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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

Fission  

NASA Astrophysics Data System (ADS)

The breaking apart of a body into smaller fragments. In the context of nuclear physics the term, nuclear fission, refers to the splitting of a heavy atomic nucleus into two or more lighter nuclei with the release of energy. The mass of the nucleus prior to fission is greater than the combined masses of the fragments, the difference in mass, ?m, being released as a quantity of energy, ?E (?E=?mc2,...

Murdin, P.

2000-11-01

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

Plio-Quaternary exhumation history of the central Nepalese Himalaya: 1. Apatite and zircon fission track and apatite [U-Th]\\/He analyses  

Microsoft Academic Search

New apatite and zircon fission track and (U-Th)\\/He analyses serve to document the bedrock cooling history of the central Nepalese Himalaya near the Annapurna Range. We have obtained 82 apatite fission track (AFT), 7 zircon fission track (ZFT), and 7 apatite (U-Th)\\/He (AHe) ages from samples collected along the Marsyandi drainage, including eight vertical relief profiles from ridges on either

A. E. Blythe; D. W. Burbank; A. Carter; K. Schmidt; J. Putkonen

2007-01-01

5

Deciphering Past and Present Tectonics of the Rio Grande Rift in New Mexico Utilizing Apatite Fission Track Thermochronology, Geochronology, Quaternary Faulting, and Cross-Section Restoration  

NASA Astrophysics Data System (ADS)

The Rio Grande rift provides an excellent laboratory for understanding styles and processes of extensional tectonics, and their driving forces. We apply apatite fission track (AFT) thermochronology, geochronology, fracture analysis, and cross-section restoration to decipher past and present tectonics of the Rio Grande rift. AFT data has been compiled from rift flank uplifts along the Rio Grande rift in an attempt to recognize long wavelength spatial and temporal patterns. AFT ages record time of cooling of rocks below ~110°C and, when cooling is due to exhumation, age elevation traverses can record upward advection of rocks through paleo 110°C isotherms. The relatively passive sides of half-grabens (e.g. Manzanos and Santa Fe Range) preserve Laramide AFT ages ranging from 45-70 Ma, indicating they were cooled during the Laramide Orogeny and have remained cooler than 110°C since then. Rift flanks on the tectonically active sides of half-grabens, (e.g. Sierra Ladrones, Sandias, Taos Range, and Sierra Blanca) have AFT ages that range from 35 Ma to <10 Ma, and record cooling that initiated with the Oligocene ignimbrite flare-up and continues through the Neogene. Our analysis tracks the approximate elevation of paleo 110°C isotherms in 10 Ma intervals from the Laramide to the present and shows that reconstructed paleoisotherms have been differentially uplifted, warped, and faulted since their time of formation, and hence serve as markers of uplift history and its mechanisms. AFT data at Ladron Peak, an active rift flank along the western margin of the Rio Grande rift in central New Mexico, indicates that it was rapidly unroofed between 20-10 Ma. Preliminary apatite helium data gives a similar age vs. elevation trend, but apatites have highly radiogenically damaged lattices and hence have corrected closure temperatures tens of degrees higher than AFT ages. The style of faulting at Ladron Peak is unusual because it is bounded by the anomalously low-angle (~15°) Jeter fault. In order to understand the evolution of faulting in this region, a balanced cross-section was constructed and restored to its pre-rift geometry. Our working hypothesis is that the low angle of the Jeter fault is most adequately explained by a rolling hinge model, where isostatic uplift causes progressive rotation of an initially steep (~60°) normal fault to shallower dips. Thirty km north of Ladron along the west side of the rift, Quaternary extensional faulting is evident in large travertine deposits at the Belen Quarry. Extensional fractures and cm-scale displacement normal faults at 4 locations give average paleostress orientations of 087, 112, 116, 127. A U-series age of 312 ka on faulted upper layers in one quarry indicates post-312 ka slip that we interpret to reflect surface manifestations of microseismicity above the Socorro magma body.

Ricketts, J. W.; Karlstrom, K. E.; Kelley, S. A.; Priewisch, A.; Crossey, L. J.; Asmerom, Y.; Polyak, V.; Selmi, M.

2011-12-01

6

New zircon fission-track ages from New Zealand Quaternary tephra: an interlaboratory experiment and recommendations for the determination of young ages  

Microsoft Academic Search

Fission-track dating, of zircons from five Pleistocene tephra in the Wanganui Basin, North Island, New Zealand, has been carried out independently in two different laboratories. The results from each are statistically identical even though there were some differences in laboratory techniques. The resulting ages confirm recent isothermal plateau fission-track (ITPFT) ages on two of these tephra, but with increased precision.

Diane Seward; Barry P. Kohn

1997-01-01

7

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

8

Nuclear Fission  

Microsoft Academic Search

The probability of nuclear fission is reviewed relative to spontaneous ; fission half lives, penetration of the fission barrier, fission with siow ; neutrons, fission at inoderate and high excitation energies. fission cross ; sections near the threshold, and the fission of elements lighter than thorium. ; The energy available for fission and the kinetic and excitation energies of ;

I. Halpern

1959-01-01

9

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

10

Irish Quaternary Association (IQUA)  

NSDL National Science Digital Library

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

1969-12-31

11

Second Quaternary dating workshop.  

National Technical Information Service (NTIS)

The second Quaternary dating methods workshop was held at Lucas Heights and sponsored by ANSTO and AINSE. Topics covered include, isotope and thermoluminescence dating, usage of accelerator and thermal ionisation mass spectrometry in environmental studies...

1999-01-01

12

Nuclear Fission  

NSDL National Science Digital Library

Start a chain reaction, or introduce non-radioactive isotopes to prevent one. Control energy production in a nuclear reactor! (Previously part of the Nuclear Physics simulation - now there are separate Alpha Decay and Nuclear Fission sims.)

Simulations, Phet I.; Adams, Wendy; Blanco, John; Lemaster, Ron; Mckagan, Sam; Perkins, Kathy

2004-07-01

13

Quaternary dichotomous voting rules  

Microsoft Academic Search

In this article, we provide a general model of “quaternary” dichotomous voting rules (QVRs), namely, voting rules for making\\u000a collective dichotomous decisions (to accept or reject a proposal), based on vote profiles in which four options are available\\u000a to each voter: voting (“yes”, “no”, or “abstaining”) or staying home and not turning out. The model covers most of actual\\u000a real-world

Annick Laruelle; Federico Valenciano

2010-01-01

14

Spontaneous fission  

SciTech Connect

The spontaneous fission (SF) of the heaviest actinides and the transactinides is of particular interest because of the dramatic changes in properties observed in the region of the heavy fermion isotopes and for still heavier elements. The existing experimental information on SF properties including half-life systematics, fragment kinetic-energy and mass-yield distributions, prompt neutron emission, and gamma emission will be reviewed. Possibility for extending studies of SF properties to other regions are considered and the potential for obtaining additional information about low-energy fission properties is discussed.

Hoffman, D.C. [Lawrence Berkeley Lab., CA (United States)

1993-09-01

15

Spontaneous fission  

NASA Astrophysics Data System (ADS)

The spontaneous fission (SF) of the heaviest actinides and the transactinides is of particular interest, because of the dramatic changes in properties observed in the region of the heavy fermium isotopes and for still heavier elements. The existing experimental information on SF properties, including half-life systematics, fragment kinetic energy and mass yield distributions, prompt neutron emission and gamma emission, will be reviewed. Possibilities for extending studies of SF properties to other regions are considered, and the potential for obtaining additional information about low-energy fission properties is discussed.

Hoffman, Darleane C.

1994-10-01

16

Bimodal fission  

SciTech Connect

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

Hulet, E.K.

1989-04-19

17

Nuclear Fission  

Microsoft Academic Search

The potential role of nuclear fission to meet increased future energy demand while reducing greenhouse gas emissions and controlling nuclear proliferation is assessed. The World Energy Council projection for an environmentally driven future is used, which projects deployment of nearly 3 TW(e) of nuclear generation by 2100, with concurrent reduction of global CO2 emissions to one-third of present levels. We

ERICH SCHNEIDER; WILLIAM C. SAILOR

2006-01-01

18

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

19

[Quaternary prevention in the elderly].  

PubMed

Quaternary prevention is a group of measures taken to prevent, decrease and/or alleviate the harm caused by health activities. Health activities not only generally produce benefits, but also harm. That is to say, although medical intervention is mainly favourable, there is a dynamic balance that requires continuous assessment of the clinical situation as naturally only those health activities that achieve more benefit than harm at the end are justified. Quaternary prevention is the avoidance of unnecessary medical activity, such as "check-ups". In another example, quaternary prevention is the recommendation of preventive measures of proven efficacy. As regards diagnosis, quaternary prevention is, for example, the avoidance of screening without foundation, such as in prostate cancer. The appropriate use of antibiotics in upper respiratory tract infections serves as an example of quaternary prevention in the field of treatment. Another example is the application of the correct rehabilitation techniques in non-specific low back pain, such as swimming and maintaining an active life as much as possible. Not to forget other important "non-classic" aspects in the elderly, such as to limit the harm that can be caused by physical movement restriction devices. These and other examples in daily practice are considered in this article to encourage the continual assessment of quaternary prevention, the classic primum non nocere "first, do no harm". PMID:23062686

Gérvas, Juan

2012-10-11

20

Quaternary uplift of southern Italy  

Microsoft Academic Search

Dramatic coastline changes demonstrate rapid Quaternary uplift of Calabria in southern Italy. Because most of the west (Tyrrhenian Sea) coast is normal fault bounded, previous work has asserted that its uplift is local footwall uplift related to extension. However, the east (Ionian Sea) coast is also uplifting but is not normal fault bounded. This reanalysis, based on original field work

Rob Westaway

1993-01-01

21

Quaternary Studies: An Interdisciplinary Program  

NSDL National Science Digital Library

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. Students and educators can find information on the researchers involved with the program and the necessary course work.

1969-12-31

22

Corrosion inhibition by quaternary amines  

Microsoft Academic Search

Quaternary ammonium compounds are excellent inhibitors of acid corroison, and seem to influence the anodic partial reaction more than the cathodic. This behavior is not readily interpreted in terms of physical vs. chemical adsorption, since these compounds do not possess bonding for chemisorption. Increasing the hydrogen bulk in the inhibitor molecule markedly increases the inhibition efficiency, which is to be

R. M. Hurd; H. Raiszadeh

1970-01-01

23

Quaternary alkaloids of Argemone mexicana.  

PubMed

Four quaternary isoquinoline alkaloids, dehydrocorydalmine, jatrorrhizine, columbamine, and oxyberberine, have been isolated from the whole plant of Argemone mexicana Linn. (Papaveraceae) and their structures established by spectral evidence. This is the first report of these alkaloids (dehydrocorydalmine, jatrorrhizine, columbamine, and oxyberberine) from Argemone mexicana and the Argemone genus. PMID:20645832

Singh, Sarita; Singh, Tryambak Deo; Singh, Virendra Pratap; Pandey, Vidya Bhushan

2010-02-01

24

ChemTeacher: Fission  

NSDL National Science Digital Library

ChemTeacher compiles background information, videos, articles, demonstrations, worksheets and activities for high school teachers to use in their classrooms. The Fission page includes resources for teaching students about the discovery and applications of fission.

2011-01-01

25

Fast and slow fission  

SciTech Connect

Measurements of alpha particle induced fission of actinide nuclei and fission of the composite system /sup 170/Yb formed in /sup 12/C and /sup 20/Ne bombardments both show significantly greater neutron emission prior to fission than is consistant with current statistical models. Implications of these results are discussed in the context of possible extreme models: (1) the enhancement of fission at low excitation energies due to shell effects; (2) the inhibition of fission at high excitations due to a limiting of the fission width; and (3) the possibility of significant neutron emission during the descent from saddle to scission. In addition the apparent incompatability between current models of incomplete fusion processes and the analysis of light heavy ion induced fission which ignore incomplete fusion is discussed.

Britt, H.C.; Gavron, A.

1981-01-01

26

Andrei Sher and Quaternary science  

NASA Astrophysics Data System (ADS)

Andrei Sher (1939-2008) was a key individual in Beringian studies who made substantial and original contributions, but also, importantly, built bridges between western and eastern Beringian scientists spanning some five decades of research. He is perhaps best known as a Quaternary palaeontologist, specializing in large mammals, and mammoths in particular, but his field of his scientific research was much broader, encompassing Quaternary geology, stratigraphy, geocryology, and paleoenvironmental reconstructions. He worked mainly in Siberia, in the Kolyma and Indigirka lowlands, and Chukotka, but also completed fieldwork in Alaska and Yukon through joint projects with American and Canadian scientists. Andrei was an active scientist until the last days of his life. He was involved in many different research projects ranging from mammoth evolution, fossil insects and environmental changes and ancient DNA. Without Andrei’s connections between researchers, many unique discoveries would likely be unknown.

Kuzmina, Svetlana; Lister, Adrian M.; Edwards, Mary E.

2011-08-01

27

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

28

21 CFR 172.165 - Quaternary ammonium chloride combination.  

Code of Federal Regulations, 2013 CFR

...FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Food Preservatives § 172.165 Quaternary ammonium chloride combination. The food additive, quaternary ammonium chloride...

2013-04-01

29

Quaternary glaciation of the Himalayan-Tibetan  

Microsoft Academic Search

Glacial geological evidence from throughout the Himalayan-Tibetan orogen is examined to determine the timing and extent of late Quaternary glaciation in this region and its relation to similar changes on a global scale. The evidence summarised here supports the existence of expanded ice caps and extensive valley glacier systems throughout the region during the late Quaternary. However, it cannot yet

LEWIS A. OWEN; MARC W. CAFFEE; ROBERT C. FINKEL; YEONG BAE SEONG

30

Stereoselective Synthesis of Quaternary Proline Analogues  

PubMed Central

This review describes available methods for the diastereoselective and asymmetric synthesis of quaternary prolines. The focus is on the preparation of ?-functionalized prolines with the pyrrolidine moiety not embedded in a polycyclic frame. The diverse synthetic approaches are classified according to the bond which is formed to complete the quaternary skeleton.

Calaza, M. Isabel

2009-01-01

31

Numerical simulations of fission  

SciTech Connect

Hydrodynamic simulation techniques to the fission problem of the lunar origin were applied. It is indicated that, for fluids with the compressibility of stars, dynamic fission instabilities lead to spiral arm ejection of mass and angular momentum in the form of a ring or disk of debris, not as a single body. Some quantitative aspects of these results seem favorable to lunar origin by fission. Fission instabilities in fluid objects with a smaller degree of compressibility, more closely approximating terrestrial material are considered. Although the qualitative features are similar, there are significant quantitative differences for the stiffer equation of state. The implications of the results for the fission hypothesis of lunar origin are discussed. Evolutions illustrating possible approaches to instability are presented.

Durisen, R.H.; Gingold, R.A.; Scott, E.H.

1984-01-01

32

Isomers in Fission Fragments  

SciTech Connect

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 {sup 248}Cm and {sup 252}Cf and in thermal neutron-induced fission of {sup 233}U, {sup 235}U and {sup 241}Pu 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.; Koester, U.; Krempel, J.; Materna, Th.; Mutti, P.; Soldner, T. [Institut Laue-Langevin, B.P. 156, F-38042 Grenoble Cedex 9 (France); Genevey, J.; Pinston, J. A.; Simpson, G. [Laboratoire de Physique Subatomique et de Cosmologie, IN2P3-CNRS/Universite J. Fourier, F-38026 Grenoble Cedex (France); Rzaca-Urban, T.; Zlomaniec, A.; Lukasiewicz, M. [Faculty of Physics, University of Warsaw, PL-00681 Warsaw (Poland); Sieja, K. [Gesellschaft fuer Schwerionenforschung, D-64291 Darmstadt (Germany); Nowacki, F.; Dorvaux, O.; Gall, B. J. P.; Roux, B. [Institut Pluridisciplinaire Hubert Curien, F-67037 Strasbourg Cedex (France); Dare, J. A. [Department of Physics and Astronomy, The University of Manchester, M13 9PL Manchester (United Kingdom)] (and others)

2009-01-28

33

Nuclear Fission Fuel is Inexhaustible  

Microsoft Academic Search

Nuclear fission energy is as inexhaustible as those energies usually termed ldquorenewablerdquo, such as hydro, wind, solar, and biomass. But, unlike the sum of these energies, nuclear fission energy has sufficient capacity to replace fossil fuels as they become scarce. Replacement of the current thermal variety of nuclear fission reactors with nuclear fission fast reactors, which are 100 times more

H. D. Lightfoot; W. Manheimer; D. A. Meneley; D. Pendergast; G. S. Stanford

2006-01-01

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

Quaternary tectonics of the southeastern coastal area, Korea: subsidence of marine terrace and late Quaternary faults  

Microsoft Academic Search

Strong earthquake has rarely occurred in Korean peninsula and a few events were recorded since 27 A.D. Historical and recent earthquakes are concentrated in the southeastern area of Korean peninsula, where more than 30 Quaternary fault exposures have recently been founded. The southern tip of the southeastern coastal area has been known as a stable block: quaternary fault and micro-earthquakes

S.-J. Choi; Y. Ota; U. Chwae

2003-01-01

36

Major Quaternary uplift along the northernmost San Andreas fault, King Range, northwestern California  

SciTech Connect

The King Range is a rugged coastal mountain range that parallels the San Andreas transform fault system just south of the Mendocino triple junction. Point Delgada is a small coastal headland that projects into the Pacific Ocean just southwest of the King Range. Apatite fission-track ages from parts of the King Range are remarkably young, averaging 1.2 Ma, indicating that a minimum of 2-5 km of uplift and unroofing have occured in the past 1.2 m.y. In contrast, ages from Point Delgada are about 12 Ma, and fission-track length data indicate that rocks there have resided at low temperatures ({le}50{degree}C) and thus at shallow depths since soon after 12 Ma. Therefore Point Delgada has experienced relative vertical stability. The contrast in uplift histories indicates that the two areas are separated by a major fault with a minimum of {approximately}1 km of Quaternary vertical offset. The fault is probably part of the San Andreas system and so may also have undergone major Quaternary strike-slip offset. The uplift in the King Range seems too great and too localized to have resulted from isostatic effects accompanying passage of the Mendocino triple junction and development of a slab-free window; rather, it is probably a local response to space problems among the various moving crustal blocks around the triple junction and San Andreas fault.

Dumitru, T.A. (La Trobe Univ., Bundoora, Victoria (Australia))

1991-05-01

37

Fission Throughout the Periodic Table.  

National Technical Information Service (NTIS)

The dualistic view of fission and evaporation as two distinct compound nucleus processes is substituted with a unified view in which fission, complex fragment emission, and light particle evaporation are seen as different aspects of a single process. 47 r...

L. G. Moretto G. J. Wozniak

1989-01-01

38

Delayed gamma Rays from Fission.  

National Technical Information Service (NTIS)

Studies of delayed gamma rays from fission at early times were conducted using the pulsed beams of neutrons and bremsstrahlung x rays from an electron linear accelerator to produce fissions. Measurements of the energy spectrum of isomeric gamma rays from ...

R. B. Walton R. E. Sund

1965-01-01

39

A Quaternary volcanic ash deposit in western Missouri  

SciTech Connect

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

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

1993-03-01

40

Fission fragment damage in zircon  

Microsoft Academic Search

X-ray diffraction, electron microscope and optical studies have been : ade on zircons damaged by fission fragments derived from the action of neutrons on uranium impurities in the zircon lattice. A dosage of about 10 fission events · cm was required to produce diffuse x-ray scattering, observable by conventional photographic methods, and a dosage of about 10 fission events ·

E. R. Vance; J. N. Boland

1975-01-01

41

Student Experiments in Spontaneous Fission.  

ERIC Educational Resources Information Center

|Advanced undergraduate experiments utilizing a commercially available, thin spontaneous fission source are described, including studies of the energy and mass distribution of the fission fragments and their energy and angular correlation. The experiments provide a useful introduction to fission, nuclear mass equations, heavy-ion physics, and…

Becchetti, F. D.; Ying, J. S.

1981-01-01

42

Microscopic description of induced fission  

NASA Astrophysics Data System (ADS)

Selected aspects of the description of neutron-induced fission in 240Pu in the framework of the nuclear energy density functional theory at finite temperature are presented. In particular, we discuss aspects pertaining to the choice of thermodynamic state variables, the evolution of fission barriers as function of the incident neutron energy, and the temperatures of the fission fragments.

Schunck, Nicolas

2013-04-01

43

A Toxicological Evaluation of Certain Heparin-Quaternary Ammonium Complexes.  

National Technical Information Service (NTIS)

Physical and chemical characterizations show that the heparin-quaternary ammonium salt complexes can be reproducibly prepared from a given lot of a quaternary ammonium salt. Local toxicity studies also indicate that both the tridodecyl methyl ammonium chl...

G. A. Grode J. P. Crowley R. D. Falb R. I. Leininger

1974-01-01

44

Biomodal Spontaneous Fission.  

National Technical Information Service (NTIS)

Investigations of mass and kinetic-energy distributions from spontaneous fission have been extended in recent years to an isotope of element 104 and, for half-lives, to an isotope of element 108. The results have been surprising in that spontaneous fissio...

E. K. Hulet

1989-01-01

45

Nuclear fission and multifragmentation  

SciTech Connect

The many-body nuclear decay known as multifragmentation is considered as a process competing with nuclear fission. It is shown that, in the particular case of disintegration of {sup 238}U by relativistic protons, the two processes occur simultaneously in the same nuclear reaction. 5 refs., 5 figs.

Zhdanov, A.A.; Solyakin, G.E. [Konstantinov Institute of Nuclear Physics, Gatchina (Russian Federation); Obukhov, A.I. [Khlopin Radium Institute, St. Petersburg (Russian Federation)

1994-07-01

46

Bacterial metabolism of quaternary ammonium compounds.  

PubMed Central

Of 10 quaternary ammonium compounds tested for biodegradation by the biological oxygen demand technique, only decyl- and hexadecyltrimethylammonium bromides were decomposed by organisms derived from sewage and soil. A mixture consisting of individual strains of Pseudomonas and Xanthomonas grew in solutions containing decyltrimethylammonium bromide as sole carbon source. The xanthomonad metabolized this quaternary ammonium compound in the presence of other organic molecules. The products of this activity included 9-carboxynomyl- and 7-carboxyheptyltrimethylammonium, suggesting that the terminal carbon of the decyl moiety is oxidized and the resulting carboxylic acid is subject to beta-oxidation.

Dean-Raymond, D; Alexander, M

1977-01-01

47

Quaternary Marine Sulfur Cycle Dynamics  

NASA Astrophysics Data System (ADS)

Published data show a -0.8% change in marine sulfate ?34S ratios in the past 2 Ma. Prior to this period it was stable at ~ 22% for ~ 50Ma since the Eocene. Compared to the residence time of sulfate (>10 Ma) the observed change is large and implies a major disturbance of the marine sulfur cycle. However, the cause of the disturbance, as well as the timing of its onset are poorly constrained. Here we present a new set of ?34S ratios of marine sulfate for the last 3 Ma with a temporal resolution of ~300ka, which shows a linear decline from 22 to ~21% in the past 1.75Ma. This may represent a change in volcanic and hydrothermal activity, pyrite burial or erosion and weathering of exposed evaporites and sulfides, which are the main processes affecting sulfate ?34S. However, during this period there is no geological evidence for exceptional volcanic and hydrothermal activity and consequently, the observed negative shift reflects either a change in isotopic composition and volume of erosional input of sulfate to the ocean, or a decrease in pyrite burial. The isotopic composition of the input flux depends on the relative proportion of sulfide vs. sulfate weathering. Sedimentary sulfides are mostly concentrated in organic rich sediments on continental shelves. Existing sea level records suggest periodic sea level drops during glacial stages related to the formation of ice sheets. This could affect sulfur cycling in two ways: a) exposure to surface weathering and erosion agents of large parts of continental shelves increased global sulfide oxidation and thus the input flux of sulfate to the ocean and/or b) the reduction of shelf areas resulted in decreased pyrite burial. We explore the effects of these changes with a simple box model. The modeling results indicate that the observed isotopic shift requires a 150% increase of pyrite weathering or a 90% reduction of pyrite burial over the past 1.75Ma. When both of these processes change in concert the same effect is produced with the doubling of pyrite weathering and 50% decrease of pyrite burial. As pyrite burial and organic matter burial are intimately linked, a drastic decrease in pyrite burial should leave its mark in the carbon isotopic record which shows no evidence of a major change in carbon cycling. We thus propose that increased sulfide weathering, either from subaerial exposure, or as a result of increased winnowing might be the principal cause of the negative ?34S shift in the Quaternary.

Markovic, S.; Paytan, A.; Wortmann, U. G.

2011-12-01

48

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 false Tricyclic quaternary amine salt (generic). 721.10569 Section 721...721.10569 Tricyclic quaternary amine salt (generic). (a) Chemical substance...generically as tricyclic quaternary amine salt (PMN P-08-471) is subject to...

2013-07-01

49

Quaternary cave levels in peninsular Florida  

Microsoft Academic Search

The hypothesis that caves in the Florida Peninsula are tied to Quaternary sea levels was proposed by hydrogeologists, without data, some 40 years ago. The hypothesis is a version of glacial control of cave levels, which is the logical combination of the water-table theory of speleogenesis and the concept that base level positions the water table. At the USA type

Lee J. Florea; H. L. Vacher; Brian Donahue; David Naar

2007-01-01

50

Quaternary glaciation of the Himalaya and Tibet  

Microsoft Academic Search

Glacial geological evidence from throughout the Himalaya-Tibet shows the existence of expanded ice caps and extensive valley glacier systems during the late Quaternary. Whether the timing of the extent of maximum glaciation was synchronous throughout the entire region or whether the response was more varied is a topic of much contention. This is mainly because the lack of organic material

L. A. Owen

2008-01-01

51

Dynamics of nuclear fission  

Microsoft Academic Search

The most interesting process of collective flow of nuclear matter is the fission process. The time-scale of this process at moderate to high excitation energies is reviewed. Various methods to measure the time associated with large scale collective flow of nuclei in the range of 10^(-21) to 10^(-17) s are compared. Pre- and post-scission multiplicities of light particles in particular

D. Hilscher; H. Rossner

1992-01-01

52

Ternary fission of neutron induced uranium fissioning isomers  

NASA Astrophysics Data System (ADS)

Spontaneously fissioning isomers (SFI) of uranium were produced in 236, 238U(n,n') reactions at 4.5 MeV mean neutron energy. A pulsed beam electrostatic accelerator was used and a time analysis of fission events was applied. Fission fragments were detected by a scintillation method, and long-range fission particles were detected by an ionization technique. Relative fission probabilities through the SFI state for both the nuclei were determined as (1.30 +/-.01).10-4 in 236U and (1.48 +/- 02). 10-4 in 238U case. The SFI half-lives were determined as 121 +/- 2 ns and 267 +/- 13 ns respectively. As a result of uranium SFI ternary fission study it was observed that one ternary per 163 +/- 44 binary fissions of 236mfu and one ternary per 49 +/- 14 binary fissions of 238mfU took place. These figures seem to be rather high as compared with nonisomeric ternary fission probability data, and tentative effect of a particular nucleon configuration in the uranium SFI is supposed.

Makarenko, V. E.; Molchanov, Yu. D.; Otroshenko, G. A.; Yankov, G. B.

1989-10-01

53

Fission Yield Predictions with TALYS  

SciTech Connect

The nuclear model code TALYS has been extended to enable the prediction of fission yields. The mass yield curves are extracted from temperature-dependent multi-modal random-neck rupture calculations. Charge yields of the fission fragment are determined using the scission-point model and subsequently folded with the mass yields. We present a comparison of several fission-fragment mass yields and isotopic yields with experimental data.

Duijvestijn, M.C.; Koning, A.J. [Nuclear Research and Consultancy Group NRG, P.O. Box 25, NL-1755 ZG Petten (Netherlands)

2005-05-24

54

''Subthreshold'' reactions involving nuclear fission  

SciTech Connect

We analyze reactions of several types that are naively below threshold but can proceed because of the release of binding energy from nuclear fission and occasionally the formation of Coulombic bound states. These reactions include (i) photofission with pion production and (ii) charged current neutrino-nucleus reactions that lead to fission and/or formation of a Coulomb bound state of a {mu}{sup -} with the nucleus of a fission fragment. We comment on the possible experimental observation of these reactions.

Goldhaber, M.; Shrock, R.

2001-02-01

55

Fission hindrance in hot nuclei  

SciTech Connect

The role of dynamics in fission has attracted much interest since the discovery of this process over fifty years ago. However, the study of the dynamical aspects of fission was for many years hampered by the lack of suitable experimental observables against which theoretical calculations could be tested. For example, it was found that the total kinetic energy release in fission can be described equally well by very different dissipation mechanisms, namely the wall formula, that is based on the collisions of the nucleons with the moving wall of the system, as well as a bulk viscosity of the nuclear matter. Although early theoretical work suggested that the fission process may be described as a diffusion process over the fission barrier, this was largely forgotten because of the success of a purely statistical model which instead of enumerating the ultimate final states of the process argues that the fission rate is determined at the {open_quote}transition state{close_quote} as the system traverses the fission saddle point. It was therefore significant when Gavron showed that the transition state model was unable to describe the number of neutrons emitted prior to scission at high excitation energy in reactions of {sup 16}O+{sup 142}Nd. Subsequent experimental work using different methods to measure the fission dissipation/viscosity has confirmed these initial observations. It was therefore very surprising when Moretto in recent publications concluded that their analysis of fission excitation functions obtained with a and {alpha} and {sup 3}He induced projectiles was perfectly in accord with the transition state model and left no room for fission viscosity. In this paper we`ll show that Moretto`s analysis is flawed by assuming first chance fission only (in direct contradiction to the experimental observation of pre-scission neutron emission in heavy-ion induced fission), and reveal why the systematics presented by Moretto looked so convincing despite these flaws.

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

1997-07-01

56

Distribution of fission yields for fission spectrum neutron-induced fission of uranium-238  

Microsoft Academic Search

The mass-yield distribution for the neutron-induced fission of ²³⁸U by degraded fission spectrum neutrons with an average energy of 1.52 MeV has been measured radiochemically for 26 mass chains in the region A = 89 to 153. Germanium-lithium gamma-ray spectroscopy coupled with beta-particle counting techniques was used to determine the absolute activities of each nuclide measured. The absolute cumulative fission

D. C. Harris; J. N. Beck; W. L. Raines; J. T. Harvey; J. L. Meason; H. L. Wright

1977-01-01

57

Evaluation of Fission Product After-Heat.  

National Technical Information Service (NTIS)

Reported here are studies on: estimation of fission-product gamma spectra; comparisons of theoretical predictions of fission-product decay power with ongoing experimental programs; and a protocol for estimating bias in decay energy estimates for fission p...

B. I. Spinrad

1976-01-01

58

Muon-induced fission: probing energy dissipation and fission dynamics  

NASA Astrophysics Data System (ADS)

In actinide muonic atoms, the 2p --> 1s and 3d --> 1s muonic transitions (inverse internal conversion) excitate the giant dipole and giant quadrupole resonances which act as doorway states for fission. The nuclear excitation energy is about 6.5-10 MeV. Because the muon lifetime is long compared to the timescale of prompt fission, the motion of the muon in the Coulomb field of the fissioning nucleus may be utilized to learn about the dynamics of fission. We solve the time-dependent Dirac equation for a muon which is initially bound to a fissioning actinide nucleus. The computations are carried out on a 3-D Cartesian lattice utilizing the Basis-Spline collocation method. Theoretical studies of the muon-attachment probability to the light fission fragment in combination with experimental data can be utilized to determine the energy dissipation in fission. For Np-237 we find a dissipated energy of about 10 MeV and a fission time delay due to friction of order 2*10-21 s. Ref: Oberacker et al, http://arxiv.org/abs/nucl-th/0403087

Oberacker, Volker; Umar, Sait

2004-10-01

59

Spontaneous Fission Properties of the Heavy Elements: Bimodal Fission.  

National Technical Information Service (NTIS)

We have measured the mass and kinetic-energy distributions from the spontaneous fission of sup 258 Fm, sup 258 No, sup 259 Md, sup 260 Md, sup 260 (104), and sup 262 No. All are observed to fission with a symmetrical division of mass, whereas the total-ki...

