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1

Fission-track evidence for Quaternary uplift of the Nanga Parbat region, Pakistan  

USGS Publications Warehouse

The north-striking Nanga Parbat-Haramosh Massif protrudes into the northwestern Himalaya along the axis of a great syntaxis1,2 (Fig. 1), where the Hindu Kush, Karakorum, and Himalayan ranges converge. As the Indus Suture Zone3 enters this region from the east it bifurcates into two branches, encircling what may be a docked island-arc terrane4. The southern branch (the Main Mantle Thrust) crops out on both flanks of the Nanga Parbat massif, forming a tight structural loop5. This massif and the adjacent terrane contain some of the highest peaks in the Himalaya; Nanga Parbat and the Indus River (located just 20km away) define the world's greatest continental relief (6,930 m). We report here the discovery of unexpectedly young sphene, zircon and apatite fission-track dates from the Nanga Parbat-Haramosh Massif. These dates (as low as 1.3 Myr for zircon and 0.4 Myr for apatite) imply that during the Pleistocene the Nanga Parbat region was uplifted and eroded at nearly 1 cm yr-1. ?? 1982 Nature Publishing Group.

Zeitler, P. K.; Johnson, N. M.; Naeser, C. W.; Tahirkheli, R. A. K.

1982-01-01

2

Timing, quantification and tectonic modelling of Pliocene-Quaternary movements in the NW Himalaya: evidence from fission track dating  

NASA Astrophysics Data System (ADS)

Variable exhumation rates, deduced from the Pliocene-Quaternary FT zircon-apatite ages from the Himalayan Metamorphic Belt (HMB) of the NW Himalaya along the Sutlej Valley in Himachal Pradesh, have been modelled in the tectonic framework of fast exhumed Lesser Himalayan windows, which caused lateral extensional sliding of the metamorphic nappe cover along the well-known Main Central Thrust (MCT) and differential movements along thrust zones as well. In the northern belt of the Higher Himalayan Crystallines (HHC), two distinct clusters of the FT apatite ages have been deciphered: apatite ages having a weighted mean of 4.9±0.2 Ma (1 ?) in basal parts on the hanging wall of the MCT, and 1.49±0.07 Ma (1 ?) in the hanging wall of a newly, recognized NE, dipping Chaura thrust further north. Fast exhumation of the Chaura thrust hanging wall has been inferred at a rate of 4.82±0.55 mm/yr from the zircon-apatite cogenetic pairs during 1.54 Ma and 0.97 Ma, and 2.01±0.35 mm/yr since 1.49 Ma. In comparison, its foot wall has been exhumed at a much slower rate of 0.61±0.10 mm/yr since 4.9 Ma. The overlying Vaikrita Thrust zone rocks reveal an exhumation rate of 1.98±0.34 mm/yr from 2.70±0.40 Ma to 1.31±0.22 Ma and 2.29±0.66 mm/yr since 1.31±0.22 Ma. Using these data, a vertical displacement of ca. 2.08±0.68 km has been calculated along the Chaura thrust between 4.9 and 1.50 Ma on an average rate of 0.6 mm/yr. It is of the order of 1.18 km from 2.70 Ma to 1.54 Ma along the Vaikrita Thrust, and 0.78 mm/yr from 1.31 Ma to 0.97 Ma, and has behaved as an extensional normal fault during these periods. Tectonic modelling of the exhumation rates in the NW Himalaya reveals fastest uplifting Himalayan domes and windows like the Nanga Parbat in Pakistan, Suru and Chisoti domes in Zanskar and Kishwar-Kulu-Rampur Window axis in SE Kashmir and Himachal Pradesh during Pliocene-Quaternary. These windows appear to have caused lateral extensional sliding of the Himalayan metamorphic nappes in the lower parts. The middle parts of the HHC belt have witnessed both overthrusting and extensional faulting due to complex and variable exhumation patterns within the hanging and foot walls of the MCT and Vaikrita Thrust along the Sutlej Valley, thus causing movement of upthrust crustal wedge between the extensional ones. Thus, FT zircon-apatite ages provide evidence for the presence of a number of crustal wedges having distinct tectonothermal history within the HHC.

Jain, A. K.; Kumar, Devender; Singh, Sandeep; Kumar, Ashok; Lal, Nand

2000-07-01

3

Detrital fission-track-compositional signature of an orogenic chain-hinterland basin system: The case of the late Neogene Quaternary Valdelsa basin (Northern Apennines, Italy)  

NASA Astrophysics Data System (ADS)

Detrital thermochronological data collected in syn-tectonic basin deposits are a promising tool for deciphering time and processes of the evolution of orogenic belts. Our study deals with the Valdelsa basin, one of the wider basins of central Tuscany, Italy. The Valdelsa basin is located at the rear of the Northern Apennines, a collisional orogen whose late Neogene Quaternary development is alternatively attributed to extensional and compressional regimes. These contrasting interpretations mostly rely on different reconstructions of the tectono-sedimentary evolution of several basins formed at the rear of the chain since the late Tortonian. Here, we explore the detrital thermochronological-compositional signature of tectonic and surface processes during the Valdelsa basin development. For this aim, detrital apatite fission-track analysis of 21 sand samples from the latest Messinian Gelasian fluvial to shallow marine basin deposits, has been accompanied by a clast composition analysis of 7 representative outcrops of the conglomerate facies. The grain-age distributions of the sediment samples are generally characterized by two distinct components, one younger peak (P1) varying between 5.5 ± 2.8 and 9.5 ± 1.0 Ma and one older peak (P2) varying from 15.0 ± 8.0 to 41.0 ± 10 Ma. By comparison with some bedrock ages obtained from the E-NE basin shoulder, we attributed the P2 peak to the Ligurian Units and the P1 peak to the Macigno Formation (Tuscan Units). These units are arranged one upon the other in the complex nappe pile forming the Northern Apennines orogen. While the gravel composition indicates a predominant feeding from the Ligurian units all along the sedimentary succession with a subordinate occurrence of Macigno pebbles slightly increasing upsection, the P1 peak is present even in the oldest collected sandy sediments. The early P1 occurrence reveals that the Macigno was exposed in the E-NE basin shoulder since at least the latest Messinian-early Zanclean. This means that deeper part of the structural edifice was exposed earlier than previously reported. This was likely made possible by exposures of Macigno at the cores of anticlines or on the footwall of backthrusts. Thus, the Macigno early supply claims a role for shortening in the Northern Apennines hinterland basin evolution. Our study revealed the suitability of the detrital thermochronological/compositional analysis on syn-tectonic infill of hinterland basins in discriminating between different tectonic processes affecting the late evolution of an orogenic chain.

Balestrieri, M. L.; Benvenuti, M.; Tangocci, F.

2013-05-01

4

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.

5

Quaternary investigation  

SciTech Connect

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.

Stieve, A.

1991-05-15

6

The Alaska Quaternary Center  

NSDL National Science Digital Library

This website illustrates the Alaska Quaternary Center's (at the University of Alaska, Fairbanks) commitment "to the promotion of interdisciplinary research and the enhancement of interdisciplinary instruction in Quaternary sciences." Users can view images of the field work and learn how to obtain quaternary data from the AQC Quaternary Research Geodatabase.

1969-12-31

7

Quaternary and Geomorphology.  

ERIC Educational Resources Information Center

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"…

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

1983-01-01

8

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.

1969-12-31

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

Quaternary Alloy Microwave MESFET.  

National Technical Information Service (NTIS)

Liquid phase epitaxial growth techniques have been used to grow quaternary alloys, Ga sub 1-x In sub x P sub 1-y As sub y, on InP substrates, using (100), (111) A and (111) B orientations. Liquidus and solidus data at 660 C have been used to determine dis...

J. W. Harrison S. B. Phatak M. A. Littlejohn G. Kelner H. H. Stadelmaier

1979-01-01

11

Quaternary Faunal Environments  

NSDL National Science Digital Library

Students collect information the environments associated with a list of presently living mammals. Students use FAUNMAP to explore the spatial patterns associated with these living mammals during the late Quaternary. They compare these distributions for living mammals to the distribution patterns for a set of extinct mammals. Students answer a set of questions that provide a basis for a summary report.

Hill, Christopher

12

Fission meter  

DOEpatents

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.

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

2012-04-10

13

Topic in Depth - Quaternary Studies  

NSDL National Science Digital Library

Quaternary Studies examines the geologic period of the Quaternary, the last two million years up to the present day. Glaciers formed and receded; animals evolved and went extinct. Here, visitors can learn all about current research and education initiatives in this field of stratigraphic geology.

2010-09-14

14

Ternary Fission Studies by Correlation Measurements with Ternary Particles  

NASA Astrophysics Data System (ADS)

The rare ternary fission process has been studied mainly by inclusive measurements of the energy distributions and fractional yields of the light charged particles (LCPs) from fission, or by experiments on the angular and energy correlation between LCPs and fission fragments (FFs). The present contribution presents a brief overview of more elaborate correlation measurements that comprise the emission of neutrons and ? rays with LCPs and FFs, or the coincident registration of two LCPs. These measurements have permitted identification of new modes of particle-accompanied fission, such as the population of excited states in LCPs, the formation of neutron-unstable nuclei as short-lived intermediate LCPs, as well as the sequential decay of particle-unstable LCPs and quaternary fission. Furthermore, the neutron multiplicity numbers bar ? (A) and distributions of fragment masses A, measured for the ternary fission modes with various LCP isotopes, give a valuable hint of the role played by nuclear shell structure in the fission process near scission. Finally, two different hitherto unknown asymmetries in ternary ?-particle emission with respect to the fission axis, called the TRI and ROT effect, were studied in fission reactions induced by polarised cold neutrons.

Mutterer, Manfred

2011-10-01

15

Quantum realization of some quaternary circuits  

Microsoft Academic Search

We present the design of quaternary quantum version of reversible circuits such as Toffoli gate, modified Fredkin gate, mux, demux, encoder-decoder using linear ion realizable quaternary Muthukrishnan-Stroud gates. Our realization of quaternary Toffoli gate is more efficient than the previous realization and other quaternary circuits are realized for the time in literature.

Mahmud Muntakim Khan; Ayan Kumar Biswas; Shuvro Chowdhury; M. Tanzid; K. M. Mohsin; M. Hasan; A. I. Khan

2008-01-01

16

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.

17

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.

2007-02-27

18

Synthesis of Quaternary Heterocyclic Salts  

PubMed Central

The microwave synthesis of twenty quaternary ammonium salts is described. The syntheses feature comparable yields to conventional synthetic methods reported in the current literature with reduced reaction times and the absence of solvent or minimal solvent.

Winstead, Angela J.; Nyambura, Grace; Matthews, Rachael; Toney, Deveine; Oyaghire, Stanley

2014-01-01

19

Fissionable nuclear fuel composition  

Microsoft Academic Search

This patent describes a fissionable nuclear composition for service in a nuclear reactor fuel core consisting essentially of a ceramic body of fissionable oxide fuel material selected from the group. It consists of uranium oxides, plutonium oxide and thorium oxides, and mixtures thereof, and containing dispersed throughout the ceramic body of fissionable oxide fuel material at least one boron depletable

R. A. Proebstle; M. O. Marlowe; A. P. Reese

1991-01-01

20

Late Quaternary vegetation - climate feedbacks  

Microsoft Academic Search

Feedbacks between vegetation and other components of the climate system are discussed with respect to their influence on climate dynamics during the late Quaternary, i.e., the last glacial - interglacial cycles. When weighting current understanding based on interpretation of palaeobotanic and palaeoclimatic evidence by numerical climate system models, a number of arguments speak in favour of vegetation dynamics being an

M. Claussen

2009-01-01

21

Quaternary ecology: A paleoecological perspective  

SciTech Connect

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.

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

1991-01-01

22

40 CFR 721.10582 - Quaternary ammonium compound (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Quaternary ammonium compound (generic). 721.10582 Section... § 721.10582 Quaternary ammonium compound (generic). (a) Chemical substance...identified generically as quaternary ammonium compound (PMN P-10-571) is subject...

2013-07-01

23

40 CFR 721.655 - Ethoxylated alkyl quaternary ammonium compound.  

Code of Federal Regulations, 2013 CFR

...Ethoxylated alkyl quaternary ammonium compound. 721.655 Section 721.655 ...Ethoxylated alkyl quaternary ammonium compound. (a) Chemical substance and significant...ethoxylated alkyl quaternary ammonium compound (PMN P-96-573) is subject...

2013-07-01

24

Relativistic Coulomb Fission  

NASA Technical Reports Server (NTRS)

Nuclear fission reactions induced by the electromagnetic field of relativistic nuclei are studied for energies relevant to present and future relativistic heavy ion accelerators. Cross sections are calculated for U-238 and Pu-239 fission induced by C-12, Si-28, Au-197, and U-238 projectiles. It is found that some of the cross sections can exceed 10 b.

Norbury, John W.

1992-01-01

25

Fission gas detection system  

DOEpatents

A device for collecting fission gas released by a failed fuel rod which device uses a filter to pass coolant but which filter blocks fission gas bubbles which cannot pass through the filter due to the surface tension of the bubble.

Colburn, Richard P. (Pasco, WA)

1985-01-01

26

Fission of metal clusters  

Microsoft Academic Search

Experimental results on the fission of doubly and other multiply charged metal clusters are reviewed and examined in the light of a simple model, where the fission barrier is approximated as two charged spheres in near-contact, at a mutual distance given by the balance between Coulomb repulsion and attractive polarization effects. The barriers are estimated for different mass and charge

U. Naher; S. Bjornholm; S. Frauendorf; F. Garcias; C. Guet

1997-01-01

27

Fission Xenon on Mars  

NASA Technical Reports Server (NTRS)

Fission Xe components due to Pu-244 decay in the early history of Mars have been identified in nakhlites; as in the case of ALH84001 and Chassigny the fission gas was assimilated into indigenous solar-type Xe. Additional information is contained in the original extended abstract.

Mathew, K. J.; Marti, K.; Marty, B.

2002-01-01

28

Isomers in Fission Fragments  

NASA Astrophysics Data System (ADS)

The structure of neutron-rich nuclei produced as secondary fission fragments was investigated using the EUROGAM and GAMMASPHERE ACS arrays, the LOHENGRIN fission-fragment mass separator and the FIFI fission-fragment identifier. Fission products were populated in spontaneous fission of 248Cm and 252Cf and in thermal neutron-induced fission of 233U, 235U and 241Pu at ILL Grenoble. Particularly useful in such studies are isomeric states, well populated in fission due to their yrast character, easy to detect due to their long half lives and easy to interpret because of their relatively simple composition. We discuss their role in studies of neutron-rich nuclei, giving examples of isomers found in our recent experiments. A special type of K-isomers, resulting from `crossing' of extruder and intruder orbitals plays a role in the mechanism of a sudden onset of deformation in the A = 100 and A = 150 regions. We present evidence for these isomers in both regions. Possible further studies in this field are proposed.

Urban, W.; Faust, H.; Jentschel, M.; Köster, U.; Krempel, J.; Materna, Th.; Mutti, P.; Soldner, T.; Genevey, J.; Pinston, J. A.; Simpson, G.; RzaCa-Urban, T.; Z?omaniec, A.; ?ukasiewicz, M.; Sieja, K.; Nowacki, F.; Dorvaux, O.; Gall, B. J. P.; Roux, B.; Dare, J. A.; Durell, J. L.; Smith, A. G.; Varley, B. J.; Tsekhanovich, I.; Jolie, J.; Linnemann, A.; Scherillo, A.; Orlandi, R.; Smith, J. F.; Ahmad, I.

2009-01-01

29

Fission induced plasmas  

NASA Technical Reports Server (NTRS)

The possibility of creating a plasma from fission fragments was investigated, as well as the probability of utilizing the energy of these particles to create population inversion leading to laser action. Eventually, it is hoped that the same medium could be used for both fissioning and lasing, thus avoiding inefficiences in converting one form of energy to the other. A central problem in understanding a fission induced plasma is to obtain an accurate model of the electron behavior; some calculations are presented to this end. The calculations are simple, providing a compendium of processes for reference.

Harries, W. L.

1977-01-01

30

Nuclear fission of Fm isotopes  

SciTech Connect

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.

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

31

Fission products experimental programme  

SciTech Connect

The 'Fission Products (FPs)' experimental programme was carried out from 1998 to 2004 in CEA/Valduc Apparatus B in the framework of the IRSN-AREVA NC Common Interest Program dealing with 'burnup credit' studies. It aims at compensating for the lack of critical experiments with FPs in the literature and validating a selection of 6 stable, non-volatile, fission products representing half of the irradiated fuel absorption of all fission products: {sup 103}Rh, {sup 133}Cs, {sup 143}Nd, {sup 149}Sm, {sup 152}Sm and {sup 155}Gd. This paper provides a more exhaustive approach of the k{sub eff} results, uncertainties and tendencies associated with the different steps of the 'Fission Products' programme. (authors)

Leclaire, N. [Institut de Radioprotection et de Surete Nucleaire IRSN, BP 17, 92262 Fontenay-aux-Roses Cedex (France); Anno, J. [Commissariat a l'Energie Atomique CEA, Institut de Protection et de Surete Nucleaire (CEA/IPSN) (France); Girault, E. [Commissariat a l'Energie Atomique CEA, Centre de Valduc, 21120 Is-Sur-Tille (France); Letang, E. [Institut de Radioprotection et de Surete Nucleaire IRSN, BP 17, 92262 Fontenay-aux-Roses Cedex (France)

2006-07-01

32

Fission Systems for Mars Exploration  

NASA Technical Reports Server (NTRS)

Fission systems are used extensively on earth, and 34 such systems have flown in space. The energy density of fission is over 10 million times that of chemical reactions, giving fission the potential to eliminate energy density constraints for many space missions. Potential safety and operational concerns with fission systems are well understood, and strategies exist for affordably developing such systems. By enabling a power-rich environment and highly efficient propulsion, fission systems could enable affordable, sustainable exploration of Mars.

Houts, Michael G.; Kim, T.; Dorney, D. J.; Swint, Marion Shayne

2012-01-01

33

Microscopic Theory of Fission  

SciTech Connect

In recent years, the microscopic method has been applied to the notoriously difficult problem of nuclear fission with unprecedented success. In this paper, we discuss some of the achievements and promise of the microscopic method, as embodied in the Hartree-Fock method using the Gogny finite-range effective interaction, and beyond-mean-field extensions to the theory. The nascent program to describe induced fission observables using this approach at the Lawrence Livermore National Laboratory is presented.

Younes, W.; Gogny, D. [Lawrence Livermore National Laboratory, Livermore, CA 94550 (United States)

2008-04-17

34

Spatial- and Time-Correlated Detection of Fission Fragments  

NASA Astrophysics Data System (ADS)

With the goal to measure angular correlations of fission fragments in rare fission decay (e.g. ternary and quaternary fission), a multi-detector coincidence system based on two and up to four position sensitive pixel detectors Timepix has been built. In addition to the high granularity, wide dynamic range and per pixel signal threshold, these devices are equipped with per pixel energy and time sensitivity providing more information (position, energy, time), enhances particle-type identification and selectivity of event-by-event detection. Operation of the device with the integrated USB 2.0 based readout interface FITPix and the control and data acquisition software tool Pixelman enables online visualization and flexible/adjustable operation for a different type of experiments. Spatially correlated fission fragments can be thus registered in coincidence. Similarly triggered measurements are performed using an integrated spectrometric module with analogue signal chain electronics. The current status of development together with demonstration of the technique with a 252Cf source is presented.

Granja, C.; Kraus, V.; Kopatch, Y.; Telezhnikov, S. A.; Vacik, J.; Tomandl, I.; Platkevic, M.; Pospisil, S.

2012-02-01

35

Microscopic description of fission properties  

SciTech Connect

Microscopic results on fission barriers, partial {gamma}-back and fission lifetimes of shape isomers are presented. They have been obtained from mean-field and beyond mean-field calculations using the effective D1S Gogny force.

Goutte, H.; Delaroche, J.-P.; Girod, M. [CEA/DAM Ile de France, DPTA/Service de Physique Nucleaire, BP 12, 91680 Bruyeres-le-Chatel (France); Libert, J. [Institut de Physique Nucleaire, CNRS-IN2P3 and Universite Paris XI, 15 rue Georges Clemenceau, 91406 Orsay (France)

2007-02-26

36

Quaternary glaciation of Mount Everest  

NASA Astrophysics Data System (ADS)

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.

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

37

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

NASA Astrophysics Data System (ADS)

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.

Stewart, John R.; Cooper, Alan

2008-12-01

38

Constraints from fission track analysis on the evolution of the Rio Tinguiririca valley area in the Main Cordillera of the Andes, Central Chile  

Microsoft Academic Search

In the Rio Tinguiririca valley in the Main Cordillera of the Andes of central Chile, 35° south, parts of a stratigraphic section ranging from the late Jurassic to the Quaternary are exposed. Fission track analysis was carried out on samples from all the stratigraphic units exposed in the area in order to gain information on the low-grade metamorphic history of

K. Waite; S. Schmidt

2005-01-01

39

Pulsed Fission Propulsion Concept  

NASA Technical Reports Server (NTRS)

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.

1999-01-01

40

Pulsed Fission Propulsion Concept  

NASA Technical Reports Server (NTRS)

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.

1999-01-01

41

Fusion-fission dynamics.  

National Technical Information Service (NTIS)

Classical dynamical calculations of the heavy ion induced fission process for the reactions (sup 40)Ar+(sup 141)Pr, (sup 20)Ne+(sup 165)Ho and (sup 12)C+(sup 175)Lu leading to the iridium like nucleus have been performed. As a result prescission lifetimes...

J. Blocki R. Planeta J. Brzychczyk K. Grotowski

1991-01-01

42

Fission and fusion dynamics  

Microsoft Academic Search

In part I a unified macroscopic approach to the field of fission and heavy ion fusion is stressed. The principal degrees of freedom relevant to this field are described. In the equations of motion there are three types of terms (potential, dissipative and inertial terms). The principal features of the potential energy landscape are illustrated qualitatively by means of an

W. J. Swiatecki; S. Bjørnholm

1972-01-01

43

Radiation Detection from Fission  

SciTech Connect

This report briefly describes the neutrons and gamma rays emitted in fission, briefly discusses measurement methods, briefly discusses sources and detectors relevant to detection of shielded HEU in sealand containers, and lists the measurement possibilities for the various sources. The brief descriptions are supplemented by reference.

Mihalczo, J.

2004-11-17

44

Clusterization in Ternary Fission  

NASA Astrophysics Data System (ADS)

This lecture notes are devoted to the new kind of ternary decay of low excited heavy nuclei called by us "collinear cluster tri-partition" (CCT) due to the features of the effect observed, namely, decay partners fly away almost collinearly and at least one of them has magic nucleon composition. At the early stage of our work the process of "true ternary fission" (fission of the nucleus into three fragments of comparable masses) was considered to be undiscovered for low excited heavy nuclei. Another possible prototype—three body cluster radioactivity—was also unknown. The most close to the CCT phenomenon, at least cinematically, stands so called "polar emission", but only very light ions (up to isotopes of Be) were observed so far.

Kamanin, D. V.; Pyatkov, Y. V.

45

[Fission product yields of 60 fissioning reactions]. Final report  

SciTech Connect

In keeping with the statement of work, I have examined the fission product yields of 60 fissioning reactions. In co-authorship with the UTR (University Technical Representative) Talmadge R. England ``Evaluation and Compilation of Fission Product Yields 1993,`` LA-UR-94-3106(ENDF-349) October, (1994) was published. This is an evaluated set of fission product Yields for use in calculation of decay heat curves with improved accuracy has been prepared. These evaluated yields are based on all known experimental data through 1992. Unmeasured fission product yields are calculated from charge distribution, pairing effects, and isomeric state models developed at Los Alamos National Laboratory. The current evaluation has been distributed as the ENDF/B-VI fission product yield data set.

Rider, B.F.

1995-05-01

46

Fission-induced plasmas  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

47

Investigation of the Soret effect in binary, ternary and quaternary hydrocarbon mixtures: New expressions for thermodiffusion factors in quaternary mixtures  

Microsoft Academic Search

Thermodiffusion or the Soret effect in binary, ternary and quaternary hydrocarbon mixtures is studied. Using the linear non-equilibrium thermodynamic (LNET) approach, expressions are derived for the estimation of the thermodiffusion coefficients or factors in quaternary mixtures using different approaches. New series of experimental data for binary, ternary and quaternary mixtures are used to evaluate the performance of the Firoozabadi, Kempers

Morteza Eslamian; M. Ziad Saghir; M. Mounir Bou-Ali

2010-01-01

48

Enantioselective construction of remote quaternary stereocentres.  

PubMed

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. PMID:24717439

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

2014-04-17

49

Enantioselective construction of remote quaternary stereocentres  

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

50

ADSORPTION MECHANISM OF QUATERNARY AMINES BY SEPIOLITE  

Microsoft Academic Search

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

E. Sabah; M. S. Çelik

2002-01-01

51

Quaternary deformation mapping with ground penetrating radar  

Microsoft Academic Search

Ground penetrating radar (GPR) was used in a programme of geological and hydrogeological investigations into the Quaternary of west Cumbria, UK. The investigations were part of an extensive programme to determine the suitability of the area for a deep radioactive waste repository. The hydrogeological characteristics of the drift deposits are important since they affect both recharge and discharge. The glacially

J. P Busby; J. W Merritt

1999-01-01

52

Quaternary Phosphonium Salts Bearing Carbamate Groups.  

National Technical Information Service (NTIS)

Novel quaternary phosphonium salts, bearing one or more carbamate groups attached through nitrogen, are prepared by condensing a hydroxymethyl phosphonium salt having the formula (R(4-n)P(CH2OH)n)(+)X(-) with an alkyl carbamate having the formula NH2CO2R'...

A. Frank

1979-01-01

53

Absolute chronology of the Pliocene-Quaternary sediment sequence of the Bogota area, Colombia  

NASA Astrophysics Data System (ADS)

A revised geochronological framework is presented for the sequence of unconsolidated sediments present in the Bogotá area (Eastern Cordillera, Colombia). This is based on 11 fission track dates on zircons that were obtained both from exposed ash layers and from a series of ashes from the Funza II borehole, which reached 586 m below the surface of the high plain. The 3 dates obtained from the exposed ash layers provide control for the older part of the sequence (6-2.5 Ma). The 8 dates from the Funza II core give control for the younger part of the sequence (3-0 Ma). Acceptance of these new fission track dates on volcanic zircons means that many of the tephra dates obtained from the Funza I core (that included fission track dates on glass shards and K?Ar dates using the mineral fractions in the ashes, published in 1984), are rejected. It also confirms earlier climate-stratigraphical dating. The Neogene-Quaternary sediments of the Bogotá area span a period of at least the last 6 Ma. The fluvial-lacustrine sediment record registers major tectonic uplift of the Eastern Cordillera for the period between 5 and 3 Ma, the development of the large sedimentary basin of Bogotá after 3.5 Ma, with an important phase of tectonic adjustment at about 1 Ma, and a long period of strong climatic fluctuations that started shortly after 2.7 Ma.

Andriessen, P. A. M.; Helmens, K. F.; Hooghiemstra, H.; Riezebos, P. A.; Van der Hammen, T.

54

Fission and Fusion Game  

NSDL National Science Digital Library

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.

55

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

NASA Astrophysics Data System (ADS)

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

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

56

Modern Pulsed Fission Propulsion Concept  

NASA Technical Reports Server (NTRS)

In the 1960's U.S. Government laboratories, under Project Orion, investigated a pulsed nuclear fission propulsion system. Based on Project Orion, an interplanetary vehicle using pulsed fission propulsion would incorporate modern technologies for momentum transfer, thermal management, and habitation design.

1999-01-01

57

Neogene and Quaternary development of the Western Carpathian lithosphere: impact on georelief and geohazards  

NASA Astrophysics Data System (ADS)

Some essential features of the Western Carpathian (and adjacent regions) lithosphere and land surface were created simultaneously in the Neogene and Quaternary. Synthesis of published as well as new geophysical, sedimentological, thermochronological and geomorphological data provide following results: Our newest morphostructural division and modelling of the crustal thickness fit together very well. Newly identified distinct core root under central part of the Western Carpatians explains rise of the annular morphostructural regions. Despite of variant possible reasons of creation of the isostatic disequilibrium, coupled morphological features suggest neotectonic (post Miocene) age. Re-evaluation of geophysical and geological data from the northern Danube Basin and Turiec Basin, together with new field-work and laboratory results formed the ground-work for a new determination of particular sedimentary facies and their changes in time and space. The results enable a better correlation of depositional and denudational history including formation of the system of planation surfaces. Apatite fission track data reflects mainly older Alpine orogenetic phases. However, the last uplift connected with the rise of modern topography is reflected by newest low-temperature termochronology data from the central part of the Western Carpathians. They specify the last stages of exhumation in the Pliocene and Pleistocene and define maximum age of preserved remnants of planation surfaces. A cosmogenic nuclide dating of deglaciation of the highest mountain (Tatras) suggests their quick Quaternary uplift, too. The Neogene and Quaternary development of the Western Carpathians projects onto distribution and intensity of recent geodynamic processes and subsequently natural hazards and risks. As an example the Quaternary development of the northernmost part of the Danubian Basin is presented (including changes of tectonic regime and river network as well as estimation of the erosion and deposition budged). Finally, an explanation of distribution of synthetic hazardous regions of the Western Carpathians in terms of their Neogene and Quaternary development is presented. Acknowledgments: This work was financially supported by the Slovak Research and Development Agency APVV under contract No. ESF—EC—0006—07.

Minár, J.; Ková?, M.; Bielik, M.; Hók, J.; Králiková, S.; Smetanová, A.; Šabo, M.; Vojtko, R.

2012-04-01

58

Quaternary neotectonics of the South Aegean arc  

Microsoft Academic Search

The sedimentary and tectonic Quaternary evolution of the South Aegean arc has been interpreted from 8000 line-km of sparker seismic reflection profiles. The older parts of basins formed by E–W-trending faults and accumulated hemipelagic sediment. Younger active faulting trends NNW in the western part of the arc and ENE in the eastern arc. The ENE-trending faults record sinistral strike-slip motion

D. J. W. Piper; C. Perissoratis

2003-01-01

59

Quaternary phylogeography: the roots of hybrid zones  

Microsoft Academic Search

The older history of hybrid zones is explored through consideration of recent advances in climatology, paleontology and phylogeography\\u000a in the Late Cenozoic, particularly the Quaternary Period with its major climatic cycles. The fossil record shows that these\\u000a ice ages and their nested millennial oscillations caused substantial changes in species distributions and with genetic evidence\\u000a allows deduction of refugia and colonization

Godfrey M. Hewitt

2011-01-01

60

Quaternary glaciations in the Northern Hemisphere  

SciTech Connect

This volume presents the final report of Project 24 of the International Geological Correlation Programme. The publication is drawn from the contributions of leading individual scientist as well as from scientific research teams. It reflects the present state of knowledge of the Quaternary Glaciations in the Northern Hemisphere and their correlation in space and time, as well as providing a unique summary of climatic change.

Sibrava, V.; Bowen, D.Q.; Richmond, G.M.

1987-01-01

61

The Fission Vision  

NSDL National Science Digital Library

Leo Szilard, a Hungarian physicist, imagined the two steps needed to free the energy in an atom's nucleus: one, a nuclear chain reaction, and two, a critical mass of the right element to set off and sustain it. Does he envision the process we now call "fission," the splitting of nuclei? Yes, he seems to, but Szilard's ideas are not yet clearly expressed. And he doesn't know which element will provide nuclei that can be easily split. This chapter describes his quest and that of his contemporaries, to identify this missing element--which ultimately unleashed nuclear energy into the world. In addition, this compelling chapter clearly illustrates the nature of science and science as a human endeavor as recommended in the National Science Education Standards.

Hakim, Joy

2007-08-17

62

Dynamical Aspects of Nuclear Fission  

NASA Astrophysics Data System (ADS)

Fission dynamics. Dependence of scission-neutron yield on light-fragment mass for [symbol]=1/2 [et al.]. Dynamics of capture quasifission and fusion-fission competition / L. Stuttgé ... [et al.] -- Fission-fission. The processes of fusion-fission and quasi-fission of superheavy nuclei / M. G. Itkis ... [et al.]. Fission and quasifission in the reactions [symbol]Ca+[symbol]Pb and [symbol]Ni+[symbol]W / G. N. Knyazheva ... [et al.]. Mass-energy characteristics of reactions [symbol]Fe+[symbol][symbol][symbol]266Hs and [symbol]Mg+[symbol]Cm[symbol][symbol]Hs at Coulomb barrier / L. Krupa ... [et al.]. Fusion of heavy ions at extreme sub-barrier energies / ?. Mi?icu and H. Esbensen. Fusion and fission dynamics of heavy nuclear system / V. Zagrebaev and W. Greiner. Time-dependent potential energy for fusion and fission processes / A. V. Karpov ... [et al.] -- Superheavy elements. Advances in the understanding of structure and production mechanisms for superheavy elements / W. Greiner and V. Zagrebaev. Fission barriers of heaviest nuclei / A. Sobiczewski ... [et al.]. Possibility of synthesizing doubly magic superheavy nuclei / Y Aritomo ... [et al.]. Synthesis of superheavy nuclei in [symbol]Ca-induced reactions / V. K. Utyonkov ... [et al.] -- Fragmentation. Production of neutron-rich nuclei in the nucleus-nucleus collisions around the Fermi energy / M. Veselský. Signals of enlarged core in [symbol]Al / Y. G. Ma ... [et al.] -- Exotic modes. New insight into the fission process from experiments with relativistic heavy-ion beams / K.-H. Schmidt ... [et al.]. New results for the intensity of bimodal fission in binary and ternary spontaneous fission of [symbol]Cf / C. Goodin ... [et al.]. Rare fission modes: study of multi-cluster decays of actinide nuclei / D. V. Kamanin ... [et al.]. Energy distribution of ternary [symbol]-particles in [symbol]Cf(sf) / M. Mutterer ... [et al.]. Preliminary results of experiment aimed at searching for collinear cluster tripartition of [symbol]Pu / Y. V. Pyatkov. Comparative study of the ternary particle emission in [symbol] and [symbol]Cm(SF) / S. Vermote ... [et al.] -- Structure of fission fragments and neurton rich nuclei / manifestation of average y-ray multiplicity in the fission modes of [symbol]Cf(sf) and the proton-induced fission of [symbol]Pa, [symbol]Np, and [symbol]Am / M. Berešová ... [et al.]. Yields of correlated fragment pairs and average gamma-ray multiplicities and energies in [symbol]Pb([symbol]O, f) / A. Bogachev ... [et al.]. Recent experiments at gammasphere intended to the study of [symbol]Cf spontaneous fission / A. V. Daniel ... [et al.]. Nuclear structure studies of microsecond isomers near A =100 / J. Genevey ... [et al.]. Covariant density functional theory: isospin properties of nuclei far from stability / G. A. Lalazisis. Relativistic mean-field description of light nuclei / J. Leja and Š. Gmuca. Energy nucleon spectra from reactions at intermediate energies / O. Grudzevich ... [et al.] -- Developments in experimental techniques. Analysis, processing and visualization of multidimensional data using DaqProVis system / M. Morhá? ... [et al.].

Kliman, J.; Itkis, M. G.; Gmuca, Š.

2008-11-01

63

Spontaneous fission and nuclear dissipation  

NASA Astrophysics Data System (ADS)

We investigate the effect on the spontaneous fission lifetime of dissipative coupling of the fission degree of freedom. The Gamow factor is modified substantially if the strength of this coupling is inferred from induced fission and heavy-ion reactions. Since experimental lifetimes and those calculated without dissipation agree reasonably well, we use our result to establish an upper bound on the reduced nuclear dissipation coefficient ? at low excitation energies. This bound, ? <~3 × 1020 S-1, is consistent with ideas developed in the context of mean-field theories. On leave from Max-Planck-Institut für Kernphysik, D-6900 Heidelberg, Fed. Rep. Germany.

Dagdeviren, N. R.; Weidenmüller, H. A.

1987-03-01

64

Quaternary Geologic Map of Connecticut and Long Island Sound Basin  

USGS Publications Warehouse

The Quaternary geologic map (sheet 1) and explanatory figures and cross sections (sheet 2) portray the geologic features formed in Connecticut during the Quaternary Period, which includes the Pleistocene (glacial) and Holocene (postglacial) Epochs. The Quaternary Period has been a time of development of many details of the landscape and of all the surficial deposits. At least twice in the late Pleistocene, continental ice sheets swept across Connecticut. Their effects are of pervasive importance to the present occupants of the land. The Quaternary geologic map illustrates the geologic history and the distribution of depositional environments during the emplacement of glacial and postglacial surficial deposits and the landforms resulting from those events.

Stone, Janet Radway; Schafer, John P.; London, Elizabeth Haley; DiGiacomo-Cohen, Mary L.; Lewis, Ralph S.; Thompson, Woodrow B.

2005-01-01

65

40 CFR 721.10666 - Quaternary ammonium compounds, bis(fattyalkyl) dimethyl, salts with tannins (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Quaternary ammonium compounds, bis(fattyalkyl) dimethyl, salts... § 721.10666 Quaternary ammonium compounds, bis(fattyalkyl) dimethyl, salts...identified generically as quaternary ammonium compounds, bis(fattyalkyl) dimethyl,...

2013-07-01

66

40 CFR 721.10342 - Quaternary ammonium compounds, fatty alkyl dialkyl hydroxide (generic).  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Quaternary ammonium compounds, fatty alkyl dialkyl hydroxide (generic... § 721.10342 Quaternary ammonium compounds, fatty alkyl dialkyl hydroxide (generic...identified generically as quaternary ammonium compounds, fatty alkyl dialkyl...

2013-07-01

67

40 CFR 721.10479 - Quaternary ammonium compounds, tris(hydrogenated tallow alkyl)methyl, chlorides.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Quaternary ammonium compounds, tris(hydrogenated tallow alkyl... § 721.10479 Quaternary ammonium compounds, tris(hydrogenated tallow alkyl...substance identified as quaternary ammonium compounds, tris(hydrogenated tallow...

2013-07-01

68

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

Code of Federal Regulations, 2011 CFR

...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...

2011-07-01

69

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

Code of Federal Regulations, 2010 CFR

...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...

2010-07-01

70

Neutron Emission in Fission and Quasi-Fission  

NASA Astrophysics Data System (ADS)

The work presents the results of the study of characteristics of the neutron emission in fission and quasi-fission of heavy and super-heavy nuclei, produced in the reactions with heavy ions. These experiments have been performed at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR), tandem accelerator in Legnaro (LNL) and VIVITRON accelerator in Strasbourg (IReS) with the use of the time-of-flight spectrometer of fission fragments CORSET and neutron multidetector DEMON. Mass-energy distributions (MED) of the 48Ca + 168Er, 208Pb, 238U and 18O + 208Pb reactions products at energies close to and below the Coulomb barrier have been studied. The pre- and post-fission neutron multiplicities as a function of the fragment mass have been obtained. A significant yield of the asymmetric component observed in the fragment mass distributions in the case of 18O + 208Pb reaction denotes the multimodal nature of the fission process. At the same time an increase in the yield of fragment masses ML ? 75-85 and MH ? 200-210 in the case 48Ca+208Pb, 238U reactions and ML ? 75-85 and MH ? 130-140 in the case 48Ca+168Er is rather connected with a quasi-fission process. The obtained neutron multiplicities dependences on fragment masses showed the validity of these assumptions.

