    Josef Michl; Arthur J. Nozik; Xudong Chen; Justin C. Johnson; Geeta Rana; Akin Akdag; Andrew F. Schwerin

    2007-01-01

    Sensitizer dyes capable of producing two triplet excited states from a singlet excited state produced by the absorption of a single photon would allow an increase of the efficiency of photovoltaic cells by up to a factor of 1.5, provided that each triplet injects an electron into a semiconductor such as TiO2. Although singlet fission in certain crystals and polymers

  11. Fission gas retention in irradiated metallic fuel

    Microsoft Academic Search

    G. R. Fenske; E. E. Gruber; J. M. Kramer

    1987-01-01

    Theoretical calculations and experimental measurements of the quantity of retained fission gas in irradiated metallic fuel (U-5Fs) are presented. The calculations utilize the Booth method to model the steady-state release of gases from fuel grains and a simplified grain-boundary gas model to predict the gas release from intergranular regions. The quantity of gas retained in as-irradiated fuel was determined by

  12. FISSION FRAGMENT RECOIL EFFECTS ON ZIRCONIUM OXIDATION

    Microsoft Academic Search

    W. C. Yee; G. H. Jenks; E. E. Stansbury

    1962-01-01

    Fission fragment recoil effects on zirconium oxidation in pure oxygen ; were studied at 1 atm pressure and 250 deg C. Specimens were oxidized under the ; following conditions: reactor radiations including recoils, reactor radiations in ; the absence of recoils, and no radiation. Irradiation experiments were conducted ; in a maximum thermal neutron flux of 8.5 x 10¹¹ neutrons\\/cm²-sec.

  13. Undergraduate Measurements For Fission Reactor Applications

    Microsoft Academic Search

    S. F. Hicks; L. J. Kersting; C. J. Lueck; P. McDonough; B. P. Crider; M. T. McEllistrem; E. E. Peters; J. R. Vanhoy

    2011-01-01

    Undergraduate students at the University of Dallas (UD) have investigated elastic and inelastic neutron scattering cross sections on structural materials important for criticality considerations in nuclear fission processes. Neutrons scattered off of 23Na and NatFe were detected using neutron time-of-flight techniques at the University of Kentucky Low-Energy Nuclear Accelerator Facility. These measurements are part of an effort to increase the

  14. Fusion, Fission, and Secretion During Phagocytosis

    NSDL National Science Digital Library

    2007-12-01

    Phagocytosis is essential for the elimination of pathogens and for clearance of apoptotic bodies. The ingestion process entails extensive remodeling of the cellular membranes, particularly when large and/or multiple particles are engulfed. The membrane fusion and fission events that accompany phagocytosis are described. The coordinated sequence of membrane trafficking events required for phagocytosis involves multiple organelles and also serves other cellular functions, such as cytokine secretion.

  15. Undergraduate Measurements For Fission Reactor Applications

    SciTech Connect

    Hicks, S. F.; Kersting, L. J.; Lueck, C. J.; McDonough, P. [Department of Physics, University of Dallas, Irving TX 75019 (United States); Crider, B. P.; McEllistrem, M. T.; Peters, E. E. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Vanhoy, J. R. [Department of Physics, United States Naval Academy, Annapolis MD 21402 (United States)

    2011-06-01

    Undergraduate students at the University of Dallas (UD) have investigated elastic and inelastic neutron scattering cross sections on structural materials important for criticality considerations in nuclear fission processes. Neutrons scattered off of {sup 23}Na and {sup Nat}Fe were detected using neutron time-of-flight techniques at the University of Kentucky Low-Energy Nuclear Accelerator Facility. These measurements are part of an effort to increase the efficiency of power generation from existing fission reactors in the US and in the design of new fission systems. Students have learned the basics of how to operate the Model CN Van de Graaff generator at the laboratory, setup detectors and electronics, use data acquisition systems, and they are currently analyzing the angular dependence of the scattered neutrons for incident neutron energies of 3.57 and 3.80 MeV. Most students participating in the project will use the research experience as the material for their undergraduate research thesis required for all Bachelor of Science students at the University of Dallas. The first student projects on this topic were completed during the summer of 2010; an overview of student participation in this investigation and their preliminary results will be presented.

  16. Calculated fission properties of the heaviest elements

    SciTech Connect

    Moeller, P.; Nix, J.R.; Swiatecki, W.J.

    1986-09-01

    A quantitative calculation is presented that shows where high-kinetic-energy symmetric fission occurs and why it is associated with a sudden and large decrease in fission half-lives. The study is based on calculations of potential-energy surfaces in the macroscopic-microscopic model and a semi-empirical model for the nuclear inertia. For the macroscopic part a Yukawa-plus-exponential model is used and for the microscopic part a folded-Yukawa single-particle potential is used. The three-quadratic-surface parameterization generates shapes for which the potential-energy surfaces are calculated. The use of this parameterization and the use of the finite-range macroscopic model allows for the study of two touching spheres and similar shapes. The results of the calculations in terms of potential-energy surfaces and fission half-lives are presented for heavy even nuclei. The surfaces are displayed in the form of contour diagrams as functions of two moments of the shape. 53 refs., 15 figs., 1 tab.

  17. A microfluidic synchronizer for fission yeast cells.

    PubMed

    Tian, Yuan; Luo, Chunxiong; Ouyang, Qi

    2013-10-21

    Among all the cell cycle synchronization technologies, the baby machine may be considered as the most artifact-free method. A baby machine incubates "mother cells" under normal conditions and collects their "babies", producing cell cultures that are similar not only in cell cycle phase but also in age. Unlike many other synchronization methods, no cell-cycle-blocking agent or metabolic stress is introduced in this method. Several macroscale and microfluidic baby machines have been developed for producing synchronized cell colonies. However, for rod-shaped cells like fission yeast (Schizosaccharomyces pombe), it is still a challenge to immobilize only the mother cells in a microfluidic device. Here we presented a new baby machine suitable for fission yeast. The device is fixed one end of the cell and releases the free-end daughter cell every time the cell finishes cytokinesis. A variety of structures for cell immobilization were attempted to find the optimal design. For the convenience of collection and further assay, we integrated into our baby machine chip a cell screener, which exploited the deformation of polymer material to switch between opening and closing states. Synchronous populations of fission yeast cells were produced with this device, its working detail was analyzed and performance was evaluated. The device provides a new on-chip tool for cell biology studies. PMID:23966136

  18. Interstellar rendezvous missions employing fission propulsion systems

    NASA Astrophysics Data System (ADS)

    Lenard, Roger X.; Lipinski, Ronald J.

    2000-01-01

    There has been a conventionally held nostrum that fission system specific power and energy content is insufficient to provide the requisite high accelerations and velocities to enable interstellar rendezvous missions within a reasonable fraction of a human lifetime. As a consequence, all forms of alternative mechanisms that are not yet, and may never be technologically feasible, have been proposed, including laser light sails, fusion and antimatter propulsion systems. In previous efforts, [Lenard and Lipinski, 1999] the authors developed an architecture that employs fission power to propel two different concepts: one, an unmanned probe, the other a crewed vehicle to Alpha Centauri within mission times of 47 to 60 years. The first portion of this paper discusses employing a variant of the ``Forward Resupply Runway'' utilizing fission systems to enable both high accelerations and high final velocities necessary for this type of travel. The authors argue that such an architecture, while expensive, is considerably less expensive and technologically risky than other technologically advanced concepts, and, further, provides the ability to explore near-Earth stellar systems out to distances of 8 light years or so. This enables the ability to establish independent human societies which can later expand the domain of human exploration in roughly eight light-year increments even presuming that no further physics or technology breakthroughs or advances occur. In the second portion of the paper, a technology requirement assessment is performed. The authors argue that reasonable to extensive extensions to known technology could enable this revolutionary capability. .

  19. Time dependent particle emission from fission products

    SciTech Connect

    Holloway, Shannon T [Los Alamos National Laboratory; Kawano, Toshihiko [Los Alamos National Laboratory; Moller, Peter [Los Alamos National Laboratory

    2010-01-01

    Decay heating following nuclear fission is an important factor in the design of nuclear facilities; impacting a variety of aspects ranging from cooling requirements to shielding design. Calculations of decay heat, often assumed to be a simple product of activity and average decay product energy, are complicated by the so called 'pandemonium effect'. Elucidated in the 1970's this complication arises from beta-decays feeding high-energy nuclear levels; redistributing the available energy between betas and gammas. Increased interest in improving the theoretical predictions of decay probabilities has been, in part, motivated by the recent experimental effort utilizing the Total Absorption Gamma-ray Spectrometer (TAGS) to determine individual beta-decay transition probabilities to individual nuclear levels. Accurate predictions of decay heating require a detailed understanding of these transition probabilities, accurate representation of particle decays as well as reliable predictions of temporal inventories from fissioning systems. We will discuss a recent LANL effort to provide a time dependent study of particle emission from fission products through a combination of Quasiparticle Random Phase Approximation (QRPA) predictions of beta-decay probabilities, statistical Hauser-Feshbach techniques to obtain particle and gamma-ray emissions in statistical Hauser-Feshbach and the nuclear inventory code, CINDER.

  20. Notes Bull. Korean Chem. Soc. 2005, Vol. 26, No. 1 175 Synthesis of Novel Biodegradable Quaternary Amine-based Cross-linked

    E-print Network

    Park, Jong-Sang

    , 2004 Key Words : Cross-linked polymer, Quaternary amine, Biodegradability, Gene delivery In recent to linear type carriers.4 Several quaternary amine-based polymeric gene delivery carriers were reported amines.9 Because quaternary amines have no nucleophilicity, quaternary amine-based biodegradable

  1. Late Quaternary terrestrial vertebrate coprolites from New Zealand

    NASA Astrophysics Data System (ADS)

    Wood, Jamie R.; Wilmshurst, Janet M.

    2014-08-01

    Over the past decade, concerted efforts to find and study Late Quaternary terrestrial vertebrate coprolites in New Zealand have revealed new insights into the diets and ecologies of New Zealand's prehistoric birds. Here, we provide a broader review of the coprolites found in natural (non-archaeological) Late Quaternary deposits from New Zealand. We summarise the morphological diversity of the coprolites, and discuss the taphonomy of the sites in which they are found. Since the 1870s more than 2000 coprolites have been discovered from 30 localities, all restricted to the South Island. The distribution of coprolite localities appears to reflect the presence of geological and climatic factors that enhance the potential for coprolite preservation; coprolites require dry conditions for preservation, and have been found on the ground surface within drafting cave entrances and at shallow (<300 mm) depths beneath rock overhangs with a northerly aspect. We classify the coprolites into eleven morphotypes, each of which may represent a range of different bird and/or reptile species. A review of genetically identified specimens shows that coprolites of different bird species overlap in size and morphology, reinforcing the need for identifications to be based on ancient DNA analysis.

  2. Late quaternary environments, Denali National Park and Preserve, Alaska

    USGS Publications Warehouse

    Elias, S.A.; Short, S.K.; Waythomas, C.F.

    1996-01-01

    Late Quaternary pollen, plant macrofossils, and insect fossils were studied from sites along three rivers in the foothills north of the Alaska Range in Denali National Park and Preserve. The aim was to carry out a reconaissance of late Quaternary organic sediments in the region, emphasizing the mid-Wisconsin, or Boutellier interstadial interval. Samples of probable early- to mid-Boutellier age (ca. 60 000 to 40 000 B.P.) from Unit 2 at the Toklat High Bluffs site indicate open boreal woodland with dense alder shrub vegetation. Organic Unit 1 at the Foraker River Slump site indicates open taiga with shrubs of probable Boutellier age. Fossil evidence from the youngest horizon in this unit indicates graminoid tundra environments, marking the transition from interstadial to late Wisconsin glacial environments. Early Holocene samples from the Foraker exposures suggest birch shrub tundra; coniferous forest apparently became established only alter 6500 B.P. Local variations in forest composition at the Foraker and Sushana sites were probably the result of disturbances, such as fire.

  3. Historical distribution of Sundaland's Dipterocarp rainforests at Quaternary glacial maxima.

    PubMed

    Raes, Niels; Cannon, Charles H; Hijmans, Robert J; Piessens, Thomas; Saw, Leng Guan; van Welzen, Peter C; Slik, J W Ferry

    2014-11-25

    The extent of Dipterocarp rainforests on the emergent Sundaland landmass in Southeast Asia during Quaternary glaciations remains a key question. A better understanding of the biogeographic history of Sundaland could help explain current patterns of biodiversity and support the development of effective forest conservation strategies. Dipterocarpaceae trees dominate the rainforests of Sundaland, and their distributions serve as a proxy for rainforest extent. We used species distribution models (SDMs) of 317 Dipterocarp species to estimate the geographic extent of appropriate climatic conditions for rainforest on Sundaland at the last glacial maximum (LGM). The SDMs suggest that the climate of central Sundaland at the LGM was suitable to sustain Dipterocarp rainforest, and that the presence of a previously suggested transequatorial savannah corridor at that time is unlikely. Our findings are supported by palynologic evidence, dynamic vegetation models, extant mammal and termite communities, vascular plant fatty acid stable isotopic compositions, and stable carbon isotopic compositions of cave guano profiles. Although Dipterocarp species richness was generally lower at the LGM, areas of high species richness were mostly found off the current islands and on the emergent Sunda Shelf, indicating substantial species migration and mixing during the transitions between the Quaternary glacial maxima and warm periods such as the present. PMID:25385612

  4. Distribution and metabolism of quaternary amines in salt marshes

    NASA Technical Reports Server (NTRS)

    King, Gary M.

    1985-01-01

    Quaternary amines such as glycine betaine (GBT) are common osmotically active solutes in much of the marine biota. GBT is accumulated by various bacteria, algae, higher plants, invertebrates, and vertebrates in response to salinity or water stresses; in some species, GBT occurs at tens to hundreds of millimolar concentrations and can account for a significant fraction of total nitrogen. Initial studies suggest that GBT is readily converted to two potential methane precursors, trimethylamine (TMA) and acetate, in anoxic sediments. TMA is apparently the most important methane precursor in surface sediments containing sulfate reducing bacteria. In salt marshes, the bulk of the methane formed may be due to the metabolism of TMA rather than other substrates. Current research is focussed on testing this hypothesis and on determining the role of quaternary amino osmoregulatory solutes in methane fluxes from marine environments. Preliminary studies have dealt with several problems: (1) determination of GBT concentrations in the dominant flora and fauna of salt marshes; (2) synthesis of radiolabelled GBT for metabolic studies; and (3) determination of fates of BGT in marine sediments using radiotracers. Both GC and HPLC techniques have been used to assay GBT concentrations in plant and animal tissues. S. alterniflora is probably the only significant source of GBT (and indirectly of methane) since the biomass and distribution of most other species is limited. Current estimates suggest that S. alterniflora GBT could account for most of the methane efflux from salt marshes.

  5. Fission Cross Sections and Fission-Fragment Mass Yields via the Surrogate Reaction Method

    SciTech Connect

    Jurado, B.; Kessedjian, G.; Aiche, M.; Barreau, G.; Bidaud, A.; Czajkowski, S.; Dassie, D.; Haas, B.; Mathieu, L.; Osmanov, B. [CENBG, CNRS/IN2P3, Univ. Bordeaux I, Chemin du Solarium B.P. 120, 33175 Gradignan (France); Audouin, L.; Capellan, N.; Tassan-Got, L.; Wilson, J. N. [IPN, CNRS/IN2P3, Univ. Paris-Sud, 91405 Orsay (France); Berthoumieux, E.; Gunsing, F.; Theisen, Ch. [CEA Saclay, DSM/DAPNIA/SPhN, 91191 Gif-sur-Yvette cedex (France); Serot, O. [CEA-Cadarache, DEN/DER/SPRC/LEPh, 13108 Saint Paul lez Durance (France); Bauge, E. [CEA, SPN, BP12, 91680 Bruyeres-le-Chatel (France); Ahmad, I. [Physics Division, Argonne National Laboratory, 9700 S. Cass Avenue, IL 60439 (United States)] (and others)

    2008-04-17

    The surrogate reaction method is a powerful tool to infer neutron-induced data of short-lived nuclei. After a short overview of the experimental techniques employed in the present surrogate experiments, we will concentrate on a recent measurement to determine neutron-induced fission cross sections for the actinides {sup 242,243}Cm and {sup 241}Am. The latest direct neutron-induced measurement for the {sup 243}Cm fission cross section is questioned by our results, since there are differences of more than 60% in the 0.7 to 7 MeV neutron energy range. Our experimental set-up has also enabled us to measure for the first time the fission fragment ''pseudo-mass'' distributions of {sup 243,244,245}Cm and {sup 242}Am compound nuclei in the excitation energy range from a few MeV to about 25 MeV.

  6. Exotic fission properties of highly neutron-rich Uranium isotopes

    E-print Network

    L. Satpathy; S. K. Patra; R. K. Choudhury

    2007-03-05

    The series of Uranium isotopes with $N=154 \\sim 172$ around the magic number N=162/164 are identified to be thermally fissile. The thermal neutron fission of a typical representative $^{249}$U of this region amenable to synthesis in the radioactive ion beam facilities is considered here. Semiempirical study of fission barrier height and width shows this nucleus to be infinitely stable against spontaneous fission due to increase in barrier width arising out of excess neutrons. Calculation of probability of fragment mass yields and microscopic study in relativistic mean field theory, show this nucleus to undergo a new mode of thermal fission decay termed {\\it multifragmentation fission} where a number of prompt scission neutrons are simultaneously released along with the two heavy fission fragments.

  7. Microscopic theory of singlet exciton fission. I. General formulation

    NASA Astrophysics Data System (ADS)

    Berkelbach, Timothy C.; Hybertsen, Mark S.; Reichman, David R.

    2013-03-01

    Singlet fission, a spin-allowed energy transfer process generating two triplet excitons from one singlet exciton, has the potential to dramatically increase the efficiency of organic solar cells. However, the dynamical mechanism of this phenomenon is not fully understood and a complete, microscopic theory of singlet fission is lacking. In this work, we assemble the components of a comprehensive microscopic theory of singlet fission that connects excited state quantum chemistry calculations with finite-temperature quantum relaxation theory. We elaborate on the distinction between localized diabatic and delocalized exciton bases for the interpretation of singlet fission experiments in both the time and frequency domains. We discuss various approximations to the exact density matrix dynamics and propose Redfield theory as an ideal compromise between speed and accuracy for the detailed investigation of singlet fission in dimers, clusters, and crystals. Investigations of small model systems based on parameters typical of singlet fission demonstrate the numerical accuracy and practical utility of this approach.