E. K. Hulet

1988-01-01

60

Efficient cellulose solvent: quaternary ammonium chlorides.  

PubMed

Pure quaternary tetraalkylammonium chlorides with one long alkyl chain dissolved in various organic solvents constitute a new class of cellulose solvents. The electrolytes are prepared in high yields and purity by Menshutkin quaternization, an inexpensive and easy synthesis route. The pure molten tetraalkylammonium chlorides dissolve up to 15 wt% of cellulose. Cosolvents, including N,N-dimethylacetamide (DMA), may be added in large excess, leading to a system of decreased viscosity. Contrary to the well-established solvent DMA/LiCl, cellulose dissolves in DMA/quaternary ammonium chlorides without any pretreatment. Thus, the use of the new solvent avoids some disadvantages of DMA/LiCl and ionic liquids, the most extensively employed solvents for homogeneous cellulose chemistry. PMID:24014114

Kostag, Marc; Liebert, Tim; El Seoud, Omar A; Heinze, Thomas

2013-09-09

61

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

62

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

63

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

64

Hydration effects in quaternary amine extraction systems  

Microsoft Academic Search

The extraction of Al+++, Cd++, Co++, Cu+, Cu++, Fe++, Fe+++, In+++, Ni++, and Zn++ with quaternary amine was studied using chloride and sulfate as ligands. On the basis of loading experiments and slope analyses, the species extracted were: CdCl{4\\/=}, CoCl{4\\/=}, CuCl{2\\/-}, CuCl{4\\/=}, FeCl{4\\/-}, and ZnCl{4\\/=}. Water content of the organic phase was analyzed as a function of loading by Karl

J. D. Miller; M. C. Fuerstenau

1970-01-01

65

Hydration effects in quaternary amine extraction systems  

Microsoft Academic Search

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

J. D. Miller; M. C. Fuerstenau

1970-01-01

66

FISSION PRODUCT GAMMA RAY SPECTRA  

Microsoft Academic Search

Uranium-235 fission product gamma spectra were calculated for various ; reactor operating histories. An IBM704 digital computer program was coded to ; compute the gamma energy contributed by each fission product gamma ray and to sum ; these results in energy groups. A representative curve showing the decay of ; various energy groups is presented. Comparisons are made with data

1958-01-01

67

Fission-fragment angular distributions  

Microsoft Academic Search

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

P. Bond

1984-01-01

68

Fission throughout the periodic table  

SciTech Connect

The dualistic view of fission and evaporation as two distinct compound nucleus processes is substituted with a unified view in which fission, complex fragment emission, and light particle evaporation are seen as different aspects of a single process. 47 refs., 22 figs.

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

1989-04-01

69

Fission fragment driven neutron source  

DOEpatents

Fissionable uranium formed into a foil is bombarded with thermal neutrons in the presence of deuterium-tritium gas. The resulting fission fragments impart energy to accelerate deuterium and tritium particles which in turn provide approximately 14 MeV neutrons by the reactions t(d,n).sup.4 He and d(t,n).sup.4 He.

Miller, Lowell G. (Idaho Falls, ID); Young, Robert C. (Idaho Falls, ID); Brugger, Robert M. (Columbia, MO)

1976-01-01

70

TREATMENT OF FISSION PRODUCT WASTE  

DOEpatents

A pyrogenic method of separating nuclear reactor waste solutions containing aluminum and fission products as buring petroleum coke in an underground retort, collecting the easily volatile gases resulting as the first fraction, he uminum chloride as the second fraction, permitting the coke bed to cool and ll contain all the longest lived radioactive fission products in greatly reduced volume.

Huff, J.B.

1959-07-28

71

Multicluster accompanied fission  

SciTech Connect

In this process a heavy or superheavy nucleus spontaneously breaks into four, five, or six nuclei of which two are asymmetric or symmetric heavy fragments and the others are light clusters, e.g., {alpha} particles, {sup 10}Be, {sup 14}C, {sup 20}O, or combinations of them. Examples are presented for the two-, three-, and four-cluster accompanied cold fission of {sup 252}Cf and {sup 262}Rf, in which the emitted clusters are 2{alpha}, {alpha}+{sup 6}He, {alpha}+{sup 10}Be, {alpha}+{sup 14}C, 3{alpha}, {alpha}+{sup 6}He+{sup 10}Be, 2{alpha}+{sup 6}He, 2{alpha}+{sup 8}Be, 2{alpha}+{sup 14}C, and 4{alpha}. A comparison is made with the recently observed {sup 252}Cf cold binary fission, and cold ternary (accompanied by {alpha} particle or by {sup 10}Be cluster). The strong shell effect corresponding to the doubly magic heavy fragment {sup 132}Sn is emphasized. The most favorable mechanism of such a decay mode should be the emission from an elongated neck formed between the two heavy fragments. {copyright} {ital 1999} {ital The American Physical Society}

Poenaru, D.N.; Gherghescu, R.A. [National Institute of Physics and Nuclear Engineering, P.O. Box MG-6, RO-76900 Bucharest (Romania); Poenaru, D.N.; Greiner, W.; Gherghescu, R.A. [Institut fuer Theoretische Physik der Universitaet, Postfach 111932, D-60054 Frankfurt am Main (Germany); Poenaru, D.N.; Greiner, W.; Hamilton, J.H.; Ramayya, A.V. [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Poenaru, D.N.; Hourany, E. [Institut de Physique Nucleaire, F-91406 Orsay Cedex (France)

1999-06-01

72

Nuclear Fission Research at IRMM  

NASA Astrophysics Data System (ADS)

The Institute for Reference Materials and Measurements (IRMM) will celebrate its 45th anniversary in 2005. With its 150-MeV Geel Electron Linear Accelerator (GELINA) and 7-MV Van de Graaff accelerator as multi-purpose neutron sources, it served the nuclear physics community for this period. The research in the field of nuclear fission was focused in recent years on both the measurement and calculation of fission cross sections, and the measurement of fission fragment properties. Fission cross sections were determined for 233Pa and 234U; the fission process was studied in the resolved resonance region of 239Pu(n,f) and for 251Cf(nth,f). These measurements derive their interest from accelerator driven systems, the thorium fuel cycle, high temperature reactors, safety issues of current reactors, and basic physics. The measurements are supported by several modeling efforts that aim at improving model codes and nuclear data evaluation.

Hambsch, Franz-Josef

2005-05-01

73

QUATERNARY GEOLOGICAL FRAMEWORK OF NORTH-HOLLAND AND THE MARKERMEER  

Microsoft Academic Search

Quaternary geological data are presented as a basis for the extensive geohydrological and geotechnical studies performed to investigate possible harmful effects of the Markerwaard reclamation project.

W. E. Westerhoff

74

Prompt Fission Neutron Emission in Resonance Fission of 239Pu  

SciTech Connect

The prompt neutron emission probability from neutron-induced fission in the resonance region is being investigated at the time-of-flight facility GELINA of the IRMM. A double Frisch-gridded ionization chamber is used as a fission-fragment detector. For the data acquisition of both the fission-fragment signals as well as the neutron detector signals the fast digitization technique has been applied. For the neutron detection, large-volume liquid scintillation detectors from the DEMON collaboration are used. A specialized data analysis program taking advantage of the digital filtering technique has been developed to treat the acquired data.Neutron multiplicity investigations for actinides, especially in resonance neutron-induced fission, are rather scarce. They are, however, important for reactor control and safety issues as well as for understanding the basic physics of the fission process. Fission yield measurements on both 235U and 239Pu without prompt neutron emission coincidence have shown that fluctuation of the fission-fragment mass distribution exists from resonance to resonance, larger in the case of 235U. To possibly explain these observations, the question now is whether the prompt neutron multiplicity shows similar fluctuations with resonance energy.

Hambsch, Franz-Josef; Oberstedt, Stephan [EC-JRC-Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium); Varapai, Natallia; Serot, Olivier [CEA Cadarache, DEN/DER/SPRC/LEPh, F-13108 St. Paul-Lez-Durance (France); Zeinalov, Shakir [Joint Institute for Nuclear Research (JINR), 141980 Dubna, Moscow Region (Russian Federation)

2005-05-24

75

Cluster aspects of binary fission  

NASA Astrophysics Data System (ADS)

With the improved scission-point model the mass distributions are calculated for induced fission of different Hg isotopes with even mass numbers A =180, 184, 188, 192, 196, 198. The calculated mass distribution and mean total kinetic energy of fission fragments are in a good agreement with the existing experimental data. The change in the shape of the mass distribution from asymmetric to more symmetric is revealed with increasing A of the fissioning AHg nucleus, and the reactions are proposed to verify this prediction experimentally.

Andreev, A. V.; Adamian, G. G.; Antonenko, N. V.

2013-04-01

76

Intrinsic energy partition in fission  

NASA Astrophysics Data System (ADS)

The intrinsic energy partition between two complementary fission fragments is investigated microscopically. 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 excitation energy in a wide distribution of fission fragments is calculated for the 234U parent nucleus.

Mirea, M.

2013-03-01

77

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

78

Quaternary structure, aggregation and cytotoxicity of transthyretin.  

PubMed

Transthyretin (TTR) with a Ser112-to-Ile mutation is known to cause amyloidosis with severe cardiomyopathy. We investigated the quaternary structure, aggregation and cytotoxicity of the S112I variant. This variant exists as a dimer at physiological pH, self-assembles into spherical aggregates and induces cell death in human neuroblastoma IMR-32 cells. In addition, we determined the neutron crystal structure of TTR at 2.0 Å resolution. The neutron structure revealed that the hydrogen-bond network involving His88 is important for the stabilization of the dimer-dimer and monomer-monomer interfaces. PMID:22439750

Mizuguchi, Mineyuki; Yokoyama, Takeshi; Nabeshima, Yuko; Kawano, Keiichi; Tanaka, Ichiro; Niimura, Nobuo

2012-03-23

79

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

80

Uplift of quaternary shorelines in eastern Patagonia: Darwin revisited  

Microsoft Academic Search

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

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

2011-01-01

81

Ecostratigraphic datums and sequence stratigraphy: Application to the marine Quaternary  

Microsoft Academic Search

The marine Quaternary is characterized by few evolutionary appearances and extinctions of planktonic foraminifera. Because climatic fluctuations are a fundamental characteristic of Pleistocene, however, better stratigraphic resolution of the marine Quaternary can be gained by the establishment of biozones based on climatically controlled foraminiferal assemblages. Utilizing relative abundances of the warm-water Globorotalia menardii complex and temperature-water G. inflata, supplemented by

R. E. Martin; E. Neff; G. W. Johnson; D. Krantz

1991-01-01

82

Sorption and desorption of quaternary amine cations on clays  

Microsoft Academic Search

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

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

1993-01-01

83

Fission Modes of Mercury Isotopes  

SciTech Connect

Background: Recent experiments on -delayed fission in the mercury-lead region and the discovery of asymmetric fission in 180Hg [A. N. Andreyev et al., Phys. Rev. Lett. 105, 252502 (2010)] have stimulated theoretical interest in the mechanism of fission in heavy nuclei.

Purpose: We study fission modes and fusion valleys in 180Hg and 198Hg to reveal the role of shell effects in the prescission region and explain the experimentally observed fragment mass asymmetry and its variation with A.

Methods: We use the self-consistent nuclear density functional theory employing Skyrme and Gogny energy density functionals.

Results: The potential energy surfaces in multidimensional space of collective coordinates, including elongation, triaxiality, reflection-asymmetry, and necking, are calculated for 180Hg and 198Hg. The asymmetric fission valleys well separated from fusion valleys associated with nearly spherical fragments are found in both cases. The density distributions at scission configurations are studied and related to the experimentally observed mass splits.

Conclusions: The energy density functionals SkM and D1S give a very consistent description of the fission process in 180Hg and 198Hg. We predict a transition from asymmetric fission in 180Hg toward a more symmetric distribution of fission fragments in 198Hg. For 180Hg, both models yield 100Ru/80Kr as the most probable split. For 198Hg, the most likely split is 108Ru/90Kr in HFB-D1S and 110Ru/88Kr in HFB-SkM .

Warda, M. [Maria Curie-Sk?odowska University-Poland; Staszczak, A. [Maria Curie-Sklodowska University; Nazarewicz, Witold [UTK/ORNL/University of Warsaw

2012-01-01

84

A miniature fast fission counter  

Microsoft Academic Search

A small, 1\\/4 inch diameter by 1\\/2 inch in length, fast neutron fission ; counter probe employing highly depleted uranium as the fission material is ; developed. The isotopic analysis of the uranium, obtained by the 3-stage mass ; spectrometer is as follows: U²³⁸ (essentially 100%) U²³⁶ (0.03 ; plus or minus 0.02 ppm), U²³⁵ (0.90 plus or minus 0.20

G. Hickman

1961-01-01

85

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

2004-02-26

86

Nuclear dissipation from fission time  

Microsoft Academic Search

Fission times, pre-scission neutron multiplicities and GDR pre-scission gamma-ray multiplicities measured for uranium or thorium nuclei formed with temperatures T ~ 1.8 MeV have been compared with calculations performed with CDSM2, a two-dimensional dynamical model combined with a statistical one. Among the three experimental approaches considered, fission times give access to the most precise pieces of information on nuclear dissipation

I. Gontchar; M. Morjean; S. Basnary

2002-01-01

87

Nuclear fission with inertial confinement  

Microsoft Academic Search

The possibility of inducing an explosive fission reaction in a small amount of fissionable material by a heavy-ion beam from\\u000a a high-power accelerator driver developed for bringing about fusion in deuterium-tritium cylindrical targets with direct burning\\u000a is analyzed. The consequences of the use of this method in the nuclear power industry are discussed.

D. G. Koshkarev; B. Yu Sharkov

2002-01-01

88

The Microscopic Theory of Fission  

SciTech Connect

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

Younes, W; Gogny, D

2009-06-09

89

Neutron Emission in Fission And Quasi-Fission of Hs  

SciTech Connect

Mass and energy distributions of fission-like fragments obtained in the reactions {sup 26}Mg+{sup 248}Cm, {sup 36}S+{sup 238}U and {sup 58}Fe+{sup 208}Pb leading to the formation of {sup 266,274}Hs are reported. From the analysis of TKE distributions for symmetric fragment it was found that at energies below the Coulomb barrier the bimodal fission of {sup 274}Hs, formed in the reaction {sup 26}Mg+{sup 248}Cm, is observed, while in the reaction {sup 36}S+{sup 238}U at these energies the main part of the symmetric fragments arises from the quasi-fission process. At energies above the Coulomb barrier the fusion-fission is a main process leading to the formation of symmetric fragment for the both reactions. In the case of {sup 58}Fe+{sup 208}Pb reaction the quasi-fission process is the main reaction mechanism at all measured energies. The pre- and post-scission neutron multiplicities as a function of the fragment mass have been obtained for all studied reactions.

Itkis, I. M.; Itkis, M. G.; Knyazheva, G. N.; Kozulin, E. M.; Krupa, L. [Flerov Laboratory of Nuclear Reactions, JINR, Dubna (Russian Federation); Hanappe, F. [Universite Libre de Bruxelles, Belgique (Belgium); Dorvaux, O.; Stuttge, L. [Institut de Recherches Subatomiques, Strasbourg (France)

2010-04-30

90

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

Microsoft Academic Search

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

Katherine J. Willis; Karl J. Niklas

2004-01-01

91

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

92

Compact fission counter for DANCE  

SciTech Connect

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

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

2010-11-06

93

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

2013-07-01

94

A quaternary temperament model and defense cluster preferences.  

PubMed

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

Kelly, Kathryn E; Tobacyk, Jerome J

2003-10-01

95

Status of fission yield data  

SciTech Connect

In this paper we summarize the current status of the recent US evaluation for 34 fissioning nuclides at one or more neutron incident energies and for spontaneous fission. Currently there are 50 yields sets, and for each we have independent and cumulative yields and uncertainties for approximately 1100 fission products. When finalized the recommended data will become part of Version VI of the US ENDF/B. Other major evaluations in progress that are included in a recently formed IAEA Coordinated Research Program are also summarized. In a second part we review two empirical models in use to estimate independent yields. Comparison of model estimates with measured data is presented, including a comparison with some recent data obtained from Lohengrin (Cf-249 T). 18 refs., 13 figs., 3 tabs.

England, T.R.; Blachot, J.

1988-01-01

96

Sampling ENDL Watt Fission Spectra  

SciTech Connect

All of the fission spectra in the Evaluated Nuclear Data Library, ENDL [1], are defined by a simple analytical function: a Watt spectrum [2], W(a,b,E') = C*Exp[-a*E']*Sinh[(b*E'){sup 1/2}]. Where the normalization, C, is given by, C = [{pi}b/4a]{sup 1/2} Exp[b/4a]/a. The coefficients a and b vary from one isotope to another and also vary weakly with the incident neutron energy. Here E' is the secondary energy, i.e., the energy at which the fission neutrons are emitted. In ENDL energy units of MeV for incident neutron energies between 0 and 20 MeV, in all cases b is very close to 1.0, and a varies over a rather small range near 1.0. Currently there are 38 fissionable isotopes in ENDL. For each of these isotopes I have parameterized a as a simple function of the incident neutron energy, and I treat b as always equal to unity. The values of these parameters are available to TART users as part of the TART CD package [3]. This parameterization coupled with the general Watt sampling method described below results in a very fast and accurate method of sampling all of the fission spectra in ENDL. In all cases I select the fissioning isotope, define a based on isotope and incident neutron energy, and then use the below described method to sample the energy E' of a neutron emitted due to fission.

Cullen, D E

2004-04-01

97

Absolute calibration technique for spontaneous fission sources  

SciTech Connect

An absolute calibration technique for a spontaneously fissioning nuclide (which involves no arbitrary parameters) allows unique determination of the detector efficiency for that nuclide, hence of the fission source strength.

Zucker, M.S.; Karpf, E.

1984-01-01

98

Options for Affordable Fission Surface Power Systems.  

National Technical Information Service (NTIS)

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 system...

M. Houts S. Gaddis R. Porter M. VanDyke T. Godfroy S. Bragg-Sitton A. Garber B. Pearson

2006-01-01

99

Search for Singlet Fission Chromophores  

SciTech Connect

Singlet fission, in which a singlet excited chromophore shares its energy with a ground-state neighbor and both end up in their triplet states, is of potential interest for solar cells. Only a handful of compounds, mostly alternant hydrocarbons, are known to perform efficiently. In view of the large number of conditions that a successful candidate for a practical cell has to meet, it appears desirable to extend the present list of high performers to additional classes of compounds. We have (i) identified design rules for new singlet fission chromophores and for their coupling to covalent dimers, (ii) synthesized them, and (iii) evaluated their performance as neat solids or covalent dimers.

Havlas, Z.; Akdag, A.; Smith, M. B.; Dron, P.; Johnson, J. C.; Nozik, A. J.; Michl, J.

2012-01-01

100

Neck Influence on Fission Paths  

SciTech Connect

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

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

2008-01-24

101

Quaternary Stratigraphy and Depositional Environments, Santa Monica Bay, Southern California.  

National Technical Information Service (NTIS)

High-resolution seismic-reflection profiles were used in conjunction with 51 vibracores to examine the Quaternary stratigraphy of the Santa Monica Shelf, southern California. Upper Pleistocene strata are confined to the central part of the shelf between t...

R. H. Osborne R. C. Scheidemann T. R. Nardin A. S. Harper

1980-01-01

102

Chemical Warfare Agent Decontaminant Solution Using Quaternary Ammonium Complexes.  

National Technical Information Service (NTIS)

A chemical warfare agent decontamination solution made up of about 20% of a quaternary ammonium complex containing benzyltrimethylammonium chloride and benzyltriethylammonium chloride and about 20% by weight of an oxidizer, dissolved in a solvent, such as...

D. T. Crounce

1997-01-01

103

Fusion Properties of Some Ionic Quaternary Ammonium Compounds.  

National Technical Information Service (NTIS)

Enthalpy, entropy and molar volume changes during the fusion process of a wide range of quaternary ammonium compounds are presented. This group of compounds has hitherto been unexplored and is of interest since, as far as melting mechanisms are concerned,...

T. G. Coker J. Ambrose G. J. Janz

1970-01-01

104

Induced nuclear fission viewed as a diffusion process: Transients  

Microsoft Academic Search

Induced nuclear fission is viewed as a diffusion process of the fission degree of freedom over the fission barrier. We describe this process in terms of a Fokker-Planck equation which contains the fission variable and its canonically conjugate momentum. We solve this equation numerically for several energies (temperatures) of the fissioning nucleus neglecting changes of the fission barrier due to

P. Grangé; Li Jun-Qing; H. A. Weidenmueller

1983-01-01

105

Neutronics for critical fission reactors and subcritical fission in hybrids  

NASA Astrophysics Data System (ADS)

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

Salvatores, Massimo

2012-06-01

106

Spontaneous fission properties of the heavy elements: Bimodal fission  

SciTech Connect

We have measured the mass and kinetic-energy distributions from the spontaneous fission of SVYFm, SVYNo, SVZMd, SWMd, SW(104), and SWSNo. All are observed to fission with a symmetrical division of mass, whereas the total-kinetic-energy (TKE) distributions strongly deviated from the Gaussian shape characteristically found in the fission of all other actinides. When the TKE distributions are resolved into two Gaussian's, the constituent peaks lie near 200 and near 233 MeV. We conclude two modes or bimodal fission is occurring in five of the six nuclides studied. Both modes are possible in the same nuclide, but one generally predominates. We also conclude the low-energy but mass-symmetrical mode is likely to extend to far heavier nuclei; while the high-energy mode will be restricted to a smaller region, a region of nuclei defined by the proximity of the fragments to the strong neutron and proton shells in TSSn. 21 refs., 7 figs., 1 tab.

Hulet, E.K.

1988-11-11

107

Theoretical Description of the Fission Process  

Microsoft Academic Search

Advanced theoretical methods and high-performance computers may finally unlock the secrets of nuclear fission, a fundamental nuclear decay that is of great relevance to society. In this work, we studied the phenomenon of spontaneous fission using the symmetry-unrestricted nuclear density functional theory (DFT). Our results show that many observed properties of fissioning nuclei can be explained in terms of pathways

Witold Nazarewicz

2009-01-01

108

Neutron Yields from Individual Fission Fragments  

Microsoft Academic Search

Two new methods are used to obtain data on neutron yield nuf as a function of the mass number M of the emitting fission fragment; the results suggest changes in fission theory. The methods involve the combination of data on fission mass yields obtained by radiochemical means with time-of-flight mass data. The more detailed method yields essentially the complete function

James Terrell

1962-01-01

109

Absolute fission rates in the FFTF  

Microsoft Academic Search

The part of the FFTF Reactor Characterization Program reported in this paper is a measurement of absolute fission rates of eight major fuel isotopes at two different positions within the reactor. The instruments employed in these tests were fission ionization chambers for which the absolute efficiency and fissionable deposit mass assay have been rigorously established.

D. M. Gilliam; J. L. Fuller; J. A. Grundl; J. A. Rawlins; J. W. Daughtry

1981-01-01

110

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

111

Quaternary cave levels in peninsular Florida  

NASA Astrophysics Data System (ADS)

The hypothesis that caves in the Florida Peninsula are tied to Quaternary sea levels was proposed by hydrogeologists, without data, some 40 years ago. The hypothesis is a version of glacial control of cave levels, which is the logical combination of the water-table theory of speleogenesis and the concept that base level positions the water table. At the USA type example of glacial control of cave levels—Mammoth Cave in the Paleozoic rocks of Kentucky—the intermediary is base level determined by rivers. By hypothesis, the intermediary for Florida is glacioeustatic sea level. This paper presents elevation data that supports this hypothesis. Recent cave surveys in the air-filled caves and spot elevations from archived maps reveal prominent levels of passages centered at 5, 12, 21, and 30 m above sea level over broad areas. They do not follow the large-scale structure of the Floridan aquifer. Instead, they align with nearby, coastal marine terraces identified as modal peaks on frequency plots from various topographic data bases. Levels matching with the three highest terraces—Wicomico, Penholoway, and Talbott—are particularly clear. Lower levels, if they accord with sea-level stands, are likely composites. Data from cavities encountered in drilled wells (e.g., bit drops) and spot elevations from archived underwater cave maps demonstrate passage levels at depths of 15, 30, 70, and 90 120 m below the modern water table. The depths below water table are similar to the depths below sea level of distant submerged terraces and paleoshoreline features identified using multibeam bathymetric data in the Gulf of Mexico. The cave, bit-drop, and terrace data are all consistent with the concept that Quaternary sea level is the fundamental control on the cave-scale porosity within the Floridan aquifer. This conclusion does not rule out the possibility that lithologically favored positions, paleokarst features and confining units, and mixing zones are also involved in the location of caves levels in this near-coastal environment.

Florea, Lee J.; Vacher, H. L.; Donahue, Brian; Naar, David

2007-05-01

112

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

113

Fission neutron source in Rome  

Microsoft Academic Search

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,

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

1997-01-01

114

Nuclear Fission Industry In Japan  

Microsoft Academic Search

The Status of the nuclear fission industry in Japan is described. Japanese nuclear policy, vision, goals, and supporting organizational structures are reviewed. The facilities of the Japanese Atomic Energy Research Institute (JAERI), Power Reactor and Nuclear Fuel Development Corporation (PNC), and the Japan Atomic Power Company (JAPCO) are illustrated and described. Nuclear power statistics and power generation costs by power

Floyd A Wyczalek

1990-01-01

115

Fluidized bed nuclear fission reactor  

Microsoft Academic Search

For the further development of nuclear fission reactors, the feasibility of a new concept is evaluated. It concerns a fluidized bed reactor in which carbon particles with a uranium core are fluidized and cooled by a high velocity pressurized helium flow. Nuclear reaction takes place if the bed is in fluidized conditions at a void fraction above 80% and it

T. H. J. J. Van Der Hagen; H. Van Dam

1996-01-01

116

Advanced Space Fission Propulsion Systems.  

National Technical Information Service (NTIS)

Fission has been considered for in-space propulsion since the 1940s. Nuclear Thermal Propulsion (NTP) systems underwent extensive development from 1955-1973, completing 20 full power ground tests and achieving specific impulses nearly twice that of the be...

M. G. Houts S. K. Borowski

2010-01-01

117

Delayed gamma Rays from Fission.  

National Technical Information Service (NTIS)

Measurements of the energy spectrum of delayed gamma rays from the neutron fission of PU239 and U235 were performed with a naI detector at a number of time intervals between 2 and 80 microsec. The data showed three new prominent gamma rays with energies o...

R. B. Walton R. E. Sund

1966-01-01

118

Fission Fragment Excited Laser System.  

National Technical Information Service (NTIS)

A laser system and method for exciting lasing action in a molecular gas lasing medium includes cooling the lasing medium to a temperature below about 150 K and injecting fission fragments through the lasing medium so as to preferentially excite low lying ...

D. A. McArthur P. B. Tollefsrud

1976-01-01

119

Quark Bags and Their Fission.  

National Technical Information Service (NTIS)

The aim of this work is to gain more insight into the physics of hadrons and to develop a theoretical framework for the treatment of hadronic fission. The description of hadronic matter in terms of quantum chromodynamics, which is generally accepted as th...

D. Vasak

1985-01-01

120

Evaluation of Fission Product Afterheat.  

National Technical Information Service (NTIS)

This report covers work under the subject contract during the spring quarter of 1977. The goal of the contract is to improve the understanding of shutdown power in reactors due to radioactive decay of fission products, particularly for light water reactor...

B. I. Spinrad

1977-01-01

121

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

122

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

123

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

2011-01-15

124

Stereocontrolled Alkylative Construction of Quaternary Carbon Centers  

PubMed Central

Protocols for the stereodefined formation of ?,?-disubstituted enolates of pseudoephedrine amides are presented followed by the implementation of these in diastereoselective alkylation reactions. Direct alkylation of ?,?-disubstituted pseudoephedrine amide substrates is demonstrated to be both efficient and diastereoselective across a range of substrates, as exemplified by alkylation of the diastereomeric pseudoephedrine ?-methylbutyramides, where both substrates are found to undergo stereospecific replacement of the ?-C-H bond with ?-C-alkyl, with retention of stereochemistry. This is shown to arise by sequential stereospecific enolization and alkylation reactions, with the alkyl halide attacking a common ?-face of the E- and Z-enolates, proposed to be that opposite the pseudoephedrine alkoxide side-chain. Pseudoephedrine ?-phenylbutyramides are found to undergo highly stereoselective but not stereospecific ?-alkylation reactions, which evidence suggests is due to facile enolate isomerization. Also, we show that ?, ?-disubstituted pseudoephedrine amide enolates can be generated in a highly stereocontrolled fashion by conjugate addition of an alkyllithium reagent to the s-cis-conformer of an ?-alkyl-?,?-unsaturated pseudoephedrine amide, providing ?,?-disubstituted enolate substrates that undergo alkylation in the same sense as those formed by direct deprotonation. Methods are presented to transform the ?-quaternary pseudoephedrine amide products into optically active carboxylic acids, ketones, primary alcohols, and aldehydes.

Kummer, David A.; Chain, William J.; Morales, Marvin R.; Quiroga, Olga; Myers, Andrew G.

2009-01-01

125

Quaternary structure of hemoglobin in solution  

NASA Astrophysics Data System (ADS)

Many important proteins perform their physiological functions under allosteric control, whereby the binding of a ligand at a specific site influences the binding affinity at a different site. Allosteric regulation usually involves a switch in protein conformation upon ligand binding. The energies of the corresponding structures are comparable, and, therefore, the possibility that a structure determined by x-ray diffraction in the crystalline state is influenced by its intermolecular contacts, and thus differs from the solution structure, cannot be excluded. Here, we demonstrate that the quaternary structure of tetrameric human normal adult carbonmonoxy-hemoglobin can readily be determined in solution at near-physiological conditions of pH, ionic strength, and temperature by NMR measurement of 15N-1H residual dipolar couplings in weakly oriented samples. The structure is found to be a dynamic intermediate between two previously solved crystal structures, known as the R and R2 states. Exchange broadening at the subunit interface points to a rapid equilibrium between different structures that presumably include the crystallographically observed states.

Lukin, Jonathan A.; Kontaxis, Georg; Simplaceanu, Virgil; Yuan, Yue; Bax, Ad; Ho, Chien

2003-01-01

126

Fission yield studies at the IGISOL facility  

NASA Astrophysics Data System (ADS)

Low-energy-particle-induced fission is a cost-effective way to produce neutron-rich nuclei for spectroscopic studies. Fission has been utilized at the IGISOL to produce isotopes for decay and nuclear structure studies, collinear laser spectroscopy and precision mass measurements. The ion guide technique is also very suitable for the fission yield measurements, which can be performed very efficiently by using the Penning trap for fission fragment identification and counting. The proton- and neutron-induced fission yield measurements at the IGISOL are reviewed, and the independent isotopic yields of Zn, Ga, Rb, Sr, Cd and In in 25MeV deuterium-induced fission are presented for the first time. Moving to a new location next to the high intensity MCC30/15 light-ion cyclotron will allow also the use of the neutron-induced fission to produce the neutron rich nuclei at the IGISOL in the future.

Penttilä, H.; Elomaa, V.-V.; Eronen, T.; Hakala, J.; Jokinen, A.; Kankainen, A.; Moore, I. D.; Rahaman, S.; Rinta-Antila, S.; Rissanen, J.; Rubchenya, V.; Saastamoinen, A.; Weber, C.; Äystö, J.

2012-04-01

127

Morphology of fission gas bubbles in fissioning uranium metal closely  

NASA Astrophysics Data System (ADS)

We investigate by SEM the micro-structural and basic phenomenological mechanisms governing the fission-gas and fusion-gas behaviour in metals. This comparative study clearly shows the characteristics of fission-gas bubbles (primarily helium and xenon) in uranium fuel metals have the same characteristics as fusion-gas bubbles (helium) in the solid-state fusion metal - palladium. The remarkably similar characteristic morphology clearly identifies the nuclear phenomenological origins of the gas bubbles in the palladium metal which are correllated and explained by the presence of a large amount of DD fusion. Allied evidence of anomalous heat production during cold fusion experiments suggests the nuclear process. Further analysis of these fusion metals by mass spectroscopy clearly identifies anomalous helium isotopes in large quantity were trapped in the palladium metal.