Itkis, I.; Bogatchev, A. A.; Chizhov, A. Yu.; Itkis, M. G.; Kliman, J.; Knyazheva, G. N.; Kondratiev, N. A.; Kozulin, E. M.; Korzyukov, I. V.; Krupa, L.; Oganessian, Yu. Ts.; Pokrovski, I. V.; Prokhorova, E. V.; Sagaidak, R. N.; Voskressenski, V. M.; Rusanov, A. Ya.; Corradi, L.; Stefanini, A. M.; Trotta, M.; Beghini, S.; Montagnoli, G.; Scarlassara, F.; Chubarian, G.; Hanappe, F.; Materna, T.; Dorvaux, O.; Rowley, N.; Stuttge, L.; Giardina, G.

2005-09-01

71

Fission fragment angular momentum in ODD-Z fissioning systems  

NASA Astrophysics Data System (ADS)

Independent isomeric yield ratios of 128Sb, 130Sb, 132, 131Te, 133Te, 132I, 134I, 136I, 135Xe and 138Cs have been determined in the fast neutron induced fission of 237Np and 241Am using radiochemical and gamma spectrometric technique. From the independent isomeric yield ratios, fragment angular momenta (Jrms) have been deduced using spin-dependent statistical model analysis. Comparison of these data with the literature data for even-Z fissioning systems shows the following important features: (i) Angular momenta for fragments with spherical 82n shell and even-Z products are lower compared to the fragments with out the 82n shell and odd-Z products indicating the effect of nuclear structure. (ii) Angular momentum of even-Z products in all the fissioning systems are comparable where as for odd-Z products it is slightly higher in the odd-Z fissioning systems than in the adjacent even-Z fissioning systems. This indicates the role of single particle on fragment angular momentum in odd-Z fissioning systems.

Naik, H.; Dange, S. P.; Singh, R. J.

72

Background radiation from fission pulses  

SciTech Connect

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.

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

1988-05-01

73

Fission of rotating fermium isotopes  

NASA Astrophysics Data System (ADS)

In this paper we discuss the process of fission of even fermium isotopes, on the basis of their rotational states. The nuclear intrinsic vorticity and its coupling to the global rotation of the nucleus are used to simulate the interaction between the rotational motion and the pairing field, and lead to pairing quenching in the case of higher angular momentum states. The rotation leads to a decreasing of the fission barrier heights. The ingredients of the model—ground state fission barriers, pairing correlation energies and the cranking moments of inertia—are obtained within the self-consistent Hartree–Fock–Bogoliubov framework using the Skyrme \\text{Sk}{{\\text{M}}^{*}} energy density functional. Fission barriers and half-lives are estimated for spins I up to I = 16?.

Baran, A.; Staszczak, A.

2014-05-01

74

Cranking mass parameters for fission  

Microsoft Academic Search

A formalism for semi-adiabatic cranking mass parameters is presented. For the fission process of 234U, the time-dependent pairing equations of motion are used to calculate the excitation energy and to extract values of the cranking inertia. A fission barrier is determined by minimizing the action trajectory in a five-dimensional configuration space spanned by elongation, necking, deformations of fragments and mass

M. Mirea; R. C. Bobulescu

2010-01-01

75

Dissipation effects in cluster fission.  

PubMed

The fission of Sr(2+)(n) is studied from time-of-flight (TOF) measurements. The TOF acts both as a mass spectrometer and as a velocity dispersion analyzer. Evidence of the postfission ejection of a fast neutral atom is shown. It is explained assuming a strong deformation of the fissioning system at the transition state. The relaxation of the deformation energy into vibrations promotes the evaporation of the large fragment. PMID:14995772

Bréchignac, C; Cahuzac, Ph; Concina, B; Leygnier, J

2004-02-27

76

Characterization of Quaternary and suspected Quaternary faults, regional studies, Nevada and California  

Microsoft Academic Search

This report presents the results of geologic studies that help define the Quaternary history of selected faults in the region around Yucca Mountain, Nevada. These results are relevant to the seismic-design basis of a potential nuclear waste repository at Yucca Mountain. The relevancy is based, in part, on a need for additional geologic data that became apparent in ongoing studies

R. E. Anderson; R. C. Bucknam; A. J. Crone; K. M. Haller; M. N. Machette; S. F. Personius; T. P. Barnhard; M. J. Cecil; R. L. Dart

1995-01-01

77

Quaternary and pre-Quaternary( ) materials and processes of southeast Ohio: Overview, speculations, and recommendations  

Microsoft Academic Search

Investigations and mapping of surficial deposits in Ohio have focused largely on the glacial deposits which cover nearly two-thirds of the state. Research on Quaternary deposits beyond the glacial border has been done by Foster, Hildreth, Andrews, Leverett, Tight, Stout, Goldthwait, Forsyth, Lessig, White, Totten, Hoyer, and Noltimier. However, growing human interaction with surficial materials of southeast Ohio now requires

1992-01-01

78

Late Quaternary history of southern Chesapeake Bay  

SciTech Connect

More than 700 km of high-resolution, seismic-reflection profiles and sidescan-sonar images provide new information about the late Quaternary history of southern Chesapeake Bay. Sidescan-sonar images show that, excluding the nearshore zone, most of the bay bottom has a monotonously smooth surface, except that sand waves, ripples, and other bedforms occur in local areas affected by tidal currents. Seismic-reflection data show that the Quaternary stratigraphy of the southern part of the Bay is related primarily to the last cycle of sea-level change. The Quaternary section overlies an erosion surface cut deeply into gently seaward-dipping marine beds of Neogene age. Fluvial paleochannels, related to the last major low sea-level stand, are characterized by as much as 55 m of incision and by thin, irregular, terrace and channel-bottom deposits. Marine and estuarine deposits related to the Holocene transgression partially or fully bury the fluvial valleys and overlie the interfluves. A prominent feature of the Bay-mouth area is a wedge of sediment that has prograded into the Bay from the inner shelf. The common assumption--that the Chesapeake Bay is the drowned valley of the Pleistocene Susquehanna River--is only partially valid for the southern part of the Bay. The Bay mouth area, in general, is relatively young. The axial channel of the Bay is a modern tidal channel that is actively eroding Tertiary deposits and migrating toward the south and west; it is unrelated to older fluvial channels. Also, the positions of the modern axial channel and the last two fluvial paleochannels indicate long-term southward migration of the Bay mouth.

Colman, S.M.; Hobbs, C.H. III; Halka, J.P.

1985-01-01

79

Towards a quaternary time scale*1  

NASA Astrophysics Data System (ADS)

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.

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

80

Quaternary isoquinoline alkaloids from Xylopia parviflora.  

PubMed

From the quaternary alkaloidal fraction of the bark and the root of Xylopia parviflora (Annonaceae), four isoquinoline alkaloids, xylopinidine, dehydrocoreximine, N, N-dimethylanomurine and N-methylphoebine were isolated along with the known compounds, pycnarrhine, lotusine, 6,7-dimethoxy-2-methyl-isoquinolinium salt, 1,2-dehydroreticuline, (-)-phellodendrine, (+)-tembetarine, (-)-litcubine, (+)-magnoflorine, tetradehydroreticuline, (-)-oblongine, (+)-menisperine, (+)-N-methylcorydine, stepharanine, (+)-xanthoplanine, dehydrodiscretine, jatrorrhizine and palmatine. 3,4-Dihydro-6,7-dimethoxy-2-methyl-isoquinolinium and N-methylpurpuerine were isolated as natural products for the first time. Their structures were determined on the basis of spectroscopic evidence. PMID:15081299

Nishiyama, Yumi; Moriyasu, Masataka; Ichimaru, Momoyo; Iwasa, Kinuko; Kato, Atsushi; Mathenge, Simon G; Chalo Mutiso, Patrick B; Juma, Francis D

2004-04-01

81

Prediction of Refractive Index of Quaternary Liquid Mixtures  

Microsoft Academic Search

Refractive index data for three quaternary liquid mixtures have been analysed after extending the mixing rules for index of refraction available in literature. Relative merits and interrelations of various important mixing rules for these quaternary liquid mixtures have been discussed in detail. Surprisingly the extended equations yield fairly good agreement between theoretical and experimental values of refractive indices.

J. D. Pandey; A. K. Shukla; R. K. Shukla; R. D. Rai

1988-01-01

82

The first enzymatic resolution of quaternary ?-acetoxy ?-substituted cyclic ketones  

Microsoft Academic Search

The enantioselective resolution of quaternary ?-acetoxy ?-substituted indanone and 1-tetralone derivatives was performed with commercially available enzyme CRL in pH=8.0 phosphate buffer. Various parameters that would affect the enantoselectivities were tested, and the optimal enzymatic resolution condition was found to afford the enantiomerically enriched quaternary acetoxylated substrates with high ees (varied between 81% and 85%).

Cihangir Tanyeli; ?dris M. Akhmedov; Çi?dem ?yigün

2006-01-01

83

Assessment of fissionable material behaviour in fission chambers  

NASA Astrophysics Data System (ADS)

A comprehensive study is performed in order to assess the pertinence of fission chambers coated with different fissile materials for high neutron flux detection. Three neutron scenarios are proposed to study the fast component of a high neutron flux: (i) high neutron flux with a significant thermal contribution such as BR2, (ii) DEMO magnetic fusion reactor, and (iii) IFMIF high flux test module. In this study, the inventory code ACAB is used to analyze the following questions: (i) impact of different deposits in fission chambers; (ii) effect of the irradiation time/burn-up on the concentration; (iii) impact of activation cross-section uncertainties on the composition of the deposit for all the range of burn-up/irradiation neutron fluences of interest. The complete set of nuclear data (decay, fission yield, activation cross-sections, and uncertainties) provided in the EAF2007 data library are used for this evaluation.

Cabellos, O.; Fernández, P.; Rapisarda, D.; García-Herranz, N.

2010-06-01

84

Cranking mass parameters for fission  

NASA Astrophysics Data System (ADS)

A formalism for semi-adiabatic cranking mass parameters is presented. For the fission process of 234U, the time-dependent pairing equations of motion are used to calculate the excitation energy and to extract values of the cranking inertia. A fission barrier is determined by minimizing the action trajectory in a five-dimensional configuration space spanned by elongation, necking, deformations of fragments and mass asymmetry. The deformation energy is computed in the frame of the microscopic-macroscopic model. The two-center shell model with Woods-Saxon potentials is used in this context. Values of the inertia for excited fissioning systems are reported. A dependence between the cranking mass parameters and the intrinsic excitation energy is evidenced.

Mirea, M.; Bobulescu, R. C.

2010-05-01

85

Fission Matrix Capability for MCNP Monte Carlo  

NASA Astrophysics Data System (ADS)

We describe recent experience and results from implementing a fission matrix capability into the MCNP Monte Carlo code. The fission matrix can be used to provide estimates of the fundamental mode fission distribution, the dominance ratio, the eigenvalue spectrum, and higher mode forward and adjoint eigenfunctions of the fission neutron source distribution. It can also be used to accelerate the convergence of the power method iterations and to provide basis functions for higher-order perturbation theory. The higher-mode fission sources can be used in MCNP to determine higher-mode forward fluxes and tallies, and work is underway to provide higher-mode adjoint-weighted fluxes and tallies. 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. The new fission matrix capabilities provide a significant advance in the state-of-the-art for Monte Carlo criticality calculations.

Brown, Forrest; Carney, Sean; Kiedrowski, Brian; Martin, William

2014-06-01

86

Estimation of temperature effects on fission barriers  

NASA Astrophysics Data System (ADS)

An accurate mass formula at finite temperature has been used to obtain a more precise estimation of temperature effects on fission barriers calculated within the liquid drop model. NUCLEAR REACTIONS, FISSION Finite temperature effects.

Pi, M.; Viñas, X.; Barranco, M.

1982-08-01

87

Computer program FPIP-REV calculates fission product inventory for U-235 fission  

NASA Technical Reports Server (NTRS)

Computer program calculates fission product inventories and source strengths associated with the operation of U-235 fueled nuclear power reactor. It utilizes a fission-product nuclide library of 254 nuclides, and calculates the time dependent behavior of the fission product nuclides formed by fissioning of U-235.

Brown, W. S.; Call, D. W.

1967-01-01

88

Quaternary coral reef refugia preserved fish diversity.  

PubMed

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

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

89

Antifungal activity of gemini quaternary ammonium salts.  

PubMed

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

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

2013-12-14

90

Biosedimentology of Quaternary stromatolites in intertropical Africa  

NASA Astrophysics Data System (ADS)

Mineralizations of microbial origin constitute a non-negligeable part of Quaternary limestones in intertropical Africa. Stromatolites have colonized a wide range of environments corresponding to different hydroclimatic situations: travertines in fluviatile environments, oncolites in flood plains, encrustations in sebkha areas and shorelines of deep, fresh water lakes. The developed morphologies represent a complete catalogue of the microbial carbonated mineralizations: oncolites, chemneys, pool-rim dams, biocherms, planar or cylindrical encrustations. The building organisms may be either pure bacterial colonies (hydrothermal and lacustrine environments), cyanophyte associations (fluviatile and lacustrine environments) or complex microbial biocoenoses. Stromatolites have recorded the hydrologic, climatic and sedimentologic evolution of the continental environment in intertropical Africa for the past 240 000 years.

Casanova, J.

91

Induced-Fission Imaging of Nuclear Material  

Microsoft Academic Search

This paper presents initial results from development of the induced-fission imaging technique, which can be used for the purpose of measuring or verifying the distribution of fissionable material in an unopened container. The technique is based on stimulating fissions in nuclear material with 14 MeV neutrons from an associated-particle deuterium-tritium (D-T) generator and counting the subsequent induced fast fission neutrons

Paul Hausladen; Matthew A Blackston; James Allen Mullens; Seth M McConchie; John T Mihalczo; Philip R Bingham; Milton Nance Ericson; Lorenzo Fabris

2010-01-01

92

Late Quaternary temperature change velocity in Mesoamerica  

NASA Astrophysics Data System (ADS)

Quaternary climate has been highly variable, and yet few quantitative continental reconstructions are available for tropical areas. Quantitative records of temperature change during the Quaternary are especially relevant for putting modern climate change into a historic context. Within this perspective, two aspects are of singular relevance: i) Identifying and quantifying past climatic variability, and ii) Providing a means to estimate the seed at which climate change happened in the past. Here we show temperature reconstructions and temperature change velocity calculations for two locations in northern tropical America. Temperature reconstruction was based on two sedimentary records form Lake Chalco (30,000 years), central Mexican highlands, and Lake Petén-Itzá, Guatemalan lowlands (86,000 years). Temperature reconstruction was based on the analysis of fossil pollen on the light of pollen-temperature transfer functions. These functions were calibrated through an extensive survey of modern pollen samples covering an elevational gradient from 0 to 4,218 m asl. Derived temperature profiles show a parallel long-term trend and a similar cooling of approximately 5 oC during the Last Glacial Maximum in the lowlands and highlands of Mexico and Guatemala. Using a digital elevation model, we ere able to reconstruct the velocity at which isotherms displaced to produce the observed temperature anomalies. Spatial velocities of temperature change in the studied areas were at least four times slower than values reported for the last 50 years, but also at least twice as fast as those obtained from recent models. This study demonstrates that modern temperature change has no precedent within the last 86,000 years, but also that tropical climate has been more variable than it has been assumed to date.

Correa-Metrio, A.; Lozano, S.; Sosa-Nájera, S.; Bush, M. B.

2013-05-01

93

Summary: Our 50-year odyssey with fission  

Microsoft Academic Search

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

J. Rayford Nix

1989-01-01

94

Our 50-year odyssey with fission: Summary  

Microsoft Academic Search

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

Nix

1989-01-01

95

Space Fission Propulsion System Development Status  

Microsoft Academic Search

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

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

96

Analysis of Lead Isotope Emissive Fission.  

National Technical Information Service (NTIS)

From the experimental excitation functions of the fission of lead isotopes with A=199-204 we have obtained cross sections of the preemissive fission and the fission of the daughter nuclei produced during the evaporation cascade process. The values of expe...

S. D. Beizin M. G. Itkis Y. A. Muzychka V. N. Okolovich B. I. Pustyl'nik

1980-01-01

97

Search for ?-delayed fission of Ac228  

NASA Astrophysics Data System (ADS)

Radium was radiochemically separated from natural thorium. Thin Ra228??-Ac228 sources were prepared and exposed to mica fission track detectors, and measured by an HPGe ?-ray detector. The ?-delayed fission events of Ac228 were observed and its ?-delayed fission probability was found to be (5±2)×10-12.

Yanbing, Xu; Shengdong, Zhang; Huajie, Ding; Shuanggui, Yuan; Weifan, Yang; Yanning, Niu; Xiting, Lu; Yingjun, Li; Yonghou, Xiao

2006-10-01

98

Space Fission System Test Effectiveness  

SciTech Connect

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.

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

99

Etching fission tracks in zircons  

USGS Publications Warehouse

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.

Naeser, C. W.

1969-01-01

100

The Oklo Fossil Fission Reactors  

NSDL National Science Digital Library

This web page gives an overview of the Oklo Fossil Fission Reactors, including the history of the area where the reactor is located, the science behind the nuclear reactions, and reasons for studying this nuclear reactor. This page also includes graphics describing the Physics behind the reactors, maps, and pictures of the reactor.

Loss, Robert

2012-06-15

101

Crystalline molecular sieve synthesis using quaternary ammonium-functionalized organosiliconate  

US Patent & Trademark Office Database

This invention relates to a method for preparing crystalline silicates such as zeolites from a forming mixture containing quaternary ammonium-functionalized organosiliconate as a directing agent. The products prepared depend, inter alia, on reaction conditions such as temperature, crystallization time, and pH. More particularly, this invention relates to the use of a quaternary ammonium-functionalized organosiliconate in the preparation of ZSM-5, ZSM-48, ZSM-51 and the ZSM-48 composition thus prepared.

1993-03-16

102

Space Fission Propulsion System Development Status  

NASA Technical Reports Server (NTRS)

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 spare or planetary surface missions. In addition, the fuel for fission systems (enriched uranium) is virtually non-radioactive. The primary safety issue with fission systems is avoiding inadvertent system start - addressing this issue through proper system design is straightforward. Despite the relative simplicity and tremendous potential of space fission systems, the development and utilization of these systems has proven elusive. The first use of fission technology in space occurred 3 April 1965 with the US launch of the SNAP-10A reactor. There have been no additional US uses of space fission system. While space fission system were used extensively by the former Soviet Union, their application was limited to earth-orbital missions. Early space fission systems must be safely and affordably utilized if Ae are to reap the benefits of advanced space fission systems.

Houts, Mike; VanDyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Williams, Eric; Harper, Roger; Salvail, Pat; Hrbud, Ivana; Rodgers, Stephen L. (Technical Monitor)

2001-01-01

103

Sorption and desorption of quaternary amine cations on clays  

SciTech Connect

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.

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

104

A Quaternary Geomagnetic Instability Time Scale  

NASA Astrophysics Data System (ADS)

Reversals and excursions of Earth's geomagnetic field create marker horizons that are readily detected in sedimentary and volcanic rocks worldwide. An accurate and precise chronology of these geomagnetic field instabilities is fundamental to understanding several aspects of Quaternary climate, dynamo processes, and surface processes. For example, stratigraphic correlation between marine sediment and polar ice records of climate change across the cryospheres benefits from a highly resolved record of reversals and excursions. The temporal patterns of dynamo behavior may reflect physical interactions between the molten outer core and the solid inner core or lowermost mantle. These interactions may control reversal frequency and shape the weak magnetic fields that arise during successive dynamo instabilities. Moreover, weakening of the axial dipole during reversals and excursions enhances the production of cosmogenic isotopes that are used in sediment and ice core stratigraphy and surface exposure dating. The Geomagnetic Instability Time Scale (GITS) is based on the direct dating of transitional polarity states recorded by lava flows using the 40Ar/39Ar method, in parallel with astrochronologic age models of marine sediments in which O isotope and magnetic records have been obtained. A review of data from Quaternary lava flows and sediments yields a GITS comprising 10 polarity reversals and 27 excursions during the past 2.6 million years. Nine of the ten reversals bounding chrons and subchrons are associated with 40Ar/39Ar ages of transitionally-magnetized lava flows. The tenth, the Guass-Matuyama chron boundary, is tightly bracketed by 40Ar/39Ar dated ash deposits. Of the 27 well-documented excursions, 14 occurred during the Matuyama chron and 13 during the Brunhes chron; 19 have been dated directly using the 40Ar/39Ar method on transitionally-magnetized volcanic rocks and form the backbone of the GITS. Excursions are clearly not the rare phenomena once thought. Rather, during the Quaternary period, they occur nearly three times as often as full polarity reversals. I will address analytical issues, including the size and consistency of system blanks, that have led to the recognition of minor (1%) discrepencies between the 40Ar/39Ar age for a particular reversal or excursion and the best astrochronologic estimates from ODP sediment cores. For example, re-analysis of lava flows from Haleakala volcano, Maui that record in detail the Matuyama-Brunhes polarity reversal have been undertaken with blanks an order of magntitude smaller and more stable than was common a decade ago. Using the modern astrochronologic calibration of 28.201 Ma for the age of the Fish Canyon sanidine standard, results thus far yield an 40Ar/39Ar age of 772 × 11 ka for the reversal that is identical to the most precise and accurate astrochronologic age of 773 × 2 ka for this reversal from ODP cores. Similarly, new dating of sanidine in the Cerro Santa Rosa I rhyolite dome, New Mexico reveals an age of 932 × 5 ka for the excursion it records, in perfect agreement with astrochronologically dated ODP core records. Work underway aims at refining the 40Ar/39Ar ages that underpin the entire GITS by further eliminating the bias between the radioisotopic and astrochronologically determined ages for several reversals and excursions.

Singer, B. S.

2013-12-01

105

Space Fission Propulsion System Development Status  

NASA Astrophysics Data System (ADS)

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 for fission systems (enriched uranium) is virtually non-radioactive. The primary safety issue with fission systems is avoiding inadvertent system start. Addressing this issue through proper system design is straight-forward. Despite the relative simplicity and tremendous potential of space fission systems, the development and utilization of these systems has proven elusive. The first use of fission technology in space occurred 3 April 1965 with the US launch of the SNAP-10A reactor. There have been no additional US uses of space fission systems. While space fission systems were used extensively by the former Soviet Union, their application was limited to earth-orbital missions. Early space fission systems must be safely and affordably utilized if we are to reap the benefits of advanced space fission systems. NASA's Marshall Space Flight Center, working with Los Alamos National Laboratory (LANL), Sandia National Laboratories, and others, has conducted preliminary research related to a Safe Affordable Fission Engine (SAFE). An unfueled core has been fabricated by LANL, and resistance heaters used to verify predicted core thermal performance by closely mimicking heat from fission. The core is designed to use only established nuclear technology and be highly testable. In FY01 an energy conversion system and thruster will be coupled to the core, resulting in an 'end-to-end' nuclear electric propulsion demonstrator being tested using resistance heaters to closely mimic heat from fission. Results of the SAFE test program will be presented. The applicability of a SAFE-powered electric propulsion system to outer planet science missions will also be discussed.

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

2001-01-01

106

Fission fragment angular momentum in ODD-Z fissioning systems  

Microsoft Academic Search

:   Independent isomeric yield ratios of 128Sb, 130Sb, 132, 131Te, 133Te, 132I, 134I, 136I, 135Xe and 138Cs have been determined in the fast neutron induced fission of 237Np and 241Am using radiochemical and gamma spectrometric technique. From the independent isomeric yield ratios, fragment angular momenta\\u000a (Jrms) have been deduced using spin-dependent statistical model analysis. Comparison of these data with the

H. Naik; S. P. Dange; R. J. Singh

2000-01-01

107

Clinker deposits, Powder River Basin, Wyoming and Montana: A new source of high-fidelity paleomagnetic data for the Quaternary  

NASA Astrophysics Data System (ADS)

Clinker, rock baked and fused by in situ burning of underlying coal, posesses a thermoremanent and/or thermochemical magnetization that resides in magnetite, hematite, and goethite. Data from individual sites imply that clinker may provide a high resolution recording of the geomagnetic field (e.g., within-site virtual geomagnetic pole angular standard deviations are usually less than 10°) , but this is dependent on its thermal history and the time over which magnetic phases formed. Data from 17 sites in the Powder River Basin (13 normal polarity, 4 reverse) yield a mean of Decl. = 348°, Incl. = 62°, ?95 = 5°, k = 42 and a corresponding pole position of 81° lat., 158° long. with a virtual geomagnetic pole angular standard deviation of 17.3°. The mechanism of clinker formation, the wide geographic distribution, and the range of available fission-track ages suggest that clinker may contain a nearly complete geomagnetic field record for much of the Quaternary.

Jones, Alison H.; Geissman, John W.; Coates, Donald A.

1984-12-01

108

DSP Algorithms for Fission Fragment and Prompt Fission Neutron Spectroscopy  

NASA Astrophysics Data System (ADS)

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 252Cf(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 252Cf(SF) reaction with data available from literature.

Zeynalova, O.; Zeynalov, Sh.; Hambsch, F.-J.; Oberstedt, S.; Fabry, I.

2009-10-01

109

Quaternary phylogeography: the roots of hybrid zones.  

PubMed

The older history of hybrid zones is explored through consideration of recent advances in climatology, paleontology and phylogeography in the Late Cenozoic, particularly the Quaternary Period with its major climatic cycles. The fossil record shows that these ice ages and their nested millennial oscillations caused substantial changes in species distributions and with genetic evidence allows deduction of refugia and colonization routes in arctic, temperate, desert and tropical regions. The age of divergence between hybridizing lineages varies from the Late Pleistocene to the Late Miocene, implying much range change and varying selection on sister lineages. Hybridizing lineages in the Tropical and Temperate regions range in age from young to old, but those studied in the Arctic are no more than a few ice ages old and their refugial roots are not clear. Mid to low latitude regions often show parapatric patchworks of lineages and multiple refugia stable through many climatic oscillations. Particular hybrid zones may have formed more than once; while some expansions were not the same, producing reticulation and introgression in previous glacial cycles. Hybrid-zone roots are complex and deep, and considerations of their complexity can reveal evolutionary pathways of species. They are indeed windows on evolution. PMID:21234647

Hewitt, Godfrey M

2011-05-01

110

Ototoxic effect of quaternary ammonium compounds.  

PubMed

In earlier investigations by the author it has been shown that chlorhexidine, when introduced into the middle ear of guinea pigs, caused serious damage to the inner ear. The present investigation was performed in order to study if the quaternary ammonium compounds benzethonium chloride and benzalkonium chloride, frequently used for skin disinfection, can also induce inner ear damage when introduced into the tympanic cavity of guinea pigs. The disinfectants in question, at a concentration of 0.1% and in a solution of aqua dest. or 70% alcohol, were introduced into the animals' middle ear for exposure times of 10, 30, or 60 min. The animals were sacrificed 2 or 9 weeks after the exposure and the organ of Corti and vestibular neuroepithelia were studied as surface preparations with phase contrast microscopy. It was found that most of the ears exposed to the disinfectants had suffered damage, affecting both the vestibular and cochlear parts of the inner ear. The extent of the damage was related both to the duration of exposure and to the length of the animals' survival after the exposure. Furthermore it was found that the tympanic cavity and the perilymphatic spaces of vestibulum and cochlea were pathologically changed. PMID:6125078

Aursnes, J

1982-01-01

111

Surface modification of sepiolite with quaternary amines.  

PubMed

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 capacity of sepiolite. The Mg(2+) ions released during the exchange process were higher than the CEC value of sepiolite because of the simultaneous dissolution of the present minerals. The water adsorption decreased with the increasing surfactant loading up to 250 mmol/kg of sepiolite, which can be ascribed to an intensification of the hydrophobic properties. With loadings above 250 mmol/kg, the water adsorption increases. Simple kinetic analysis of SDBAC adsorption was performed. The properties and the type of bonding between the surfactants and sepiolite were investigated by DT, TG, and DTG analysis. During the gradual heating in oxidizing atmosphere, the adsorbed organic material is oxidized giving rise to significant exothermic peaks. The exothermic peak temperatures in the range 200-500 degrees C depended on the surfactant loadings and provided evidence of the formation of multilayers on the sepiolite surface. PMID:16045916

Lemi?, Jovan; Tomasevi?-Canovi?, Magdalena; Djurici?, Mirjana; Stani?, Tanja

2005-12-01

112

Quaternary glaciations of the southern Andes  

NASA Astrophysics Data System (ADS)

The southern Andes comprise the southernmost portion of the Andean Cordillera, beginning at the edge of the Puna Altiplano (lat.27°S) and ending at Isla de los Estados (lat.55°S). The late Cainozoic glacial record of these mountains spans the interval from the Late Miocene to the present and is one of the most complete to be found anywhere in the world. This has arisen for several reasons: (i) the conterminous mountain ice cap extended to the piedmont zone on both flanks of the range, where the sedimentary and morphological record has been well preserved; (ii) periodic volcanism, mainly from monogenetic fissure eruptions of basalt east of the range and from central tephra-producing cones along the mountain crest, has provided opportunity for the preservation and radiometric dating of interbedded glacial deposits; (iii) a tectonically-induced interval of stream incision in the Mid Pleistocene and simultaneous uplift has preserved glacial sediments on interfluves; (iv) in the Chilean lakes region west of the mountains, Late Quaternary glaciers terminated in a well-vegetated landscape, thus creating scope for radiocarbon dating of interbedded and incorporated organic materials; consequently, the last glaciation in the Llanquihue area of Chile is one of the best dated sequences in South America; thus the 'Llanquihue' Glaciation is proposed as the South American equivalent of the 'Wisconsin' and 'Weichsel' glaciations of North America and north west Europe respectively.

Rabassa, Jorge; Clapperton, Chalmers M.

113

Fission Track Dating of Tanzanite  

Microsoft Academic Search

Seven crystals of tanzanite from the Ally and D'Souza Mines, Tanzaniao gave an average fission track age of 585 + 28 m.y. Tanzanite, a gem variety of zoisite, has annealing characteristics that are very similar to epidote; both require a temperature above 725oC for complete track annealing in an hour. Sub-gem-quality tanzanite, from a new occrurence ztoO km to the

M. Saul

114

Fission of Rapidly Rotating Protostars  

NASA Astrophysics Data System (ADS)

It has long been conjectured that close binary star systems might form through the fission of a rapidly rotating and contracting protostar (for a review see Durisen & Tohline 1985). Protostars that are axisymmetric beyond the point of dynamic bar-like mode instability do not fission (Imamura et al. 2000), but contracting non-axisymmetric protostars might encounter bifurcations of surface shape leading to fission. In addition, they may be susceptible to hydrodynamic instabilities, first described by Lebovitz & Lifschitz (1996), whose nonlinear effects are still unknown. We will present a series of hydrodynamic simulations of rapidly rotating polytropic protostars to investigate fission in contracting protostars. The initial model is an equilibrium configuration with T/|W| ? 0.14, where T is the rotational kinetic energy and W is the total gravitational energy. It is given a bar-like cos(2?) density perturbation with an amplitude of .02, .10 or .25. These perturbed polytropes are then cooled by reducing the polytropic constant K where P = K?1+1/n. Here P is the pressure, ? is the density and n is the polytropic index, here chosen to be 3/2. As the polytrope contracts, we find no strong signal of a growing instability. All simulations evolve through to the dynamic bar-like mode instability point at T/|W|? 0.27 and produce a ring around a bar, not a binary. However, there is some indication of amplitude growth at a T/|W|?0.22. We are investigating this growth further with follow-up simulations that start at an equilibrium model with a T/|W| ? 0.22. This enables us to study growth in this regime with higher resolution and slower contraction rates. This work has been supported by the National Science Foundation through grant AST-0452975 (astronomy REU program to Indiana University).

Lozier, Jennifer L.; Michael, S.; Durisen, R. H.; Imamura, J. N.

2006-12-01

115

Technical Application of Nuclear Fission  

NASA Astrophysics Data System (ADS)

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.

Denschlag, J. O.

116

MODELING AND FISSION CROSS SECTIONS FOR AMERICIUM.  

SciTech Connect

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.

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

2005-05-01

117

Landau-Zener effect in fission  

Microsoft Academic Search

A model that takes into account the Landau-Zener promotion mechanism during fission was developed recently. The structures observed in the subthreshold neutron-induced fission of Th232 are investigated employing this model. Theoretical single-particle excitations of a phenomenological two-humped barrier are determined by solving a system of coupled differential equations for the motion along the optimal fission path. A rather good agreement

M. Mirea; L. Tassan-Got; C. Stephan; C. O. Bacri; R. C. Bobulescu

2007-01-01

118

Calculated fission properties of the heaviest elements  

Microsoft Academic Search

Experimental results on the fission properties of nuclei close to 264Fm show sudden and large changes with a change of only one or two neutrons or protons. The nucleus 258Fm, for instance, undergoes symmetric fission with a half-life of about 0.4ms and a kinetic-energy distribution peaked at about 235 MeV whereas 256Fm undergoes asymmetric fission with a half-life of about

P. Möller; J. R. Nix; W. J. Swiatecki

1987-01-01

119

Fission barriers and half-lives  

SciTech Connect

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.

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

1989-01-01

120

Bacterial adhesion inhibition of the quaternary ammonium functionalized silica nanoparticles.  

PubMed

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 was coated with the surface modified silica nanoparticles presented bacterial growth inhibition activity. For comparison of bacterial growth resistance, hydrophobic silane (alkyl functionalized silane) modified silica nanoparticles and pristine silica nanoparticles were prepared. As a result of bacterial adhesion test, the quaternary ammonium functionalized silica nanoparticles exhibited the enhanced inhibition performance against growth of Gram-negative Escherichia coli (96.6%), Gram-positive Staphylococcus aureus (98.5%) and Deinococcus geothermalis (99.6%) compared to pristine silica nanoparticles. These bacteria resistances also were stronger than that of hydrophobically modified silica nanoparticles. It could be explained that the improved bacteria inhibition performance originated from the synergistic effect of hydrophobicity and antibacterial property of quaternary ammonium silane. Additionally, the antimicrobial efficacy of the fabricated nanoparticles increased with decreasing size of the nanoparticles. PMID:21115282

Song, Jooyoung; Kong, Hyeyoung; Jang, Jyongsik

2011-02-01

121

Determining the Fission Yield Distribution for the Reactor Neutron Induced Fission of exp 241 AM.  

National Technical Information Service (NTIS)

For the reactor neutron induced fission of exp 241 Am the fission yields for a total of 35 masses were determined as against exp 235 U fission yields and compared with available data. The shape of the mass distribution curve was well defined by the measur...

W. Weinlaender H. J. Born

1972-01-01

122

Ternary and quaternary antimonide devices for thermophotovoltaic applications  

SciTech Connect

Thermophotovoltaic (TPV) devices have been fabricated using epitaxial ternary and quaternary layers grown on GaSb substrates. GaInSb ternary devices were grown by metalorganic vapor phase epitaxy (MOVPE) with buffer layers to accommodate the lattice mismatch, and GaInAsSb lattice-matched quaternaries were grown by MOVPE and by liquid phase epitaxy (LPE). Improved devices are obtained when optical absorption occurs in the p-layer due to the longer minority carrier diffusion length. Thick emitter p/n devices are limited by surface recombination, with highest quantum efficiency and lowest dark current being achieved with epitaxially grown surface passivation layers on lattice-matched MOVPE quaternaries. Thin emitter/thick base n/p devices are very promising, but require improved shallow high-quality n-type ohmic contacts.

Hitchcock, C.W.; Gutmann, R.J.; Ehsani, H.; Bhat, I.B. [Rensselaer Polytechnic Inst., Troy, NY (United States). Center for Integrated Electronics and Electronics Manufacturing; Wang, C.A. [Massachusetts Inst. of Tech., Lexington, MA (United States). Lincoln Lab.; Freeman, M.J.; Charache, G.W. [Lockheed Martin, Inc., Schenectady, NY (United States)

1998-06-01

123

[The biological activity of quaternary ammonium salts (QASs)].  

PubMed

Quaternary ammonium salts (QASs), especially those of cationic surfactant character, are applied as antibacterial and antifungal disinfectants. QASs affect lipid-enveloped viruses, including human immunodeficiency virus (HIV) and hepatitis B virus (HBV), but not non-enveloped viruses. These compounds are extensively used in domestic (as ingredients of shampoos, hair conditioners), agricultural (as fungicides, pesticides, insecticides), healthcare (as medications), and industrial applications (as biocides, fabric softeners, corrosion inhibitors). The extensive use of quaternary ammonium disinfectants in recent years has led to the development of resistance in microorganisms to these drugs. Thus Staphylococcus aureus strains contain the plasmid-carrying genes qacA and qacB encoding resistance to quaternary ammonium compounds and acriflavine. The membrane proteins QacA and QacB confer multidrug resistance by exporting the compound by the proton motive force which is generated by the transmembrane electrochemical proton gradient. PMID:20400784

Ob?ak, Ewa; Gamian, Andrzej

2010-01-01

124

Dynamics of Rotationally Fissioned Asteroids  

NASA Astrophysics Data System (ADS)

We present a model for near-Earth asteroid (NEA) rotational fission that results in the evolution of all observed types of NEA systems: synchronous binaries, asteroid pairs, doubly synchronous binaries, high-e binaries, ternary systems, and contact binaries. The model consists of "rubble pile” asteroid geophysics, the YORP and binary YORP effects, and mutual gravitational interactions. An NEA can be modeled as a ``rubble pile"--a collection of gravitationally bound boulders with a distribution of size scales and very little tensile strength between them. The YORP effect torques a "rubble pile” asteroid until the asteroid reaches its disruption spin limit, and then two collections of boulders will enter into orbit about each other determined by the largest distance between mass centers. This binary system dynamically evolves under the effects of non-spherical gravitational potentials, solar gravitational perturbations, and mutual body tides. The coupling between the spin states and orbit state chaotically drives the system into the observed asteroid classes with mass ratio, q, distinguishing two evolutionary tracks. High mass ratio systems, q>0.2, evolve tidally into doubly synchronous binaries and then continued to be evolved by BYORP. Low mass ratio systems, q<0.2, will disrupt on a timescale of 1 yr creating asteroid pairs unless another process interdicts. Before escape the secondary will often be spun up via gravitational torques until it too may fission, creating a chaotic ternary system. We call this new process secondary fission. The resulting triple system may eject one body or, more often, send one into a slow speed impact with the primary. These processes tend to stabilize the initially chaotic binaries to create synchronous binaries. These results emphasize the importance of the initial component size distribution and configuration within the parent body. This work is supported by NASA's PGG and OPR programs through grants: NNX08AL51G and NNX09AU23G.

Jacobson, Seth A.; Scheeres, D. J.

2010-10-01

125

FISSION GAS YIELD IN URANIUM  

Microsoft Academic Search

The yield of xenon and krypton in irradiated uranium was found to vary ; with neutron flux from 4.8 cm³(STP)\\/cm³ uranium-atom percent burnup ; at 10¹² neut\\/cm²-sec to neut\\/cm²-sec as a result of neutron ; capture by the unstable isotopes Xe¹³³ and Xe¹³⁵. These results are ; applicable only to uranium irradiated in a thermal flux The fission gas yields

1962-01-01

126

Characterization of Quaternary and suspected Quaternary faults, Amargosa area, Nevada and California  

SciTech Connect

This report presents the results of geologic studies that help define the Quaternary history of selected faults in the region around Yucca Mountain, Nevada. These results are relevant to the seismic-design basis of a potential nuclear waste repository at Yucca Mountain. The relevancy is based, in part, on a need for additional geologic data that became apparent in ongoing studies by S. Pezzopane (written commun., 1995) that resulted in the identification of 51 relevant and potentially relevant (see appendix A for definitions) individual and compound faults and fault zones in the 100-km-radius region around the Yucca Mountain site. These structures were divided into local and regional categories by Pezzopane (1995); this report deals with selected regional structures. In this introduction, the authors outline the scope and strategy of the studies and the tectonic environment of the studied structures.

Anderson, R.E.; Crone, A.J.; Machette, M.N.; Bradley, L.A.; Diehl, S.F.