  8. Microscopic theory of singlet exciton fission. I. General formulation.

    PubMed

    Berkelbach, Timothy C; Hybertsen, Mark S; Reichman, David R

    2013-03-21

    Singlet fission, a spin-allowed energy transfer process generating two triplet excitons from one singlet exciton, has the potential to dramatically increase the efficiency of organic solar cells. However, the dynamical mechanism of this phenomenon is not fully understood and a complete, microscopic theory of singlet fission is lacking. In this work, we assemble the components of a comprehensive microscopic theory of singlet fission that connects excited state quantum chemistry calculations with finite-temperature quantum relaxation theory. We elaborate on the distinction between localized diabatic and delocalized exciton bases for the interpretation of singlet fission experiments in both the time and frequency domains. We discuss various approximations to the exact density matrix dynamics and propose Redfield theory as an ideal compromise between speed and accuracy for the detailed investigation of singlet fission in dimers, clusters, and crystals. Investigations of small model systems based on parameters typical of singlet fission demonstrate the numerical accuracy and practical utility of this approach. PMID:23534622

  9. Experiments on nuclear fission induced by radioactive beams

    SciTech Connect

    Skobelev, N.K. [Joint Institute for Nuclear Research, Moscow (Russian Federation)

    1994-07-01

    The cross sections of {sup 209}Bi nuclear fission induced by secondary beams of {sup 6}He and {sup 4}He are measured under identical conditions. The experimental data are in good agreement with earlier results on the fission cross section of the {sup 4}He + {sup 209}Bi reaction. The measured values of the cross section of {sup 209}Bi fission induced by {sup 6}He ions are much higher than the cross sections of fission induced by {alpha}-particles. It is found that the fission threshold for the {sup 6}He + {sup 209}Bi reaction is shifted as compared to that of the {sup 4}He + {sup 209}Bi reaction. Various factors that can be responsible for the observed peculiarities in the {sup 209}Bi fission induced by the {sup 6}He ions are analyzed. 25 refs., 5 figs.

  10. Frequent gene fissions associated with human pathogenic bacteria.

    PubMed

    Karamichali, Ioanna; Koumandou, V Lila; Karagouni, Amalia D; Kossida, Sophia

    2014-01-01

    Gene fusion and fission events are important for evolutionary studies and for predicting protein-protein interactions. Previous studies have shown that fusion events always predominate over fission events and, in their majority, they represent singular events throughout evolution. In this project, the role of fusion and fission events in the genome evolution of 104 human bacterial pathogens was studied. 141 protein pairs were identified to be involved in gene fusion or fission events. Surprisingly, we find that, in the species analyzed, gene fissions prevail over fusions. Moreover, while most events appear to have occurred only once in evolution, 23% of the gene fusion and fission events identified are deduced to have occurred independently multiple times. Comparison of the analyzed bacteria with non-pathogenic close relatives indicates that this impressive result is associated with the recent evolutionary history of the human bacterial pathogens, and thus is probably caused by their pathogenic lifestyle. PMID:24530517

  11. Early results utilizing high-energy fission product (gamma) rays to detect fissionable material in cargo

    SciTech Connect

    Slaughter, D R; Accatino, M R; Bernstein, A; Church, J A; Descalle, M A; Gosnell, T B; Hall, J M; Loshak, A; Manatt, D R; Mauger, G J; McDowell, M; Moore, T M; Norman, E B; Pohl, B A; Pruet, J A; Petersen, D C; Walling, R S; Weirup, D L; Prussin, S G

    2004-09-30

    A concept for detecting the presence of special nuclear material ({sup 235}U or {sup 239}Pu) concealed in intermodal cargo containers is described. It is based on interrogation with a pulsed beam of 7 MeV neutrons that produce fission events and their {beta}-delayed neutron emission or {beta}-delayed high-energy {gamma}-radiation between beam pulses provide the detection signature. Fission product {beta}-delayed {gamma}-rays above 3 MeV are nearly ten times more abundant than {beta}-delayed neutrons and are distinct from natural radioactivity and from nearly all of the induced activity in a normal cargo. Detector backgrounds and potential interferences with the fission signature radiation have been identified and quantified. An important goal in the US is the detection of nuclear weapons or special nuclear material (SNM) concealed in intermodal cargo containers. This must be done with high detection probability, low false alarm rates, and without impeding commerce, i.e. about one minute for an inspection. The concept for inspection has been described before and its components are now being evaluated. While normal radiations emitted from plutonium may allow its detection, the majority of {sup 235}U {gamma} ray emission is at 186 keV, is readily attenuated by cargo, and thus not a reliable detection signature for passive detection. Delayed neutron detection following a neutron or photon beam pulse has been used successfully to detect lightly or unshielded SNM targets. While delayed neutrons can be easily distinguished from beam neutrons they have relatively low yield in fission, approximately 0.008 per fission in {sup 239}Pu and 0.017 per fission in {sup 235}U, and are rapidly attenuated in hydrogenous materials making that technique unreliable when challenged by thick hydrogenous cargo overburden. They propose detection of {beta}-delayed high-energy {gamma} radiation as a more robust signature characteristic of SNM.

  12. Search for {beta}-delayed fission of {sup 228}Ac

    SciTech Connect

    Xu Yanbing; Ding Huajie; Yuan Shuanggui; Yang Weifan; Niu Yanning; Li Yingjun; Xiao Yonghou [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhang Shengdong [China Institute of Atomic Energy, Beijing 102413 (China); Lu Xiting [School of Physics, Peking University, Beijing 1000871 (China)

    2006-10-15

    Radium was radiochemically separated from natural thorium. Thin {sup 228}Ra{yields}{beta}{sup -228}Ac sources were prepared and exposed to mica fission track detectors, and measured by an HPGe {gamma}-ray detector. The {beta}-delayed fission events of {sup 228}Ac were observed and its {beta}-delayed fission probability was found to be (5{+-}2)x10{sup -12}.

  13. A warning on fission resonance intergrals: Caveat utor

    SciTech Connect

    Holden, N.E.

    1988-01-01

    A common error is made in defining the resonance integral in most tabulations and handbooks. Although it has a minor effect on the capture resonance integral and on the fission resonance integral for the fissile nuclides, it leads to gross errors in the fission resonance integral for the fertile nuclides. The errors in the fission resonance integral for fertile nuclides of the elements from thorium through curium in the ENDF/B-V library will be presented. Let the user beware.

  14. Neutron emission from fission fragments during acceleration p

    SciTech Connect

    Hinde, D.J.; Charity, R.J.; Foote, G.S.; Leigh, J.R.; Newton, J.O.; Ogaza, S.; Chatterjee, A.

    1984-03-19

    Fission-neutron angular correlations following fusion of /sup 19/F and /sup 232/Th have been measured. Conventional analysis, based on the approximation that post-fission neutrons originate only from fully accelerated fission fragments, gives unexpectedly large numbers of ''prefission'' neutrons. Comparison with the considerably less fissile system /sup 200/Pb gives the first convincing evidence that this approach is inadequate. Consideration of neutron emission from the accelerating fragments gives results consistent with expectations.

  15. Neutron flux profile monitor for use in a fission reactor

    DOEpatents

    Kopp, Manfred K. (Oak Ridge, TN); Valentine, Kenneth H. (Lenoir City, TN)

    1983-01-01

    A neutron flux monitor is provided which consists of a plurality of fission counters arranged as spaced-apart point detectors along a delay line. As a fission event occurs in any one of the counters, two delayed current pulses are generated at the output of the delay line. The time separation of the pulses identifies the counter in which the particular fission event occured. Neutron flux profiles of reactor cores can be more accurately measured as a result.

  16. Fission barriers heights in A$\\sim$ 200 mass region

    E-print Network

    Mahata, K

    2015-01-01

    Statistical model analysis has been carried out for $p$ and $\\alpha$ induced fission reactions using a consistent description for fission barrier and level density in A $\\sim$ 200 mass region. A continuous damping of shell correction with excitation energy have been considered. Extracted fission barriers agree well with the recent microscopic-macroscopic model. The shell corrections at the saddle point were found to be not significant.

  17. Fission barriers heights in A$\\sim$ 200 mass region

    E-print Network

    K. Mahata

    2015-05-29

    Statistical model analysis has been carried out for $p$ and $\\alpha$ induced fission reactions using a consistent description for fission barrier and level density in A $\\sim$ 200 mass region. A continuous damping of shell correction with excitation energy have been considered. Extracted fission barriers agree well with the recent microscopic-macroscopic model. The shell corrections at the saddle point were found to be not significant.

  18. New Fission Cross Section Measurements using a Time Projection Chamber

    NASA Astrophysics Data System (ADS)

    Sadler, Michael

    2008-03-01

    A group of six universities (ACU, California Polytechnic, Colorado School of Mines, Georgia Institute of Technology, Ohio, and Oregon State) and three national laboratories (Los Alamos, Lawrence Livermore, and Idaho) have undertaken the task of building a Time Projection Chamber (TPC) to measure the fission cross sections needed for the next generation of nuclear reactors. The fission TPC concept will be presented, and why we think we can improve on 50 years of fission study.

  19. Charge distribution in low energy fission of actinides

    Microsoft Academic Search

    H. Naik; R. J. Singh; R. H. Iyer

    2004-01-01

    Charge distribution studies were carried out for heavy mass fission products in the thermal neutron induced fission of 232U and 238Pu as well as in the spontaneous fission of 244Cm using off-line gamma ray spectrometry. The width parameter (sgrZ\\/sgrA), the most probable charge\\/mass (Zp\\/Ap) and the charge polarization (DgrZ) as a function of fragment mass were deduced. The slope of

  20. Charge distribution in low energy fission of actinides

    Microsoft Academic Search

    H Naik; R J Singh; R H Iyer

    2004-01-01

    Charge distribution studies were carried out for heavy mass fission products in the thermal neutron induced fission of 232U and 238Pu as well as in the spontaneous fission of 244Cm using off-line gamma ray spectrometry. The width parameter (?Z\\/?A), the most probable charge\\/mass (Zp\\/Ap) and the charge polarization (?Z) as a function of fragment mass were deduced. The slope of

  1. Macroscopic Features of Light Heavy-Ion Fission Reactions

    E-print Network

    C. Beck; A. Szanto de Toledo

    1995-12-19

    Global macroscopic features observed in the fully-damped binary processes in light di-nuclear systems, such as limiting angular momenta, mean total kinetic energies and energy thresholds for fusion-fission processes (''fission thresholds") are presented. Their deduced systematics are consistent with that obtained for heavier systems and follow a fusion-fission picture which can be described by a realistic rotating liquid drop model considering diffuse-surface and finite-nuclear-range effects.

  2. Fission of actinide nuclei using multi-nucleon transfer reactions

    NASA Astrophysics Data System (ADS)

    Léguillon, Romain; Nishio, Katsuhisa; Hirose, Kentaro; Orlandi, Riccardo; Makii, Hiroyuki; Nishinaka, Ichiro; Ishii, Tetsuro; Tsukada, Kazuaki; Asai, Masato; Chiba, Satoshi; Ohtsuki, Tsutomu; Araki, Shohei; Watanabe, Yukinobu; Tatsuzawa, Ryotaro; Takaki, Naoyuki

    2014-09-01

    We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. We are promoting a campaign to measure fission-fragment mass distributions for neutron-rich actinide nuclei populated by transfer reactions from their ground state up to an excitation energy of several tens MeV. We thus obtain the excitation energy dependence of the mass distribution. The experiment was carried out at the 20 MV JAEA tandem facility at Tokai. We report on the data obtained in the direct reaction 18 O + 232 Th . Transfer-channels and excitation energies of the fissioning nuclei were identified using silicon dE-E detectors located at forward angle. Two fission fragments were detected in coincidence using multi-wire proportional counters. Fission fragment masses were determined by kinematic consideration. We obtained the fission fragment mass distributions for 13 nuclei from actinium to uranium and some fission barrier heights. Present study is supported by the Ministry of Education, Culture, Sports, Science and Technology of Japan.

  3. Eruptive history of Earth's largest Quaternary caldera (Toba, Indonesia) clarified

    Microsoft Academic Search

    C. A. Chesner; W. I. Rose; A. Deino; R. Drake; J. A. Westgate

    1991-01-01

    Single-grain laser-fusion 40Ar\\/39Ar analyses of individual sanidine phenocrysts from the two youngest Toba (Indonesia) tuffs yield mean ages of 73 ±4 and 501 ±5 ka. In addition, glass shards from Toba ash deposited in Malaysia were dated at 68 ±7 ka by the isothermal plateau fission-track technique. These new determinations, in conjunction with previous ages for the two oldest tuffs

  4. Generalized Energy-Dependent Q Values for Fission

    SciTech Connect

    Vogt, R

    2010-03-31

    We extend Madland's parameterization of the energy release in fission to obtain the dependence of the fission Q value for major and minor actinides on the incident neutron energies in the range 0 {le} E{sub n} {le} 20 MeV. Our parameterization is based on the actinide evaluations recommended for the ENDF/B-VII.1 release. This paper describes the calculation of energydependent fission Q values based on the calculation of the prompt energy release in fission by Madland. This calculation was adopted for use in the LLNL ENDL database and then generalized to obtain the prompt fission energy release for all actinides. Here the calculation is further generalized to the total energy release in fission. There are several stages in a fission event, depending on the time scale. Neutrons and gammas may be emitted at any time during the fission event.While our discussion here is focussed on compound nucleus creation by an incident neutron, similar parameterizations could be obtained for incident gammas or spontaneous fission.

  5. Coal cleaning employing quaternary salts: Final report, July 1, 1985-February 28, 1986

    SciTech Connect

    Hippo, E.J.; Murdie, N.

    1986-05-01

    Investigation into a novel approach to coal desulfurization has continued. This approach is envisioned to include a treatment step to swell coal in quaternary salt solution, followed by physical separation, chemical reaction to desulfurize the coal, and recovery of the quaternary salt. The objective of the first step of the program was to define conditions under which complete exchange of quaternary salts with coal hydroxy groups occurs, define the extent of coal swelling and changes in coal properties as a function of amount of exchange, and determine the effect of process variation on swelling rate and coal properties. Results of this reaction have demonstrated that substantial coal swelling occurs in the presence of quaternary salts. The amount of quaternary exchange is a small portion of the total OH groups present in the coal. Swelling was found to depend on the concentration of quaternary salts, ratio of solution to coal, time of exchange (less than one hour), type and amount of solvent, pH, and coal composition, but was independent of particle size (<-60 mesh), temperature, and soak time < one hour. Recent data have shown that pyrite and inertinite can be concentrated after quaternary salt treatment. Excessive swelling with little exchange indicates that changes occur in the surface chemistry of the coal during reaction. Thus, oil agglomeration and froth flotation should be improved when coals are treated with quaternary salt. Optical microscopic analysis of the treated coals indicates that swelling and exchange are maceral dependent. In addition, swelling causes liberation of pyrite and inertinite which become isolated or exposed at edge/crack sites. Work is now concentrating on the development of mineral separation from coal and recovery of quaternary salt. 12 refs., 13 figs., 17 tabs.

  6. Fission chamber measurements of ²³⁵U fission for encapsulated ²⁵²Cf sources

    Microsoft Academic Search

    R. A. Hamblen

    1987-01-01

    Measurements with a dual fission chamber have been made of the ²³⁵U fission rate in the neutron field of ²⁵²Cf calibration sources to investigate the effect of scattering from source encapsulation. The fission chamber, provided by the US National Bureau of Standards (NBS), is capable of high-precision absolute measurements. Neutron sources investigated include a Savannah River Lab. (SRL) 100-series source

  7. Selection of quaternary ammonium bromides for use in zinc/bromine cells

    NASA Astrophysics Data System (ADS)

    Cathro, K. J.; Cedzynska, K.; Constable, D. C.; Hoobin, P. M.

    Various cyclic and aliphatic quaternary ammonium bromides have been tested for use in zinc/bromine battery electrolytes. No single compound can be used over the temperature range 0-50°C due to crystallization of solid materials from either the polybromide or the aqueous phases. Electrolytes containing mixtures of quaternary ammonium bromides can avoid this problem of crystallization, and electrolytes containing 1:1 mixtures of N-methyl- N-ethylpyrrolidinium bromide with either N-methyl- N-ethylmorpholinium bromide or dimethylethylpropylammonium bromide have proved acceptable. The performance of a small zinc/bromine cell using electrolytes prepared from various quaternary ammonium bromides is described.

  8. SOCIAL GROUP FISSION AND GENE DYNAMICS AMONG BLACK-TAILED PRAIRIE DOGS

    E-print Network

    Foltz, David W.

    SOCIAL GROUP FISSION AND GENE DYNAMICS AMONG BLACK-TAILED PRAIRIE DOGS (CYNOMYS LUDOVICIANUS fission. Key words: coancestry, competition, cooperation, Cynomys ludovicianus, dispersal, fission, gene al. 1990). Black-tailed prairie dogs (Cynomys ludovicianus; hereafter, simply ``prairie dogs

  9. Fission Product Data Measured at Los Alamos for Fission Spectrum and Thermal Neutrons on 239Pu, 235U, 238U

    NASA Astrophysics Data System (ADS)

    Selby, H. D.; Mac Innes, M. R.; Barr, D. W.; Keksis, A. L.; Meade, R. A.; Burns, C. J.; Chadwick, M. B.; Wallstrom, T. C.