George, Russ

2005-03-01

128

DSP Algorithms for Fission Fragment and Prompt Fission Neutron Spectroscopy  

SciTech Connect

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

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

2009-10-29

129

Proliferation resistant fission energy systems  

SciTech Connect

Fission energy systems that significantly reduce the need for the user country to be involved in the nuclear operations and technology could simplify implementation and reduce the proliferation potential. Conceptual system designs with improved (relative to the once-through LWR fuel cycle) proliferation resistance for application in developing countries are being evaluated. The fission energy systems being studied include all activities and equipment necessary to produce energy, recycle selected materials, and dispose of the waste. The systems currently being studied are required to function with no refueling of the reactors on the user site. These requirements are being used to initiate the study, on the assumption that removal of these operations from within the developing countries will improve the proliferation resistance. Preliminary evaluations of a small fast reactor core cooled either by sodium or lead-bismuth are provided.

Brown, N. W., LLNL

1997-07-02

130

The isotope hydrology of Quaternary climate change.  

PubMed

Understanding the links between climate change and human migration and culture is an important theme in Quaternary archaeology. While oxygen and hydrogen stable isotopes in high-latitude ice cores provide the ultimate detailed record of palaeoclimate extending back to the Middle Pleistocene, groundwater can act as a climate archive for areas at lower latitudes, permitting a degree of calibration for proxy records such as lake sediments, bones, and organic matter. Not only can oxygen and hydrogen stable isotopes be measured on waters, but the temperature of recharge can be calculated from the amount of the atmospheric noble gases neon, argon, krypton, and xenon in solution, while residence time can be estimated from the decay of the radioisotopes carbon-14, chlorine-36, and krypton-81 over timescales comparable to the ice core record. The Pleistocene-Holocene transition is well characterised in aquifers worldwide, and it is apparent that isotope-temperature relationships of the present day are not necessarily transferable to past climatic regimes, with important implications for the interpretation of proxy isotope data. Groundwaters dating back to one million years, i.e., to beyond the Middle Pleistocene, are only found in major aquifer basins and information is relatively sparse and of low resolution. Speleothem fluid inclusions offer a way of considerably increasing this resolution, but both speleothem formation and large-scale groundwater recharge requires humid conditions, which may be relatively infrequent for areas currently experiencing arid climates. Both types of record therefore require caution in their interpretation when considering a particular archaeological context. PMID:21051074

Darling, W G

2010-11-03

131

Fission properties for r-process nuclei  

NASA Astrophysics Data System (ADS)

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

Erler, J.; Langanke, K.; Loens, H. P.; Martínez-Pinedo, G.; Reinhard, P.-G.

2012-02-01

132

Energy partition in nuclear fission  

Microsoft Academic Search

A scission point model (two spheroid model TSM) including semi-empirical, temperature-dependent shell correction energies for deformed fragments at scission is presented. It has been used to describe the mass-asymmetry-dependent partition of the total energy release on both fragments from spontaneous and induced fission. Characteristic trends of experimental fragment energy and neutron multiplicity data as function of incidence energy in the

A. Ruben; H. Märten; D. Seeliger

1991-01-01

133

Laser driven fusion fission hybrids  

Microsoft Academic Search

The role of the fusion-fission hybrid reactor (FFHR) as a fissile fuel and\\/or power producer is discussed. As long range options to supply the world energy needs, hybrid-fueled thermal-burner reactors are compared to liquid metal fast breeder reactors (LMFBR). A discussion of different fuel cycles (thorium, depleted uranium, and spent fuel) is presented in order to compare the energy multiplication,

L. F. Hansen; J. A. Maniscalco

1977-01-01

134

Superconductivity enhanced by Hg fission  

NASA Astrophysics Data System (ADS)

For the successful application of high-temperature copper oxide superconductors, the problem of the ease of motion of magnetic vortices (quantized flux lines) within the material must be solved. The motion results in finite electrical resistance which prevents the desired loss-free conduction of current. We demonstrate a solution to this problem by anchoring the vortices with crystallographic defects induced by fission of mercury atoms in a mercury/copper oxide superconductor.

Krusin-Elbaum, L.; Lopez, D.; Thompson, J. R.; Wheeler, R.; Ullmann, J.; Chu, C. W.; Lin, Q. M.

1997-09-01

135

Fission fusion hybrids- recent progress  

NASA Astrophysics Data System (ADS)

Fission-fusion hybrids enjoy unique advantages for addressing long standing societal acceptability issues of nuclear fission power, and can do this at a much lower level of technical development than a competitive fusion power plant- so it could be a nearer term application. For waste incineration, hybrids can burn intransigent transuranic residues (with the long lived biohazard) from light water reactors (LWRs) with far fewer hybrid reactors than a comparable system within the realm of fission alone. For fuel production, hybrids can produce fuel for ˜4 times as many LWRs with NO fuel reprocessing. For both waste incineration or fuel production, the most severe kind of nuclear accident- runaway criticality- can be excluded, unlike either fast reactors or typical accelerator based reactors. The proliferation risks for hybrid fuel production are, we strongly believe, far less than any other fuel production method, including today's gas centrifuges. US Thorium reserves could supply the entire US electricity supply for centuries. The centerpiece of the fuel cycle is a high power density Compact Fusion Neutron Source (major+minor radius ˜ 2.5-3.5 m), which is made feasible by the super-X divertor.

Kotschenreuther, M.; Valanju, P.; Mahajan, S.; Covele, B.

2012-03-01

136

Quaternary naltrexone reverses radiogenic and morphine-induced locomotor hyperactivity  

SciTech Connect

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

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

1984-04-01

137

Neutron threshold activation detectors (TAD) for the detection of fissions  

Microsoft Academic Search

Prompt fission neutrons are one of the strongest signatures of the fission process. Depending on the fission inducing radiation, their average number ranges from 2.5 to 4 neutrons per fission. They are more energetic and abundant, by about 2 orders of magnitude, than the delayed neutrons (?3 vs. ?0.01) that are commonly used as indicators for the presence of fissionable

Tsahi Gozani; John Stevenson; Michael J. King

2011-01-01

138

New fission track ages of tektites and related glasses  

Microsoft Academic Search

Fission track dating is applied to a large number of australites, Muong Nong type tektites, Darwin glasses and Libyan Desert glasses. It is found that these glasses often have lowered fission track ages due to annealing effects. The same specimens have also smaller fission track etch pits. According to the diminishing percentage of etched fossil fission track diameters, lowered fission

W. Gentner; D. Storzer; G. A. Wagner

1969-01-01

139

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

140

?-ray studies of the fission of 238U induced by 12C, spectroscopy and fission dynamics  

NASA Astrophysics Data System (ADS)

Fission studies have been known for a long time to provide neutron-rich nuclei in various states of excitation energy, spin and deformation. Although many studies have been performed concerning fission fragments from spontaneous fission and neutron induced fission, a renewed interest in fission-fragment spectroscopy has occurred with the elaboration of large Ge detector arrays such as EUROBALL. We have recently performed an experiment with EUROBALL III using SAPhIR; a fission-fragment detector made from photovoltaic cells. The compact and versatile geometry of SAPhIR allows it to be installed inside the ?-ray detector, and to obtain additional information from the fission process as well as a timing reference. Neutron-rich nuclei have been populated in the fusion-fission reaction 238U+12C leading to the compound nucleus 250Cf. First results of this experiment are presented.

Houry, M.; Korten, W.; Le Coz, Y.; Lucas, R.; Theisen, Ch.; Barreau, G.; Doan, T. P.; Aiche, M.; Aleonard, M. M.; Chemin, J. F.; Scheurer, J. N.; Belier, G.; Meot, V.; Ethvignot, Th.; Durell, J.; Grimwood, D.; Phillips, W. R.; Roach, A.; Smith, A. G.; Varley, B. J.; Deloncle, I.; Porquet, M. G.; Astier, A.; Perries, S.; Redon, N.

1998-10-01

141

Quaternary tectonics of the southeastern coastal area, Korea: subsidence of marine terrace and late Quaternary faults  

NASA Astrophysics Data System (ADS)

Strong earthquake has rarely occurred in Korean peninsula and a few events were recorded since 27 A.D. Historical and recent earthquakes are concentrated in the southeastern area of Korean peninsula, where more than 30 Quaternary fault exposures have recently been founded. The southern tip of the southeastern coastal area has been known as a stable block: quaternary fault and micro-earthquakes haven’t occurred. To clarify whether the active tectonic movement is or not, digital marine terrace mapping and fracture mapping have been done for the southeastern coastal area. The area is composed of the Late Cretaceous volcanic rocks, sedimentary rocks and the Early Tertiary granite. Wave-cut platform in the area is comparatively smaller and narrower than that of other southeastern parts. Most of platforms have no Quaternary sediments and or very thin sediments. Platforms except the Holocene are generally divided into three steps. The lowest platform has a height of 8-11m. The middle one is broad with a height of 17 to 22m. The highest is narrowly scattered with a height of 33-41m. The lowest platform is correlated to the 2nd terrace of the northern area, which has been attributed to the isotopic substage, 5a. The uplift rate based on the altimetrical and indirect chronological data ranges from 0.072-0.108 m/ky. Such a low uplift rate indicates that the area is very stable because of belonging to intra-plate or continental block. The elevation of platform is getting lower from the north to the south. Reducing altitude of platform towards the south might be interpreted to a local block tilting within Yangsan Fault Belt during the Latest Pleistocene or an active tectonic subsidence to the south throughout the whole Korean peninsula. Several Quaternary faults supporting the active tectonic movement have been found from marine terrace feature mapping. Two sites have been proved the presence of fault by geophysical survey and cut-slope. Flight of marine terrace at two fault sites inclines slowly to the inland side and shows topographically vertical offset with small amount. Local block tilting and subsiding platforms from the north to the south are both due to the active tectonic fault movement of the Latest Pleistocene. Accompanied reverse Pleistocene faults dip to the east and show the top-up-to-the-west reverse movement sense. GPS measurement revealed the west of northwestern vector. Differential tectonic stress regime to the west has occurred to Korean peninsula during the Latest Pleistocene. Stronger tectonic force from the Pacific Ocean Plate gave an effect of high platform to the northern area. Weaker dynamic force due to the Philippine Plate caused low elevation to the southern area.

Choi, S.-J.; Ota, Y.; Chwae, U.

2003-04-01

142

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

143

Studies of corrosion inhibitors for zinc–manganese batteries: quinoline quaternary ammonium phenolates  

Microsoft Academic Search

Three compounds, hydroxyethyl quinoline quaternary ammonium phenolate, hydroxyethyl quinoline quaternary ammonium para-methyl phenolate and hydroxyethyl quinoline quaternary ammonium para-nitro phenolate were synthesized and tested as corrosion inhibitors for zinc–manganese batteries. Such quaternary ammonium salts derived from heterocylic molecule containing N atoms possess a higher density electron cloud around the functional groups and provide a larger projective area. From the analysis

Dongshe Zhang; Lidong Li; Lixin Cao; Neifen Yang; Chubao Huang

2001-01-01

144

A CMOS Quaternary Threshold Logic Full Adder Circuit with Transparent Latch  

Microsoft Academic Search

A circuit that realizes the quaternary threshold logic full adder function with transparent latching has been realized in a standard polysilicon-gate CMOS technology. In its FOLLOW mode, the quaternary full adder accepts two quaternary inputs and a binary CARRY input, and develops a two-quaternary-digit output word that is the base-four sum of the inputs. In the HOLD mode, these output

1990-01-01

145

Considerations on the Probability of Nuclear Fission  

Microsoft Academic Search

A semiempirical equation for fission thresholds has been extended to include the effects of unpaired nucleons on the rate of spontaneous fission. Excitation functions for the (alpha, 4n) reactions of Ra226, Th230, and U236 have been measured. These results and reported cross sections for other (alpha, 4n) reactions in the heaviest elements have been analyzed in terms of fission and

Robert Vandenbosch; Glenn T. Seaborg

1958-01-01

146

Possibility of optically induced nuclear fission  

Microsoft Academic Search

The process of nuclear fission induced by nonlinear radiative coupling to atomic electrons is considered. For 248-nm radiation at an intensity of approx. =10²¹ W\\/cm², highly relativistic currents are produced which can couple to the fission mode of nuclear decay. With irradiation for a time of approx. =100 fs the results indicate a fission probability of approx. =10⁻⁵ for \\/sub

K. Boyer; T. S. Luk; C. K. Rhodes

1988-01-01

147

Scattering of protons by fission fragments  

Microsoft Academic Search

The scattering of protons emitted from the neck area of the fissioning nucleus by fission fragments has been computed by solving the time-independent part of the Schrodinger equation for the symmetric fission of 235U+n. The current density (j=(h\\/2 pi )\\/2mi)( psi *GRAD psi - Psi GRAD psi *) is calculated as a function of the final energy of the protons

A. J. Kordyasz

1980-01-01

148

A wavepacket description of ternary fission  

Microsoft Academic Search

Ternary fission is approximated by the time-dependent evolution of the alpha-particle wavepacket in the potential generated by two moving fission fragments from ternary fission of 235U+n. The time-dependent Schrodinger equation is solved numerically by a finite elements method on an axially symmetric spatial mesh. The time-dependent evolution of the wavepacket is presented. It is illustrated by contour maps of the

A. J. Kordyasz

1981-01-01

149

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

150

Fission of Uranium238 with Carbon Ions  

Microsoft Academic Search

Angular distributions and kinetic-energy spectra of fragments, and cross sections for fission of U238 with 63- to 124-Mev C12 ions, have been measured with the use of a silicon p-n junction detector. The distributions have been analyzed in terms of the formation of a compound nucleus and subsequent decay by evaporation of neutrons in competition with fission. The percent fission

T. Sikkeland; A. E. Larsh; G. E. Gordon

1961-01-01

151

Fission neutron output measurements at LANSCE  

Microsoft Academic Search

Accurate data for both physical properties and fission properties of materials are necessary to properly model dynamic fissioning systems. To address the need for accurate data on fission neutron energy spectra, especially at outgoing neutron energies below about 200 keV and at energies above 8 MeV, ongoing work at LANSCE involving collaborators from LANL, LLNL and CEA Bruyeres-le-Chatel is extending

Ronald Owen Nelson; Robert C Haight; Matthew J Devlin; Nikolaos Fotiadis; Alexander Laptev; John M O Donnell; Terry N Taddeucci; Fredrik Tovesson; J L Ullmann; Stephen A Wender; T A Bredeweg; M Jandel; D J Vieira; Ching-Yen Wu; J A Becker; M A Stoyer; R Henderson; M Sutton; Gilbert Belier; A Chatillon; Thierry Granier; Benoit Laurent; Julien Taieb

2010-01-01

152

RECOVERY OF ALUMINUM FROM FISSION PRODUCTS  

DOEpatents

A method is given for recovertng aluminum values from aqueous solutions containing said values together with fission products. A mixture of Fe/sub 2/O/ sub 3/ and MnO/sub 2/ is added to a solution containing aluminum and fission products. The resulting aluminum-containing supernatant is then separated from the fission product-bearing metal oxide precipitate and is contacted with a cation exchange resin. The aluminum sorbed on the resin is then eluted and recovered. (AEC)

Blanco, R.E.; Higgins, I.R.

1962-11-20

153

Tyrosine urea muscarinic acetylcholine receptor antagonists: achiral quaternary ammonium groups.  

PubMed

Tyrosine ureas had been identified as potent muscarinic receptor antagonists with promising in vivo activity. Controlling the stereochemistry of the chiral quaternary ammonium center had proved to be a serious issue for this series, however. Herein we describe the preparation and SAR of tyrosine urea antagonists containing achiral quaternary ammonium centers. The most successful such moiety was the 2-methylimidazo[2,1-b][1,3]thiazol-7-ium group which yielded highly potent antagonists with long duration of action in an inhaled animal model of bronchoconstriction. PMID:23099092

Jin, Qi; Davis, Roderick S; Bullion, Ann M; Jin, Jian; Wang, Yonghui; Widdowson, Katherine L; Palovich, Michael R; Foley, James J; Schmidt, Dulcie B; Buckley, Peter T; Webb, Edward F; Salmon, Michael; Belmonte, Kristen E; Sarau, Henry M; Busch-Petersen, Jakob

2012-10-02

154

A quaternary logic encoder-decoder circuit design using CMOS  

NASA Astrophysics Data System (ADS)

A binary-to-quaternary encoder and quaternary-to-binary decoder circuit pair is described as designed in a 5-volt CMOS technology. These circuits communicate with logical currents. Using model parameter values for a standard 5-micron polysilicon gate process technology and 10 microamp logical currents, we have simulated propagation delays of about 20 ns from binary encoder input to binary decoder output. with the encoder using scaled-up logical currents and driving a 100 pF load on the decoder input to simulate communication between chips, we observe simulated worst-case delays of about 35ns.

Freitas, D. A.; Current, K. W.

155

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

156

Quaternary glaciation of the Himalayan-Tibetan orogen  

Microsoft Academic Search

ABSTRACT: Glacial geological,evidence,from,throughout,the,Himalayan–Tibetan,orogen,is examined,to determine,the timing and,extent of late Quaternary,glaciation in this region and,its relation to similar changes,on a global scale. The evidence,summarised,here supports the existence of expanded,ice caps,and,extensive,valley glacier systems,throughout,the region,during,the late Quaternary. However, it cannot yet be determined whether the timing of the extent of maximum glaciation was synchronous,throughout,the entire region or whether,the response was more,varied. The lack

Lewis A. Owen; Marc W. Caffee; Robert C. Finkel; Yeong Bae Seong

2008-01-01

157

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

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 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...

2013-07-01

158

Calculated medium-energy fission cross sections  

SciTech Connect

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

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

1988-01-01

159

METHOD FOR SEPARATING PLUTONIUM AND FISSION PRODUCTS EMPLOYING AN OXIDE AS A CARRIER FOR FISSION PRODUCTS  

DOEpatents

Carrier precipitation processes for separating plutonium values from uranium fission products are described. Silicon dioxide or titanium dioxide in a finely divided state is added to an acidic aqueous solution containing hexavalent plutonium ions together with ions of uranium fission products. The supernatant solution containing plutonium ions is then separated from the oxide and the fission products associated therewith.

Davies, T.H.

1961-07-18

160

Thermochromatographic Investigations of Fission Product Transport and Chemistry.  

National Technical Information Service (NTIS)

A thermochromatographic technique has been developed to investigate the chemical states of fission products from irradiated fuel as well as in fission product simulation studies. Some recent work on iodine transport and on release of fission products from...

F. B. Growcock S. Aronson M. Friedlander J. Skalyo A. Hosseini

1978-01-01

161

Spallation - Neutrons Beyond Nuclear Fission  

NASA Astrophysics Data System (ADS)

The classical research neutron sources are fission reactors. They have reached their technical limits as far as neutron flux is concerned. But there is an alternative way with many advantages: spallation. The emphasis in this context is on pulsed operation, which is easily achieved with spallation as being accelerator-driven. The extension of neutron scattering to fields not covered with reactors is discussed as well as the utilization of spallation neutrons for other fields such as nuclear waste transmutation and future power reactors.

Conrad, Harald

162

Hydroclimatic interpretation of Quaternary shorelines on South Australian playas  

Microsoft Academic Search

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

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

1998-01-01

163

Adsorption of some quaternary onium salts on silica gel  

Microsoft Academic Search

The adsorption of quaternary onium salts such as hexadecyltrimethylammonium chloride, hexadecyltrimethylammonium bromide, benzyltrimethylammonium chloride and tetrabutylammonium bromide from aqueous solution, and of tricaprylylmethylammonium chloride (Aliquat® 336) and hexadecyltributyl phosphonium bromide from organic solution has been studied using silica as an adsorbent. The adsorption from the aqueous phase was found to be dependent on the pH of the medium, giving a

A. C. Ghosh; K. Satyanarayana; R. C. Srivastava; N. N. Dutta

1995-01-01

164

Bacterial resistance to disinfectants containing quaternary ammonium compounds  

Microsoft Academic Search

Quaternary ammonium compounds (QAC) are widely used as disinfectants in both medical and food environments. Microbial contaminants are, therefore, regularly exposed to their action and the isolation from clinical and food sources of resistant bacteria continues to be reported in many countries. Resistance to QAC in clinical strains of staphylococci is encoded by one of at least three resistance genes,

G. Sundheim; S. Langsrud; E. Heir; A. L. Holck

1998-01-01

165

Supernormal optical characteristics in doped quaternary ammonium salt KDP crystals  

Microsoft Academic Search

Potassium dihydrogen phosphate, KH2PO4 (KDP) crystals with different concentrations of quaternary ammonium salt in solution were grown. In this paper, unusual transmittance ratio properties of KDP are reported. The transmittance ratio is smaller than unity at some locations. These results indicate that the plane wave effect and optical activity are highly displaced in KDP crystals, and the effect is varies

Xin-guang Xu; Xun Sun; Zheng-ping Wang; Gui-bao Xu; Zong-shu Shao; Zhang-shou Gao

2003-01-01

166

Photoluminescence Studies of InGaAlAs Quaternary Alloys.  

National Technical Information Service (NTIS)

Photoluminescence data are used to obtain the concentration and temperature dependence of the bandgap energies of epitaxial layers of quaternary alloy In/sub 0.1/Ga/sub x/Al/sub y/As for Al concentrations less than 0.6. The samples were grown by MBE witho...

E. D. Jones L. R. Dawson

1988-01-01

167

Quaternary Bimodal Volcanism in Acigol area, Cappadocia - Turkiye  

NASA Astrophysics Data System (ADS)

Cappadocia is famous with its splendid ignimbritic landscape which occurred during Miocene. The volcanic activity continued during Pliocene and Quaternary. Quaternary volcanism in Acigöl sector is represented by bimodal basaltic and rhyolitic products with a lack of intermediate compositions. Basaltic volcanic products (~47% SiO2) are characterized by diffuse monogenetic scoria cones and associated lava flows. Moreover, fissural basaltic activity is observed along N-S trending crack network. Preliminary petrographical studies indicate that basaltic products are hypocrystalline-porphyritic olivine basalts. Quaternary rhyolitic volcanism is represented by domes, dome complexes, associated lava flows and phreatomagmatic eruption centers. Besides, occurrences of spherulite bearing vitric rhyolitic intrusions are present along the probable boundary of a Miocene caldera, which is thought to be the source region for the Cappadocian ignimbrites. Rhyolitic lavas (74 -77% SiO2) are dominantly aphyric with slight transition from meta/peraluminous towards peralkaline whole rock compositions (Agpaitic Index: 0,91 - 0,96). However, Agpaitic Indices on volcanic glass are usually greater than unity. Occurrence of Quaternary bimodal basaltic - slightly peralkaline rhyolitic volcanism as well as N-S extensional tectonic features would be the result of possible intraplate rifting processes.

Cubukcu, H. E.; Aydar, E.; Sen, E.; Bayhan, H.

2009-04-01

168

Impact of quaternary structure dynamics on allosteric drug discovery.  

PubMed

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. PMID:23409765

Jaffe, Eileen K

2013-01-01

169

Late Quaternary Lake-Level Record from Northern Eurasia  

Microsoft Academic Search

Lake records from northern Eurasia show regionally coherent patterns of changes during the late Quaternary. Lakes peripheral to the Scandinavian ice sheet were lower than those today but lakes in the Mediterranean zone were high at the glacial maximum, reflecting the dominance of glacial anticyclonic conditions in northern Europe and a southward shift of the Westerlies. The influence of the

Sandy P. Harrison; Ge Yu; Pavel E. Tarasov

1996-01-01

170

Quaternary phosphorites off the southeast coast of India  

Microsoft Academic Search

Detailed petrological, mineralogical, geochemical and radiogenic (U, Sr, Nd) and stable isotope (C, O, S) studies have been carried out on the Quaternary phosphorites of the continental margin off Chennai, southeast coast of India. These phosphorites are formed as a result of trapping and binding of sediments by microbial mats and are similar to phosphate stratiform stromatolites. Detrital and biogenic

V. Purnachandra Rao; A Michard; S. W. A Naqvi; M. E Böttcher; Rama Krishnaswamy; M Thamban; R Natarajan; D. V Borole

2002-01-01

171

The sequence of Quaternary glaciation in the Bayan Har Mountains  

Microsoft Academic Search

Four periods of Quaternary glaciation in the Pleistocene have been found in the area of the Bayan Har Mountains. They represent, respectively, the two stages of the Last Glacial age; the penultimate ice age, and an earlier ice age. During the late stage of the Last Glacial age, glaciers developed only near the mountain ridges of the Bayan Har. In

Shangzhe Zhou; Jijun Li

1998-01-01

172

Late Quaternary evolution of Riverine Plain paleochannels, southeastern Australia  

Microsoft Academic Search

The Riverine Plain of southeastern Australia is the result of prolonged Cenozoic fluvial activity associated with the Murray River and its major southern tributaries, the Murrumbidgee, Goulburn and Lachlan. Single thread, distributary and anabranching channels and floodplains with associated eolian dunes and lunette-bordered lake basins characterise the uppermost sequences of the Late Quaternary. Following 30 years of detailed mapping and

K. J. Page; J. Kemp; G. C. Nanson

2009-01-01

173

Quaternary research in Poland: selected achievements and prospects  

Microsoft Academic Search

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

Leszek Marks

174

The Late Quaternary glaciation of Africa: A regional synthesis  

Microsoft Academic Search

There are numerous mountain ranges in Africa which carry evidence of Quaternary glaciation, though few have glaciers now and these are rapidly disappearing. The best studied sites are in East Africa and Ethiopia. In East Africa, the three highest mountains, Kilimanjaro, Kenya and the Rwenzori, each have evidence of 3–5 major glaciations dating back to an estimated 400,000 BP, one

Henry A. Osmaston; Sandy P. Harrison

2005-01-01

175

Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information  

ERIC Educational Resources Information Center

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

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

2011-01-01

176

Formal Quaternary stratigraphy—What do we expect and need?  

Microsoft Academic Search

At the start of my INQUA career a reasonable target for the long-term development of Quaternary stratigraphy was the construction of a table that listed a number (perhaps fewer than a dozen, perhaps more) of “stages” for each of the chief regions of the Earth, and which reliably indicated how these stages should be correlated from region to region. A

N. J. Shackleton

2006-01-01

177

Formal Quaternary stratigraphy---What do we expect and need?  

Microsoft Academic Search

At the start of my INQUA career a reasonable target for the long-term development of Quaternary stratigraphy was the construction of a table that listed a number (perhaps fewer than a dozen, perhaps more) of ``stages'' for each of the chief regions of the Earth, and which reliably indicated how these stages should be correlated from region to region. A

N. J. Shackleton

2006-01-01

178

Quaternary paleolake development in the Fen River basin, North China  

Microsoft Academic Search

The Taiyuan Graben and the Linfen Graben are two fault-controlled grabens in the Fen River basin, north China. Broad paleolakes periodically occupied the two grabens during the Pleistocene. This paper discusses how neotectonic activities and paleoclimate changes may have influenced the development of the paleolakes in the two grabens during the middle to late Quaternary, based on the lacustrine landforms

Xiaomeng Hu; Youli Li; Jingchun Yang

2005-01-01

179

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

180

Quaternary Naltrexone Reverses Radiogenic and Morphine-Induced Locomotor Hyperactivity.  

National Technical Information Service (NTIS)

The present study attempted to determine the relative role of the peripheral and central nervous system in the production of morphine-induced or radiation-induced locomotor hyperactivity of the mouse. Toward this end, we used a quaternary derivative of an...

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

1984-01-01

181

Quaternary Glacial Mapping in Western Wisconsin Using Soil Survey Information  

ERIC Educational Resources Information Center

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

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

2011-01-01

182

Quaternary ammonium sulfanilamide: a membrane-impermeant carbonic anhydrase inhibitor  

Microsoft Academic Search

A novel carbonic anhydrase (CA) inhibitor, quaternary ammonium sulfanilamide (QAS), was tested for potency as a CA inhibitor and for its ability to be excluded from permeating biological membranes. Inhibitor titration plots of QAS vs. pure bovine CA II and CA from the gills of the blue crab, Callinectes sapidus, yielded K\\/sub i\\/ values of approx. 15 ..mu..M; thus QAS

1987-01-01

183

Effects of Quaternary Sea Level Cycles on Strontium in Seawater  

Microsoft Academic Search

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

Heather M Stoll; Daniel P Schrag

1998-01-01

184

Quaternary glaciation in Africa: key chronologies and climatic implications  

Microsoft Academic Search

Multiple episodes of Quaternary glaciation are evidenced on >10 distinct mountain localities throughout Africa, with the best dated sites from Kilimanjaro and Mt Kenya in equatorial East Africa. A general paucity of radiogenic dates constrains the glacial chronology, and regional sequences have largely been based on correlations by relative weathering of features. Excellent glacial moraine preservation and other features of

Bryan G. Mark; Henry A. Osmaston

2008-01-01

185

Rapid separation of fresh fission products (draft)  

Microsoft Academic Search

The fission of highly eruiched uranium by thermal neutrons creates dozens of isotopic products. The Isotope and Nuclear Chemistry Group participates in programs that involve analysis of 'fiesh' fission products by beta counting following radiochemical separations. This is a laborious and time-consuming process that can take several days to generate results. Gamma spectroscopy can provide a more immediate path to

D. E. Dry; E. Bauer; L. A. Petersen

2003-01-01

186

Dosimetry of noble-gas fission products  

Microsoft Academic Search

In the first minutes and hours following a reactor accident, personnel at the reactor facility, and possibly members of the public at off-site locations may be subjected to significant radiation dose from exposure to the entire spectrum of noble gas fission products and their daughter radionuclides. In order to measure the immersion dose of noble gas fission products following the

P. J. T

1989-01-01

187

Fission Neutron Spectra and Nuclear Temperatures  

Microsoft Academic Search

It is shown that Weisskopf's nuclear evaporation theory, when allowance is made for the expected distribution of nuclear temperatures of fission fragments, predicts an essentially Maxwellian distribution of fission neutron energies in the laboratory system. This is found to be in excellent agreement with all available data. On the assumption that neutron emission is symmetrical about 90° in the center-of-mass

James Terrell

1959-01-01

188

Nuclear fission sustainability with hybrid nuclear cycles  

Microsoft Academic Search

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

José M. Martínez-Val; Mireia Piera

2007-01-01

189

Nuclear fission with a Langevin equation  

Microsoft Academic Search

A microscopically derived Langevin equation is applied to thermally induced nuclear fission. An important memory effect is pointed out and discussed. A strong friction coefficient, estimated from microscopic quantities, tends to decrease the stationary limit of the fission rate and to increase the transient time. The calculations are performed with a collective mass depending on the collective variable and with

David Boilley; Eric Suraud; Abe Yasuhisa; Sakir Ayik

1993-01-01

190

Spontaneous fission properties and lifetime systematics  

SciTech Connect

Half-lives for spontaneous fission of nuclides with even and odd numbers of particles are compared with recent theoretical calculations. A summary of odd particle hindrance factors is given. The most recent measurements of kinetic-energy and mass distributions and neutron emission for spontaneous fission of the heaviest nuclides are summarized and discussed. 51 refs., 9 figs.

Hoffman, D.C.

1989-03-01

191

Nuclear Power from Fission Reactors. An Introduction.  

ERIC Educational Resources Information Center

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

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

192

Spectroscopy of selected fission fragments  

SciTech Connect

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

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

1999-10-22

193

Theoretical Description of the Fission Process  

SciTech Connect

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

Witold Nazarewicz

2009-10-25

194

Prompt ? rays and neutrons from fission  

NASA Astrophysics Data System (ADS)

Nuclear data are needed to test the accuracy of calculations from nuclear reaction codes. Information on the prompt ?-ray distributions from fission is sparse and only a handful of published experiments data that measured the prompt ?-ray distribution above incident neutron energies of 1 MeV can be found. In addition, improvement on the accuracy and shape of neutron spectrum from the fission of actinides been requested by the nuclear data communityootnotetext``Prompt Fission Neutron Spectra of Major Actinides,'' INDC(NDS)-0571, ed. R. Capote Noy, (2010).. An investigation on the shapes of the neutron and ?-ray distributions from the spontaneous fission of ^252Cf and the neutron-induced fission of ^235U was undertaken using the Chi-Nu detector array at the Weapons Neutron Research Facility of the Los Alamos Neutron Science Center. Preliminary results will be presented.