1995-12-31

127

GF(4) Based Synthesis of Quaternary Reversible\\/Quantum Logic Circuits  

Microsoft Academic Search

Galois field sum of products (GFSOP) has been found to be very promising for reversible\\/quantum implementation of multiple-valued logic. In this paper, we show ten quaternary Galois field expansions, using which quaternary Galois field decision diagrams (QGFDD) can be constructed. Flattening of the QGFDD generates quaternary GFSOP (QGFSOP). These QGFSOP can be implemented as cascade of quaternary 1-qudit gates and

Mozammel H. A. Khan; Marek A. Perkowski

2007-01-01

128

Ice Age Earth: Late Quaternary geology and climate  

SciTech Connect

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.

Dawson, A.G.

1992-01-01

129

40 CFR 721.8658 - Modified polymer of vinyl acetate and quaternary ammonium compound (generic).  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Modified polymer of vinyl acetate and quaternary ammonium...Chemical Substances § 721.8658 Modified polymer of vinyl acetate and quaternary ammonium...substance identified generically as modified polymer of vinyl acetate and quaternary...

2010-07-01

130

Adsorption and excess fission xenon  

NASA Astrophysics Data System (ADS)

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.

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

131

Get Close to a Nuclear Fission Reaction!  

NSDL National Science Digital Library

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.

2004-01-29

132

Fission track dating of zircon: a multichronometer.  

National Technical Information Service (NTIS)

Scattering in Fission Track ages of zircons of a single rock is possible when they present morphological and geochemical variations, if the greatest care is not taken in the choice of the etching conditions and the counting of tracks. The Fission Track st...

J. Carpena

1992-01-01

133

Fission stability diagram of sup 240 Pu  

SciTech Connect

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.

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

134

Options for Affordable Fission Surface Power Systems  

NASA Technical Reports Server (NTRS)

Fission surface power systems could provide abundant power anywhere on free surface of the moon or Mars. Locations could include permanently shaded regions on the moon and high latitudes on Mars. To be fully utilized; however, fission surface power systems must be safe, have adequate performance, and be affordable. This paper discusses options for the design and development of such systems.

Houts, Mike; Gaddis, Steve; Porter, Ron; VanDyke, Melissa; Martin Jim; Godfroy, Tom; Bragg-Sitton, Shannon; Garber, Anne; Pearson, Boise

2006-01-01

135

Fission fragment tracks in semiconducting layer structures  

Microsoft Academic Search

Fission fragment irradiation of a number of semiconducting materials establishes that permanent tracks are formed only when the conductivity is ?2 × 10 (ohm-cm). The intermittent nature of particle tracks is a characteristic of layer structures and further analysis confirms that there is one ‘defect’ per sandwich plane crossed by the fission particle. The intermittency is ascribed to the reduced

D. Vernon Morgan; L. T. Chadderton

1968-01-01

136

Fast neutron fission of 241Am  

NASA Astrophysics Data System (ADS)

For the fission of 241Am induced by fast neutrons from a 239Pu critical assembly, we have determined the mass-yield distribution and measured independent fission yields and one isomer ratio. The mass-yield distribution curve was constructed from the results for 29 total chain yields which were derived from measurements of fission products ranging from 91Y to 161Tb. Absolute fission yields were obtained with an accuracy of 4% by the requirement of unit total yield in each half of the mass-yield distribution curve and by use of the 235U(n, f) and 238U(n, f) monitor reactions. The peak-to-valley ratio is about 60. Several independent fractional chain yields were measured. Values of Zp, the most probable charge for a given mass number, inferred from these measurements are in good agreement with those estimated from independent-yield systematics. NUCLEAR REACTIONS, FISSION 241Am(n, f), E=degraded fission-spectrum distribution; measured fission yields, deduced fission mass distribution. Measured independent fractional chain yields; measured isomer ratio.

Sigg, R. A.; Kantelo, M. V.; Sisson, D. H.; Prindle, A. L.; Nethaway, D. R.

1983-01-01

137

ORNL fission product release tests VI-6.  

National Technical Information Service (NTIS)

The ORNL fission product release tests investigate release and transport of the major fission products from high-burnup fuel under LWR accident conditions. The two most recent tests (VI-4 and VI-5) were conducted in hydrogen. In three previous tests in th...

M. F. Osborne R. A. Lorenz J. L. Collins C. S. Lee

1991-01-01

138

Systematics of Fission-Product Yields  

SciTech Connect

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.

A.C. Wahl

2002-05-01

139

Application of quaternary phase diagrams to compound semiconductor processing  

SciTech Connect

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.

Sinclair, R.

1994-10-01

140

Pliocene and Quaternary geology of Mana Island (Note)  

Microsoft Academic Search

Mana Island, off the south-west coast of the North Island, is capped by the Mana Surface which dips south-east at about 2. This dip is considered to be tectonic in origin. The surface, considered to be a marine abrasion platform, has no overlying deposits except late Quaternary loesses. No continuity with mainland surfaces can be demonstrated, but correlation with the

D. N. Williams

1978-01-01

141

Double-Chain Surfactants with Two Quaternary Ammonium Head Groups.  

National Technical Information Service (NTIS)

Double-chain surfactants with two quaternary ammonium head groups were prepared: 2-(7-trimethylammo nioheptyl)-2-decyl-4-(8-trimethyla mmoniooctyl)-5-octyl-1- 3-dioxolane dibromide (3) and 2-(3- trimethylammoniopropyl) -2-tetradecyl-4-(8-trimethylammo nio...

D. A. Jaeger S. G. Russell H. Shinozaki

1994-01-01

142

Stereocontrol by quaternary centres: a stereoselective synthesis of (-)-luminacin D.  

PubMed

Very high diastereoselectivity can be achieved by 1,3-chelation-controlled allylation of aldehydes that possess a non-chelating ?-ether substituent, even if the ?-position is a quaternary centre and/or a spiro-epoxide. This reaction was used as a key step in an enantioselective synthesis of the angiogenesis inhibitor luminacin?D. PMID:24519660

Bartlett, Nathan; Gross, Leona; Péron, Florent; Asby, Daniel J; Selby, Matthew D; Tavassoli, Ali; Linclau, Bruno

2014-03-17

143

Quaternary Paleoecology and Climate Change, Bladen County, NC  

NSDL National Science Digital Library

Students analyze a Quaternary pollen diagram from lakes in Bladen County, NC. This diagram contains (from the top down) the current deglaciation, the last glacial, and the previous interglacial. Students These lakes occur in Carolina Bays and students also evaluate a proposal that meteorite impact created the Bays.

Farley, Martin

144

European quaternary refugia: a factor in large carnivore extinction?  

Microsoft Academic Search

The extinction of large carnivores in Europe during the Quaternary is reviewed and the potential role of glacial refugia in these extinctions is investigated using the VORTEX model for population viability analysis. A model was built for a medium sized big cat similar to the extinct Panthera gombaszoegensis utilising life history data from the modern jaguar Panthera onca. This approach

Hannah J. O'Regan; Alan Turner; David M. Wilkinson

2002-01-01

145

Quaternary deformation in the Eastern Pamirs, Tadzhikistan and Kyrgyzstan  

Microsoft Academic Search

Active deformation in the eastern Pamir of Central Asia is concentrated on the margins of the orogen with minor deformation within the high terrain. Along the Trans-Alai mountain front at the northern perimeter of the orogen, Quaternary thrusting is documented by uplifted pediments, now at >500 m above the piedmont, Holocene fault scarps, and large earthquakes with N to NW

M. R. Strecker; W. Frisch; M. W. Hamburger; L. Ratschbacher; S. Semiletkin; A. Zamoruyev; N. Sturchio

1995-01-01

146

Seismic stratigraphy of Late Quaternary deposits in the eastern Skagerrak  

Microsoft Academic Search

High-resolution seismic profiles from the Swedish west coast divide Quaternary deposits into six seismic sequences, containing 13 different seismic facies. Documentation of these sequences and facies and their stratigraphic and geographic variability is the first step in a basin-fill analysis to interpret depositional environments and major controlling processes. The deposits are attributed to one deglaciation cycle. The seismic sequences are:

Olof Larsson; Rodney L. Stevens

2008-01-01

147

Pliocene - Quaternary Faults and Potential Seismic Hazards in Southern Nevada  

Microsoft Academic Search

Known Quaternary faults in the Central Basin & Range Province (CBR) have a southern limit at about 35 degrees 30' N latitude, south of Las Vegas, NV. The boundary is generally aligned with the southern end of the Sierra Nevada and strike-slip faults, such as those in Death Valley, that accommodate the right-lateral motion transferred from the plate boundary to

W. J. Taylor; J. Wagoner; C. M. Depolo; B. Luke; J. Louie

2005-01-01

148

Enhanced energy transfer in quasi-quaternary nanocrystal superlattices.  

PubMed

Quasi-quaternary nanocrystal superlattices are assembled by using exclusively core-shell particles as building blocks. The assemblies show an enhancement of energy-transfer from cadmium selenide-based core-shell quantum dots to gold-iron oxide core-shell nanocrystals compared to random mixtures of the same components. PMID:24357329

Cargnello, Matteo; Diroll, Benjamin T; Gaulding, E Ashley; Murray, Christopher B

2014-04-16

149

Quaternary geology of the Channeled Scabland and adjacent areas  

Microsoft Academic Search

The quaternary history of the channeled scabland is characterized by discrete episodes of catastrophic flooding and prolonged periods of loess accumulation and soil formation. The loess sequence was correlated with Richmond's Rocky Mountain glacial chronology. At least five major catastrophic flood events occurred in the general vicinity of the channeled scabland. The earliest episode occurred prior to the extensive deposition

V. R. Baker

1978-01-01

150

Quaternary fossil fish from the Kibish Formation, Omo Valley, Ethiopia  

Microsoft Academic Search

The late Quaternary Kibish Formation of the Omo Valley, southwestern Ethiopia, preserves environments reflecting a history of fluctuations in the level of nearby Lake Turkana over the past 200,000 years. The Kibish Formation has yielded a diverse mammalian fauna (as well as birds and crocodiles), stone tools, and the oldest anatomically modern Homo sapiens. Fish, the most common vertebrate fossils

Josh Trapani

2008-01-01

151

Late Quaternary paleohydrologic and paleotemperature change in southern Nevada  

Microsoft Academic Search

Paleo-spring discharge activity in the southern Great Basin responded to changes in recharge, hence climate changes, in high mountain areas during the late Quaternary. In our study, we examined four stratigraphic sections in southern Nevada in order to reconstruct paleohydrologic change spanning the last two major discharge cycles. The largest discharge event in those sections is expressed as extensive wetland

Jay Quade; Richard M. Forester; Joseph F. Whelan

152

Quaternary history and contemporary patterns in a currently expanding species  

Microsoft Academic Search

BACKGROUND: Quaternary climatic oscillations had dramatic effects on species evolution. In northern latitudes, populations had to survive the coldest periods in refugial areas and recurrently colonized northern regions during interglacials. Such a history usually results in a loss of genetic diversity. Populations that did not experience glaciations, in contrast, probably maintained most of their ancestral genetic diversity. These characteristics dramatically

Carole Kerdelhué; Lorenzo Zane; Mauro Simonato; Paola Salvato; Jérôme Rousselet; Alain Roques; Andrea Battisti

2009-01-01

153

Quaternary glacial history of NW Garhwal, Central himalayas  

Microsoft Academic Search

A first account of the Quaternary glacial history is presented for northwest Garhwal, Central Himalaya. On the basis of sediments and landforms, one glacial stage has been recognised. This is called the Bhagirathi Glacial Stage, when extensive valley glaciers advanced down the Bhagirathi valley to Jhala, 40.5 km from the snout of Gangotri Glacier. The ELA depression during this stage

Milap Chand Sharma; Lewis A. Owen

1996-01-01

154

Landscape paleoecology and late Quaternary extinctions in the Hudson Valley  

Microsoft Academic Search

Stratigraphic palynological analyses of four late Quaternary deposits comprise a landscape-level study of the patterns and processes of megafaunal extinction in the southeastern New York region. Distinctive spores of the dung fungus Sporormiella are used as a proxy for megafaunal biomass and charcoal particle analysis as a proxy for fire history. A decline in spore values at all sites is

Guy Schuyler Robinson

2003-01-01

155

Transport phenomena in a reactive quaternary gas mixture  

Microsoft Academic Search

Quaternary gas mixtures which undergo a binary and reversible chemical reaction of the type A+B?C+D are analyzed within the framework of Boltzmann equation in order to investigate the effects caused by the reactions on the transport coefficients. The gas system is considered close to chemical equilibrium, a state in which the affinity has a small value characterizing the final stage

Adriano W. Silva; Giselle M. Alves; Gilberto M. Kremer

2007-01-01

156

Impact of Quaternary Structure Dynamics on Allosteric Drug Discovery  

PubMed Central

The morpheein model of allosteric regulation draws attention to proteins that can exist as an equilibrium of functionally distinct assemblies where: one subunit conformation assembles into one multimer; a different subunit conformation assembles into a different multimer; and the various multimers are in a dynamic equilibrium whose position can be modulated by ligands that bind to a multimer-specific ligand binding site. The case study of porphobilinogen synthase (PBGS) illustrates how such an equilibrium holds lessons for disease mechanisms, drug discovery, understanding drug side effects, and identifying proteins wherein drug discovery efforts might focus on quaternary structure dynamics. The morpheein model of allostery has been proposed as applicable for a wide assortment of disease-associated proteins (Selwood, T., Jaffe, E., (2012) Arch. Bioch. Biophys, 519:131–143). Herein we discuss quaternary structure dynamics aspects to drug discovery for the disease-associated putative morpheeins phenylalanine hydroxylase, HIV integrase, pyruvate kinase, and tumor necrosis factor ?. Also highlighted is the quaternary structure equilibrium of transthyretin and successful drug discovery efforts focused on controlling its quaternary structure dynamics.

Jaffe, Eileen K.

2013-01-01

157

Parity nonconservation in nuclear fission  

SciTech Connect

The aim of this work is to determine the size {alpha}{sub nf} of the global PNC asymmetry coefficient for the isotopes {sup 237}Np, {sup 245}Cm and {sup 249}Cf, to search for a mass- and energy dependence {alpha}{sub nf}(m{sub LF},E{sub FF}) in the case of {sup 233}U(n,f) and to test the predicted angular distribution of fragments W({theta}). Analysis of the new results together with those obtained before for six other fissile isotopes shows an evident decrease of the PNC effect when going from {sup 229}Th to {sup 249}Cf. A tentative interpretation of this tendency as a result of saddle point properties of the fission-prone nucleus is given. For the mass- and energy analysis the principle of measurement is presented and first results for the test of the angular dependence are given.

Koetzle, A.; Jesinger, P.; Goennenwein, F. [Physikalisches Institut, Auf der Morgenstelle 14, 72076 Tuebingen (Germany); Petrov, G. A.; Petrova, V. I.; Gagarski, A. M.; Krasnoschokova, I. A.; Pleva, Yu. S.; Sokolov, V. E.; Soloviev, S. M.; Vasiliev, V. Ya. [PNPI of RAS, Gatchina, Leningrad district, 188350 (Russian Federation); Danilyan, G. [ITEP, Moscow 117259 (Russian Federation); Zimmer, O.; Nesvizhevsky, V. [Institut Laue-Langevin, 38042 Grenoble (France)

1998-10-26

158

Downstream behavior of fission products  

SciTech Connect

The downstream behavior of fission products has been investigated by injecting mixtures of CsOH, CsI, and Te into a flowing steam/hydrogen stream and determining the physical and chemical changes that took place as the gaseous mixture flowed down a reaction duct on which a temperature gradient (1000/sup 0/ to 200/sup 0/C) had been imposed. Deposition on the wall of the duct occurred by vapor condensation in the higher temperature regions and by aerosol deposition in the remainder of the duct. Reactions in the gas stream between CsOH and CsI and between CsOH and Te had an effect on the vapor condensation. The aerosol was characterized by the use of impingement tabs placed in the gas stream.

Johnson, I.; Farahat, M.K.; Settle, J.L.; Johnson, C.E.; Ritzman, R.

1986-01-01

159

Summary: Our 50-year odyssey with fission  

NASA Astrophysics Data System (ADS)

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 experimental phenomena as deformed ground-state nuclear shapes, fission into fragments of unequal size, sawtooth neutron yields, spontaneously fissioning isomers, broad resonances and narrow intermediate structure in fission cross sections and cluster radioactivity. However, inertial and dissipative forces also play decisive roles in the dynamical evolution of a fissioning nucleus. The energy dissipated between the saddle and scission points is small for low initial excitation energy at the saddle point and increases with increasing excitation energy. At moderate excitation energies, the dissipation of collective energy into internal single-particle excitation energy proceeds largely through the interaction of nucleons with the mean field and with each other in the vicinity of the nuclear surface, as well as through the transfer of nucleons between the two portions of the evolving dumbbell-like system. These unique dissipation mechanisms arise from the Pauli exclusion principle for fermions and the details of the nucleon-nucleon interaction, which make the mean free path of a nucleon near the Fermi surface at low excitation energy longer than the nuclear radius. With its inverse process of heavy-ion fusion reactions, fission continues to yield surprises in the study of large-amplitude collective nuclear motion. Future challenges include devising experiments to unambiguously distinguish dissipative effects from analogous effects caused by collective degrees of freedom and computing fission directly from the underlying hadronic interaction.

Nix, J. Rayford

1989-10-01

160

Tunneling Through Triple-Humped Fission Barriers  

NASA Astrophysics Data System (ADS)

This chapter gives a survey of the latest results obtained for the fission process that takes place when the energy of the compound system is smaller than the energy of the fission barrier. The tunneling and resonant tunneling processes play a role in this energy region. The transmission resonances were studied in high-energy-resolution experiments and the excitation energies, J ? and K values of the states were determined. Rotational bands were constructed, from which the moment of inertia and the degree of the deformation were determined. The implications of these results to the present knowledge of the fission potential extracted from experiments are discussed.

Krasznahorkay, A.

161

Advanced fission models in nuclear data calculations  

NASA Astrophysics Data System (ADS)

Transition states at the saddle points and superdeformed or hyperdeformed states in the secondary wells of multiple-humped potential barriers play an important role in low-energy fission processes. In the present work discrete collective spectra at large nuclear deformations are predicted by means of the dinuclear model and combined with the optical model for fission of the Empire-3 system of codes. The formalism is applied to the 233U(n, f) reaction and the computed cross section compared with recent experimental results of the n_TOF Collaboration. Angular anisotopies of fission fragments are evaluated with an improved version of the scission-point model.

Shneidman, T. M.; Andreev, A. V.; Sin, M.; Massimi, C.; Vannini, G.; Ventura, A.

2012-05-01

162

Origin of the Moon by rotational fission  

SciTech Connect

Consistent with the current understanding of the Moon's bulk composition, internal structure, seismic and tectonic characteristics, evidence is discussed which suggests that the Moon originated by fission. The concepts discussed are: (1) all stars are members of close or contact binary systems; (2) advances in dynamical studies of the fission hypothesis show that stellar bodies also undergo fission; (3) the newly formed proto moon would have lost a large fraction of its original mass via mass transfer; and (4) due to the foregoing concepts the result would be a moon of terrestrial mantle material which was depleted in both metallic iron and volatiles.

Binder, A.B.

1984-01-01

163

Fine Structure in the Velocity Distributions of Slowed Fission Fragments  

Microsoft Academic Search

Fine structure is observed in the velocity distribution of U235 fission fragments that have been slowed by aluminum or nickel, but none is observed for unslowed fragments. Identification of this velocity fine structure with the fine structure in the fission mass yield confirms the influence of the 82-neutron shell in the fission act, as distinguished from its influence in post-fission

R. B. Leachman; H. W. Schmitt

1954-01-01

164

Fission Matrix Capability for MCNP Monte Carlo  

SciTech Connect

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],

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

165

Fission Fragment Studies from Near-Barrier Photo-Fission of Uranium  

NASA Astrophysics Data System (ADS)

We have performed near-barrier photo-fission measurements on uranium at the High Intensity Gamma-ray Source (HIGS) at TUNL. Offline gamma-ray measurements of the activated targets were performed to identify decaying fission fragments and determine their concentrations. Fission fragment analysis can be utilized to help validate the overall fission cross-section determination. The distribution of the fission fragments is expected to be a function of the incident photon energy, especially near the fission threshold. The offline gamma rays were measured with an HPGe detector at the HIGS facility. We measured the gamma ray spectra of the activated targets as a function of time. These spectra were then analyzed to determine the lifetimes of the fragments. We will present the results of our analysis and discuss future prospects.

Tuffley, M. J.; Johnson, M. S.; Hall, J. M.; McNabb, D. P.; Ahmed, M. W.; Stave, S.; Weller, H. R.; Mueller, J. M.; Karwowski, H.; Tompkins, J.

2010-11-01

166

Search for Other Natural Fission Reactors.  

National Technical Information Service (NTIS)

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 approxim...

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

1977-01-01

167

Formation and dynamics of fission fragments  

NASA Astrophysics Data System (ADS)

Although the overall time scale for nuclear fission is long, suggesting a slow process, rapid shape evolution occurs in its later stages near scission. Theoretical prediction of the fission fragments and their characteristics are often based on the assumption that the internal degrees of freedom are equilibrated along the fission path. However, this adiabatic approximation may break down near scission. This is studied for the symmetric fission of 258,264Fm. The nonadiabatic evolution is computed using the time-dependent Hartree-Fock method, starting from an adiabatic configuration where the fragments have acquired their identity. It is shown that dynamics has an important effect on the kinetic and excitation energies of the fragments. The vibrational modes of the fragments in the post-scission evolution are also analyzed.

Simenel, C.; Umar, A. S.

2014-03-01

168

Actual Point About Fission Products Vitrification.  

National Technical Information Service (NTIS)

The main characteristics concerning the continuous vitrification process for the confinement of fission product solutions operated at AVM are summarized. The general principle of a vitrification plant is described. The AVM plant efficiency as also its con...

R. Bonniaud

1982-01-01

169

Electron spectra from decay of fission products  

SciTech Connect

Electron spectra following decay of individual fission products (72 less than or equal to A less than or equal to 162) are obtained from the nuclear data given in the compilation using a listed and documented computer subroutine. Data are given for more than 500 radionuclides created during or after fission. The data include transition energies, absolute intensities, and shape parameters when known. An average beta-ray energy is given for fission products lacking experimental information on transition energies and intensities. For fission products having partial or incomplete decay information, the available data are utilized to provide best estimates of otherwise unknown decay schemes. This compilation is completely referenced and includes data available in the reviewed literature up to January 1982.

Dickens, J K

1982-09-01

170

A new neutron counter for fission research  

NASA Astrophysics Data System (ADS)

A new neutron counter for research experiments on nuclear fission has been developed. This instrument is designed for the detection of prompt fission neutrons within relatively high levels of gamma and neutron background. It is composed of a set of 3He proportional counters arranged within a block of polyethylene which serves as moderator. The detection properties have been studied by means of Monte Carlo simulations and experiments with radioactive sources. These properties are confirmed by an experiment on neutron-induced fission of 238U at the WNR facility of the Los Alamos Neutron Science Center during which the mean prompt fission neutron multiplicity, or ?¯ has been measured from 1 to 20 MeV of incident neutron energy.

Laurent, B.; Granier, T.; Bélier, G.; Chatillon, A.; Martin, J.-F.; Taieb, J.; Hambsch, F.-J.; Tovesson, F.; Laptev, A. B.; Haight, R. C.; Nelson, R. O.; O?Donnell, J. M.

2014-05-01

171

Fusion-fission in light nuclear systems  

SciTech Connect

The fission process, which has been largely ignored for reactions involving light nuclear systems, will be shown to play a significant role in the /sup 32/S + /sup 24/Mg reaction at energies greater than about 1 1/2 times the Coulomb barrier energy. The magnitude of the fusion-fission cross section ant its fragment mass dependence are found to be consistent with newer estimates of the fission barriers in lighter systems. The presence of the fission mechanism has significance for understanding the limitation to fusion at higher energies and has implications for comparisons of model calculations of evaporation-residue and associated light-particle yields with experiment. 17 refs., 8 figs.

Sanders, S.J.

1988-01-01

172

Proton-induced fission of iridium  

NASA Astrophysics Data System (ADS)

The isotopic distribution of rubidium produced in the proton induced fission of iridium has been measured at 68, 85, and 100 MeV incident beam energies using an on-line mass spectrometer with a surface ionization ion source. The deduced neutron multiplicities are substantially higher and show a steeper energy dependence compared to similar measurements done with a heavy ion beam in this mass region and in the same range of excitation energies. This might confirm an effect of the angular momentum of the fissioning nucleus on the fragment deexcitation mechanism. NUCLEAR REACTIONS, FISSION 191,193Ir(p,f), Ep=68, 85, 100 MeV; measured independent relative yields of Rb. Deduced total number of neutrons emitted in symmetric fission.

Pathak, B. P.; Lessard, L.; Nikkinen, L.; Lee, J. K. P.

1982-05-01

173

Ternary fission induced by polarized neutrons  

NASA Astrophysics Data System (ADS)

Ternary fission of (e,e) U- and Pu- isotopes induced by cold polarized neutrons discloses some new facets of the process. In the so-called ROT effect shifts in the angular distributions of ternary particles relative to the fission fragments show up. In the so-called TRI effect an asymmetry in the emission of ternary particles relative to a plane formed by the fragment momentum and the spin of the neutron appear. The two effects are shown to be linked to the components of angular momentum perpendicular and parallel to the fission axis at the saddle point of fission. Based on theoretical models the spectroscopic properties of the collective transitional states at the saddle point are inferred from experiment.

Gönnenwein, Friedrich

2013-12-01

174

Microscopic Fission Barriers of Very Heavy Nuclei  

Microsoft Academic Search

The fission barriers of sixteen isotopes of Californium, Fermium and Nobelium have been microscopically calculated up to and beyond the second saddle point within Hartree-Fock plus pairing approaches. The Skyrme density-dependent effective force in its SkM* parametrization - rather well suited to the description of fission barriers - was used in the particle-hole channel. As for the treatment of pairing

L. Bonneau; T. L. Ha; D. Samsoen; P. Quentin; N. Pillet

2002-01-01

175

Overview of tritium fast-fission yields  

SciTech Connect

Tritium production rates are very important to the development of fast reactors because tritium may be produced at a greater rate in fast reactors than in light water reactors. This report focuses on tritium production and does not evaluate the transport and eventual release of the tritium in a fast reactor system. However, if an order-of-magnitude increase in fast fission yields for tritium is confirmed, fission will become the dominant production source of tritium in fast reactors.

Tanner, J.E.

1981-03-01

176

MCNP6 Fission Multiplicity with FMULT Card  

SciTech Connect

With the merger of MCNPX and MCNP5 into MCNP6, MCNP6 now provides all the capabilities of both codes allowing the user to access all the fission multiplicity data sets. Detailed in this paper is: (1) the new FMULT card capabilities for accessing these different data sets; (2) benchmark calculations, as compared to experiment, detailing the results of selecting these separate data sets for thermal neutron induced fission on U-235.

Wilcox, Trevor [Los Alamos National Laboratory; Fensin, Michael Lorne [Los Alamos National Laboratory; Hendricks, John S. [Los Alamos National Laboratory; James, Michael R. [Los Alamos National Laboratory; McKinney, Gregg W. [Los Alamos National Laboratory

2012-06-18

177

Fast-fission tokamak breeder reactors  

Microsoft Academic Search

A fast-fission blanket around a fusion plasma exploits high neutron multiplication for superior breeding and high-energy multiplication to generate significant net electrical power. A major improvement over previous fast-fission blanket concepts is the use of mobile fuel, namely a pebble-bed configuration with helium cooling. Upon loss of coolant, the mobile fuel can be gravity-dumped to a separately cooled dump tank

D. L. Jassby; D. H. Berwald; J. Garner; R. H. Whitley; I. Maya; C. P. C. Wong; J. D. Lee; R. W. Moir; D. R. Cohn

1986-01-01

178

Modeling Fission Product Sorption in Graphite Structures  

SciTech Connect

The goal of this project is to determine changes in adsorption and desorption of fission products to/from nuclear-grade graphite in response to a changing chemical environment. First, the project team will employ principle calculations and thermodynamic analysis to predict stability of fission products on graphite in the presence of structural defects commonly observed in very high- temperature reactor (VHTR) graphites. Desorption rates will be determined as a function of partial pressure of oxygen and iodine, relative humidity, and temperature. They will then carry out experimental characterization to determine the statistical distribution of structural features. This structural information will yield distributions of binding sites to be used as an input for a sorption model. Sorption isotherms calculated under this project will contribute to understanding of the physical bases of the source terms that are used in higher-level codes that model fission product transport and retention in graphite. The project will include the following tasks: Perform structural characterization of the VHTR graphite to determine crystallographic phases, defect structures and their distribution, volume fraction of coke, and amount of sp2 versus sp3 bonding. This information will be used as guidance for ab initio modeling and as input for sorptivity models; Perform ab initio calculations of binding energies to determine stability of fission products on the different sorption sites present in nuclear graphite microstructures. The project will use density functional theory (DFT) methods to calculate binding energies in vacuum and in oxidizing environments. The team will also calculate stability of iodine complexes with fission products on graphite sorption sites; Model graphite sorption isotherms to quantify concentration of fission products in graphite. The binding energies will be combined with a Langmuir isotherm statistical model to predict the sorbed concentration of fission products on each type of graphite site. The model will include multiple simultaneous adsorbing species, which will allow for competitive adsorption effects between different fission product species and O and OH (for modeling accident conditions).

Szlufarska, Izabela [University of Wisconsin, Madison, WI (United States); Morgan, Dane [University of Wisconsin, Madison, WI (United States); Allen, Todd [University of Wisconsin, Madison, WI (United States)

2013-04-08

179

Calculated fission properties of the heaviest elements  

Microsoft Academic Search

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

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

1986-01-01

180

Ion sources for fission fragment accelerators  

Microsoft Academic Search

At the Grenoble and Munich high-flux reactors fission fragment accelerators are under design which will deliver beams of very neutron-rich fission products with a final energy between 3 and 6 MeV\\/u. In order to obtain an efficient acceleration in a compact accelerator, charge conversion of the 1+ ion beams from the in-pile ion source to a q\\/A>=0.16 has to take

U. Köster; O. Kester; D. Habs

1998-01-01

181

Search for inverse fission of uranium  

NASA Astrophysics Data System (ADS)

Background: There is a long-term interest in running the fission reaction backward, i.e., studying the “inverse fission” of uranium. The recent availability of beams of n-rich fission fragments has stimulated interest in this endeavor.Purpose: To search for inverse fission in the reactions 124,132Sn + 100Mo.Method: In the 124Sn + 100Mo reaction, evaporation residues were searched for using in-beam detection of evaporation residues, in-beam ? spectroscopy, and post-irradiation ? spectroscopy, while in the 132Sn + 100Mo reaction, the evaporation residue 230U was searched for using post-irradiation ? spectroscopy.Results: No evidence for the occurrence of the inverse fission reactions was found. The upper-limit cross section for the latter reaction is ˜550 ?b, while the experimental upper-limit cross section for the former reaction is about 21-21+38 nb.Conclusions: The intensity of suitable radioactive beams is not high enough at present to detect inverse fission. For the 124Sn + 100Mo reaction, the observed upper limits are below the estimates of current models for these reactions, probably due to fusion hindrance.

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

2012-04-01

182

Shape Isomers - a Key to Fission Barriers  

NASA Astrophysics Data System (ADS)

Quantitative predictions of fission product yields are relevant for the reliable operation of different modern nuclear applications. This concerns the realistic characterizations of the radio-toxicity of the fuel elements after the envisaged extended irradiation, as well as sub-critical assemblies, where the number of delayed neutrons from minor actinides is determined by the characteristic emission yields of the corresponding so-called pre-cursor isotopes. However, to be able to make more reliable quantitative predictions of fission characteristics requires the better understanding of the fission process itself. For this purpose a better knowledge about the distinct structure of the nuclear energy landscape around the fission barrier is indispensable. In particular, the question should be answered, whether the fission barrier is either double- or triple-humped or even multi-humped as been proposed within the multi-modal neck rupture model. Despite quite some effort based on different experimental techniques and theoretical approaches, this question remains still unanswered. There is still no consistent picture of the fission barrier available and hence, different sets of barrier parameters are in use, unable to describe the different observed phenomena in a coherent way. With the systematic investigation of shape isomer population, its decay modes as well as the branching ratio, precise information can be obtained to resolve the puzzling situation. The experimental approach will be discussed and results from first experiments presented.

Oberstedt, S.; Hambsch, F.-J.; Kornilov, N.; Lövestam, G.; Oberstedt, A.; Gawrys, M.

2008-04-01

183

Mapping a buried Quaternary valley and pre-Quaternary faults through seismic methods in Copenhagen, Denmark.  

NASA Astrophysics Data System (ADS)

Limited knowledge of the subsurface geology motivates the use of geophysical techniques before large engineering projects are conducted. These applications are normally restricted to satisfy the project aims, like mapping the near surface sediments, unconsolidated rocks and/or geological structures that may affect the construction locally. However, the applications can also contribute to the general knowledge of the regional geology around the location of interest. This report highlights the mapping of a buried Quaternary valley and identification of regional faults by a reflection and refraction seismic survey performed in Copenhagen. A 13.9 Km seismic survey was carried out at Copenhagen city along six crooked lines in order to determine the velocity fields in the near subsurface segment of a planned metro line and reflection patterns in deeper levels. The aim of the survey was to collect information needed for designing the underground metro. In particular it was sought to map the interface between Quaternary sedimentary layers of clay, till and sand, and the underlying layers of Palaeogene limestone found between 7 and 40 m below the ground surface. The data acquisition was carried out using a 192 channels array, receiver groups with 5 m spacing and a Vibroseis as a source at 5 m spacing following a roll along technique to complete the survey spreads. The urban environment demanded extensive survey planning including traffic control, notifications to residents and a fluent coordination with municipal authorities in order to minimize disturbances and ensure data acquisition. The reflection data was processed under a conventional scheme and the refraction data was interpreted using a non-linear traveltime tomography algorithm. The reflection results indicate the presence of faults oriented NW-SE to NNW-SSE affecting the limestone sequences. The faults may be associated to the Sorgenfrei-Tornquist Zone at the transition between the Danish Basin and the Baltic Shield. The refraction interpretation allowed the mapping of the velocity distribution in the upper sediments and their interface with the underlying limestone sequences. In this work two sections along the northern part of the survey are presented and discussed. The cases show the ability of the seismic results to image the presence of a buried valley that has been previously reported but was geophysically mapped for the first time under these investigations. The results delineate the sediments-limestone interface as the depth to the limestone increases. These results are validated through borehole data from locations along the surveyed lines. Other minor lateral variations are also observed and compared to a geological model. The location of the buried valley corresponds to a fault zone observed in the reflection seismic investigation. Accordingly, the location of the valley may in part have been controlled by the faults. The overall results of the seismic investigations are currently being used as part of the design basis for the construction of the metro line and may be useful for future engineering projects in the area. In general, the investigation results demonstrated that in addition to meet specific project objectives near surface geophysics has the potential to provide insights to the general understanding of geological processes. The authors wish to acknowledge Metroselskabet I/S for permission in presenting the results, and the Cityringen Joint Venture partners COWI, Arup and Systra.

Martinez, Kerim; Alfredo Mendoza, Jose; Henrik, Olsen

2010-05-01

184

Quaternary sedimentation of the principal deltas of Vietnam  

NASA Astrophysics Data System (ADS)

Quaternary depressions in Vietnam (namely the Cuulong River, the Red River, and coastal depressions in the central part of the country) were filled mainly by continental deposits in five cycles as follows: (V) Upper Holocene (Thaibinh and Dongkhoi formations); (IV) Lower to Middle Holocene (Haihung and Tanthanh Binh-chanh formations); (III) Upper Pleistocene (Vinhphuc formation); (II) Middle to Upper Pleistocene (Hanoi and Thuduc formations); (I) Lower Pleistocene (Lechi, Trangbom, and Hoanghoa formations). Each cycle starts with a regression and ends with a transgression. Within the Quaternary the maximum regressive phase was in the Middle to Upper Pleistocene (beginning of cycle II) and the maximum transgressive phase in the Middle Holocene (end of cycle IV).

Nghi, Tran; Ngo Quang Toan; Do Thi Van Thanh; Nguyen Dinh Minh; Nguyen Van Vuong

185

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

SciTech Connect

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.

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

2008-11-18

186

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.

187

Organic non-quaternary clathrate salts for petroleum separation  

SciTech Connect

A method is described for separating hydrocarbon feed streams containing mixtures of aromatic hydrocarbons and non-aromatic hydrocarbons into aromatics lean raffinate streams and aromatics rich extract streams by contacting the hydrocarbon feed streams with an organic non-quaternary clathrate salt having less than 16 carbon atoms in the cation, whereby the clathrate salt selectively interacts with the aromatic component of the hydrocarbon feed mixture producing a raffinate phase of reduced aromatic content a hydrocarbon - salt clathrate and an extract phase of increased aromatic content containing the clathrate salt and combined aromatic hydrocarbon, separating the raffinate phase from the extract phase and releasing the aromatic hydrocarbon from the clathrate salt of the extract phase to recover an aromatics rich stream and the organic non-quaternary salt which is recycled for contact with fresh hydrocarbon feed.

Boate, D.R.; Zaworotko, M.J.

1993-06-15

188

Unexpected primitive rodents in the Quaternary of Argentina  

NASA Astrophysics Data System (ADS)

This article describes the first fossils recorded in the Hernandarias Formation (Pleistocene) in Entre Ríos province (eastern Argentina). They are represented by three teeth assigned to the caviomorph rodents (Rodentia, Mammalia) Aenigmys diamantensis gen. et sp. nov. and Eumysops. To establish the phylogenetic affinities of the two most enigmatic teeth, their enamel microstructure was studied. Aenigmys diamantensis is considered the most primitive taxon of a clade formed by Dinomyidae-Neoepiblemidae-Heptaxodontidae. Evidence of the close relationships among these families also is presented herein. The new fossils reinforce previous hypotheses about the survival of primitive Brazilian taxa after their extinction in the Pampas and Patagonia of southern South America. They also show that the diversity of caviomorph rodents during the Quaternary was greater than supposed and that an important Quaternary extinction, not previously detected, affected several lineages. With the available evidence, it is not possible to determine if these rodents indicate a warm pulse or a particular biogeographic situation in Entre Ríos.

Vucetich, María G.; Vieytes, Emma C.; Verzi, Diego H.; Noriega, Jorge I.; Tonni, Eduardo P.

2005-10-01

189

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

PubMed

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 (kobs) 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

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

2014-10-13

190

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

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.

S. Frank

2009-09-01

191

Fission neutron source in Rome  

NASA Astrophysics Data System (ADS)

A fission neutron source is operating in Rome at the ENEA Casaccia Research Center since 1971, consisting of a low power fast reactor named RSV-Tapiro. it is employed for a variety of experiments, including dosimetry, material testing, radiation protection and biology. In particular, application to experimental radiobiology includes studies of the biological action of neutrons in the whole-body irradiated animal, or in specialized systems in vivo or in vitro. For his purpose a vertical irradiation facility was originally constructed. Recently, a new horizontal irradiation facility has been designed to allow the exposure of larger samples or larger sample batches at one time. Dosimetry at the sample irradiation positions is routinely carried out by the conventional method of using two ion chambers. This physical dosimetry has recently been compared with the results of biological dosimetry based on the detection of chromosomal aberrations in peripheral blood human lymphocytes irradiated in vitro. A characterization of the radiation quality in the two configurations has been carried out by tissue equivalent proportional counter microdosimetry measurements. Information about the main characteristics of the reactor and the two irradiation facilities is provided and relevant results of the various measurements are summarized. Radiobiological results obtained using this neutron source are also briefly outlined.