    2010-12-01

    We describe measurements of fission product data at Los Alamos that are important for determining the number of fissions that have occurred when neutrons are incident on plutonium and uranium isotopes. The fission-spectrum measurements were made using a fission chamber designed by the National Institute for Standards and Technology (NIST) in the BIG TEN critical assembly, as part of the Inter-laboratory Liquid Metal Fast Breeder Reactor (LMFBR) Reaction Rate (ILRR) collaboration. The thermal measurements were made at Los Alamos' Omega West Reactor. A related set of measurements were made of fission-product ratios (so-called R-values) in neutron environments provided by a number of Los Alamos critical assemblies that range from having average energies causing fission of 400-600 keV (BIG TEN and the outer regions of the Flattop-25 assembly) to higher energies (1.4-1.9 MeV) in the Jezebel, and in the central regions of the Flattop-25 and Flattop-Pu, critical assemblies. From these data we determine ratios of fission product yields in different fuel and neutron environments (Q-values) and fission product yields in fission spectrum neutron environments for 99Mo, 95Zr, 137Cs, 140Ba, 141,143Ce, and 147Nd. Modest incident-energy dependence exists for the 147Nd fission product yield; this is discussed in the context of models for fission that include thermal and dynamical effects. The fission product data agree with measurements by Maeck and other authors using mass-spectrometry methods, and with the ILRR collaboration results that used gamma spectroscopy for quantifying fission products. We note that the measurements also contradict earlier 1950s historical Los Alamos estimates by ˜5-7%, most likely owing to self-shielding corrections not made in the early thermal measurements. Our experimental results provide a confirmation of the England-Rider ENDF/B-VI evaluated fission-spectrum fission product yields that were carried over to the ENDF/B-VII.0 library, except for 99Mo where the present results are about 4%-relative higher for neutrons incident on 239Pu and 235U. Additionally, our results illustrate the importance of representing the incident energy dependence of fission product yields over the fast neutron energy range for high-accuracy work, for example the 147Nd from neutron reactions on plutonium. An upgrade to the ENDF library, for ENDF/B-VII.1, based on these and other data, is described in a companion paper to this work.

  10. Fission neutron spectra measurements at LANSCE - status and plans

    SciTech Connect

    Haight, Robert C [Los Alamos National Laboratory; Noda, Shusaku [Los Alamos National Laboratory; Nelson, Ronald O [Los Alamos National Laboratory; O' Donnell, John M [Los Alamos National Laboratory; Devlin, Matt [Los Alamos National Laboratory; Chatillon, Audrey [CEA-FRANCE; Granier, Thierry [CEA-FRANCE; Taieb, Julien [CEA-FRANCE; Laurent, Benoit [CEA-FRANCE; Belier, Gilbert [CEA-FRANCE; Becker, John A [LLNL; Wu, Ching - Yen [LLNL

    2009-01-01

    A program to measure fission neutron spectra from neutron-induced fission of actinides is underway at the Los Alamos Neutron Science Center (LANSCE) in a collaboration among the CEA laboratory at Bruyeres-le-Chatel, Lawrence Livermore National Laboratory and Los Alamos National Laboratory. The spallation source of fast neutrons at LANSCE is used to provide incident neutron energies from less than 1 MeV to 100 MeV or higher. The fission events take place in a gas-ionization fission chamber, and the time of flight from the neutron source to that chamber gives the energy of the incident neutron. Outgoing neutrons are detected by an array of organic liquid scintillator neutron detectors, and their energies are deduced from the time of flight from the fission chamber to the neutron detector. Measurements have been made of the fission neutrons from fission of {sup 235}U, {sup 238}U, {sup 237}Np and {sup 239}Pu. The range of outgoing energies measured so far is from 1 MeV to approximately 8 MeV. These partial spectra and average fission neutron energies are compared with evaluated data and with models of fission neutron emission. Results to date will be presented and a discussion of uncertainties will be given in this presentation. Future plans are to make significant improvements in the fission chambers, neutron detectors, signal processing, data acquisition and the experimental environment to provide high fidelity data including mea urements of fission neutrons below 1 MeV and improvements in the data above 8 MeV.

  11. Pairing-induced speedup of nuclear spontaneous fission

    E-print Network

    Jhilam Sadhukhan; J. Dobaczewski; W. Nazarewicz; J. A. Sheikh; A. Baran

    2014-10-06

    Collective inertia is strongly influenced at the level crossing at which quantum system changes diabatically its microscopic configuration. Pairing correlations tend to make the large-amplitude nuclear collective motion more adiabatic by reducing the effect of those configuration changes. Competition between pairing and level crossing is thus expected to have a profound impact on spontaneous fission lifetimes. To elucidate the role of nucleonic pairing on spontaneous fission, we study the dynamic fission trajectories of $^{264}$Fm and $^{240}$Pu using the state-of-the-art self-consistent framework. We employ the superfluid nuclear density functional theory with the Skyrme energy density functional SkM$^*$ and a density-dependent pairing interaction. Along with shape variables, proton and neutron pairing correlations are taken as collective coordinates. The collective inertia tensor is calculated within the nonperturbative cranking approximation. The fission paths are obtained by using the least action principle in a four-dimensional collective space of shape and pairing coordinates. Pairing correlations are enhanced along the minimum-action fission path. For the symmetric fission of $^{264}$Fm, where the effect of triaxiality on the fission barrier is large, the geometry of fission pathway in the space of shape degrees of freedom is weakly impacted by pairing. This is not the case for $^{240}$Pu where pairing fluctuations restore the axial symmetry of the dynamic fission trajectory. The minimum-action fission path is strongly impacted by nucleonic pairing. In some cases, the dynamical coupling between shape and pairing degrees of freedom can lead to a dramatic departure from the static picture. Consequently, in the dynamical description of nuclear fission, particle-particle correlations should be considered on the same footing as those associated with shape degrees of freedom.

  12. Pairing-induced speedup of nuclear spontaneous fission

    NASA Astrophysics Data System (ADS)

    Sadhukhan, Jhilam; Dobaczewski, J.; Nazarewicz, W.; Sheikh, J. A.; Baran, A.

    2014-12-01

    Background: Collective inertia is strongly influenced at the level crossing at which the quantum system changes its microscopic configuration diabatically. Pairing correlations tend to make the large-amplitude nuclear collective motion more adiabatic by reducing the effect of these configuration changes. Competition between pairing and level crossing is thus expected to have a profound impact on spontaneous fission lifetimes. Purpose: To elucidate the role of nucleonic pairing on spontaneous fission, we study the dynamic fission trajectories of 264Fm and 240Pu using the state-of-the-art self-consistent framework. Methods: We employ the superfluid nuclear density functional theory with the Skyrme energy density functional SkM* and a density-dependent pairing interaction. Along with shape variables, proton and neutron pairing correlations are taken as collective coordinates. The collective inertia tensor is calculated within the nonperturbative cranking approximation. The fission paths are obtained by using the least action principle in a four-dimensional collective space of shape and pairing coordinates. Results: Pairing correlations are enhanced along the minimum-action fission path. For the symmetric fission of 264Fm, where the effect of triaxiality on the fission barrier is large, the geometry of the fission pathway in the space of the shape degrees of freedom is weakly impacted by pairing. This is not the case for 240Pu, where pairing fluctuations restore the axial symmetry of the dynamic fission trajectory. Conclusions: The minimum-action fission path is strongly impacted by nucleonic pairing. In some cases, the dynamical coupling between shape and pairing degrees of freedom can lead to a dramatic departure from the static picture. Consequently, in the dynamical description of nuclear fission, particle-particle correlations should be considered on the same footing as those associated with shape degrees of freedom.

  13. Excitation energy dependence of fission in the mercury region

    E-print Network

    J. D. McDonnell; W. Nazarewicz; J. A. Sheikh; A. Staszczak; M. Warda

    2014-06-26

    Background: Recent experiments on beta-delayed fission reported an asymmetric mass yield in the neutron-deficient nucleus 180Hg. Earlier experiments in the mass region A=190-200 close to the beta-stability line, using the (p,f) and (\\alpha,f) reactions, observed a more symmetric distribution of fission fragments. While the beta-delayed fission of 180Hg can be associated with relatively low excitation energy, this is not the case for light-ion reactions, which result in warm compound nuclei. Purpose: To elucidate the roles of proton and neutron numbers and excitation energy in determining symmetric and asymmetric fission yields, we compute and analyze the isentropic potential energy surfaces of 174,180,198Hg and 196,210Po. Methods: We use the finite-temperature superfluid nuclear density functional theory, for excitation energies up to E*=30MeV and zero angular momentum. For our theoretical framework, we consider the Skyrme energy density functional SkM* and a density-dependent pairing interaction. Results: For 174,180Hg, we predict fission pathways consistent with asymmetric fission at low excitation energies, with the symmetric fission pathway opening very gradually as excitation energy is increased. For 198Hg and 196Po, we expect the nearly-symmetric fission channel to dominate. 210Po shows a preference for a slightly asymmetric pathway at low energies, and a preference for a symmetric pathway at high energies. Conclusions: Our self-consistent theory suggests that excitation energy weakly affects the fission pattern of the nuclei considered. The transition from the asymmetric fission in the proton-rich nuclei to a more symmetric fission in the heavier isotopes is governed by the shell structure of pre-scission configurations.

  14. Fission track age of Transantarctic Mountain microtektites

    NASA Astrophysics Data System (ADS)

    Folco, L.; Bigazzi, G.; D'Orazio, M.; Balestrieri, M. L.

    2011-05-01

    We determined the fission track age of Transantarctic Mountain microtektites. The plateau method yielded a formation age of 0.85 ± 0.17 Ma. This age overlaps within error with that of the catastrophic impact that produced the Australasian tektite-microtektite strewn field ca. 0.8 Ma ago. This provides further evidence that Transantarctic Mountain microtektites belong to the Australasian tektite-microtektite strewn field, as previously suggested on the basis of geochemical evidence, Sr-Nd isotope systematics and poorly resolved radiometric data.

  15. Site of Action of Certain Antibacterial Heterocyclic Quaternary Ammonium Compounds

    PubMed Central

    Cox, W. A.

    1965-01-01

    The site of action of related mono- and bis-quinaldinium compounds was investigated in Staphylococcus aureus and Bacillus megaterium. The effects of these compounds on cell morphology and on protoplast formation and fragility were studied, and the distribution of C14-labeled quinaldinium compound in cell fractions was measured. The latter studies showed that a major part of the quaternary compound penetrates the cell, leaving a very small quantity associated with the cell wall. Similar antibacterial effects were seen with both the mono- and bis-quinaldinium compounds studied, and these effects were comparable with antibacterial properties of known cationic surface-active antibacterial agents. Images Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 PMID:4956041

  16. Evidences for Neogene-Quaternary tectonics in Svalbard

    NASA Astrophysics Data System (ADS)

    Cianfarra, Paola; Salvini, Francesco

    2013-04-01

    Svalbard locates along the De Geer Transform Fault that separates the kinematics of North Atlantic and Arctic Ocean and are a continental rise along the North Atlantic portion of this transform. A fold and thrust belt of Paleogene age boards the Western margin of the Spitsbergen with a NNW-SSE trend. In the '60s the West - Spitsbergen fold and trust belt was related to the relative movements between Laurentia and Eurasia. Specifically, it was regarded to be a transpressive orogen developed at the intra-continental De Geer Transform margin between the Barents and the Greenland Shelves. This setting was suggested by the necessity of a continental transform off the western margin of Svalbard needed to restore the relative openings of the North Atlantic-Arctic Ocean basins, and the Paleogene age of the fold-belt. Later structural studies in other areas of Svalbard suggested that convergent tectonics have been prevailing during much of the fold and thrust development. However this belt can hardly be regarded as a classical orogen resulting from an active continental margin for the lack of evidence for subduction, synorogenic magmatism, metamorphism or a thickened crust. On the other hand, it would be difficult to merely relate this fold and thrust belt to the De Geer Transform Fault. According to Authors a transform fault should produce structures with vergence away from the fault on both sides, whereas the found direction of tectonic transport in North Greenland is the same as in Spitsbergen, i.e. to the E and NE. In this way the transform separation of North-Greenland and Spitsbergen should postdate the formation of the Tertiary North-Greenland and Spitsbergen fold and trust belt. This rises the question on possible Neogene-Quaternary tectonics in Spitsbergen. Evidence for this younger tectonics includes the occurrence of Quaternary volcanism and thermal springs in the northern part of Spitsbergen and the moderate seismicity in Nordaustlandet. Other clues supporting a recent tectonics derive from the analysis of satellite images and air photos, including the glacier and fluvial drainage suggesting a strong tectonic control. Moreover some authors have found in Ny Alesund an uplift rate from GPS measurements higher than those predicted by postglacial rebound models, again suggesting a tectonic contribution. Preliminary results from field work in the Brogger peninsula confirmed the presence of Neogene-Quaternary tectonics. Marine terraces and fluvio-glacial deposits show several N-S elongated steps along the northern projection of N-S trending faults cutting the Meso-Cenozoic rocks. N-S trending faults have been systematically found in Devonian to Tertiary rocks. These faults are characterised by right-lateral, strike-slip movements and the presence of near surface to sub aerial mineralizations on their surfaces, including kinematic indicators. N-S faults with the same kinematics show the presence of deformed Quaternary clastic, unconsolidated deposits within their shear zones. All the found brittle deformation evidence are compatible with the kinematics of the recent activity of the De Geer Transform Fault.

  17. Late Quaternary folding of coral reef terraces, Barbados

    NASA Astrophysics Data System (ADS)

    Taylor, Frederick W.; Mann, Paul

    1991-02-01

    Uplifted late Ouaternary coral reefs on the island of Barbados record folding of the emergent crest of the Lesser Antilles accretionary prism (Barbados Ridge complex) since ca. 1 Ma. Three northeast striking folds are defined by systematic changes in altitudes in the crest of First High Cliff, a mostly constructional reef terrace about 125 ka, and Second High Cliff, a partially erosional reef terrace about 500 ka. The folds have wavelengths of 6 to 8 km and fold axes extend about 10 km. The largest anticline rises to the northeast, where it has been breached by erosion exposing highly deformed Eocene to lower Miocene rocks of the Scotland District. Uplift rates based on heights of the last interglacial First High Cliff range from 0.07 to 0.44 mm/yr. Quaternary folding on Barbados indicates that the crest of the accretionary prism continues to be an active fold belt undergoing northwestsoutheast shortening.

  18. Programmed pore architectures in modular quaternary metal-organic frameworks.

    PubMed

    Liu, Lujia; Konstas, Kristina; Hill, Matthew R; Telfer, Shane G

    2013-11-27

    To generate metal-organic frameworks (MOFs) that are complex and modular yet well ordered, we present a strategy employing a family of three topologically distinct linkers that codes for the assembly of a highly porous quaternary MOF. By introducing substituted analogues of the ligands, a set of eight isoreticular frameworks is delivered, with the MOF structure systematically varied while the topology is maintained. To combat randomness and disorder, the substitution patterns of the ligands are designed to be compatible with their crystallographic site symmetries. MOFs produced in this way feature "programmed pores"--multiple functional groups compartmentalized in a predetermined array within a periodic lattice--and are capable of complex functional behavior. In these examples unconventional CO2 sorption trends, including capacity enhancements close to 100%, emerge from synergistic effects. Future PP-MOFs may be capable of enzyme-like heterogeneous catalysis and ultraselective adsorption. PMID:24180695

  19. Quaternary prevention, an answer of family doctors to overmedicalization.

    PubMed

    Jamoulle, Marc

    2015-02-01

    In response to the questioning of Health Policy and Management (HPAM) by colleagues on the role of rank and file family physicians in the same journal, the author, a family physician in Belgium, is trying to highlight the complexity and depth of the work of his colleagues and their contribution to the understanding of the organization and economy of healthcare. It addresses, in particular, the management of health elements throughout the ongoing relationship of the family doctor with his/her patients. It shows how the three dimensions of prevention, clearly included in the daily work, are complemented with the fourth dimension, quaternary prevention or prevention of medicine itself, whose understanding could help to control the economic and human costs of healthcare. PMID:25674569

  20. Neogene-Quaternary Middle Atlas basaltic province (Morocco): Isotope constraints

    NASA Astrophysics Data System (ADS)

    Bosch, D.; Maury, R.; El Azzouzi, M.; Parat, F.; Bellon, H.

    2012-04-01

    The Middle Atlas basaltic province is the largest and youngest volcanic field in Morocco. A hundred well-preserved strombolian cones and maars emitted numerous mafic lava flows which cover a surface of ca. 960 km2 and range in composition from nephelinites to subalkaline basalts through basanites and alkali basalts. We have investigated the Sr, Nd and Pb isotopic compositions and trace element features of these mafic lavas. Nephelinites represent only 1.2 % of the total surface of volcanic units; they form small monogenic volcanoes built during the Middle and Late Miocene (16.25 - 5.87 Ma) and the Plio-Quaternary (3.92 - 0.67 Ma). The three other types are exclusively Plio-Quaternary (3.77 - 0.60 Ma). Basanites cover 22.5 % of the volcanic field area, and generally overlie the more widespread alkali basaltic flows (68.5 % of the plateau surface). Finally, subalkaline basalts form the El Koudiate cone and associated flows (7.8 % of the surface of the volcanic units) and their petrographic, trace element and isotopic features suggest that they derive from the contamination of alkali basaltic magmas by the upper continental crust. Nephelinites, basanites and alkali basalts have a distinct HIMU flavour (206Pb/204Pb up to 20.44) which is similar to that of metasomatic clinopyroxenes from associated spinel-facies peridotite xenoliths (Wittig et al., 2010). Most nephelinites have rather unradiogenic 87Sr/86Sr ratios close to 0.7032, which do not change through time. Those of the other types are slightly higher (up to 0.7037) and tend to increase temporally, and also from basanites to alkali basalts. These geochemical features allow us to discuss the relative contributions of the African continental crust and lithospheric mantle and that of the underlying asthenosphere to the genesis of the Middle Atlas magmas.

  1. Late Quaternary slip on the Santa Cruz Island fault, California

    USGS Publications Warehouse

    Pinter, N.; Lueddecke, S.B.; Keller, E.A.; Simmons, K.R.