Kwan, E.; Wu, C. Y.; Chyzh, A.; Gostic, J.; Henderson, R.; Haight, R. C.; Lee, H. Y.; O'Donnell, J. M.; Perdue, B. A.; Taddeucci, T. N.

2011-10-01

195

Event-by-Event Fission 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. The presentation first discusses the present status of FREYA, which has now been extended up to energies where pre-equilibrium emission becomes significant and one or more neutrons may be emitted prior to fission. Concentrating on {sup 239}Pu(n,f), we discuss the neutron multiplicity correlations, the dependence of the neutron energy spectrum on the neutron multiplicity, and the relationship between the fragment kinetic energy and the number of neutrons and their energies. We also briefly suggest novel fission observables that could be measured with modern detectors.

Randrup, J; Vogt, R

2010-11-09

196

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

197

Fission-energy release for 16 fissioning nuclides. Final report  

SciTech Connect

Results are presented of a least-squares evaluation of the components of energy release per fission in /sup 232/Th, /sup 233/U, /sup 235/U, /sup 238/U, /sup 239/Pu, and /sup 241/Pu. For completeness, older (1978) results based on systematics are presented for these and ten other isotopes of interest. There have been recent indications that the delayed energy components may be somewhat higher than those used previously, but the LSQ results do not seem to change significantly when modest (approx. 1 MeV) increases in the total delayed energy are included in the inputs. Additional measurements of most of the energy components are still needed to resolve remaining discrepancies.

Sher, R.

1981-03-01

198

Characterization of Quaternary and suspected Quaternary faults, regional studies, 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 that resulted in the identification of 51 relevant and potentially relevant individual and compound faults and fault zones in the 100-km-radius region around the Yucca Mountain site. Geologic data used to characterize the regional faults and fault zones as relevant or potentially relevant seismic sources includes age and displacement information, maximum fault lengths, and minimum distances between the fault and the Yucca Mountain site. For many of the regional faults, no paleoseismic field studies have previously been conducted, and age and displacement data are sparse to nonexistent. In November 1994, the Branch of Earthquake and Landslide Hazards entered into two Memoranda of Agreement with the Yucca Mountain Project Branch to conduct field reconnaissance, analysis, and interpretation of six relevant and six potentially relevant regional faults. This report describes the results of study of those faults exclusive of those in the Pahrump-Stewart Valley-Ash Meadows-Amargosa Valley areas. We also include results of a cursory study of faults on the west flank of the Specter Range and in the northern part of the Last Chance Range. A four-phase strategy was implemented for the field study.

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

1995-12-31

199

Laser driven fusion fission hybrids  

SciTech Connect

The role of the fusion-fission hybrid reactor (FFHR) as a fissile fuel and/or power producer is discussed. As long range options to supply the world energy needs, hybrid-fueled thermal-burner reactors are compared to liquid metal fast breeder reactors (LMFBR). A discussion of different fuel cycles (thorium, depleted uranium, and spent fuel) is presented in order to compare the energy multiplication, the production of fissile fuel, the laser efficiency and pellet gain requirements of the hybrid reactor. LLL has collaborated with Bechtel Corporation and with Westinghouse on the conceptual design of laser fusion power plants. The neutronic studies of these two designs are discussed. The operational parameters, such as energy multiplication, power density, burn-up and plutonium production as a function of time, are also presented.

Hansen, L.F.; Maniscalco, J.A.

1977-07-12

200

Future challenges for nuclear data research in fission (u)  

SciTech Connect

I describe some high priority research areas in nuclear fission, where applications in nuclear reactor technologies and in modeling criticality in general are demanding higher accuracies in our databases. We focus on fission cross sections, fission neutron spectra, and fission product data.

Chadwick, Mark B [Los Alamos National Laboratory

2010-01-01

201

Mitochondrial fission controls DNA fragmentation by regulating endonuclease G  

Microsoft Academic Search

Mitochondria constantly undergo fusion and fission that are necessary for the maintenance of organelle fidelity. However, growing evidence has shown that abnormal mitochondrial fusion and fission participate in the regulation of apoptosis. Mitochondrial fusion is able to inhibit apoptosis, whereas mitochondrial fission is involved in the initiation of apoptosis. It remains elusive as to whether mitochondrial fission can regulate DNA

Jincheng Li; Jing Zhou; Yanrui Li; Danian Qin; Peifeng Li

2010-01-01

202

?-delayed fission of 192,194At  

NASA Astrophysics Data System (ADS)

By using the recoil-fission correlation technique, the exotic process of beta-delayed fission (?DF) was unambiguously identified in the very neutron-deficient nuclei 192,194At in experiments at the velocity filter SHIP at Gesellschaft für Schwerionenforschung (GSI). The upper limits for the total kinetic energy release in fission of 192,194Po, being the daughter products of 192,194At after ?+/EC decay, were estimated. The possibility of an unusually high ?DF probability for 192At is discussed.

Andreyev, A. N.; Antalic, S.; Ackermann, D.; Bianco, L.; Franchoo, S.; Heinz, S.; Heßberger, F. P.; Hofmann, S.; Huyse, M.; Kalaninová, Z.; Kojouharov, I.; Kindler, B.; Lommel, B.; Mann, R.; Nishio, K.; Page, R. D.; Ressler, J. J.; Streicher, B.; Saro, S.; Sulignano, B.; Van Duppen, P.

2013-01-01

203

Ternary Fission Induced by Polarized Neutrons  

SciTech Connect

P-odd and T-odd asymmetries in the emission of fragments and light particles have been investigated in ternary fission induced by polarized neutrons. P-odd asymmetries unambiguously point to a violation of parity in the fission process. By contrast, T-odd asymmetries do not necessarily imply a violation of time reversal invariance. The asymmetries observed are rather due to a final state interaction between the light ternary particle and the nucleus from which they are ejected. New results with interesting information on the ternary fission process are presented.

Goennenwein, F.; Jesinger, P. [Physikalisches Institut, Universitaet Tuebingen, 72076 Tuebingen (Germany); Gagarski, A.; Petrov, G.; Bunakov, V. [Petersburg Nuclear Physics Institute, 188300 Gatchina (Russian Federation); Mutterer, M. [Institut fuer Kernphysik, Technische Universitaet, 64289 Darmstadt (Germany); Trzaska, W. [Department of Physics, Jyvaeskylae University, 40351 Jyvaeskylae (Finland); Nesvizhevsky, V.; Lelievre-Berna, E. [Institut Laue Langevin, 38042 Grenoble (France)

2005-05-24

204

Fusion-fission of heavy systems  

NASA Astrophysics Data System (ADS)

The influence of the entrance channel on fission processes was studied by forming the same composite system by two different target-projectile combinations (40Ar+209Bi and56Fe+187Re, respectively). Compound nucleus fission and quasi fission were observed and the analysis was performed in the framework of the extra-extra-push model, which provides a qualitative interpretation of the results; limits for the extra-extra-push threshold are given, but problems with quantitative predictions for the extra-push are noted.

Rivet, M. F.; Alami, R.; Borderie, B.; Fuchs, H.; Gardes, D.; Gauvin, H.

1988-09-01

205

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

206

Microscopic Calculations of Spontaneous Fission Life-times and Neutron-Induced Fission Cross Sections  

NASA Astrophysics Data System (ADS)

Fission potential-energy surfaces are calculated from a microscopic Hartree-Fock-Bogoliubov description of the deformed nucleus, fully constrained in the three deformation coordinates (c, h, ?). The dynamical fission paths along the multidimensional symmetric and asymmetric deformation space are determined by applying the classical least action principle. The resulting dynamical fission barriers and spontaneous fission half-lives are compared with the experimental values for 240Pu. Furthermore, microscopic calculations of fission barriers and nuclear level densities are used to obtain neutron-induced fission cross sections. The results for the actinides are compared with existing experimental data in the low energy region ~100 keV relevant to the r-process nucleosynthesis.

Demetriou, P.; Samyn, M.; Goriely, S.

2004-04-01

207

Microscopic Calculations of Spontaneous Fission Half-Lives and Neutron-Induced Fission Cross Sections  

NASA Astrophysics Data System (ADS)

Fission potential-energy surfaces are calculated from a microscopic Hartree-Fock-Bogoliubov description of the deformed nucleus, fully constrained in the three deformation coordinates c, h, ?. The dynamical fission paths along the multidimensional deformation space are determined by applying the classical least action principle. The resulting dynamical fission barriers and spontaneous fission half-life are compared with static calculations and experimental values for 240Pu. Furthermore, microscopic calculations of fission barriers and nuclear level densities are used to obtain neutron-induced fission cross sections. The results for the actinides are compared with existing experimental data in the low energy region ?100 keV relevant to the r-process nucleosynthesis.

Demetriou, P.; Samyn, M.; Goriely, S.

2004-02-01

208

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.

209

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.

2011-06-16

210

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

211

Probing enzyme quaternary structure by combinatorial mutagenesis and selection.  

PubMed Central

Genetic selection provides an effective way to obtain active catalysts from a diverse population of protein variants. We have used this tool to investigate the role of loop sequences in determining the quaternary structure of a domain-swapped enzyme. By inserting random loops of four to seven residues into a dimeric chorismate mutase and selecting for functional variants by genetic complementation, we have obtained and characterized both monomeric and hexameric enzymes that retain considerable catalytic activity. The low percentage of active proteins recovered from these selection experiments indicates that relatively few loop sequences permit a change in quaternary structure without affecting active site structure. The results of our experiments suggest further that protein stability can be an important driving force in the evolution of oligomeric proteins.

MacBeath, G.; Kast, P.; Hilvert, D.

1998-01-01

212

Directional Correlation of Fission Fragments and Prompt Gamma Rays Associated With Thermal Neutron Fission  

Microsoft Academic Search

Prompt fission gamma-ray intensity as a function of the angle from the fragment direction has been measured for the thermal neutron fission of U233, U235, and Pu239. For each of these three nuclides, the fission gamma rays were found to be emitted preferentially in the direction of fragment motion by as much as 15%. It was found that the experimental

Marvin M. Hoffman

1964-01-01

213

Map and Data for Quaternary Faults and Folds in Wyoming  

NSDL National Science Digital Library

The primary objective of this U.S. Geological Survey Open-file Report is to improve seismic-hazard assessments in regions of Wyoming with low to moderate levels of historic seismicity. A map and pamphlet are available for download in PDF format. The map shows faults and folds with evidence of Quaternary movement including data on timing of the most recent movement, sense of movement, slip rate, and continuity of surface expression.

Michael, Machette; Survey, U. S.

214

The new basic theory on Quaternary environmental research  

Microsoft Academic Search

On the basis of extensive survey to the Quaternary paleosols, soils and weathering layers in the vast northern China and the\\u000a Loess Plateau, we found some unusually special phenomena of chemical components such as unsuccessive illuvium, twin illuviums,\\u000a unusually thick illuvium and multi-illuviums etc. According to the analysis on the content of CaCO3 and the data of penetrating experiment, a

Zhao Jingbo

2004-01-01

215

Experiments for correlating quaternary carbons in RNA bases  

Microsoft Academic Search

The paper presents a set of triple-resonance two-dimensional experiments for correlating all quaternary carbons in RNA bases\\u000a to one or more of the base protons. The experiments make use of either three-bond proton-carbon couplings and one selective\\u000a INEPT step (the long-range selective HSQC experiment) to transfer the magnetization between a proton and the carbon of interest\\u000a and back, or they

Radovan Fiala; Markéta L. Munzarová; Vladimír Sklená?

2004-01-01

216

Vegetation ecotone dynamics in Southwest Alaska during the Late Quaternary  

Microsoft Academic Search

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

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

2001-01-01

217

Integrating Quaternary Science Research in Land Management, Restoration, and Conservation  

Microsoft Academic Search

Most of us have come to expect that the general public will ignore the primary message of Quaternary science that change happens. A flurry, however, of recent media attention to 20th-century global warming and its anomalies from climates of the last millennium has brought climate science at least momentarily into popular focus. Similarly, public land-managing agencies and conservation groups have

Constance I. Millar; Wallace B. Woolfenden

218

Quaternary faulting history along the Deep Springs fault, California  

Microsoft Academic Search

New geologic mapping, structural stud- ies, geochronology, and diffusion erosion modeling along the Deep Springs fault, Cal- ifornia, shed light on its Quaternary fault- ing history. The Deep Springs fault, a 26- km-long, predominantly north-northeast- striking, west-northwestdipping normal fault bounding the eastern side of Deep Springs Valley, cuts Jurassic batholithic rocks nonconformably overlain by middle Miocene to Pleistocene stream gravels,

Jeffrey Lee; Charles M. Rubin; Andrew Calvert

2001-01-01

219

Petrogenesis of Plio-Quaternary basalts in Mahabad, NW Iran  

NASA Astrophysics Data System (ADS)

The Mahabad1:100000 sheet is located mostly in the Kurdestan district on southern part of west Azerbijan province between east Longitude 45? 30'- 46 ?, and northern Latitude 36? 30'- 37?. Geographic position, geological and structural setting as well as general geological characters of this zone is very similar to Sanandaj-Sirjan zone. Topography is dominated by mountainous terrain with an average elevation around 1800 meters. The oldest rocks belong to intrusive rocks, Mahabad Rhyolite. The younger ones include Plio-Quaternary basalt to alkali basalt, andesite, trachyte and alluvium terraces and salt marsh. The young quaternary volcanoes occur in the southern range east and east of mahabad map sheet. The Plio-Quaternary volcanic lava are seen in the Borhan village? It is built almost entirely of fluid lava flows?. The volcanic rocks are basic in composition (basalt, tephrit basanite). The petrographic and geochemical evidences, related diagrams show fractionation. By studying the major and trace elements variation diagrams, a trend of normal crystallization can be seen crustal contamination in extensional environments. It seems that the original magma has an ultrabasic composition. Some of the phenocrysts of olivine, pyroxene & plagioclase are seen in thin sections. These rocks have microlitic porphyritic? hyallo microlithic porphyritic textures in thin sections. On the basis of chemical analysis? magma that has formed the rocks had alkaline nature. The ratio of nephelin norm is around 5.3 in this rocks. A primitive mantle- normalized incompatible trace element diagram shows close similarity to typical OIB pattern. All of documents denote that magma originated from an enriched asthenospheric mantle and low degree of partial melting in source. Key words: alkali basalt, Quaternary, Volcanic, Compression. asthenospher

Shojaei, Masoomeh; Kheirkhah, Monireh; Hashem Emami, Mohamad; Maleki, Glavig

2010-05-01

220

Titration of long-chain quaternary ammonium compounds using tetraphenylboron  

Microsoft Academic Search

A rapid macro procedure for the determination of long-chain quaternary ammonium compounds (QAC) has been developed using sodium\\u000a tetraphenylboron as a titrant. About 1–1.5 meq of QAC is dissolved or dispersed in 50 ml of water. Dichlorofluorescein is\\u000a added as an indicator. The sample is then titrated with 0.06 N aqueous sodium tetraphenylboron. As long as free QAC is present

L. D. Metcalfe; R. J. Martin; A. A. Schmitz

1966-01-01

221

Assay of quaternary ammonium antimicrobial compounds by aqueous potentiometric titration  

Microsoft Academic Search

An automatic potentiometric titration method for the determination of quaternary ammonium antimicrobial compounds at the macro\\u000a level is described. The procedure involves the use of standard sodium lauryl sulfate as the titrant and a nitrate ion-selective\\u000a or surfactant electrode to detect the end point. The method, which includes a new, simpler means of titrant standardization,\\u000a avoids the use of hazardous

George T. Battaglini

2002-01-01

222

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

223

The impact of Quaternary Ice Ages on mammalian evolution.  

PubMed Central

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.

Lister, Adrian M

2004-01-01

224

Late quaternary turnover of mammals in Borneo: the zooarchaeological record  

Microsoft Academic Search

The Quaternary has been a period of repeated, oscillating patterns of climate change. Global fluctuations in sea level affected\\u000a the island status of Borneo, which was probably joined to continental Asia for more than half of the last 250,000 years. Alternating\\u000a connection and isolation, coupled with the ecological barrier of a savanna corridor running from the Malay Peninsula to Java\\u000a during

2010-01-01

225

Geological provenance of Quaternary deposits from the southeastern Brazilian coast  

NASA Astrophysics Data System (ADS)

Natural gamma radiation measurements of beach sand deposits were performed with the aim of understanding the provenance and transport processes of sediments along the coastal zone of three Brazilian States. The method employs thorium, uranium and potassium as tracers of the mineralogical properties of beach sand minerals, which reflect the geological history of transport and sorting processes. A considerable positive correlation with the geological evolution of these Quaternary coastal deposits was observed.

Anjos, R. M.; Veiga, R.; Carvalho, C.; Macario, K. D.; Gomes, P. R. S.

2007-05-01

226

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

Microsoft Academic Search

We describe measurements of fission product data at Los Alamos that are important for determining the number of fissions that have occurred when neutrons are incident on plutonium and uranium isotopes. The fission-spectrum measurements were made using a fission chamber designed by the National Institute for Standards and Technology (NIST) in the BIG TEN critical assembly, as part of the

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

2010-01-01

227

Ternary and quaternary selenide crystals for nonlinear optical applications  

NASA Astrophysics Data System (ADS)

We have developed several binary, ternary and quaternary sulfide and selenide crystals for nonlinear optical applications and present an overview on the crystal growth and characterization of crystals for nonlinear optical (NLO) conversion efficiency. We have summarized the performance of silver gallium selenide (AgGaSe2), thallium arsenic selenide (Tl3AsSe3), and silver gallium germanium selenide (AgGaGe3Se8 and AgGaGe5Se12) crystals and have compared with gallium selenide (GaSe). All these crystals were grown by vertical Bridgman method in quartz ampoules by using stoichiometric compounds synthesized from constituent elements. The significant problem of cleaving of GaSe was reduced in ternary and quaternary compounds. Experimental results showed that binary, ternary and quaternary selenide compounds transmit at wavelengths up to 16 ?m, have reasonably high value of nonlinear conversion merit (d2/n3, where d is the NLO coefficient and n is the refractive index) and have the lowest absorption coefficient compared to arsenides, phosphides and other nonlinear optical (NLO) materials.

Singh, N. B.; Knuteson, D. J.; Kanner, G.; Berghmans, A.; Green, K.; Wagner, B.; Kahler, D.; King, M.; McLaughlin, S.

2011-09-01

228

THE COMPARATIVE CHARACTERISTICS OF TERNARY FISSION IN URANIUM AND PLUTONIUM  

Microsoft Academic Search

Data were accumulated on a total of 20,000 ternary fission events for ; the slow neutron fission of U²³³, 15,000 ternary fission events for U\\/sup ; 235\\/, and 12,000 fission events for Pu²³⁹. The sum of the energies of the ; fission fragments E⁠+ Eâ was plotted as a function of Eâ\\/E\\/sub ; 2\\/ for double an d ternary

V. N. Dmitriev; L. V. Drapchinskii; K. A. Petrzhak; Yu. F. Romanov

1963-01-01

229

Microscopic description of complex nuclear decay: Multimodal fission  

NASA Astrophysics Data System (ADS)

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

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

2009-07-01

230

Advanced modeling of prompt fission neutrons  

SciTech Connect

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

Talou, Patrick [Los Alamos National Laboratory

2009-01-01

231

TMI-2 Fission Product Inventory Estimates (Draft).  

National Technical Information Service (NTIS)

This report presents the results of analyses performed to estimate the inventory and distribution of selected radioisotopes within the TMI-2 reactor system. The intent of the report is to document the method used in estimating the fission product inventor...

E. L. Tolman M. Nishio

1987-01-01

232

Nuclear Fission and the Transuranium Elements.  

National Technical Information Service (NTIS)

Many of the transuranium elements are produced and isolated in large quantities through the use of neutrons furnished by nuclear fission reactions: plutonium (atomic number 94) in ton quantities; neptunium (93), americium (95), and curium (96) in kilogram...

G. T. Seaborg

1989-01-01

233

Porous fission fragment tracks in fluorapatite  

SciTech Connect

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

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

2010-10-01

234

Porous fission fragment tracks in fluorapatite  

NASA Astrophysics Data System (ADS)

Fission tracks caused by the spontaneous fission of U238 in minerals, as revealed by chemical etching, are extensively used to determine the age and thermal history of Earth’s crust. Details of the structure and annealing of tracks at the atomic scale have remained elusive, as the original track is destroyed during chemical etching. By combining transmission electron microscopy with in situ heating, we demonstrate that fission tracks in fluorapatite are actually porous tubes, instead of having an amorphous core, as generally assumed. Direct observation shows thermally induced track fragmentation in fluoapatite, in clear contrast to the amorphous tracks in zircon, which gradually “fade” without fragmentation. Rayleigh instability and the thermal emission of vacancies control the annealing of porous fission tracks in fluorapatite.

Li, Weixing; Wang, Lumin; Sun, Kai; Lang, Maik; Trautmann, Christina; Ewing, Rodney C.

2010-10-01

235

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

236

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

NASA Astrophysics Data System (ADS)

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

Chen, Chris; Cooper, Stuart

2000-03-01

237

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

238

A NEW FISSION PRODUCT: Ga⁷⁴  

Microsoft Academic Search

The 8 min Ga⁷⁴ was separated from the fission-products of U\\/sup ; 235\\/. The gallium activity was characterized as Ga⁷⁴ by comparison of its ; gamma -ray spectrum with that obtained from (n,p)-produced Ga⁷⁴. Chemical ; separation of the Ga⁷⁴ was effected by a combination of extraction, ; volatilization, ionexchange, and precipitation steps. Its fission yield was ; determined to

J. A. Marinsky; E. Eichler

1960-01-01

239

Laser Spectroscopy of Cooled Zirconium Fission Fragments  

Microsoft Academic Search

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

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

2002-01-01

240

Glass Dating by Fission Fragment Tracks  

Microsoft Academic Search

The use of fission fragment damage tracks for dating of geological and other glasses is described and applied to a number of tektites and a Libyan glass. By comparison with K-Ar and Rb-Sr dates the decay constant for spontaneous fission of U 8 is derived geo- logically to be 6.9 X 10 -7 yr-L Most of the tektite dates are

R. L. Fleischer; P. B. Price

1964-01-01

241

A new interpretation of asymmetric nuclear fission  

Microsoft Academic Search

Summary  Twelve arguments are presented in favour of an interpretation of asymmetric nuclear fission as a two-step process. In the\\u000a first step, a light cluster is formed within the nucleus from the valence nucleons of the fissioning nucleus. In the second\\u000a step, the whole subshell of the208Pb core, or the major part of this subshell, is transferred to free valence states

G. Mouze; C. Ythier

1990-01-01

242

State Dependent ?-PAIRING and Spontaneous Fission  

NASA Astrophysics Data System (ADS)

We examine the fission barriers, mass parameters and spontaneous fission half lives of Fermium isotopes within the framework of the macroscopic-microscopic model with a ?-pairing interaction. Four different macroscopic models are applied and studied. The results are compared to experimental data and to the ones of the corresponding monopole pairing approach. The half lives obtained in the ?-pairing model are comparable with experimental data.

Baran, A.; ?ojewski, Z.; Sieja, K.

243

Fission fragment registration in synthetic quartz  

Microsoft Academic Search

Synthetic quartz crystals were irradiated with Cf-fission fragments to study track registration properties in the x-plane. It was found that the properties depend on the sense of the x-plane: the etched-track size is larger and the effective critical angle ?? is higher on the + xx-plane than on the - x-plane and as a result the registration efficiency for fission

Teruko Sawamura; Hastuo Yamazaki

1990-01-01

244

FISSION OF URANIUM238 WITH CARBON IONS  

Microsoft Academic Search

Angular distributions and kinetic-energy spectra of fragments, and cross ; sections for fission of U²³⁸ with 63- to 124-Mev C¹² ions, were ; measured with the use of a silicon p-n junction detector. The distributions were ; analyzed in terms of the formation of a compound nucleus and subsequent decay by ; evaporation of neutrons in competition with fission. The

T. Sikkeland; A. E. Larsh; G. E. Gordon

1961-01-01

245

Our 50-year odyssey with fission: Summary  

SciTech Connect

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 dumbell-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. 87 refs., 12 figs.

Nix, J.R.

1989-01-01

246

Formation and transport of fission product aerosols  

SciTech Connect

The calculation of fission product retention is the primary system of light water reactors requires the knowledge of the size distribution of the particles formed from the condensation of the volatile fission product vapors released in LWR accidents. To this end, a computer model RAFT (Reactor Aerosol Formation and Transport) is being developed to predict the size distribution and composition of the condensed cesium, iodine and tellurium containing aerosols.

Im, K.H.; Ahluwalia, R.K.

1983-01-01

247

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

248

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

249

Transport properties of fission product vapors  

SciTech Connect

Kinetic theory of gases is used to calculate the transport properties of fission product vapors in a steam and hydrogen environment. Provided in tabular form is diffusivity of steam and hydrogen, viscosity and thermal conductivity of the gaseous mixture, and diffusivity of cesium iodide, cesium hydroxide, diatomic tellurium and tellurium dioxide. These transport properties are required in determining the thermal-hydraulics of and fission product transport in light water reactors.

Im, K.H.; Ahluwalia, R.K.

1983-07-01

250

ORNL fission product release tests VI6  

Microsoft Academic Search

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 this series (VI-1, VI-2, and VI-3), which had been conducted in steam, the oxidized Zircaloy cladding remained largely intact and acted

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

1991-01-01

251

Theoretical descriptions of neutron emission in fission  

SciTech Connect

Brief descriptions are given of the observables in neutron emission in fission together with early theoretical representations of two of these observables, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity {bar {nu}}{sub p}. This is followed by summaries, together with examples, of modern approaches to the calculation of these two quantities. Here, emphasis is placed upon the predictability and accuracy of the new approaches. In particular, the dependencies of N(E) and {bar {nu}}{sub p} upon the fissioning nucleus and its excitation energy are discussed. Then, recent work in multiple-chance fission and other recent work involving new measurements are presented and discussed. Following this, some properties of fission fragments are mentioned that must be better known and better understood in order to calculate N(E) and {bar {nu}}{sub p} with higher accuracy than is currently possible. In conclusion, some measurements are recommended for the purpose of benchmarking simultaneous calculations of neutron emission and gamma emission in fission. 32 refs., 26 figs.

Madland, D.G.

1990-01-01

252

Spontaneous fission of the heaviest elements  

SciTech Connect

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

Hoffman, D.C.

1989-04-01

253

Atypical mitochondrial fission upon bacterial infection  

PubMed Central

We recently showed that infection by Listeria monocytogenes causes mitochondrial network fragmentation through the secreted pore-forming toxin listeriolysin O (LLO). Here, we examine factors involved in canonical fusion and fission. Strikingly, LLO-induced mitochondrial fragmentation does not require the traditional fission machinery, as Drp1 oligomers are absent from fragmented mitochondria following Listeria infection or LLO treatment, as the dynamin-like protein 1 (Drp1) receptor Mff is rapidly degraded, and as fragmentation proceeds efficiently in cells with impaired Drp1 function. LLO does not cause processing of the fusion protein optic atrophy protein 1 (Opa1), despite inducing a decrease in the mitochondrial membrane potential, suggesting a unique Drp1- and Opa1-independent fission mechanism distinct from that triggered by uncouplers or the apoptosis inducer staurosporine. We show that the ER marks LLO-induced mitochondrial fragmentation sites even in the absence of functional Drp1, demonstrating that the ER activity in regulating mitochondrial fission can be induced by exogenous agents and that the ER appears to regulate fission by a mechanism independent of the canonical mitochondrial fission machinery.

Stavru, Fabrizia; Palmer, Amy E.; Wang, Chunxin; Youle, Richard J.; Cossart, Pascale

2013-01-01

254

Spontaneous fission properties of 259103Lr  

NASA Astrophysics Data System (ADS)

We have measured the mass and kinetic-energy distributions of fragments from the spontaneous fission of 259Lr. The 259Lr was produced via the 248Cm (15N,4n) reaction with a production cross section of 100 nb using 81-MeV projectiles. The kinetic energies and times of the alpha particles and coincident fission fragments were measured using our rotating wheel system. From these data the half-life, mass, and kinetic-energy distributions were derived. The total kinetic-energy (TKE) distribution appears to consist of a single component with a most probable pre-neutron-emission TKE of 215+/-3 MeV. The mass distribution is predominantly symmetric with a full width at half maximum of about 20 mass numbers. These results are consistent with trends observed for other trans-berkelium spontaneously fissioning isotopes. We determined the half-life to be 6.14+/-0.36 s by measuring its alpha decay and the observed spontaneous fission half-life was consistent with that value. An energy of 8.439+/-0.010 MeV was measured for the main alpha transition of 259Lr. We measured a spontaneous fission to alpha-decay ratio of 0.25+/-0.03 which results in a partial half-life for spontaneous fission of 31+/-4 s, if there are no other appreciable modes of decay.

Hamilton, T. M.; Gregorich, K. E.; Lee, D. M.; Czerwinski, K. R.; Hannink, N. J.; Kacher, C. D.; Kadkhodayan, B.; Kreek, S. A.; Nurmia, M. J.; Lane, M. R.; Neu, M. P.; Türler, A.; Hoffman, D. C.

1992-11-01

255

Fission cross section measurements at LANSCE  

NASA Astrophysics Data System (ADS)

Neutron induced fission cross sections of actinides are measured at the Los Alamos Neutron Science Center (LANSCE) in support of the Advanced Fuel Cycle Initiative (AFCI) and the National Nuclear Security Administration (NNSA). Nuclear technologies are increasingly dependent on advanced simulations for design and licensing requirements, and nuclear cross section data are important input parameters for the simulation tools. Fast nuclear reactor and stockpile stewardship applications often share nuclear data needs and requirements, and the LANSCE neutron source is ideal for measuring many of these data. The fission cross section measurements are guided by sensitivity studies performed in support of the AFCI program, as well as requests from NNSA. Recent results for the Pu-239 and Pu-241 fission cross sections from 0.01 eV to 200 MeV will be presented, and the discrepancy with current evaluations of the Pu-241 fission cross section discussed. Ongoing activities to extend the fission program will be presented, such as the development of a Time Projection Chamber (TPC) to significantly improve the experimental accuracies in fission cross section measurements.

Tovesson, Fredrik; Hill, Tony

2009-10-01

256

Polarization-encoded all-optical quaternary universal inverter and design of multivalued flip-flop  

NASA Astrophysics Data System (ADS)

Quaternary inverters are the fundamental building blocks of multivalued flip-flops (MVFFs). A novel all-optical quaternary universal inverter circuit with the help of a semiconductor optical amplifier-assisted Sagnac switch is proposed and described. This circuit exploits the polarization properties of light. Different logical states are represented by different polarization states of light. A terahertz optical asymmetric multiplexer-based gate plays an important role here. Numerical simulation results confirming the described method are given. An all-optical circuit for a MVFF (quaternary) with the help of our proposed quaternary universal inverter is also designed, and simulation results are presented.

Chattopadhyay, Tanay; Roy, Jitendra Nath

2010-03-01

257

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

258

The effect of the angular momentum dependence of the fission probability on the determination of fission time scales from fission excitation functions  

NASA Astrophysics Data System (ADS)

The effect of the strong angular momentum dependence of the fission probability is shown to prevent a direct determination of the pre-saddle fission delay time from fission excitation functions. Neglect of this effect in the analysis of excitation functions causes an apparent drop in fission probability with excitation energy, which can be misinterpreted as evidence for a pre-saddle delay time. Permanent address: Department of Physics, Smith College, Northampton, MA 01063, USA.

Hinde, D. J.; Leigh, J. R.; Lestone, J. P.; Newton, J. O.; Elfström, S.; Wei, J. X.; Zielinska-Pfabé, M.

1991-04-01

259

Fission and Quasi-Fission of Nuclei Produced in the Reactions with 48CA Ions  

Microsoft Academic Search

The work presents the results of the study of characteristics of the fission and quasi-fission of heavy nuclei, produced in the reactions with 48Ca ions at energies close to and below the Coulomb barrier. These experiments have been performed at the U-400 accelerator of the Flerov Laboratory of Nuclear Reactions (JINR) and XTU tandem accelerator in Legnaro (Italy) with the

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

2003-01-01

260

A new design of fission detector for prompt fission neutron investigation  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

261

Options for development of space fission propulsion systems  

NASA Astrophysics Data System (ADS)

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

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

2001-02-01

262

An aminostratigraphy for the British Quaternary based on Bithynia opercula.  