Coppola, Mario; di Majo, V.; Ingrao, G.; Rebessi, S.; Testa, A.

1997-02-01

192

Fission-fusion neutron source  

NASA Astrophysics Data System (ADS)

In order to meet the requirements of fusion power reactors and nuclear waste treatment, a concept of fission-fusion neutron source is proposed, which consists of a LiD assembly located in the heavy water region of the China Advanced Research Reactor. This assembly of LiD fuel rods will be irradiated with slow neutrons and will produce fusion neutrons in the central hole via the reaction 6Li(n, ?). More precisely, tritium ions with a high energy of 2.739 MeV will be produced in LiD by the impinging slow neutrons. The tritium ions will in turn bombard the deuterium ions present in the LiD assembly, which will induce fusion reaction and then the production of 14 MeV neutrons. The fusion reaction rate will increase with the accumulation of tritium in LiD by the reaction between tritium and deuteron recoils produced by the 14 MeV neutrons. When the concentration of tritium reaches 0.5 · 10 22 and the fraction of fusion reactions between tritium and deuteron recoils approaches 1, the 14 MeV neutron flux is doubled and redoubled, an so forth, approaching saturation in which the tritium produced at a time t is exhausted by the fusion reactions to keep constant the tritium concentration in LiD.

Yu, Jinnan; Yu, Gang

2009-04-01

193

The impact of Quaternary Ice Ages on mammalian evolution.  

PubMed

The Quaternary was a time of extensive evolution among mammals. Most living species arose at this time, and many of them show adaptations to peculiarly Quaternary environments. The latter include continental northern steppe and tundra, and the formation of lakes and offshore islands. Although some species evolved fixed adaptations to specialist habitats, others developed flexible adaptations enabling them to inhabit broad niches and to survive major environmental changes. Adaptation to short-term (migratory and seasonal) habitat change probably played a part in pre-adapting mammal species to the longer-term cyclical changes of the Quaternary. Fossil evidence indicates that environmental changes of the order of thousands of years have been sufficient to produce subspeciation, but speciation has typically required one hundred thousand to a few hundred thousand years, although there are both shorter and longer exceptions. The persistence of taxa in environments imposing strong selective regimes may have been important in forcing major adaptive change. Individual Milankovitch cycles are not necessarily implicated in this process, but nor did they generally inhibit evolutionary change among mammals: many evolutionary divergences built over multiple climatic cycles. Deduction of speciation timing requires input from fossils and modern phenotypic and breeding data, to complement and constrain mitochondrial DNA coalescence dates which appear commonly to overestimate taxic divergence dates and durations of speciation. Migrational and evolutionary responses to climate change are not mutually exclusive but, on the contrary, may be synergistic. Finally, preliminary analysis suggests that faunal turnover, including an important element of speciation, was elevated in the Quaternary compared with the Neogene, at least in some biomes. Macroevolutionary species selection or sorting has apparently resulted in a modern mammalian fauna enriched with fast-reproducing and/or adaptively generalist species. PMID:15101579

Lister, Adrian M

2004-02-29

194

Fractionation of Serum Proteins with a Quaternary Ammonium Detergent  

Microsoft Academic Search

THE fractionation of serum proteins with the aid of quaternary ammonium compounds has met with difficulties, because the detergent\\/protein ratio must be maintained at a very constant level1. We have shown that this is no longer necessary if `Desogen' (methylphenyl dodecyltrimethyl-ammonium-methosulphate, Geigy S.A., Basle) is used. Separation into at least four components can be performed by the following method.

F. J. Loomeijer

1950-01-01

195

Sorption of quaternary ammonium compounds to municipal sludge  

Microsoft Academic Search

The sorptive behavior of four quaternary ammonium compounds (QACs) – hexadecyl trimethyl ammonium chloride (C16TMA), dodecyl trimethyl ammonium chloride (C12TMA), hexadecyl benzyl dimethyl ammonium chloride (C16BDMA), and dodecyl benzyl dimethyl ammonium chloride (C12BDMA) – to municipal primary, waste activated, mesophilic digested, and thermophilic digested sludges was assessed at 22°C. Batch adsorption of all four separately tested QACs to primary sludge

Zainab Z. Ismail; Ulas Tezel; Spyros G. Pavlostathis

2010-01-01

196

Sorption of Polymeric Quaternary Ammonium Compounds to Humic Acid  

Microsoft Academic Search

Polymeric quaternary ammonium salts or polyquaterniums are used not only in the water and wastewater industry but also in\\u000a cosmetics. The former have been extensively studied with sorption to wastewater treatment plant (WWTP) biosolids an important\\u000a factor in their fate, mitigating release to the environment. Compounds of cosmetic origin have not received the same scrutiny\\u000a as those used in other

Janet Cumming; Darryl William Hawker; Heather Chapman; Kerry Nugent

2011-01-01

197

Ternary and quaternary mixed electrolytes for lithium cells  

Microsoft Academic Search

This paper reports the influence of composition of mixed solvent electrolyte composition on the discharge capacity and charge–discharge cycle life of lithium metal\\/amorphous V2O5–P2O5 (95:5 in molar ratio) cells. The solvents used were ethylene carbonate (EC), propylene carbonate (PC), 2-methyltetrahydrofuran (2MeTHF) and THF. LiAsF6 was used as the solute. The electrolyte solutions examined here contain ternary and quaternary mixed systems.

S. I. Tobishima; K. Hayashi; Y. Nemoto; S. Sugihara; J. I. Yamaki

1999-01-01

198

Low Sensitivity of Listeria monocytogenes to Quaternary Ammonium Compounds  

Microsoft Academic Search

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

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

2000-01-01

199

Design of quaternary Ir-Nb-Ni-Al refractory superalloys  

SciTech Connect

The authors propose a method for developing new quaternary Ir-Nb-Ni-Al refractory superalloys for ultra-high-temperature uses, by mixing two types of binary alloys, Ir-20 at. pct Nb and Ni-16.8 at. pct Al, which contain fcc/L1{sub 2} two-phase coherent structures. For alloys of various Ir-Nb/Ni-Al compositions, the authors analyzed the microstructure and measured the compressive strengths. Phase analysis indicated that three-phase equilibria--fcc, Ir{sub 3}Nb-L1{sub 2}, and Ni{sub 3}Al-L1{sub 2}--existed in Ir-5Nb-62.4Ni-12.6A1(at.pct) (alloy A), Ir-10Nb-41.6Ni-8.4Al(at.pct)(alloy B), and Ir-15Nb-20.8Ni-4.2Al(at.pct)(alloy C) at 1,400 C; at 1,300 C, three phase equilibria--fcc, Ir{sub 3}Nb, and Ni{sub 3}Al--existed in alloys A and C and four-phase equilibria--fcc, Ir{sub 3}Nb, Ni{sub 3}Al, and IrAl-B2--existed in alloy B. The fcc/L1{sub 2} coherent structure was examined by using transmission electron microscopy (TEM). At a temperature of 1,200 C, the compressive strength of these quaternary alloys was between 130 and 350 MPa, which was higher than that of commercial Ni-based superalloys, such as MarM247 (50 MPa), and lower than that of Ir-based binary alloys (500 MPa). Compared to Ir-based alloys, the compressive strain of these quaternary alloys was greatly improved. The potential of the quaternary alloys for ultra-high-temperature use is also discussed.

Yu, X.H.; Yamabe-Mitarai, Y.; Ro, Y.; Harada, H.

2000-01-01

200

Humidity sensor using epoxy resin containing quaternary ammonium salts  

Microsoft Academic Search

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

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

2001-01-01

201

Quaternary Constant-Amplitude Codes for Multicode CDMA  

Microsoft Academic Search

A constant-amplitude code is a code that reduces the peak-to-average power ratio (PAPR) in multicode code-division multiple access (MC-CDMA) systems to the favorable value 1. In this paper, quaternary constant-amplitude codes (codes over Z 4) of length 2 m with error-correction capabilities are studied. These codes exist for every positive integer m, while binary constant-amplitude codes cannot exist if m

Kai-Uwe Schmidt

2009-01-01

202

Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis  

NASA Astrophysics Data System (ADS)

A new AGU title, Methane Hydrates in Quaternary Climate Change: The Clathrate Gun Hypothesis, by James P. Kennett, Kevin G. Cannariato, Ingrid L. Hendy and Richard J. Behl, presents an alternate hypothesis to explain climate behavior, including abrupt warming over the past 800,000 years. According to the Clathrate Gun Hypothesis, periodic releases of atmospheric methane from melting methane hydrate amplified a pattern of temperature fluctuations and triggered "greenhouse" warming that led to an increase in global temperatures.

203

Quaternary Benzo[C]Phenanthridine Alkaloids — Biological Activities  

Microsoft Academic Search

\\u000a Quarternary benzo[c]phenanthridine alkaloids (QBA) are a small class of compounds commonly isolated from Caprifoliaceae, Fumariaceae,\\u000a Meliacea, Papaveraceae and Rutaceae plants. QBA belong to the elicitor-inducible secondary metabolites and are considered\\u000a phytoalexines because of their antifungal and nematocidal activities. Quaternary benzo[c]phenanthridine alkaloids whose most\\u000a studied representatives are sanguinarine (SA), chelerythrine (CHE), and fagaronine (FA) (Fig. 1) display a wide spectrum of

V. Šimánek; R. Vespalec; A. Šedo; J. Ulrichová; J. Vi?ar

204

Quaternary subsidence zones in Albania: some case studies  

Microsoft Academic Search

The Neotectonic evolution of Albania, from the Middle Pleistocene to the present day, is characterised by a general uplift\\u000a that began after the Pliocene. Subsidence took place locally and led to the formation of graben-shaped Quaternary lakes and\\u000a plains. During this period, graben lakes were formed at Shkodra, Ohrid, Prespa and Butrinti, whereas at Korça, Elbasani, Zadrima,\\u000a Tirana, Myzeqe, etc.,

Sh. Aliaj; G. Baldassarre; D. Shkupi

2001-01-01

205

Transport phenomena in a reactive quaternary gas mixture  

Microsoft Academic Search

Quaternary gas mixtures which undergo a binary and reversible chemical reaction of the type A+B&rlhar2;C+D are analyzed within the framework of Boltzmann equation in order to investigate the effects caused by the reactions on the transport coefficients. The gas system is considered close to chemical equilibrium, a state in which the affinity has a small value characterizing the final stage

Adriano W. Silva; Giselle M. Alves; Gilberto M. Kremer

2007-01-01

206

Protein Flexibility Facilitates Quaternary Structure Assembly and Evolution  

PubMed Central

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.

Marsh, Joseph A.; Teichmann, Sarah A.

2014-01-01

207

Microstructure development in Al-Cu-Ag-Mg quaternary alloy  

NASA Astrophysics Data System (ADS)

The solidification behaviour of multi-component and multi-phase systems has been largely investigated in binary and ternary alloys. In the present study, a quaternary model system is proposed based on the well known Al-Cu-Ag and Al-Cu-Mg ternary eutectic alloys. The quaternary eutectic composition and temperature were determined by EDS (Energy Dispersive Spectrometry) and DSC (Differential Scanning Calorimetry) analysis, respectively. The microstructure was then characterised by SEM (Scanning Electron Microscope). In the DSC experiments, two types of quaternary eutectics were determined according to their phase composition. For each type of eutectic, various microstructures were observed, which result in different eutectic compositions. Only one of the determined eutectic compositions was further studied by the controlled growth technique in a vertical Bridgeman type furnace. In the initial part of the directionally solidified sample, competing growth between two-phase dendrites and three-phase eutectics was obtained, which was later transformed to competing growth between three-phase and four-phase eutectics. Moreover, silver enrichment was measured at the solidification front, which is possibly caused by Ag sedimentation due to gravity and Ag rejection from dendritic and three-phase eutectic growth, and its accumulation at the solidification front.

Zhou, Bin; Froyen, L.

2012-01-01

208

Ecological impacts of the late Quaternary megaherbivore extinctions.  

PubMed

As a result of the late Quaternary megafaunal extinctions (50,000-10,000 before present (BP)), most continents today are depauperate of megaherbivores. These extinctions were time-transgressive, size- and taxonomically selective, and were caused by climate change, human hunting, or both. The surviving megaherbivores often act as ecological keystones, which was likely true in the past. In spite of this and extensive research on the causes of the Late Quaternary Extinctions, the long-term ecological consequences of the loss of the Pleistocene megafauna remained unknown until recently, due to difficulties in linking changes in flora and fauna in paleorecords. The quantification of Sporormiella and other dung fungi have recently allowed for explicit tests of the ecological consequences of megafaunal extirpations in the fossil pollen record. In this paper, I review the impacts of the loss of keystone megaherbivores on vegetation in several paleorecords. A growing number of studies support the hypothesis that the loss of the Pleistocene megafauna resulted in cascading effects on plant community composition, vegetation structure and ecosystem function, including increased fire activity, novel communities and shifts in biomes. Holocene biota thus exist outside the broader evolutionary context of the Cenozoic, and the Late Quaternary Extinctions represent a regime shift for surviving plant and animal species. PMID:24649488

Gill, Jacquelyn L

2014-03-01

209

Anticholinesterase inhibitory activity of quaternary alkaloids from Tinospora crispa.  

PubMed

Quaternary alkaloids are the major alkaloids isolated from Tinospora species. A previous study pointed to the necessary presence of quaternary nitrogens for strong acetylcholinesterase (AChE) inhibitory activity in such alkaloids. Repeated column chromatography of the vine of Tinospora crispa extract led to the isolation of one new protoberberine alkaloid, 4,13-dihydroxy-2,8,9-trimethoxydibenzo[a,g]quinolizinium (1), along with six known alkaloids-dihydrodiscretamine (2), columbamine (3), magnoflorine (4), N-formylannonaine (5), N-formylnornuciferine (6), and N-trans-feruloyltyramine (7). The seven compounds were isolated and structurally elucidated by spectroscopic analysis. Two known alkaloids, namely, dihydrodiscretamine and columbamine are reported for the first time for this plant. The compounds were tested for AChE inhibitory activity using Ellman's method. In the AChE inhibition assay, only columbamine (3) showed strong activity with IC50 48.1 µM. The structure-activity relationships derived from these results suggest that the quaternary nitrogen in the skeleton has some effect, but that a high degree of methoxylation is more important for acetylcholinesterase inhibition. PMID:24448061

Yusoff, Mashitah; Hamid, Hazrulrizawati; Houghton, Peter

2014-01-01

210

Quaternary salts containing the pentafluorosulfanyl (SF5) group.  

PubMed

The first quaternary salts of pyridine (2), N-methyl imidazole (3), N-propyl triazole (4), and pyridazine (5) that contain the pentafluorosulfanyl (SF(5)) group were prepared and characterized. Neat reactions of the aromatic nitrogen compounds with SF(5)(CF(2))(n)(CH(2))(m)I (n = 2 or 4, m = 2 or 4) gave quaternary iodides 6a-c, 7a-c, 8a, and 9a,b, which were metathesized with LiN(SO(2)CF(3))(2) to form the bis(trifluoromethylsulfonyl)amides 10a-c, 11a-c, 12a, and 13a,b, in high yields. With the exception of the pyridine bis(trifluoromethylsulfonyl)amide salts, the compounds melted or exhibited a T(g) at <0 degrees C. The methylimidazolium, pyridinium, and pyridazinium salts exhibited densities of approximately 2 g/cm(3). Particularly striking was the density of CF(3)(CF(2))(5)(CH(2))(2)-pyridazinium N(CF(3)SO(2))(2) measured at 2.13 g/cm(3); however, an atypically high density for the 1-CF(3)(CF(2))(5)(CH(2))(2)-3-methyl imidazolium amide (14) was also observed at 1.77 g/cm(3). All quaternary salts were characterized via IR, (19)F, (1)H, and (13)C NMR spectra and elemental analyses. PMID:12971788

Singh, Rajendra P; Winter, Rolf W; Gard, Gary L; Gao, Ye; Shreeve, Jean'ne M

2003-09-22

211

Quaternary diversification in European alpine plants: pattern and process.  

PubMed Central

Molecular clock approaches applied previously to European alpine plants suggest that Primula sect. Auricula, Gentiana sect. Ciminalis and Soldanella diversified at the beginning of the Quaternary or well within this period, whereas Globularia had already started diversifying in the (Late-)Tertiary. In the first part of this paper we present evidence that, in contrast to Globularia and Soldanella, the branching patterns of the molecular internal transcribed spacer phylogenies of both Primula and Gentiana are incompatible with a constant-rates birth-death model. In both of these last two taxa, speciation probably decreased through Quaternary times, perhaps because of some niche-filling process and/or a decrease in specific range size. In the second part, we apply nonlinear regression analyses to the lineage-through-time plots of P. sect. Auricula to test a range of capacity-dependent models of diversification, and the effect of Quaternary climatic oscillations on diversification and extinction. At least for one major clade of sect. Auricula there is firm evidence that both diversification and extinction are a function of temperature. Intriguingly, temperature appears to be correlated positively with extinction, but negatively with diversification. This suggests that diversification did not take place, as previously assumed, in geographical isolation in high-altitude interglacial refugia, but rather at low altitudes in geographically isolated glacial refugia.

Kadereit, Joachim W; Griebeler, Eva Maria; Comes, Hans Peter

2004-01-01

212

Simulation of Quaternary glacial cycles with fully interactive carbon cycle  

NASA Astrophysics Data System (ADS)

Although it is generally accepted that, as postulated by the Milankovitch theory, Earth's orbital variations play an important role in Quaternary climate dynamics, the mechanism of glacial cycles still not fully understood. Among major scientific challenges remains the understanding of the nature of 100 kyr cycles that dominated climate variability over the late part of Quaternary and a strong link between ice volume and atmospheric CO2 concentration. Here using the Earth system model of intermediate complexity CLIMBER-2 which includes 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 - we performed simulations of the Quaternary climate cycles using variations in the Earth's orbital parameters as the only prescribed climate forcing. Thanks to high computational efficiency of the CLIMBER-2 model we performed a large suite of model simulations aimed on better understanding the role of individual processes. We found that the main drivers of atmospheric CO2 evolve with time: changes in sea surface temperature and volume of bottom water of southern origin exert CO2 control during glacial inception and deglaciation, while changes in carbonate chemistry and marine biology are dominant during the first and second parts of the glacial cycles, respectively. Changes in terrestrial carbon pool play significant role during deglaciation. We also discus how paleoclimate records, such as atmospheric and deep oceanic d13C, can help to constrain model parameters and test hypotheses on the mechanism of glacial-interglacial CO2 variations.

Ganopolski, Andrey; Brovkin, Victor

2014-05-01

213

Spatiotemporal variation in exhumation of the Crystallines in the NW-Himalaya, India: Constraints from fission track dating analysis  

NASA Astrophysics Data System (ADS)

During Himalayan orogeny, coeval thrusting along the Main Central/Munsiari Thrust (MCT/MT) and extension along the South Tibetan-Detachment System (STDS) are widely responsible for rapid exhumation of the Higher Himalayan Crystalline (HHC) zone. Apatite and zircon fission-track data along the Kaliganga and Darma valleys in the Kumaon Himalaya serve to document the shallow bedrock exhumation history of the HHC. Taking into account sample location within the HHC with respect to the MCT/MT, the apatite fission track (AFT) data-sets along the Darma (1.0 ± 0.1 to 2.8 ± 0.3 Ma) and Kaliganga (1.4 ± 0.2 to 2.4 ± 0.3 Ma) which are sharing same structural setting and rock types and being separated by 40 km, show very similar patterns of exhumation histories since Plio-Quaternary in the Kumaon Himalaya. Data sets along Darma and Kaliganga are very similar to data set of adjacent traverse (50 km away) along the Goriganga valley studied by Patel and Carter (2009). Whole data sets within the HHC in Kumaon Himalaya provide clear evidence for Plio-Quaternary tectonic activity along the Vaikrita Thrust (VT). Precipitation in this region exerts a strong influence on erosional surface processes. Fluvial erosional unloading along the Himalaya is focused on the high mountainous region of the HHC, where the orographic barrier forces out the maximum percentage of annual rainfall. FT cooling ages reveal coincidence between rapid erosion and exhumation that is focused in a ~ 25-30 km wide sector of the HHC, rather than covering the entire orogen. Similarity of AFT age pattern and exhumation rates along all three major traverses (Goriganga, Darma and Kaliganga) indicates that the region has been experiencing constant rate of crustal uplift and erosion since long time. Comparison of fission track ages from the Kumaon Himalaya with other segments of the NW-Himalaya shows spatiotemporal variation in exhumation. It is described due to the development of local structures such as dome/window in Jammu and Kashmir and Himachal Himalayas and Quaternary active thrusting along the VT and MCT/MT in the Garhwal-Kumaon Himalaya.

Patel, R. C.; Adlakha, Vikas; Lal, Nand; Singh, Paramjeet; Kumar, Y.

2011-05-01

214

Microscopic Description of Nuclear Fission:. Fission Barrier Heights of Even-Even Actinides  

NASA Astrophysics Data System (ADS)

We evaluate the performance of modern nuclear energy density functionals for predicting inner and outer fission barrier heights and energies of fission isomers of even-even actinides. For isomer energies and outer barrier heights, we find that the self-consistent theory at the HFB level is capable of providing quantitative agreement with empirical data.

McDonnell, J.; Schunck, N.; Nazarewicz, W.

2014-09-01

215

Prompt gamma-ray coincidences from U-235 induced fission  

NASA Astrophysics Data System (ADS)

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.

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

1999-10-01

216

[Evaluating the effect of quaternary ammonium disinfectants on bacterial strains of animal origin].  

PubMed

The authors evaluate two quaternary ammonium compounds, first and second generation, using three methods: minimum bactericide concentration, the suspension test of the German Society for Hygiene and Microbiology and the agar gel diffusion test. The compounds were tested against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Enterococcus faecalis from sheep and pigs. The results show that quaternary ammonia compounds with dodecyl chains have greater efficacy than benzalconium chloride, and that quaternary ammonium compounds are more effective against gram-positive bacteria. No resistance linked to the strains used in the tests was detected. Finally, the authors demonstrate that all three techniques are valid for the evaluation of quaternary ammonium disinfectants. PMID:15005566

Rueda, J; Amigot Lázaro, J A; Ducha, J

2003-12-01

217

Mass distribution in 11B induced fission of 232Th  

NASA Astrophysics Data System (ADS)

Formation cross sections of several fission products have been determined using recoil catcher technique followed by ?-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 have been obtained using the systematics of charge distribution in low and medium energy fission. The mass distribution for complete fusion fission is broad, Gaussian whereas it is asymmetric for transfer induced fission. The evaporation residue cross sections of targetlike nuclei formed in 232Th(11B, 10Be)233Pa reaction were also measured. The measured evaporation residue cross sections and the decay probabilities of targetlike nucleus 233Pa, calculated by the PACE2 code have been used to estimate the proton transfer fission cross sections which were found to be negligible compared to the total transfer cross section for all the projectile energies used. The transfer fission cross section is dominated by alpha transfer fission as inferred by measured forward to backward ratios for several fission products as well as Qgg systematics for the probable transfer reactions. The proportion of transfer fission cross section to the total fission cross section was 15, 17, and 22 % at projectile energies of 72, 60, and 55 MeV, respectively.

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

1999-06-01

218

Comparative Functional Genomics of the Fission Yeasts  

PubMed Central

The fission yeast clade, comprising Schizosaccharomyces pombe, S. octosporus, S. cryophilus and S. japonicus, occupies the basal branch of Ascomycete fungi and is an important model of eukaryote biology. A comparative annotation of these genomes identified a near extinction of transposons and the associated innovation of transposon-free centromeres. Expression analysis established that meiotic genes are subject to antisense transcription during vegetative growth, suggesting a mechanism for their tight regulation. In addition, trans-acting regulators control new genes within the context of expanded functional modules for meiosis and stress response. Differences in gene content and regulation also explain why, unlike the Saccharomycotina, fission yeasts cannot use ethanol as a primary carbon source. These analyses elucidate the genome structure and gene regulation of fission yeast and provide tools for investigation across the Schizosaccharomyces clade.

Rhind, Nicholas; Chen, Zehua; Yassour, Moran; Thompson, Dawn A; Haas, Brian J; Habib, Naomi; Wapinski, Ilan; Roy, Sushmita; Lin, Michael F.; Heiman, David I; Young, Sarah K; Furuya, Kanji; Guo, Yabin; Pidoux, Alison; Chen, Huei Mei; Robbertse, Barbara; Goldberg, Jonathan M.; Aoki, Keita; Bayne, Elizabeth H.; Berlin, Aaron M; Desjardins, Christopher A.; Dobbs, Edward; Dukaj, Livio; Fan, Lin; FitzGerald, Michael G; French, Courtney; Gujja, Sharvari; Hansen, Klavs; Keifenheim, Dan; Levin, Joshua Z.; Mosher, Rebecca A.; Muller, Carolin A.; Pfiffner, Jenna; Priest, Margaret; Russ, Carsten; Smialowska, Agata; Swoboda, Peter; Sykes, Sean M; Vaughn, Matthew; Vengrova, Sonya; Yoder, Ryan; Zeng, Qiandong; Allshire, Robin; Baulcombe, David; Birren, Bruce W.; Brown, William; Ekwall, Karl; Kellis, Manolis; Leatherwood, Janet; Levin, Henry; Margalit, Hanah; Martienssen, Rob; Nieduszynski, Conrad A.; Spatafora, Joseph W.; Friedman, Nir; Dalgaard, Jacob Z.; Baumann, Peter; Niki, Hironori; Regev, Aviv; Nusbaum, Chad

2011-01-01

219

Landau-Zener effect in fission  

SciTech Connect

A model that takes into account the Landau-Zener promotion mechanism during fission was developed recently. The structures observed in the subthreshold neutron-induced fission of {sup 232}Th are investigated employing this model. Theoretical single-particle excitations of a phenomenological two-humped barrier are determined by solving a system of coupled differential equations for the motion along the optimal fission path. A rather good agreement with experimental data is obtained using a small number of independent parameters. It is predicted that the structure at 1.4 and 1.6 MeV is mainly dominated by a spin 3/2 partial cross section with a small admixture of spin 1/2, while the structure at 1.7 MeV is given by a large partial cross section of spin 5/2.

Mirea, M.; Tassan-Got, L.; Stephan, C.; Bacri, C. O.; Bobulescu, R. C. [Horia Hulubei National Institute for Physics and Nuclear Engineering, 077125 Bucharest (Romania); Institute de Physique Nucleaire, F-91406 Orsay Cedex (France); Faculty of Physics, P.O. Box MG-11, Bucharest (Romania)

2007-12-15

220

Energy partition in low energy fission  

SciTech Connect

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 other 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.

Mirea, M. [Horia Hulubei National Institute for Physics and Nuclear Engineering, RO-077125 Bucharest (Romania)

2011-05-15

221

?-delayed fission and ? decay of 178Tl  

NASA Astrophysics Data System (ADS)

A detailed nuclear-decay spectroscopy study of the neutron-deficient isotope 178Tl has been performed using the highly selective Resonance Ionization Laser Ion Source and ISOLDE mass separator (CERN), which allowed a unique isobarically pure beam of 178Tl to be produced. The first identification of the ?-delayed fission of this isotope was made and its probability P?DF(178Tl)=0.15(6)% was determined. An asymmetric fission fragment mass distribution of the daughter isotope 178Hg (populated by the ? decay of 178Tl) was deduced based on the measured fission fragment energies. The fine-structure ?-decay pattern of 178Tl allowed the low-energy states in the daughter nucleus 174Au to be studied.

Liberati, V.; Andreyev, A. N.; Antalic, S.; Barzakh, A.; Cocolios, T. E.; Elseviers, J.; Fedorov, D.; Fedoseeev, V. N.; Huyse, M.; Joss, D. T.; Kalaninová, Z.; Köster, U.; Lane, J. F. W.; Marsh, B.; Mengoni, D.; Molkanov, P.; Nishio, K.; Page, R. D.; Patronis, N.; Pauwels, D.; Radulov, D.; Seliverstov, M.; Sjödin, M.; Tsekhanovich, I.; Van den Bergh, P.; Van Duppen, P.; Venhart, M.; Veselský, M.

2013-10-01

222

Fission-fragment energy deposition in argon  

SciTech Connect

The gas-dynamic response of argon to fission-fragment energy deposition is simulated, for the first time explicitly including the coupling between the gas density, which is spatially and temporally varying, and the power density. In simulations of three experiments with different initial fill pressures of argon, good agreement was found between calculated and observed pressure rises, after the experimental pressure rise data from one case were used as a calibration. However, in each case, the calculated thermal energy deposition corresponding to the experimental pressure data was about half the fission-fragment kinetic energy release into the gas predicted by neutron and fission-fragment transport calculations. Also, the experimental pressure data exhibited a decay not seen in the simulations, which did not incorporate an energy-loss mechanism.

Torczynski, J.R.; Gross, R.J.; Hays, G.N.; Harms, G.A.; Neal, D.R.; McArthur, D.A.; Alford, W.J.

1989-03-01

223

Prompt fission neutron emission: Problems and challenges  

NASA Astrophysics Data System (ADS)

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.

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

2013-12-01

224

Lunar surface fission power supplies: Radiation issues  

SciTech Connect

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.

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

1994-07-01

225

Heavy-Ion-Induced Fission in the Rare-Earth Region and the Statistical Model.  

National Technical Information Service (NTIS)

Two separate aspects of heavy-ion-induced fission in the rare-earth region are considered. First, fission excitation functions and their relationship to fission barriers are considered. Second, results on neutron emission associated with fission are brief...

F. Plasil J. R. Beene B. Cheynis R. L. Ferguson F. E. Obenshain

1982-01-01

226

Low-mass fission detector for the fission neutron spectrum measurement  

SciTech Connect

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.

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

2010-10-20

227

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

228

Apatite fission-track dating of fault-related rocks along the Nojima and Kusumoto faults and its tectonic significance  

NASA Astrophysics Data System (ADS)

The tectonic history of the Nojima fault, a ~10 km-long active fault whose movement caused the disastrous 1995 Kobe earthquake, was studied by the apatite fission-track (AFT) dating method. AFT ages of 63-83 Ma from a thermally undisturbed uplifted block indicate relatively minor uplift since ~65 Ma with an estimated total exhumation of ~3.6 km assuming a geothermal gradient of 25°C/km. AFT ages of 44-54 Ma and the nature of the track length distribution from fault-related rocks indicate that fault-related hydrothermal minerals, such as laumontite and chlorite, and foliated cataclasite were formed by ancient fault activity that occurred before ~44 Ma. It is inferred that the Quaternary fault activity of the Nojima fault is a relatively major phase in the entire tectonic history of the Nojima fault.

Ito, Hisatoshi

2004-11-01

229

Three's company: The fission yeast actin cytoskeleton  

PubMed Central

How the actin cytoskeleton assembles into different structures to drive diverse cellular processes is a fundamental cell biological question. In addition to orchestrating the appropriate combination of regulators and actin-binding proteins, different actin-based structures must insulate themselves from one another to maintain specificity within a crowded cytoplasm. Actin specification is particularly vexing in complex eukaryotes where a multitude of protein isoforms and actin structures operate within the same cell. Fission yeast Schizosaccharomyces pombe possesses a single actin isoform that functions in three distinct structures throughout the cell cycle. In this review, we explore recent studies in fission yeast that help unravel how different actin structures operate in cells.

Kovar, David R.; Sirotkin, Vladimir; Lord, Matthew

2010-01-01

230

Understanding cytokinesis: lessons from fission yeast  

PubMed Central

For decades after the discovery that a contractile ring made of actin filaments and myosin II produces the force to constrict the cleavage furrow of animal cells, the complexity of cytokinesis has slowed progress in understanding the mechanism. Mechanistic insights, however, have been obtained by genetic, biochemical, microscopic and mathematical modelling approaches in the fission yeast Schizosaccharomyces pombe. Many features that have been identified in fission yeast are probably shared with animal cells, as both inherited many cytokinesis genes from their common ancestor about one billion years ago.

Pollard, Thomas D.; Wu, Jian-Qiu

2010-01-01

231

Cross section for 246Cm subbarrier fission  

NASA Astrophysics Data System (ADS)

The cross section for 246Cm fission induced by neutrons of energy in the range 0.1 eV-20 keV was measured by the neutron lead slowing-down spectrometer (LSDS-100) of the Institute for Nuclear Research (INR, Russian Academy of Sciences, Moscow). The parameters of the resonance area and of the fission width were evaluated for several low-lying s-wave neutron resonances. The parameters of the intermediate structure in the cross section for the subbarrier fusion of 246Cm nuclei were found. The results obtained in this way were compared with available experimental data and with recommended evaluated data.

Alekseev, A. A.; Bergman, A. A.; Berlev, A. I.; Koptelov, E. A.; Samylin, B. F.; Trufanov, A. M.; Fursov, B. I.; Shorin, V. S.

2010-10-01

232

Uncertainty Quantification on Prompt Fission Neutrons Spectra  

SciTech Connect

Uncertainties in the evaluated prompt fission neutrons spectra present in ENDF/B-VII.0 are assessed in the framework of the Los Alamos model. The methodology used to quantify the uncertainties on an evaluated spectrum is introduced. We also briefly review the Los Alamos model and single out the parameters that have the largest influence on the calculated results. Using a Kalman filter, experimental data and uncertainties are introduced to constrain model parameters, and construct an evaluated covariance matrix for the prompt neutrons spectrum. Preliminary results are shown in the case of neutron-induced fission of {sup 235}U from thermal up to 15 MeV incident energies.

Talou, P. [T-16, Nuclear Physics Group, Los Alamos National Laboratory, NM 87545 (United States)], E-mail: talou@lanl.gov; Madland, D.G.; Kawano, T. [T-16, Nuclear Physics Group, Los Alamos National Laboratory, NM 87545 (United States)

2008-12-15

233

Proton-induced fission of iridium  

SciTech Connect

The isotopic distribution of rubidium produced in the proton induced fission of iridium has been measured at 68, 85, and 100 MeV incident beam energies using an on-line mass spectrometer with a surface ionization ion source. The deduced neutron multiplicities are substantially higher and show a steeper energy dependence compared to similar measurements done with heavy ion beam in this mass region and in the same range of excitation energies. This might confirm an effect of the angular momentum of the fissioning nucleus on the fragment deexcitation mechanism.

Pathak, B.P.; Lessard, L.; Nikkinen, L.; Lee, J.K.P.

1982-05-01

234

Soliton fission management by dispersion oscillating fiber.  

PubMed

We report the experimental observation of the fission of picosecond solitons in a fiber with sine-wave variation of the core diameter along the longitudinal direction of propagation. The experimental pulse dynamics is reproduced by numerical simulations. The fission of high-intensity solitons caused by both the variation of the fiber dispersion and stimulated Raman scattering is demonstrated. The number of output pulses and their frequencies can be managed by periodical modulation of the fiber dispersion even under the strong effect of the Raman scattering. PMID:19550919

Sysoliatin, Alexej A; Senatorov, Andrew K; Konyukhov, Andrey I; Melnikov, Leonid A; Stasyuk, Vladimir A

2007-12-10

235

Dynamic fission instability of dissipative protoplanets  

NASA Technical Reports Server (NTRS)

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.

Boss, A. P.; Mizuno, H.

1985-01-01

236

Angular Momentum Distribution of Fission Fragments  

NASA Astrophysics Data System (ADS)

Latest generation fission experiments provide an excellent testing ground for theoretical models. In this contribution we compare the measurements obtained with the DANCE calorimeter at LANSCE with our full-scale simulation of the primary fragment de-excitation, using the recently developed CGMF code, based on a Monte-Carlo implementation of the Hauser-Feshbach theoretical model. We compute the isomeric ratios as a function of the initial angular momentum of the fission fragments. Comparison with the available experimental data allows us to determine the initial spin distribution. Finally, we study the sensitivity to the discrete spectra input.

Stetcu, I.; Talou, P.; Kawano, T.; Jandel, M.

2014-04-01

237

Fission decay in intermediate heavy ion reactions  

SciTech Connect

Results are presented on cross sections, parallel and perpendicular momentum transfers, charge loss and velocity systematics for fission following reactions of Fe and Nb projectiles at 50--100 MeV/A on targets of Ta, Au, and Th. The results at 100 MeV/A are compared to a detailed multistage deexcitation model. The initial collision is modeled with an intranuclear cascade. The resultant excited target residues then undergo a fast preequilibrium decay stage followed by a statistical decay involving nucleon evaporation and fission. Results from this modeling are in reasonable agreement with experimental data. 14 refs., 11 figs.

Britt, H.C.

1990-10-03

238

Dynamic fission instability of dissipative protoplanets  

NASA Astrophysics Data System (ADS)

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.

Boss, A. P.; Mizuno, H.

1985-07-01

239

Laser Spectroscopy of Cooled Zirconium Fission Fragments  

NASA Astrophysics Data System (ADS)

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.

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

2002-08-01

240

Distribution of Independent Fission-Product Yields to Isomeric States.  

National Technical Information Service (NTIS)

A simple one-parameter model is presented for calculating the distribution of independent yield strength between ground and isomeric states of primary fission products formed by neutron-induced fission of actinide nuclei. Yield branching ratios are calcul...

D. G. Madland T. R. England

1976-01-01

241

Space Fission Propulsion Testing and Development Progress, Phase 1.  

National Technical Information Service (NTIS)

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 perfo...

M. VanDyke M. Houts K. Pedersen T. Godfroy R. Dickens D. Poston B. Reid P. Salvail P. Ring

2001-01-01

242

Fission-gas release from uranium nitride at high fission rate density  

NASA Technical Reports Server (NTRS)

A sweep gas facility has been used to measure the release rates of radioactive fission gases from small UN specimens irradiated to 8-percent burnup at high fission-rate densities. The measured release rates have been correlated with an equation whose terms correspond to direct recoil release, fission-enhanced diffusion, and atomic diffusion (a function of temperature). Release rates were found to increase linearly with burnups between 1.5 and 8 percent. Pore migration was observed after operation at 1550 K to over 6 percent burnup.

Weinstein, M. B.; Kirchgessner, T. A.; Tambling, T. N.

1973-01-01

243

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

NASA Astrophysics Data System (ADS)

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.

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

244

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

NASA Astrophysics Data System (ADS)

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.

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

245

An aminostratigraphy for the British Quaternary based on Bithynia opercula  

PubMed Central

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.

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

246

Quaternary geology and waste disposal in South Norfolk, England  

NASA Astrophysics Data System (ADS)

South Norfolk is dominated by the till plain of the Anglian Glaciation in eastern England, and therefore there are very few disused gravel pits and quarries suitable for the landfilling of municipal waste. Consequently, in May 1991, Norfolk County Council applied for planning permission to develop an above ground or 'landraise' waste disposal site at a disused U.S. World War II Airfield at Hardwick in South Norfolk. The proposal involved excavating a pit 2-4 m deep into the Lowestoft Till and overfilling it to create a hill of waste up to 10 m above the existing till plain. In general, leachate containment was to be achieved by utilising the relatively low permeability till on the floor of the site, but with reworking of the till around the site perimeter because of sand lenses in the upper part of the till. This paper examines three aspects of the proposal and the wider issues relating to Quaternary geology and waste disposal planning in South Norfolk: (i) the suitability of the till as a natural leachate containment system; (ii) the appropriateness of the landraise landform; and (iii) alternative sites. A Public Inquiry into the proposals was held in January/February 1993 and notification of refusal of planning permission was published in August 1993. Among the grounds for refusal were an inadequate knowledge of the site's geology and hydrogeology and the availability of alternative sites. The paper concludes by stressing that a knowledge of Quaternary geology is crucial to both the planning and design of landfill sites in areas of glacial/Quaternary sediments.

Gray, J. M.