    1998-01-01

    The style, timing, and pattern of slip on the Santa Cruz Island fault were investigated by trenching the fault and by analysis of offset late Quaternary landforms. A trench excavated across the fault at Christi Beach, on the western coast of the island, exposed deformation of latest Pleistocene to Holocene sediments and pre-Quaternary rocks, recording repeated large-magnitude rupture events. The most recent earthquake at this site occurred ca. 5 ka. Coastal terraces preserved on western Santa Cruz Island have been dated using the uranium-series technique and by extrapolation using terrace elevations and the eustatic record. Offset of terraces and other landforms indicates that the Santa Cruz Island fault is predominantly left lateral, having a horizontal slip rate of not more than 1.1 mm/yr and probably about 0.8 mm/yr. The fault also has a smaller reverse component, slipping at a rate of between 0.1 and 0.2 mm/yr. Combined with measurements of slip per event, this information suggests a long-term average recurrence interval of at least 2.7 k.y. and probably 4-5 k.y., and average earthquake magnitudes of Mw 7.2-7.5. Sense of slip, recurrence interval, and earthquake magnitudes calculated here for the Santa Cruz Island fault are very similar to recent results for other faults along the southern margin of the western Transverse Range, including the Malibu Coast fault, the Santa Monica fault, the Hollywood fault, and the Raymond fault, supporting the contention that these faults constitute a continuous and linked fault system, which is characterized by large but relatively infrequent earthquakes.

  2. Quaternary incised valleys in southern Brazil coastal zone

    NASA Astrophysics Data System (ADS)

    Weschenfelder, Jair; Baitelli, Ricardo; Corrêa, Iran C. S.; Bortolin, Eduardo C.; dos Santos, Cristiane B.

    2014-11-01

    High-resolution seismic records obtained in the Rio Grande do Sul coastal zone, southern Brazil, revealed that prominent valleys and channels developed in the area before the installation of actual coastal plain. Landwards, the paleoincisions can be linked with the present courses of the main river dissecting the area. Oceanwards, they can be linked with related features previously recognized in the continental shelf and slope by means of seismic and morphostructural studies. Based mainly on seismic, core data and geologic reasoning, it can be inferred that the coastal valleys were incised during forced regression events into the coastal prism deposited during previous sea level highstand events of the Quaternary. Seismic data has revealed paleovalleys up to 10 km wide and, in some places, infilled with up to 40 m thick of sediments. The results indicated two distinct periods of cut-and-fill events in the Patos Lagoon area. The filling of the younger incision system is mainly Holocene and its onset is related to the last main regressive event of the Pleistocene, when the sea level fell about 130 m below the actual position. The older incision and filling event is related to the previous regressive-transgressive events of the Middle and Late Pleistocene. The fluvial discharge fed delta systems on the shelf edge during the sea level lowstands. The subsequent transgressions drowned the incised drainage, infilling it and closing the inlets formerly connecting the coastal river to the ocean. The incised features may have played a significant role on the basin-margin architecture, facies distribution and accommodation space during the multitude of up and down sea level events of the Quaternary.

  3. Are seawater Sr/Ca variations preserved in Quaternary foraminifera?

    SciTech Connect

    Stoll, H.M.; Schrag, D.P.; Clemens, S.C.

    1999-11-01

    High precision measurements of Sr/Ca in planktonic foraminifera for the last 150 ka reveal Sr/Ca variations of up to 12% on glacial/interglacial time scales. Although records showing the largest variations appear to be strongly influenced by selective dissolution, other records show Sr/Ca variations of 3--5% that do not covary with indicators of dissolution intensity and that are reproduced in sites of contrasting Quaternary dissolution histories. These systematic variations are characterized by high Sr/Ca ratios during glacial maxima, followed by steep decreases during deglaciation and gradual increases through interstadial periods, closely following {delta}{sup 18}O curves. Foraminiferal Sr/Ca variations may reflect changes in the Sr/Ca ratio of seawater, or they may be due to kinetically or biologically induced changes in Sr partitioning. Coupled numerical models of the Sr and Ca budgets of the ocean reveal that sea level changes, together with large changes in river fluxes and carbonate accumulation rates, can produce seawater Sr/Ca variations that approximate both the shape and amplitude of foraminiferal Sr/Ca variations. However, such extreme changes in river and carbonate fluxes conflict with existing data on carbonate accumulation rates and Sr isotopic constraints on the magnitude of variations in the river flux. Smaller variations (1--3%) in the Sr/Ca ratio of seawater likely characterize Quaternary glacial cycles. Changes in Sr partitioning due to glacial-interglacial changes in the carbonate ion concentration and other environmental factors likely produce additional variation in the Sr/Ca record of planktonic foraminifera.

  4. Fission energy program of the US Department of Energy, FY 1981

    SciTech Connect

    Ferguson, Robert L.

    1980-03-01

    Information is presented concerning the National Energy Plan and fission energy policy; fission energy program management; converter reactor systems; breeder reactor systems; and special nuclear evaluations and systems.

  5. Mitochondrial Morphological Features Are Associated with Fission and Fusion Events

    PubMed Central

    Martin, Katie R.; Hlavacek, William S.; MacKeigan, Jeffrey P.

    2014-01-01

    Mitochondria are dynamic organelles that undergo constant remodeling through the regulation of two opposing processes, mitochondrial fission and fusion. Although several key regulators and physiological stimuli have been identified to control mitochondrial fission and fusion, the role of mitochondrial morphology in the two processes remains to be determined. To address this knowledge gap, we investigated whether morphological features extracted from time-lapse live-cell images of mitochondria could be used to predict mitochondrial fate. That is, we asked if we could predict whether a mitochondrion is likely to participate in a fission or fusion event based on its current shape and local environment. Using live-cell microscopy, image analysis software, and supervised machine learning, we characterized mitochondrial dynamics with single-organelle resolution to identify features of mitochondria that are predictive of fission and fusion events. A random forest (RF) model was trained to correctly classify mitochondria poised for either fission or fusion based on a series of morphological and positional features for each organelle. Of the features we evaluated, mitochondrial perimeter positively correlated with mitochondria about to undergo a fission event. Similarly mitochondrial solidity (compact shape) positively correlated with mitochondria about to undergo a fusion event. Our results indicate that fission and fusion are positively correlated with mitochondrial morphological features; and therefore, mitochondrial fission and fusion may be influenced by the mechanical properties of mitochondrial membranes. PMID:24733410

  6. Measurement of fission product gases in the atmosphere

    Microsoft Academic Search

    W. R. Schell; M. J. Tobin; D. J. Marsan; C. W. Schell; J. Vives-Batlle; S. R. Yoon

    1997-01-01

    The ability to quickly detect and assess the magnitude of releases of fission-produced radioactive material is of significant importance for ongoing operations of any conventional nuclear power plant or other activities with a potential for fission product release. In most instances, the control limits for the release of airborne radioactivity are low enough to preclude direct air sampling as a

  7. Fission foil detector calibrations with high energy protons

    NASA Technical Reports Server (NTRS)

    Benton, E. V.; Frank, A. L.

    1995-01-01

    Fission foil detectors (FFD's) are passive devices composed of heavy metal foils in contact with muscovite mica films. The heavy metal nuclei have significant cross sections for fission when irradiated with neutrons and protons. Each isotope is characterized by threshold energies for the fission reactions and particular energy-dependent cross sections. In the FFD's, fission fragments produced by the reactions are emitted from the foils and create latent particle tracks in the adjacent mica films. When the films are processed surface tracks are formed which can be optically counted. The track densities are indications of the fluences and spectra of neutrons and/or protons. In the past, detection efficiencies have been calculated using the low energy neutron calibrated dosimeters and published fission cross sections for neutrons and protons. The problem is that the addition of a large kinetic energy to the (n,nucleus) or (p,nucleus) reaction could increase the energies and ranges of emitted fission fragments and increase the detector sensitivity as compared with lower energy neutron calibrations. High energy calibrations are the only method of resolving the uncertainties in detector efficiencies. At high energies, either proton or neutron calibrations are sufficient since the cross section data show that the proton and neutron fission cross sections are approximately equal. High energy proton beams have been utilized (1.8 and 4.9 GeV, 80 and 140 MeV) for measuring the tracks of fission fragments emitted backward and forward.

  8. Fission-track ages from the Precambrian of Shropshire.

    USGS Publications Warehouse

    Naeser, C.W.; Toghill, P.; Ross, R.J., Jr.

    1982-01-01

    Four samples of Longmyndian and Uriconian strata from S of Shrewsbury, England have been processed for apatite and/or zircon fission-track ages. The resultant ages illustrate how depth of burial may affect fission-track ages. The analytical procedures followed were as described in Naeser (1979).-from Authors

  9. Telomere Regulation During the Cell Cycle in Fission Yeast

    PubMed Central

    Moser, Bettina A.; Chang, Ya-Ting; Nakamura, Toru M.

    2015-01-01

    The fission yeast Schizosaccharomyces pombe has emerged as a useful model organism to study telomere maintenance mechanisms. In this chapter, we provide detailed protocols for quantitative ChIP and BrdU incorporation analyses to investigate how fission yeast telomeres are regulated during the cell cycle by utilizing cdc25-22 synchronized cell cultures. PMID:24906327

  10. Phase 1 space fission propulsion system testing and development progress

    Microsoft Academic Search

    Melissa van Dyke; Mike Houts; Tom Godfroy; Ricky Dickens; David Poston; Rick Kapernick; Bob Reid; Pat Salvail; Peter Ring

    2002-01-01

    Successful development of space fission systems requires an extensive program of affordable and realistic testing. In addition to tests related to design\\/development of the fission system, realistic testing of the actual flight unit must also be performed. If the system is designed to operate within established radiation damage and fuel burn up limits while simultaneously being designed to allow close

  11. Nuclear Design of the HOMER15 Mars Surface Fission Reactor

    Microsoft Academic Search

    David I

    2002-01-01

    The next generation of robotic missions to Mars will most likely require robust power sources in the range of 3 to 20 kWe. Fission systems are well suited to provide safe, reliable, and economic power within this range. The goal of this study is to design a compact, low-mass fission system that meets Mars surface power requirements, while maintaining a

  12. Fission Dynamics in the Four-Dimensional Deformation Space

    NASA Astrophysics Data System (ADS)

    Pomorski, Krzysztof; Bartel, Johann

    A four-dimensional deformation space adapted to describe the fission dynamics of hot, rotating nuclei is proposed. The deformation coordinates consisting of the elongation, neck formation, left-right asymmetry and nonaxiality result in fission barriers much lower and thiner than those obtained in the spherical-harmonics expansion using the same number of deformation parameters.

  13. Fission product behavior in the Molten Salt Reactor Experiment

    Microsoft Academic Search

    E. L. Compere; S. S. Kirslis; E. G. Bohlmann; F. F. Blankenship; W. R. Grimes

    1975-01-01

    Essentially all the fission product data for numerous and varied samples ; taken during operation of the Molten Salt Reactor Experiment or as part of the ; examination of specimens removed after particular phases of operation are ; reported, together with the appropriate inventory or other basis of comparison, ; and relevant reactor parameters and conditions. Fission product behavior fell

  14. A scintillating fission detector for neutron flux measurements

    Microsoft Academic Search

    Sy Stange; Ernst I Esch; Eric A Burgett; Iain May; Ross E Muenchausen; Felicia Taw; Fredrik K Tovesson

    2010-01-01

    Neutron flux monitors are commonly used for a variety of nuclear physics applications. A scintillating neutron detector, consisting of a liquid scintillator loaded with fissionable material, has been developed, characterized, and tested in the beam line at the Los Alamos Neutron Science Center, and shows a significant improvement in neutron sensitivity compared with a conventional fission chamber. Recent research on

  15. Compound Nucleus Reactions in LENR, Analogy to Uranium Fission

    Microsoft Academic Search

    Heinrich Hora; George Miley; Karl Philberth

    2008-01-01

    The discovery of nuclear fission by Hahn and Strassmann was based on a very rare microanalytical result that could not initially indicate the very complicated details of this most important process. A similarity is discussed for the low energy nuclear reactions (LENRs) with analogies to the yield structure found in measurements of uranium fission. The LENR product distribution measured earlier

  16. High efficiency organic multilayer photodetectors based on singlet exciton fission

    Microsoft Academic Search

    J. Lee; P. Jadhav; M. A. Baldo

    2009-01-01

    We employ an exciton fission process that converts one singlet exciton into two triplet excitons to increase the quantum efficiency of an organic multilayer photodetector beyond 100%. The photodetector incorporates ultrathin alternating donor-acceptor layers of pentacene and C60, respectively. By comparing the quantum efficiency after separate pentacene and C60 photoexcitation we find that singlet exciton fission in pentacene enhances the

  17. Efficient singlet fission discovered in a disordered acene film.

    PubMed

    Roberts, Sean T; McAnally, R Eric; Mastron, Joseph N; Webber, David H; Whited, Matthew T; Brutchey, Richard L; Thompson, Mark E; Bradforth, Stephen E

    2012-04-11

    Singlet exciton fission is a process that occurs in select organic semiconductors and entails the splitting of a singlet excited state into two lower triplet excitons located on adjacent chromophores. Research examining this phenomenon has recently seen a renaissance due to the potential to exploit singlet fission within the context of organic photovoltaics to prepare devices with the ability to circumvent the Shockley-Queisser limit. To date, high singlet fission yields have only been reported for crystalline or polycrystalline materials, suggesting that molecular disorder inhibits singlet fission. Here, we report the results of ultrafast transient absorption and time-resolved emission experiments performed on 5,12-diphenyl tetracene (DPT). Unlike tetracene, which tends to form polycrystalline films when vapor deposited, DPT's pendant phenyl groups frustrate crystal growth, yielding amorphous films. Despite the high level of disorder in these films, we find that DPT exhibits a surprisingly high singlet fission yield, with 1.22 triplets being created per excited singlet. This triplet production occurs over two principal time scales, with ~50% of the triplets appearing within 1 ps after photoexcitation followed by a slower phase of triplet growth over a few hundred picoseconds. To fit these kinetics, we have developed a model that assumes that due to molecular disorder, only a subset of DPT dimer pairs adopt configurations that promote fission. Singlet excitons directly excited at these sites can undergo fission rapidly, while singlet excitons created elsewhere in the film must diffuse to these sites to fission. PMID:22432700

  18. Singlet exciton fission in pure and doped anthracene

    Microsoft Academic Search

    K. von Burg; I. Zschokke-Gränacher

    1979-01-01

    On the basis of the kinetic model by Merrifield for triplet exciton fusion in molecular crystals, we have derived an expression which describes the reciprocal process, i.e., the anisotropy of the prompt fluorescence in the presence of singlet exciton fission in a magnetic field. For the first time a thorough comparison of Merrifield's theory with singlet exciton fission experiments is

  19. Singlet fission in pentacene through multiple exciton quantum states

    Microsoft Academic Search

    Zhiyong Zhang; Paul Zimmerman; Charles Musgrave

    2010-01-01

    Multi-exciton generation (MEG) has been reported for several materials and may dramatically increase solar cell efficiency. Singlet fission is the molecular analogue of MEG and has been observed in various systems, including tetracene and pentacene, however, no fundamental mechanism for singlet fission has yet been described, although it may govern MEG processes in a variety of materials. Because photoexcited states

  20. Singlet exciton fission in pure and doped anthracene

    Microsoft Academic Search

    K. von Burg

    1979-01-01

    On the basis of the kinetic model by Merrifield for triplet exciton fusion in molecular crystals, we have derived an expression which describes the reciprocal process, i.e., the anisotropy of the prompt fluorescence in the presence of singlet exciton fission in a magnetic field. For the first time a thorough comparison of Merrifield’s theory with singlet exciton fission experiments is

  1. Fission Gas Release from Uranium Heated in Carbon Dioxide

    Microsoft Academic Search

    Kiyoaki TAKETANI; Katsuichi IKAWA

    1965-01-01

    An experiment to predict the amount of fission gas release from U heated in CO2 was made in connection with the safely evaluation of the Tokai Atomic Power Reactor. Fission gas release from slightly irradiated U pieces was measured as a function of percent oxidation, and it was found that the percent release was proportional to the percent oxidation. The

  2. Fission gas release in LWR fuel measured during nuclear operation

    Microsoft Academic Search

    A. D. Appelhans; E. Skattum; D. J. Osetek

    1980-01-01

    A series of fuel behavior experiments are being conducted in the Heavy Boiling Water Reactor in Halden, Norway, to measure the release of Xe, Kr, and I fission products from typical light water reactor design fuel pellets. Helium gas is used to sweep the Xe and Kr fission gases out of two of the Instrumented Fuel Assembly 430 fuel rods

  3. Recent studies in heavy ion induced fission reactions

    Microsoft Academic Search

    R. K. Choudhury

    2001-01-01

    Nuclear fission process involves large scale shape changes of the nucleus, while it evolves from a nearly spherical configuration to two separated fission fragments. The dynamics of these shape changes in the nuclear many body system is governed by a strong interplay of the collective and single particle degrees of freedom. With the availability of heavy ion accelerators, there has

  4. Chemical factors affecting fission product transport in severe LMFBR accidents

    SciTech Connect

    Wichner, R.P.; Jolley, R.L.; Gat, U.; Rodgers, B.R.

    1984-10-01

    This study was performed as a part of a larger evaluation effort on LMFBR accident, source-term estimation. Purpose was to provide basic chemical information regarding fission product, sodium coolant, and structural material interactions required to perform estimation of fission product transport under LMFBR accident conditions. Emphasis was placed on conditions within the reactor vessel; containment vessel conditions are discussed only briefly.

  5. Development Progress in Phase 1 Fission Propulsion Systems

    NASA Technical Reports Server (NTRS)

    Houts, Michael G.; VanDyke, Melissa; Godfroy, Tom; Martin, Jim; Dickens, Ricky; Pedersen, Kevin; Poston, David; Reid, Bob; Lipinski, Ron; Wright, Steve; Lenard, Roger

    2000-01-01

    Phase 1 fission propulsion systems are those fission propulsion systems that are highly testable and require no development of nuclear fuels or materials. The systems can be developed without new or significantly modified facilities, have adequate performance for numerous missions of interest, and demonstrate technologies and programmatics that are traceable to Phase 2 and Phase 3 systems. Phase 1 fission propulsion systems focus on safety, cost and schedule. Phase 1 flight units can be tested at full thrust using resistance heaters to simulate heat from fission. The development and use of Phase 1 systems will help enable Phase 2 or Phase 3 fission propulsion systems capable of giving rapid, affordable access to any point in the solar system. A Phase 1 fission propulsion system under development at the Marshall Space Flight Center (MSFC) in collaboration with individuals from Department of Energy Laboratories and industry is the Safe Affordable Fission Engine (SAFE). The propellant energy source of a 30 kW SAFE unit (SAFE-30) is being fabricated, and will begin testing at MSFC in FY00. The conceptual design of a 300 kW SAFE unit (SAFE-300)is nearing completion. Experiments have been performed on both SAFE-30 and SAFE-300 components. Module tests have confirmed the performance potential of the SAFE series of propulsion systems. This paper will report on the development status of the Phase 1 SAFE fission propulsion system.