PubMed

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

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

2013-02-01

263

AMS measurements of fission products at CIAE  

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

264

Theory of neutron emission in fission  

SciTech Connect

A survey of theoretical representations of two of the observables in neutron emission in fission is given, namely, the prompt fission neutron spectrum N(E) and the average prompt neutron multiplicity {bar {nu}}{sub p}. Early representations of the two observables are presented and their deficiencies are discussed. This is followed by summaries and some examples of recent theoretical models for the calculation of these quantities. Emphasis is placed upon the predictability and accuracy of the recent models. In particular, the dependencies of N(E) and {bar {nu}}{sub p} upon the fissioning nucleus and its excitation energy are treated in detail for the Los Alamos model. Recent work in the calculation of the prompt fission neutron spectrum matrix N(E, E{sub n}), where E{sub n} is the energy of the neutron inducing fission, is then discussed. Concluding remarks address the current status of the ability to calculate these observables with confidence, the direction of future theoretical efforts, and limitations to current (and future) approaches. This paper is an extension of a similar paper presented at the International Centre for Theoretical Physics in 1996.

Madland, D.G.

1998-08-01

265

Correlation of recent fission product release data  

SciTech Connect

For the calculation of source terms associated with severe accidents, it is necessary to model the release of fission products from fuel as it heats and melts. Perhaps the most definitive model for fission product release is that of the FASTGRASS computer code developed at Argonne National Laboratory. There is persuasive evidence that these processes, as well as additional chemical and gas phase mass transport processes, are important in the release of fission products from fuel. Nevertheless, it has been found convenient to have simplified fission product release correlations that may not be as definitive as models like FASTGRASS but which attempt in some simple way to capture the essence of the mechanisms. One of the most widely used such correlation is called CORSOR-M which is the present fission product/aerosol release model used in the NRC Source Term Code Package. CORSOR has been criticized as having too much uncertainty in the calculated releases and as not accurately reproducing some experimental data. It is currently believed that these discrepancies between CORSOR and the more recent data have resulted because of the better time resolution of the more recent data compared to the data base that went into the CORSOR correlation. This document discusses a simple correlational model for use in connection with NUREG risk uncertainty exercises. 8 refs., 4 figs., 1 tab.

Kress, T.S.; Lorenz, R.A.; Nakamura, T.; Osborne, M.F.

1989-01-01

266

Average neutronic properties of prompt fission products  

SciTech Connect

Calculations of the average neutronic properties of the ensemble of fission products producted by fast-neutron fission of /sup 235/U and /sup 239/Pu, where the properties are determined before the first beta decay of any of the fragments, are described. For each case we approximate the ensemble by a weighted average over 10 selected nuclides, whose properties we calculate using nuclear-model parameters deduced from the systematic properties of other isotopes of the same elements as the fission fragments. The calculations were performed primarily with the COMNUC and GNASH statistical-model codes. The results, available in ENDF/B format, include cross sections, angular distributions of neutrons, and spectra of neutrons and photons, for incident-neutron energies between 10/sup -5/ eV and 20 MeV. Over most of this energy range, we find that the capture cross section of /sup 239/Pu fission fragments is systematically a factor of two to five greater than for /sup 235/U fission fragments.

Foster, D.G. Jr.; Arthur, E.D.

1982-02-01

267

Electrochemically stable fluorohydrogenate ionic liquids based on quaternary phosphonium cations  

Microsoft Academic Search

Fluorohydrogenate ionic liquids of quaternary phosphonium cations, tri-n-butylmethylphosphonium (P4441) fluorohydrogenate, tetra-n-butylphosphonium (P4444) fluorohydrogenate, and tri-n-butyl-n-octylphosphonium (P4448) fluorohydrogenate, have been synthesized by the metatheses of anhydrous hydrogen fluoride and the corresponding phosphonium chloride precursors. All the obtained salts have melting points below room-temperature with a vacuum-stable composition of P444m(FH)2.3F (m=1, 4, and 8) and were characterized by density, conductivity, and viscosity

Shunsuke Kanematsu; Kazuhiko Matsumoto; Rika Hagiwara

2009-01-01

268

Quaternary Faults and Folds by State and Region  

NSDL National Science Digital Library

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

269

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.

270

Thermal properties of quaternary ammonium and pyridinium compounds  

SciTech Connect

In the present work an attempt was made at a comprehensive investigation of the influence of the chemical structure of a whole series of cation-active surfactants on the stability to temperature influences, and the general directions of the irreversible transformations at high temperature were established. As a result of a study of processes of thermal decomposition of quaternary ammonium and syridinium salts, quantitative correlations were established according to the influence of the chemical structure of the salts on the limits of thermal stability. On the basis of a detailed analysis of volatile pyrolysis products, concrete schemes of the conversions in the objects studied were proposed.

Aksenova, V.P.; Khar'kov, S.N.; Logovotovskaya, V.D.; Belotserkovets, N.I.; Chegolya, A.S.

1982-12-10

271

Cytotoxic quaternary alkaloids from the flowers of Narcissus tazetta.  

PubMed

Intensive chromatographic separation of the polar fraction of an ethanolic extract of the fresh flowers of Narcissus tazetta L. (Amaryllidaceae) yielded two new quaternary alkaloids with a phenanthrene skeleton, N-methyl-8,9-methylenedioxy-phenantridinium methylsulfate (1) and N-methyl-8,9-methylenedioxy-phenantridinium malate (2). The structure determination of the alkaloids was based on one- and two-dimensional NMR studies including HMQC, and HMBC studies, and mass spectroscopic analysis. The existence, in 1, of the methylsulfate group was confirmed by X-ray diffraction analysis. Cytotoxic activities for 1 and 2 against a panel of cancer cell lines are also reported. PMID:11683132

Youssef, D T; Khalifa, A A

2001-10-01

272

Two new quaternary protoberberine alkaloids from Corydalis yanhusuo.  

PubMed

Two new quaternary protoberberine alkaloids, namely corydayanine (1) and yanhusuine (2), were isolated from the tubers of Corydalis yanhusuo. On the basis of extensive chemical and spectroscopic evidences, especially 1D and 2D NMR and HRMS experiments, their structures were elucidated as 5,6-dihydro-3,9-dihydroxy-2,10-dimethoxy-13-methyl-dibenzo[a,g] quinolizinium alkaloid and 5,6-dihydro-12-hydroxy-2,3,9-trimethoxy-13-methyl-dibenzo[a,g] quinolizinium alkaloid, respectively. PMID:22530675

Zhou, Qiong; Deng, An-Jun; Qin, Hai-Lin

2012-01-01

273

Spatial Response of Mammals to Late Quaternary Environmental Fluctuations  

PubMed

Analyses of fossil mammal faunas from 2945 localities in the United States demonstrate that the geographic ranges of individual species shifted at different times, in different directions, and at different rates in response to late Quaternary environmental fluctuations. The geographic pattern of faunal provinces was similar for the late Pleistocene and late Holocene, but differing environmental gradients resulted in dissimilar species composition for these biogeographic regions. Modern community patterns emerged only in the last few thousand years, and many late Pleistocene communities do not have modern analogs. Faunal heterogeneity was greater in the late Pleistocene. PMID:8662471

Graham; Lundelius; Graham; Schroeder; Toomey; Anderson; Barnosky; Burns; Churcher; Grayson; Guthrie; Harington; Jefferson; Martin; McDonald; Morlan; Semken; Webb; Werdelin; Wilson

1996-06-14

274

Event-by-Event Fission Modeling of Prompt Neutrons and Photons from Neutron-Induced and Spontaneous Fission with FREYA  

NASA Astrophysics Data System (ADS)

The event-by-event fission Monte Carlo code FREYA (Fission Reaction Event Yield Algorithm) generates large samples of complete fission events. Using FREYA, it is possible to obtain the fission products as well as the prompt neutrons and photons emitted during the fission process, all with complete kinematic information. We can therefore extract any desired correlation observables. Concentrating on ^239Pu(n,f), ^240Pu(sf) and ^252Cf(sf), we compare our FREYA results with available data on prompt neutron and photon emission and present predictions for novel fission observables that could be measured with modern detectors.

Vogt, Ramona; Randrup, Jorgen

2013-04-01

275

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

276

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

277

Genetic structure of Podocarpus nubigena (Podocarpaceae) provides evidence of Quaternary and ancient historical events  

Microsoft Academic Search

Evolution of ancient lineages inhabiting austral latitudes of the southern Andes has taken place in response to historical processes occurring at distinct spatial and temporal scales. We tested the hypothesis that distribution patterns of genetic polymorphisms within Podocarpus nubigena Lindl. (Podocarpaceae) were shaped by contemporary events acting at local scales such as Quaternary glaciations as well as pre-Quaternary palaeogeographical features

M. P. Quiroga; A. C. Premoli

2010-01-01

278

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

279

Isotopic fission fragment distributions as a deep probe to fusion-fission dynamics  

NASA Astrophysics Data System (ADS)

During the fission process, the atomic nucleus deforms and elongates up to the two fragments inception and their final separation at the scission deformation. The evolution of the nucleus energy with deformation defines a potential energy landscape in the multidimensional deformation space. It is determined by the macroscopic properties of the nucleus, and is also strongly influenced by the single-particle structure of the nucleus, which modifies the macroscopic energy minima. The fission fragment distribution is a direct consequence of the deformation path the nucleus has encountered, and therefore is the most genuine experimental observation of the potential energy landscape of the deforming nucleus. Very asymmetric fusion-fission reactions at energy close to the Coulomb barrier, produce well-defined conditions of the compound nucleus formation, where processes such as quasi-fission, pre-equilibrium emission and incomplete fusion are negligible. In the same time, the excitation energy is sufficient to reduce significantly structural effects, and mostly the macroscopic part of the potential is responsible for the formation of the fission fragments. We use inverse kinematics combined with a spectrometer to select and identify the fission fragments produced in 238U+12C at a bombarding energy close to and well-above the Coulomb barrier. For the first time, the isotopic yields are measured over the complete atomic-number distribution, between Z=30 and Z=63. In the experimental set-up, it is also possible to identify transfer-induced reactions, which lead to low-energy fission

Farget, F.; Caamaño, M.; Delaune, O.; Tarasov, O. B.; Derkx, X.; Schmidt, K.-H.; Amthor, A. M.; Audouin, L.; Bacri, C.-O.; Barreau, G.; Bastin, B.; Bazin, D.; Blank, B.; Benlliure, J.; Cacéres, L.; Casarejos, E.; Chbihi, A.; Fernàndez-Dominguez, B.; Gaudefroy, L.; Golabek, C.; Grévy, S.; Jurado, B.; Kamalou, O.; Lemasson, A.; Lukyanov, S.; Mittig, W.; Morrissey, D. J.; Navin, A.; Pereira, J.; Perrot, L.; Rejmund, M.; Roger, T.; Saint-Laurent, M.-G.; Savajols, H.; Schmitt, C.; Sherill, B. M.; Stodel, C.; Taieb, J.; Thomas, J.-C.; Villari, A. C.

2013-03-01

280

Fission-product formation in the thermal-neutron-induced fission of odd Cm isotopes  

SciTech Connect

Thermal-neutron-induced fission of {sup 243}Cm was studied at the Lohengrin mass separator. The light-mass peak of the fission-yield curve was investigated, and yields of masses from A=72 to A=120 were obtained. Independent-product yields were determined for nuclear charges Z=28-37. The yield of masses in the superasymmetric region was found to be identical to other fission reactions studied at Lohengrin. The multimodal approach to fission and the macroscopic-microscopic method for the calculation of charge-distribution parameters in isobaric chains were used to analyze experimental results from the fission of {sup 243}Cm and {sup 245}Cm. A systematics on fission modes was derived from the analysis and extended to the {sup 247}Cm case. The weight of the {sup 132}Sn mode was found to decrease in {sup 243}Cm, relative to the {sup 245}Cm nucleus. A prediction of the {sup 78}Ni yield in the fission of Cm isotopes was made. The feasibility of the study of {sup 78}Ni at Lohengrin has been demonstrated.

Tsekhanovich, I.; Varapai, N.; Rubchenya, V.; Rochman, D.; Simpson, G.S.; Sokolov, V.; Fioni, G.; Al Mahamid, Ilham [Institut Laue-Langevin, 38042 Grenoble (France); Petersburg Nuclear Physics Institute, 188350 Gatchina (Russian Federation); Commissariat a l'Energie Atomique, Siege, 75752 Paris Cedex 15 (France); Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2004-10-01

281

Final excitation energy of fission fragments  

SciTech Connect

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

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

2011-06-15

282

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); Dorn, R.I. [Arizona State Univ., Tempe, AZ (United States); Ku, T.L. [Univ. of Southern California, Los Angeles, CA (United States)

1995-04-01

283

Optimally Moderated Nuclear Fission Reactor and Fuel Source Therefor.  

National Technical Information Service (NTIS)

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

A. B. Ougouag H. D. Gougar W. K. Terry

2004-01-01

284

Fission-barrier heights of neutron-deficient mercury nuclei  

NASA Astrophysics Data System (ADS)

The recently measured probabilities of the ?-delayed fission for 178,180Tl are used to deduce the fission-barrier heights of the daughter isotopes 178,180Hg, undergoing low-energy fission. Four alternative ?-decay strength functions and four variants of the statistical model of de-excitation of the daughter nucleus are used to determine the fission-barrier height for 180Hg. Depending on the choice of the model, the deduced fission-barrier heights appear to be between 10% and 40% smaller than theoretical estimates. This observation is verified also for fission-barrier heights extracted using the probability of ?-delayed fission of 178Tl. The spread in extracted fission-barrier heights results mainly from uncertainties in the magnitude of the pairing gap at the saddle configuration.

Veselský, M.; Andreyev, A. N.; Antalic, S.; Huyse, M.; Möller, P.; Nishio, K.; Sierk, A. J.; Van Duppen, P.; Venhart, M.

2012-08-01

285

Fission Rate Measurements in Fuel Plate Type Assembly Reactor Cores.  

National Technical Information Service (NTIS)

The methods, materials and equipment have been developed to allow extensive and precise measurement of fission rate distributions in water moderated, U-Al fuel plate assembly type reactor cores. Fission rate monitors are accurately positioned in the react...

J. W. Rogers

1988-01-01

286

New fission-neutron-spectrum representation for ENDF  

SciTech Connect

A new representation of the prompt fission neutron spectrum is proposed for use in the Evaluated Nuclear Data File (ENDF). The proposal is made because a new theory exists by which the spectrum can be accurately predicted as a function of the fissioning nucleus and its excitation energy. Thus, prompt fission neutron spectra can be calculated for cases where no measurements exist or where measurements are not possible. The mathematical formalism necessary for application of the new theory within ENDF is presented and discussed for neutron-induced fission and spontaneous fission. In the case of neutron-induced fission, expressions are given for the first-chance, second-chance, third-chance, and fourth-chance fission components of the spectrum together with that for the total spectrum. An ENDF format is proposed for the new fission spectrum representation, and an example of the use of the format is given.

Madland, D.G.

1982-04-01

287

Length of fission tracks and age of muscovite samples  

Microsoft Academic Search

It has been observed that the etchable length of fission tracks in muscovite depends very closely on geologic age determined by the fission tracks method. The consequences of this fact, and especially its influence on the age calculation, are discussed.

Giulio Bigazzi

1967-01-01

288

Energy Dependence of Plutonium Fission-Product Yields  

NASA Astrophysics Data System (ADS)

A method is developed for interpolating between and/or extrapolating from two pre-neutron-emission first-chance mass-asymmetric fission-product yield curves. Measured 240Pu spontaneous fission and thermal-neutron-induced fission of 239Pu fission-product yields (FPY) are extrapolated to give predictions for the energy dependence of the n + 239Pu FPY for incident neutron energies from 0 to 16 MeV. After the inclusion of corrections associated with mass-symmetric fission, prompt-neutron emission, and multi-chance fission, model calculated FPY are compared to data and the ENDF/B-VII.1 evaluation. The ability of the model to reproduce the energy dependence of the ENDF/B-VII.1 evaluation suggests that plutonium fission mass distributions are not locked in near the fission barrier region, but are instead determined by the temperature and nuclear potential-energy surface at larger deformation.

Lestone, J. P.

2011-12-01

289

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

290

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

291

Observe an animation of nuclear fission  

NSDL National Science Digital Library

Created for high school students, this animation illustrates the nuclear fission of a uranium atom. A short simulation accompanied by text demonstrates how the addition of one neutron to uranium-235 causes it to become the unstable atom uranium-236. The unstable nucleus of uranium-236 spontaneously splits into two lighter elements, releasing a substantial amount of energy along with three neutrons. These neutrons can then react with other uranium-235 atoms to create a chain reaction of fission. Students are able to use control buttons to play, pause, and move forward and backward through the simulation. Copyright 2005 Eisenhower National Clearinghouse

Education, Terc. C.; Littell, Mcdougal

2003-01-01

292

Italian hybrid and fission reactors scenario analysis  

NASA Astrophysics Data System (ADS)

Italy is a country where a long tradition of studies both in the fission and fusion field is consolidated; nevertheless a strong public opinion concerned with the destination of the Spent Nuclear Fuel hinders the development of nuclear power. The possibility to a severe reduction of the NSF mass generated from a fleet of nuclear reactors employing an hypothetical fusionfission hybrid reactor has been investigated in the Italian framework. The possibility to produce nuclear fuel for the fission nuclear reactors with the hybrid reactor was analyzed too.

Ciotti, M.; Manzano, J.; Sepielli, M.

2012-06-01

293

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

294

Uncertainty Quantification on Prompt Fission Neutrons Spectra  

NASA Astrophysics Data System (ADS)

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 235U from thermal up to 15 MeV incident energies.

Talou, P.; Madland, D. G.; Kawano, T.

2008-12-01

295

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

296

European quaternary refugia: a factor in large carnivore extinction?  

NASA Astrophysics Data System (ADS)

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 highlighted the potential importance of glacial refugia in the extinction process. Even model refugia the size of the Italian peninsula did not guarantee persistence of a population over a 1000 yr time span, illustrating the role of chance in survival in such a refugium. An area the size of the largest Mediterranean island was unable to support a big cat population for a period of 1000 yr. The models also demonstrated the importance of inbreeding as a mechanism for extinction in refugia. It is suggested that repeated genetic bottlenecks during successive glaciations would tend to remove lethal recessive alleles from the population, increasing the probability of survival in refugia in subsequent glaciations. The history of extinction of large carnivores in the European Quaternary is interpreted in the light of these results.

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

2002-12-01

297

Uplift of quaternary shorelines in eastern Patagonia: Darwin revisited  

NASA Astrophysics Data System (ADS)

During his journey on the Beagle, Darwin observed the uniformity in the elevation of coastal Eastern Patagonia along more than 2000 km. More than one century later, the sequences of Quaternary shorelines of eastern Patagonia have been described and their deposits dated but not yet interpreted in terms of geodynamics. Consequently, we i) mapped the repartition of the Quaternary coastal sequences in Argentinean Patagonia, ii) secured accurate altitudes of shoreline angles associated with erosional morphologies (i.e. marine terraces and notches), iii) took into account previous chrono-stratigraphical interpretations in order to calculate mean uplift rates since ~ 440 ka (MIS 11) and proposed age ranges for the higher and older features (up to ~ 180 m), and iv) focused on the Last Interglacial Maximum terrace (MIS 5e) as the best constrained marine terrace (in terms of age and altitude) in order to use it as a tectonic benchmark to quantify uplift rates along the entire passive margin of Eastern South America. Our results show that the eastern Patagonia uplift is constant through time and twice the uplift of the rest of the South American margin. We suggest that the enhanced uplift along the eastern Patagonian coast that interested Darwin during his journey around South America on the Beagle could originate from the subduction of the Chile ridge and the associated dynamic uplift.

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

2011-04-01

298

Liquefaction potential of Quaternary alluvium in Bolu settlement area, Turkey  

NASA Astrophysics Data System (ADS)

Groundwater bearing alluvial units in the seismically active settlement areas may bring out probable damage on the urban and built environment due to liquefaction. Bolu settlement area and surroundings are located in the North Anatolian Fault Zone. Geotechnical boreholes were drilled in order to determine the distribution of the geological units, to obtain representative soil samples and to measure groundwater level. Quaternary aged alluvium is the main geological unit in the South of study area. Stiffness and consistency of the soils were determined by Standart penetration test. P and S wave velocities of soil have been measured along the seismic profiles. The index and physical properties of the samples have also been tested in the laboratory. Liquefaction potential and safety factor of the sandy levels in Quaternary aged alluvium were investigated by different methods based on SPT and V s. Liquefaction seems to be a significant risk in case of an earthquake with a max = 0.48 g and M w = 7.5 at different levels of the boreholes. This situation may bring out environmental problems in the future.

Ulamis, Koray; Kilic, Recep

2008-09-01

299

Asynchronous glaciation in Eastern Siberia during the Late Quaternary  

NASA Astrophysics Data System (ADS)

The extent and timing of former glaciation in Eastern Siberia has been reconstructed through the systematic mapping of end moraines, and the integration of published age-estimates. Reconstructions reveal that during the global Last Glacial Maximum (gLGM), glaciers extended no more than 50 km beyond mountain centres. During earlier, pre-gLGM, phases, glaciers were more extensive, with lengths of over 260 km. Published age estimates, though few, reveal that the timing of former glaciation, and the maximum Quaternary extent, was asynchronous across the region, and out-of-phase with ice-extent maxima elsewhere in the Northern Hemisphere. This glacial history is partly explained through consideration of climatic-forcing (particularly moisture-availability, solar insolation and albedo), though topographic-controls upon the extent and dynamics of former glaciers are also considered. Ultimately, it is argued that, during periods of Late-Quaternary cooling, the extent of glaciers in Eastern Siberia was governed by moisture availability, which was, in turn, largely governed by the extent of ice sheets elsewhere in the Northern Hemisphere.

Barr, Iestyn

2013-04-01

300

Global warming: Perspectives from the Late Quaternary paleomammal record  

SciTech Connect

Global warming at the end of the Pleistocene caused significant environmental changes that directly and indirectly effected biotic communities. The biotic response to this global warming event can provide insights into the processes that might be anticipated for future climatic changes. The megafauna extinction may have been the most dramatic alteration of mammalian communities at the end of the Pleistocene. Late Quaternary warming also altered regional diversity patterns for some small mammal guilds without extinction. Reductions in body size for both small and large mammal species were also consequences of these environmental fluctuations. Geographic shifts in the distributions of individual mammal species resulted in changes in species composition of mammalian communities. The individualistic response of biota to environmental fluctuations define some boundary conditions for modeling communities. Understanding these boundary conditions is mandatory in planning for the preservation of biodiversity in the future. Finally, it is essential to determine how global warming will alter seasonal patterns because it is apparent from the paleobiological record that not all Quaternary warming events have been the same.

Graham, R.W. (Illinois State Museum, Springfield, IL (United States))

1993-03-01

301

Morphological Change in Quaternary Mammals of North America  

NASA Astrophysics Data System (ADS)

This book examines case studies of North American Quaternary mammalian evolution within the larger domain of modern evolutionary theory. It presents previously unpublished studies of a variety of taxa (xenarthrans, rodents, carnivores, ungulates) examined over several temporal scales, from a few thousand years during the Holocene to millions of years of late Pliocene and Pleistocene time. Different organizational levels are represented, from mosaic population variation, to a synopsis of Quaternary evolution of an entire order (Rodentia). In addition to specific case histories, the book includes purely theoretical and methodological contributions, for example, on the statistical recognition of stasis in the fossil record, new ways to calculate evolutionary rates, and the use of digital image analysis in the study of dental ontogeny. Perhaps the most important aspect of the studies reported in this book is that they span the time between the "ecological moment" and "deep time". Modern taxa can be traced back into the fossil record, and variation among extant taxa can be used as a control against which variation in the extinct ones can be understood.

Martin, Robert A.; Barnosky, Anthony D.

1993-09-01

302

Quaternary seismo-tectonic activity of the Polochic Fault, Guatemala  

NASA Astrophysics Data System (ADS)

The Polochic-Motagua fault system is part of the sinistral transform boundary between the North American and Caribbean plates in Guatemala and the associated seismic activity poses a threat to ˜70% of the country's population. The aim of this study is to constrain the Late Quaternary activity of the Polochic fault by determining the active structure geometry and quantifying recent displacement rates as well as paleo-seismic events. Slip rates have been estimated from offsets of Quaternary volcanic markers and alluvial fan using in situ cosmogenic 36Cl exposure dating. Holocene left-lateral slip rate and Mid-Pleistocene vertical slip rate have been estimated to 4.8 ± 2.3 mm/y and 0.3 ± 0.06 mm/y, respectively, on the central part of the Polochic fault. The horizontal slip rate is within the range of longer-term geological slip rates and short-term GPS-based estimates. In addition, the non-negligible vertical motion participates in the uplift of the block north of the fault and seems to be a manifestation of the regional, far-field stress regime. We excavated the first trench for paleo-seismological study on the Polochic fault in which we distinguish four large paleo-seismic events since 17 ky during which the Polochic fault ruptured the ground surface.

Authemayou, Christine; Brocard, Gilles; Teyssier, Christian; Suski, Barbara; Cosenza, Beatriz; MoráN-Ical, Sergio; GonzáLez-VéLiz, Claussen Walther; Aguilar-Hengstenberg, Miguel Angel; Holliger, Klaus

2012-07-01

303

Ecostratigraphic datums and sequence stratigraphy: Application to the marine Quaternary  

SciTech Connect

The marine Quaternary is characterized by few evolutionary appearances and extinctions of planktonic foraminifera. Because climatic fluctuations are a fundamental characteristic of Pleistocene, however, better stratigraphic resolution of the marine Quaternary can be gained by the establishment of biozones based on climatically controlled foraminiferal assemblages. Utilizing relative abundances of the warm-water Globorotalia menardii complex and temperature-water G. inflata, supplemented by left- and right-coiling varieties of G. truncatulinoides, the authors have subdivided the prezone-W Pleistocene of the tropical Atlantic (Core V16-205), Caribbean Sea (DSDP Core 502B), and northeast Gulf of Mexico (ODP Core 625B, Eureka Core E67-135) into 17 subzones, each with an average duration of {approximately}100,000 yrs. The subzones appear to reflect water mass shifts and disjunct species distributions resulting from expansion and contraction of northern hemisphere ice sheets. Hence, subzonal boundaries should also reflect change in eustatic sea level and sequence boundaries. Indeed, graphic correlation of the subzones, along with biostratigraphic markers and paleomagnetic and oxygen isotope datums, reveals changes in sediment accumulation rate (especially on the continental slope) and missing section, as well as intervals of deformation (core breaks) that affect the occurrence of subzonal boundaries and biostratigraphic markers.

Martin, R.E. (Univ. of Delaware, Neward (United States)); Neff, E. (Univ. of Rhode Island, Narragansett (United States)); Johnson, G.W. (Hart Environmental Management, Pennsauken, NJ (United States)); Krantz, D. (Univ. of Delaware, Lewes (United States))

1991-03-01

304

Optimally moderated nuclear fission reactor and fuel source therefor  

DOEpatents

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

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

2008-07-22

305

Influence of fission spectra uncertainties on calculated fast reactor parameters  

Microsoft Academic Search

The effect of fission spectra uncertainties on calculated fast reactor parameters is studied by (1) considering the sensitivities to fission spectrum parameters of four performance parameters in the fast reactor benchmark ZPR-6\\/7, (2) estimating the uncertainties in these calculated performance parameters due to uncertainties in the fission spectra, (3) reporting the change in ZPR-6\\/7 calculated performance parameters due to fission

J. L. Lucius; J. H. Marable

1979-01-01

306

Group Fission in Barbary Macaques ( Macaca sylvanus ) at Affenberg Salem  

Microsoft Academic Search

We analyzed eight group fissions occurring during a 20-year period in three groups of a free-ranging provisioned Barbary macaque population. The founder group fissioned four times within 3.5 years after transfer to the enclosure, indicating that external factors—new environment, more space, absence of other groups—facilitated group fissions. Two groups resulting from these fissions, split twice within 2.5 and 1 years,

J. Kuester; A. Paul

1997-01-01

307

Some predictions of the cluster model of nuclear fission  

Microsoft Academic Search

The unified viewpoint provided by the cluster model of nuclear fission ; is used to predict mass distributions using the observed minima in the excitation ; energies of fragmerts and to calculate angular distributions from the mass yield ; curves. The mass distribution in thermal neutron induced fission of U²³⁵ ; is calculated, using certain assumptions for asymmetric fission, and

H. Faissner; K. Wildermuth

1962-01-01

308

Multiparameter studies of polar emission in 236U fission  

Microsoft Academic Search

The energy distributions and relative intensities of protons, deutrons, tritons and alpha-particles emitted along the fission axis during thermal neutron fission of 235U were measured simultaneously with both fission fragment energies. The mass distributions of fragments, the total kinetic energy (TKE), the dependence of the mean TKE on the fragment mass, as well as the mean kinetic energy dependence of

E. Piasecki; M. Sowinski; L. Nowicki; A. Kordyasz; E. Cieslak; W. Czarnacki

1975-01-01

309

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

310

Half-life for spontaneous fission of /sup 243/Cm  

SciTech Connect

A method is proposed for measuring the half-life for spontaneous fission of curium 243. Isotope separation and purification techniques are described and the isotope ratio of the purified target is given. The efficiency of fission fragment detection for solid state mica detectors was measured with a curium 244 standard. Results for the rate of spontaneous fission are tabulated.

Polynov, V.N.; Druzhinin, A.A.; Korochkin, A.M.; Nikitin, E.A.; Bochkarev, V.A.; Vyachin, V.N.; Lapin, V.G.; Maksimov, M.Yu.

1987-10-01

311

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

312

Alpha-recoil track dating of Quaternary volcanics  

Microsoft Academic Search

Like fission-track dating, alpha-recoil track (ART) dating is based on the accumulation of nuclear particles that are released by natural radioactivity and produce etchable tracks in solids. ARTs are formed during the alpha-decay of uranium and thorium as well as of their daughter nuclei. When emitting an alpha-particle, the heavy remaining nucleus recoils 30–40 nm, leaving behind a trail of

K. Gögen; G. A. Wagner

2000-01-01

313

Fission and quasi-fission: insights into heavy element formation reactions  

SciTech Connect

Mass-angle distributions carry detailed information on the characteristics of quasi-fission, and thus of the dynamics of heavy element formation reactions. Recent experimental results are presented and discussed.

Hinde, D. J.; Rietz, R. du; Rafiei, R.; Dasgupta, M.; Diaz-Torres, A. [Department of Nuclear Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); Thomas, R. G. [Department of Nuclear Physics, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia); B.A.R.C., Mumbai (India)

2009-03-04

314

Uncertainties and Covariances of the Fission Cross Sections and the Fission Neutron Multiplicities for Actinides  

SciTech Connect

Experimental data on the fission cross sections and the fission-neutron multiplicities of actinides are analyzed on the basis of the unrecognized error-estimation method. Such an approach allows us to estimate reasonable systematic uncertainties of available data, which are underestimated by authors of most measurements as a rule. The corresponding uncertainties and covariances of evaluated data are obtained for the most important actinides in the 15-energy group representation. Differences between the present evaluations and the recent BOLNA results are discussed for the main actinides. It is shown that the fission cross section uncertainties are overestimated essentially in the BOLNA analysis for minor actinides. Uncertainties of the cross sections and the neutron multiplicities averaged over the Cf-252 fission-neutron spectrum are considered.

Gai, E.V. [Institute of Physics and Power Engineering, 239033 Obninsk (Russian Federation); Ignatyuk, A.V. [Institute of Physics and Power Engineering, 239033 Obninsk (Russian Federation)], E-mail: ignatyuk@ippe.ru

2008-12-15

315

The nuclear fission process as Brownian motion: modifying the Kramers fission rates  

NASA Astrophysics Data System (ADS)

In 1940 Kramers demonstrated theoretically the influence of dissipation on the rate of the thermal escape of a Brownian particle from metastable state. He pointed out the nuclear fission process as a possible application of his results. In his derivation only the canonical ensemble and harmonical shapes of the potential were considered. We generalize the Kramers results for the case of the microcanonical ensemble which is more relevant for the fission process and derive the corrections to the original Kramers formulas accounting for the anharmonic character of the collective potential near its quasistationary and barrier points. The finite "distance" between the barrier and scission points is accounted for as well. We perform quantitative study of the agreement between the generalized and corrected Kramers fission rates and the exact dynamical quasistationary rates in the case of typical fission potentials.