247

Multiple sources of Quaternary tephra layers in the Mariana Trough  

Microsoft Academic Search

Tephra layers in Quaternary sediments (<1 Ma) in the central Mariana Trough contain three different series of glass shards: (1) low-K basaltic to basaltic-andesitic series (LKB: SiO2 = 47.3–53.6 wt.%; K2O = 0.2–0.8 wt.%); (2) medium-to high-K basaltic to dacitic series (HKS: SiO2 = 47.6–70.9 wt.%; K2O = 0.8–3.2 wt.%); and (3) low-K dacitic to rhyolitic series (LKDR: SiO2 =

S. M. Straub

1997-01-01

248

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.

249

Cyclic explosive activity of the Iceland plume in the quaternary  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

250

Strontium isotopes in Quaternary basalts of southeastern California  

USGS Publications Warehouse

Strontium isotopic variations (87Sr/86Sr of 0.7029 to 0.7052) in Quaternary basalts of southeastern California, USA, are not readily explained by assimilation of crustal material similar to that contained as xenoliths in the basalt. Isotopic differences between chrome diopside (0.7016) and olivine (0.7087) from a lherzolite xenolith suggest that the isotopic variations in the basalts may be inherited from the source regions or modified by the upper parts of the mantle that were traversed by the lavas. ?? 1970.

Peterman, Z. E.; Carmichael, I. S. E.; Smith, A. L.

1970-01-01

251

Arctic-alpine blockfields in northern Sweden: Quaternary not Neogene  

NASA Astrophysics Data System (ADS)

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.

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

2014-02-01

252

40Ar\\/39Ar dating of Quaternary feldspar: Examples from the Taupo Volcanic Zone, New Zealand  

Microsoft Academic Search

Using a continuous laser and resistance furnace, we have measured ages on Quaternary plagioclase with an absolute precision of about ±30 ka and on Quaternary sanidine with a relative precision of better than 1%. Such precision was achieved by using low-temperature heating steps to remove much of the nonradiogenic argon contamination. Plagioclase is one of the most common mineral phases

M. S. Pringle; M. McWilliams; B. F. Houghton; M. A. Lanphere; C. J. N. Wilson

1992-01-01

253

Long-term tree populations in northwest Greece through multiple Quaternary climatic cycles  

Microsoft Academic Search

THE emergent view of Quaternary cold stage European landscapes dominated by open vegetation communities has led to the concept that tree populations occurred only in restricted sites (refugia) in southern Europe1-5, although there is still considerable uncertainty over the precise location and extent of such populations. Trees respond to Quaternary climatic change by spreading from refugia during interglacials, but at

P. C. Tzedakis

1993-01-01

254

LATE-QUATERNARY VEGETATION DYNAMICS IN NORTH AMERICA: SCALING FROM TAXA TO BIOMES  

Microsoft Academic Search

This paper integrates recent efforts to map the distribution of biomes for the late Quaternary with the detailed evidence that plant species have responded individual- istically to climate change at millennial timescales. Using a fossil-pollen data set of over 700 sites, we review late-Quaternary vegetation history in northern and eastern North America across levels of ecological organization from individual taxa

John W. Williams; Bryan N. Shuman; Thompson Webb; Patrick J. Bartlein; Phillip L. Leduc

2004-01-01

255

Late Quaternary sea-level highstands in the Tasman Sea: evidence from Lord Howe Island  

Microsoft Academic Search

Lord Howe Island, situated 600 km east of Australia, provides a unique opportunity to evaluate Late Quaternary highstands of sea level in the Tasman Sea. The mid-ocean island, which is the site of the southernmost coral reef, is composed of basalts of late Tertiary age, and calcarenites derived from bioclastic reefal carbonates. Both erosional and depositional evidence of Late Quaternary

C. D. Woodroffe; C. V. Murray-Wallace; E. A. Bryant; B. Brooke; H. Heijnis; D. M. Price

1995-01-01

256

Late Quaternary slip rates across the central Tien Shan, Kyrgyzstan, central Asia  

Microsoft Academic Search

(1) Slip rates across active faults and folds show that late Quaternary faulting is distributed across the central Tien Shan, not concentrated at its margins. Nearly every intermontane basin contains Neogene and Quaternary syntectonic strata deformed by Holocene north-south shortening on thrust or reverse faults. In a region that spans two thirds of the north-south width of the central Tien

Stephen C. Thompson; Ray J. Weldon; Charles M. Rubin; Kanatbek Abdrakhmatov; Peter Molnar; Glenn W. Berger

2002-01-01

257

Catalytic enantioselective nazarov cyclization: construction of vicinal all-carbon-atom quaternary stereocenters.  

PubMed

The diastereoselective asymmetric synthesis of vicinal all-carbon-atom quaternary stereocenters is a challenging problem in organic synthesis for which only few solutions have been described. A catalytic asymmetric Nazarov cyclization of fully substituted dienones that provides cyclopentenone derivatives with vicinal quaternary stereocenters in high optical purity and as single diastereoisomers is now reported. PMID:24838340

Jolit, Anais; Walleser, Patrick M; Yap, Glenn P A; Tius, Marcus A

2014-06-10

258

Recent Progress on the Stereoselective Synthesis of Cyclic Quaternary ?-Amino Acids  

PubMed Central

The most recent papers describing the stereoselective synthesis of cyclic quaternary ?-amino acids are collected in this review. The diverse synthetic approaches are classified according to the size of the ring and taking into account the bond that is formed to complete the quaternary skeleton.

Cativiela, Carlos; Ordonez, Mario

2010-01-01

259

A study of Quaternary structures in the Qom region, West Central Iran  

Microsoft Academic Search

West Central Iran comprises numerous Quaternary faults. Having either strike-slip or thrust mechanisms, these faults are potentially active and therefore capable of creating destructive earthquakes. In this paper, we use satellite images as well as field trips to identify these active faults in the Qom region. The Qom and Indes faults are the main NW-trending faults along which a Quaternary

A. Babaahmadi; H. Safaei; A. Yassaghi; H. Vafa; A. Naeimi; S. Madanipour; M. Ahmadi

2010-01-01

260

A Preliminary Geomorphic Overview of Late Quaternary Glacier Fluctuations in the South Shetland Islands, West Antarctica  

Microsoft Academic Search

?The timing and extent of glaciations during the Late Quaternary in the South Shetland Islands, West Antarctica were defined using field mapping, geomorphic analysis and radiocarbon dating. Landforms of glacial erosion and deposition, in particular subglacial meltwater channel erosion, suggest that at least three glaciations occurred during the late Quaternary within the study region. During the global LGM, glacial troughs

Yeong Bae Seong; Hyoun Soo Lim; Ho Il Yoon; Yong Il Lee; Yeadong Kim; Lewis A. Owen

2006-01-01

261

Characterisation of quaternary mixtures by the apparent content curves method: identification of tocopherols in vegetable oils  

Microsoft Academic Search

A procedure for identification of the compounds in quaternary mixtures has been developed. The proposed procedure is based on the apparent content curves method. From these curves and using the Q parameter, work conditions are selected and quaternary mixtures treated as \\

A. R. Maurí-Aucejo; M. Llobat-Estellés; R. Marín-Saez

2003-01-01

262

The first enzymatic resolution of quaternary ??-acetoxy ?,?-unsaturated cyclohexenones and cyclopentenones  

Microsoft Academic Search

The enantioselective resolution of various quaternary ??-acetoxy ?,?-unsaturated cyclohexenones and cyclopentenones was performed with the commercially available enzyme CCL in pH=8.0 phosphate buffer. Various parameters that would affect the enantioselectivities were tested and the best enzymatic resolution conditions were found to afford the enantiomerically enriched quaternary acetoxylated substrates with high ee varying between 36% and 99%.

Cihangir Tanyeli; Fazilet Devrim Özdemirhan; Çi?dem ?yigün

2005-01-01

263

Fission measurements with PPAC detectors using a coincidence technique  

SciTech Connect

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)

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

264

Analysis of fissionable pellets for inertial confinement fusion  

Microsoft Academic Search

A study consisting of a number of calculations has been performed and is presented investigating the neutronics and hydrodynamics of a fission-fusion pellet system with an arbitrary driver. A fission driven fusion process, where the fission reaction is the primary source of energy for the fusion reaction, has been regarded as a promising technique for reducing the energy delivery requirements

H. Makowitz; J. Tsang

1978-01-01

265

Fissile and fusile breeding in the thorium fusion fission hybrid  

Microsoft Academic Search

The thorium fuel cycle fissile and fusile breeding in a molten salt and a solid fuel blanket for a system consisting of fusion fuel factories coupled to fission satellites burners, is considered. The use of the thorium cycle in a fusion fission hybrid could bypass the stage of fourth generation fission breeder reactors in that the energy multiplication in the

Magdi Ragheb; Ayman Nour Eldin

2010-01-01

266

Mass distribution in 19F induced fission of 232Th  

NASA Astrophysics Data System (ADS)

Formation cross sections of several fission products have been determined using the recoil catcher technique followed by ?-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 have been obtained using the systematics of charge distribution in low and medium energy fission. Mass distribution for complete fusion fission is broad Gaussian whereas it is asymmetric for transfer induced fission. At 95 MeV the transfer fission constitutes about 28% of total fission cross section while at 112 MeV it is about 14%, showing that the transfer fission fraction decreases with increasing projectile energy across the barrier. The evaporation residue cross sections of the targetlike nucleus formed in the 232Th (19F, 18O) 233Pa reaction were also measured. The evaporation residue cross sections and the calculated decay probabilities of the targetlike nucleus 233Pa by PACE2 have been used to estimate the fraction of proton and ? transfer fission in the total transfer fission cross section.

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

1996-02-01

267

Enabling the Use of Space Fission Propulsion Systems  

SciTech Connect

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.

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

268

Factors affecting use of fission foils as dosimetry sensors  

SciTech Connect

Fission foils are commonly used as dosimetry sensors. They play a very important role in neutron spectrum determinations. This paper provides a combination of experimental measurements and calculations to quantify the importance and synergy of several factors that affect the fission response of a dosimeter. Only when these effects are properly treated can fission dosimeters be used with sufficient fidelity.

Griffin, P.J.; Vehar, D.W.; Kelly, J.G.; Holm, C.V.

1996-12-31

269

Calculations on fission gas behaviour in the high burnup structure  

Microsoft Academic Search

The behaviour of fission gas in high burnup fuel during steady-state and transient conditions is of special interest for safety reasons. Despite this, mechanistic models that reflect the fission gas transport processes and reliably predict the evolution of the remaining fission gas in the high burnup structure (HBS) are largely missing today. We start to address this problem by developing

P. Blair; A. Romano; Ch. Hellwig; R. Chawla

2006-01-01

270

Late Quaternary geomorphology and soils in Crater Flat, Yucca mountain area, southern Nevada  

SciTech Connect

Crater Flat is an alluvium-filled structural basin on the west side of Yucca Mountain, Nevada, which is under consideration for a high-level nuclear waste repository. North-trending, late Quaternary faults offset alluvium in Crater Flat both along the canyons of the western flanks of Yucca Mountain and out on the piedmont slope. We believe the initial lack of young offsets at Yucca Mountain was in part due to unrecognized late Quaternary stratigraphy. We hypothesize that alluviation in the Yucca Mountain region was more active during the late Quaternary than previously thought. Several techniques were tried to test this hypothesis. Results are compared with previous soils and surface-exposure dating studies, and correlated to stratigraphy of other late Quaternary units in the southern Nevada, Death Valley, and Mojave Desert areas, and provide new stratigraphic data relevant to understanding climatic-alluvial processes in the Basin and Range Province during the late Quaternary. 76 refs., 7 figs., 6 tabs.

Peterson, F.F.; Bell, J.W.; Ramelli, A.R. [Univ. of Nevada, Reno, NV (United States)] [Univ. of Nevada, Reno, NV (United States); Dorn, R.I. [Arizona State Univ., Tempe, AZ (United States)] [Arizona State Univ., Tempe, AZ (United States); Ku, T.L. [Univ. of Southern California, Los Angeles, CA (United States)] [Univ. of Southern California, Los Angeles, CA (United States)

1995-04-01

271

Search for other natural fission reactors  

Microsoft Academic Search

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

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

1977-01-01

272

Formation of asteroid pairs by rotational fission.  

PubMed

Pairs of asteroids sharing similar heliocentric orbits, but not bound together, were found recently. Backward integrations of their orbits indicated that they separated gently with low relative velocities, but did not provide additional insight into their formation mechanism. A previously hypothesized rotational fission process may explain their formation-critical predictions are that the mass ratios are less than about 0.2 and, as the mass ratio approaches this upper limit, the spin period of the larger body becomes long. Here we report photometric observations of a sample of asteroid pairs, revealing that the primaries of pairs with mass ratios much less than 0.2 rotate rapidly, near their critical fission frequency. As the mass ratio approaches 0.2, the primary period grows long. This occurs as the total energy of the system approaches zero, requiring the asteroid pair to extract an increasing fraction of energy from the primary's spin in order to escape. We do not find asteroid pairs with mass ratios larger than 0.2. Rotationally fissioned systems beyond this limit have insufficient energy to disrupt. We conclude that asteroid pairs are formed by the rotational fission of a parent asteroid into a proto-binary system, which subsequently disrupts under its own internal system dynamics soon after formation. PMID:20740010

Pravec, P; Vokrouhlický, D; Polishook, D; Scheeres, D J; Harris, A W; Galád, A; Vaduvescu, O; Pozo, F; Barr, A; Longa, P; Vachier, F; Colas, F; Pray, D P; Pollock, J; Reichart, D; Ivarsen, K; Haislip, J; Lacluyze, A; Kusnirák, P; Henych, T; Marchis, F; Macomber, B; Jacobson, S A; Krugly, Yu N; Sergeev, A V; Leroy, A

2010-08-26

273

Observe an Animation of Nuclear Fission  

NSDL National Science Digital Library

Teachers could use this resource with students to help them visualize the process of nuclear fission. Students could be encouraged to use the movie control buttons to view and review the animation, pausing whenever necessary. Although this resource was designed to supplement a specific Earth science textbook, it can be used without that text.

2010-01-01

274

Fission Detection Using the Associated Particle Technique  

SciTech Connect

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.

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

2008-09-18

275

Liquid uranium alloy-helium fission reactor  

DOEpatents

This invention teaches a nuclear fission reactor having a core vessel and at least one tandem heat exchanger vessel coupled therewith across upper and lower passages to define a closed flow loop. Nuclear fuel such as a uranium alloy in its liquid phase fills these vessels and flow passages. Solid control elements in the reactor core vessel are adapted to be adjusted relative to one another to control fission reaction of the liquid fuel therein. Moderator elements in the other vessel and flow passages preclude fission reaction therein. An inert gas such as helium is bubbled upwardly through the heat exchanger vessel operable to move the liquid fuel upwardly therein and unidirectionally around the closed loop and downwardly through the core vessel. This helium gas is further directed to heat conversion means outside of the reactor vessels to utilize the heat from the fission reaction to generate useful output. The nuclear fuel operates in the 1200.degree.-1800.degree. C. range, and even higher to 2500.degree. C., limited only by the thermal effectiveness of the structural materials, increasing the efficiency of power generation from the normal 30-35% with 300.degree.-500.degree. C. upper limit temperature to 50-65%. Irradiation of the circulating liquid fuel, as contrasted to only localized irradiation of a solid fuel, provides improved fuel utilization.

Minkov, Vladimir (Skokie, IL) [Skokie, IL

1986-01-01

276

Plutonium to Uranium Fission Ratio Measurements.  

National Technical Information Service (NTIS)

The measurement of the ratio of plutonium to uranium fissions has for some years been used as a method of characterizing the thermal spectrum in reactor lattices. This report describes the method of analysis of this type of measurement which has been deve...

R. H. Waterson

1971-01-01

277

Transfer-induced fission of superheavy nuclei  

NASA Astrophysics Data System (ADS)

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 Ca48+Cm244,246,248 at energies near the corresponding Coulomb barriers. The predicted cross sections are found to be measurable with the detection of three-body final states.

Adamian, G. G.; Antonenko, N. V.; Sargsyan, V. V.; Scheid, W.; Zubov, A. S.

2010-07-01

278

Brownian Shape Dynamics in Nuclear Fission  

NASA Astrophysics Data System (ADS)

It was recently found that remarkably accurate fission-fragment mass distributions can be obtained by treating the nuclear shape evolution as a Metropolis walk on previously calculated five-dimensional potential-energy surfaces; this novel method is briefly reviewed here.

Randrup, Jørgen; Möller, Peter

2014-09-01

279

Fission Energy and Other Sources of Energy  

ERIC Educational Resources Information Center

Discusses different forms of energy sources and basic reasons for the opposition to the use of atomic energy. Suggests that research efforts should also be aimed toward the fission technology to make it acceptable besides major research studies conducted in the development of alternative energy sources. (CC)

Alfven, Hannes

1974-01-01

280

Studies of fission hindrance in hot nuclei  

SciTech Connect

The study of dissipation in hot nuclear systems is a subject of great current interest. Different experimental techniques and observables have recently been utilized which axe sensitive to the dissipation in large-scale shape rearrangements, such as those encountered in heavy-ion fusion, fission and quasifission reactions. To study the dynamical shape evolution of hot nuclear systems it is necessary to measure properties (or processes) that are sensitive to the time-scale on which these shape changes occur. Several methods, such as the emission of prescission particles (n, p and {alpha}) and {gamma}-rays, have been used to study the fission time-scale in relation to these (well known) decay processes. Recently it has also been pointed out that measurements of the evaporation residue cross section, which are very sensitive to the competition between particle emission and fission, probe the fission time-scale. This paper will present recent studies of the evaporation residue cross section in the {sup 32}S+{sup 184} system carried out at the ATLAS Fragment Mass Analyzer, including the methods for obtaining absolute cross sections.

Back, B.B.; Blumenthal, D.J.; Davids, C.N. [and others

1995-06-01

281

Understanding cytokinesis: lessons from fission yeast  

Microsoft Academic Search

For decades after the discovery that a contractile ring made of actin filaments and myosin II produces the force to constrict the cleavage furrow of animal cells, the complexity of cytokinesis has slowed progress in understanding the mechanism. Mechanistic insights, however, have been obtained by genetic, biochemical, microscopic and mathematical modelling approaches in the fission yeast Schizosaccharomyces pombe. Many features

Jian-Qiu Wu; Thomas D. Pollard

2010-01-01

282

Transfer-induced fission of superheavy nuclei  

SciTech Connect

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.

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

283

Spontaneous Fission of the Heaviest Elements.  

National Technical Information Service (NTIS)

Although spontaneous fission was discovered in (238)U in 1940, detailed studies of the process were first made possible in the 1960's with the availability of milligram quantities of (252)Cf. The advent of solid-state detectors made it possible to perform...

D. C. Hoffman

1989-01-01

284

Exposure Rates from Experimentally Fractionated Fission Products.  

National Technical Information Service (NTIS)

Exposure rates, at three feet above a uniformly contaminated smooth plane, were calculated from recent experimentally measured gamma-ray spectra of fractionated products of thermal-neutron fission of 235U. The fractionation had been carried out by very ea...

L. R. Bunney D. Sam

1971-01-01

285

After Apollo: Fission Origin of the Moon  

ERIC Educational Resources Information Center

Presents current ideas about the fission process of the Moon, including loss of mass. Saturnian rings, center of the Moon, binary stars, and uniformitarianism. Indicates that planetary formation may be best explained as a destructive, rather than a constructive process. (CC)

O'Keefe, John A.

1973-01-01

286

Possible mechanism of parity nonconservation in fission  

SciTech Connect

The P-odd asymmetry in the angular distribution of fragments produced in fission of a polarized nucleus is discussed. A mechanism is proposed in which the effect arises as the result of mixing of the rotational states of a cold highly deformed nucleus. Experiments which are critical with respect to this mechanism are discussed.

Sushkov, O.P.; Flambaum, V.V.

1980-01-01

287

Mechanism for parity violation in fission  

SciTech Connect

Parity violation in the fission of nuclei by thermal neutrons is studied. It is shown that the effect is due to the mixing of rotational states of opposite parity of the cold, strongly deformed nucleus. This mixing appears as the result of the weak interaction at the compound-nucleus stage.

Sushkov, O.P.; Flambaum, V.V.

1981-01-01

288

A fission-fragment-sensitive target for X-ray spectroscopy in neutron-induced fission  

Microsoft Academic Search

A fission-fragment-sensitive detector built for low-energy photon spectroscopy applications at the WNR “white” neutron source at Los Alamos is described. The detector consists of eight layers of thin photovoltaic cells, onto which 1mg\\/cm2 of pure 238U is deposited. The detector serves as an active target to select fission events from background and other reaction channels. The fairly small thickness of

T. Ethvignot; T. Granier; L. Giot; P. Casoli; R. O. Nelson

2002-01-01

289

Fission barrier properties, resonance fluctuations and isomer fission cross-sections.  

SciTech Connect

Although the main picture of fission bamer physics was established some time ago many of the details still have to be settled. Consequently, the application to evaluation of crosssections of unmeasurable or exotic nuclides and their excited states is still in its early stages. In this paper I consider some of these details and explore the possibility of quantitative estimation of fission cross-sections

Lynn, J. E. (J. Eric); Hayes, A. C. (Anna C.)

2002-11-27

290

Angular momentum of fission fragments in low energy fission of actinides  

NASA Astrophysics Data System (ADS)

Independent isomeric yield ratios (IYR) of 128Sb, 130Sb, 132Sb, 131Te, 133Te, 132I, 134I, 136I, 135Xe, and 138Cs have been determined in fast neutron induced fission of 232Th, 238U, 240Pu, and 244Cm as well as in thermal neutron induced fission of 232U and 238Pu using radiochemical and offline ?-ray spectrometric techniques. From the IYR, fragment angular momenta (Jrms) have been deduced using a spin-dependent statistical model analysis. These data along with the literature data for 230Th?, 234U?, 236U?, 240Pu?, 242Pu?, 244Cm(SF), 246Cm?, 250Cf?, and 252Cf(SF) for fifteen even-Z fissioning systems show the following important features: (i) The Jrms of the odd-Z fission products are higher than those of the even-Z fission products, indicating the odd-even effect. For both the odd-Z and even-Z fission products, the Jrms increase with Z2F/AF. (ii) The Jrms of fragments with spherical 50-p and 82-n shells are lower compared to those of fragments outside the spherical shell, indicating the effect of shell closure proximity. (iii) The Jrms of the fission products increase with mass number in spite of fluctuations in shell closure proximity and odd-even effects but do not show any correlation with the neutron emission curve. (iv) In all fifteen even-Z fissioning systems from Th to Cf, the yield-weighted Jrms values show an anticorrelation with the elemental yields. (v) The odd-even fluctuation on Jrms does not change drastically from Th to Cf, unlike the proton odd-even effect (?p) which decreases significantly with the increase of Coulomb parameter (Z2F/A1/3F).

Naik, H.; Dange, S. P.; Singh, R. J.

2005-01-01

291

Yields of short-lived fission products following fast fission of U-238  

NASA Astrophysics Data System (ADS)

Fission-product yields following neutron-induced fission of 238U have been measured at the UMass Lowell 1-MW research reactor using gamma-ray spectroscopy. High- resolution gamma-ray spectra of aggregate fission products have been measured at 13 delay-time intervals ranging from 0.3 s to 4,000s after fission. A helium-jet system was used to rapidly transfer fission products from the fission chamber to a low-background counting area where they were sprayed onto a moving tape. The tape, whose speed determined the observed delay time, carried the products to a high-purity germanium detector. The use of beta-gamma coincidence reduced the background by about two orders of magnitude, and further improvement in the peak-to-background ratio was obtained by using a NaI(Tl) annulus for Compton suppression. The helium-jet system has been shown to give uniform transfer of fission products over the mass range studied. Cumulative and independent yields of fission products are calculated from the time-evolution of relative line intensities extracted from the aggregate spectra. An average of four lines per nuclide were used in this determination. Only lines showing the correct time evolution and relative intensity were used to assure there was no contamination from lines with similar energies. Measured nuclide yields are compared to those given in the ENDF/B-VI evaluation. Yields for 63 nuclides were determined, including twenty- one nuclides with halflives less than 2 s. Eleven determinations of yields were made for nuclides with isomeric states.

Campbell, Joann Marie

1997-07-01

292

Exhumation mechanisms of SE Carpathians assessed by detrital zircon fission-track thermochronology  

NASA Astrophysics Data System (ADS)

Radiometric dating of detrital minerals has been more and more used in the recent years to better understand the long-term evolution of mountain belts and their topography. Low temperature geochronology studies of European orogens such as Swiss and Western Alps, Apennines or Betics show an unusual exhumation history since the late Neogene. Most of the current research has inferred the coupling between tectonics, climate and surface processes as responsible for topographic changes. In the south-eastern part of Romanian Carpathians recent thermochronological studies revealed that up to 5 km of sediments were exhumed during the two post-collisional exhumation stages: first around 5 Ma and a second phase during Quaternary times. We aim to unravel the mechanism(s) and improve the temporal resolution controlling the exhumation by applying detrital zircon fission-track thermochronology (DZFT) to key stratigraphic layers of the foreland basin, archive of the long-term orogenic exhumation. A large data-set of DZFT ages have been obtained for samples along three river profiles perpendicular to the strike of the East Carpathian orogen. The full grain age spectrum have well defined components around 70, 100 and >134 Ma which correlates with Laramian and Austrian (in Romanian nomenclature) tectonic phases. All the youngest components (P1) of each sample are non-reset and preserve the source provenance as well as the recent exhumation history. We suggest a climatic control on the exhumation and erosion of the SE Carpathians since late Neogene time, with significant peak accelerations that are correlated in space and time with the Messinian Salinity Crisis event (~5 Ma) and with the Quaternary stages of enhanced exhumation. However, a striking feature is the presence of few thermochronological age components situated in the very close temporal proximity to the stratigraphic age which show inclusions, euhedral morphometry and zonations. They are likely derived from the Neogene volcanism situated in eastern margin of Transylvanian basin, and dated by K-Ar method as young as Quaternary up to 10.5 Ma. This has significant inferences for constraining the timing of basin connectivity within the Paratethys domains that have bordered the East Carpathians Mountains.

Trifan, C?t?lin; Andriessen, Paul; Ma?enco, Liviu

2013-04-01

293

Low Sensitivity of Listeria monocytogenes to Quaternary Ammonium Compounds  

PubMed Central

Ninety-seven epidemiologically unrelated strains of Listeria monocytogenes were investigated for their sensitivities 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 pump, and the orfA gene, a putative transcriptional repressor of mdrL. The absence of plasmids in four of the seven resistant strains and the conservation of resistance after plasmid curing suggested that the resistance genes are not plasmid borne. Moreover, PCR amplification and Southern blot hybridization experiments failed to find genes phylogenetically related to the qacA and smr genes, encoding multidrug efflux systems previously described for the genus Staphylococcus. The high association between nontypeability by phages and the loss of sensitivity to quaternary ammonium compounds are suggestive of an intrinsic resistance due to modifications in the cell wall.

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

2000-01-01

294

Geomorphology and late Quaternary of the Chaco (South America)  

NASA Astrophysics Data System (ADS)

The Chaco is a large tropical plain located in the interior of South America, consisting of parts of Argentina, Paraguay and Bolivia. It is 840,000 km 2 in area and is characterized by forests, savannas and extensive swamps, which give it a marked climatic and biogeographic identity. It encompasses five huge alluvial fans built by the major rivers which cross the region: Salado, Bermejo, Pilcomayo, Parapetí and Grande. The fans are composed of several sedimentary units, deposited during different times of the late Quaternary under diverse climates. Two fluvial terraces appear at the apex of each fan; the older one is probably late Pleistocene in age, the second was formed in postglacial times. Humid climates, such as the present one, favoured the generation of soils and stable fluvial belts; drier climates led to widespread sedimentation along small ephemeral channels and large spill-outs. During two intervals, on in the late Quaternary glacial maximum and the late Holocene dry climates occurred in the region, leading to the formation of dune fields and loess mantles.

Iriondo, Martin

1993-08-01

295

Late quaternary environments, Denali National Park and Preserve, Alaska  

USGS Publications Warehouse

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.

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

1996-01-01

296

Late Quaternary terrestrial vertebrate coprolites from New Zealand  

NASA Astrophysics Data System (ADS)

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.

Wood, Jamie R.; Wilmshurst, Janet M.

2014-08-01

297

Late Quaternary sedimentation on the North Aegean continental margin, Greece  

SciTech Connect

The late Quaternary seismic stratigraphy of the North Aegean continental shelf and adjacent basins has been interpreted from boomer and 3.5-kHz seismic profiles. Ages derived from shallow cores and offshore wells, and relative offsets on small synsedimentary faults, provide chronological control. Sea level history inferred from seismic stratigraphy correlates with the global eustatic sea level record based on oxygen isotopic curves. The present depth of the delta plain formed on the outer shelf during the late stage 6 lowstand provides a dated and originally horizontal marker for estimating rates of tectonic subsidence. Gross distribution of sediment facies is similar in both tectonically stable and active areas. The shell break formed by delta progradation, but is marked by faults in most places because of the accommodation provided by graben subsidence rates of 0.3-1.5 mm/yr. Standard sequence stratigraphic analysis can be applied to these sediments deposited during high-amplitude Quaternary sea level oscillations. High rates of subsidence result in the preservation an unusually complete record of sea level change. Major lowstand progradation is dependent on the duration, rather than the magnitude, of sea level lowstand. The long glaciations in isotopic stages 6, 12, 16, and 22 resulted in the most prominent seaward progradation on the margin. Sandy lowstand turbidite deposits formed only when there was rapid fall in sea level; otherwise sand was trapped on delta tops and silty muds were deposited in deep water.

Piper, D.J.W. (Bedford Inst. of Oceanography, Dartmouth, Nova Scotia (Canada)); Perissoratis, C. (Inst. of Geology and Mineral Research, Athens (Greece))

1991-01-01

298

Constraining the age and magnitude of uplift in the northern National Petroleum Reserve in Alaska (NPRA)-apatite fission-track analysis of samples from three wells  

USGS Publications Warehouse

A broad, post-mid-Cretaceous uplift is defined in the northern National Petroleum Reserve in Alaska (NPRA) by regional truncation of Cretaceous strata, thermal maturity patterns, and amounts of exhumation estimated from sonic logs. Apatite fission-track (AFT) analysis of samples from three wells (South Meade No. 1, Topagoruk No. 1, and Ikpikpuk No. 1) across the eastern flank of the uplift indicates Tertiary cooling followed by Quaternary heating. Results from all three wells indicate that cooling, presumably caused by uplift and erosion, started about 75-65 Ma (latest Cretaceous-earliest Tertiary) and continued through the Tertiary Period. Data from South Meade indicate more rapid cooling after about 35-15 Ma (latest Eocene-middle Miocene) followed by a significant increase in subsurface temperature during the Quaternary, probably the result of increased heat flow. Data from Topagoruk and Ikpikpuk include subtle evidence of accelerated cooling starting in the latest Eocene-middle Miocene and possible evidence of increased temperature during the Quaternary. Subsurface temperature perturbations related to the insulating effect of permafrost may have been responsible for the Quaternary temperature increase at Topagoruk and Ikpikpuk and may have been a contributing factor at South Meade. Multiple lines of geologic evidence suggest that the magnitude of exhumation resulting from uplift and erosion is 5,000-6,500 ft at South Meade, 4,000-5,500 ft at Topagoruk, and 2,500-4,000 ft at Ikpikpuk. The results from these wells help to define the broad geometry of the uplift, which increases in magnitude from less than 1,000 ft at the Colville River delta to perhaps more than 7,000 ft along the northwestern coast of NPRA, between Point Barrow and Peard Bay. Neither the origin nor the offshore extent of the uplift, west and north of the NPRA coast, have been determined.

Houseknecht, David W.; Bird, Kenneth J.; O'Sullivan, Paul

2011-01-01

299

Insights into nuclear structure and the fission process from spontaneous fission  

SciTech Connect

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.

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

1993-12-31

300

Fission track dating of kimberlitic zircons  

USGS Publications Warehouse

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.

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

1983-01-01

301

Role of the Zero-Point Corrections in Fission Dynamics  

NASA Astrophysics Data System (ADS)

The way of evaluating spontaneous fission half-lives of nuclei in a multidimensional deformation space is discussed. The cranking as well as the generator coordinate method were used to obtain the collective inertia tensor and the 'zero-point' corrections to the fission barriers. The fission probability was evaluated within the WKB approximation along the least-action trajectory to fission. The influence on the fission life-times of the dynamics in the pairing degrees of freedom as well as the effect of the higher even-multipolarity shape parameters and the role of the reflection asymmetry is examined.

Pomorski, Krzysztof

302

Fission Technology for Exploring and Utilizing the Solar System  

NASA Technical Reports Server (NTRS)

Fission technology can enable rapid, affordable access to any point in the solar system. Potential fission-based transportation options include bimodal nuclear thermal rockets, high specific energy propulsion systems, and pulsed fission propulsion systems. In-space propellant re-supply enhances the effective performance of all systems, but requires significant infrastructure development. Safe, timely, affordable utilization of first-generation space fission propulsion systems will enable the development of more advanced systems. First generation space systems will build on over 45 years of US and international space fission system technology development to minimize cost,

Houts, Mike; VanDyke, Melissa; Godfroy, Tom; Pedersen, Kevin; Martin, James; Dickens, Ricky; Salvail, Pat; Hrbub, Ivana; Schmidt, George R. (Technical Monitor)

2000-01-01

303

Fission Yield Measurements by Inductively Coupled Plasma Mass-Spectrometry  

SciTech Connect

Correct prediction of the fission products inventory in irradiated nuclear fuels is essential for accurate estimation of fuel burnup, establishing proper requirements for spent fuel transportation and storage, materials accountability and nuclear forensics. Such prediction is impossible without accurate knowledge of neutron induced fission yields. Unfortunately, the accuracy of the fission yields reported in the ENDF/B-VII.0 library is not uniform across all of the data and much of the improvement is desired for certain isotopes and fission products. We discuss our measurements of cumulative fission yields in nuclear fuels irradiated in thermal and fast reactor spectra using Inductively Coupled Plasma Mass Spectrometry.

Irina Glagolenko; Bruce Hilton; Jeffrey Giglio; Daniel Cummings; Karl Grimm; Richard McKnight

2009-11-01

304

Diabetes regulates mitochondrial biogenesis and fission in neurons  

PubMed Central

Aims Normal mitochondrial (Mt) activity is a critical component of neuronal metabolism and function. Disruption of Mt activity by altered Mt fission and fusion is the root cause of both neurodegenerative disorders and Charcot-Marie-Tooth Type 2A inherited neuropathy. The current study addressed the role of Mt fission in the pathogenesis of diabetic neuropathy (DN). Methods Mt biogenesis and fission were assayed in both in vivo and in vitro models of DN. Gene, protein, mitochondrial DNA and ultrastructural analyses were used to assess Mt biogenesis and fission. Results Our data reveal increased Mt biogenesis in dorsal root ganglion (DRG) neurons from diabetic compared to non-diabetic mice. An essential step in Mt biogenesis is Mt fission, regulated by the Mt fission protein Drp1. Evaluation of in vivo diabetic neurons indicated small, fragmented Mt, suggesting increased fission. In vitro studies reveal short-term hyperglycemic exposure increased expression of Drp1. The influence of hyperglycemia-mediated Mt fission on cellular viability was evaluated by knockdown of Drp1. Knockdown of Drp1 resulted in decreased susceptibility to hyperglycemic damage. Conclusions We propose that: 1) Mt undergo biogenesis in response to hyperglycemia, but the increased biogenesis is insufficient to accommodate the metabolic load; 2) hyperglycemia causes an excess of Mt fission, creating small, damaged mitochondria; and 3) reduction of aberrant Mt fission increases neuronal survival and indicates an important role for the fission-fusion equilibrium in the pathogenesis of DN.

Edwards, J.L.; Quattrini, A.; Lentz, S.I.; Figueroa-Romero, C.; Cerri, F.; Backus, C.; Hong, Y.; Feldman, E.L.

2014-01-01

305

A transferable model for singlet-fission kinetics.  

PubMed

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

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

306

Nuclear fission of neutron-deficient protactinium nuclides  

NASA Astrophysics Data System (ADS)

Fragment velocity, kinetic energy, mass yield, and element yield distributions in the fission of neutron-deficient Pa isotopes produced in the reactions of 16O and 18O on 209Bi have been measured at incident beam energies near and above the Coulomb barriers by the time-of-flight and radiochemical methods. An asymmetric mass-division component has been observed. Measured fission cross sections were compared with the results of statistical model calculations which take into account two fission barrier heights for symmetric and asymmetric yields. The fission barrier height deduced for the asymmetric fission is found slightly lower than that for the symmetric one. The difference between the two barrier heights in the fission of the present protactinium nuclides (N~135) is considerably smaller than that in the neutron-rich nuclide of 233Pa (N~142), indicating that the difference sensitively depends on the neutron number of the fissioning nuclide.

Nishinaka, I.; Nagame, Y.; Tsukada, K.; Ikezoe, H.; Sueki, K.; Nakahara, H.; Tanikawa, M.; Ohtsuki, T.

1997-08-01

307

A transferable model for singlet-fission kinetics  

NASA Astrophysics Data System (ADS)

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.

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

308

FISSION: A computer code for calculating fission yields and delayed-neutron yields using the model proposed by Waldo  

NASA Astrophysics Data System (ADS)

Of the many available models that describe fission yields, the one proposed by R. Waldo seems to best reproduce the total delayed neutron yeilds obtained in fission by thermal or fission spectrum neutrons. A computer code was written to calculate fission product yields and beta-delayed neutron yields using his model. A description of the model is given. A comparison of calculated fission product yields to experimental yields as well as calculations using other models for both 235U(n/sub t/,f) and 239Pu(n/sub t/,f) is included.

Kusnezov, D. F.; Henry, E. A.

1981-11-01

309

Quaternary Reorganization of North American Mid-continent Drainage Systems  

NASA Astrophysics Data System (ADS)

Identification of ancestral drainage systems in the North American mid-continent has been a topic of research and debate among geologists since the middle of the 19th Century. Over time our understanding of the significance of Quaternary glaciations in reshaping drainage patterns has grown. The ancestral Teays River, which drained large areas of the central Appalachians and flowed westward across Indiana and western Illinois, was dammed multiple times by Quaternary glaciers before finally being rerouted to the course of the modern central Ohio River. Similarly, the northward-flowing ancestral Pittsburgh River was dammed by pre-Illinoian glaciers; subsequent stream piracy converted this river system into the modern Allegheny, Monongahela and uppermost Ohio Rivers. Deposits and geomorphic features along the westward-flowing lower Wisconsin River indicate that the modern upper Mississippi River and Wisconsin River may have experienced a similar history of ice blockage, stream piracy, and radical rerouting. Coring into the Bridgeport strath terrace along the lower Wisconsin River reveals that the bedrock surface dips to the east, indicating the valley was cut by an eastward-flowing river. We believe the most likely scenario following this interpretation is that an ancestral river flowing along the modern upper Mississippi River valley made a sharp bend at Prairie du Chien, WI, and flowed eastward along the valley occupied by the modern lower Wisconsin River. This river, referred to here as the Wyalusing River, likely flowed northeastward into the Great Lakes (St. Lawrence) drainage until that path was blocked by ice advancing from the northwest. Subsequent stream piracy immediately south of the modern confluence of the Mississippi and Wisconsin Rivers rerouted these streams, converting them to the headwaters of the greater Mississippi drainage. The combined rerouting of these river systems into entirely different drainage basins necessitates significant fundamental changes to the total discharge of the St. Lawrence and Mississippi Rivers. While it is unclear if the Teays River ever flowed into the St. Lawrence drainage or developed as a westward-flowing tributary to the buried Mahomet valley in Illinois, both the ancestral Pittsburgh and Wyalusing Rivers originated as headwaters of the St. Lawrence basin before being rerouted as part of the Mississippi basin. The areas formerly drained by the Pittsburgh and Wyalusing Rivers comprise ~8% of the modern Mississippi River basin, and modern discharge from those areas represent ~14% of the mean annual discharge of the Mississippi River. The transfer of this drainage area and discharge to the Mississippi basin is mirrored by an equivalent loss from the St. Lawrence system during the Quaternary as a direct result of glacially-driven drainage system reorganization.