  6. Predetonation probability of a fission-bomb core

    Microsoft Academic Search

    B. Cameron Reed

    2010-01-01

    An undergraduate-level derivation of the probability that a uranium or plutonium fission bomb will suffer an uncontrolled predetonation due to neutrons liberated in spontaneous fissions in the fissile material is developed. Consistent with what was learned by Los Alamos bomb designers during World War II, it is shown why uncontrolled predetonation was not a problem for a U-235 bomb of

  7. Whole-rock uranium analysis by fission track activation

    NASA Technical Reports Server (NTRS)

    Weiss, J. R.; Haines, E. L.

    1974-01-01

    We report a whole-rock uranium method in which the polished sample and track detector are separated in a vacuum chamber. Irradiation with thermal neutrons induces uranium fission in the sample, and the detector records the integrated fission track density. Detection efficiency and geometric factors are calculated and compared with calibration experiments.

  8. Antibacterial properties of poly(quaternary ammonium) modified gold and titanium dioxide nanoparticles.

    PubMed

    Wan, Weijie; Yeow, John T W

    2012-06-01

    We report excellent antibacterial effect induced by amine-functionalized gold and titanium dioxide nanoparticles without external excitations. The idea originates from the excellent antibacterial property of quaternary ammonium salts. The effects of poly(quaternary ammonium) and polyacrylate sodium functional groups as nanoparticle surfactants are compared to show that poly(quaternary ammonium) functional groups are the main cause of the induced antibacterial effect. 99.999% of E. coli can be destructed in 10 minutes by simply mixing bacteria with nanoparticle dispersions. The effect of nanoparticle concentrations on the antibacterial property is evaluated. Time required to significantly suppress bacteria growth is studied. The result indicates that the excellent antibacterial property can be introduced to any nanomaterials by using poly(quaternary ammonium) functional groups as surfactants. The engineered nanoparticles can find enormous applications such as self-cleaning surfaces, waste water treatment, Lab-on-a-Chip devices and many more. PMID:22905506

  9. Map and data for Quaternary faults and folds in Washington state

    USGS Publications Warehouse

    Lidke, David J.; Johnson, Samuel Y.; McCrory, Patricia A.; Personius, Stephen F.; Nelson, Alan R.; Dart, Richard L.; Bradley, Lee-Ann; Haller, Kathleen M.; Machette, Michael N.

    2004-01-01

    The map shows faults and folds in Washington State that exhibit evidence of Quaternary deformation and includes data on timing of most recent movement, sense of movement, slip rate, and continuity of surface expression.

  10. The late Quaternary limnological history of Lake Kinneret (Sea of Galilee), Israel

    E-print Network

    Marco, Shmuel "Shmulik"

    The late Quaternary limnological history of Lake Kinneret (Sea of Galilee), Israel N. Hazana , M) during the Neogene­Quartenary periods. We reconstructed the limnological history (level and composition

  11. OMVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics (title change from A)

    SciTech Connect

    HAN,JUNG; FIGIEL,JEFFREY J.; PETERSEN,GARY A.; MYERS JR.,SAMUEL M.; CRAWFORD,MARY H.; BANAS,MICHAEL ANTHONY; HEARNE,SEAN JOSEPH

    2000-01-18

    We report the growth and characterization of quaternary AlGaInN. A combination of photoluminescence (PL), high-resolution x-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) characterizations enables us to explore the contours of constant PL peak energy and lattice parameter as functions of the quaternary compositions. The observation of room temperature PL emission at 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GrdnN MQW heterostructures have been grown; both XRD and PL measurements suggest the possibility of incorporating this quaternary into optoelectronic devices.

  12. Induction of contact drematitis in guinea pigs by quaternary ammonium compounds: the mechanisms of antigen formation

    SciTech Connect

    Schallreuter, K.R.; Schulz, K.H.; Wood, J.M.

    1986-12-01

    Eight quaternary ammonium compounds were tested for their ability to induce contact dermatitis in guinea pigs by using a modified Freund's complete adjuvant test together with the guinea pig maximization test. Only two quaternary ammonium salts of eight tested could be designated as strong allergens. These two active substances were shown to be capable of stable association with membrane lipids in forming immunogenic complexes. This surface complexation phenomenon was confirmed by using a spin-labeled quaternary ammonium salt which competed for binding sites to the surface of epidermal cells in vivo. Electron spin resonance was used to demonstrate that stable ion-pairs are formed between binding sites and the two allergenic preservatives. Furthermore, information was obtained on the kinetics of immunogenic complex formation as well as on the position and orientation of the quaternary ammonium ion at the cell surface.

  13. Metalorganic Vapor-Phase Epitaxial Growth and Characterization of Quaternary AlGaInN

    SciTech Connect

    BANAS, MICHAEL ANTHONY; CRAWFORD, MARY H.; FIGIEL, JEFFREY J.; HAN, JUNG; LEE, STEPHEN R.; MYERS JR., SAMUEL M.; PETERSON, GARY D.

    1999-09-27

    In this letter we report the growth (by MOVPE) and characterization of quaternary AlGaInN. A combination of PL, high-resolution XRD, and RBS characterizations enables us to explore and delineate the contours of equil-emission energy and lattice parameters as functions of the quaternary compositions. The observation of room temperature PL emission as short as 351nm (with 20% Al and 5% In) renders initial evidence that the quaternary could be used to provide confinement for GaInN (and possibly GaN). AlGaInN/GdnN MQW heterostructures have also been grown; both x-ray diffraction and PL measurement suggest the possibility of incorporating this quaternary into optoelectronic devices.

  14. Induction of contact dermatitis in guinea pigs by quaternary ammonium compounds: the mechanism of antigen formation.

    PubMed Central

    Schallreuter, K U; Schulz, K H; Wood, J M

    1986-01-01

    Eight quaternary ammonium compounds were tested for their ability to induce contact dermatitis in guinea pigs by using a modified Freund's complete adjuvant test together with the guinea pig maximization test. Only two quaternary ammonium salts of the eight tested could be designated as strong allergens. These two active substances were shown to be capable of stable association with membrane lipids in forming immunogenic complexes. This surface complexation phenomenon was confirmed by using a spin-labeled quaternary ammonium salt which competed for binding sites at the surface of epidermal cells in vivo. Electron spin resonance was used to demonstrate that stable "ion-pairs" are formed between binding sites and the two allergenic preservatives. Furthermore, information was obtained on the kinetics of immunogenic complex formation as well as on the position and orientation of the quaternary ammonium ion at the cell surface. PMID:3830108

  15. ENDF/B fission-product data

    SciTech Connect

    Rose, P.F.; Burrows, T.W.

    1981-01-01

    In recognition of the pressing need for nuclear decay data in a variety of reactor-related applications, the scope of the Evaluated Nuclear Data Files (ENDF/B) was expanded to include such information. The initial reason for this expansion was to provide reliable data and a common data base to be used in computer codes developed to carry out summation calculations of the decay-heat source term in reactor cores. The ENDF/B-V fission product file was released in July 1980 and contains data for 877 nuclides. Forty-two of these are found in greater detail on the General Purpose file. Seven hundred and fifty isotopes contain decay data. One hundred and ninety-six contain cross section data for total, elastic, inelastic, and angular distributions in the energy range 10/sup -5/ eV to 20 MeV. This special fission product file is contained on 6 magnetic tapes, and is available from the National Nuclear Data Center (NNDC) at BNL. (WHK)

  16. A fission-powered interstellar precursor mission

    NASA Astrophysics Data System (ADS)

    Lipinski, Ronald J.; Lenard, Roger X.; Wright, Steven A.; West, John L.

    1999-01-01

    An ``interstellar precursor mission'' lays the groundwork for eventual interstellar exploration by studying the interstellar medium and by stretching technologies that have potential application for eventual interstellar exploration. The numerous scientific goals for such a mission include generating a 3-D stellar map of our galaxy, studying Kuiper-belt and Oort cloud objects, and observing distant objects using the sun's gravitational lens as the primary of an enormous telescope. System equations are developed for a space tug which propels a 2500-kg scientific payload to 550 astronomical units in about 20 years. The tug to transport this payload uses electric propulsion with an lsp of 15,000 seconds and a fission reactor with a closed Brayton cycle to generate the electricity. The optimal configuration may be to thrust for only about 6 years and then coast for the remaining 14 years. This spacecraft does not require any physics breakthroughs or major advances in technology. The fission power system can be engineered and built by drawing upon known technologies developed for related systems over the past 40 years. The tug system would eventually reach 1000 a.u in 33 years, and would have adequate power to relay large amounts of data throughout its journey.

  17. Fission fragment rockets: A potential breakthrough

    SciTech Connect

    Chapline, G.F.; Dickson, P.W.; Schnitzler, B.G.

    1988-01-01

    A new reactor concept which has the potential of enabling extremely energetic and ambitious space propulsion missions is described. Fission fragments are directly utilized as the propellant by guiding them out of a very low density core using magnetic fields. The very high fission fragment exhaust velocities yield specific impulses of approximately a million seconds while maintaining respectable thrust levels. Specific impulses of this magnitude allow acceleration of significant payload masses to several percent of the velocity of light and enable a variety of interesting missions, e.g., payloads to the nearest star, Alpha Centauri, in about a hundred years for very rapid solar system transport. The parameters reported in this paper are based on a very preliminary analysis. Considerable trade-off studies will be required to find the optimum system. We hope the optimum system proves to be as attractive as our preliminary analysis indicates, although we must admit that our limited effort is insufficient to guarantee any specific level of performance.

  18. The role of Quaternary environmental change in plant macroevolution: the exception or the rule?

    PubMed

    Willis, Katherine J; Niklas, Karl J

    2004-02-29

    The Quaternary has been described as an important time for genetic diversification and speciation. This is based on the premise that Quaternary climatic conditions fostered the isolation of populations and, in some instances, allopatric speciation. However, the 'Quaternary Ice-Age speciation model' rests on two key assumptions: (i) that biotic responses to climate change during the Quaternary were significantly different from those of other periods in Earth's history; and (ii) that the mechanisms of isolation during the Quaternary were sufficient in time and space for genetic diversification to foster speciation. These assumptions are addressed by examining the plant fossil record for the Quaternary (in detail) and for the past 410 Myr, which encompasses previous intervals of icehouse Earth. Our examination of the Quaternary record indicates that floristic responses to climate changes during the past 1.8 Myr were complex and that a distinction has to be made between those plants that were able to withstand the extremes of glacial conditions and those that could not. Generation times are also important as are different growth forms (e.g. herbaceous annuals and arborescent perennials), resulting in different responses in terms of genetic divergence rates during isolation. Because of these variations in the duration of isolation of populations and genomic diversification rates, no canonical statement about the predominant floristic response to climatic changes during the Quaternary (i.e. elevated rates of speciation or extinction, or stasis) is currently possible. This is especially true because of a sampling bias in terms of the fossil record of tree species over that of species with non-arborescent growth forms. Nevertheless, based on the available information, it appears that the dominant response of arborescent species during the Quaternary was extinction rather than speciation or stasis. By contrast, our examination of the fossil record of vascular plants for the past 410 Myr indicates that speciation rates often increased during long intervals of icehouse Earth (spanning up to 50 Myr). Therefore, longer periods of icehouse Earth than those occurring during the Quaternary may have isolated plant populations for sufficiently long periods of time to foster genomic diversification and allopatric speciation. Our results highlight the need for more detailed study of the fossil record in terms of finer temporal and spatial resolution than is currently available to examine the significance of intervals of icehouse Earth. It is equally clear that additional and detailed molecular studies of extant populations of Quaternary species are required in order to determine the extent to which these 'relic' species have genomically diversified across their current populations. PMID:15101573

  19. Neutron capture and fission in /sup 254g/ Es

    SciTech Connect

    Halperin, J.; Bigelow, J.E.; O'Kelley, G.D.; Oliver, J.H.; Wiggins, J.T.

    1985-07-01

    Integral neutron capture and neutron fission cross sections have been measured for the 276-day /sup 254g/ Es. Thermal cross sections and resonance integrals were evaluated using a cadmium filter technique. Capture cross sections were determined from alpha-particle spectrum measurements following neutron irradiations with cobalt flux monitors. Fission cross sections were measured using fission track detection techniques with STTU monitors. The fission cross-section values compared favorably with an absorption cross-section determination from a burnout experiment of SVTEs-SVUEs. The integral neutron capture and fission cross sections determined for /sup 254g/ Es are: sigma /sub c/ /sup th/ = 28.3 + or - 2.5 and I /sub c/ = 18.2 + or - 1.5 b, and sigma /sub F/ /sup th/ = 1970 + or - 200 and I /sub F/ = 1200 + or - 250 b.

  20. Microscopic theory of singlet exciton fission. I. General formulation

    E-print Network

    Berkelbach, Timothy C; Reichman, David R

    2012-01-01

    Singlet fission, a spin-allowed energy transfer process generating two triplet excitons from one singlet exciton, has the potential to dramatically increase the efficiency of organic solar cells. However, the dynamical mechanism of this phenomenon is not fully understood and a complete, microscopic theory of singlet fission is lacking. In this work, we assemble the components of a comprehensive microscopic theory of singlet fission that connects excited state quantum chemistry calculations with finite-temperature quantum relaxation theory. We elaborate on the distinction between localized diabatic and delocalized adiabatic bases for the interpretation of singlet fission experiments in both the time and frequency domains. We discuss various approximations to the exact density matrix dynamics and propose Redfield theory as an ideal compromise between speed and accuracy for the detailed investigation of singlet fission in dimers, clusters, and crystals. Investigations of small model systems based on parameters t...

  1. Activated singlet exciton fission in a semiconducting polymer.

    PubMed

    Musser, Andrew J; Al-Hashimi, Mohammed; Maiuri, Margherita; Brida, Daniele; Heeney, Martin; Cerullo, Giulio; Friend, Richard H; Clark, Jenny

    2013-08-28

    Singlet exciton fission is a spin-allowed process to generate two triplet excitons from a single absorbed photon. This phenomenon offers great potential in organic photovoltaics, but the mechanism remains poorly understood. Most reports to date have addressed intermolecular fission within small-molecular crystals. However, through appropriate chemical design chromophores capable of intramolecular fission can also be produced. Here we directly observe sub-100 fs activated singlet fission in a semiconducting poly(thienylenevinylene). We demonstrate that fission proceeds directly from the initial 1Bu exciton, contrary to current models that involve the lower-lying 2Ag exciton. In solution, the generated triplet pairs rapidly recombine and decay through the 2Ag state. In films, exciton diffusion breaks this symmetry and we observe long-lived triplets which form charge-transfer states in photovoltaic blends. PMID:23883167

  2. Fission matrix capability for MCNP, Part II - Applications

    SciTech Connect

    Carney, S. E. [University of Michigan, NERS Department, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States); Brown, F. B. [Los Alamos National Laboratory, Monte Carlo Codes Group, MS A143, PO Box 1663, Los Alamos, NM 87545 (United States); Kiedrowski, B. C. [University of Michigan, NERS Department, 2355 Bonisteel Boulevard, Ann Arbor, MI 48109 (United States); Martin, W. R. [Los Alamos National Laboratory, Monte Carlo Codes Group, MS A143, PO Box 1663, Los Alamos, NM 87545 (United States)

    2013-07-01

    This paper describes the initial experience and results from implementing a fission matrix capability into the MCNP Monte Carlo code. The fission matrix is obtained at essentially no cost during the normal simulation for criticality calculations. It can be used to provide estimates of the fundamental mode power distribution, the reactor dominance ratio, the eigenvalue spectrum, and higher mode spatial eigenfunctions. It can also be used to accelerate the convergence of the power method iterations. Past difficulties and limitations of the fission matrix approach are overcome with a new sparse representation of the matrix, permitting much larger and more accurate fission matrix representations. Numerous examples are presented. A companion paper (Part I - Theory) describes the theoretical basis for the fission matrix method. (authors)

  3. Algicidal Activity of a Surface-Bonded Organosilicon Quaternary Ammonium Chloride

    PubMed Central

    Walters, P. A.; Abbott, E. A.; Isquith, A. J.