Gontchar, I. I.; Kuzyakin, R. A.; Pavlova, E. G.; Aktaev, N. E.

2012-09-01

316

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

NASA Astrophysics Data System (ADS)

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

Kozulin, E. M.; Äystö, J.; Bogachev, A. A.; Iamaletdinov, S.; Itkis, M. G.; Hanappe, F.; Dorvaux, O.; Khlebnikov, S. V.; Kliman, J.; Knyazheva, G. N.; Krupa, L.; Lyapin, V.; Mutterer, M.; Rubchenya, V. A.; Sillanpää, M. O.; Trzaska, W. H.; Vardaci, E.

2006-08-01

317

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

SciTech Connect

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

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

2006-08-14

318

Evaluation of Fission Product After-Heat.  

National Technical Information Service (NTIS)

Reported here is work for the period indicated under the subject contract. Specific tasks covered in this report are: (1) Neutron capture in fission products, with the preliminary result that this effect does not lead to a major change in decay power of r...

B. I. Spinrad

1976-01-01

319

EQUILIBRIUM CHARGES OF FISSION FRAGMENTS IN GASES  

Microsoft Academic Search

A magnetic analysis method was used to measure the equilibrium charges ; of median-mass light and heavy fission fragments in S, He, air, and A, and mass-; 97 fragments in He for wide ranges of fragment velocity and gas pressure. The ; data for the fragments in H\\/, air, and A showed pressure effects on the ; equilibrium charge which

Clyde Fulmer; Bernard Cohen

1958-01-01

320

Velocity-Range Relation for Fission Fragments  

Microsoft Academic Search

Considerations indicated in an earlier note as regards the rate of velocity loss of fission fragments along the range are developed in greater detail and a comparison is given between the calculations and more recent experiments. Especially is a more precise estimate given for the charge effective in electronic encounters which are determining for the stopping effect over the first

N. Bohr

1941-01-01

321

Liquid uranium alloy-helium fission reactor  

Microsoft Academic Search

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

Minkov

1986-01-01

322

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

323

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

324

In the exit channel of nuclear fission  

Microsoft Academic Search

The final period of nuclear fission is discussed. We propose the following picture: Nuclear scission happens because of an hydrodynamic instability triggered by random surface vibrations. Thus the scissioning complex ruptures at random positions. Measured total kinetic energies point to the very relevance of the instability, while the randomness of rupture shows up in neutron emission data.

U. Brosa; S. Grossmann

1983-01-01

325

Asymptotically Correct Shell Model for Nuclear Fission  

Microsoft Academic Search

A two-center shell model with oscillator potentials, l-->.s--> forces, and l-->2 terms is developed. The shell structures of the original spherical nucleus and those of the final fragments are reproduced. For small separation of the two centers the level structure resembles the Nilsson scheme. This two-center shell model might be of importance in problems of nuclear fission.

D. Scharnweber; U. Mosel; W. Greiner

1970-01-01

326

Spontaneous fission of /sup 259/Fm  

SciTech Connect

A 1.5-s spontaneous fission activity has been produced by irradiating /sup 257/Fm with 16-MeV tritons. On the basis of formation cross sections, fission half-life systematics, and the identification of other possible products, this 1.5-s activity has been attributed to /sup 259/Fm formed by the reaction /sup 257/Fm(t,p)/sup 259/Fm. /sup 259/Fm is the heaviest known isotope of Fm and has more neutrons than any other nuclide thus far identified. This measurement of the spontaneous fission of /sup 259/Fm is the first to show a narrow, predominantly symmetric, mass division from spontaneous fission. It is accompanied by a very high kinetic energy, the most probable total kinetic energy being 242 +- 6 MeV. These features show a marked acceleration in the trend toward more symmetric mass division and higher total kinetic energies than have been observed previously for the Fm isotopes as the mass increased.

Hulet, E.K.; Lougheed, R.W.; Landrum, J.H.; Wild, J.F.; Hoffman, D.C.; Weber, J.; Wilhelmy, J.B.

1980-03-01

327

Mean Kinetic Energy of Nuclear Fission Fragments.  

National Technical Information Service (NTIS)

The experimental data on average kinetic energies of fragments at fixed nucleon composition and excitation energy of fissile intermediate nuclei from exp 141 Pr to exp 175 Lu and heavy nuclei from exp 182 W to exp 246 Cm are systematized. The fission reac...

V. G. Vorob'eva B. D. Kuz'minov V. N. Manokhin

1977-01-01

328

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)

1986-01-01

329

The Fission Vision: Teacher and Student Editions  

NSDL National Science Digital Library

Although they may have heard the term many times, students often have difficulty conceptualizing the process of nuclear fission. The kinesthetic simulation, as wellas the two suggested applets, are worthwhile activities for clarifying the process of nuclearfission. This free selection includes the Table of Contents, A Note from Joy Hakim, Resources for Integration and Implementation, the corresponding National Science Education Standards, and the Index.

Texley, Juliana

2008-11-01

330

Liquid uranium alloy-helium fission reactor  

DOEpatents

This invention describes a nuclear fission reactor which has 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 to 1800/sup 0/C range, and even higher to 2500/sup 0/C.

Minkov, V.

1984-06-13

331

Fission, fusion and the energy crisis  

Microsoft Academic Search

A relatively non-technical survey of nuclear fission and nuclear fusion power sources, this book is intended for the undergraduate student. It begins with an analogy of our present level of energy consumption with the practice of living on accumulated capital reserves in which uranium and fossil fuel use represents capital depletion and renewable energy sources and fusion energy represent long-range

Hunt

1980-01-01

332

A CHEMICAL METHOD OF TREATING FISSIONABLE MATERIAL  

DOEpatents

One step of a process for separating plutonium from uranium and fission products is presented. A nitric acid solution containing these constituents is treated with formic acid to reduce simultaneously the plutonium to a valence state of not greater than +4 and destroy and eliminate the excess nitric acid.

Olson, C.M.

1959-09-01

333

TMI2 fission product inventory estimates (draft)  

Microsoft Academic Search

This report presents the results of analyses performed to estimate the inventory and distribution of selected radioisotopes within the TMI-2 reactor system. The intent of the report is to document the method used in estimating the fission product inventory and associated uncertainties. The values presented should be viewed as preliminary. Selected radioisotopes for which best-estimate inventories and uncertainties are presented

E. L. Tolman; M. Nishio

1987-01-01

334

Mitochondrial fission in apoptosis, neurodegeneration and aging  

Microsoft Academic Search

A decline in mitochondrial function is well recognized in neurodegenerative diseases and aging, and is thought to play a causal role in their biology. Unfortunately, the molecular basis underlying this detrimental loss in mitochondrial function remains mysterious. Interestingly, mitochondria undergo frequent fission and fusion. This process is regulated by molecular machinery that has been highly conserved during evolution, including dynamin-related

Ella Bossy-Wetzel; Mark J Barsoum; Adam Godzik; Robert Schwarzenbacher; Stuart A Lipton

2003-01-01

335

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

336

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

337

Cold fission as cluster decay with dissipation  

SciTech Connect

For cold (neutronless) fission we consider an analytical model of quantum tunneling with dissipation through a barrier {ital U}({ital q}) evaluated with a M3Y nucleon-nucleon force. We calculate the tunneling spectrum, i.e., the fission rate as a function of the total kinetic energy of the fragments. The theoretical results are compared with the experimental data obtained for the fine structure of two cold fission modes of {sup 252}Cf: {sup 148}Ba+{sup 104}Mo and {sup 146}Ba+{sup 106}Mo. Taking into account the dissipative coupling of the potential function {ital U}({ital q}) and of the momentum {ital p} with all the other neglected coordinates, we obtain a remarkable agreement with the experimental data. We conclude that the cold fission process is a spontaneous decay with a spectrum determined by the shape of the barrier and an amplitude depending on the strength of the dissipative coupling. {copyright} {ital 1996 The American Physical Society.}

Stefanescu, E.; Scheid, W. [Institut fuer Theoretische Physik der Justus-Liebig-Universitaet, Giessen (Germany); Sandulescu, A.; Greiner, W. [Institut fuer Theoretische Physik der Johann Wolfgang Goethe-Universitaet, Frankfurt am Main (Germany)

1996-06-01

338

AVR EXPERIMENTS RELATED TO FISSION PRODUCT TRANSPORT  

Microsoft Academic Search

Fission products deposited outside of the active core play a dominant role in source term estimations for advanced small pebble bed HTRs, particularly in design basis accidents (dba), despite of their relatively small fraction of < 3·10 -4 of the total inventory. This is, because the maximum tolerable releases in dba are < 10 -7 of the total inventory of

Rainer Moormann

2006-01-01

339

Nondestructive fission gas release measurement and analysis  

Microsoft Academic Search

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

P. M. OLeary; D. R. Packard

1993-01-01

340

Delayed neutrons in fission of polonium isotopes  

SciTech Connect

A strong difference is found in the relative yields of delayed neutrons in the production of compound nuclei of polonium isotopes in reactions in which bismuth and lead are bombarded by various charged particles. The effect can be partially explained by the different lengths of the ..beta..-decay chains of the light and heavy fission products.

Ramazanov, R.; Urikbaev, Z.S.; Maksyutenko, B.P.; Ignat'ev, S.V.

1988-06-01

341

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

342

Fission Fragment Distributions and Delayed Neutron Yields from Photon-Induced-Fission  

SciTech Connect

Fission fragment distributions and delayed neutron yields for 235U and 238U are provided by a complete modelization of the photofission process below 25 MeV. The absorption cross-section parameterization and the fission fragment distributions are given and compared to experimental data. The delayed neutron yields and the half-lives in terms of six groups are presented and compared to data obtained with a bremsstrahlung spectrum of 15 MeV.

David, J.-C.; Dore, D.; Giacri-Mauborgne, M.-L.; Ridikas, D.; Lauwe, A. van [DSM/DAPNIA/SPhN, CEA/Saclay, F-91191 Gif-sur-Yvette cedex (France)

2005-05-24

343

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

344

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

SciTech Connect

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

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

1985-05-01

345

Fission Product Yields from Fission Spectrum n+ 239Pu for ENDF\\/B-VII.1  

Microsoft Academic Search

We describe a new cumulated fission product yield (FPY) evaluation for fission spectrum neutrons on plutonium that updates the ENDF\\/B-VI evaluation by England and Rider, for the forthcoming ENDF\\/B-VII.1 database release.11We intend to release the ENDF\\/B-VII.1 database in December 2011, and all released data are subject to CSEWG approval. It is possible that the released evaluated data will differ from

M. B. Chadwick; T. Kawano; D. W. Barr; M. R. Mac Innes; A. C. Kahler; T. Graves; H. Selby; C. J. Burns; W. C. Inkret; A. L. Keksis; J. P. Lestone; A. J. Sierk; P. Talou

2010-01-01

346

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

347

Fission Fragment Deformation and Dynamical Effects in Spontaneous Fission of 252CF and 248CM  

NASA Astrophysics Data System (ADS)

The number of prompt neutrons emitted in the fission event have been measured separately for each complementary fragment in coincidence with fragment mass and kinetic energies in spontaneous fission of 252Cf and 248Cm. Two high efficient Gd-loaded liquid scintillator tanks were used for the neutron registration. Approximately 3-106 fission events coincident with prompt neutron emission have been accumulated for each isotope. Neutron multiplicity distributions corrected for efficiency, background and pile-up have been obtained as a function of fission fragment mass and kinetic energy. Based on these unfolded multiplicity distributions fragment mass distributions for specific numbers of emitted neutrons have been obtained. These mass spectra demonstrates the presence of cold compact and deformed fission and the strong influence of deformed neutron shells in fragments at the descent to scission. Possible explanations for deformed cold fission are given on the basis of an analysis of the behavior of the moments of the multiplicity distributions on the fragment total kinetic energy.

Kalinin, V. A.; Dushin, V. N.; Petrov, B. F.; Yakovlev, V. A.; Vorobyev, A. S.; Laptev, A. B.; Shcherbakov, O. A.; Hambsch, F.-J.

2003-10-01

348

Calculation of fission yield using fission barrier from optimal shapes of liquid drop model  

NASA Astrophysics Data System (ADS)

Fission barrier parameter that obtained from the liquid drop model framework does not involve any optimal shapes that based on minimization of liquid drop energy at fixed volume and elongation. In this work, fission yield of 238U and 232Th have been calculated using TALYS nuclear reaction code by implementing fission barrier height that obtained from minimization of liquid drop energy without using any shape parameterization. Fission yield model that has been employed in this calculation was derived from multi modes of random neck rupture model (MM-RNRM) proposed by Brosa et. al. This model is based on Lawrence shapes of deformed nuclei at scission mechanism and has been integrated in TALYS code. The calculation results were compared with the fission yield from ENDF at 0.5 MeV, 10 MeV, and 14 MeV in both cases. The discrepancy between calculation results and ENDF data are probably due to invalid fission parameter that included in the input file.

Perkasa, Yudha Satya; Waris, Abdul; Kurniadi, Rizal; Su'ud, Zaki

2012-06-01

349

Effect of fission dynamics on the spectra and multiplicities of prompt fission neutrons  

SciTech Connect

With the goal of examining their effect on the spectra and multiplicities of the prompt neutrons emitted in fission, we discuss recent advances in a unified macroscopic-microscopic description of large-amplitude collective nuclear dynamics. The conversion of collective energy into single-particle excitation energy is calculated for a new surface-plus-window dissipation mechanism. By solving the Hamilton equations of motion for initial conditions appropriate to fission, we obtain the average fission-fragment translational kinetic energy and excitation energy. The spectra and multiplicities of the emitted neutrons, which depend critically upon the average excitation energy, are then calculated on the basis of standard nuclear evaporation theory, taking into account the average motion of the fission fragments, the distribution of fission-fragment residual nuclear temperature, the energy dependence of the cross section for the inverse process of compound-nucleus formation, and the possibility of multiple-chance fission. Some illustrative comparisons of our calculations with experimental data are shown.

Nix, J.R.; Madland, D.G.; Sierk, A.J.

1985-01-01

350

Improved calculation of the prompt fission neutron spectrum from the spontaneous fission of /sup 252/Cf  

SciTech Connect

An improved calculation is presented for the prompt fission neutron spectrum N(E) from the spontaneous fission of /sup 252/Cf. In this calculation the fission-spectrum model of Madland and Nix is used, but with several improvements leading to a physically more accurate representation of the spectrum. Specifically, the contributions to N(E) from the entire fission-fragment mass and charge distributions will be calculated instead of calculating on the basis of a seven-point approximation to the peaks of these distributions as has been done in the past. Therefore, values of the energy release in fission, fission-fragment kinetic energy, nuclear level density, and compound nucleus cross section for the inverse process will be considered on a point-by-point basis over the fragment yield distributions instead of considering averages of these quantities over the peaks of the distributions. Particular attention will be given to the energy-dependent compound nucleus cross sections and to the nuclear level density model. Other refinements to the calculation of N(E) will also be discussed. Results will be presented and compared with earlier calculations of the spectrum and with recent experimental measurements of the spectrum. 9 figs.

Madland, D.G.

1988-01-01

351

Predicting the Fission Yeast Protein Interaction Network  

PubMed Central

A systems-level understanding of biological processes and information flow requires the mapping of cellular component interactions, among which protein–protein interactions are particularly important. Fission yeast (Schizosaccharomyces pombe) is a valuable model organism for which no systematic protein-interaction data are available. We exploited gene and protein properties, global genome regulation datasets, and conservation of interactions between budding and fission yeast to predict fission yeast protein interactions in silico. We have extensively tested our method in three ways: first, by predicting with 70–80% accuracy a selected high-confidence test set; second, by recapitulating interactions between members of the well-characterized SAGA co-activator complex; and third, by verifying predicted interactions of the Cbf11 transcription factor using mass spectrometry of TAP-purified protein complexes. Given the importance of the pathway in cell physiology and human disease, we explore the predicted sub-networks centered on the Tor1/2 kinases. Moreover, we predict the histidine kinases Mak1/2/3 to be vital hubs in the fission yeast stress response network, and we suggest interactors of argonaute 1, the principal component of the siRNA-mediated gene silencing pathway, lost in budding yeast but preserved in S. pombe. Of the new high-quality interactions that were discovered after we started this work, 73% were found in our predictions. Even though any predicted interactome is imperfect, the protein network presented here can provide a valuable basis to explore biological processes and to guide wet-lab experiments in fission yeast and beyond. Our predicted protein interactions are freely available through PInt, an online resource on our website (www.bahlerlab.info/PInt).

Pancaldi, Vera; Sarac, Omer S.; Rallis, Charalampos; McLean, Janel R.; Prevorovsky, Martin; Gould, Kathleen; Beyer, Andreas; Bahler, Jurg

2012-01-01

352

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

353

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

354

Transient effects in fission from new experimental signatures.  

PubMed

A new experimental approach is introduced to investigate the relaxation of the nuclear deformation degrees of freedom. Highly excited fissioning systems with compact shapes and low angular momenta are produced in peripheral relativistic heavy-ion collisions. Both fission fragments are identified in atomic number. Fission cross sections and fission-fragment element distributions are determined as a function of the fissioning element. From the comparison of these new observables with a nuclear-reaction code a value for the transient time is deduced. PMID:15324228

Jurado, B; Schmitt, C; Schmidt, K-H; Benlliure, J; Enqvist, T; Junghans, A R; Keli?, A; Rejmund, F

2004-08-12

355

The behavior of fission products during nuclear rocket reactor tests  

NASA Astrophysics Data System (ADS)

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

Bokor, Peter C.; Kirk, William L.; Bohl, Richard J.

1991-01-01

356

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

SciTech Connect

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

Hippo, E.J.; Murdie, N.

1986-05-01

357

Fast Neutron Induced Fission neutron Spectra Below the Incident Energy  

SciTech Connect

Fission neutron spectra from neutron induced fission in 235U and 239Pu for energies below that of the neutron inducing fission have been measured. The spectra were obtained for 1.5 MeV and 2.5 MeV incident neutrons. Previous accelerator-based fission neutron spectra measurements have been seriously complicated by time-correlated gamma rays and scattered neutrons from the fission sample. Three barium fluoride detectors were placed near the sample undergoing induced fission and used to identify fission gamma rays. A coincidence of fission gamma rays was used to gate a liquid scintillator neutron detector to distinguish fission events from other events. The fission neutron spectral shape and average energy measured in this experiment compare well to both previous measurements and prior theory and also suggest a dependence on incident neutron energy and mass of the fissioning nucleus. An overview of the experiment, a discussion of the results, and the importance of this work to homeland security are given.

Woodring, Mitchell L.; Egan, James J.; Kegel, Gunter H.; DeSimone, David J.

2008-06-15

358

Fifty years of nuclear fission: Nuclear data and measurements series  

SciTech Connect

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

Lynn, J.E.

1989-06-01

359

Recoil-fission tagging of the transfermium nucleus 252No  

NASA Astrophysics Data System (ADS)

An in-beam study of the transfermium nucleus 252No has been performed using the JUROSPHERE II array of germanium detectors coupled to the gas-filled recoil separator RITU. A new technique of recoil-fission tagging was used to extract tagged ?-ray data. Having significant spontaneous fission and ?-decay branches, 252No is an ideal candidate for a comparative study. In a similar manner to ?-decay tagging the fission events can be used to obtain ?-ray data. The recoil-fission tagged ?-ray spectrum showed a similar structure to the ?-decay tagged ?-ray spectrum. By comparing the ?-tagged and fission-tagged spectra and decay curves, it was shown that the spontaneous fission originates from the same initial state as the ? decay. This extension of the tagging method allows in-beam spectroscopic data to be obtained from heavy nuclei with significant spontaneous-fission branches.

Leppänen, A.-P.; Uusitalo, J.; Greenlees, P. T.; Herzberg, R.-D.; Amzal, N.; Becker, F.; Butler, P. A.; Chewter, A. J. C.; Cocks, J. F. C.; Dorvaux, O.; Eeckhaudt, S.; Eskola, K.; Gerl, J.; Grahn, T.; Hammond, N. J.; Hauschild, K.; Helariutta, K.; Heßberger, F. P.; Houry, M.; Jones, G. D.; Jones, P. M.; Julin, R.; Juutinen, S.; Kankaanpää, H.; Kettunen, H.; Khoo, T. L.; Korten, W.; Kuusiniemi, P.; Le Coz, Y.; Leino, M.; Lister, C. J.; Lucas, R.; Muikku, M.; Nieminen, P.; Nyman, M.; Page, R. D.; Pakarinen, J.; Rahkila, P.; Reiter, P.; Sarén, J.; Schlegel, Ch.; Scholey, C.; Stezowski, O.; Theisen, Ch.; Trzaska, W. H.; Wollersheim, H. J.

2006-06-01

360

Late Quaternary western Mediterranean pollen records and African winds  

NASA Astrophysics Data System (ADS)

Late Quaternary vegetation changes of regional and global significance in the Mediterranean region are generally interpreted as being controlled by changes in the circulation patterns of North Atlantic air masses. However, the possibility cannot be excluded that they may also be related to winds blowing from Africa. Long pollen records from southwest Europe show that Cedrus pollen of northwest African provenance is found during the glacial periods, and occasionally during abrupt deforestation events in the forest-dominated periods of the interglacials. A pollen concentration record from central Italy shows that during the Holocene the presence of Cedrus pollen coincides with two abrupt deforestation events, around 8.1 and 4.2 cal kyr BP. These observations raise the question of a possible influence of eolian activity on arboreal vegetation during phases of climatic stress towards aridity, and suggest the use of modern pollen monitoring as a strategy for revealing tendencies towards aridification in southwestern Europe.

Magri, D.; Parra, I.

2002-06-01

361

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

362

Quaternary eustatic sedimentary accretion of southern Bahamas Archipelago  

SciTech Connect

Surficial geologic mapping indicates that the southern half of the Bahamas Archipelago is forming by the accretion of discrete depositional sequences resulting from successive eustatic sea level changes: (1) multiple beach and dune ridges, (2) estuarine, (3) lacustrine, (4) shallow subtidal, (5) reef and reef rubble, and (6) megadune complexes. The lithologies are accreted along unconformable erosional-solutional contacts - marine terraces and subaerial caliche crusts. During periods of significant transgression, sequences 1-5 are accreted. Sediments are predominantly skeletal and peloid. During periods of significant regression, megadune complexes are accreted. Ooids are the dominant sediment. Erosional-solutional features reflect areas of subaerial exposure and/or coastline erosion. Terraces at 10, 20, and 40 ft elevations are preserved along arid eastern Great Inagua Island. The calichification of Bahamian Quaternary carbonates has concentrated insoluble residues (quartz, feldspar, heavy minerals, crandallite, micrometeorites). Insoluble residue analysis provides a basis for the correlation of accreted eustatic sedimentary sequences.

Mitchell, S.W.

1985-02-01

363

Site of Action of Certain Antibacterial Heterocyclic Quaternary Ammonium Compounds  

PubMed Central

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

Cox, W. A.

1965-01-01

364

Quaternary beetle research: the state of the art  

NASA Astrophysics Data System (ADS)

Quaternary beetle research has progressed in a variety of ways during the last decade. New kinds of data are being extracted from the fossil specimens themselves, such as ancient DNA and stable isotopes. The ancient DNA studies hold the promise of proving new insights on the stability of beetle genotypes. The study of stable isotopes of H and O from fossil beetle chitin holds the promise of providing an independent proxy for the reconstruction of temperature and precipitation. The discipline is also expanding into previously unstudied regions, such as Australia, New Zealand, and northern Asia. Along with the new study regions, new schools of thought are also forming in the discipline, challenging old research paradigms. This is a necessary step forward for the discipline, as it grows and develops in the 21st Century.

Elias, Scott A.

2006-08-01

365

Luminescence studies on nitride quaternary alloys double quantum wells  

NASA Astrophysics Data System (ADS)

We present theoretical photoluminescence (PL) spectra of undoped and p-doped Al xIn 1- x- yGa yN/Al XIn 1- X- YGa YN double quantum wells (DQWs). The calculations were performed within the k.p method by means of solving a full eight-band Kane Hamiltonian together with the Poisson equation in a plane wave representation, including exchange-correlation effects within the local density approximation. Strain effects due to the lattice mismatch are also taken into account. We show the calculated PL spectra, analyzing the blue and red-shifts in energy as one varies the spike and the well widths, as well as the acceptor doping concentration. We found a transition between a regime of isolated quantum wells and that of interacting DQWs. Since there are few studies of optical properties of quantum wells based on nitride quaternary alloys, the results reported here will provide guidelines for the interpretation of forthcoming experiments.

Rodrigues, S. C. P.; dos Santos, O. F. P.; Scolfaro, L. M. R.; Sipahi, G. M.; da Silva, E. F., Jr.

2008-09-01

366

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

367

Late Quaternary river drainage and fish evolution, Southland, New Zealand  

NASA Astrophysics Data System (ADS)

Late Quaternary to Holocene landscape evolution in southern New Zealand was dominated by glacial outwash processes. Evolution of the drainage network on a regional scale was punctuated by numerous river capture events associated with outwash transport and deposition. River capture events can be inferred from geological and topographic observations throughout the region. Independent evidence for river capture and drainage reorientation can be obtained from genetic studies of a freshwater-limited fish (Galaxias ‘southern’, informal name). Regionally extensive interlinking of principal rivers (Mataura, Oreti, Aparima) via coalescence of alluvial plains onshore, and offshore at sea level lowstands, has resulted in a widespread genetic homogenisation of fish populations (< 0.9% mtDNA divergence). Genetically similar populations of G. ‘southern’ are present in an adjacent catchment (Von) that was captured episodically by the neighbouring major river system (Clutha). The low degree of genetic divergence between Oreti and Von catchments (< 0.15% mtDNA divergence) demonstrates that genetic interaction between fish populations was severed recently, probably during the early Holocene. This is in accord with radiocarbon dating (11 13 ka) of the youngest gravel level within the intervening divide. In contrast, morphologically similar fish in another adjacent major river (Waiau) have a minimum mtDNA divergence of 2.4% from the fish in the Mataura, Oreti, and Aparima Rivers. This genetic separation occurred at ca. 145 240 ka, based on the late Quaternary outwash terrace dating, in agreement with “molecular clock” estimates. Geological and genetic data in combination provide powerful tools for the elucidation of local and regional geomorphic evolution where river capture is an important process. The potential is strong for genetic data alone to provide information on the relative and absolute timing of river capture events, but must be interpreted in the context of severance of water connections between catchments and subsequent isolation of freshwater-limited populations.

Craw, D.; Burridge, C.; Anderson, L.; Waters, J. M.

2007-02-01

368

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

369

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

NASA Astrophysics Data System (ADS)

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

Vorobyev, A. S.; Dushin, V. N.; Hambsch, F.-J.; Jakovlev, V. A.; Kalinin, V. A.; Laptev, A. B.; Petrov, B. F.; Shcherbakov, O. A.

2005-05-01

370

Fast neutron induced fission neutron spectra below the incident energy  

NASA Astrophysics Data System (ADS)

Fission neutron spectra from neutron induced fission in 235U and 239Pu for energies below that of the neutron inducing fission have been measured. The spectra were obtained for 1.5 MeV and 2.5 MeV incident neutrons. Previous accelerator-based fission neutron spectra measurements have been seriously complicated by time-correlated gamma-rays and scattered neutrons from the fission sample. This work provides a way to extract fission neutrons from other radiation species in a manner not previously attempted. Protons from the University of Massachusetts Lowell type CN 5.5 MV Van de Graaff accelerator were pulsed and then bunched by a Mobley compression bunching system to pulse time durations of approximately 500 ps. Monoenergetic neutron bursts produced by the 7Li(p,n)7Be reaction, were incident on samples of 235U and 239Pu inducing fission and producing fission neutrons. Three BaF2 detectors placed near the sample were used to identify fission gamma rays. The coincidence of two BaF2 detector anode signals was used to gate a liquid scintillation detector to distinguish fission events from other events in the detector. The fission neutron time-of-flight data was acquired by a new personal computer based multi-parameter data acquisition system called INVADAR. INVADAR allowed data to be taken in a multi-parameter event-mode format using a single analog-to-digital converter and an analog multiplexer. The fission neutron spectra shape and average energy measured here compare well to previous measurements and theory. The data support the theoretical suggestion that the fission neutron spectrum shape depends upon the incident neutron energy and mass of the fissioning nucleus.

Woodring, Mitchell Lee

1997-09-01

371

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

372

Microscopic Calculations of 240Pu Fission  

SciTech Connect

Hartree-Fock-Bogoliubov calculations have been performed with the Gogny finite-range effective interaction for {sup 240}Pu out to scission, using a new code developed at LLNL. A first set of calculations was performed with constrained quadrupole moment along the path of most probable fission, assuming axial symmetry but allowing for the spontaneous breaking of reflection symmetry of the nucleus. At a quadrupole moment of 345 b, the nucleus was found to spontaneously scission into two fragments. A second set of calculations, with all nuclear moments up to hexadecapole constrained, was performed to approach the scission configuration in a controlled manner. Calculated energies, moments, and representative plots of the total nuclear density are shown. The present calculations serve as a proof-of-principle, a blueprint, and starting-point solutions for a planned series of more comprehensive calculations to map out a large set of scission configurations, and the associated fission-fragment properties.

Younes, W; Gogny, D

2007-09-11

373

Anisotropic Neutron Evaporation from Spinning Fission Fragments  

NASA Astrophysics Data System (ADS)

Neutron evaporation anisotropy in the centre of mass of the rotating fission fragments in the spontaneous fission of 252Cf has been investigated within the CORA experiments. If it is well accepted that the bulk of emitted neutrons originate from an isotropic evaporation in the centre of mass of the moving fragments, discrepancies in experimental as well as in theoretical energy and angular distributions appear throughout many attempts performed by various authors. Scission neutrons most probably contribute but don't allow to explain totally the observed anisotropy. Due to its weak contribution to the total anisotropy, the centre of mass anisotropy is very difficult to be highlighted. A novel experimental approach has been developed to extract this effect and will be presented as well as some first results.

Stuttgé, L.; Dorvaux, O.; Gönnenwein, F.; Mutterer, M.; Kopatch, Yu.; Chernysheva, E.; Hanappe, F.; Hambsch, F.-J.

2011-10-01

374

Nuclear organisation and RNAi in fission yeast.  

PubMed

Over the last decade, the fission yeast Schizosaccharomyces pombe has been used extensively for investigating RNA interference (RNAi)-mediated heterochromatin assembly. However, only recently have studies begun to shed light on the 3D organisation of chromatin and the RNAi machinery in the fission yeast nucleus. These studies indicate association of repressive and active chromatin with different regions of the nuclear periphery, similar to other model organisms, and clustering of functionally related genomic features. Unexpectedly, RNAi factors were shown to associate with nuclear pores and were implicated in the regulation of genomic features outside of the well-studied heterochromatic regions. Nuclear organisation is likely to contribute to substrate specificity of the RNAi pathway. However, further studies are required to elucidate the exact mechanisms and functional importance of this nuclear organisation. PMID:23453865

Woolcock, Katrina J; Bühler, Marc

2013-02-28

375

Nuclear Fission Investigation with Twin Ionization Chamber  

NASA Astrophysics Data System (ADS)

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.; Nazarenko, M.; Hambsch, F.-J.; Oberstedt, S.

2011-11-01

376

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

377

Adjustment of the (235)U Fission Spectrum  

SciTech Connect

The latest nuclear data are used to examine the sensitivity of the least squares adjustment of the {sup 235}U fission spectrum to the measured reaction rates, dosimetry cross sections, and prior spectrum covariance matrix. All of these parameters were found to be very important in the spectrum adjustment. The most significant deficiency in the nuclear data is the absence of a good prior covariance matrix. Covariance matrices generated from analytic models of the fission spectra have been used in the past. This analysis reveals some unusual features in the covariance matrix produced with this approach. Specific needs are identified for improved nuclear data to better determine the {sup 235}U spectrum. An improved {sup 235}U covariance matrix and adjusted spectrum are recommended for use in radiation transport sensitivity analyses.

GRIFFIN,PATRICK J.; WILLIAMS,J.G.