Carson, E. C.; Rawling, J. E., III; Attig, J. W.; Bates, B. R.

2013-12-01

310

Quaternary history and contemporary patterns in a currently expanding species  

PubMed Central

Background Quaternary climatic oscillations had dramatic effects on species evolution. In northern latitudes, populations had to survive the coldest periods in refugial areas and recurrently colonized northern regions during interglacials. Such a history usually results in a loss of genetic diversity. Populations that did not experience glaciations, in contrast, probably maintained most of their ancestral genetic diversity. These characteristics dramatically affected the present-day distribution of genetic diversity and may influence the ability of species to cope with the current global changes. We conducted a range-wide study of mitochondrial genetic diversity in the pine processionary moth (Thaumetopoea pityocampa/T. wilkinsoni complex, Notodontidae), a forest pest occurring around the Mediterranean Basin and in southern Europe. This species is responding to the current climate change by rapid natural range expansion and can also be accidentally transported by humans. Our aim was to assess if Quaternary climatic oscillations had a different effect across the species' range and to determine if genetic footprints of contemporary processes can be identified in areas of recent introduction. Results We identified three main clades that were spatially structured. In most of Europe, the genetic diversity pattern was typical for species that experienced marked glaciation cycles. Except in refugia, European populations were characterized by the occurrence of one main haplotype and by a strong reduction in genetic diversity, which is expected in regions that were rapidly re-colonized when climatic conditions improved. In contrast, all other sub-clades around the Mediterranean Basin occurred in limited parts of the range and were strongly structured in space, as is expected in regions in which the impact of glaciations was limited. In such places, genetic diversity was retained in most populations, and almost all haplotypes were endemic. This pattern was extreme on remote Mediterranean islands (Crete, Cyprus, Corsica) where highly differentiated, endemic haplotypes were found. Recent introductions were typified by the existence of closely-related haplotypes in geographically distant populations, which is difficult to detect in most of Europe because of a lack of overall genetic structure. Conclusion In regions that were not prone to marked glaciations, recent moth introductions/expansions could be detected due to the existence of a strong spatial genetic structure. In contrast, in regions that experienced the most intense Quaternary climatic oscillations, the natural populations are not genetically structured, and contemporary patterns of population expansion remain undetected.

Kerdelhue, Carole; Zane, Lorenzo; Simonato, Mauro; Salvato, Paola; Rousselet, Jerome; Roques, Alain; Battisti, Andrea

2009-01-01

311

Detrital zircon fission track thermochronology in key stratigraphic formations of the Danube system, Romania: climatic or tectonic signals?  

NASA Astrophysics Data System (ADS)

Recent thermochronological investigations of Romanian Carpathians, covering the Cretaceous-Quaternary exhumation and burial history of the orogen, has revealed significant constraints related to the understanding of its thermo-tectonic evolution. Available information in the form of less constrained thermochronological ages in the orogen and its foreland might indicate that climate change caused strong variation in erosion rates and sediment fluxes post-dating the Late Miocene continental collision. Moreover, in the SE Carpathians foreland, a change in sediment supply is suggested by both classical provenance and sequence stratigraphy studies that inferred an important contribution of the Messinian Salinity Crisis event (MSC) that took place in the Eastern Paratethys. Since the link between tectonics and climate is still a matter of debate in this sector of the Carpathians chain, one way of solving the controversy is to apply the robust zircon fission-track (ZFT) in key stratigraphic formations of the depositional area by the means of the thermochronological provenance study. The aim is to integrate the age signatures from the river drainage system as provenance markers by linking them with existing thermochronological data located in the exhumed source area of the Carpathians chain. A large number of samples were collected in the Upper Miocene to Quaternary (9-0 Ma) deposits of the western flank of the Focsani basin, located in the SE Carpathians foreland. In order to link this intermediate basin with the active marine depositional area which is presently the Black Sea, 13 additional samples were taken from recent (<10Ka) sediments of the Danube Delta for detrital ZFT analysis. This was complemented by exhumation ages in the denuded Carpathians area. Preliminary results suggest a key climatic control on the exhumation and erosion of the Carpathians chain during Upper Miocene-Quaternary times, with significant peak accelerations that are well correlated in space and time not only with the MSC event, but also with the Quaternary stages of enhanced climatic exhumation. This poster was supported by the EUROCORES programme TOPO-EUROPE of the European Science Foundation.

Trifan, C. I.; Andriessen, P. A. M.; Matenco, L.

2012-04-01

312

Expanded record of Quaternary oceanographic change: Amerasian Arctic Ocean  

USGS Publications Warehouse

Four sediment cores collected from the Northwind and Mendeleyev ridges, Arctic Ocean, from 1089 m to 1909 m water depth, provide an oceanographic record extending back into the Matuyama reversed polarity chron. Benthic foraminiferal analyses show four prominent assemblage zones: Bolivina arctica, Cassidulina teretis, Bulimina aculeata, and Oridorsalis tener from the upper Matuyama reversed polarity chronozone through the Brunhes normal polarity chronozone. These assemblage zones represent depth-dependent benthic foraminiferal biofacies changes associated with oceanographic events that occurred in the Amerasian basin at ??? 780 and 300 ka, and indicate oceanographic influence from the North Atlantic. Recognition of these benthic assemblage zones in Arctic cores from the Alpha Ridge indicates that the benthic foraminiferal zonations in intermediate to deep water (>1000 m) Arctic cores may be more useful than preexisting lithostratigraphic zonations and should provide important information pertaining to the Quaternary paleoceanographic evolution of the Arctic Ocean.

Ishman, S. E.; Polyak, L. V.; Poore, R. Z.

1996-01-01

313

The Pleistocene Boundary and the Beginning of the Quaternary  

NASA Astrophysics Data System (ADS)

The Pleistocene Boundary and the Beginning of the Quaternary presents the results of a forty-year international program to establish a precise definition for the most important boundary in geologic time - the beginning of the modern age of glacial climates. This book, the final report of International Geological Correlation Project 41, describes the selection of a fixed reference point in the sequence of deep-water marine strata exposed at Vrica, Italy. This point, dated to 1.81 million years before the present, coincides with the onset of the first of four major glacial phases. The opening chapters of the book document the geology and palaeontology of the agreed physical reference point, and the successful proposal of this point as the boundary-stratotype of the Pleistocene Epoch. The book then describes the correlation of the boundary throughout the ocean basins and continents of the world in terms of detailed stratigraphic criteria such as planktonic biostratigraphy, magnetostratigraphy and radiometric age determinations.

van Couvering, John A.

2004-12-01

314

A Quaternary ZnCdSeTe Nanotip Photodetector  

PubMed Central

The authors report the growth of needle-like high density quaternary Zn0.87Cd0.13Se0.98Te0.02nanotips on oxidized Si(100) substrate. It was found that average length and average diameter of the nanotips were 1.3 ?m and 91 nm, respectively. It was also found that the as-grown ZnCdSeTe nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. Furthermore, it was found that the operation speeds of the fabricated ZnCdSeTe nanotip photodetector were fast with turn-on and turn-off time constants both less than 2 s.

2009-01-01

315

Asynchronous extinction of late Quaternary sloths on continents and islands  

PubMed Central

Whatever the cause, it is extraordinary that dozens of genera of large mammals became extinct during the late Quaternary throughout the Western Hemisphere, including 90% of the genera of the xenarthran suborder Phyllophaga (sloths). Radiocarbon dates directly on dung, bones, or other tissue of extinct sloths place their “last appearance” datum at ?11,000 radiocarbon years before present (yr BP) or slightly less in North America, ?10,500 yr BP in South America, and ?4,400 yr BP on West Indian islands. This asynchronous situation is not compatible with glacial–interglacial climate change forcing these extinctions, especially given the great elevational, latitudinal, and longitudinal variation of the sloth-bearing continental sites. Instead, the chronology of last appearance of extinct sloths, whether on continents or islands, more closely tracks the first arrival of people.

Steadman, David W.; Martin, Paul S.; MacPhee, Ross D. E.; Jull, A. J. T.; McDonald, H. Gregory; Woods, Charles A.; Iturralde-Vinent, Manuel; Hodgins, Gregory W. L.

2005-01-01

316

Quaternary geophysical framework of the northeastern North Carolina coastal system  

USGS Publications Warehouse

The northeastern North Carolina coastal system, from False Cape, Virginia, to Cape Lookout, North Carolina, has been studied by a cooperative research program that mapped the Quaternary geologic framework of the estuaries, barrier islands, and inner continental shelf. This information provides a basis to understand the linkage between geologic framework, physical processes, and coastal evolution at time scales from storm events to millennia. The study area attracts significant tourism to its parks and beaches, contains a number of coastal communities, and supports a local fishing industry, all of which are impacted by coastal change. Knowledge derived from this research program can be used to mitigate hazards and facilitate effective management of this dynamic coastal system.

Thieler, E.R.; Foster, D.S.; Mallinson, D.M.; Himmelstoss, E.A.; McNinch, J.E.; List, J.H.; Hammar-Klose, E.S.

2013-01-01

317

Dissipative regime in low energy fission  

NASA Astrophysics Data System (ADS)

In this presentation, a generalization of the time dependent pairing equations is presented by including the Landau-Zener effect in the superfluid model. These new equations allows a mixing of seniority one configurations that allows us to obtain a ground state at the end of the process. An application concerning the C-14 emission is offered and its fine structure is explained. These new equations are furthermore used to evidence a dynamical pair breaking effect that could explain the fine odd-even effect in cold fission. The partition of the dissipated energy between the two fission fragments will be also modeled. Finally, the time dependent pairing equations are used to deduce a model for non-adiabatic cranking inertia.

Mirea, M.

318

Nuclear Fission Investigation with Twin Ionization Chamber  

SciTech Connect

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.

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

319

Fusion-fission energy systems evaluation  

SciTech Connect

This report serves as the basis for comparing the fusion-fission (hybrid) energy system concept with other advanced technology fissile fuel breeding concepts evaluated in the Nonproliferation Alternative Systems Assessment Program (NASAP). As such, much of the information and data provided herein is in a form that meets the NASAP data requirements. Since the hybrid concept has not been studied as extensively as many of the other fission concepts being examined in NASAP, the provided data and information are sparse relative to these more developed concepts. Nevertheless, this report is intended to provide a perspective on hybrids and to summarize the findings of the rather limited analyses made to date on this concept.

Teofilo, V.L.; Aase, D.T.; Bickford, W.E.

1980-01-01

320

True ternary fission of superheavy nuclei  

SciTech Connect

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.

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

321

SABR Fusion-Fission Hybrid Studies  

NASA Astrophysics Data System (ADS)

The Subcritical Advanced Burner Reactor (SABR) concept is a fast reactor comprised of a tokamak fusion neutron source based on ITER surrounded by an annular fission core adapted from Integral Fast Reactor designs. Previous work has examined SABR used to help close the nuclear fuel cycle by fissioning the transuranics from spent nuclear fuel. One focus of the present work is a SABR Breeder Reactor to achieve tritium self-sufficieny and a Pu breeding ratio significantly above 1 in order to provide fuel for SABR as well as for MOX-fueled LWR's and other fast reactors. Another focus of this research is the dynamic safety simulation of lloss-of-flow loss-of-heat-sink, loss-of-power, and positive reactivity accidents in the TRU fuel SABR burner reactor. The reactivity effect of thermal-induced bowing of fuel pins has been modeled, which is expected to provide passive safety.

Stewart, Chris

2012-03-01

322

Fission Fragment characterization with FALSTAFF at NFS  

NASA Astrophysics Data System (ADS)

The Neutrons for Science (NFS) facility will be one of the first installations of the SPIRAL2 facility. NFS will be composed of a time-of-flight baseline and irradiation stations and will allow studying neutron-induced reactions for energies going from some hundreds of keV up to 40 MeV. Continuous and quasi-monoenergetic energy neutron beams will be available. Taking advantage of this new installation, the development of an experimental setup for a full characterization of actinide fission fragments in this energy domain has been undertaken. To achieve this goal a new detection system called FALSTAFF (Four Arm cLover for the STudy of Actinide Fission Fragments) in under development. In this paper, the characteristics of the NFS facility will be exposed and the motivations for the FALSTAFF experiment will be presented. The experimental setup will be described and the expected resolutions based on realistic GEANT4 simulations will be discussed.

Doré, D.; Farget, F.; Lecolley, F.-R.; Ledoux, X.; Lehaut, G.; Materna, T.; Pancin, J.; Panebianco, S.

2013-03-01

323

System Concepts for Affordable Fission Surface Power  

NASA Technical Reports Server (NTRS)

This paper presents an overview of an affordable Fission Surface Power (FSP) system that could be used for NASA applications on the Moon and Mars. The proposed FSP system uses a low temperature, uranium dioxide-fueled, liquid metal-cooled fission reactor coupled to free-piston Stirling converters. The concept was determined by a 12 month NASA/DOE study that examined design options and development strategies based on affordability and risk. The system is considered a low development risk based on the use of terrestrial-derived reactor technology, high efficiency power conversion, and conventional materials. The low-risk approach was selected over other options that could offer higher performance and/or lower mass.

Mason, Lee; Poston, David; Qualls, Louis

2008-01-01

324

Synthesis and Characterization of Ruthenium(II) Phenanthroline Complexes Containing Quaternary Amine Substituents  

PubMed Central

A series of mixed ligand complexes of ruthenium(II) complexes 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 group 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 were observed. Both electrochemical and photophysical investigations indicate that the quaternary amine has little or no impact on the properties of the complex when compared to the complexes lacking the amine.

Bhuiyan, A. A.; Dossey, R.; Anderson, T. J.; Millett, F.; Durham, B.

2009-01-01

325

Quaternary volcanic rocks from Central Burma: Geochemical characteristics and petrogenesis  

NASA Astrophysics Data System (ADS)

Burma is located in the eastern margin of the India-Asia collision zone. The most significant geologic feature in the region is arguably the Sagaing Fault representing a dextral strike-slip fault system that links the eastern Himalayan Syntaxis in the north and the Andaman Sea in the south. This region is situated in a unique or ¡§transitional¡¨ position between contractional (Himalayan) and extensional (Andaman Sea) tectonic settings, and furthermore characterized by the eruption of a series of Middle Miocene to Quaternary volcanoes along the Sagaing Fault. Here we report geochemical and Sr-Nd isotopic analyses of Quaternary basalts and basaltic andesites recovered from Mt. Popa and Monywa areas, Central Burma. Major element data of the Burmese rocks show a potash-rich nature, with most of the Mt. Popa samples (8 out of 12 analyses) plotting in the high-K calc-alkaline suite and the Monywa samples (5 out of 7 analyses) in the shoshonitic suite. The latter may be further specified as absarokite based on their mineral constituents and trace element characteristics. All these rocks display significant depletions in the high field strength elements (HFSE; e.g., Nb, Ta and Ti), enrichments in the large ion lithophile elements (LILE; e.g., Cs, Rb, Ba, Th, U) and light rare earth elements. Thus, the overall incompatible trace element distribution patterns are similar to those of arc magmas formed in the subduction zone. Moreover, the Burmese rocks show high Nd and low Sr isotopic ratios, with ?Nd = +1 to +4 and 87Sr/86Sr~ 0.7045. Consequently, we propose that the magma source of the high-K calc-alkaline rocks from Mt. Popa is a juvenile mantle wedge in the region despite the Indian Ocean slab beneath this part of the Asian continent has already ceased its subduction. Under this framework, the Monywa absarokites represent small-degree melting products of a phlogopite-bearing peridotite source in the mantle wedge.

Yang, H.; Chung, S.; Chu, C.; Gallet, S.; Mitchell, A.

2007-12-01

326

Development of quaternary Ir-Ta-Ni-Al refractory superalloys  

SciTech Connect

To improve the performance of Ir-based alloys, the authors propose alloys designed by combining Ir- and Ni-based alloys because Ni-based alloys are ductile, have a relatively low density (about 8.5g/cm{sup 3}, compared to 22g/cm{sup 3} for Ir), and low cost. The objective is to combine the high-temperature strength of Ir-based alloys with the good ductility, low density, and low cost of Ni-based alloys. If the fcc and L1{sub 2} phases with coherent structure form in both alloys, the authors expect that the fcc and L1{sub 2} two-phase regions of the Ir- and Ni-based alloys will connect with each other at the interface of the Ir-based and Ni-based alloys. The coherency of the fcc/L1{sub 2} phase is very important for quaternary alloys to achieve high strength at high temperature. The authors chose the Ir-Ta alloy from the available Ir-based binary alloys because the strength of the Ir-Ta binary alloy is high at high temperature (over 700 MPa at 1,200 C) and because Ta has a solid solution hardening effect in Ni-based alloys. For the Ni alloy, they chose the Ni-Al alloy because it is of coherent structure of fcc and L1{sub 2}. They therefore studied the strength and microstructure of Ir-Ta-Ni-Al quaternary alloys.

Yu, Xihong; Yamabe-Mitarai, Yoko; Ro, Yoshikazu; Gu, Yuefeng; Harada, Hiroshi [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan)] [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan)

1999-08-20

327

Are seawater Sr/Ca variations preserved in Quaternary foraminifera?  

SciTech Connect

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.

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

1999-11-01

328

Quaternary glacial evolution in the Central Cantabrian Mountains (Northern Spain)  

NASA Astrophysics Data System (ADS)

The glacial evolution of the Cantabrian Mountains is not well known. Previous studies have focused on the extent of the glacial maximum and the presence of younger features in several massifs. Recently, efforts have been made to date glacial periods, particularly the glacial maximum. This work presents a reconstruction of the glacial evolution in the Cantabrian Mountains, providing data on the environmental characteristics and timing of the different stages from the Quaternary glacial maximum to the Little Ice Age. The study area covers 3000 km2 between the 4°58'W and 3°34'W and includes eleven massifs of the central area of the Cantabrian Mountains. The selected sectors have an Atlantic and Atlantic-Mediterranean transitional climate and include the highest massifs (above 2600 m) and low-altitude glacierised massifs (lower than 2000 m). Glacial extent and evolution have been reconstructed on the basis of detailed geomorphological and morphostratigraphic mapping. The equilibrium line altitude (palaeo-ELA) has been estimated for the different stages of each tongue. The ELA has been assessed by the AAR and modified Kurowski methods and altitude methods have been considered. A numerical chronological framework is proposed using 17 AMS radiocarbon and one OSL data obtained in lake and bog deposits from three massifs. Four main glacial stages have been differentiated, between 38,000 BP and the Little Ice Age. They correspond to different cold environments, and the number of glacial stages varies from one to four among the different massifs. Conclusions are analysed in the context of the Quaternary glacial evolution of other Iberian mountains.

Serrano, E.; González-Trueba, J. J.; Pellitero, R.; González-García, M.; Gómez-Lende, M.

2013-08-01

329

Comparative Functional Genomics of the Fission Yeasts  

Microsoft Academic Search

The fission yeast clade---comprising Schizosaccharomyces pombe, S. octosporus, S. cryophilus, and S. japonicus---occupies the basal branch of Ascomycete fungi and is an important model of eukaryote biology. A comparative annotation of these genomes identified a near extinction of transposons and the associated innovation of transposon-free centromeres. Expression analysis established that meiotic genes are subject to antisense transcription during vegetative growth,

Nicholas Rhind; Zehua Chen; Moran Yassour; Dawn A. Thompson; Brian J. Haas; Naomi Habib; Ilan Wapinski; Sushmita Roy; Michael F. Lin; David I. Heiman; Sarah K. Young; Kanji Furuya; Yabin Guo; Alison Pidoux; Huei Mei Chen; Barbara Robbertse; Jonathan M. Goldberg; Keita Aoki; Elizabeth H. Bayne; Aaron M. Berlin; Christopher A. Desjardins; Edward Dobbs; Livio Dukaj; Lin Fan; Michael G. FitzGerald; Courtney French; Sharvari Gujja; Klavs Hansen; Dan Keifenheim; Joshua Z. Levin; Rebecca A. Mosher; Carolin A. Müller; Jenna Pfiffner; Margaret Priest; Carsten Russ; Agata Smialowska; Peter Swoboda; Sean M. Sykes; Matthew Vaughn; Sonya Vengrova; Ryan Yoder; Qiandong Zeng; Robin Allshire; David Baulcombe; Bruce W. Birren; William Brown; Karl Ekwall; Manolis Kellis; Janet Leatherwood; Henry Levin; Hanah Margalit; Rob Martienssen; Conrad A. Nieduszynski; Joseph W. Spatafora; Nir Friedman; Jacob Z. Dalgaard; Peter Baumann; Hironori Niki; Aviv Regev; Chad Nusbaum

2011-01-01

330

Dissipation effects in low energy fission  

Microsoft Academic Search

The dissipation energy is computed using the microscopic time-dependent equations of motion along minimal action trajectories for three different values of the mass-asymmetries in the 236U fission. The single-particle level schemes are given by the two-center shell model. A qualitative agreement with the experimental mass distribution was obtained when the dissipation energy was taken into consideration in computing the penetrabilities.

M. Mirea; L. Tassangot; C. Stephan; C. O. Bacri

2004-01-01

331

Multiplicities of charged particles prior to fission  

NASA Astrophysics Data System (ADS)

We solve time-dependent master-equations for the cascade de-excitation of the compound nucleus, taking into account the transient behaviour of the fission width. This transient behaviour is related to the nuclear friction constant, and is parametrised in terms of a delay time ?. We extend recent work by Grange, Hassani and others by including both proton and neutron evaporation. Our results show that a measurement of charged-particle multiplicities should further confine ?.

Lanza, E. G.; Weidenmüller, H. A.

1986-06-01

332

Fusion, Fission, and Secretion During Phagocytosis  

NSDL National Science Digital Library

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.

2007-12-01

333

Fission track age of Transantarctic Mountain microtektites  

Microsoft Academic Search

We determined the fission track age of Transantarctic Mountain microtektites. The plateau method yielded a formation age of 0.85±0.17Ma. This age overlaps within error with that of the catastrophic impact that produced the Australasian tektite–microtektite strewn field ca. 0.8Ma ago. This provides further evidence that Transantarctic Mountain microtektites belong to the Australasian tektite–microtektite strewn field, as previously suggested on the

L. Folco; G. Bigazzi; M. D’Orazio; M. L. Balestrieri

2011-01-01

334

A New Role for Myosin II in Vesicle Fission  

PubMed Central

An endocytic vesicle is formed from a flat plasma membrane patch by a sequential process of invagination, bud formation and fission. The scission step requires the formation of a tubular membrane neck (the fission pore) that connects the endocytic vesicle with the plasma membrane. Progress in vesicle fission can be measured by the formation and closure of the fission pore. Live-cell imaging and sensitive biophysical measurements have provided various glimpses into the structure and behaviour of the fission pore. In the present study, the role of non-muscle myosin II (NM-2) in vesicle fission was tested by analyzing the kinetics of the fission pore with perforated-patch clamp capacitance measurements to detect single vesicle endocytosis with millisecond time resolution in peritoneal mast cells. Blebbistatin, a specific inhibitor of NM-2, dramatically increased the duration of the fission pore and also prevented closure during large endocytic events. Using the fluorescent markers FM1-43 and pHrodo Green dextran, we found that NM-2 inhibition greatly arrested vesicle fission in a late phase of the scission event when the pore reached a final diameter of ? 5 nm. Our results indicate that loss of the ATPase activity of myosin II drastically reduces the efficiency of membrane scission by making vesicle closure incomplete and suggest that NM-2 might be especially relevant in vesicle fission during compound endocytosis.

Cabeza, Jose M.; Acosta, Jorge; Ramirez-Ponce, Pilar; Ales, Eva

2014-01-01

335

A new approach to prompt fission neutron TOF data treatment  

NASA Astrophysics Data System (ADS)

The prompt neutron emission in spontaneous fission of 252Cf has been investigated applying digital signal electronics along with associated digital signal processing algorithms. A new mathematical approach, applicable to single events, was developed for prompt fission neutron (PFN) time-offlight distribution unfolding. The main goal was to understand the reasons of the long existing discrepancy between theoretical calculations and the measurements of prompt fission neutron (PFN) emission dependence on the total kinetic energy (TKE) of the fission fragments (FF). Since the 252Cf (sf) reaction is one of the main references for nuclear data the understanding of the PFN emission mechanism is very important both for nuclear fission theory and nuclear data. The experimental data were taken with a twin Frisch-grid ionization chamber and a NE213-equivalent neutron detector in an experimental setup similar to the well known work of C. Budtz-Jorgensen and H.-H. Knitter. About 2.5 × 105 coincidences between fission fragment (FF) and neutron detector response to prompt fission neutron detection have been registered ( ? 1.6 × 107 of total recorded fission events). Fission fragment kinetic energy, mass and angular distribution, neutron time-of-flight and pulse shape have been investigated using a 12-bit waveform digitizer. The signal waveforms have been analyzed using digital signal processing algorithms. The main goal of this work was a detailed description of the prompt fission neutron treatment.

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

336

Undergraduate Measurements For Fission Reactor Applications  

SciTech Connect

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.

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

337

Undergraduate Measurements For Fission Reactor Applications  

NASA Astrophysics Data System (ADS)

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 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.

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

2011-06-01

338

Calculated fission properties of the heaviest elements  

SciTech Connect

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.

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

1986-09-01

339

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

NASA Astrophysics Data System (ADS)

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 242,243Cm and 241Am. The latest direct neutron-induced measurement for the 243Cm 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 243,244,245Cm and 242Am compound nuclei in the excitation energy range from a few MeV to about 25 MeV.

Jurado, B.; Kessedjian, G.; Aiche, M.; Barreau, G.; Bidaud, A.; Czajkowski, S.; Dassié, D.; Haas, B.; Mathieu, L.; Osmanov, B.; Audouin, L.; Capellán, N.; Tassan-Got, L.; Wilson, J. N.; Berthoumieux, E.; Gunsing, F.; Theisen, Ch.; Serot, O.; Bauge, E.; Ahmad, I.; Greene, J. P.; Janssens, R. V. F.

2008-04-01

340

Minor-Actinides Fission Cross Sections and Fission Fragment Mass Yields via the Surrogate Reaction Technique  

NASA Astrophysics Data System (ADS)

The surrogate reaction method has been used to determine neutron-induced fission cross sections for the short-lived actinides 242, 243Cm and 241Am. The latest direct neutron-induced measurement for the 243Cm 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 243,244,245Cm and 242Am compound nuclei in the excitation energy range from a few MeV to about 25 MeV.

Jurado, B.; Kessedjian, G.; Aïche, M.; Barreau, G.; Bidaud, A.; Czajkowski, S.; Dassié, D.; Haas, B.; Mathieu, L.; Osmanov, B.; Audouin, L.; Capellán, N.; Tassan-Got, L.; Wilson, J. N.; Berthoumieux, E.; Gunsing, F.; Theisen, Ch.; Bauge, E.; Serot, O.; Ahmad, I.; Greene, J. P.; Janssens, R. V. F.

2008-04-01

341

Cross section for the subthreshold fission of {sup 236}U  

SciTech Connect

The cross section for {sup 236}U fission in the neutron-energy range E{sub n} = 0.001-20 keV was measured by using the INR RAS (Institute of Nuclear Research, Russian Academy of Sciences, Moscow) LSDS-100 neutron spectrometer of the lead slowing-down spectrometer type. The resonance fission areas of the resonances at 5.45 eV and 1.28 keV were found, and the fission widths of these resonances were evaluated. The cross section for the {sup 238}U(n, f) fission process was measured, and the threshold sensitivity of the LSDS-100 to small values of fission cross sections was estimated. The well-known intermediate structure in the cross section for the neutron-induced subbarrier fission of {sup 236}U was confirmed.

Alekseev, A. A.; Bergman, A. A.; Berlev, A. I.; Koptelov, E. A. [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation); Samylin, B. F.; Trufanov, A. M.; Fursov, B. I.; Shorin, V. S., E-mail: shorin@ippe.r [Institute of Physics and Power Engineering (Russian Federation)

2008-08-15

342

Cross section for the subthreshold fission of 236U  

NASA Astrophysics Data System (ADS)

The cross section for 236U fission in the neutron-energy range E n = 0.001 20 keV was measured by using the INR RAS (Institute of Nuclear Research, Russian Academy of Sciences, Moscow) LSDS-100 neutron spectrometer of the lead slowing-down spectrometer type. The resonance fission areas of the resonances at 5.45 eV and 1.28 keV were found, and the fission widths of these resonances were evaluated. The cross section for the 238U( n, f) fission process was measured, and the threshold sensitivity of the LSDS-100 to small values of fission cross sections was estimated. The well-known intermediate structure in the cross section for the neutron-induced subbarrier fission of 236U was confirmed.

Alekseev, A. A.; Bergman, A. A.; Berlev, A. I.; Koptelov, E. A.; Samylin, B. F.; Trufanov, A. M.; Fursov, B. I.; Shorin, V. S.

2008-08-01

343

Fission xenon from extinct Pu-244 in 14,301.  

NASA Technical Reports Server (NTRS)

Xenon extracted in step-wise heating of lunar breccia 14,301 contains a fission-like component in excess of that attributable to uranium decay during the age of the solar system. There seems to be no adequate source for this component other than Pu-244. Verification that this component is in fact due to the spontaneous fission of extinct Pu-244 comes from the derived spectrum which is similar to that observed from artificially produced Pu-244. It thus appears that Pu-244 was extant at the time lunar crustal material cooled sufficiently to arrest the thermal diffusion of xenon. Subsequent history has apparently maintained the isotopic integrity of plutonium fission xenon. Of major importance are details of the storage itself. Either the fission component is the result of in situ fission of Pu-244 and subsequent storage in 14,301 material, or the fission xenon was stored in an intermediate reservoir before incorporation into 14,301.

Drozd, R.; Hohenberg, C. M.; Ragan, D.

1972-01-01

344

Frequent gene fissions associated with human pathogenic bacteria.  

PubMed

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

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

2014-01-01

345

Isomeric yield ratios of fission products in proton-induced fission of 232 Th  

Microsoft Academic Search

Isomeric yield ratios of 11 fission products were measured in the system of 13 MeV proton-induced fission of232Th by an on-line ion-guide isotope separator. It was found that the closed shell structures of primary fragments and their\\u000a complementary fragments affect the isomeric yield ratios. Isomeric yield ratios of121Cd (11\\/2?, 3\\/2+) and135Xe (11\\/2?, 3\\/2+) were measured precisely in the proton energy

S. Goto; D. Kaji; H. Kudo; M. Fujita; T. Shinozuka; M. Fujioka

1999-01-01

346

Yields of fission products produced by thermal-neutron fission of 245Cm  

NASA Astrophysics Data System (ADS)

Absolute yields have been determined for 105 gamma rays emitted in the decay of 95 fission products representing 54 mass chains created during thermal-neutron fission of 245Cm. These results include 17 mass chains for which no prior yield data exist. Using a Ge(Li) detector, spectra were obtained of gamma rays between 30 sec and 0.3 yr after very short irradiations of thermal neutrons on a 1 ?g sample of 245Cm. On the basis of measured gamma-ray yields and known nuclear data, total chain mass yields and relative uncertainties were obtained for 51 masses between 84 and 156. The absolute overall normalization uncertainty is <8%. The measured A-chain cumulative yields make up 81% of the total light mass (A<=121) yield and 92% of the total heavy mass yield. The results are compared with fission-product yields previously measured with generally good agreement. The mass-yield data have been compared with those for thermal-neutron fission of 239Pu and for 252Cf(s.f.); the influences of the closed shells Z=50, N=82 are not as marked as for thermal-neutron fission of 239Pu but much more apparent than for 252Cf(s.f.). Information on the charge distribution along several isobaric mass chains was obtained by determining fractional yields for 12 fission products. The charge distribution width parameter, based upon data for the heavy masses, A=128 to 140, is independent of mass to within the uncertainties of the measurements. Gamma-ray assignments were made for decay of short-lived fission products for which absolute gamma-ray transition probabilities are either not known or in doubt. Absolute gamma-ray transition probabilities were determined as (51 +/- 8)% for the 374-keV gamma ray from decay of 110Rh, (35 +/- 7)% for the 1096-keV gamma ray from decay of 133Sb, and (21.2 +/- 1.2)% for the 255-keV gamma ray from decay of 142Ba. RADIOACTIVITY, FISSION 245Cm(n,f) En=thermal; measured ?(E?,T12) deduced mass, charge yields.

Dickens, J. K.; McConnell, J. W.

1981-01-01

347

Oxygen-Isotope Geochemistry of Quaternary Rhyolite from the Mineral Mountains, Utah, USA.  

National Technical Information Service (NTIS)

Oxygen isotope analyses were made of phenocryst and glass separates from four Quaternary rhyolite flows and domes in the Mineral Mountains, southwest Utah. With the exception of biotite in all samples and alkali feldspar in the rhyolite domes, all mineral...

J. R. Bowman S. H. Evans W. P. Nash

1982-01-01

348

Antibacterial properties of poly(quaternary ammonium) modified gold and titanium dioxide nanoparticles.  

PubMed

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

Wan, Weijie; Yeow, John T W

2012-06-01

349

Map and data for Quaternary faults and folds in Washington state  

USGS Publications Warehouse

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.

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

350

Petrology of the Quaternary Volcanics of the Roosevelt KGRA, and Adjoining Area, Utah.  

National Technical Information Service (NTIS)

The Roosevelt KGRA (known geothermal resource area) located near Milford, Utah, is associated with a suite of Quaternary silicic volcanics distributed for 15 km along the crest and western flank of the Mineral Mountains, a large Tertiary granite batholith...

W. P. Nash

1976-01-01

351

Late Quaternary History, Climate, and Oceanography of the Timor Sea, Northwestern Australia.  

National Technical Information Service (NTIS)

The history of late Quaternary climate in low latitudes is still a controversial issue. Studies of the morphology and sedimentary facies of the Timor Sea, supplemented by new radiocarbon dates, indicate that the region was considerably more arid than the ...

T. H. Van Andel G. R. Heath T. C. Moore D. F. R. McGeary

1967-01-01

352

Foraminiferal Evidence of Late Quaternary Sea Level Fluctuations from the West Flower Garden Bank.  

National Technical Information Service (NTIS)

Foraminiferal assemblages were analyzed in 8 piston cores and 22 surface samples from the West Flower Garden Bank in the northwest Gulf of Mexico in an attempt to accurately determine late Quaternary paleoclimatic and geologic events. The faunas are subdi...

B. R. Sidner C. W. Poag

1973-01-01

353

Biological evaluation of quaternary bis ammonium salt and cetylpyridinum bromide against S. epidermidis biofilm.  

PubMed

Quaternary ammonium compounds are broad-spectrum bacteriocides widely used as antiseptics, disinfection and preservation agents. The aim of this study was to examine the activity of two quaternary ammonium salts, cetylpyridinum bromide and a newly synthesized quaternary bis ammonium salt, against S. epidermidis biofilm. The average values of killing efficiency for cetylpyridinum bromide ranged from 26.6% to 64.1% for all tested concentrations (0.125 to 8.0 microg x mL(-1)) and for quaternary bis ammonium salt the percentage of killing efficiency ranged from 59.7% to 88.4% for tested concentrations (from 2.0 to 128.0 microg x mL(-1)). Both tested compounds significantly affect staphylococcal biofilms, but any of used concentrations caused a total eradication of bacterial biofilm. PMID:24730129

Stefa?ska, Joanna; Pietruczuk-Padzik, Anna; Struga, Marta; Borkowski, Maciej; Tyski, Stefan

2013-01-01

354

Asymmetric organocatalytic Michael-?-amination sequence for the construction of a quaternary stereocenter.  

PubMed

Combination of secondary and primary amine-catalyzed organocascade Michael-?-amination is described. This sequence afforded ?-hydrazino aldehydes bearing a quaternary stereocenter with high yield and excellent stereoselectivity. PMID:21140009

Desmarchelier, Alaric; Marrot, Jérôme; Moreau, Xavier; Greck, Christine

2011-02-21

355

Metalorganic Vapor-Phase Epitaxial Growth and Characterization of Quaternary AlGaInN  

SciTech Connect

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.

BANAS, MICHAEL ANTHONY; CRAWFORD, MARY H.; FIGIEL, JEFFREY J.; HAN, JUNG; LEE, STEPHEN R.; MYERS JR., SAMUEL M.; PETERSON, GARY D.

1999-09-27

356

Novel approach for prediction of ultrasonic velocity in quaternary liquid mixtures  

Microsoft Academic Search

A modified Flory theory along with the Auerbach and Altenberg relations has been employed for the computation of ultrasonic velocity of three quaternary liquid mixtures and a comparative study of all the three relations has then been carried out.

J. D. Pandey; A. K. Singh; Ranjan Dey

2005-01-01

357

OMVPE Growth of Quaternary (Al,Ga,In)N for UV Optoelectronics (title change from A)  

SciTech Connect

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.

HAN,JUNG; FIGIEL,JEFFREY J.; PETERSEN,GARY A.; MYERS JR.,SAMUEL M.; CRAWFORD,MARY H.; BANAS,MICHAEL ANTHONY; HEARNE,SEAN JOSEPH

2000-01-18

358

Neck influence on dynamics of cluster radioactivities and cold fission  

SciTech Connect

In this paper, a two-center parametrization with smooth neck is used to describe the shapes during the fission process of {sup 234}U in a wide range of mass asymmetry (cold fission with {sup 100}Zr fragment, {sup 28}Mg radioactivity and {alpha}-decay). The optimum fission path has been found by minimizing the action integral. The neck influence is stronger for lower mass asymmetry.

Poenaru, D.N.; Greiner, W. (Inst. fuer Theoretisch Physik, J.W. Goethe-Univ., Postfach 111932, D-6000 Frankfurt am Main (DE)); Mirea, M.; Cata, I.; Mazilu, D. (Inst. of Atomic Physics, P.O. Box MG-6, RO-76900 Bucharest (RO))

1990-10-20

359

Non-axial shapes in spontaneous fission of superheavy nuclei  

Microsoft Academic Search

We test the importance of non-axial nuclear shapes in spontaneous fission of heavy and superheavy even-even nuclei from the region around a hypothetical doubly magic nucleus 298114. Fission half-lives are calculated by finding dynamical fission paths as dictated by the least WKB action principle with the macroscopic-microscopic energy and the cranking inertial parameters. Results show that the effects of non-axial

R. A. Gherghescu; J. Skalski; Z. Patyk; A. Sobiczewski

1999-01-01

360

Neutron flux profile monitor for use in a fission reactor  

DOEpatents

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.

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

1983-01-01

361

Nuclear level density and the mass distribution of fission fragments  

NASA Astrophysics Data System (ADS)

Using the single particle energy spectrum and Bethe's formula for nuclear level density, the mass distribution of fission fragments is calculated for nuclei 236U, 258Fm, and 240Pu, and also for the compound systems 84Kr + 238U and 129Xe + 197Au at different excitation energies. The results are in reasonable agreement with experimental yield curves. RADIOACTIVITY, FISSION Nuclear level density, mass and charge distribution of fission fragments.

Rajasekaran, M.; Devanathan, V.

1981-12-01

362

Generalization of Kramers's formula: Fission over a multidimensional potential barrier  

NASA Astrophysics Data System (ADS)

We generalize Kramers's rate expression for diffusion over a potential barrier to the case of a diffusion problem for n degrees of freedom. These can be thought of as the shape degrees of freedom of a fissioning nucleus. We present our formula for the fission width and discuss its dependence on the parameters-the mass tensor, the friction tensor, and the shape of the potential landscape. NUCLEAR REACTIONS, FISSION Diffusion, transition state method.