    1973-01-01

    The hydrolysis product of a quaternary amine-containing organosilicon salt, 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, was found to exhibit algicidal activity while chemically bonded to a variety of substrates. Six representative species of Chlorophyta, Cyanophyta, and Chrysophyta were used to evaluate the algicidal activity. Substrate-bonded 14C-labeled organosilicon quaternary ammonium salt when attached to nonwoven fibers was durable to repeated washings, and algicidal activity could not be attributed to slow release of the chemical. Images PMID:4632852

  4. SURVEY OF TERNARY AND QUATERNARY METASTABLE GAMMA-PHASE URANIUM ALLOYS

    Microsoft Academic Search

    V. W. Storhok; A. A. Bauer; R. F. Dickerson

    1958-01-01

    A survey of the effects of ternary and quaternary alloying on the ;\\u000a stability and properties of uranium-zirconium, -- niobium, and -- molybdenum-base ;\\u000a gammaphase alloys was conducted. The effects of ternary and quaternary additions ;\\u000a of chromium, molybdenum, niobium, ruthenium, vanndium, and zirconium on ;\\u000a transformation kinetics, transformation temperature, hot hardness, and corrosion ;\\u000a resistance were investigated. Niobium or

  5. The performance of direct-sequence spread spectrum with complex processing and quaternary data modulation

    Microsoft Academic Search

    Thomas G. Macdonald; Michael B. Pursley

    2000-01-01

    The receiver processing that is often employed for direct-sequence spread spectrum with quaternary data modulation operates separately on in-phase and quadrature components of the spread-spectrum signal. Previous results on complex quaternary sequences, which are also referred to as four-phase sequences, provide a strong motivation to employ alternative processing methods that permit the receiver to benefit from the correlation properties of

  6. Studies on the synthesis and antibacterial activities of polymeric quaternary ammonium salts from dimethylaminoethyl methacrylate

    Microsoft Academic Search

    Guiqian Lu; Dingcai Wu; Ruowen Fu

    2007-01-01

    Four quaternary ammonium salt monomers were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with benzyl chloride (BC), butyl bromide (BB), dodecyl bromide (DB) or hexadecyl bromide (HB), respectively. And then, the monomers were homopolymerized to obtain four polymeric quaternary ammonium materials with different lengths of alkyl chain, which were referred to as poly(DMAEMA-BC), poly(DMAEMA-BB), poly(DMAEMA-DB) and poly(DMAEMA-HB), respectively. The resultant

  7. Mixed Quaternary Ammonium and Phosphonium Salts Bound to Macromolecular Supports for Removal Bacteria from Water

    Microsoft Academic Search

    A. Popa; G. Ilia; S. Iliescu; G. Dehelean; A. Pascariu; A. Bora; C. M. Davidescu

    2004-01-01

    This paper deals with synthesis and characterization of mixed quaternary ammonium and phosphonium salts grafted on macromolecular supports by polymer-analogous trans-quaternization reactions. The degrees of functionalization with quaternary mixed ammonium and phosphonium groups are relatively high, ranging from 0.09 to 1.285 mmoles of functional groups\\/gram of copolymer, ensuring a sufficient concentration of active centers per unit mass of copolymer and

  8. Synthesis and structure-activity relationship (SAR) of novel perfluoroalkyl-containing quaternary ammonium salts

    Microsoft Academic Search

    Jian-Ying Sun; Jing Li; Xiao-Long Qiu; Feng-Ling Qing

    2005-01-01

    A new series of perfluoroalkyl-containing quaternary ammonium compounds were prepared and examined for their antibacterial activities. The perfluoroalkyl-containing quaternary ammonium salts mainly exhibited excellent antibacterial activity for the Gram-positive strain such as Staphylococcus aureus, the MIC (minimal inhibitory concentration) values was between 2.5 and 10?g\\/mL and the MBC (minimal bactericidal concentration) values were 20?g\\/mL. They all showed weak activity against

  9. Synthesis and in vitro antibacterial activity of quaternary ammonium cephalosporin derivatives bearing oxazolidinone moiety

    Microsoft Academic Search

    In Hwa Chung; Choong Sup Kim; Jae Hong Seo; Bong Young Chung

    1999-01-01

    Several oxazolidinones having amine moiety were prepared to form a quaternary ammonium salt with cephalosporin nucleus, and\\u000a antibacterial activity of the quaternary ammonium cephalosporin derivatives bearing oxazolidinone moiety were examined particularly\\u000a with expectation of dual activity. However, the cephalosporin-oxazolidinone compounds revealed rather weaker antibacterial\\u000a activityin vitro than their parent exazolidinone and cephalosporin without showing any characteristic activity as expected.

  10. Antibacterial activity of quaternary ammonium chitosan containing mono or disaccharide moieties: Preparation and characterization

    Microsoft Academic Search

    Warayuth Sajomsang; Pattarapond Gonil; Supawan Tantayanon

    2009-01-01

    The 9 quaternary ammonium chitosans containing monosaccharides or disaccharides moieties were successfully synthesized by reductive N-alkylation then quaternized by N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (Quat-188). The chemical structures of quaternary ammonium chitosan derivatives were characterized by ATR-FTIR and 1H NMR spectroscopy. The degree of N-substitution (DS) and the degree of quaternization (DQ) were determined by 1H NMR spectroscopic method. It was found

  11. Efficacy of a quaternary ammonium compound against planktonic and sessile populations of different Legionella pneumophila strains

    Microsoft Academic Search

    Ayten Kimiran-Erdem; Nazmiye Ozlem Sanli-Yurudu; Aysin Cotuk

    2007-01-01

    Efficacy of Gemacide PN-50TM (a quaternary ammonium compound) as a commercial formulation recommended for disinfecting heat exchangers was determined\\u000a for both planktonic and sessile populations of variousLegionella pneumophila strains. The quaternary ammonium compound (QAC) was preferred as an alternative due to the emerging resistance of potentially\\u000a pathogenic bacteria against different biocides. PlanktonicL. pneumophila strains were suspended in tap water while

  12. Antibacterial activity of reactive quaternary ammonium compounds in solution and in nonleachable coatings

    Microsoft Academic Search

    G. Gozzelino; D. E. Romero Tobar; N. Chaitiemwong; W. C. Hazeleger; R. R. Beumer

    2011-01-01

    Antibacterial polymers suitable for coating applications without leaching of the biocidal component have been obtained by UV copolymerization of acrylic resins with acrylic monomers containing quaternary ammonium moieties. Suitable reactive biocides, based on quaternary ammonium monomers (QAMs), endowed with undecylacryloyl group and alkyl chains with 2 (QAM-C2), 8 (QAM-C8), and 16 (QAM-C16) carbon atoms have been synthesized. Aqueous solutions of

  13. Engineering geologic studies of the Austin Chalk, Taylor Marl, and Quaternary alluvium Ellis County, Texas

    E-print Network

    Westerfield, John Gayden

    1989-01-01

    ENGINEERING GEOLOGIC STUDIES OF THE AUSTIN CHALK, TAYLOR MARL, AND QUATERNARY ALLUVIUM, ELLIS COUNTY, TEXAS A Thesis by JOHN GAYDEN WESTERFIELD Submitted to the Office of Graduate Studies of Texas A&M University in partial fullfillment... and content by: Norma (Chair of ford ommittee) Christ pher C. Mathewson (Member) Richard L. Carlson (Member) John H. 'Spa (H ad of Department) May 1989 ABSTRACT Engineering Geologic Studies of the Austin Chalk, Taylor Marl, and Quaternary Alluvium...

  14. Engineering geologic studies of the Austin Chalk, Taylor Marl, and Quaternary alluvium Ellis County, Texas 

    E-print Network

    Westerfield, John Gayden

    1989-01-01

    ENGINEERING GEOLOGIC STUDIES OF THE AUSTIN CHALK, TAYLOR MARL, AND QUATERNARY ALLUVIUM, ELLIS COUNTY, TEXAS A Thesis by JOHN GAYDEN WESTERFIELD Submitted to the Office of Graduate Studies of Texas A&M University in partial fullfillment... of the requirements for the degree of MASTER OF SCIENCE May 1989 Major Subject: Geology ENGINEERING GEOLOGIC STUDIES OF THE AUSTIN CHALX, TAYLOR MARL, AND QUATERNARY ALLUVIUM, ELLIS COUNTY, TEXAS A Thesis by JOHN GAYDEN WESTERFIELD Approved as to style...

  15. Use of quaternary ammonium salts of nitrogen containing polymers for improved carburetor detergency

    SciTech Connect

    Biasotti, J.B.; Vartanian, P.F.

    1980-01-15

    A quaternary ammonium salt is described of a copolymer, said copolymer being the olefin polymerization product of: (A) a nitrogen amine free ester of a C/sub 1/-C/sub 6/ olefinically unsaturated aliphatic mono-, di-, or polycarboxylic acid having a tertiary nitrogen atom; and (B) an olefinically unsaturated co-monomer containing a basic nitrogen atom in a side chain; a fuel component, especially gasoline, containing such quaternary ammonium salt of such copolymer as a detergent.

  16. Characterization of â??the quaternary amine transporters of Rhizobium leguminosarum bv. viciae 3841

    Microsoft Academic Search

    Marc A. Fox; Ramakrishnan Karunakaran; Mary E. Leonard; Bouchra Mouhsine; Allan Williams; Alison K. East; J. Allan Downie; Philip S. Poole

    2008-01-01

    Rhizobium leguminosarum bv. viciae 3841 contains six putative quaternary ammonium transporters (Qat), of the ABC family. Qat6 was strongly induced by hyperosmosis although the solute transported was not identified. All six systems were induced by the quaternary amines choline and glycine betaine. It was confirmed by microarray analysis of the genome that pRL100079-83 (qat6) is the most strongly upregulated transport

  17. Synthesis of a quaternary amine anion exchange resin and study its adsorption behaviour for chromate oxyanions

    Microsoft Academic Search

    Asem A. Atia

    2006-01-01

    Glycidyl methacrylate\\/N,N?-methylene bis-acrylamide (GMA\\/MBA) was prepared and allowed to react with tetraethylenepentamine (TEP) to give glycidyl methacrylate amine resin (RPA) followed by treatment with glycidyl trimethylammonium chloride (GTA) to give glycidyl methacrylate resin bearing quaternary ammonium chloride moieties (RQA). Zeta potential measurements showed that RQA particles are positively charged over pH 2–10 indicating the strong basic nature of the quaternary

  18. Synthesis and characterization of ruthenium(II) phenanthroline complexes containing quaternary amine substituents

    Microsoft Academic Search

    A. A. Bhuiyan; R. Dossey; T. J. Anderson; F. Millett; B. Durham

    2008-01-01

    A series of mixed-ligand complexes of ruthenium(II) containing 5-methylphenanthroline and trimethylamino-5-methylphenanthroline have been synthesized to investigate the impact of the quaternary amine on the photophysical properties. Thermal stability studies indicate that the quaternary amine is stable with respect to hydrolysis. Mass spectral analysis of the complexes revealed only fragments consistent with homolytic cleavage of the amines and no parent ions

  19. Kinetics of extraction in the cupric-chloro-quaternary amine system

    Microsoft Academic Search

    M. C. Fuerstenau; M. R. Elmore; B. R. Palmer; K. N. Han

    1987-01-01

    The kinetics of extraction of the cupric tetrachloro complex with quaternary amine is presented as a function of cupric, chloride,\\u000a and amine concentrations and temperature. Initial rate exhibits first order dependence with respect to the concentrations\\u000a of the cupric tetrachloro complex and quaternary amine. Binary interaction between interfacial cupric tetrachloro complex\\u000a and amine is rate controlling. The enthalpy of activation

  20. Sampling and Analysis of Quaternary Ammonium Compounds (QACs) Traces in Indoor Atmosphere

    Microsoft Academic Search

    Guillaume Vincent; Marie Christine Kopferschmitt-Kubler; Philippe Mirabel; Gabrielle Pauli; Maurice Millet

    2007-01-01

    Quaternary Ammonium Compounds (QACs) are widely found in disinfectants used in hospitals. Benzalkonium chloride (BAC) and\\u000a didecyldimethylammonium chloride (DDAC) predominate in the disinfecting formulations. These compounds are strong irritants\\u000a and can play a role in the induction of Occupational Asthma among the professionals of health and cleaning. In order to evaluate\\u000a the potential health effect of these quaternary ammonium compounds

  1. Improved Fission Neutron Data Base for Active Interrogation of Actinides

    SciTech Connect

    Pozzi, Sara; Czirr, J. Bart; Haight, Robert; Kovash, Michael; Tsvetkov, Pavel

    2013-11-06

    This project will develop an innovative neutron detection system for active interrogation measurements. Many active interrogation methods to detect fissionable material are based on the detection of neutrons from fission induced by fast neutrons or high-energy gamma rays. The energy spectrum of the fission neutrons provides data to identify the fissionable isotopes and materials such as shielding between the fissionable material and the detector. The proposed path for the project is as follows. First, the team will develop new neutron detection systems and algorithms by Monte Carlo simulations and bench-top experiments. Next, They will characterize and calibrate detection systems both with monoenergetic and white neutron sources. Finally, high-fidelity measurements of neutron emission from fissions induced by fast neutrons will be performed. Several existing fission chambers containing U-235, Pu-239, U-238, or Th-232 will be used to measure the neutron-induced fission neutron emission spectra. The challenge for making confident measurements is the detection of neutrons in the energy ranges of 0.01 – 1 MeV and above 8 MeV, regions where the basic data on the neutron energy spectrum emitted from fission is least well known. In addition, improvements in the specificity of neutron detectors are required throughout the complete energy range: they must be able to clearly distinguish neutrons from other radiations, in particular gamma rays and cosmic rays. The team believes that all of these challenges can be addressed successfully with emerging technologies under development by this collaboration. In particular, the collaboration will address the area of fission neutron emission spectra for isotopes of interest in the advanced fuel cycle initiative (AFCI).

  2. Induced nuclear fission viewed as a diffusion process: Transients

    SciTech Connect

    Grange, P.; Jun-Qing, L.; Weidenmueller, H.A.

    1983-05-01

    Induced nuclear fission is viewed as a diffusion process of the fission degree of freedom over the fission barrier. We describe this process in terms of a Fokker-Planck equation which contains the fission variable and its canonically conjugate momentum. We solve this equation numerically for several energies (temperatures) of the fissioning nucleus neglecting changes of the fission barrier due to the temperature dependence of nuclear shell effects. We pay particular attention to the time tau needed for the system to build up the quasistationary probability flow over the fission barrier. The rate of the latter is approximated in terms of the Bohr-Wheeler formula or Kramers's transition state expression. Our results for tau are consistent with those obtained earlier in the framework of a simplified model: As long as ..beta..< or =..beta../sub 0/ , the time tau is proportional to ..beta../sup -1/. This relationship exhibits the fact that with increasing friction ..beta.., the diffusion process is accelerated, so that it takes the system increasingly less time to attain the quasistationary distribution. The constant ..beta../sub 0/ is roughly given by 2..omega../sub 1/, where ..omega../sub 1/ is the frequency of a harmonic oscillator potential which osculates the potential at the minimum corresponding to the initial configuration of the fissioning nucleus. The condition ..beta..< or =..beta../sub 0/ is roughly equivalent with the motion in that minimum being underdamped. The converse relationship: tau increases with ..beta..: is found for ..beta..>..beta../sub 0/. Generalizing Kramers's original derivation, we obtain an analytical expression for the time dependence of the probability current over the fission barrier. For ..beta..< or approx. =..beta../sub 0/, this expression agrees well with our numerical results. We use it to calculate the energy dependence of the fission probability P/sub f/ and find that P/sub f/ grows much less rapidly with increasing excitation energy than would be predicted by the Bohr-Wheeler formula.

  3. Influence of angular momentum on the mass distribution width of heavy ion induced fission: What is the frontier between fission and quasi-fission?

    Microsoft Academic Search

    C. Lebrun; F. Hanappe; J. F. Lecolley; F. Lefebvres; C. Ngô; J. Péter; B. Tamain

    1979-01-01

    The 124 and 206 MeV20Ne+natRe and the 192 and 297 MeV40Ar+165Ho systems have been used to form the 205 At nucleus with different angular momentum populations. The mass distributions of the fission fragments have been measured. Removing the effect of the temperature, it has been found that their width strongly increases with angular momentum especially when the fission barrier has

  4. Mixed ternary ion associate formation between xanthene dye, cinchona-alkaloid and quaternary ammonium ion and its application to the determination of trace amounts of quaternary ammonium salts in pharmaceuticals

    Microsoft Academic Search

    Tadao Sakai; Akihiko Hirose

    2003-01-01

    Xanthene dyes such as eosin and tetraiodofluorescein form 1:2 ion associates with quaternary ammonium ions at pH 7–9; however, the development of color in the organic solvent is poor. When a quaternary ammonium salt is added in the extractable 1:2 associate formed between a xanthene dye and a cinchona-alkaloid in the neutral media, a mixed ternary ion associate (xanthene dye:cinchona-alkaloid:quaternary

  5. Towards high accurate neutron-induced fission cross sections of 240,242Pu: Spontaneous fission half-lives

    NASA Astrophysics Data System (ADS)

    Salvador-Castiñeira, P.; Bry?, T.; Eykens, R.; Hambsch, F.-J.; Moens, A.; Oberstedt, S.; Pretel, C.; Sibbens, G.; Vanleeuw, D.; Vidali, M.

    2013-12-01

    Fast spectrum neutron-induced fission cross sections of transuranic isotopes are being of special demand in order to provide accurate data for the new GEN-IV nuclear power plants. To minimize the uncertainties on these measurements accurate data on spontaneous fission half-lives and detector efficiencies are a key point. High ?-active actinides need special attention since the misinterpretation of detector signals can lead to low efficiency values or underestimation in fission fragment detection. In that context, 240,242Pu isotopes have been studied by means of a Twin Frisch-Grid Ionization Chamber (TFGIC) for measurements of their neutron-induced fission cross section. Gases with different drift velocities have been used, namely P10 and CH4. The detector efficiencies for both samples have been determined and improved spontaneous fission half-life values were obtained.

  6. Results of interlaboratory comparison of fission track ages for 1992 fission track workshop

    USGS Publications Warehouse

    Miller, D.S.; Crowley, K.D.; Dokka, R.K.; Galbraith, R.F.; Kowallis, B.J.; Naeser, C.W.

    1993-01-01

    Two apatites and one sphene were made available to the fission track research community for analysis prior to the 1992 Fission Track Workshop held in Philadelphia, U.S.A., 13-17 July. Eighteen laboratories throughout the world received aliquots of apatite and sphene. To date, analyses by 33 different scientists have been representing 15 different laboratories. With respect to the previous two interlaboratory comparisons, there is a noticeable improvement in the accuracy of the age results (Naeser and Cebula, 1978; Naeser et al., 1981; Miller et al., 1985;Miller et al.1990). Ninety-four percent of the analysis used the external detector method (EDM) combined with the zeta technique while the remaining individuals used the population method (POP). Track length measurements (requested for the first time in the interlaboratory comparison studies) were in relatively good agreement. ?? 1993.

  7. Coal cleaning employing quaternary salts. Annual report, July 1, 1984-June 30, 1985. [Tetrabutyl ammonium hydroxide; tetramethyl ammonium hydroxide

    SciTech Connect

    Hippo, E.J.; Murdie, N.