1999-09-14

378

New Nubar Results for Fissionable Materials  

NASA Astrophysics Data System (ADS)

A crucial feature of reactor operation and control is the emission of ?-delayed neutrons from the fuel. For example, uncertainties in the number of delayed neutrons can lead to excessive margins for safety in the operation of fission reactors. The relevant measurable quantity is the beta-delayed neutron emission probability (Pn), which is the probability that the beta-decay proceeds to states above the neutron separation energy and a neutron is emitted following the beta decay. A parameter called ``Delayed Nu-bar'' defines the mean number of delayed neutrons per fission event. Nu-bars have been measured for a number of fuels and provide a benchmark quantity from which databases can be tested. The latest ENDF-B/VII.1 library was benchmarked and sensitivity studies were carried out to understand the contribution of the uncertainties and where improvements could be achieved for Pn values. Nu-bar calculations were then performed for several of the minor actinides.

Johnson, T. D.; Sonzogni, A. A.; McCutchan, E. A.

2012-10-01

379

Late Quaternary Glacial and Vegetative History of the Glacier National Park Region, Montana.  

National Technical Information Service (NTIS)

The report presents the late Quaternary glacial and vegetative history of the Glacier National Park region, northwestern Montana, based on field mapping, volcanic ash identification, radiocarbon age determinations, and tree-ring analysis. The report docum...

P. E. Carrara

1989-01-01

380

Bactericidal and Sporicidal Activity of a Quaternary Ammonium Resin-Triiodide Complex  

PubMed Central

Tests to determine the potential use of a quaternary ammonium resin-triiodide complex as a sterilizing agent showed that it was an ineffective sporicide and that bactericidal activity was impaired by complex milieu.

Gilmour, Marion N.; Wicksell, Eva K.

1972-01-01

381

Induction of contact dermatitis in guinea pigs by quaternary ammonium compounds: the mechanism of antigen formation.  

PubMed Central

Eight quaternary ammonium compounds were tested for their ability to induce contact dermatitis in guinea pigs by using a modified Freund's complete adjuvant test together with the guinea pig maximization test. Only two quaternary ammonium salts of the eight tested could be designated as strong allergens. These two active substances were shown to be capable of stable association with membrane lipids in forming immunogenic complexes. This surface complexation phenomenon was confirmed by using a spin-labeled quaternary ammonium salt which competed for binding sites at the surface of epidermal cells in vivo. Electron spin resonance was used to demonstrate that stable "ion-pairs" are formed between binding sites and the two allergenic preservatives. Furthermore, information was obtained on the kinetics of immunogenic complex formation as well as on the position and orientation of the quaternary ammonium ion at the cell surface.

Schallreuter, K U; Schulz, K H; Wood, J M

1986-01-01

382

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

383

Spontaneous fission half-lives and their systematics  

SciTech Connect

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

Holden, N.E.

1998-03-01

384

Delayed-fission properties of neutron-deficient americium nuclei  

SciTech Connect

Characteristics of the delayed-fission decay mode in light americium nuclei have been investigated. Measurements on the unknown isotopes {sup 230}Am and {sup 236}Am were attempted, and upper limits on the delayed-fission branches of these nuclei were determined. Evidence of the existence of {sup 236}Am was observed in radiochemical separations. Total kinetic energy and mass-yield distributions of the electron-capture delayed-fission mode were measured for {sup 232}Am (t{sub 1/2} = 1.31 {plus minus} 0.04 min) and for {sup 234}Am (t{sub 1/2} = 2.32 {plus minus} 0.08 min), and delayed-fission probabilities of 6.9 {times} 10{sup {minus}4} and 6.6 {times} 10{sup {minus}5}, respectively, were determined. The total kinetic energy and the asymmetric mass-yield distributions are typical of fission of mid-range actinides. No discernible influence of the anomalous triple-peaked mass division characteristic of the thorium-radium region was detected. Measurements of the time correlation between the electron-capture x-rays and the subsequent fission conform that the observed fissions arise from the electron-capture delayed-fission mechanism. Delayed fission has provided a unique opportunity to extend the range of low-energy fission studies to previously inaccessible regions. 71 refs., 44 figs., 13 tabs.

Hall, H.L. (California Univ., Berkeley, CA (USA). Dept. of Chemistry)

1989-10-23

385

Observation of Structures in the Mass-Tke Distributions of Fission Fragments in Spontaneous Fission  

NASA Astrophysics Data System (ADS)

The number of prompt neutrons emitted in the fission event has been measured separately for each complementary fragment in coincidence with fragment mass and kinetic energies in spontaneous fission of 252Cf and 248Cm. Two high efficient Gd-loaded liquid scintillator tanks were used for the neutron registration. Approximately 3·106 fission events coincident with prompt neutron emission have been accumulated for each isotope. Two-dimensional neutron multiplicity distributions corrected for efficiency, background and pile-up have been reconstructed for each value of the fission fragment mass and total kinetic energy (TKE). Based on these unfolded multiplicity distributions fragment mass and TKE distributions for specific numbers of emitted neutrons from each of the complementary fragments have been obtained. These distributions exhibit pronounced structures reflecting the fine structures in the potential-energy surface. Structures showing a periodicity of two-masses at the edges of the mass-TKE distributions corresponding to the odd-even effect of the neutron pairing in the fissioning nucleus have been observed for the first time at large values of the fragment total excitation energy.

Kalinin, V. A.; Dushin, V. N.; Jakovlev, V. A.; Petrov, B. F.; Vorobyev, A. S.; Laptev, A. B.; Shcherbakov, O. A.; Hambsch, F.-J.

2004-02-01

386

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

PubMed Central

The Quaternary has been described as an important time for genetic diversification and speciation. This is based on the premise that Quaternary climatic conditions fostered the isolation of populations and, in some instances, allopatric speciation. However, the 'Quaternary Ice-Age speciation model' rests on two key assumptions: (i) that biotic responses to climate change during the Quaternary were significantly different from those of other periods in Earth's history; and (ii) that the mechanisms of isolation during the Quaternary were sufficient in time and space for genetic diversification to foster speciation. These assumptions are addressed by examining the plant fossil record for the Quaternary (in detail) and for the past 410 Myr, which encompasses previous intervals of icehouse Earth. Our examination of the Quaternary record indicates that floristic responses to climate changes during the past 1.8 Myr were complex and that a distinction has to be made between those plants that were able to withstand the extremes of glacial conditions and those that could not. Generation times are also important as are different growth forms (e.g. herbaceous annuals and arborescent perennials), resulting in different responses in terms of genetic divergence rates during isolation. Because of these variations in the duration of isolation of populations and genomic diversification rates, no canonical statement about the predominant floristic response to climatic changes during the Quaternary (i.e. elevated rates of speciation or extinction, or stasis) is currently possible. This is especially true because of a sampling bias in terms of the fossil record of tree species over that of species with non-arborescent growth forms. Nevertheless, based on the available information, it appears that the dominant response of arborescent species during the Quaternary was extinction rather than speciation or stasis. By contrast, our examination of the fossil record of vascular plants for the past 410 Myr indicates that speciation rates often increased during long intervals of icehouse Earth (spanning up to 50 Myr). Therefore, longer periods of icehouse Earth than those occurring during the Quaternary may have isolated plant populations for sufficiently long periods of time to foster genomic diversification and allopatric speciation. Our results highlight the need for more detailed study of the fossil record in terms of finer temporal and spatial resolution than is currently available to examine the significance of intervals of icehouse Earth. It is equally clear that additional and detailed molecular studies of extant populations of Quaternary species are required in order to determine the extent to which these 'relic' species have genomically diversified across their current populations.

Willis, Katherine J; Niklas, Karl J

2004-01-01

387

FISSION-TRACK AGES OF ZIRCONS  

Microsoft Academic Search

The fission-fragment-track dating method has been applied to zircons ranging in age from less than I m.y. to more than 100 m.y. Good agreement was obtained with ages determined by standard methods. Uranium concentrations were measured and the microscopic distribution of uranium was studied. It was found that no movement of uranium had taken place over geologic time. Crystals as

R. L. Fleischer; P. B. Price; R. M. Walker

1964-01-01

388

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

389

Fission fragment damage to crystal structures  

Microsoft Academic Search

AlâOâ and ZrSiOâ show little change in properties when ; exposed to 10¹⁸ to 10¹⁹ nvt of thermal neutrons. When, however, a ; source of fission fragments is provided in the form of a UOâ dispersant, ; the grain boundaries and the peaks of the x-ray-diffraction profile disappear on ; irradiation. The crystal structure of UâOâ is also destroyed when

B. Berman; M. L. Bleiberg; W. Yeniscavich

1960-01-01

390

LONG-RANGE PARTICLES FROM NUCLEAR FISSION  

Microsoft Academic Search

A measurement of the probability of emission of longrange particles, ; which are known to be predominantly alpha particles, made with a multiple ; ionization chamber gave the following results for spontaneous fission: Cf²⁵²; , 299 plus or minus 18; Cm²⁴², 257 plus or minus 17; Cm²⁴⁴, 314 ; plus or minus 20; Pu²⁴°, 314 approximately 20; a nd Pu²⁴²,

Ralph Nobles

1962-01-01

391

Identification of ?s isomers in fission products  

NASA Astrophysics Data System (ADS)

Several ?s isomers have been observed in the fission products of 241Pu and 239Pu. The detection is based on the time correlation between reaction products selected by the LOHENGRIN spectrometer and the ?-rays depopulating the isomers. New isomers have been observed in 96Rb, 106Nb, 127Sn, and 130Te and the others have been confirmed in 94Y, 126Sn, 129Sn and 129Sb.

Genevey, J.; Pinston, J. A.; Faust, H.; Friedrichs, T.; Gross, M.; Ibrahim, F.; Larqué, T.; Oberstedt, S.

1998-12-01

392

Featured Organism: Schizosaccharomyces pombe, The Fission Yeast  

PubMed Central

Schizosaccharomyces pombe, the fission yeast, has long been a crucial model for the study of the eukaryote cell cycle. We take a look at this important yeast, whose genome has recently been completed, featuring comments from Valerie Wood, Jürg Bähler, Ramsay McFarlane, Susan Forsburg, Iain Hagan and Paul Nurse on the implications of having the complete sequence and future prospects for pombe genomics.

2002-01-01

393

A comparison of the systemic toxicity of lidocaine versus its quaternary derivative QX-314 in mice  

Microsoft Academic Search

Purpose  We recently showed that the quaternary lidocaine derivative, QX-314, produces long-lasting local anesthesia with a slow onset\\u000a in animal models in vivo. As quaternary agents do not rapidly penetrate biological membranes or the blood-brain barrier, QX-314 may represent a local\\u000a anesthetic with decreased systemic toxicity compared with conventional tertiary aminoamines. To test this hypothesis, we conducted\\u000a an in vivo animal

Helen M. C. Cheung; Sang Mook Lee; Bernard A. MacLeod; Craig R. Ries; Stephan K. W. Schwarz

2011-01-01

394

Late Quaternary sedimentation on the Mid-Atlantic Reykjanes Ridge: clay mineral assemblages and depositional environment  

Microsoft Academic Search

Sediment samples from the Mid-Atlantic Reykjanes Ridge (59°N) were taken to get information about sediment genesis and to\\u000a identify different sources during the late Quaternary. Samples were investigated by X-ray diffraction and grain-size analyses.\\u000a The clay mineral assemblages in sediments of the Reykjanes Ridge reflect paleoceanographic changes during the late Quaternary.\\u000a Holocene sediments are characterized by high contents of smectite,

B. Gehrke; K. S. Lackschewitz; H.-J. Wallrabe-Adams

1996-01-01

395

The Inhibition of Sodium Currents in Myelinated Nerve by Quaternary Derivatives of Lidocaine  

Microsoft Academic Search

The inhibition of sodium currents by quaternary derivatives of lidocaine was studied in single myelinated nerve fibers. Membrane currents were diminished little by external quaternary lidocaine (QX). QX present in the axoplasm (<0.5 mM) inhibited sodium currents by more than 90%. Inhibition occurred as the sum of a constant, tonic phase and a variable, voltage- sensitive phase. The voltage-sensitive inhibition

GARY R. STRICHARTZ

1973-01-01

396

‘Biting effect’ stabilizing gallate-type catechin\\/quaternary ammonium ion complexes  

Microsoft Academic Search

The relationship between the structure of catechins and their binding ability for quaternary ammonium ions was examined. From binding studies using eight catechins and benzyltrimethylammonium chloride, it was revealed that the binding ability of the gallate-type catechins is much higher than that of the non-gallate-type catechins. The quaternary ammonium ion binding site of the gallate-type catechins was determined to be

Nobuyuki Hayashi; Tomomi Ujihara

2007-01-01

397

Synergistic chiral ion pair catalysts for asymmetric catalytic synthesis of quaternary ?,?-diamino acids.  

PubMed

The combination of a chiral phosphate anion with a silver ion has been demonstrated as a powerful and synergistic ion pair catalyst for the aza-Mannich reaction. A series of valuable quaternary ?,?-diamino acid derivatives was obtained in high yield, and with excellent diastereo- (up to 25:1 dr) and enantioselectivity (up to 99% ee). The adducts can be smoothly transformed into the corresponding protected chiral quaternary ?,?-diamino acids by a one-pot hydrolysis reaction. PMID:22472066

Shi, Shi-Hui; Huang, Fu-Ping; Zhu, Ping; Dong, Zhen-Wen; Hui, Xin-Ping

2012-04-03

398

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

399

Quaternary liquid–liquid equilibrium: water–phosphoric acid–1-butanol–2-butanone at 25°C  

Microsoft Academic Search

Mutual solubility and tie-line data are presented for the ternary system, water (W)–phosphoric acid (PA)–1-butanol (BuOH) and water–phosphoric acid–2-butanone (methyl ethyl ketone, MEK) at 25°C, as well as for the quaternary system, water–phosphoric acid–1-butanol–2-butanone, at the same conditions. These systems present an unusual behavior since there are no quaternary tie-line planes and the solubility surface presents a shape like a

F Ruiz; M. I Galán; N Boluda

1998-01-01

400

Characterization of â??the quaternary amine transporters of Rhizobium leguminosarum bv. viciae 3841  

Microsoft Academic Search

Rhizobium leguminosarum bv. viciae 3841 contains six putative quaternary ammonium transporters (Qat), of the ABC family. Qat6 was strongly induced by hyperosmosis although the solute transported was not identified. All six systems were induced by the quaternary amines choline and glycine betaine. It was confirmed by microarray analysis of the genome that pRL100079-83 (qat6) is the most strongly upregulated transport

Marc A. Fox; Ramakrishnan Karunakaran; Mary E. Leonard; Bouchra Mouhsine; Allan Williams; Alison K. East; J. Allan Downie; Philip S. Poole

2008-01-01

401

Algicidal Activity of a Surface-Bonded Organosilicon Quaternary Ammonium Chloride  

PubMed Central

The hydrolysis product of a quaternary amine-containing organosilicon salt, 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride, was found to exhibit algicidal activity while chemically bonded to a variety of substrates. Six representative species of Chlorophyta, Cyanophyta, and Chrysophyta were used to evaluate the algicidal activity. Substrate-bonded 14C-labeled organosilicon quaternary ammonium salt when attached to nonwoven fibers was durable to repeated washings, and algicidal activity could not be attributed to slow release of the chemical. Images

Walters, P. A.; Abbott, E. A.; Isquith, A. J.

1973-01-01

402

Investigation of part of the quaternary system Fe-Cr-Ni-Mn  

Microsoft Academic Search

1.By means of microscopic analysis, hardness and electrical resistance, an investigation was made of a triangular section of the tetrahedron of the quaternary system Fe-Cr-Ni-Mn. The section of the quaternary system chosen for investigation had as its base a section of the ternary system Fe -Cr -Ni parallel to the Fe -Cr side at a constant nickel content of 10%

I. I. Kornilov; L. E. Kantorovich

1959-01-01

403

Geomorphological effects of plate movement during Quaternary in China’s tropics  

Microsoft Academic Search

The eastern and western fronts of plate movement in Taiwan Island and Tibetan Plateau respectively are the two major sources\\u000a of tectonic force for the morphogensis during Quaternary in China’s tropics. Seven examples of geomorphological effects of\\u000a plate movement are enumerated to discuss the differentiation of tectonic landforms in space and time during Quaternary. The\\u000a tectonic movement tends to be

Zhang Weiqiang; Huang Zhenguo

2004-01-01

404

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

405

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

406

Microscopic cold fission yields of Cf252  

NASA Astrophysics Data System (ADS)

We show that the sharp maximum corresponding to Mo107 in the fragment distribution of the Cf252 cold fission is actually a Sn-like radioactivity, similar to other decay processes in which magic nuclei are involved, namely ? decay and heavy cluster emission, also called Pb-like radioactivity. It turns out that the mass asymmetry degree of freedom has a key role in connecting initial Sn with the final Mo isotopes along the fission path. We investigate the cold rearrangement of nucleons within the framework of the two-center shell model in order to compute the cold valleys in the charge equilibrated fragmentation potential. The fission yields are estimated by using the semiclassical penetration approach. We consider 5 degrees of freedom, namely the interfragment distance, the shapes of fragments, the neck parameter, and mass asymmetry. We found an isomeric minimum between the internal and external barriers. It turns out that the inner cold valley of the total potential energy is connected to the doubly magic isotope Sn132.

Mirea, M.; Delion, D. S.; S?ndulescu, A.

2010-04-01

407

A microfluidic synchronizer for fission yeast cells.  

PubMed

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

Tian, Yuan; Luo, Chunxiong; Ouyang, Qi

2013-08-21

408

Time dependent particle emission from fission products  

SciTech Connect

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

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

2010-01-01

409

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

410

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

SciTech Connect

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

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

2008-04-17

411

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

SciTech Connect

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

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

2004-09-30

412

Comparison of Fission Induced by Protons and Pions  

NASA Astrophysics Data System (ADS)

We compare the properties of fission induced by protons and pions. Three different methodologies are used to make this comparison. First, it is shown that pion-induced fission cross sections are not much different in magnitude from proton-induced fission cross sections at the same beam kinetic energy. Secondly, across the pion-nucleon (3,3) resonance so prominent with free nucleons, it has been observed that there is no significant change in the reaction mechanism in the case of pions. Thirdly, it is noted that an empirical expression used for evaluations of proton-induced fission cross sections is also valid for positive pion-induced fission cross sections, at least for actinide nuclei. Fission cross sections computed using a cascade-exciton model code for 209Bi and 238U are also compared with the experimental data available.

Zafar, Yasin; M. Ikram, Shahzad

2011-08-01

413

Electron-capture delayed fission properties of 244Es  

SciTech Connect

Electron-capture delayed fission was observed in {sup 244}Es produced via the {sup 237}Np({sup 12}C,5n){sup 244}Es reaction at 81 MeV (on target) with a production cross section of 0.31{+-}0.12 {micro}b. The mass-yield distribution of the fission fragments is highly asymmetric. The average preneutron-emission total kinetic energy of the fragments was measured to be 186{+-}19 MeV. Based on the ratio of the number of fission events to the measured number of {alpha} decays from the electron-capture daughter {sup 244}Cf (100% {alpha} branch), the probability of delayed fission was determined to be (1.2{+-}0.4) x 10{sup -4}. This value for the delayed fission probability fits the experimentally observed trend of increasing delayed fission probability with increasing Q value for electron-capture.

Shaughnessy, Dawn A.; Gregorich, Kenneth E.; Adams, Jeb L.; Lane, Michael R.; Laue, Carola A.; Lee, Diana M.; McGrath, Christopher A.; Ninov, Victor; Patin, Joshua B.; Strellis, Dan A.; Sylwester, Eric R.; Wilk, Philip A.; Hoffman, Darleane C.

2001-03-16

414

Experiments on nuclear fission induced by radioactive beams  

SciTech Connect

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

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

1994-07-01

415

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

PubMed

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

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

2013-03-21

416

Microscopic theory of singlet exciton fission. I. General formulation  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

417

Fission gas bubbles in uranium-aluminide fuels  

SciTech Connect

Formation of fission gas bubbles heretofore has not been observed in uranium-aluminide fuels. Recent irradiations to record high burnups offered a possibility to determine the onset of fission gas bubble formation in this type of fuel. Present experimental evidence suggests that UAl/sub 2/, UAl/sub 3/, and UAl/sub 4/ do not form fission gas bubbles at fission densities of 7 x 10/sup 21//cm/sup 3/ of fuel (60% depletion of 93% enriched /sup 235/U), and that pure uranium aluminide is likely to remain free of fission gas bubbles to very high /sup 235/U burnup at any enrichment. However, fission gas bubbles were found in these experimental fuels for the first time, but they were without exception associated with uranium-oxide inclusions that were evidently formed during fuel fabrication.

Hofman, G.L.

1987-04-01

418

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

419

Shell effects in fission and quasi-fission of heavy and superheavy nuclei  

Microsoft Academic Search

Results of the experiments aimed at the study of fission and quasi-fission processes in the reactions12C+204Pb,48Ca+144,154Sm,168Er,208Pb,244Pu,248Cm;58Fe+208Pb,244Pu,248Cm, and64Ni+186W,242Pu are presented in the work. The choice of the above-mentioned reactions was inspired by recent experiments on the production of the isotopes283112,289114 and283116 at Dubna [1],[2] using the same reactions. The58Fe and64Ni projectiles were chosen since the corresponding projectile-target combinations lead to the

M. G. Itkis; S. Beghini; A. A. Bogachev; L. Corradi; O. Dorvaux; A. Gadea; G. Giardina; F. Hanappe; I. M. Itkis; M. Jandel; J. Kliman; S. V. Khlebnikov; G. N. Kniajeva; N. A. Kondratiev; E. M. Kozulin; L. Krupa; A. Latina; T. Materna; G. Montagnoli; Yu. Ts. Oganessian; I. V. Pokrovsky; E. V. Prokhorova; N. Rowley; V. A. Rubchenya; A. Ya. Rusanov; R. N. Sagaidak; F. Scarlassara; A. M. Stefanini; L. Stuttge; S. Szilner; M. Trotta; W. H. Trzaska; D. N. Vakhtin; A. M. Vinodkumar; V. M. Voskressenski; V. I. Zagrebaev

2004-01-01

420

Fission-product gamma-ray and photoneutron spectra  

Microsoft Academic Search

Fission-product gamma-ray and photoneutron spectra from thermal and fast fission of ²³³U, ²³⁵U, ²³⁸U, and ²³⁹Pu have been calculated at 27 time intervals between 1 and 1000 hours following reactor shutdown. The gamma spectral calculations were made using CINDER, a depletion and fission-product code, which has been revised, extended, and variably dimensioned for applications to many problems involving irradiated materials.

M. G. Stamatelatos; T. R. England

1975-01-01

421

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

422

Fission converter heat removal and safety under accident conditions  

Microsoft Academic Search

The design and safety of the heat removal system of the Massachusetts Institute of Technology (MIT) design for a fission converter-based epithermal beam is discussed in this paper. Plate-type reactor fuel elements, used in the MIT research reactor (MITR-II), are also used for the fission converter. This fission converter-based beam provides epithermal neutron fluxes at the patient position in excess

B. Sutharshan; N. E. Todreas; O. K. Harling

1996-01-01

423

Determining the age of apatite crystals from uranium fission tracks  

Microsoft Academic Search

Further increase in sensitivity of the search for superheavy elements from the tracks of spontaneous-fission fragments in natural crystals is based on the use of partial annealing (reducing the etchable length of the tracks from the fission of uranium and plutonium nuclei by a factor of 2.5-3) and on the search for ternary-fission events of nuclei with Z >> ii0

Kh. Murtazaev; V. P. Perelygin; R. I. Petrova; S. G. Stetsenko

1991-01-01

424

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

425

Semiclassical Interpretation of the Mass Asymmetry in Nuclear Fission  

SciTech Connect

We give a semiclassical interpretation of the mass asymmetry in the fission of heavy nuclei. Using only a few classical periodic orbits and a cavity model for the nuclear mean field, we reproduce the onset of left-right asymmetric shapes at the fission isomer minimum and the correct topology of the deformation energy surface of {sup 240}Pu in the region of the outer fission barrier. {copyright} {ital 1997} {ital The American Physical Society}

Brack, M. [Institut fuer Theoretische Physik, Universitaet Regensburg, D-93040 Regensburg (Germany); Reimann, S.M. [Niels Bohr Institutet, Blegdamsvej 17, DK-2100 Copenhagen O/ (Denmark); Sieber, M. [Abteilung Theoretische Physik, Universitaet Ulm, D-89069 Ulm (Germany)

1997-09-01

426

Viscosity, fission time scale and deformation of 156Dy  

NASA Astrophysics Data System (ADS)

In the fusion-fission reaction 40Ar + 116Cd --> 156Dy* --> fission, at Eb = 216 MeV and 238 MeV, ?-rays were measured in coincidence with fission fragments. The interpretation of the ?-ray spectra is done with the help of a modified version of the statistical-model code CASCADE. The spectra can be reproduced with nuclear viscosities in the range 0.01 < ?< 4. The extracted fission time scale is of the order of 10-19 s. The CASCADE analysis seems to favor a prolate deformation with ?~ 0.45.

van't Hof, G.; Bacelar, J. C. S.; Diószegi, I.; Harakeh, M. N.; Hesselink, W. H. A.; Kalantar-Nayestanaki, N.; Kugler, A.; van der Ploeg, H.; Plompen, A. J. M.; van Schagen, J. P. S.

1998-08-01

427

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

428

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

429

SEPARATION OF PLUTONIUM FROM URANIUM AND FISSION PRODUCTS  

DOEpatents

A chromatographic adsorption process is presented for the separation of plutonium from other fission products formed by the irradiation of uranium. The plutonium and the lighter element fission products are adsorbed on a sulfonated phenol-formaldehyde resin bed from a nitric acid solution containing the dissolved uranium. Successive washes of sulfuric, phosphoric, and nitric acids remove the bulk of the fission products, then an eluate of dilute phosphoric and nitric acids removes the remaining plutonium and fission products. The plutonium is selectively removed by passing this solution through zirconium phosphate, from which the plutonium is dissolved with nitric acid. This process provides a convenient and efficient means for isolating plutonium.

Boyd, G.E.; Adamson, A.W.; Schubert, J.; Russell, E.R.

1958-10-01

430

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 20MeV. In the 33ms 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 ˜12ms 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

431

Quaternary memory device fabricated from a single layer Fe film  

NASA Astrophysics Data System (ADS)

A cross-shaped Hall device was fabricated from a single-crystal bcc Fe film having two in-plane magnetic easy axes. When a current pulse is applied to a Au strip patterned on top of the Fe Hall device, multiple domains with two orthogonal magnetization directions form in the Fe Hall device during magnetization reversal. Distributions of such domain that result in four different Hall resistance states can then be obtained by applying appropriate current pulses to the Au strip of the device. The writing of each Hall resistance state is then performed by applying a sequence of current pulses to the Au strip that generate magnetic fields required to achieve a desired domain distribution in the Fe film. Time dependent measurements show remarkably robust temporal stability for all four Hall resistance states. The demonstration of the writing process for the four distinct states in this Fe Hall device by current pulse sequences provides the possibility of realizing a practical room-temperature quaternary memory device in a single ferromagnetic film.

Yoo, Taehee; Khym, S.; Lee, Hakjoon; Lee, Sangyeop; Lee, Sanghoon; Liu, X.; Furdyna, J. K.; Lee, Dong Uk; Kyu Kim, Eun

2012-04-01

432

Electrochemical properties of quaternary ammonium salts for electrochemical capacitors  

SciTech Connect

The limiting reduction and oxidation potentials and electrolytic conductivities of new quaternary ammonium salts were examined for electrochemical capacitor applications, whose anions have already been tested as lithium salts for lithium battery applications. The anodic stability was in the following order BR{sub 4}{sup {minus}} < ClO{sub 4}{sup {minus}} {le} CF{sub 3}SO{sub 3}{sup {minus}} < (CF{sub 3}SO{sub 2}){sub 2}N{sup {minus}} {le} C{sub 4}F{sub 9}SO{sub 3}{sup {minus}} < BF{sub 4}{sup {minus}} < PF{sub 6}{sup {minus}} {le} AsF{sub 6}{sup {minus}} < SbF{sub 6}{sup {minus}}. The electrolytic conductivities of Me{sub 4{minus}n}Et{sub n}N(CF{sub 3}SO{sub 2}){sub 2}N (n = 0--4) were examined in comparison with Me{sub 4{minus}n}Et{sub n}NBF{sub 4} counterparts. These imide salts showed good solubility, relatively high conductivity, and anodic stability in propylene carbonate. Et{sub 4}N(CF{sub 3}SO{sub 2}){sub 2}N was found to be a good supporting salt for low permittivity organic solvents, and it afforded a highly conductive electrolyte system based on the ethylene carbonate-dimethyl carbonate mixed solvent, which is useful for electrochemical capacitor applications.

Ue, Makoto; Takeda, Masayuki; Takehara, Masahiro; Mori, Shoichiro [Mitsubishi Chemical Corp., Inashiki, Ibaraki (Japan). Tsukuba Research Center

1997-08-01

433

Causal link between Quaternary paleoclimatic changes and volcanic islands evolution  

NASA Astrophysics Data System (ADS)

High precision radiometric ages of large-volume volcanic flank collapses indicate a causal relationship between the evolution of volcanic islands from different geodynamic contexts and global climatic changes. We present a compilation of previously well-dated events within the last 1 Myr from Tahiti, Hawaii, Canary Islands, together with new ages from Guadeloupe and Martinique (Lesser Antilles). Ages of major flank collapses show a strong correlation with Quaternary climate changes evidenced by a global stack of benthic d18O records. Effectively, most collapses occurred within a glacial to interglacial termination. The ages reported here favor the hypothesis that for the last 900 kyr major flank collapse events occurred during the onset of glacial to interglacial transitions when a sudden influx of melt water from polar ice caps results in rapid sea level rise. Thus, it can be inferred that, when geological causes such as regional tectonics or edifice strength reduction due to volcanic processes are also present, rapid sea level rise can favor large mass wasting events. We propose that following a sub aerial erosion interval during low sea level stands, rapid sea level rise induces enhanced coastal erosion and sudden changes of pore pressure conditions within basal layers, which favor edifice failure. Since these events can trigger tsunamis and can initiate periods of increased volcanic activity, we show here that global warming may result in an increased likelihood of certain geologic hazards, such as large landslides of up to several hundreds cubic kilometers.

Quidelleur, X.; Hildenbrand, A.; Samper, A.

2006-12-01

434

Latest quaternary volcanism in the St. George Basin, southwestern Utah  

SciTech Connect

The St. George Basin was the site of mafic volcanism from about 6 Ma to 1 ka. The nature of latest Quaternary volcanism is of interest because the Basin is recognized as a low temperature (< 90C) geothermal resource area and it is part of the transition zone between the Basin and Range Province and the Colorado Plateau. The authors have studied the geochemistry, mineralogy, and aerial distribution of two of the youngest eruptions centers: (1) Veyo Volcano; and (2) the Diamond Valley scoria cones (DVSC). Veyo Volcano erupted basaltic andesite, beginning with an explosive stage marked by a 0.5 m basal Plinian layer. Later eruptions alternated between quiescent and Strombolian-styles. Phenocrysts include clear plagioclase, sieve-texture plagioclase, olivine and rare augite. The DVSC and associated Santa Clara lava flow are tholeiitic basalt, consisting of olivine phenocrysts, and rare plagioclase phenocrysts. Based on preliminary geochemical data, Diamond Valley rocks exhibit lower incompatible element ratios compared to mafic rocks on the Markagunt Plateau and transition zone rocks. In contrast, Veyo Volcano rocks are similar to transition zone mafic rocks with regard to incompatible element abundances.

Millings, V.T. III; Green, J.D.; Nusbaum, R.L. (Coll. of Charleston, SC (United States). Dept. of Geology)

1993-03-01

435

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

436

Quaternary heteroaromatic salts with prophylactic and antidotal activity towards soman  

SciTech Connect

A series of quaternary heteroaromatic salts has been prepared and evaluated for prophylactic and antidotal activity towards the lethal toxicity of soman. One series of compounds contains 2-, 3-, or 4-(dimethylaminocarbonyloxy)phenoxymethyl substituents at the 2 position of the following rings: 1,3-dimethylimidazolium, 1-methylpyridinium, 1-methylquinolinium, 1,3-dimethylbenzimidazolium and 1-methylimidazo1,2-Apyridinium. The compounds were evaluated both in vitro, by determining the IC50 for electric eel acetylcholinesterase, and in vivo, using both antidotal and prophylactic assays in mice. Compound 2b was most active in the in vitro assay (IC50 = 0.01 M). However, its toxicity is high and compound la is more effective in vivo with 80-100% protective activity against 2 LD50 of soman at 6.2 to 62.5 mg/kg. A second series of compounds consisted of 6-substituted 2'-, 3'-, and 4'-(dimethylaminocarbonyloxy) phenylimidazo (1,2-a) pyridinium salts (8).