Jing-Shang, Zhang; Weidenmüller, H. A.

1983-11-01

363

Quantal dynamics of dissipation in heavy ion nuclear fission  

NASA Astrophysics Data System (ADS)

Energy dissipation during heavy ion nuclear fission has been calculated by employing the one-dimensional time dependent frictional Schrödinger equation. The variation of loss of energy with respect to the shape of the fissioning system follows the same trend as the classical frictional matrix. The dissipative loss of kinetic energy with respect to time is also shown. NUCLEAR REACTIONS, FISSION Ar + Th, Elab=250 MeV, onedimensional quantized frictional motion, loss of energy.

Mukherjee, S. N.; Pandey, L. N.

1983-09-01

364

Fission studies with 140 MeV {alpha} particles  

SciTech Connect

Binary fission induced by 140 MeV {alpha} particles has been measured for {sup nat}Ag, {sup 139}La, {sup 165}Ho, and {sup 197}Au targets. The measured quantities are the total kinetic energies, fragment masses, and fission cross sections. The results are compared with other data and systematics. A minimum of the fission probability in the vicinity Z{sup 2}/A=24 is observed.

Buttkewitz, A.; Duhm, H. H.; Strauss, W. [I. Institut fuer Experimentalphysik, Universitaet Hamburg, Hamburg (Germany); Goldenbaum, F. [Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Machner, H. [Institut fuer Kernphysik, Forschungszentrum Juelich, Juelich (Germany); Fachbereich Physik, Universitaet Duisburg-Essen, Duisburg (Germany)

2009-09-15

365

New Fission Cross Section Measurements using a Time Projection Chamber  

NASA Astrophysics Data System (ADS)

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.

Sadler, Michael

2008-03-01

366

Gamma Rays from Short-Lived Fission-Fragment Isomers  

Microsoft Academic Search

Measurements of the energy spectra of isomeric gamma rays from the neutron fission of U235 and Pu239 at a number of time intervals between 50 and 600 musec showed six prominent gamma rays for both cases of fission. The intensities and half-lives for these gamma rays indicate that there are three fission-fragment isomers, each giving rise to a pair of

R. E. Sund; R. B. Walton

1966-01-01

367

Quantitative morphotectonics of the Pliocene to Quaternary Auletta basin, southern Italy  

Microsoft Academic Search

The geomorphological evolution of the Pliocene–Quaternary Auletta basin, a wide fault-bounded depression of the southern Apennines axial zone, Italy, was reconstructed using both DEM-based morphometric analysis and classical morphotectonic investigations. Morphotectonic analyses have been integrated with geological, structural and paleomagnetic data in order to reconstruct the Quaternary evolution of the area.The Auletta basin coincides with the lower valley of the

Dario Gioia; Marcello Schiattarella; Massimo Mattei; Giovanni Nico

2011-01-01

368

New quaternary benzyl chloride salts for inclusion in hair cream rinse formulations  

Microsoft Academic Search

Quaternary ammonium salts have been prepared from benzyl chloride and amino amides and an amino ester of a long chain fatty\\u000a acid. These benzyl salts were incorporated in simple hair conditioner formulations containing the quaternary salt, anhydrous\\u000a lanolin, cetyl alcohol, and water. Preliminary evaluations indicated that the formulations were effective in the removal of\\u000a tangles and snarls following washing with

A. V. Bailey; G. Sumrell; T. E. Gurtner

1974-01-01

369

Quaternary turbidite systems on the northern margins of the Balearic Basin (Western Mediterranean): a synthesis  

Microsoft Academic Search

The Balearic Basin is a young basin composed of thick Plio–Quaternary sediments, including active gravity sedimentation. During the Quaternary, gravity processes deposited (1) turbidite systems, either as symmetrical fans (Petit-Rhne and Valencia fans) or asymmetrical ridges (Marseille–Planier, Grand-Rhne and Pyreneo-Languedocian ridges) and (2) several mass-transport deposits, indicating recurrent sedimentary failures of the margin. This paper synthesizes previous works and proposes

L. Droz; A. T. dos Reis; M. Rabineau; S. Berné; G. Bellaiche

2006-01-01

370

Viscosities of nonelectrolyte liquid mixtures. III. Selected binary and quaternary mixtures  

Microsoft Academic Search

This paper is the final in a series of three viscosity and density studies of pure n-alkanes and selected binary and quaternary mixtures. A standard U-tube viscometer was used for viscosity measurements, and a Pyrex flask-type pycnometer was used for density determinations. Results are given here for pure alkane and selected binary mixtures of n-tetradecane + n-octane, for selected quaternary

D. L. Wakefield

1988-01-01

371

Synthesis and anti-microbial activities of choline-like quaternary ammonium chlorides.  

PubMed

New choline-like quaternary ammonium chlorides were obtained. The work-up procedure of synthesis was quick and efficient. The obtained chlorides showed anti-microbial activities. Quaternary ammonium chlorides derivatives of deanol esters exhibited strong activity and wide anti-bacterial spectra, similar to the activity of benzalkonium chloride. The relationship between chemical structure and anti-microbial activity was analyzed by the QSAR method. PMID:14642336

Pernak, Juliusz; Chwa?a, Przemys?aw

2003-01-01

372

Agricultural contaminants in Quaternary aquitards: A review of occurrence and fate in North America  

Microsoft Academic Search

.   The intensity of agriculture has increased significantly during the past 30 years, resulting in increased detection of agricultural\\u000a contaminants (nutrients, pesticides, salts, trace elements, and pathogens) in groundwater. Till, glaciolacustrine, and loess\\u000a deposits of Quaternary age compose the most common surficial deposits underlying agricultural areas in North America. Quaternary\\u000a aquitards generally contain higher concentrations of solid organic carbon (SOC, as

S. J. Rodvang; W. W. Simpkins

2001-01-01

373

Effect of alkyl quaternary ammonium on processing discoloration of melt-intercalated PVC-montmorillonite composites  

Microsoft Academic Search

The effects of alkyl quaternary ammonium on the processing thermal stability of poly (vinyl chloride)\\/alkyl quaternary ammonium modified montmorillonite (PVC\\/OMMT) composites were investigated. PVC\\/sodium montmorillonite (MMT) composites were prepared for comparison. The intercalated PVC\\/OMMT composites exhibited a non-terminal rheological behavior, and showed better mechanical properties and higher thermal degradation stability than the PVC\\/MMT composites. However, under identical melt processing conditions,

Chaoying Wan; Yong Zhang; Yinxi Zhang

2004-01-01

374

Pervaporation of the quaternary mixture present during the esterification of lactic acid with ethanol  

Microsoft Academic Search

Pervaporation of the quaternary mixture involved in the synthesis of ethyl lactate, water\\/ethanol\\/ethyl lactate\\/lactic acid, has been investigated. Pervaporation experiments were performed with the commercial hydrophilic membrane PERVAP® 2201 at 327.15 and 348.15K. PERVAP® 2201 membrane was previously tested for some of the binary mixtures present in the quaternary mixture showing high water selectivity. The effects of pervaporation temperature and

Patricia Delgado; María Teresa Sanz; Sagrario Beltrán

2009-01-01

375

Fission cross sections in the intermediate energy region  

SciTech Connect

Until recently there has been very little cross section data for neutron-induced fission in the intermediate energy region, primarily because no suitable neutron source has existed. At Los Alamos, the WNR target-4 facility provides a high-intensity source of neutrons nearly ideal for fission measurements extending from a fraction of a MeV to several hundred MeV. This paper summarizes the status of fission cross section data in the intermediate energy range (En > 30 MeV) and presents our fission cross section data for {sup 235}U and {sup 238}U compared to intranuclear cascade and statistical model predictions.

Lisowski, P.W.; Gavron, A.; Parker, W.E.; Ullmann, J.L.; Balestrini, S.J. (Los Alamos National Lab., NM (USA)); Carlson, A.D.; Wasson, O.A. (National Inst. of Standards and Technology, Gaithersburg, MD (USA)); Hill, N.W. (Oak Ridge National Lab., TN (USA))

1991-01-01

376

Generalized Energy-Dependent Q Values for Fission  

SciTech Connect

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.

Vogt, R

2010-03-31

377

Differences between angular distributions of fission fragments of unequal mass  

SciTech Connect

Results are presented of measurements of the angular anisotropy of unequal-mass fragments from the fission of /sup 232/Th and /sup 236//sup ,//sup 238/U by neutrons near the fission threshold. A radiochemical procedure was used. Differences were observed in the angular distributions of fragments having unequal masses. The result was unexpected for the contemporary (with shell corrections and statistical approach) liquid-drop model of fission, and can be explained in the molecular-fission model and others that take into account the barrier to separation of the produced fragments.

Gokhberg, B.M.; Kozlov, L.D.; Lisin, S.K.; Morozov, L.N.; Pchelin, V.A.; Chistyakov, L.V.; Shigin, V.A.; Shubko, V.M.; Yashin, Y.A.

1988-02-01

378

A role for myosin II in mammalian mitochondrial fission.  

PubMed

Mitochondria are dynamic organelles, undergoing both fission and fusion regularly in interphase cells. Mitochondrial fission is thought to be part of a quality-control mechanism whereby damaged mitochondrial components are segregated from healthy components in an individual mitochondrion, followed by mitochondrial fission and degradation of the damaged daughter mitochondrion. Fission also plays a role in apoptosis. Defects in mitochondrial dynamics can lead to neurodegenerative diseases such as Alzheimer's disease. Mitochondrial fission requires the dynamin GTPase Drp1, which assembles in a ring around the mitochondrion and appears to constrict both outer and inner mitochondrial membranes. However, mechanisms controlling Drp1 assembly on mammalian mitochondria are unclear. Recent results show that actin polymerization, driven by the endoplasmic reticulum-bound formin protein INF2, stimulates Drp1 assembly at fission sites. Here, we show that myosin II also plays a role in fission. Chemical inhibition by blebbistatin or small interfering RNA (siRNA)-mediated suppression of myosin IIA or myosin IIB causes an increase in mitochondrial length in both control cells and cells expressing constitutively active INF2. Active myosin II accumulates in puncta on mitochondria in an actin- and INF2-dependent manner. In addition, myosin II inhibition decreases Drp1 association with mitochondria. Based on these results, we propose a mechanistic model in which INF2-mediated actin polymerization leads to myosin II recruitment and constriction at the fission site, enhancing subsequent Drp1 accumulation and fission. PMID:24485837

Korobova, Farida; Gauvin, Timothy J; Higgs, Henry N

2014-02-17

379

The detection of delayed ?-rays between intense bremsstrahlung pulses for discriminating fissionable from non-fissionable materials  

NASA Astrophysics Data System (ADS)

The detection and identification of delayed fission ?-rays emitted between intense bremsstrahlung pulses was investigated as a method to discriminate between fissionable and non-fissionable materials. Photofission and other photonuclear reactions were induced in U238, Pb, Fe and Be targets using a pulsed bremsstrahlung beam for several endpoint energies between 8 and 20 MeV. In the 33 ms between irradiating pulses, correlated photon energy and time spectra were collected using a high-purity germanium detector. When non-fissionable materials were irradiated, the high-energy ?-ray yield decreased a couple orders of magnitude within the first ˜12 ms after the pulse. In contrast, the high-energy ?-rays emitted from the decay of fission fragments were nearly constant throughout the period between bremsstrahlung pulses. Hence, a basic energy and time discrimination provides a unique high-energy delayed ?-ray signature for fissionable material detection.

Reedy, E. T. E.; Thompson, S. J.; Hunt, A. W.

2009-07-01

380

Quaternary evolution of the Agri Valley, Southern Italy  

NASA Astrophysics Data System (ADS)

The Agri Valley (Southern Italy) is a key area for understanding the Quaternary evolution of a large sector of the external Southern Apennines, due to its E-W orientation across the mountain chain. It also represents one of the most tectonically active regions of Southern Italy and it therefore deserves a particular interest. Based on the great sensitivity of the rivers in recording even small changes of the topographic gradient, a detailed morphological analysis of the fluvial terraces has been carried out along the valley. We also carefully analysed the several orders of marine terraces occurring along the final sector of the valley. Available structural, stratigraphic, geophysical, seismotectonic and other morphological data have been taken into account in order to reconstruct the Quaternary evolution of the area. Accordingly, the Agri Valley can be subdivided into three reaches, diachronously developed during Pleistocene times and characterized by a differentiated geological evolution. Two major tectonic structures are mainly responsible for this segmentation and namely the Armento Thrust, to the West, and the Rotondella anticline-Scorciabuoi Fault, to the East. The high Agri Valley represents the first reach both morphologically and chronologically. It formed during (Late?) Pliocene, while erosional processes producing progressive deepening, widening and lengthening of the valley certainly persisted throughout the Early Pleistocene. The general uplift of this sector was probably induced by activity along the Armento Thrust. However, from Middle to Late Pleistocene this sector was characterised by depositional conditions associated to the accumulation of a 200-300 m thick sedimentary succession, the so-called Complesso Val d'Agri. Possible causes of this inversion will be discussed. Only from latest Quaternary onwards, this sector of the valley was newly affected by entrenching due to a progressive phenomenon of regressive erosion across the lithological threshold of the Armento anticline. The second reach of the Agri Valley entirely crosses the Sant'Arcangelo Basin from West to East. The sedimentary infilling mainly consists of a marine succession where only the youngest conglomeratic Serra Corneta Fm, of Early to early Middle Pleistocene age, represents a pure continental environment. Although this alluvial plain was certainly crossed by several water streams, the second reach of the Agri Valley began forming only when the regional uplift prevailed and diffused alluvial conditions were therefore abandoned. As a consequence, since Middle Pleistocene this sector of the valley was continuously deepening and widening though the occurrence of river terraces clearly document the stepping behaviour of the process. Because of the lithological contrast occurring where the river crosses the Armento anticline, to the West, and due to the probable recent activity along the Scorciabuoi Fault, to the East, this second reach of the Agri Valley can be still easily delimited by two knick-points occurring along the river bed. Also the third reach of the valley started forming during Middle Pleistocene due to the seaward river lengthening consequent of the progressive entrenching of the marine sediments that were continuously uplifted and inexorably brought into subaerial conditions. The occurrence of several orders of morphologically linked fluvial and marine terraces clearly documents this regional geodynamic process and the role played by eustasy. In particular, this latter phenomenon allowed to attempt some estimates on the amount of uplift rate affecting the region. Also the analysis of the fluvial pattern, the load-type and the sinuosity allows to segment the river in several sectors with different characteristics and behaviour ranging from purely meandering to transitional meandering-thalweg braided channels. Longitudinal variations are observed and are likely associated to major tectonic structures.

Caputo, R.; Bianca, M.

2003-04-01

381

Fission-fragment angular distributions for the 19F + 208Pb near- and sub-barrier fusion-fission reaction  

Microsoft Academic Search

Fission cross sections and angular distributions have been measured for the 19F + 208Pb reaction at bombarding energies from 83 to 105 MeV. The fission excitation function is well reproduced on the basis of the coupled-channels theory. The fission-fragment angular distributions are calculated in terms of the transition-state theory, with the transmission coefficients extracted from the excitation function calculation. It

Huanqiao Zhang; Zuhua Liu; Jincheng Xu; Kan Xu; Jun Lu; Ming Ruan

1990-01-01

382

The detection of delayed gamma-rays between intense bremsstrahlung pulses for discriminating fissionable from non-fissionable materials  

Microsoft Academic Search

The detection and identification of delayed fission gamma-rays emitted between intense bremsstrahlung pulses was investigated as a method to discriminate between fissionable and non-fissionable materials. Photofission and other photonuclear reactions were induced in U238, Pb, Fe and Be targets using a pulsed bremsstrahlung beam for several endpoint energies between 8 and 20MeV. In the 33ms between irradiating pulses, correlated photon

E. T. E. Reedy; S. J. Thompson; A. W. Hunt

2009-01-01

383

Late Quaternary paleoceanography of the Eurasian Basin, Arctic Ocean  

NASA Astrophysics Data System (ADS)

We reconstructed late Quaternary deep (3000-4100 m) and intermediate depth (1000-2500 m) paleoceanographic history of the Eurasian Basin, Arctic Ocean from ostracode assemblages in cores from the Lomonosov Ridge, Gakkel Ridge, Yermak Plateau, Morris Jesup Rise, and Amundsen and Makarov Basins obtained during the 1991 Polarstern cruise. Modern assemblages on ridges and plateaus between 1000 and 1500 m are characterized by abundant, relatively species-rich benthic ostracode assemblages, in part, reflecting the influence of high organic productivity and inflowing Atlantic water. In contrast, deep Arctic Eurasian basin assemblages have low abundance and low diversity and are dominated by Krithe and Cytheropteron reflecting faunal exchange with the Greenland Sea via the Fram Strait. Major faunal changes occurred in the Arctic during the last glacial/interglacial transition and the Holocene. Low-abundance, low-diversity assemblages from the Lomonosov and Gakkel Ridges in the Eurasian Basin from the last glacial period have modern analogs in cold, low-salinity, low-nutrient Greenland Sea deep water; glacial assemblages from the deep Nansen and Amundsen Basins have modern analogs in the deep Canada Basin. During Termination 1 at intermediate depths, diversity and abundance increased coincident with increased biogenic sediment, reflecting increased organic productivity, reduced sea-ice, and enhanced inflowing North Atlantic water. During deglaciation deep Nansen Basin assemblages were similar to those living today in the deep Greenland Sea, perhaps reflecting deepwater exchange via the Fram Strait. In the central Arctic, early Holocene faunas indicate weaker North Atlantic water inflow at middepths immediately following Termination 1, about 8500-7000 year B.P., followed by a period of strong Canada Basin water overflow across the Lomonosov Ridge into the Morris Jesup Rise area and central Arctic Ocean. Modern perennial sea-ice cover evolved over the last 4000-5000 years. Late Quaternary faunal changes reflect benthic habitat changes most likely caused by changes in the import of cold, deepwater of Greenland Sea origin and warmer and middepth Atlantic water to the Eurasian Basin through the Fram Strait, and export of Arctic Ocean deepwater. Appendix Tables Al-A4 are available on microfiche. Orderfrom the American Geophysical Union, 2000 Florida Avenue,N.W., Washington, DC 20009. Document P94-002; $2.50.Payment must accompany order.

Cronin, T. M.; Holtz, T. R.; Stein, R.; Spielhagen, R.; Fütterer, D.; Wollenburg, J.

1995-04-01

384

A model of the Quaternary geological deposits of Bucharest City  

NASA Astrophysics Data System (ADS)

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.

Serpescu, Irina; Radu, Emil; Radu Gogu, Constantin; Amine Boukhemacha, Mohamed; Gaitanaru, Dragos; Bica, Ioan

2013-04-01

385

Late Quaternary carbonate deposition at the bottom of the world  

NASA Astrophysics Data System (ADS)

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.

Frank, Tracy D.; James, Noel P.; Bone, Yvonne; Malcolm, Isabelle; Bobak, Lindsey E.

2014-05-01

386

Quaternary ammonium derivatives as spasmolytics for irritable bowel syndrome.  

PubMed

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

Evangelista, S

2004-01-01

387

Antiproton Powered Gas Core Fission Rocket  

SciTech Connect

Extensive research in recent years has demonstrated that 'at rest' annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

Kammash, Terry [Department of Nuclear Engineering and Radiological Sciences, University of Michigan, 2355 Bonisteel Blvd, Ann Arbor, MI 48109 (United States)

2005-02-06

388

Antiproton Powered Gas Core Fission Rocket  

NASA Astrophysics Data System (ADS)

Extensive research in recent years has demonstrated that ``at rest'' annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

Kammash, Terry

2005-02-01

389

Antiproton Powered Gas Core Fission Rocket  

NASA Astrophysics Data System (ADS)

Extensive research in recent years has demonstrated that “at rest” annihilation of antiprotons in the uranium isotope U238 leads to fission at nearly 100% efficiency. The resulting highly-ionizing, energetic fission fragments can heat a suitable medium to very high temperatures, making such a process particularly suitable for space propulsion applications. Such an ionized medium, which would serve as a propellant, can be confined by a magnetic field during the heating process, and subsequently ejected through a magnetic nozzle to generate thrust. The gasdynamic mirror (GDM) magnetic configuration is especially suited for this application since the underlying confinement principle is that the plasma be of such density and temperature as to make the ion-ion collision mean free path shorter than the plasma length. Under these conditions the plasma behaves like a fluid, and its escape from the system is analogous to the flow of a gas into vacuum from a vessel with a hole. For the system we propose we envisage radially injecting atomic or U238 plasma beam at a pre-determined position and axially pulsing an antiproton beam which upon interaction with the uranium target gives rise to near isotropic ejection of fission fragments with a total mass of 212 amu and total energy of about 160 MeV. These particles, along with the annihilation products (i.e. pions and muons) will heat the background U238 gas - inserted into the chamber just prior to the release of the antiproton - to one keV temperature. Preliminary analysis reveals that such a propulsion system can produce a specific impulse of about 3000 seconds at a thrust of about 50 kN. When applied to a round trip Mars mission, we find that such a journey can be accomplished in about 142 days with 2 days of thrusting and requiring only one gram of antiprotons to achieve it.

Kammash, T.

390

Monte Carlo calculation of the deexcitation of fission fragments in the spontaneous fission of 252Cf  

NASA Astrophysics Data System (ADS)

The consequences of the evaporation of prompt neutrons and ? rays from primary fission fragments in the spontaneous fission of 252Cf have been examined by a Monte Carlo method. A semiempirical mass equation and experimental values of total kinetic energies are used to obtain the sum of excitation energies of complementary fragments. The division of this energy between complementary fragments is determined by the two-spheroid model for the scission configuration. The prompt neutron multiplicity distribution gives a value of 3.68 for the average number of prompt neutrons in 252Cf(sf). Calculated values of the average number of prompt neutrons as a function of fragments mass are in good agreement with the experimental values. Calculated results for the charge dependence of total ?-ray energies show an odd-even effect, whereas no such effect is apparent in the charge dependence of the average number of neutrons. Mass and charge distributions of secondary fission fragments are also well reproduced in the calculations. NUCLEAR REACTIONS, FISSION 252Cf(sf); calculated prompt neutrons and ? rays. Pairing effect on ?-ray energy.

Kildir, M.; Aras, N. K.

1982-01-01

391

Recent fission cross section standards measurements  

SciTech Connect

The /sup 235/U(n,f) reaction is the standard by which most neutron induced fission cross sections are determined. Most of these cross sections are derived from relatively easy ratio measurements to /sup 235/U. However, the more difficult /sup 235/U(n,f) cross section measurements require the use of advanced neutron detectors for the determination of the incident neutron fluence. Examples of recent standard cross section measurements are discussed, various neutron detectors are described, and the status of the /sup 235/U(n,f) cross section standard is assessed. 23 refs., 8 figs., 4 tabs.

Wasson, O.A.

1985-01-01

392

Fission neutron spectra measurements at LANSCE - status and plans  

SciTech Connect

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.

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

393

Yields of fission products produced by thermal-neutron fission of 249Cf  

NASA Astrophysics Data System (ADS)

Absolute yields have been determined for 107 gamma rays emitted in the decay of 97 fission products representing 54 mass chains created during thermal-neutron fission of 249Cf. These results include 14 mass chains for which no prior yield data exist. Using a Ge(Li) detector, spectra were obtained of gamma rays emanating from a 0.4 ?g sample of 249Cf between 45 s and 0.4 yr after very short irradiations of the 249Cf by thermal neutrons. On the basis of measured gamma-ray yields and known nuclear data, total chain mass yields and relative uncertainties were obtained for 51 masses between 89 and 156. The absolute overall normalization uncertainty is ~8%. The measured A-chain cumulative yields make up 77% of the total light mass (A<=123) yield and 79% of the total heavy mass yield. The results are compared with fission-product yields previously measured, with generally good agreement. Information on the charge distribution along several isobaric mass chains was obtained by determining fractional yields for 11 fission products and combining these results with other measurements. The charge distribution width parameter for the heavy masses A=128 to 140 is independent of mass to within the uncertainties of the measurements. For the light masses A=89 to 112 the charge distribution parameter is also independent of mass but is smaller than for the heavy masses. Total chain yields are in fair agreement with the current evaluation for 249Cf. [RADIOACTIVITY, FISSION 249Cf(n,f) En=thermal measured ?(E?,T12) deduced mass, charge yields.

Dickens, J. K.; McConnell, J. W.

1981-07-01

394

New perspectives on Beringian Quaternary paleogeography, stratigraphy, and glacial history  

NASA Astrophysics Data System (ADS)

Aspects of the paleogeography, stratigraphy, and glacial history of Beringia have been greatly revised over the past 15-20 yr. Access to North East Russia, in particular, has provided the opportunity to evaluate the Beringia landscape as a contiguous subcontinent during the Quaternary. For the first time, new research has made clearer the connection between tectonic forces and the submergence of the Bering Strait during the middle Pliocene. Revisions in the regional stratigraphy of glacial and interglacial deposits in northwest Alaska and northeast Russia provide a new foundation for assessing the causes for differences in glacial ice extent through time. The consensus of all field workers verifies that glacial ice throughout most of Beringia was of very limited extent during the last glacial maximum. The onset of regional glaciation during the waning stages of the last interglaciation is clearly out of phase with glaciation at lower latitudes. Despite the lack of much glacial activity during the early Holocene, Alaska contains a rich record of late Holocene glacial response to Neoglacial cooling. Changes in the Holocene environment of Beringia likely had a profound affect on early inhabitants. The curiosity-driven vision and spirit of both David Hopkins and the late Troy Pewe have had a profound influence on Arctic paleoenvironmental research.

Brigham-Grette, Julie

2001-01-01

395

Liquid chromatography of hydrocarbonaeous quaternary amines on cyclodextrin bonded silica  

USGS Publications Warehouse

Mixtures of n-alkylbenzyldimethylammonium chloride (ABDAC) were resolved into homologous components by high-performance liquid chromatography (HPLC) with a cyclodextrin-bonded silica stationary phase. With a few exceptions, results from this study are similar to those obtained from traditional reversed-phase HPLC. It was found that the presence of electrolytes in aqueous mobile phases is not a critical factor in determining the success of HPLC separation. Under normal HPLC conditions, a mobile phase consisting of either methanol–water (50:50) or acetonitrile–water (30:70) was employed for obtaining adequate resolution of the quaternary ammonium mixtures. Although the percent organic modifier–water profiles were similar to those in previous studies with these compounds, resolution (R) and selectivity (?) parameters were found to be quite susceptible to changes in the mobile phase solvent composition. The retention behavior of the cationic analytes in the homologous series is consistent with the hydrophobic-interaction concept proposed for the retention mechanism via dominant inclusion complex formation. Several electrolytes were chosen for a study of the counter ion effect on the chromatographic characteristics of ABDAC components. Among the electrolytes examined, the perchlorate ion was found most likely to act as an ion-pairing counter ion for ammonium cations in the HPLC system studied. A correlation study established linear relationships between the chain length of ABDAC and the logarithmic capacity factor (k2). The analytical utility of the HPLC method was demonstrated by the analysis of various unknown mixtures.

Abidi, S. L.

1986-01-01

396

Kinetics of tethering quaternary ammonium compounds to K(+) channels.  

PubMed

Polymeric maleimido-quaternary ammonium (QA) compounds have been shown to function as molecular tape measures when covalently tethered to external cysteine residues of a Shaker K(+) channel (Blaustein R.O., P.A. Cole, C. Williams, and C. Miller. 2000. Nat. Struct. Biol. 7:309-311). For sufficiently long compounds, the cysteine-maleimide tethering reaction creates a high concentration, at the channel's pore, of a TEA-like moiety that irreversibly blocks current. This paper investigates a striking feature of the maleimide-cysteine tethering kinetics. Strong blockers-those that induce substantial levels (>80%) of irreversible inhibition of current-react with channel cysteines much more rapidly than weak blockers and, when delivered to channels with four cysteine targets, react with multiexponential kinetics. This behavior is shown to arise from the ability of a strong blocker to concentrate its maleimide end near a channel's cysteine target by exploiting the reversible pore-blocking affinity of its QA headgroup. PMID:12149281

Blaustein, Robert O

2002-08-01

397

Epiguruk: a late Quaternary environmental record from northwestern Alaska  

USGS Publications Warehouse

Epiguruk, a prominent bluff along the Kobuk River in northwestern Alaska, exposes a rich depositional record of Quaternary eolian and fluvial sand, with associated loess, paleosols, and periglacial features. Three major complexes of alluvial and eolian deposits are separated by two conspicuous organic-rich paleosols which formed during cool-moist interstadial intervals. Sediments between the two paleosols include eolian, channel, and floodplain deposits that formed during alluviation of the Kobuk River to a height of about 12m above the present level. The youngest depositional complex, which overlies the upper paleosol, is divisible into late Wisconsinan and Holocene components and into fluvial-channel, flood-plain, eolian-dune, sand-sheet, loess, and pond facies. Eolian sand from the active Kobuk sand sea overloaded the river during late Wisconsinan time, causing it to alluviate to about 13m above its modern level. The Holocene record reflects erosion and deposition by a small southern Tributary to the Kobuk River, downcutting by the Kobuk River toward its modern level, and subsequent erosion across a meander belt nearly 8km wide. 66 radiocarbon ages, many from rooted shrubs, provide a firm chronology for the past 35 k.y. at Epiguruk. -from Authors

Hamilton, T. D.; Ashley, G. M.

1993-01-01

398

Mucoadhesive nanoparticles made of thiolated quaternary chitosan crosslinked with hyaluronan.  

PubMed

Mucoadhesive polymeric nanoparticles intended for drug transport across the gastrointestinal mucosa were prepared from quaternary ammonium-chitosan conjugates synthesised from reduced-MW chitosan (32 kDa). Conjugates contained pendant moieties of 2-4 adjacent diethyl-dimethylene-ammonium groups substituted on repeating units (26-55%). Conjugates were thiolated via amide bonds with thioglycolic acid to yield products with thiol content in the 35-87 ?mol/g range. Nanoparticles with mean size in the 270-370 nm range and positive zeta-potential (+3.7 to +12.5 mV) resulted from ionotropic gelation of the thiolated conjugates with de-polymerised hyaluronic acid (470 kDa). The nanoparticles were fairly stable in size and thiol content and showed a significant mucoadhesivity, matching and even exceeding that of the constituent polymers. Nanoparticles were internalised by endothelial progenitor cells in direct relation to their surface charge intensity. Nanoparticle uptake significantly improved cell viability and resistance to oxidation. The lyophilised nanoparticles were re-dispersible and could make a manageable formulation for oral use. PMID:23218262

Zambito, Ylenia; Felice, Francesca; Fabiano, Angela; Di Stefano, Rossella; Di Colo, Giacomo

2013-01-30

399

Antibacterial Nanocomposite with Calcium Phosphate and Quaternary Ammonium  

PubMed Central

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 nanocomposite contained NACP and reinforcement glass fillers, with QADM in the resin. Two commercial composites were tested as controls. Composites were inoculated with Streptococcus mutans. After 180-day water-aging, NACP+QADM nanocomposite had flexural strength and elastic modulus matching those of commercial controls (p > 0.1). NACP+QADM nanocomposite reduced the biofilm colony-forming units (CFU) by 3-fold, compared with commercial composites (p < 0.05). Metabolic activity and lactic acid production of biofilms on NACP+QADM were much less than those on commercial composites (p < 0.05). The antibacterial properties of NACP+QADM were maintained after water-aging for 30, 90, and 180 d (p > 0.05). In conclusion, the novel NACP-QADM nanocomposite greatly decreased biofilm metabolic activity, CFU, and lactic acid, while matching the load-bearing capability of commercial composites without antibacterial properties. The NACP-QADM nanocomposite with strong and durable antibacterial properties, together with its previously reported Ca-PO4 release capability, may render it useful for caries-inhibiting restorations.

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

2012-01-01

400

Quaternary glaciation of the Tashkurgan Valley, Southeast Pamir  

NASA Astrophysics Data System (ADS)

The Quaternary glacial history of Tashkurgan valley, in the transition between the Pamir and Karakoram, in Xinjiang Province, China was examined using remote sensing, field mapping, geomorphic analysis of landforms and sediments, and 10Be terrestrial cosmogenic nuclide dating. Moraines were assigned to four glacial stages: 1) the Dabudaer glacial stage that dates to the penultimate glacial cycle and/or earlier, and may represent one or more glaciations; 2) the Tashkurgan glacial stage that dates to early last glacial, most likely Marine Oxygen Isotope Stage (MIS) 4; 3) the Hangdi glacial stage that dates to MIS 2, possibly early MIS 2; and 4) the Kuzigun glacial stage that dates to the MIS 2, possibly the global Last Glacial Maximum, and is younger than the Hangdi glacial stage. Younger moraines and rock glaciers are present at the heads of tributary valleys; but these were inaccessible because they are located close to politically sensitive borders with Pakistan, Afghanistan and Tajikistan. Glaciers during the Dabudaer glacial stage advanced into the central part of the Tashkurgan valley. During the Tashkurgan glacial stages, glaciers advanced several kilometers beyond the mouths of the tributary valleys into the Tashkurgan valley. Glaciers during the Hangdi and Kuzigun glacial stages advanced just beyond the mouths of the tributary valleys. Glaciation in this part of the Himalayan-Tibetan orogen is likely strongly controlled by northern hemisphere climate oscillations, although a monsoonal influence on glaciation cannot be ruled out entirely.

Owen, Lewis A.; Chen, Jie; Hedrick, Kathyrn A.; Caffee, Marc W.; Robinson, Alexander C.; Schoenbohm, Lindsay M.; Yuan, Zhaode; Li, Wenqiao; Imrecke, Daniel B.; Liu, Jinfeng

2012-07-01

401

The position of the gulf stream during quaternary glaciations.  

PubMed

Ocean general circulation theories predict that the position of the boundary between subtropical and subpolar gyres (and therefore the position of the Gulf Stream-North Atlantic Current system and the subpolar-subtropical front) is set by the line of zero "Ekman pumping," where there is no convergence or divergence of water in the directly wind-forced surface layer of the ocean. In the present-day North Atlantic Ocean this line runs southwest to northeast, from off the Carolinas to off Ireland. However, during the last ice age (18,000 years ago) the subpolar-subtropical boundary ran more zonally, directly toward Gibraltar. A numerical atmospheric general circulation model indicates that the field of Ekman pumping 18,000 years ago was modified by the presence of a continental ice cap more than 3 kilometers thick such that the line of zero Ekman pumping overlaid the paleogyre boundary. These results demonstrate that the presence of a thick continental ice sheet could have caused changes in sea surface temperatures in the North Atlantic during Quaternary glaciations by altering wind patterns. PMID:17792608

Keffer, T; Martinson, D G; Corliss, B H

1988-07-22

402

Enhanced adsorption of quaternary amine using modified activated carbon.  

PubMed

This study examined different methodologies to modify activated carbon (AC) for the removal of quaternary amine, tetramethylammonium hydroxide (TMAH), from water. Commercial carbon (WAC) was treated by nitric acid oxidation (NA-WAC), silica impregnation (SM-WAC0.5), and oxygen plasma (P10-WAC), and their characteristics and adsorption capacity were compared. The Langmuir model fitted the equilibrium adsorption data well under different pH. The maximum adsorption capacity of WAC was 27.77 mg/g, while those of NA-WAC, SM-WAC 0.5, and P10-WAC were 37.46, 32.83 and 29.03 mg/g, respectively. Nitric acid oxidation was the most effective method for enhancing the adsorption capacity of TMAH. Higher pH was favorable for TMAH adsorption. Desorption study revealed that NA-WAC had no considerable reduction in performance even after five cycles of regeneration by 0.1 N hydrochloric acid. It was proposed that electrostatic interaction was the main mechanism of TMAH adsorption on activated carbon. PMID:24845325

Prahas, Devarly; Wang, M J; Ismadji, Suryadi; Liu, J C

2014-01-01

403

Cellular uptake of polyurethane nanocarriers mediated by gemini quaternary ammonium.  

PubMed

The effective passage of drug formulations into tumor cells is a key factor in the development of nanoscale delivery systems. However, rapid cellular uptake with reduced toxicity remains a great challenge for efficient and safe delivery. In this study, we first use gemini quaternary ammonium (GQA) as a cell internalization promoter to enhance the cellular uptake of drug nanocarriers. It is found that a twenty times faster cell internalization could be achieved by introducing GQA into biodegradable multiblock polyurethane nanomicelles, as confirmed by flow cytometry and confocal laser scanning microscopy (CLSM) studies. Meanwhile, an added methoxyl-poly(ethylene glycol) (mPEG) outer corona could protect these cationic micelles from cytotoxicity at high concentrations, as verified by methyl tetrazolium (MTT) assay. Moreover, GQA not only acts as an enhancer for rapid cellular entry, but also plays an important role in controlled self-assembly and high drug loading capacity. Our work offers a new understanding on the role of cationic surfactants; and provides a facile and economical approach for the design of versatile drug nanocarriers to achieve efficient delivery and good biocompatibility. PMID:21907404

Ding, Mingming; He, Xueling; Wang, Zhigao; Li, Jiehua; Tan, Hong; Deng, Hua; Fu, Qiang; Gu, Qun

2011-12-01

404

Possible Late Quaternary faulting in the Benton Hills, southeastern Missouri  

SciTech Connect

Geologic mapping in the 1930's by Dan Stewart and Lyle McManamy identified numerous faults in the Thebes Gap area of the Benton Hills, including two post-late Quaternary faults (max. of 10 m displacement) along the southeastern escarpment. Recent geologic mapping (Richard Harrison, pers. comm.) suggests dextral strike-slip displacement on most of these faults; some deformation post-dates the Pliocene-Pleistocene Mounds gravel. Small historical earthquake epicenters have been recorded in the Benton Hills area. Review of these data and analysis of the geologic and structural relationships to small- and large-scale drainage and alluvial features suggest tectonic control of the southeastern escarpment of the Benton Hills. The authors propose the coincidence of geologic structures and landforms resembles tectonically active alluvial basin margins, with the Benton Hills southeastern margin representing a fault block uplift escarpment. Future seismic reflection, drilling and trenching studies are planned to determine if the escarpment is fault controlled and of recent origin.

Palmer, J.R.; Hoffman, D. (Missouri Geological Survey Program, Rolla, MO (United States). Dept. of Natural Resources)

1993-03-01

405

Effects of quaternary ammonium chain length on antibacterial bonding agents.  

PubMed

The objectives of this study were to synthesize new quaternary ammonium methacrylates (QAMs) with systematically varied alkyl chain lengths (CL) and to investigate, for the first time, the CL effects on antibacterial efficacy, cytotoxicity, and dentin bond strength of bonding agents. QAMs were synthesized with CL of 3 to 18 and incorporated into Scotchbond Multi-Purpose (SBMP) bonding agent. The cured resins were inoculated with Streptococcus mutans. Bacterial early attachment was investigated at 4 hrs. Biofilm colony-forming units (CFU) were measured after 2 days. With CL increasing from 3 to 16, the minimum inhibitory concentration and minimum bactericidal concentration were decreased by 5 orders of magnitude. Incorporating QAMs into SBMP reduced bacterial early attachment, with the least colonization at CL = 16. Biofilm CFU for CL = 16 was 4 log lower than SBMP control (p < .05). All groups had similar dentin bond strengths (p > .1). The new antibacterial materials had fibroblast/odontoblast viability similar to that of commercial controls. In conclusion, increasing the chain length of new QAMs in bonding agents greatly increased the antibacterial efficacy. A reduction in Streptococcus mutans biofilm CFU by 4 log could be achieved, without compromising bond strength and cytotoxicity. New QAM-containing bonding agents are promising for a wide range of restorations to inhibit biofilms. PMID:23958761

Li, F; Weir, M D; Xu, H H K

2013-10-01

406

Quaternary climate change and the geographic ranges of mammals.  