    1985-09-01

    An investigation into a novel approach to coal desulfurization has been initiated. This approach is in the formative stages, but is envisioned to included a treatment step to swell coal in quaternary salt solution followed by physical separation, chemical reaction to desulfurize the coal, and recovery of the quaternary salt. The present program was aimed at developing fundamental data associated with the first step. This report covers the first six months of the project. The objective of this portion of the program was to define conditions under which complete exchange of quaternary salts with coal hydroxy groups occurs, define the extent of coal swelling and changes in coal properties as a function of amount of exchange, and determine the effect of process variation on swelling rate and coal properties. Results of this research have demonstrated that substantial coal swelling occurs in the presence of quaternary salts. The amount of quaternary exchange is a small portion of the total OH groups present in the coal. Swelling has been found to be dependent on the concentration of quaternary salts, the ratio of solution to coal, time of exchange, and the type of solvent. The data also demonstrate that particle size and size distribution are changed extensively by the quaternary salt treatment. Furthermore, it appears that iron sulfide and/or sulfate are dissolved in the quaternary base. Also, some organic material is dissolved by the quaternary base. Preliminary data indicate that minerals and inertinite can be concentrated after quaternary salt treatment. The results indicate that quaternary recovery should be easier than first expected. Also, the excessive swelling with little exchange indicated that the surface chemistry of the coal is altered after exchange. Thus, oil agglomeration and froth flotation should be improved when coals are treated with the quaternary salt. 11 refs., 11 tabs.

  8. Early Flight Fission Test Facilities (EFF-TF) To Support Near-Term Space Fission Systems

    Microsoft Academic Search

    Melissa van Dyke; Melissa

    2004-01-01

    Through hardware based design and testing, the EFF-TF investigates fission power and propulsion component, subsystems, and integrated system design and performance. Through demonstration of systems concepts (designed by Sandia and Los Alamos National Laboratories) in relevant environments, previous non-nuclear tests in the EFF-TF have proven to be a highly effective method (from both cost and performance standpoint) to identify and

  9. Spontaneous Fission-Neutron Fission Xenon: A New Technique for Dating Geological Events

    Microsoft Academic Search

    Albert Teitsma; W. B. Clarke; C. J. Allegre

    1975-01-01

    A method for dating geological samples which uses fission product xenon in a manner similar to the use of radiogenic argon in the 40Ar-39 Ar technique has been developed. The results of stepwise heating experiments for a zircon from the Ahaggar region in the Sahara are compared to the geochronology determined by the rubidiumstrontium, uranium-thorium-lead, and potassium-argon dating methods.

  10. Spontaneous fission--neutron fission xenon: a new technique for dating geological events

    Microsoft Academic Search

    A. Teitsma; W. B. Clarke; C. J. Allegre

    1975-01-01

    A method for dating geological samples which uses fission product xenon ; in a manner similar to the use of radiogenic argon in the ⁴°Ar--³⁹Ar ; technique has been developed. The results of stepwise heating experiments for a ; zircon from the Ahaggar region in the Sahara are compared to the geochronology ; determined by the rubidium--strontium, uranium--thorium--lead, and potassium--;

  11. Fission fragment properties in fast-neutron-induced fission of /sup 237/Np

    SciTech Connect

    Naqvi, A.A.; Kaeppeler, F.; Dickmann, F.; Mueller, R.

    1986-07-01

    We report on a four-parameter measurement of the kinetic energies E-italic and the velocities v-italic of correlated fragments in fast-neutron-induced fission of /sup 237/Np. The influence of excitation energy on the important fragment properties such as mass, kinetic energy, and prompt neutron emission have been investigated experimentally at 0.80 and 5.55 MeV neutron energy. Our results include mean values of fragment properties before and after neutron evaporation, e.g., of fragment velocities and masses, total kinetic energies, and the respective variances. Also given are the distributions of fragment mass, of E-italic/sub k-italic//sub ,tot/, the variance of E-italic/sub k-italic//sub ,tot/, as well as the number of prompt fission neutrons as a function of fragment mass. These results show that shell effects are strong near threshold at E-italic/sub n/ = 0.80 MeV, but decrease significantly at the higher excitation energy, in qualitative agreement with the model of Wilkins, Chasman, and Steinberg. However, the observed increase in the number of prompt fission neutrons, which appears only in the heavy fragment, cannot be explained by this model.

  12. Results of interlaboratory comparison of fission-track age standards: Fission-track workshop-1984

    USGS Publications Warehouse

    Miller, D.S.; Duddy, I.R.; Green, P.F.; Hurford, A.J.; Naeser, C.W.

    1985-01-01

    Five samples were made available as standards for the 1984 Fission Track Workshop held in the summer of 1984 (Rensselaer Polytechnic Institute, Troy, New York). Two zircons, two apatites and a sphene were distributed prior to the meeting to 40 different laboratories. To date, 24 different analysts have reported results. The isotopic ages of the standards ranged from 16.8 to 98.7 Myr. Only the statement that the age of each sample was less than 200 Myr was provided with the set of standards distributed. Consequently, each laboratory was required to use their laboratory's accepted treatment (irradiation level, etching conditions, counting conditions, etc.) for these samples. The results show that some workers have serious problems in achieving accurate age determinations. This emphasizes the need to calibrate experimental techniques and counting procedures against age standards before unknown ages are determined. Any fission-track age determination published or submitted for publication can only be considered reliable if it is supported by evidence of consistent determinations on age standards. Only this can provide the scientific community with the background to build up confidence concerning the validity of the fission-track method. ?? 1985.

  13. Empirical description of ? -delayed fission partial half-lives

    NASA Astrophysics Data System (ADS)

    Ghys, L.; Andreyev, A. N.; Antalic, S.; Huyse, M.; Van Duppen, P.

    2015-04-01

    Background: The process of ? -delayed fission (? DF ) provides a versatile tool to study low-energy fission in nuclei far away from the ? -stability line, especially for nuclei which do not fission spontaneously. Purpose: The aim of this paper is to investigate systematic trends in ? DF partial half-lives. Method: A semi-phenomenological framework was developed to systematically account for the behavior of ? DF partial half-lives. Results: The ? DF partial half-life appears to exponentially depend on the difference between the Q value for ? decay of the parent nucleus and the fission-barrier energy of the daughter (after ? decay) product. Such dependence was found to arise naturally from some simple theoretical considerations. Conclusions: This systematic trend was confirmed for experimental ? DF partial half-lives spanning over seven orders of magnitude when using fission barriers calculated from either the Thomas-Fermi or the liquid-drop fission model. The same dependence was also observed, although less pronounced, when comparing to fission barriers from the finite-range liquid-drop model or the Thomas-Fermi plus Strutinsky integral method.

  14. Compilation of fission product yields Vallecitos Nuclear Center

    SciTech Connect

    Rider, B.F.

    1980-01-01

    This document is the ninth in a series of compilations of fission yield data made at Vallecitos Nuclear Center in which fission yield measurements reported in the open literature and calculated charge distributions have been utilized to produce a recommended set of yields for the known fission products. The original data with reference sources, as well as the recommended yields are presented in tabular form for the fissionable nuclides U-235, Pu-239, Pu-241, and U-233 at thermal neutron energies; for U-235, U-238, Pu-239, and Th-232 at fission spectrum energies; and U-235 and U-238 at 14 MeV. In addition, U-233, U-236, Pu-240, Pu-241, Pu-242, Np-237 at fission spectrum energies; U-233, Pu-239, Th-232 at 14 MeV and Cf-252 spontaneous fission are similarly treated. For 1979 U234F, U237F, Pu249H, U234He, U236He, Pu238F, Am241F, Am243F, Np238F, and Cm242F yields were evaluated. In 1980, Th227T, Th229T, Pa231F, Am241T, Am241H, Am242Mt, Cm245T, Cf249T, Cf251T, and Es254T are also evaluated.

  15. Evaluation of fusion-fission energy systems

    SciTech Connect

    Willingham, C.E.; Bickford, W.E.

    1980-10-01

    The Office of Fuel Cycle Evaluation of the Department of Energy has conducted a Nonproliferation Alternative Systems Assessment Program (NASAP). The goal of the NASAP is to provide recommendations in the development of nuclear energy systems which have potential for reducing the risk of nuclear weapons proliferation while satisfying the short- and long-term needs for nuclear energy. The fusion-fission hybrid is one of the nuclear energy systems which have been considered for long-term applications. This paper presents the information needed to evaluate and analyze hybrids for the NASAP. Although most of the combined driver-blanket hybrid systems considered in this study have not been optimized for performance and cost, the resulting data provides valuable insights into the future potential hybrids.

  16. The munich accelerator for fission fragments (MAFF)

    SciTech Connect

    Kester, Oliver; Habs, Dietrich; Gross, Martin; Sieber, Thomas; Bongers, Henning; Kolbe, Alfred; Maier, Hans Juergen; Thirolf, Peter [Ludwig-Maximilians Universitaet Muenchen, 85748 Garching (Germany); Egidy, Till von; Koester, Ulli; Steichele, Erich; Kienle, Paul; Koerner, Hans Joachim [Technische Universitaet Muenchen, 85748 Garching (Germany); Schempp, Alwin [J. W. Goethe Universitaet Frankfurt, 60325 Frankfurt (Germany); Ratzinger, Ulrich [GSI, Postfach 110552, 64220 Darmstadt (Germany)

    1999-04-26

    An accelerator (MAFF) for the new Munich high flux reactor FRM-II is under design in order to deliver intense beams of very neutron-rich fission fragments of up to 10{sup 12} particles per second with final energies between 3.7 and 5.9 MeV/u to perform experiments for the production of heavy elements. To obtain an efficient acceleration in a short LINAC, charge breeding of the 1{sup +}-ion beam from the reactor to a q/A{>=}0.16 is required. New measurements with an electron cyclotron resonance ion source (ECRIS) have shown that the requirements for a low duty cycle LINAC (10%) can be fulfilled by the ECRIS. To reach a high flexibility in the final energy with a small number of structures, new kinds of IH-structures are under development at the Munich tandem laboratory.

  17. Detecting fission from special nuclear material sources

    DOEpatents

    Rowland, Mark S. (Alamo, CA); Snyderman, Neal J. (Berkeley, CA)

    2012-06-05

    A neutron detector system for discriminating fissile material from non-fissile material wherein a digital data acquisition unit collects data at high rate, and in real-time processes large volumes of data directly into information that a first responder can use to discriminate materials. The system comprises counting neutrons from the unknown source and detecting excess grouped neutrons to identify fission in the unknown source. The system includes a graphing component that displays the plot of the neutron distribution from the unknown source over a Poisson distribution and a plot of neutrons due to background or environmental sources. The system further includes a known neutron source placed in proximity to the unknown source to actively interrogate the unknown source in order to accentuate differences in neutron emission from the unknown source from Poisson distributions and/or environmental sources.

  18. (Fuel, fission product, and graphite technology)

    SciTech Connect

    Stansfield, O.M.

    1990-07-25

    Travel to the Forschungszentrum (KFA) -- Juelich described in this report was for the purpose of participating in the annual meeting of subprogram managers for the US/DOE Umbrella Agreement for Fuel, Fission Product, and Graphite Technology. At this meeting the highlights of the cooperative exchange were reviewed for the time period June 1989 through June 1990. The program continues to contribute technology in an effective way for both countries. Revision 15 of the Subprogram Plan will be issued as a result of the meeting. There was interest expressed by KFA management in the level of support received from the NPR program and in potential participation in the COMEDIE loop experiment being conducted at the CEA.

  19. Control system for a small fission reactor

    NASA Astrophysics Data System (ADS)

    Burelbach, J. P.; Kann, W. J.; Saiveau, J. G.

    1985-02-01

    A system for controlling the reactivity of a small fission reactor includes an elongated, flexible hollow tube in the general form of a helical coiled spring axially positioned around and outside of the reactor vessel in an annular space between the reactor vessel and a surrounding cylindrical-shaped neutron reflector. A neutron absorbing material is provided within the hollow tube with the rate of the reaction controlled by the extension and compression of the hollow tube, e.g., extension of the tube increases reactivity while its compression reduces reactivity, in varying the amount of neutron absorbing material disposed between the reactor vessel and the neutron reflector. Conventional mechanical displacement means may be employed to control the coil density of the hollow tube as desired.

  20. Control system for a small fission reactor

    DOEpatents

    Burelbach, J.P.; Kann, W.J.; Saiveau, J.G.

    1985-02-08

    A system for controlling the reactivity of a small fission reactor includes an elongated, flexible hollow tube in the general form of a helical coiled spring axially positioned around and outside of the reactor vessel in an annular space between the reactor vessel and a surrounding cylindrical-shaped neutron reflector. A neutron absorbing material is provided within the hollow tube with the rate of the reaction controlled by the extension and compression of the hollow tube, e.g., extension of the tube increases reactivity while its compression reduces reactivity, in varying the amount of neutron absorbing material disposed between the reactor vessel and the neutron reflector. Conventional mechanical displacement means may be employed to control the coil density of the hollow tube as desired.

  1. Budding and Fission of a multiphase vesicle

    E-print Network

    Jean-Marc Allain; Martine Ben Amar

    2005-04-08

    We present a model of bi-phasic vesicle in the limit of large surface tension. In this regime, the vesicle is completely stretched and well described by two spherical caps with a fold which concentrates the membrane stress. The conservation laws and geometric constraints restrict the space of possible shapes to a pair of solutions labeled by a parameter $\\tau$ given by {\\it line tension/pressure}. For a given $\\tau$ value, the two solutions differ by the length of the interface between domains. For a critical value $\\tau\\_c$, the two vesicle shapes become identical and no solution exists above this critical value. This model sheds new light on two proposed mechanisms (osmotic shocks and molecule absorption) to explain the budding and the fission in recent experiments.

  2. Budding and Fission of a multiphase vesicle

    E-print Network

    Allain, J M; Allain, Jean-Marc; Amar, Martine Ben

    2005-01-01

    We present a model of bi-phasic vesicle in the limit of large surface tension. In this regime, the vesicle is completely stretched and well described by two spherical caps with a fold which concentrates the membrane stress. The conservation laws and geometric constraints restrict the space of possible shapes to a pair of solutions labeled by a parameter $\\tau$ given by {\\it line tension/pressure}. For a given $\\tau$ value, the two solutions differ by the length of the interface between domains. For a critical value $\\tau\\_c$, the two vesicle shapes become identical and no solution exists above this critical value. This model sheds new light on two proposed mechanisms (osmotic shocks and molecule absorption) to explain the budding and the fission in recent experiments.

  3. Nondestructive fission gas release measurement and analysis

    SciTech Connect

    O'Leary, P.M.; Packard, D.R. (Siemens Nuclear Power Corp., Richland, WA (United States))

    1993-01-01

    Siemens Power Corporation (SPC) has performed reactor poolside gamma scanning measurements of fuel rods for fission gas release (FGR) detection for more than 10 yr. The measurement system has been previously described. Over the years, the data acquisition system, the method of spectrum analysis, and the means of reducing spectrum interference have been significantly improved. A personal computer (PC)-based multichannel analyzer (MCA) package is used to collect, display, and store high-resolution gamma-ray spectra measured in the fuel rod plenum. A PC spread sheet is used to fit the measured spectra and compute sample count rates after Compton background subtraction. A Zircaloy plenum spacer is often used to reduce positron annihilation interference that can arise from the INCONEL[sup [reg sign

  4. Late Quaternary carbonate deposition at the bottom of the world

    NASA Astrophysics Data System (ADS)

    Frank, Tracy D.; James, Noel P.; Bone, Yvonne; Malcolm, Isabelle; Bobak, Lindsey E.

    2014-05-01

    Carbonate sediments on polar shelves hold great potential for improving understanding of climate and oceanography in regions of the globe that are particularly sensitive to global change. Such deposits have, however, not received much attention from sedimentologists and thus remain poorly understood. This study investigates the distribution, composition, diagenesis, and stratigraphic context of Late Quaternary calcareous sediments recovered in 15 piston cores from the Ross Sea shelf, Antarctica. Results are used to develop a depositional model for carbonate deposition on glaciated, polar shelves. The utility of the deposits as analogs for the ancient record is explored. In the Ross Sea, carbonate-rich lithofacies, consisting of poorly sorted skeletal sand and gravel, are concentrated in the west and along the outer reaches of the continental shelf and upper slope. Analysis of fossil assemblages shows that deposits were produced by numerous low-diversity benthic communities dominated locally by stylasterine hydrocorals, barnacles, or bryozoans. Radiocarbon dating indicates that carbonate sedimentation was episodic, corresponding to times of reduced siliciclastic deposition. Most accumulation occurred during a time of glacial expansion in the lead-up to the Last Glacial Maximum. A more recent interval of carbonate accumulation postdates the early Holocene sea level rise and the establishment of the modern grounding line for the Ross Ice Shelf. When carbonate factories were inactive, fossil debris was subjected to infestation by bioeroders, dissolution, fragmentation, and physical reworking. This study reveals the episodic nature of carbonate deposition in polar settings and a reciprocal relationship with processes that deliver and redistribute siliciclastic debris. Carbonate production is most active during colder periods of the glacial-interglacial cycle, a potential new sedimentological paradigm for polar carbonate systems. Low accumulation rates and long residence times on the seafloor leave sediments vulnerable to significant post-depositional modification, processes that profoundly affect the appearance of deposits as they enter the rock record. Comparison with other examples of polar carbonates highlights the utility of these Late Quaternary deposits as a well-constrained analog that can aid in the recognition and interpretation of similar deposits from the ancient record.