Sundberg, R.J.; Dalvie, D.; Cordero, J.; Sabat, M.

1993-05-13

437

Quaternary geology of the Rhode Island inner shelf  

USGS Publications Warehouse

Five sedimentary units and three erosional unconformities identified in high-resolution seismic-reflection profiles reveal the stratigraphic framework and Quaternary history of the inner continental shelf south of Narragansett Bay, Rhode Island. Late Tertiary to early Pleistocene rivers eroded the pre-Mesozoic bedrock and the Upper Cretaceous to lower Tertiary coastal plain and continental shelf strata to form a lowland and cuesta having a north-facing escarpment. The lowland and landward flanks of the cuesta were modified by glaciers during Pleistocene time and subsequently were overlain by drift and end moraine deposits of the late Wisconsinan ice advance. During deglaciation, freshwater lakes formed between the retreating ice and end moraines. Prior to sea-level rise, the drift and older deposits were cut by streams flowing south and southwestward toward Block Island Sound. As sea level rose, postglacial valleys were partly filled by fluvial, freshwater-peat, estuarine and salt-marsh deposits. Transgressing seas eroded the sea floor, exposing bedrock and coastal plain outcrops, and deposited marine sediments. ?? 1983.

Needell, S. W.; O'Hara, C. J.; Knebel, H. J.

1983-01-01

438

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

2011-09-09

439

Effects of late quaternary climate change on Palearctic shrews.  

PubMed

The Late Quaternary was a time of rapid climatic oscillations and drastic environmental changes. In general, species can respond to such changes by behavioral accommodation, distributional shifts, ecophenotypic modifications (nongenetic), evolution (genetic) or ultimately face local extinction. How those responses manifested in the past is essential for properly predicting future ones especially as the current warm phase is further intensified by rising levels of atmospheric carbon dioxide. Here, we use ancient DNA (aDNA) and morphological features in combination with ecological niche modeling (ENM) to investigate genetic and nongenetic responses of Central European Palearctic shrews to past climatic change. We show that a giant form of shrew, previously described as an extinct Pleistocene Sorex species, represents a large ecomorph of the common shrew (Sorex araneus), which was replaced by populations from a different gene-pool and with different morphology after the Pleistocene Holocene transition. We also report the presence of the cold-adapted tundra shrew (S. tundrensis) in Central Europe. This species is currently restricted to Siberia and was hitherto unknown as an element of the Pleistocene fauna of Europe. Finally, we show that there is no clear correlation between climatic oscillations within the last 50 000 years and body size in shrews and conclude that a special nonanalogous situation with regard to biodiversity and food supply in the Late Glacial may have caused the observed large body size. PMID:23505017

Prost, Stefan; Klietmann, Johannes; van Kolfschoten, Thijs; Guralnick, Robert P; Waltari, Eric; Vrieling, Klaas; Stiller, Mathias; Nagel, Doris; Rabeder, Gernot; Hofreiter, Michael; Sommer, Robert S

2013-03-09

440

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

2012-03-08

441

Facilitating Progress on the Quaternary History of Sea Level Change  

NASA Astrophysics Data System (ADS)

Understanding Future Sea Level Rise: The Challenges of Dating Past Interglacials; Woods Hole, Massachusetts, 20-25 September 2009; Substantial uncertainty exists in projections of future sea level rise, due primarily to a lack of understanding about ice sheet dynamics. Paleo Constraints on Sea Level Rise (PALSEA) is a working group of the Past Global Changes (PAGES) project and the International Marine Global Change Studies (IMAGES) program that aims to extract information about ice sheet response to temperature change by examining the history of sea level over the Quaternary (spanning the past ˜2.5 million years). In particular, PALSEA focuses on the past 800,000 years, particularly interglacial periods, with a range of temperatures bracketing the modern. PALSEA recently held a workshop at Woods Hole Oceanographic Institution (WHOI). Funded by IMAGES, PAGES, and WHOI's Ocean and Climate Change Institute, the workshop focused on challenges in uranium-thorium (U-Th) coral dating. The meeting also included a public outreach event, “Where land and sea meet: Managing shoreline change over the next 100 years,” funded by WHOI's Morss Colloquium.

Thompson, W. G.; Andersen, M. B.

2010-04-01

442

Resistance to quaternary ammonium compounds in food-related bacteria.  

PubMed

Microbial resistance to antimicrobial agents continues to be a major problem. The frequent use and misuse of disinfectants based on quaternary ammonium compounds (QACs) in food-processing industries have imposed a selective pressure and may contribute to the emergence of disinfectant-resistant microorganisms. A total number of 1,325 Gram-negative isolates (Escherichia coli, other coliforms Vibrio spp., and Aeromonas spp.) and 500 Enterococcus spp. from food and food-processing industries and fish farming were screened for natural resistance to the QAC-based disinfectant benzalkonium chloride (BC). Of the 1,825 isolates, 16 strains, mainly from meat retail shops, showed low-level resistance to BC. None of the Enterococcus spp. from broiler, cattle, and pigs, the antibiotic-resistant E. coli from pig intestine and fish pathogens Vibrio spp. and Aeromonas spp. from the Norwegian fish farming industry were resistant to BC. The BC-resistant strains were examined for susceptibility to 15 different antibiotics, disinfectants, and dyes. No systematic cross-resistance between BC and any of the other antimicrobial agents tested was detected. Stable enhanced resistance in Enterobacter cloacae isolates was demonstrated by step-wise adaptation in increasing concentrations of BC. In conclusion, BC resistance among food-associated Gram-negative bacteria and Enterococcus spp. is not frequent, but resistance may develop to user concentrations after exposure to sublethal concentrations of BC. PMID:12523638

Sidhu, Maan Singh; Sørum, Henning; Holck, Askild

2002-01-01

443

Late Quaternary Environment Of Central Yakutia, East Siberia  

NASA Astrophysics Data System (ADS)

A Russian-German joint project, investigating the late Quaternary development of periglacial and glacial landscapes, lacustrine systems, as well as permafrost complexes and ground ice features in central Yakutia, is currently in progress. Field work was carried out in 2002 and 2003 along the Tumara and Djanushka rivers in the Verkhoyansk Mountains and its foreland, and in 2004 in the alass region northeast of Yakutsk. Geomorphological and sedimentological findings, satellite-image evaluation, and first dating results by optical-stimulated luminescence give evidence of multiple glacial advances in the foreland of the Verkhoyansk Mountains that were not in phase with variations in global ice volume. The last episode with extended piedmont glaciers entering the Verkhoyansk foreland took place around 32 ka BP. No major glacier advances are evident for the global last glacial maximum, because dry conditions apparently prevented sufficient snow and ice accumulation, as suggested by the deposition of extended loess-like sediments at that time. Stable-isotope records of ice wedges, as indicators of palaeo winter temperatures, together with pollen records from Lake Satagay give evidence of an early Holocene climate optimum between approximately 8.0 and 6.0 ka BP, followed by climate deterioration during the late Holocene. Variations in the concentration and composition of organic matter in the Lake Satagay sediment record, moreover, reveal pronounced fluctuations of lake-level status, attributed to short-term climate oscillations at centennial time scales that caused cyclic changes in aridity.

Diekmann, B.; Lehmkuhl, F.; Andreev, A.; Frechen, M.; Hubberten, H.; Pestryakova, L.; Popp, S.; Siegert, C.; Spektor, V.; Stauch, G.

2004-12-01

444

Quaternary ammonium sulfanilamide: a membrane-impermeant carbonic anhydrase inhibitor  

SciTech Connect

A novel carbonic anhydrase (CA) inhibitor, quaternary ammonium sulfanilamide (QAS), was tested for potency as a CA inhibitor and for its ability to be excluded from permeating biological membranes. Inhibitor titration plots of QAS vs. pure bovine CA II and CA from the gills of the blue crab, Callinectes sapidus, yielded K/sub i/ values of approx. 15 ..mu..M; thus QAS is a relatively weak but effective CA inhibitor. Permeability of the QAS was directly tested by two independent methods. The inhibitor was excluded from human erythrocytes incubated in 5 mM QAS for 24 h as determined using an /sup 18/O-labeled mass spectrometer CA assay for intact cells. Also QAS injected into the hemolymph of C. sapidus (1 or 10 mM) did not cross the basal membrane of the gill. The compound was cleared from the hemolymph by 96 h after injection, and at no time during that period could the QAS be detected in homogenates of gill tissue. Total branchial CA activity was only slightly reduced following the QAS injection. These data indicate that QAS is a CA inhibitor to which biological membranes are impermeable and that can be used in vivo and in vitro in the study of membrane-associated CA.

Henry, R.P.

1987-05-01

445

Synthesis and aggregation behavior of a hexameric quaternary ammonium surfactant.  

PubMed

A star-shaped hexameric quaternary ammonium surfactant (PAHB), bearing six hydrophobic chains and six charged hydrophilic headgroups connected by an amide-type spacer group, was synthesized. The self-assembly behavior of the surfactant in aqueous solution was studied by surface tension, electrical conductivity, isothermal titration microcalorimetry, dynamic light scattering, cryogenic transmission electron microscopy, and NMR techniques. The results reveal that there are two critical aggregate concentrations during the process of aggregation, namely C(1) and C(2). The aggregate transitions are proved to be caused by the changes of the surfactant configuration through hydrophobic interaction among the hydrocarbon chains. Below C(1), PAHB may present a star-shaped molecular configuration due to intramolecular electrostatic repulsion among the charged headgroups, and large aggregates with network-like structure are observed. Between C(1) and C(2), the hydrophobic interaction among the hydrophobic chains may become stronger to make the hydrophobic chains of the PAHB molecules curve back and pack more closely, and then the network-like aggregates transfer to large spherical aggregates of ?100 nm. Beyond C(2), the hydrophobic interaction may become strong enough to cause the PAHB molecular configuration to turn into a pyramid-like shape, resulting in the transition of the spherical large aggregates to spherical micelles of ?10 nm. Interestingly, the PAHB displays high emulsification ability to linear fatty alkyls even at very low concentration. PMID:21797217

Fan, Yaxun; Hou, Yanbo; Xiang, Junfeng; Yu, Defeng; Wu, Chunxian; Tian, Maozhang; Han, Yuchun; Wang, Yilin

2011-08-09

446

Ancient lithospheric source for Quaternary lavas in Hispaniola  

NASA Astrophysics Data System (ADS)

Fragments of ancient continental lithosphere, entrained in the shallow oceanic mantle, have been found in a number of locations in the Southern Hemisphere, including rare arc settings. Lavas erupted in these locations exhibit Pb isotopic characteristics that are similar to the so-called enriched mantle 1 reservoir, one of the end-members that define the isotopic composition of the Earth's mantle. However, no lavas with isotopic signatures resembling enriched mantle 1 have been identified in the Caribbean region. Here we present isotopic analyses for mafic-alkaline lavas from Quaternary volcanic centres in Hispaniola. We identify unusual isotopic characteristics indicating the presence of a mantle component similar to enriched mantle 1 beneath Hispaniola. Furthermore, we find evidence for an involvement of this mantle component in the genesis of spatially associated calk-alkaline lavas. On the basis of these isotopic systematics we estimate that the mafic-alkaline lavas are derived from an ancient lithospheric fragment with affinities to the supercontinent Gondwana. We conclude that the fragment originated from the Grenvillian terranes of Central America and Mexico, which also have affinities to Gondwana, indicating that Hispaniola interacted tectonically with these terranes.

Kamenov, George D.; Perfit, Michael R.; Lewis, John F.; Goss, Adam R.; Arévalo, Ricardo; Shuster, Robert D.

2011-08-01

447

Coal cleaning employing quaternary salts. Annual report, July 1, 1984-June 30, 1985. [Tetrabutyl ammonium hydroxide; tetramethyl ammonium hydroxide  

SciTech Connect

An investigation into a novel approach to coal desulfurization has been initiated. This approach is in the formative stages, but is envisioned to included a treatment step to swell coal in quaternary salt solution followed by physical separation, chemical reaction to desulfurize the coal, and recovery of the quaternary salt. The present program was aimed at developing fundamental data associated with the first step. This report covers the first six months of the project. The objective of this portion of the program was to define conditions under which complete exchange of quaternary salts with coal hydroxy groups occurs, define the extent of coal swelling and changes in coal properties as a function of amount of exchange, and determine the effect of process variation on swelling rate and coal properties. Results of this research have demonstrated that substantial coal swelling occurs in the presence of quaternary salts. The amount of quaternary exchange is a small portion of the total OH groups present in the coal. Swelling has been found to be dependent on the concentration of quaternary salts, the ratio of solution to coal, time of exchange, and the type of solvent. The data also demonstrate that particle size and size distribution are changed extensively by the quaternary salt treatment. Furthermore, it appears that iron sulfide and/or sulfate are dissolved in the quaternary base. Also, some organic material is dissolved by the quaternary base. Preliminary data indicate that minerals and inertinite can be concentrated after quaternary salt treatment. The results indicate that quaternary recovery should be easier than first expected. Also, the excessive swelling with little exchange indicated that the surface chemistry of the coal is altered after exchange. Thus, oil agglomeration and froth flotation should be improved when coals are treated with the quaternary salt. 11 refs., 11 tabs.

Hippo, E.J.; Murdie, N.

1985-09-01

448

Micropaleontologic record of late Pliocene and Quaternary paleoenvironments in the northern Albemarle Embayment, North Carolina, U.S.A  

Microsoft Academic Search

Micropaleontological data provide a strong actualistic basis for detailed interpretations of Quaternary paleoenvironmental change. The 90 m-thick Quaternary record of the Albemarle Embayment in the mid-Atlantic coastal plain of the USA provides an excellent opportunity to use such an approach in a region where the details of Quaternary environmental change are poorly known.The foraminiferal record in nine cores from the northern

Stephen J. Culver; Kathleen M. Farrell; David J. Mallinson; Benjamin P. Horton; Debra A. Willard; E. Robert Thieler; Stanley R. Riggs; Scott W. Snyder; John F. Wehmiller; Christopher E. Bernhardt; Caroline Hillier

2008-01-01

449

Entrance-channel dependence of fission-fragment anisotropies: A direct experimental signature of fission before equilibration  

Microsoft Academic Search

Fission-fragment angular distributions in reactions of 10B, 12C, 16O+232Th and 237Np, and 19F+237Np have been measured. While the measured anisotropies in B- and C-induced fission are found to be in agreement with the predictions of the standard Halpern-Strutinsky theory, they are anomalously large in the case of O- and F-induced fission. Such a discontinuous behavior in angular anisotropy with respect

V. S. Ramamurthy; S. S. Kapoor; R. K. Choudhury; A. Saxena; D. M. Nadkarni; A. K. Mohanty; B. K. Nayak; S. V. Sastry; S. Kailas; A. Chatterjee; P. Singh; A. Navin

1990-01-01

450

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

451

Advanced Monte Carlo modeling of prompt fission neutrons for thermal and fast neutron-induced fission reactions on Pu239  

Microsoft Academic Search

Prompt fission neutrons following the thermal and 0.5 MeV neutron-induced fission reaction of Pu239 are calculated using a Monte Carlo approach to the evaporation of the excited fission fragments. Exclusive data such as the multiplicity distribution P(nu), the average multiplicity as a function of fragment mass nu¯(A), and many others are inferred in addition to the most used average prompt

P. Talou; B. Becker; T. Kawano; M. B. Chadwick; Y. Danon

2011-01-01

452

Advanced Monte Carlo modeling of prompt fission neutrons for thermal and fast neutron-induced fission reactions on ²³Pu  

Microsoft Academic Search

Prompt fission neutrons following the thermal and 0.5 MeV neutron-induced fission reaction of ²³Pu are calculated using a Monte Carlo approach to the evaporation of the excited fission fragments. Exclusive data such as the multiplicity distribution P(), the average multiplicity as a function of fragment mass -bar(A), and many others are inferred in addition to the most used average prompt

P. Talou; T. Kawano; B. Becker; Y. Danon; M. B. Chadwick

2011-01-01

453

Event-by-event study of photon observables in spontaneous and thermal fission  

NASA Astrophysics Data System (ADS)

The event-by-event fission model freya is employed to study photon observables in spontaneous fission and fission induced by thermal neutrons. Comparison with available data is made as far as possible, including some recent correlation studies.

Vogt, R.; Randrup, J.

2013-04-01

454

Scientists Identify New Quaternary Materials for Solar Cell Absorbers (Fact Sheet), NREL Highlights, Science  

SciTech Connect

Research provides insight for exploring use of earth-abundant quaternary semiconductors for large-scale solar cell applications. For large-scale solar electricity generation, it is critical to find new material that is Earth abundant and easily manufactured. Previous experimental studies suggest that Cu{sub 2}ZnSnS{sub 4} could be a strong candidate absorber materials for large-scale thin-film solar cells due to its optimal bandgap, high adsorption coefficient, and ease of synthesis. However, due to the complicated nature of the quaternary compound, it is unclear whether other quaternary compounds have physical properties suitable for solar cell application. Researchers at the National Renewable Energy Laboratory (NREL), Fudan University, and University College London have performed systematic searches of quaternary semiconductors using a sequential cation mutation method in which the material properties of the quaternary compounds can be derived and understood through the evolution from the binary, to ternary, and to quaternary compounds. The searches revealed that in addition to Cu{sub 2}ZnSnS{sub 4}, Cu{sub 2}ZnGeSe{sub 4} and Cu{sub 2}ZnSnSe{sub 4} are also suitable quaternary materials for solar cell absorbers. Through the extensive study of defect and alloy properties of these materials, the researchers propose that to maximize solar cell performance, growth of Cu{sub 2}ZnSnS{sub 4} under Cu-poor/Zn-rich conditions will be optimal and the formation of Cu{sub 2}ZnSn(S,Se){sub 4} alloy will be beneficial in improving solar cell performance.

Not Available

2011-10-01

455

Neutron Multiplicities in Heavy-Ion Induced Fission: Timescale of Fusion-Fission.  

National Technical Information Service (NTIS)

Neutron-fission fragment angular correlations have been measured for the compound nuclei sup 168 Yb, sup 192 Pb, sup 198 Pb, sup 200 Pb, sup 210 Po, sup 213 Fr and sup 251 Es, formed at excitation energies between 45 and 90 MeV by fusion reactions induced...

D. J. Hinde R. J. Charity G. S. Foote J. R. Leigh J. O. Newton

1985-01-01

456

Measurement of the fission yields of selected prompt and decay fission  

SciTech Connect

Gamma-ray spectrometry measurements have been made of the fission yields of selected ?-rays emitted by the spontaneously fissioning isotopes 252Cf and 244Cm. The measured ?-rays were selected based on their relative abundance in the spectrum and their freedom from interference or, in a few instances, ease of interference correction. From these data and the cumulative and independent yield data of ENGLAND and RIDER, those ?-rays that are primarily produced by radioactive decay, as opposed to direct yield, were converted into the decays per spontaneous fission expressed in percent and compared to cumulative yield values of ENGLAND and RIDER. For those ?-rays whose production is dominated by direct (independent) yield, the ratio of ?-rays per spontaneous fission is reported. The ?-ray yield can be compared to the independent yield values of ENGLAND and RIDER when 100% of the direct feeding passes through the ?-ray. In those cases where both cumulative and independent yields contribute to the observed ?-ray emission rate, a direct comparison is not possible but a method to quantify the contribution from each is proposed.

E.L. Reber; R.J. Gehrke; R. Aryaeinejad; J.K. Hartwell

2005-03-01

457

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

458

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

459

Recent Measurements with the NIFFTE Fission TPC  

NASA Astrophysics Data System (ADS)

The NIFFTE Time Projection Chamber (TPC) is a powerful tool being developed to take precision measurements of neutron-induced fission cross sections of transuranic elements. These improved data are needed for applications including the development of future generations of nuclear reactors. During the last run at the Los Alamos Neutron Science Center (LANSCE) the partially instrumented TPC took data with several different targets. Results from this run will be shared including an update on the measurement of the cross section ratio for U-238 to U-235.

Towell, Rusty

2012-10-01

460

SEPARATION OF URANIUM, PLUTONIUM AND FISSION PRODUCTS  

DOEpatents

The separation of uranium and plutonium from neutronirradiated uranium is described. The neutron-irradiated uranium is dissolved in nitric acid to provide an aqueous solution 3N in nitric acid. The fission products of the solution are extruded by treating the solution with dibutyl carbitol substantially 1.8N in nitric acid. The organic solvent phase is separated and neutralized with ammonium hydroxide and the plutonium reduced with hydroxylamine base to the trivalent state. Treatment of the mixture with saturated ammonium nitrate extracts the reduced plutonium and leaves the uranium in the organic solvent.

Nicholls, C.M.; Wells, I.; Spence, R.

1959-10-13

461

(Fission product transport processes in reactor accidents)  

SciTech Connect

The purpose of this trip was to participate in and to hold informal discussions with other participants in the International Centre for Heat and Mass Transfer (ICHMT) International Seminar on Fission Product Transport Processes held at Dubrovnik, Yugoslavia, during the week of May 22--26, 1989. There were 129 participants from 20 countries at the Seminar. The travelers delivered two invited lectures and presented four invited papers based upon NRC-sponsored work at Oak Ridge National Laboratory. One of the travelers also served as Chairman of the Session entitled Transport Phenomena in the Reactor Coolant System'' and appeared as a Panelist in the Closing Session of the Seminar.

Hodge, S.A.; Beahm, E.C.; Kress, T.S.; Malinauskas, A.P.

1989-06-14

462

Material recognition using fission gamma rays  

NASA Astrophysics Data System (ADS)

Material recognition is studied by measuring the transmission spectrum of 252Cf fission gamma rays in the energy range E?=0.1-5.5 MeV for 0.1-MeV-wide energy bins through a number of elementary samples. Each transmitted spectrum is compared with a library of reference spectra for different elements providing the possibility of material identification. In case of elemental samples with known thickness, this procedure allows the identification of the sample Z with uncertainty typically lower than 3 Z-units over a wide range of elements. Applications to composite materials are also reported.

Viesti, G.; Sajo-Bohus, L.; Fabris, D.; Lunardon, M.; Moretto, S.; Nebbia, G.; Pesente, S.

2009-07-01

463

Characteristics of SCR seismicity inferred from Australia's Quaternary faulting record  

NASA Astrophysics Data System (ADS)

Australia boasts arguably the richest Quaternary faulting record in all of the world's stable continental region (SCR) crust. Variation in Quaternary fault scarp length, vertical displacement, relation to other faults and to topography, justifies the division of the continent according to fault character. Six onshore "neotectonic domains" are recognised. Each domain relates to a distinct underlying crustal type and architecture, which can be broadly assigned to the classes: cratonic, non-cratonic and extended. Scarp length provides a means of estimating the maximum magnitude earthquake possible in each domain, while displacement/scarp height (or total relief) permits estimation of activity rate. In general, as has previously been recognised, higher activity is associated with extended crust than with non-extended crust. Application of this domains model permits greater confidence in identifying analogous systems elsewhere in the world. A common characteristic across Australia appears to be the temporal clustering of large earthquakes - periods of earthquake activity comprising a finite number of large events are separated by much longer periods of seismic quiescence. In several instances there is evidence for deforming regions at scales of several hundred kilometres switching on and off over the last several million years. What is not clear from the limited available paleoseismic data is whether successive active periods are comparable in terms of slip, number of events, magnitude of events, etc. Irrespective, this apparent bimodal recurrence behaviour poses problems for probabilistic seismic hazard assessment (PSHA) in that it implies that large earthquake recurrence is not random (i.e. Poissonian). The points critical to understanding the hazard posed by SCR faults, and modelling this hazard probabilistically, become: 1) is the fault in question in the midst of an active period, or in a quiescent period; 2) how many large events might constitute an active period, and how many ruptures has the fault generated so far in its current active period (should it be in one); and 3) what is the mean recurrence interval in an active period, and what is the variability around this mean? This data might be incorporated statistically into PSHAs. Calculations based upon data from Australia's national geodetic network (~1000-2000 km spacing between observation points) over the past several decades indicate relative displacements less than 1mm/a at the 95% confidence level. At a regional scale, any crustal deformation in the two seismic zones where dense campaign GPS networks have been constructed (~20-50 km observation spacing), is yet to emerge from the measurement uncertainty, despite ongoing micro- to moderate magnitude seismicity. This, together with the paleoseismological evidence for bimodal rupture histories from across Australia, is consistent with a model of low strain accumulation and rapid strain release. This is contrary to the plate margin paradigm, where strain accumulation and release rates are assumed to be roughly comparable.

Clark, D.; McPherson, A.

2011-12-01

464

Measurement of prompt gamma-ray emission in fission  

NASA Astrophysics Data System (ADS)

In this work we present results from the characterization of both LaCl3:Ce scintillation and polycrystalline diamond detectors to be used for measurements of prompt gamma radiation emitted in fission. The properties of these new detector types, such as excellent timing resolution and improved energy resolution will allow to obtain fission data with higher accuracy than those available today.

Borcea, R.; Billnert, R.; Geerts, W.; Hambsch, F.-J.; Tornin, R. Jaime; Karlsson, J.; Oberstedt, A.; Oberstedt, S.

2010-01-01

465

Gamma-Ray Spectra of Fractionated Fission Products.  

National Technical Information Service (NTIS)

To determine the effects of fractionation on gamma-ray exposure rates in fission-product fields, spectra of gamma-rays emitted by fractionated products of thermal neutron fission of 235U were studied. Controlled fractionation was brought about by sweeping...

D. Sam L. R. Bunney

1971-01-01

466

The Capture and Loss of Electrons by Fission Fragments  

Microsoft Academic Search

We calculate the effective charge of fission fragments passing through a low pressure gas. We first compute, on a classical basis, the cross section for capture of an electron by a fission fragment of relatively arbitrary charge and velocity. We then develop a rough theory which gives the cross section for loss of an electron through interaction with a gas

George I. Bell

1953-01-01

467

Characteristics of diallyl phthalate resin as a fission track detector  

Microsoft Academic Search

Diallyl phthalate (DAP) resin plates were irradiated with fission fragments, and then etched in aqueous solution of KOH. Etched tracks were observed and counted by using an optical microscope. The detection efficiency of fission fragments was about 100% for both perpendicular and random incidence. DAP plates were insensitive to alpha particles and fast neutrons. These characteristics are suitable for detecting

T. Tsuruta

1999-01-01

468

Statistical scission model of fission-fragment angular distributions  

Microsoft Academic Search

A statistical scission model is applied to heavy-ion--induced fission. Comparison of model calculations to experimental data on fission-fragment angular distributions shows excellent agreement for systems in a large range of fissility parameter, excitation energy, and spin value. For many of these reactions, the traditional transition-state model and its extensions are inapplicable or fail to reproduce the data.

H. H. Rossner; J. R. Huizenga; W. U. Schroeder

1984-01-01

469

Effect of viscosity on the dynamics of fission  

Microsoft Academic Search

The effect of ordinary viscosity on nuclear fission is studied by solving classical equations of motion for the time evolution of fissioning nuclei. The collective potential energy is calculated both by means of the usual liquid-drop model and by means of a modified liquid-drop model that takes into account the lowering in the nuclear macroscopic energy due to the finite

K. T. R. Davies; A. J. Sierk; J. R. Nix

1976-01-01

470

Yields of fragments of the spontaneous fission of Cf 252  

Microsoft Academic Search

At the time this work ended, the article [4] was published, in which the yields of fragments of the spontaneous fission of Cf 252 in the region of masses 95-147 were determined relative to the yields of the fragments of fission of U 23s with thermal neutrons. The comparison fragment selected was Ba i4~ the yield of which for the

N. V. Skovorodkin; G. E. Lozhkomoev; K. A. Petrzhak; A. V. Sorokina; B. M. Aleksandrov; A. S. Krivokhatskii

1973-01-01

471

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

472

NUCLEAR FISSION IN THE EARLY HISTORY OF THE EARTH  

Microsoft Academic Search

Differences in the isotopic ratios of xenon in the Earth's atmosphere ; and in the Richardson meteorite are discussed. The differences indicate that at ; least 10% of the atmospheric xenon-138 is fissiogenic. This is much greater than ; that expected from the uranium-238 spontaneous fission alone but can be explained ; as due to the spontaneous fission of some

P. K. KURODA

1960-01-01

473

Nuclear fission in heavy elements by high-energy particles  

Microsoft Academic Search

The results of a radiochemical investigation of nuclear fission in uranium, thorium, and bismuth by protons with an energy of 680 Mev are presented. Using an interpolation method a complete chart of the fission residue products is obtained. It is noted that there is a predominance in the production of nuclei with excess neutrons (58–64%); it is also shown that

A. K. Lavrukhina; L. D. Krasavina

1957-01-01

474

Semiclassical Interpretation of the Mass Asymmetry in Nuclear Fission  

Microsoft Academic Search

We give a semiclassical interpretation of the mass asymmetry in the fission of heavy nuclei. Using only a few classical periodic orbits and a cavity model for the nuclear mean field, we reproduce the onset of left-right asymmetric shapes at the fission isomer minimum and the correct topology of the deformation energy surface of 240Pu in the region of the

M. Brack; S. M. Reimann; M. Sieber

1997-01-01

475

Neutron Multiplicity At Spontaneous Fission Of 246Fm  

NASA Astrophysics Data System (ADS)

For experiments aimed at the study of spontaneous fission of transfermium nuclei improvements in the focal plane detector system of recoil separa tor VASSILISSA have been made. The neutron detector consisting of 54 3He -filled counters has been mounted around the focal plane detector chamber. The multiplicity of prompt neutrons emitted in spontaneous fission of 246 Fm was measured.

Svirikhin, A. I.; Yeremin, A. V.; Chelnokov, M. L.; Chepigin, V. I.; Izosimov, I. V.; Katrasev, D. E.; Malyshev, O. N.; Minkova, A.; Popeko, A. G.; Sokol, E. A.

2010-04-01

476

Neutron multiplicity at spontaneous fission of 246Fm  

NASA Astrophysics Data System (ADS)

For experiments aimed at the study of spontaneous fission of transfermium nuclei improvements in the focal plane detector system of recoil separator VASSILISSA have been made. The neutron detector consisting of 54 3He-filled counters has been mounted around the focal plane detector chamber. The multiplicity of prompt neutrons emitted in spontaneous fission of 246Fm was measured.

Svirikhin, A. I.; Yeremin, A. V.; Chelnokov, M. L.; Chepigin, V. I.; Izosimov, I. V.; Katrasev, D. E.; Malyshev, O. N.; Minkova, A.; Popeko, A. G.; Sokol, E. A.

2009-10-01

477

Charge distribution in low energy fission of actinides  

NASA Astrophysics Data System (ADS)

Charge distribution studies were carried out for heavy mass fission products in the thermal neutron induced fission of 232U and 238Pu as well as in the spontaneous fission of 244Cm using off-line gamma ray spectrometry. The width parameter (sgrZ/sgrA), the most probable charge/mass (Zp/Ap) and the charge polarization (DgrZ) as a function of fragment mass were deduced. The slope of charge polarization with mass asymmetry (dgr(DgrZ)/dgrA'), average charge dispersion parameter (langsgrZrang) and proton odd-even effect (dgrp) were also obtained for these fissioning systems. The dgr(DgrZ)/dgrA' and langsgrZrang for the above three fissioning systems are determined for the first time. The dgrp value in 244Cm(SF) is also determined for the first time. These data along with the literature data for other even-Z fissioning systems such as 230Th*, 232Th*, 233Th*, 234U*, 236U*, 238U*, 239U*, 240Pu*, 241Pu*, 242Pu*, 245Cm*, 246Cm*, 250Cf* and 252Cf(SF) are discussed in terms of nuclear structure effect and dynamics of descent from saddle to the scission point. The role of excitation energy in low energy fission is also discussed by comparing the data of spontaneous, thermal and fast neutron induced fission of actinides.

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

2004-02-01