PubMed

A species' range can be a proxy for its ecological well-being. Species with small and shrinking range distributions are particularly vulnerable to extinction. Future climate change scenarios are predicted to affect species' geographical extents, but data on how species' distributions respond to changing climate are largely anecdotal, and our understanding of the determinants and limits to species geographic ranges is surprisingly poor. Here we show that mammal species in more historically variable environments have larger geographical ranges. However, the relationship between range size and long-term climate trends cannot be explained by variation in our estimates of habitat specificity. We suggest that large oscillations in Quaternary temperatures may have shaped the contemporary distribution of range sizes via the selective extirpation of small-ranged species during glacial expansion and/or recolonization by good dispersers after glacial retreats. The effect of current climate change on species' distributions and extinctions may therefore be determined by the geographical coincidence between historical and future climate scenarios, the "mesh size" of the extinction/dispersal filter imposed by past climate change, and whether similar ecological and evolutionary responses to historical climatic change are appropriate in an increasingly transformed and fragmented landscape. PMID:19627231

Davies, T Jonathan; Purvis, Andy; Gittleman, John L

2009-09-01

407

Late Quaternary environments, vegetation and agriculture in northern New Zealand  

NASA Astrophysics Data System (ADS)

A sedimentological and plant microfossil history of the Late Quaternary is preserved in two sediment cores from early Polynesian ditch systems on southern Aupouri Peninsula. The study places human activities into a geomorphological and ecological context and allows comparison of natural and anthropogenic effects on two different geological settings: a floodplain and a relatively closed peat swamp. The data fill part of the current gap in the environmental record from northern New Zealand, namely MIS 3 (57k-26k yr BP). There is evidence for an increase in fire frequency in the region after 40k 14C yr BP, suggesting a shift to drier (and cooler) conditions. Pollen records show that conifer-hardwood forest dominated by podocarps (especially Dacrydium) prevailed prior to Polynesian arrival and deforestation within the last millennium, with Fuscopsora insignificant throughout. Both cores show sections with gaps in deposition or preservation, possible flood-stripping of peat during the pre-Holocene and mechanical disturbance by early Polynesians. The identification of prehistoric starch grains and other microremains of introduced Colocasia esculenta (taro) in both cores supports indirect evidence that the ditch systems of far northern New Zealand were used for the extensive cultivation of this crop. Copyright

Horrocks, M.; Nichol, S. L.; Augustinus, P. C.; Barber, I. G.

2007-03-01

408

Tertiary and quaternary allostery in tetrameric hemoglobin from Scapharca inaequivalvis.  

PubMed

The clam Scapharca inaequivalvis possesses two cooperative oxygen binding hemoglobins in its red cells: a homodimeric HbI and a heterotetrameric A2B2 HbII. Each AB dimeric half of HbII is assembled in a manner very similar to that of the well-studied HbI. This study presents crystal structures of HbII along with oxygen binding data both in the crystalline state and in wet nanoporous silica gels. Despite very similar ligand-linked structural transitions observed in HbI and HbII crystals, HbII in the crystal or encapsulated in silica gels apparently exhibits minimal cooperativity in oxygen binding, in contrast with the full cooperativity exhibited by HbI crystals. However, oxygen binding curves in the crystal indicate the presence of a significant functional inequivalence of A and B chains. When this inequivalence is taken into account, both crystal and R state gel functional data are consistent with the conservation of a tertiary contribution to cooperative oxygen binding, quantitatively similar to that measured for HbI, and are in keeping with the structural information. Furthermore, our results indicate that to fully express cooperative ligand binding, HbII requires quaternary transitions hampered by crystal lattice and gel encapsulation, revealing greater complexity in cooperative function than the direct communication across a dimeric interface observed in HbI. PMID:23458680

Ronda, Luca; Bettati, Stefano; Henry, Eric R; Kashav, Tara; Sanders, Jeffrey M; Royer, William E; Mozzarelli, Andrea

2013-03-26

409

Parathyroid adenoma with coeliac disease: primary or quaternary hyperparathyroidism?  

PubMed

Coeliac disease is a gluten-sensitive enteropathy of varying severity. Osteomalacia and hypocalcaemia can result from malabsorption of vitamin D and calcium, which, in turn, can lead to secondary hyperparathyroidism. If coeliac disease remains untreated for long, tertiary hyperparathyroidism can also develop through autonomy of the parathyroid glands via chronic stimulation. Primary hyperparathyroidism also has been reported in some cases of coeliac disease. We report the case of an adolescent with coeliac disease presenting with severe hypercalcaemia from a parathyroid adenoma. A 14 year-old girl was admitted to our department for delayed puberty and growth retardation. Laboratory examination revealed iron deficiency anaemia, low 25OH vitamin D level (7 ng/ml), high parathyroid hormone level (PTH) (955 pg/ml), and hypercalcaemia (13.4 mg/dl). Endoscopic biopsy was compatible with gluten enteropathy. Endomysium antibody was positive. A gluten-free diet was started. Her calcium returned to normal after excision of the parathyroid adenoma. After four months of the gluten-free diet, she began to mature, and puberty began with development of breasts and axillary-pubic hair growth. It has been suggested that autonomous four-gland hyperplasia or tertiary hyperparathyroidism may progress to adenoma formation, and that this should be termed "quaternary hyperparathyroidism". More studies are required to explain the relationship between coeliac disease and hyperparathyroidism. PMID:22378099

Anaforoglu, Inan; Ersoy, Kerem; Algun, Ekrem

2012-01-01

410

Antibacterial nanocomposite with calcium phosphate and quaternary ammonium.  

PubMed

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 nanocomposite contained NACP and reinforcement glass fillers, with QADM in the resin. Two commercial composites were tested as controls. Composites were inoculated with Streptococcus mutans. After 180-day water-aging, NACP+QADM nanocomposite had flexural strength and elastic modulus matching those of commercial controls (p > 0.1). NACP+QADM nanocomposite reduced the biofilm colony-forming units (CFU) by 3-fold, compared with commercial composites (p < 0.05). Metabolic activity and lactic acid production of biofilms on NACP+QADM were much less than those on commercial composites (p < 0.05). The antibacterial properties of NACP+QADM were maintained after water-aging for 30, 90, and 180 d (p > 0.05). In conclusion, the novel NACP-QADM nanocomposite greatly decreased biofilm metabolic activity, CFU, and lactic acid, while matching the load-bearing capability of commercial composites without antibacterial properties. The NACP-QADM nanocomposite with strong and durable antibacterial properties, together with its previously reported Ca-PO(4) release capability, may render it useful for caries-inhibiting restorations. PMID:22403412

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

2012-05-01

411

N-methyl-citalopram: A quaternary selective serotonin reuptake inhibitor.  

PubMed

We describe the synthesis and the pharmacological characterization of a new quaternary selective serotonin reuptake inhibitor (SSRI) N-methyl-citalopram (NMC) with periphery restricted action due to its inability to cross the blood brain barrier. NMC recognized and blocked the human platelet serotonin transporter (SERT) with similar affinity to that of citalopram as was evident from competition binding studies with [(3)H]citalopram and uptake studies with [(3)H]5-HT. In contrast, the affinity of NMC to rat brain SERT was 10-fold lower than its parent compound citalopram. Similarly to citalopram, NMC did not inhibit dopamine and noradrenaline uptake in rat brain synaptosomes at 10(-7)M as well as [(3)H]ketanserin binding to rat brain membranes at 10(-5)M, demonstrating its SSRI profile. A comparison of radioactivity retained in perfused mice brain following in vivo intraperitoneal injections of tritium-labeled NMC or citalopram showed that unlike citalopram, NMC did not penetrate the brain. Taken together, our observations suggest that N-methyl-citalopram is a selective serotonin reuptake inhibitor that does not penetrate the mouse brain. Epidemiological studies have suggested that chronic use of SSRI drugs may confer a protective effect against myocardial infarction (MI) apparently reflecting reduced platelet aggregation secondary to reduced platelet serotonin levels. N-methyl-citalopram may therefore have a potential as a new anti-platelet drug that does not cross the blood brain barrier and is thus devoid of the adverse CNS effects of SSRI drugs. PMID:20696140

Bismuth-Evenzal, Yona; Roz, Netta; Gurwitz, David; Rehavi, Moshe

2010-11-15

412

Localization and quaternary structure of the PKA RI? holoenzyme  

PubMed Central

Specificity for signaling by cAMP-dependent protein kinase (PKA) is achieved by both targeting and isoform diversity. The inactive PKA holoenzyme has two catalytic (C) subunits and a regulatory (R) subunit dimer (R2:C2). Although the RI?, RII?, and RII? isoforms are well studied, little is known about RI?. We show here that RI? is enriched selectively in mitochondria and hypothesized that its unique biological importance and functional nonredundancy will correlate with its structure. Small-angle X-ray scattering showed that the overall shape of RI?2:C2 is different from its closest homolog, RI?2:C2. The full-length RI?2:C2 crystal structure allows us to visualize all the domains of the PKA holoenzyme complex and shows how isoform-specific assembly of holoenzyme complexes can create distinct quaternary structures even though the R1:C1 heterodimers are similar in all isoforms. The creation of discrete isoform-specific PKA holoenzyme signaling “foci” paves the way for exploring further biological roles of PKA RI? and establishes a paradigm for PKA signaling.

Ilouz, Ronit; Bubis, Jose; Wu, Jian; Yim, Yun Young; Deal, Michael S.; Kornev, Alexandr P.; Ma, Yuliang; Blumenthal, Donald K.; Taylor, Susan S.

2012-01-01

413

Systematics of prompt ?-ray emission in fission  

NASA Astrophysics Data System (ADS)

The prompt ?-ray energy and multiplicity distributions were measured for the neutron-induced fission in 235U and 239,241Pu by using a highly segmented 4??-ray calorimeter in coincidence with the detection of fission fragments by a gas-filled parallel-plate avalanche counter. Both distributions were unfolded according to the detector response, which was simulated numerically by using a model validated with the ?-ray calibration sources. The mean value and the width of the ?-ray multiplicity distribution show a systematic increase with increasing mass of fissile nucleus, whereas, the energy distribution shows the dependence of ?-ray energy above 5 MeV on the species of fissile nuclei. The correlations between ?-ray energy and multiplicity were studied by comparing the mean value and the width of the total ?-ray energy between measurement and simulation by using an assembly with elements selected by random sampling of their unfolded distributions. The detector response was taken into account in the simulation. These results together with the detailed description of the experiment and analysis are presented.

Chyzh, A.; Wu, C. Y.; Kwan, E.; Henderson, R. A.; Gostic, J. M.; Bredeweg, T. A.; Couture, A.; Haight, R. C.; Hayes-Sterbenz, A. C.; Jandel, M.; Lee, H. Y.; O'Donnell, J. M.; Ullmann, J. L.

2013-03-01

414

Nuclear fission with mean-field instantons  

NASA Astrophysics Data System (ADS)

We present a description of nuclear spontaneous fission, and generally of quantum tunneling, in terms of instantons, that is, periodic imaginary-time solutions to time-dependent mean-field equations. This description allows comparisons to be made with the more familiar generator coordinate (GCM) and adiabatic time-dependent Hartree-Fock (ATDHF) methods. It is shown that the action functional whose value for the instanton is the quasiclassical estimate of the decay exponent fulfills the minimum principle when additional constraints are imposed on trial fission paths. In analogy with mechanics, these are conditions of energy conservation and the velocity-momentum relations. In the adiabatic limit, the instanton method reduces to the time-odd ATDHF equation, with collective mass including the time-odd Thouless-Valatin term, while the GCM mass completely ignores velocity-momentum relations. This implies that GCM inertia generally overestimates the instanton-related decay rate. The very existence of the minimum principle offers hope for a variational search for instantons. After the inclusion of pairing, the instanton equations and the variational principle can be expressed in terms of the imaginary-time-dependent Hartree-Fock-Bogoliubov (TDHFB) theory. The adiabatic limit of this theory reproduces ATDHFB inertia.

Skalski, Janusz

2008-06-01

415

Fuel and fission product release from sodium  

SciTech Connect

The NALA program at Kernforschungszentrum Karlsruhe is concerned with the release of fuel and fission products from hot or boiling sodium pools (radiological secondary source term) in a liquid-metal fast breeder reactor accident scenario with tank failure. The main concern is to determine retention factors (RF), to uncover the most essential parameters that influence the RF values, and to describe the way they do it. In the framework of the last NALA series, NALA IIIc, the influence of sodium-concrete interaction was investigated, partly with subsequent sodium burning. In our experiments, [approx]3 kg of sodium and added pieces of concrete reaching from 4 to 40 g was used. The composition of the concrete was suitable for shielding and construction as used in the SNR-300 reactor. Fuel was simulated by 20-[mu]m particles of depleted UO[sub 2], and CeO[sub 2], NaI, and TeO[sub 2] were used as fission products. Most experiments were performed in an inert argon gas atmosphere with monitored hydrogen development. In some cases, the preheated pool was allowed to come into contact with ambient air, which caused an ordinary sodium fire. For the latter case, we used the 220-m[sup 3] FAUNA vessel as an outer containment and collected the fire aerosols by a trap and subsequent filters for analysis.

Sauter, H. (Kernforschungszentrum Karlsruhe (Germany))

1992-01-01

416

FYPO: the fission yeast phenotype ontology  

PubMed Central

Motivation: To provide consistent computable descriptions of phenotype data, PomBase is developing a formal ontology of phenotypes observed in fission yeast. Results: The fission yeast phenotype ontology (FYPO) is a modular ontology that uses several existing ontologies from the open biological and biomedical ontologies (OBO) collection as building blocks, including the phenotypic quality ontology PATO, the Gene Ontology and Chemical Entities of Biological Interest. Modular ontology development facilitates partially automated effective organization of detailed phenotype descriptions with complex relationships to each other and to underlying biological phenomena. As a result, FYPO supports sophisticated querying, computational analysis and comparison between different experiments and even between species. Availability: FYPO releases are available from the Subversion repository at the PomBase SourceForge project page (https://sourceforge.net/p/pombase/code/HEAD/tree/phenotype_ontology/). The current version of FYPO is also available on the OBO Foundry Web site (http://obofoundry.org/). Contact: mah79@cam.ac.uk or vw253@cam.ac.uk

Harris, Midori A.; Lock, Antonia; Bahler, Jurg; Oliver, Stephen G.; Wood, Valerie

2013-01-01

417

Telomere regulation during the cell cycle in fission yeast.  

PubMed

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

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

2014-01-01

418

Recent MELCOR and VICTORIA Fission Product Research at the NRC  

Microsoft Academic Search

The MELCOR and VICTORIA severe accident analysis codes, which were developed at Sandia National Laboratories for the U. S. Nuclear Regulatory Commission, are designed to estimate fission product releases during nuclear reactor accidents in light water reactors. MELCOR is an integrated plant-assessment code that models the key phenomena in adequate detail for risk-assessment purposes. VICTORIA is a more specialized fission-

N. E. Bixler; R. K. Cole; R. O. Gauntt; J. H. Schaperow; M. F. Young

1999-01-01

419

JNDC nuclear data library of fission products. Second version.  

National Technical Information Service (NTIS)

The second version of the JNDC (Japanese Nuclear Data Committee) FP (Fission Product) nuclear data library is described in this report. The library contains nuclear decay and fission yield data for 1078 unstable and 149 stable FP nuclides, and neutron cro...

K. Tasaka J. Katakura H. Ihara T. Nakagawa H. Takano

1990-01-01

420

Mitochondrial Morphological Features Are Associated with Fission and Fusion Events  

PubMed Central

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.

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

2014-01-01

421

Contribution a l'etude de la competition fission evaporation de particules dans la fission nucleaire consideree comme un processus de diffusion. (Particle evaporation-fission competition in nuclear fission considered as a diffusion process).  

National Technical Information Service (NTIS)

Nuclear fission is treated as a diffusion process in phase space corresponding to the essential collective variable of fission. The solution of the two-dimensional Fokker-Planck equation is used to obtain an escape rate over the collective potential barri...

S. Hassani

1983-01-01

422

Nuclear structure and dynamics from heavy - ion induced fission reactions  

NASA Astrophysics Data System (ADS)

The study of heavy - ion fusion and fission reactions at near - barrier energies continues to be a rich source of information as regards nuclear structure and dynamics. From a comprehensive statistical model analysis of the fusion and the fission data including information on the pre - scission neutrons, for a large number of compound nuclei with masses around 200, it has been possible to determine reliably the fission barrier, the nuclear moment of inertia and the shell correction at the saddle point. Interestingly, it is found that for the nuclei in the mass region around 200, a significantly large fraction of the ground state shell correction persists at the deformed saddle - point. Systematic measurements of the fission fragment angular distributions spanning a range of projectiles with A = 9 to 19, bombarding the Th,U and Np targets have clearly brought out role of the entrance channel dynamics involving a new type of non - equilibrium fission, which we call pre - equilibrium fission comempeting with the equilibrium compound nucleus fission. A new model which takes into account the deformation and the spin values of the target and the projectile, the orientation and the entrance channel mass asymmetry dependence of the interacting nuclei has been developed which provides a good description of the fission fragment angular distribution data both at above and below barrier energies.

Kailas, S.; Mahata, K.; Thomas, R. G.; Kapoor, S. S.

2007-05-01

423

Fusion-Fission Hybrids Driven By Heavy Ion Inertial Fusion  

Microsoft Academic Search

There is a desire to resolve fuel cycle issues for increasing the role of nuclear energy. The recent Laser Inertial Fusion-Fission Energy (LIFE) initiative that builds upon NIF ignition, is likely to rekindle national interest in developing intense, high power ion beam accelerators for fusion energy production and for fusion-fission hybrid concepts that combine an ion beam driven fusion neutron

P. A. Seidl

424

Microscopic calculations of the inertial mass parameter for fissioning nuclei  

Microsoft Academic Search

Inertia mass parameter B in a fissioning nucleus is calculated. The method of calculation is based on the assumption of adiabatic collective motion in the fission degree of freedom. Resulting values for B are 4 to 11 times larger than those obtained from the liquid-drop model estimates. It turns out that the inertial parameter increases almost linearly with nuclear deformation.

Adam Sobiczewski; Zdzislaw Szymanski; Slawomir Wycech; Sven Gösta Nilsson; James Rayford Nix; Chin Fu Tsang; Christer Gustafson; Peter Möller; Björn Nilsson

1969-01-01

425

Fission fragmentation effects on ion beam inertial fusion targets  

Microsoft Academic Search

The effects of preheat due to fission fragments is considered for a U-ion driven LiD-Pb-DT spherical target for various beam spot sizes and power levels. Fission effects are seen to reduce the D-T varrhor values by up to a factor 2 with a subsequent reduction in the target performance.

T. D. Beynon; E. H. Smith

1985-01-01

426

Giant vibration of fission fragments and concomitant electromagnetic radiation  

Microsoft Academic Search

Giant shape vibrations of fission fragments are described in a simple model which is based on nuclear transport theory. The friction and inertial parameters are calculated within the linear response and cranking theory, respectively. The initial conditions are chosen in the scission region following the conventional picture of the fission process at low energy. The emission of electromagnetic radiation by

J. Bartel; D. Boosé; K. Dietrich; K. Pomorski; J. Richert

1991-01-01

427

Fusion-Fission Hybrid for Fissile Fuel Production without Processing  

Microsoft Academic Search

Two scenarios are typically envisioned for thorium fuel cycles: 'open' cycles based on irradiation of ²³²Th and fission of ²³³U in situ without reprocessing or 'closed' cycles based on irradiation of ²³²Th followed by reprocessing, and recycling of ²³³U either in situ or in critical fission reactors. This study evaluates a third option based on the possibility of breeding fissile

M Fratoni; R W Moir; K J Kramer; J F Latkowski; W R Meier; J J Powers

2012-01-01

428

Fission-track ages from the Precambrian of Shropshire.  

USGS Publications Warehouse

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

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

1982-01-01

429

Whole-rock uranium analysis by fission track activation  

NASA Technical Reports Server (NTRS)

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.

Weiss, J. R.; Haines, E. L.

1974-01-01

430

Fission Product Iodine Carry-over from Experimental Apparatus.  

National Technical Information Service (NTIS)

Measurements of fission product iodine carry-over have been made on a small scale laboratory test unit at one atmosphere. Fission product iodine in the water having several chemical species such as I exp 0 , I exp - , I exp +5 , and organic, the carry-ove...

H. Tone S. Okagawa

1977-01-01

431

Patterns and barriers for fission of charged small metal clusters  

Microsoft Academic Search

Asymmetric fission of small doubly-charged sodium clusters, investigated via a local-spin-density molecular-dynamics method, is shown to occur predominantly via Na+2n-->Na+n-3+Na+3, for 4<=n<=12. For the smallest cluster (n8 exhibit a double-hump shape, and the dynamics of fission involves a precursor mechanism.

R. N. Barnett; Uzi Landman; Gunaretnam Rajagopal

1991-01-01

432

Long-Range Fission Fragments from Radiogenic Lead.  

National Technical Information Service (NTIS)

Fission tracks with a range 19 percent longer than tracks produced by uranium fission fragments were observed on mylar foils after a three-year underground (100 m.w.e.) exposure to 3600 cm exp 2 of radiogenic lead. Ordinary lead which was simultaneously e...

J. Maly D. R . Walz

1978-01-01

433

Vlasov treatment of spontaneous fission and sub-barrier fusion  

Microsoft Academic Search

We present a model towards the many-body description of spontaneous fission and sub-barrier fusion based on the semiclassical Vlasov equation and the Feynman path integral method. We define suitable collective variables from the Vlasov solution and use the imaginary time technique for the dynamics below the Coulomb barrier. Internal excitations in fission process and the effect of particle transfer in

A. Iwamoto; V. Kondratyev; A. Bonasera

1998-01-01

434

FAST FISSION IN LIGHT-WATER-MODERATED LATTICES  

Microsoft Academic Search

From the results or measurements of the ratios of the fission rates of U\\/; sup 238\\/ and U²³⁵ in light-water-moderated critical assemblies with ; slightly enriched fuel effective cross sections were derived, with whose help the ; fast fission factor in power reactors could be calculated. (tr-auth);

1963-01-01

435

A scintillating fission detector for neutron flux measurements  

Microsoft Academic Search

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

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

2010-01-01

436

Electroplating method for producing ultralow-mass fissionable deposits  

DOEpatents

A method for producing ultralow-mass fissionable deposits for nuclear reactor dosimetry is described, including the steps of holding a radioactive parent until the radioactive parent reaches secular equilibrium with a daughter isotope, chemically separating the daughter from the parent, electroplating the daughter on a suitable substrate, and holding the electroplated daughter until the daughter decays to the fissionable deposit.

Ruddy, Francis H. (Monroeville, PA)

1989-01-01

437

Fission foil detector calibrations with high energy protons  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

438

Search for spontaneous fission emitters in Atlantis II (Part II)  

Microsoft Academic Search

In this paper we describe an attempt to isolate superheavy elements from Atlantis II hot brine deposits. Volatile, sulfidic elements (Cd, Pb) were isolated and investigated for spontaneous fission events with a mica-plastic solid state track detector sandwich. During nearly two years exposure time no spontaneous fission activity was observed. The upper limit for the concentration of superheavy elements (following

T. Lund; R. Brandt; D. Molzahn; G. Tress; P. Vater; A. Marinov

1981-01-01

439

Single-particle spin effect on fission fragment angular momentum  

NASA Astrophysics Data System (ADS)

Independent isomeric yield ratios (IYR) of 128Sb, 130Sb, 132Sb, 131Te, 133Te, 132I, 134I, 136I, 135Xe, and 138Cs have been determined in the fast neutron-induced fission of 243Am using the radiochemical and ?-ray spectrometric technique. From the IYR, fragment angular momenta (J rms) have been deduced using the spin-dependent statistical model analysis. From the J rms-values and experimental kinetic energy data deformation parameters (?) have been deduced using the pre-scission bending mode oscillation model and the statistical model. The J rms- and ?-values of fission fragments from the present and earlier work in the odd-Z fissioning systems ( 238Np * , 242Am * and 244Am * ) are compared with the literature data in the even-Z fissioning systems ( 230, 233Th * , 233, 234, 236, 239U * , 239, 240, 241, 242Pu * , 244Cm(SF), 245, 246Cm * , 250Cf * and 252Cf(SF)) to examine the role of single-particle (proton) spin effect. It was observed that i) in all the fissioning systems J rms- and ?-values of the fragments with spherical 82n shell and even-Z products are lower than the fragments away from the spherical neutron shell and odd-Z products, which indicate the effect of nuclear structure. ii) For both even-Z and odd-Z fission products J rms-values increase with Z F 2/A F due to increase in Coulomb torque. iii) The J rms- and ?-values of even-Z fission products are comparable in all the fissioning systems. However, for odd-Z fission products they are slightly higher in the odd-Z fissioning systems compared to their adjacent even-Z fissioning systems. This is possible due to the contribution of the extra single-particle (proton) spin of the odd-Z fissioning systems to their odd-Z fragments. iv) The yield-weighted fragment angular momentum and elemental yields profile shows an anti-correlation in even-Z fissioning systems but not in the odd-Z fissioning systems.

Naik, H.; Dange, S. P.; Singh, R. J.; Reddy, A. V. R.

2007-02-01

440

Applications of Event-by-Event Fission Modeling with FREYA  

SciTech Connect

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. We first discuss the present status of FREYA, which has now been extended to include spontaneous fission. Concentrating on {sup 239}Pu(n{sub th},f), {sup 240}Pu(sf) and {sup 252}Cf(sf), 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 suggest novel fission observables that could be measured with modern detectors.

Vogt, R; Randrup, J

2011-09-16

441

Determining isotopic distributions of fission products with a Penning trap  

NASA Astrophysics Data System (ADS)

A novel method to determine independent yields in particle-induced fission employing the ion guide technique and ion counting after a Penning trap has been developed. The method takes advantage of the fact that a Penning trap can be used as a precision mass filter, which allows an unambiguous identification of the fission fragments. The method was tested with 25MeV and 50MeV proton-induced fission of 238U . The data is internally reproducible with an accuracy of a few per cent. A satisfactory agreement was obtained with older ion guide yield measurements in 25MeV proton-induced fission. The results for Rb and Cs yields in 50MeV proton-induced fission agree with previous measurements performed at an isotope separator equipped with a chemically selective ion source.

Penttilä, H.; Karvonen, P.; Eronen, T.; Elomaa, V.-V.; Hager, U.; Hakala, J.; Jokinen, A.; Kankainen, A.; Moore, I. D.; Peräjärvi, K.; Rahaman, S.; Rinta-Antila, S.; Rubchenya, V.; Saastamoinen, A.; Sonoda, T.; Äystö, J.

2010-04-01

442

Angular momentum effects in multimodal fission of {sup 226}Th  

SciTech Connect

The {gamma}-rays from the multimodal fission of the {sup 226}Th formed in {sup 18}O+{sup 208}Pb was investigated at the near- and sub-barrier energies. The corresponding excitation energies at the saddle point, E{sub sp}*, ranged from 23 to 26 MeV. The average {gamma}-ray multiplicities and relative {gamma}-ray energies as a function of the mass of the fission fragments exhibits a complex structure and strong variations. Such strong variations have never been previously observed in heavy ion-induced fusion-fission reactions. Obtained results may be explained with the influence of shell effects on the properties of the fission fragments. Present work is the one in series of investigation of the multimodal fission phenomena in At-Th region.

Chubarian, G. G.; Hurst, B. J.; O'Kelly, D.; Schmitt, R. P. [Cyclotron Institute, Texas A and M University, Texas 77843 (United States); Itkis, M. G.; Kondratiev, N. A.; Kozulin, E. M.; Oganessian, Yu. Ts.; Pashkevich, V. V.; Pokrovsky, I. V.; Salamatin, V. S. [FLNR, JINR, Dubna, Russia 141980 (Russian Federation); Rusanov, A. Ya. [INP, Alma-Ata (Kazakhstan); Calabretta, L.; Maiolino, C.; Lukashin, K.; Agodi, C.; Bellia, G. [LNS-INFN, 57 Corso Italia, I-95100, Catania (Italy); Hanappe, F. [ULB, PNTPM CP229, av. F.D. Roosewelt, B1050, Brussels (Belgium); Liatard, E. [ISN, 53 avenue des Martyrs, 38026, Grenoble, Cedex (France); Huck, A. [CRN, 23, rue du Loess, 67037 Strasbourg, Cedex 2 (France)] (and others)

1998-12-21

443

Angular momentum effects in multimodal fission of {sup 226}Th  

SciTech Connect

The {gamma}-rays from the multimodal fission of the {sup 226}Th formed in {sup 18}O+{sup 208}Pb was investigated at the near- and sub-barrier energies. The corresponding excitation energies at the saddle point, E{sub sp}{sup {asterisk}}, ranged from 23 to 26 MeV. The average {gamma}-ray multiplicities and relative {gamma}-ray energies as a function of the mass of the fission fragments exhibits a complex structure and strong variations. Such strong variations have never been previously observed in heavy ion-induced fusion-fission reactions. Obtained results may be explained with the influence of shell effects on the properties of the fission fragments. Present work is the one in series of investigation of the multimodal fission phenomena in At-Th region. {copyright} {ital 1998 American Institute of Physics.}

Chubarian, G.G.; Hurst, B.J.; OKelly, D.; Schmitt, R.P. [Cyclotron Institute, Texas AM University, Texas 77843 (United States); Itkis, M.G.; Kondratiev, N.A.; Kozulin, E.M.; Oganessian, Y.T.; Pashkevich, V.V.; Pokrovsky, I.V.; Salamatin, V.S. [FLNR, JINR, Dubna, (Russia) 141980; Rusanov, A.Y. [INP, Alma-Ata (Kazakhstan); Calabretta, L.; Maiolino, C.; Lukashin, K.; Agodi, C.; Bellia, G. [LNS-INFN, 57 Corso Italia, I-95100, Catania (Italy); Hanappe, F. [ULB, PNTPM CP229, av. F.D. Roosewelt, B1050, Brussels (Belgium); Liatard, E. [ISN, 53 avenue des Martyrs, 38026, Grenoble, Cedex (France); Huck, A.; Stuttge, L. [CRN, 23, rue du Loess, 67037 Strasbourg, Cedex 2 (France)

1998-12-01

444

Colloquium: Beta-delayed fission of atomic nuclei  

NASA Astrophysics Data System (ADS)

This Colloquium reviews the studies of exotic type of low-energy nuclear fission, the ?-delayed fission (?DF). Emphasis is made on the new data from very neutron-deficient nuclei in the lead region, previously scarcely studied as far as fission is concerned. These data establish the new region of asymmetric fission in addition to the previously known one in the transuranium nuclei. New production and identification techniques, which emerged in the last two decades, such as the wider use of electromagnetic separators and the application of selective laser ionization to produce intense isotopically or even isomerically pure radioactive beams are highlighted. A critical analysis of presently available ?DF data is presented and the importance of detailed quantitative ?DF studies, which become possible now, is stressed, along with the recent theory efforts in the domain of low-energy fission.

Andreyev, Andrei N.; Huyse, Mark; Van Duppen, Piet

2013-10-01

445

Gravity anomalies, Quaternary vents, and Quaternary faults in the southern Cascade Range, Oregon and California: Implications for arc and backarc evolution  

USGS Publications Warehouse

Isostatic residual gravity anomalies in the southern Cascade Range of northern California and southern Oregon are spatially correlated with broad zones of Quaternary magmatism as reflected by the total volume of Quaternary volcanic products, the distribution of Quaternary vents, and the anomalously low teleseismic P wave velocities in the upper 30 km of crust. The orientation of Quaternary faults also appears to be related to gravity anomalies and volcanism in this area, trending generally north-south within the magmatic regions and northwest-southeast as they enter the neighboring amagmatic zones to the north and south. The relationship between gravity anomalies, vent density, and fault orientations may indicate in a broad sense the strength of the middle and upper crust. The southern Cascade Range occupies a transition zone where horizontal stress is transferred from the northwest-southeast dextral shear of the Walker Lane belt to the east-west extension characteristic of the Cascade arc in central Oregon. Faulting along north-south strikes in the volcanically active areas indicates the east-west extensional stresses in thermally weakened crust, whereas northwest faulting between the volcanically active areas reflects the northwest trending, right lateral shear strain of the Walker Lane belt. The segmentation of the arc reflected in Quaternary magmatism may be caused by differential extension behind crustal blocks of the forearc rotating clockwise with respect to North America. In this view the volcanic centers at Mount Shasta, Medicine Lake volcano, and Lassen Peak in northern California are situated along the southern parts of the trailing edges of two distinct segments of the forearc where additional extension is implied by their differential clockwise rotation. U.S. copyright. Published in 1997 by the American Geophysical Union.

Blakely, R. J.; Christiansen, R. L.; Guffanti, M.; Wells, R. E.; Donnelly-Nolan, J. M.; Patrick, Muffler, L. J.; Clynne, M. A.; Smith, J. G.

1997-01-01

446

Projectile fission of (sup 238)U relativistic ions in a Pb target and discovery of new fission fragments.  

National Technical Information Service (NTIS)

The authors have measured the cross sections for the production of fission fragments in the fission of 750 A.MeV (sup 238)U ions colliding with a Pb target. Several new neutron-rich isotopes have been discovered by this process. (HSI) (ERA citation 19:026...

M. Bernas S. Czajkowski P. Armbruster H. Geissel P. Dessagne

1994-01-01

447

Etude de la fission thermique tres asymetrique de (sup 235)U. (Study of (sup 235)U very asymmetric thermal fission).  

National Technical Information Service (NTIS)

The fission fragment separator Lohengrin of the Institut Laue-Langevin in Grenoble was used to determine the yields of the very asymmetric light fission products (A=84-69) as a function of A, Z, and the kinetic energy E. The proton pairing effect causes f...

J. L. Sida

1989-01-01

448

Fission fragment yields in the fission of 232Th by protons of energies 8 to 22 MeV  

NASA Astrophysics Data System (ADS)

Excitation functions of fission products for 22 fragment masses and neutron-evaporation products, (p,n), (p,2n) and (p,3n) were measured in detail for the system of 232Th+p in the proton energy range of 8 to 22 MeV. It was found that the excitation functions of symmetrically divided fission fragments were apparently different from those of asymmetrically divided ones. For the interpretation of the experimental results, a statistical evaporation-and-fission calculation was performed by taking into consideration symmetric and asymmetric fission barriers. The experimental data could be reproduced by this statistical calculation, with fission barrier heights that were in accord with the reported experimental ones for the asymmetric fragments and the theoretically predicted one for the symmetric mass division. The level density parameter at the symmetric saddle had to be about 13% larger than that for the asymmetric saddle in order to reproduce the energy dependence of the cross section ratios of asymmetric to symmetric product yields. NUCLEAR REACTIONS, FISSION 232Th(p,f), Ep=8-22 MeV, stacked-foil method, excitation functions of fission products and neutron-evaporation products, statistical calculation, symmetric and asymmetric fission barriers.

Kudo, H.; Muramatsu, H.; Nakahara, H.; Miyano, K.; Kohno, I.

1982-06-01

449

Paleovalley systems: Insights from Quaternary analogs and experiments  

NASA Astrophysics Data System (ADS)

Ancient fluvial valley systems are long recognized as important features in the stratigraphic record, but emerged as a specific focus of attention with publication of first-generation sequence-stratigraphic concepts. This paper reviews current understanding of paleovalley systems from the perspective of Quaternary analogs and experimental studies. Paleovalley systems can include distinct mixed bedrock-alluvial, coastal-plain, and cross-shelf segments. Mixed bedrock-alluvial segments are long-lived, cut across bedrock of significantly older age, and have an overall degradational architecture. By contrast, coastal-plain and cross-shelf segments are non-equilibrium responses to high-frequency cycles of relative sea-level change: most coastal-plain and cross-shelf segments form as a geometric response to relative sea-level fall, as river systems cut through coastal-plain and inner shelf clinothems, and extend basinward to track the shoreline. After incision and cross-shelf extension, lateral channel migration and contemporaneous channel-belt deposition creates a valley-scale feature. Coastal-plain and cross-shelf paleovalley widths are set by the number of channel-belt sandbodies deposited during this time. Paleovalley systems play a key role in source-to-sink sediment routing. Early views included the model of incision and complete sediment bypass in response to relative sea-level fall. However, this model does not stand up to empirical, theoretical, or experimental scrutiny. Instead, there is a complex dynamic between incision, deposition, and sediment export from an evolving valley: periods of incision correspond with sediment export minima, whereas periods of lateral migration and channel-belt construction result in increased flux to the river mouth. Sediment export from evolving valleys, and merging of drainages during cross-shelf transit, play key roles in sediment transfer to the shelf-margin and genetically-linked slope to basin-floor systems. Connection between the river mouth and the shelf margin likely occurs for different periods of time depending on gradient of the river and shelf, as well as amplitude of high-frequency sea-level changes. Late Quaternary analogs and experimental studies provide an alternative sequence-stratigraphic interpretation for paleovalley systems. In coastal-plain paleovalleys, basal valley-fill surfaces meet criteria for an unconformity and a classically-defined sequence boundary: however, this surface is mostly everywhere of the same age as overlying fluvial deposits, and does not correspond to a long period of incision and sediment bypass. In cross-shelf paleovalleys, the basal contact between fluvial and deltaic or shoreface deposits is commonly interpreted as a sequence boundary, but is not an unconformity characterized by incision and sediment bypass. Instead, this surface is a facies contact that separates genetically-related fluvial and deltaic strata: the surface that correlates to the basal valley-fill surface within the coastal-plain paleovalley dips below cross-shelf prograding deltaic and/or shoreface strata, which are fed by deposition within the evolving valley itself, and should be the downlap surface. Many issues deserve attention in the future. We have stressed understanding the inherent scales and physical processes that operate during the formation and evolution of paleovalley systems. We also suggest the relative roles of allogenic forcing vs. autogenic dynamics, and the potential significance of high-frequency isostatic adjustments should be topics for future discussion.

Blum, M.; Martin, J.; Milliken, K.; Garvin, M.

2013-01-01

450

Mapping the late Quaternary evolution of the lower Mississippi Valley  

NASA Astrophysics Data System (ADS)

The lower Mississippi Valley (LMV) extends from Cape Girardeau to Natchez and from Little Rock to Memphis. Extensive Quaternary terraces within the LMV have been considered to reflect downstream changes in base level (global sea level) and (or) upstream changes in water and sediment input because of glaciation. We suggest that the first-order control on terrace development was glacial-isostatic adjustment (GIA). Observed variation in heights of Quaternary alluvial surfaces at Memphis is 50 m (Rittenour et al., 2007). GIA modeling by Clark et al. (1994) predicted vertical displacement of as much as 130 m at Memphis over the last 18,000 years. ICE-5G models predict smaller displacement and reinforce the viability of GIA as the primary cause of LMV aggradation and incision. Existing analyses of LMV terraces are built on geomorphic maps by Saucier and colleagues (1974, 1994; Autin et al., 1991) that were interpreted from aerial photographs and inch-to-the-mile contour maps. Geomorphic mapping from high-resolution DEMs is more accurate, more rapid, and more reproducible than mapping from aerial photography and intermediate-resolution contours. Working from lidar DEMs (1-5 m XY resolution) and the 10 m National Elevation Dataset (NED) DEM largely derived from 1:24,000 scale contours, Haugerud is mapping the geomorphology of the LMV at ~1:500,000 scale. Goals are to explore the GIA-terrace hypothesis and improve the geomorphic and stratigraphic context for studies of New Madrid seismicity. Mapping leads to several observations: 1. The Holocene floodplain of the Miss