  5. Quaternary ammonium derivatives as spasmolytics for irritable bowel syndrome.

    PubMed

    Evangelista, S

    2004-01-01

    Quaternary ammonium derivatives such as cimetropium, n-butyl scopolammonium, otilonium and pinaverium bromide have been discovered and developed as potent spasmolytics of the gastrointestinal tract. Their pharmacological activity has been proven in both "in vivo" and "in vitro" studies of hypermotility. "In vitro" experiments showed that they possess antimuscarinic activity at nM level but only pinaverium and otilonium are endowed with calcium channel blocker properties. These latter compounds relaxed the gastrointestinal smooth muscle mainly through a specific inhibition of calcium ion influx through L-type voltage operated calcium channels. Molecular pharmacology trials have indicated that pinaverium and otilonium can bind specific subunits of the calcium channel in the external surface of the plasma membrane and in this way they block the machinery of the contraction. Recent evidence showed that otilonium is able to bind tachykinin NK(2) receptors and not only inhibits one of the major contractile agents but can reduce the activation of afferent nerves devoted to the passage of sensory signals from the periphery to the central nervous system. Thanks to their typical physico-chemical characteristics, they are poorly absorbed by the systemic circulation and generally remain in the gastrointestinal tract where they exert the muscle relaxant activity by a local activity. Some differences exists in the absorption among these compounds: both n-butyl scopolammonium and cimetropium are partially taken up in the bloodstream, pinaverium has a low absorption (8-10 %) but is endowed with an excellent hepato-biliary excretion and otilonium, which has the lowest absorption (3 %), is almost totally excreted by faeces. Quaternary ammonium derivatives are widely used for the treatment of irritable bowel syndrome and recent meta-analyses have supported their efficacy in this disease. Due to its therapeutic index, the use of n-butyl scopolammonium is more indicated to treat acute colics than a chronic disease such as irritable bowel syndrome. Taking into consideration the published trials carried out with validated methodology in irritable bowel syndrome, cimetropium and otilonium are the best demonstrated drugs for the improvement in global assessment, pain and abdominal distension. PMID:15579053

  6. A model of the Quaternary geological deposits of Bucharest City

    NASA Astrophysics Data System (ADS)

    Serpescu, Irina; Radu, Emil; Radu Gogu, Constantin; Amine Boukhemacha, Mohamed; Gaitanaru, Dragos; Bica, Ioan

    2013-04-01

    Bucharest city is located in the central part of the Moesic Platform, in the Romanian Plain with micro-relief resulting from erosion and sedimentary processes which extended along the valleys of the Dambovita River to the south and the Colentina River to the north. The city is located in the axial area of a syncline where the thickness of the sedimentary deposits is up to 1000 m. The area lies on a rigid base is made of metamorphites, and various igneous intrusions (granodiorite, granite). The sedimentary deposits covering this rigid base are made by different phases of erosion and sedimentary processes of marine, lacustrian or continental sediments ending with Quaternary sediments. As a result, different alluvial deposits (such as piedmont, deltaic, alluvial cones, terrace, waterside and lacustrine deposits) can be met. Furthermore one also can find loess deposits which in turn cover totally the older deposits where rivers dug the present relief. To highlight the spatial extent of these geological structures, a geological model of Bucharest city is developed. A set of information coming from different sources as geological and geotechnical boreholes showing a detailed geological and lithological description, geological and topographical maps, geological and hydrogeological reports have been used to develop the 3D geological model of this region. 33 geological cross sections were defined and interpreted by using lithological and sedimentological criteria. Using these geological cross sections and prior geological knowledge, the Quaternary deposits have been described and classified into 6 structural units given from top to down as follows: (1) Superficial deposits represented by loess and anthropogenic materials. The geological model indicates that these deposits show a sporadic development becoming more concentrated in the central west part of the city. (2) Colentina Formations composed by of poorly sorted, cross-stratified sand and gravel with clayey lens indicating a high energy deposition environment. The geological model indicates more accentuate vertical lithological heterogeneity than a horizontal one as well as a decrease of the Colentina Formation thickness. (3) Intermediary deposits represented by silty-clay with fine sand intercalation indicating a mixed regime with limited lakes and dry lands. (4) Mostistea Formation made of sediments with a variety of grain size, from fine sand to coarse sand with small intercalations of gravels and scrap of woods. It was found that areas where the Intermediary deposits are less developed making the Colentina Formation in direct connection to Mostistea Formation. (5) Marly Complex composed by a succession of marls and clays with lenticular sandy intercalations indicating a fluvial-lacustrine environment. (6) Fratesti Strata made of sand and gravel which includes A, B and C Fratesti levels.

  7. Electrodeposition of iron-cobalt-nickel-copper quaternary system

    NASA Astrophysics Data System (ADS)

    Huang, Qiang

    Electrodeposition is a cost-effective method to produce thin film materials, which have been used widely in the microelectronic industry, and is advantageous to fabricate metal deposits into recessed and curved areas. In this dissertation, a FeCoNiCu quaternary alloy system was investigated, both experimentally and theoretically, for fabrication of multilayers, grating structures, and nanowires. Multilayer structures are composed of alternating ferromagnetic and nonmagnetic nanometric layers, and are of interest due to the giant magnetoresistance (GMR) property it possesses, a change in electric resistance in the presence of an external magnetic field. In addition, the compositional modulation, or the composition contrast, in multilayer structures can be used to develop a grating structured mold for the development of a novel nanoimprinting process. FeCoNiCu was investigated as a more general alloy system containing iron-group metals and a nonmagnetic element, Cu, which can be simplified and adapted to any binary or ternary systems. With a dilute tartrate sulfate bath nanometric multilayers were successfully fabricated with pulse plating and GMR value was reported for this electrodeposited system for the first time. A value of -6% was achieved on rotating disk electrode (RDE) and this maximum occurred when the structure had no preferred crystal phase. Over 40% GMR has been achieved when the multilayer was plated onto a polycrystalline Cu foil. A mathematical model was developed to tailor the deposition process on RDE, and both steady state and nonsteady state cases were simulated. A compositional gradient, which is inherent to a nonsteady state deposition process when the layer size is of nanometer scale was predicted. The quaternary system was explored for other applications. Selective etching of electrodeposited multilayer structures was investigated for different etching solutions. A diluted K2Cr2O 7/H2SO4 solution was successfully developed to produce grating structures for a nanoimprinting mold, which was demonstrated with a simple cast molding process. In addition, nanowire plating was explored with different plating schemes. Nanowires of multilayers were successfully fabricated, and the nanometric layer structure was verified. A deviation was observed in the layer thickness from DC plating, as a result of the nonsteady state plating process, consistent with the model developed.

  8. Quantifying glacial erosion in the European Alps using apatite fission track dating

    NASA Astrophysics Data System (ADS)

    Wangenheim, Cornelia; Glotzbach, Christoph

    2015-04-01

    To investigate the impact of glacial erosion on landscape evolution during the Quaternary, problems may occur in choosing the best method, because many methods only reflect parts of the era. Erosion rate calculations based on cosmogenic nuclides only cover the Holocene and erosion rate calculations based on river load gauging reflect even shorter timescales (e.g. von Blanckenburg 2005). In this study we investigate the potential of thermochronological methods, especially apatite fission track dating (AFT) to quantify glacial erosion in the European Alps. The topography of the European Alps is strongly influenced by Quaternary glaciations, as it formed characteristic features like overdeepened and hanging valleys. The study area is located in the Central Alps of Switzerland, which is a high mountain area. At ~0.9 Ma glacial erosion has led to a considerable increase in valley incision rates in this area (Haeuselmann et al. 2007) and therefore it is ideally suited to study the glacial impact on landscape evolution. The advantage of using AFT dating, while studying changes in erosional processes, is that possibly arising nonsteady-state erosion will be recorded within the spatial distribution of thermochronological ages. In this study we applied AFT dating on both bedrock and sediments. The bedrock samples derive from different elevations to figure out whether or not spatial differences and elevation dependencies exist. Combined with already published data we have a relatively high sample density distributed throughout the whole study area. The detrital samples originate from stream sediments and from glacial deposits in the form of late glacial moraines and cave sediments from the last ~0.5 Ma in order to obtain possible lateral variations in erosion. The AFT ages of the bedrocks vary between ~4 Ma and ~9 Ma, resulting in an average long-term exhumation rate of ~0.5 km/Ma. Most of the ages range between 7 and 9 Ma, confirmed by prevailing ages of stream sediment samples. The bedrock age distribution of this area indicates that ages do not only increase with elevation, they also show a distinct local trend along major valleys. This trend may be at least partly caused by focused valley incision during glaciations (Shuster et al. 2011), as the youngest ages appear around the position of the equilibrium line altitude of the Last Glacial Maximum, where it is assumed that Quaternary glacial erosion reached an integrative maxima. Haeuselmann, P. Granger, D. E. Jeannin, P.-Y. and Lauritzen, S.-E. (2007): Abrupt glacial valley incision at 0.8 Ma dated from cave deposits in Switzerland. - Geology 35, 143-146. Shuster, D. L., Cuffey, K. M., Sanders, J. W. and Balco, G. (2011): Thermochronometry reveals headward propagation of erosion in alpine landscape. - Science 332, 84-88. von Blanckenburg, F. (2005): The control mechanisms of erosion and weathering at basin scale from cosmogenic nuclides in river sediment. - Earth and Planetary Science Letters 237, 462 - 479.

  9. Nanoscopic mechanisms of singlet fission in amorphous molecular solid Weiwei Mou,1

    E-print Network

    Southern California, University of

    Nanoscopic mechanisms of singlet fission in amorphous molecular solid Weiwei Mou,1 Shinnosuke; accepted 26 February 2013; published online 29 April 2013) Fission of a spin-singlet exciton into two-flow-network topology for singlet- fission "hot spots" in amorphous diphenyl tetracene, where fission occurs

  10. Memory of the entrance-channel K distribution observed in fission at high angular momentum

    Microsoft Academic Search

    C. R. Morton; A. C. Berriman; R. D. Butt; M. Dasgupta; A. Godley; D. J. Hinde; J. O. Newton

    2000-01-01

    Fission and evaporation residue cross sections, and fission fragment anisotropies, for the reaction 34S+168Er have been measured to energies where the fission barrier no longer controls the fission process. Anisotropies calculated with the transition state model were found to be in excess of the measured anisotropies. Such an effect can be explained by assuming that the high angular momentum trajectories

  11. Langevin analysis of fission excitation functions induced by protons

    NASA Astrophysics Data System (ADS)

    Tian, Jian; Wang, Ning; Ye, Wei

    2015-03-01

    The stochastic Langevin approach to fission is applied to analyze fission excitation functions measured in p+206Pb and p+209Bi systems. A presaddle friction strength of (3–5) × 1021 s?1 is extracted by comparing theoretical predictions with experimental data. Furthermore, the small distortion of the formed compound nuclei with respect to the spherical shape under the condition of low angular momentum suggests that experimentally, populating an excited compound system via light-ion induced reactions favors a more accurate determination of presaddle friction with a fission cross section. Supported by National Nature Science Foundation of China (11075034)

  12. Singlet exciton fission in polycrystalline pentacene: from photophysics toward devices.

    PubMed

    Wilson, Mark W B; Rao, Akshay; Ehrler, Bruno; Friend, Richard H

    2013-06-18

    Singlet exciton fission is the process in conjugated organic molecules bywhich a photogenerated singlet exciton couples to a nearby chromophore in the ground state, creating a pair of triplet excitons. Researchers first reported this phenomenon in the 1960s, an event that sparked further studies in the following decade. These investigations used fluorescence spectroscopy to establish that exciton fission occurred in single crystals of several acenes. However, research interest has been recently rekindled by the possibility that singlet fission could be used as a carrier multiplication technique to enhance the efficiency of photovoltaic cells. The most successful architecture to-date involves sensitizing a red-absorbing photoactive layer with a blue-absorbing material that undergoes fission, thereby generating additional photocurrent from higher-energy photons. The quest for improved solar cells has spurred a drive to better understand the fission process, which has received timely aid from modern techniques for time-resolved spectroscopy, quantum chemistry, and small-molecule device fabrication. However, the consensus interpretation of the initial studies using ultrafast transient absorption spectroscopy was that exciton fission was suppressed in polycrystalline thin films of pentacene, a material that would be otherwise expected to be an ideal model system, as well as a viable candidate for fission-sensitized photovoltaic devices. In this Account, we review the results of our recent transient absorption and device-based studies of polycrystalline pentacene. We address the controversy surrounding the assignment of spectroscopic features in transient absorption data, and illustrate how a consistent interpretation is possible. This work underpins our conclusion that singlet fission in pentacene is extraordinarily rapid (?80 fs) and is thus the dominant decay channel for the photoexcited singlet exciton. Further, we discuss our demonstration that triplet excitons generated via singlet fission in pentacene can be dissociated at an interface with a suitable electron acceptor, such as fullerenes and infrared-absorbing inorganic semiconducting quantum dots. We highlight our recent reports of a pentacene/PbSe hybrid solar cell with a power conversion efficiency of 4.7% and of a pentacene/PbSe/amorphous silicon photovoltaic device. Although substantive challenges remain, both to better our understanding of the mechanism of singlet exciton fission and to optimize device performance, this realization of a solar cell where photocurrent is simultaneously contributed from a blue-absorbing fission-capable material and an infrared-absorbing conventional cell is an important step towards a dual-bandgap, single-junction, fission-enhanced photovoltaic device, which could one day surpass the Shockley-Queisser limit. PMID:23656886

  13. The discovery and spontaneous fission properties of /sup 262/No

    SciTech Connect

    Lougheed, R.W.; Hulet, E.K.; Wild, J.F.; Moody, K.J.; Dougan, R.J.; Gannett, C.M.; Henderson, R.A.; Hoffman, D.C.; Lee, D.M.

    1989-04-19

    We have discovered /sup 262/No, as the electron capture daughter of /sup 262/Lr(t/sub 1/2/ = 216 m). This new isotope of nobelium decays by spontaneous fission with about a 5-ms half-life which is several orders of magnitude longer than recent theoretical estimates. We measured a sharply symmetric fission-fragment mass division and a bimodal total kinetic energy distribution; the high-energy symmetric-fission path was most abundant. /sup 262/No is the first nuclide with 160 neutrons to be discovered and is the closest to the N = 162 neutron subshell for which enhanced stability is predicted. 14 refs., 3 figs.

  14. Diabetes regulates mitochondrial biogenesis and fission in mouse neurons

    Microsoft Academic Search

    J. L. Edwards; A. Quattrini; S. I. Lentz; C. Figueroa-Romero; F. Cerri; C. Backus; Y. Hong; E. L. Feldman

    2010-01-01

    Aims\\/hypothesis  Normal mitochondrial activity is a critical component of neuronal metabolism and function. Disruption of mitochondrial activity\\u000a by altered mitochondrial fission and fusion is the root cause of both neurodegenerative disorders and Charcot–Marie–Tooth\\u000a type 2A inherited neuropathy. This study addressed the role of mitochondrial fission in the pathogenesis of diabetic neuropathy.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Mitochondrial biogenesis and fission were assayed in both in vivo

  15. Fission-suppressed blankets for fissile fuel breeding fusion reactors

    NASA Astrophysics Data System (ADS)

    Lee, J. D.; Moir, R. W.

    1981-07-01

    Two blanket concepts for deuterium-tritium (DT) fusion reactors are presented which maximize fissile fuel production while at the same time suppress fission reactions. By suppressing fission reactions, the reactor will be less hazardous, and therefore easier to design, develop, and license. A fusion breeder operating a given nuclear power level can produce much more fissile fuel by suppressing fission reactions. The two blankets described use beryllium for neutron multiplication. One blanket uses two separate circulating molten salts: one salt for tritium breeding and the other salt for U-233 breeding. The other uses separate solid forms of lithium and thorium for breeding and helium for cooling.

  16. Fission decay of $^{282}$Cn studied using cranking inertia

    E-print Network

    D. N. Poenaru; R. A. Gherghescu

    2014-11-03

    Superheavy nuclei produced until now are decaying mainly by $\\alpha$ emission and spontaneous fission. Calculated $\\alpha$ decay half-lives are in agreement with experimental data within one order of magnitude. The discrepancy between theory and experiment can be as high as ten orders of magnitude for spontaneous fission. We analyze a way to improve the accuracy by using the action integral based on cranking inertia and a potential barrier computed by the macroscopic-microscopic method with a two-center shell model. Illustrations are given for $^{282}$Cn which has a measured fission half-life.

  17. Fission Potential Energy Surfaces in Ten-Dimensional Deformation Space

    NASA Astrophysics Data System (ADS)

    Pashkevich, V.; Pyatkov, Y.; Unzhakova, A.

    Various fission processes are described in terms of high-dimensional potential energy surface in the frame of the Strutinsky shell correction method for actinide region. The complete deformation space is necessary to study the potential energy minima responsible for the cluster radioactivity, cold fission and cold multi-fragmentation valleys. The nuclear shape families for the different fission configurations are obtained without any specific change of the parameters. The coordinate system based on the Cassini ovaloids makes it possible to increase the number of independent deformation parameters without divergence. The higher orders of the deformation are shown to play an important role in the description of the potential energy surface structure.

  18. Chemistry of fission product iodine under nuclear reactor accident conditions

    SciTech Connect

    Malinauskas, A.P.; Bell, J.T.

    1986-01-01

    The radioisotopes of iodine are generally acknowledged to be the species whose release into the biosphere as a result of a nuclear reactor accident is of the greatest concern. In the course of its release, the fission product is subjected to differing chemical environments; these can alter the physicochemical form of the fission product and thus modify the manner and extent to which release occurs. Both the chemical environments which are characteristic of reactor accidents and their effect in determining physical and chemical form of fission product iodine have been studied extensively, and are reviewed in this report. 76 refs.

  19. Superlinear density dependence of singlet fission rate in tetracene films

    E-print Network

    Zhang, Bo; Wang, Rui; Tan, Zhanao; Liu, Yunlong; Guo, Wei; Zhai, Xiaoling; Wang, Xiaoyong; Xiao, Min

    2014-01-01

    We experimentally show that the rate of singlet fission in tetracene films has a superlinear dependence on the density of photo-excited singlet excitons with ultrafast transient absorption spectroscopy. The spectrotemporal features of singlet and triplet dynamics can be disentangled from experimental data with the algorithm of singular value decomposition. The correlation between their temporal dynamics indicates a nonlinear density dependence of fission rate, which leads to a conjecture of coherent singlet fission process arising from superradiant excitons in crystalline tetracene. This hypothesis might be able to resolve some long-standing controversies.

  20. Nanoscopic mechanisms of singlet fission in amorphous molecular solid

    NASA Astrophysics Data System (ADS)

    Mou, Weiwei; Hattori, Shinnosuke; Rajak, Pankaj; Shimojo, Fuyuki; Nakano, Aiichiro

    2013-04-01

    Fission of a spin-singlet exciton into two triplet excitons, if realized in disordered organic solid, could revolutionize low-cost fabrication of efficient solar cells. Here, a divide-conquer-recombine approach involving nonadiabatic quantum molecular dynamics and kinetic Monte Carlo simulations identifies the key molecular geometry and exciton-flow-network topology for singlet-fission "hot spots" in amorphous diphenyl tetracene, where fission occurs preferentially. The simulation reveals the molecular origin of experimentally observed two time scales in exciton population dynamics and may pave a way to nanostructural design of efficient solar cells from first principles.